Performance measurement evaluation of the ecological component for inorganic arsenic compounds

Summary of the performance measurement evaluation of the ecological component for inorganic arsenic compounds

Executive summary

Performance measurement evaluations are a critical component of the overall chemicals management process, providing Canadians with information on the effectiveness of risk management actions for toxic substances. This report evaluates the performance of the risk management approach applied to inorganic arsenic compounds, identified as posing a risk to the environment.

The risk management of inorganic arsenic compounds was selected for performance measurement evaluation due to the substance meeting several readiness criteria outlined in the Performance Measurement Evaluation Strategy for Risk Management of Toxic Substances. These criteria include having risk management tools implemented for a sufficient duration to measure impact and the availability of key performance indicator data.

Inorganic arsenic compounds are present in the environment due to natural processes such as volcanic eruptions and weathering of rocks, as well as human activities like metal and mineral production, coal combustion, and the use of arsenic in pesticides. The 1993 Priority Substances List 1 (PSL1) assessment concluded that inorganic arsenic compounds were entering the environment in quantities or conditions harmful to the environment and potentially to human health. Consequently, these compounds were added to Schedule 1, which contains a list of substances concluded to be toxic under the Canadian Environmental Protection Act, 1999 (CEPA).

Adding a substance to Schedule 1 enables the Government of Canada to take action under CEPA to manage and mitigate the risks posed by the substance to humans and the environment. The approach to managing the risks of inorganic arsenic compounds included using existing measures to control releases of metals and other toxic substances, rather than developing specific risk management measures for arsenic. The Government's objectives are to reduce environmental concentrations to levels below those thought to cause adverse effects (the environmental objective) by preventing or reducing releases of inorganic arsenic compounds to the greatest extent feasible (the risk management objective). This report evaluates the effectiveness of the risk management measures taken to reduce the risks of inorganic arsenic compounds to the environment since 1993, assesses progress in meeting the environmental and risk management objectives, and evaluates Environment and Climate Change Canada's efforts to communicate environmental risks of inorganic arsenic compounds to the public.

Overall, the performance measurement evaluation found that progress has been made in achieving the   environmental and risk management objectives. Risk management measures have generally been effective at reducing releases from identified sources of concern. Industrial releases of arsenic have declined significantly since 1993, primarily due to reductions in the metal and mineral production sector. While this sector remains the largest source of arsenic releases to the environment, releases are expected to continue decreasing through the implementation of existing risk management measures. These measures should be updated as necessary to incorporate advances in best environmental practices and best available technologies, and to track the implementation rate of voluntary measures.

The significant increase in on-site disposals from the mining sector, due to arsenic contained in waste rock or mine tailings, reflects heightened activity or improved reporting practices. While current disposal practices are appropriate, the large amount of arsenic-containing mining waste is becoming a growing source of concern for future environmental management. This is particularly relevant when considering the long-term implications once facilities cease operations and the long list of abandoned mine sites that require remediation.

Reductions in industrial releases have led to declines in environmental concentrations of arsenic below levels of concern in many areas. However, certain regions in Canada, such as the Great Lakes, still exhibit arsenic levels above those considered to cause adverse effects. Continued monitoring of arsenic levels in the environment is essential for future evaluations. Enhancing monitoring efforts to fill gaps would be beneficial, potentially through collaboration with provinces and territories. Further research into the adverse effects of arsenic on wildlife and fish tissues is recommended to better evaluate environmental risk levels.

Few communication materials have been published on arsenic in the environment and associated risks. Ongoing work to improve awareness and public access to data, including user-friendly dashboards, will help Canadians understand the risks of toxic substances, their sources, and actions to prevent pollution.

In summary, human activities continue to release arsenic into the environment, with levels in some areas exceeding thresholds for adverse effects. Investigation is needed to determine if further reductions in releases are feasible and if new risk management actions are necessary for some sectors and sources. Continued collaboration with the United States and domestic partners is vital for managing releases beyond federal jurisdiction. A follow-up evaluation of the performance of risk management actions is recommended by 2035 to assess the implementation of any new measures, where warranted, and to collect additional performance measurement and environmental data. This data will be crucial for future evaluations and risk management efforts.

A performance measurement evaluation of the effectiveness of the Government of Canada's actions to address risks to human health from inorganic arsenic compounds will be conducted separately by Health Canada.

Glossary of terms

Back trajectory cluster analysis

Technique used to trace the path of a specific air mass in the atmosphere back to its source.

Benchmarks

Reference points or standards against which performance or achievements can be measured.

Biodilution

A phenomenon where certain substances become less concentrated as they move up through different levels of the food chain.

Biomagnification

A phenomenon where certain substances, such as pollutants or toxins, become more concentrated as they move up through different levels of the food chain.

Bioavailable arsenic

Arsenic that is available for absorption by living organisms from the environment, indicating its potential biological impact.

Biosolids

Refers to the primarily organic solid product of wastewater treatment that can be beneficially used.

BLIERs (Base Level Industrial Emissions Requirements)

BLIERs are emission requirements that are intended to apply to major industrial sectors or equipment types to ensure that significant industrial sources achieve a good base-level of performance across the country.

CCA (chromated copper arsenate)

A chemical compound used as a wood preservative, providing protection against rot, decay, and insect attack. However, due to its toxicity, it is no longer used in residential construction in Canada.

CCME (Canadian Council of Ministers of the Environment)

An intergovernmental forum responsible for coordinating environmental policies and programs in Canada.

CEPA (Canadian Environmental Protection Act, 1999)

Federal legislation that provides the framework for environmental protection and pollution prevention in Canada.

CMP (Chemicals Management Plan)

A Canadian government initiative designed to reduce the risks posed by chemicals to Canadians and their environment.

COA (Canada-Ontario Agreement)

An agreement that sets out specific responsibilities for the Canadian federal government and the Ontario provincial government in managing the environmental health of the Great Lakes.

COD (chemical oxygen demand)

A measure of the amount of oxygen required to oxidize soluble and particulate organic matter in water.

Coke

A type of carbon-rich solid that is derived from coal and is used as a fuel and in making steel.

Concentration

The amount of a substance in a given volume or mass of a medium (like air, water or soil). Usually expressed in units such as nanograms per cubic metre for air (ng/m3), micrograms per liter (µg/L) for water or micrograms per gram (µg/g) for solids.

Effluents

Refers to the total content of treated water discharged from a wastewater treatment system, including dissolved and particulate forms of chemical substances that remain after treatment and are released into the environment. May also refer to discharge of treated or untreated wastewater from an industrial facility.

Environmental code of practice

Voluntary guidelines issued to manage and mitigate environmental impacts from a particular source sector by recommending best practices and procedures. A risk management instrument available under CEPA.

Exceedance

Occurs when the concentration of a substance as measured in the environment, a plant or an animal is higher than the established environmental quality criteria or guidelines.

Facultative and aerated lagoons

Wastewater treatment systems using natural and assisted processes to decompose organic matter, with facultative lagoons relying partly on algae, and aerated ones using machinery to mix air and water.

Fluvial corridor

Areas adjacent to rivers and streams that are studied for their environmental characteristics and their role in maintaining ecological balance.

Fugitive air releases

Releases that escape capture from stacks, vents, or other confined air streams, due to equipment leaks, improper gas collection, or evaporation.

GLWQA (Great Lakes Water Quality Agreement)

An agreement between the United States and Canada intended to restore and protect the waters of the Great Lakes.

Guidelines

Recommended practices or limits that are not mandatory but serve to inform consistent and optimal approaches within specific fields. For example, guidelines under CEPA may recommend limits for the release of substances into the environment or best practices to avoid or minimize releases.

ICP-MS (inductively coupled plasma mass spectrometry)

An analytical technique used for elemental determinations, capable of detecting metals and several non-metals at very low concentrations.

Iron, steel, and ilmenite sector

Industries involved in the processing of iron ore, iron, steel, and ilmenite, each with specific environmental impacts and regulatory considerations.

MDMER (Metal and Diamond Mining Effluent Regulations)

Regulations governing the discharge of effluent from metal and diamond mines in Canada.

Mean concentration

The mean value is the average of a set of data. It is calculated by summing all the values and then dividing them by the number of observations. The mean concentration represents the typical value in the dataset, but it can be influenced by extreme values (outliers) more than the median.

Median concentration

The median value is the middle value in a set of data arranged in order of magnitude. If the dataset has an odd number of observations, it is the middle one; if even, it is the average of the two middle values. The median concentration represents a central point of data and is less affected by extreme values than the mean.

Mining

A set of industrial processes, including extraction operations, used to remove minerals and other geological materials from the earth. These processes may involve surface or underground techniques and serve as the foundation for producing metals and other critical resources.

NOx (nitrogen oxides)

Gases that are by-products of combustion processes and are major contributors to smog and acid rain.

NPRI (National Pollutant Release Inventory)

A Canadian government program that requires facilities to report on the quantities of pollutants they release to the environment.

Particulate phase concentrations

The concentration of a substance bound to particles in the water, as opposed to being dissolved in the water itself.

Performance agreement

A voluntary agreement between regulatory bodies and industries to meet specific performance standards in environmental management.

PME (performance measurement evaluation)

An evaluation process designed to assess the effectiveness of risk management actions in place for substances found to be toxic under CEPA.

PM (particulate matter)

Small particles or droplets in the air.

PM_2.5 (particulate matter with a diameter of less than 2.5 micrometres) and PM₁₀ (particulate matter with a diameter of less than 10 micrometres)

Fine particles can carry a variety of substances, including arsenic. Their small size allows them to penetrate deep into the lungs and even enter the bloodstream, posing greater health risks than larger particles like total particulate matter (TPM).

Pollution prevention planning notices

Official notices issued to facilities requiring them to prepare and implement plans to minimize pollution. A risk management instrument available under CEPA.

PPER (Pulp and Paper Effluent Regulations)

Canadian regulations that limit the release of effluents from pulp and paper mills to protect water quality.

PSL (Priority Substances List)

A historical list of substances in Canada that were identified as requiring assessment to determine their impact on the health of Canadians or their environment.

PSL1 (Priority Substances List 1)

The first set of substances assessed under CEPA, which included inorganic arsenic compounds.

Redox potential

or oxidation-reduction potential, measures a substance's tendency to gain or lose electrons. It is essential to understanding energy transfer in chemical reactions and biological systems.

Regulatory instruments

Tools used by governments or regulatory bodies to enforce actions intended to protect the environment.

Residence time

The average time a volume of water spends in a lake or other body of water. In the context of environmental science, it is significant because longer residence times can allow for more extensive chemical reactions or settling of particles.

Risk management objectives

Specific targets set to manage and mitigate risks associated with the use of toxic substances.

SO₂ (sulfur dioxide)

A gas produced by burning sulfur-containing fuels or smelting metal ores, which can cause respiratory problems and harm the environment.

Statistical evaluations

Methods used to analyze data to identify patterns, trends, and relationships among variables in environmental studies.

TEL (threshold effects level)

The upper limit of contaminant concentrations within a medium that pose no effects on the environment. Most commonly used with respect to concentrations in sediment.

TPM (total particulate matter)

The combined mass of all particulate matter emitted from a source, measured to assess air quality.

VOCs (volatile organic compounds)

Organic chemicals that evaporate at room temperature and react in the atmosphere to form ozone, contributing to air pollution.

Water and wastewater management

The practice of managing water resources and wastewater collection and treatment to minimize environmental impact.

Wastewater influents

Refers to the total content of untreated sewage from residential, commercial, institutional, and industrial sources, including dissolved and particulate forms of chemical substances, entering a wastewater treatment system for processing.

Water quality criteria

Standards set by regulatory agencies that specify the maximum permissible levels of pollutants in water to protect human health and aquatic life.

Whole water

Refers to the total content of a substance in both dissolved and particulate forms in a water sample. This is different from measurements that might only consider dissolved substances. Both dissolved and whole water measurements are used because particulate-bound contaminants can still pose environmental and health risks, affecting bioavailability, transport, and long-term deposition in ecosystems.

WSER (Wastewater Systems Effluent Regulations)

Canadian federal regulations governing the treatment and discharge of effluents from wastewater systems to protect water quality.

1. Introduction

The Government of Canada aims to mitigate the risks posed by substances identified as toxic to people in Canada and the environment under the Canadian Environmental Protection Act, 1999 (CEPA) through risk management initiatives within the Chemicals Management Plan. Performance measurement evaluations play a critical role in the overall chemicals management process by providing Canadians with insights into the effectiveness of risk management measures implemented for toxic substances. The approach for assessing the effectiveness of these measures and the achievement of objectives for toxic substances is detailed in the Performance Measurement Evaluation Strategy for Risk Management of Toxic Substances.

This report is intended to evaluate the effectiveness of risk management measures implemented by the Government of Canada for arsenic and its inorganic compounds, specifically to ascertain whether the established objectives for this substance have been met, whether additional actions are required to protect the environment, or whether the risk management measures have failed to achieve the intended outcomes. Health Canada will report separately on the results of its evaluation concerning the effectiveness of the Government of Canada’s actions to protect human health.

1.1 Sources, fate and effects of exposure

Arsenic is an element present in the earth’s crust and commonly found in fuel deposits such as coal, petroleum, and various geological formations. Arsenic mobilizes through air, soil, and water through natural processes such as volcanic eruptions and the weathering of rocks.

Human activities including mining and metal and mineral production, the use of arsenical pesticides, coal-fired power generation, and the disposal of domestic and industrial waste materials have significantly increased the amount of arsenic being released into the environment.

When released into the environment, arsenic can take different chemical forms which can be categorized into organic and inorganic arsenic compounds. Inorganic compounds, such as arsenite (As³⁺) and arsenate (As⁵⁺), are highly toxic to both the environment and humans.  Arsenic compounds containing carbon are known as organic compounds and include monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). These compounds are less toxic than inorganic arsenic compounds. The transformation from inorganic to organic arsenic involves natural processes, primarily microbial action in the environment, where microbes in soil and water methylate inorganic arsenic compounds, producing organic compounds like MMA and DMA. Due to the higher toxicity of inorganic arsenic and its greater availability in the environment, this report will primarily focus on inorganic arsenic compounds, as they were the basis for the original toxicity assessment.

Arsenic can be transported hundreds of kilometres in the atmosphere before being deposited onto land or into water bodies. In terrestrial environments, arsenic can accumulate in soil and enter the food chain through plant uptake. It can enter water sources through natural leaching from rocks and soils. In aquatic systems, arsenic can exist in dissolved forms or be associated with particulate matter in water. Arsenic can bind to particles and settle into sediments, where it may remain for extended periods. Under certain conditions, arsenic can be further remobilized, posing a long-term threat to aquatic ecosystems. Arsenic tends to accumulate in organisms, particularly in aquatic species and plants, which can lead to its persistence within food webs. Arsenic poses risks to ecosystems and human health due to its potential to accumulate in the organs and tissues of various species, such as fish and birds. Affected animals generally display intense abdominal pain, weak pulse, and dehydration among other symptoms.

1.2 Federal approach to risk management of inorganic arsenic compounds

Under the Canadian Environmental Protection Act, 1988 (CEPA 1988), both the Minister of Environment and the Minister of Health were tasked with developing a list of substances requiring timely assessment to determine if they are "toxic" or have the potential to become "toxic," as defined in Section 11 of the Act. This list was known as the Priority Substances List (PSL). CEPA 1988 mandated that substances on the PSL be evaluated within five years of their inclusion.

Arsenic was part of the first group of substances assessed under the Priority Substances List 1 (PSL1), which was established under CEPA 1988. The 1993 assessment concluded that inorganic arsenic compounds met the definition of "toxic" under CEPA as they posed a risk to both the environment and human health. As a result of this assessment, inorganic arsenic compounds were added to Schedule 1 of CEPA in 2000.

In response to toxic conclusions for inorganic arsenic compounds and other substances, the federal government established the Toxic Substances Management Policy (TSMP), which adopts a preventive and precautionary approach to manage substances entering the environment that could harm human health or the environment. This policy emerged from stakeholder consultations held from September 1994 to April 1995, following the release of the federal government's discussion paper "Towards a Toxic Substances Management Policy for Canada". Under the TSMP, track 2 life-cycle management was applied to arsenic and other similar substances, focusing on controlling and managing risks throughout their entire life cycle. This approach aligned with the TSMP’s broader goal of minimizing the release of toxic substances into the environment.

The policy offered decision-makers guidance and established a science-based management framework to ensure federal programs align with its objectives. It also served as the cornerstone of the federal government's stance on toxic substances management in discussions with provinces, territories, and international negotiations until the launch of the Chemicals Management Plan (CMP) in 2006.

The 2018 Fall Report of the Commissioner of the Environment and Sustainable Development to the Parliament of Canada assessed whether Environment and Climate Change Canada (ECCC) and Health Canada (HC) effectively enforced regulations under CEPA to control toxic substances. The report identified that enforcement priorities were not based on risks to health and the environment, recommendations from previous audits were not fully addressed, and public information on toxic substances was often unclear.

As a direct result of the report, the departments developed a Performance Measurement Evaluation (PME) Strategy, incorporated into the broader framework of the CMP. This strategy currently serves as a tool for evaluating the effectiveness of measures implemented to protect human health and the environment and determining the success of key objectives like minimizing health risks and reducing environmental impacts. This detailed analysis is essential for federal departments to make data-informed decisions, identify effective initiatives, and highlight areas needing improvement.

Moreover, the strategy emphasizes transparency and accountability. Through sharing evaluation results with the public, stakeholders, and other regulatory bodies, a clearer understanding of Canada's performance with respect to its chemical management efforts is achieved. This transparency ensures accountability and provides valuable information to the public and stakeholders, enabling them to participate more effectively in chemical management discussions and initiatives.

The approach to evaluating the effectiveness of risk management actions and whether objectives for toxic substances have been met is set out in the PME Strategy for Risk Management of Toxic Substances, titled: Strategic performance measurement: Evaluating the effectiveness of risk management actions on toxic substances in protecting Canadians and their environment.

1.3 The performance measurement evaluation report

Arsenic was chosen for the evaluation through a prioritization process. A key factor in its selection was its long-standing recognition as toxic to both the environment and human health under CEPA. As noted in the preceding section, inorganic arsenic compounds were added to Schedule 1 of the new Canadian Environmental Protection Act, 1999 (CEPA) in 2000 following a comprehensive risk assessment.

Since no formal risk management strategy was created to manage arsenic, for the purposes of this evaluation, the environmental objective for arsenic is to reduce Canadian anthropogenic releases of inorganic arsenic compounds so as not to exceed levels expected to cause adverse effects to the environment, taking into consideration natural background concentrations. The risk management objective for arsenic is to achieve the lowest level of anthropogenic releases of inorganic arsenic compounds that are technically and economically feasible, taking into consideration socioeconomic factors and focusing on actions taken since the 1993 assessment.

To guide this evaluation, several performance indicators have been identified:

Are environmental levels of arsenic a concern and/or do they exceed risk-based guidelines?

Trends in environmental concentrations of arsenic are closely monitored and analyzed to determine if arsenic is present or entering the environment at levels expected to cause adverse effects and how current conditions compare to levels observed prior to the introduction of risk management measures (baseline conditions).

Are there specific sites with elevated arsenic concentrations?

The evaluation examines differences in arsenic concentrations between ambient and impacted sites, focusing on various media such as water, soil, and air to provide insights into the spatial distribution and localized impacts of arsenic contamination and how this may have changed over time.

Considering the changes in arsenic levels over time, are additional protective actions required?

The evaluation assesses the implementation and effectiveness of relevant risk management actions, including whether they achieved their intended targets and objectives, and investigates whether these actions resulted in measurable reductions in releases of arsenic over time.

Are companies implementing best practices to their fullest extent?

Considering socioeconomic factors, the evaluation examines the extent to which best available technologies and best environmental practices are being implemented in sectors of concern, aiming to determine whether human-made releases of arsenic from these sectors can be further reduced.

Is current monitoring data sufficient to evaluate the risks and environmental outcomes?

The report evaluates the adequacy of information collected to support science-based decision-making in risk management for the ecological component of the PME for arsenic, providing insights into the availability and quality of data necessary for informed decision-making processes.

This report will provide recommendations regarding the need for consideration of new risk management actions, improved monitoring initiatives, enhancements in communication strategies, amendments to the environmental or risk management objectives, and the identification of new exposure sources. It will also determine the requirement for future evaluations.

2. Releases of arsenic from human activities

Arsenic is released into the environment as a byproduct from various human activities. These anthropogenic sources include the combustion of fossil fuels, disposal of waste materials, and both historical and ongoing mining as well as metal and mineral production activities. Additionally, production and use of products containing arsenic contribute to its release. Arsenic compounds have been used in wood preservatives like chromated copper arsenate (CCA), in certain pesticides and herbicides, and as an alloying agent to create or strengthen certain characteristics of other metals.

The PSL1 assessment identified these key sources, particularly highlighting metal and mineral production operations such as base metal and gold production, mining, coal-fired power plants, the use of arsenic-based pesticides and wood preservatives, and the disposal of domestic and industrial waste materials, as significant contributors to environmental contamination.

Environmental pollutants such as arsenic are tracked by federal government initiatives like the National Pollutant Release Inventory (NPRI). Although the federal Air Pollutant Emissions Inventory (APEI) records releases of several pollutants that affect air quality, including those contributing to smog and acid rain, as well as certain pollutants that are subject to international reporting, it does not include tracking of arsenic releases.

2.1 National Pollutant Release Inventory

The NPRI is Canada’s public inventory of releases, disposals, and transfers. It tracks over 320 pollutants from over 7,000 facilities across Canada. Reporting facilities include factories that manufacture a variety of goods, mines, oil and gas operations, power plants, and wastewater treatment systems (WWTSs). The NPRI data helps the government set environmental priorities and monitor environmental performance. The inventory collects data primarily through mandatory reporting from facilities that meet certain criteria. These criteria can include the type and quantity of pollutants released, the size of the facility, and the nature of its operations. NPRI data is published annually for all facilities that are required to report.

Figure 1: Map of arsenic releases reported in 2022

Data in the NPRI is organized by industrial sectors according to codes issued under the North American Industry Classification System (NAICS codes). It should be noted that a single facility reporting to the NPRI may have activities that fall under more than one industrial sector code. While facilities do have the ability to report more than one NAICS code to the NPRI, releases are not divided to each code, making it difficult to determine the relative amount of arsenic and other substances being released by each different industrial activity at a single facility.

For the purposes of this report, NPRI facilities were reviewed to identify their main activities, and then grouped into broader industrial sectors based on those activities. A detailed mapping of these groupings is provided in Table 11 of the annex.

The NPRI periodically updates its reporting requirements. These updates are pivotal in reflecting the evolving industrial practices and environmental priorities, significantly impacting the data collected and the management of pollutants. Notably, between 1993 and 2002, the NPRI's reporting requirements expanded to include a wider range of activities and facilities, bringing industries potentially emitting arsenic under closer observation, and improving the comprehensiveness of arsenic releases data. A major update occurred in 2002 when the reporting thresholds for arsenic and its compounds were adjusted to 50 kilograms with a 0.1% concentration criterion from 10-tonne and 1% concentration thresholds, tightening the reporting requirements and enhancing the tracking and management of arsenic releases.

In addition, the 2002 changes introduced new exemptions and redefined key terms, such as “facility” and “by-product,” which led to the exclusion of certain sources that were previously reportable. Some substances were reclassified resulting in gaps where emissions no longer met the revised thresholds. These definitional shifts, combined with sector-specific exemptions and transitional reporting inconsistencies, contributed to apparent decreases or disappearances in emissions data that reflect administrative changes rather than actual reductions in pollution.

The periodic updates to the data collection requirements of the NPRI, while essential for enhancing the accuracy and relevance of environmental data, introduce challenges in comparing data collected under different requirements over time. These changes can impact the consistency of data sets, making it difficult to directly compare trends across different reporting periods. To address this issue and ensure a coherent analysis, this report will primarily focus on data collected from the year 2002 onwards.

While this report is based on data obtained from the NPRI, it is important to note that the values presented here may differ slightly from those found in NPRI publications. This is because additional quality checks and contextual reviews were conducted for specific sectors to clarify facility activities, verify reported figures, and ensure consistency with the scope of this analysis. As a result, some adjustments were made to better align the data with the broader sector groupings and analytical objectives of this report.

2.1.1 Air releases

Arsenic air releases originate from several key industries and activities. The most significant is smelting operations within the metal and mineral production sector, particularly the production of non-ferrous metals like copper, lead, and zinc. These activities can emit arsenic into the atmosphere during the extraction and processing phases. Another major source is coal combustion, common in both power plants and industrial facilities. The coal used in these processes often contains trace amounts of arsenic, which becomes airborne when burned.

Previously, arsenic-containing pesticides contributed significantly to arsenic air releases. Although their usage has been limited due to regulatory controls, residual arsenic compounds in the soil where these pesticides were applied in the past can still volatilize into the air. Wood treatment processes, which once extensively used arsenic-based preservatives, also used to be a significant source of arsenic releases. These have been mostly phased out but were historically notable. Lastly, arsenic can be released into the air during the incineration of arsenic-containing waste, such as compostables and garbage from homes, businesses, schools, and other institutions. Regions with a high concentration of industries like mining, smelting, or coal-burning may experience elevated levels of arsenic in the air.

Using records from the NPRI, it is possible to analyze trends in the number of facilities that reported arsenic releases. Over the past two decades, the overall trend shows that despite an increase in the number of facilities reporting, air releases of arsenic have significantly decreased from a total of 163,581 kg in 2002 to a total of 21,547 kg in 2022, a decrease of more than 86%, indicating that environmental regulations and instruments and pollution control methods are effective.

The trend is largely driven by the reductions from the metal and mineral production sector, which is the primary contributor to arsenic releases, reducing its air releases from 160,960 kg in 2002 to 19,572 kg in 2022. Releases from this industry have shown a steady decline.

In 2022, arsenic releases from the electricity and combustion sector were considerably lower than in 2002, with a notable decrease in air releases over time. Levels remained stable from 2002 to 2011, around 1,300 kg annually, with a subsequent decline to less than 400 kg by 2022.

Releases to air from mining have slightly increased, from 242 kg in 2002 to just over 1,100 kg in 2022. 

Figure 2: Releases of arsenic to air by metal and mineral production facilities reporting to the NPRI from 2000 to 2022

Figure 3: Releases of arsenic to air by industry type (excluding metal and mineral production) and number of facilities reporting to the NPRI from 2000 to 2022 

2.1.2 Releases to water

Arsenic released into water bodies stems from a variety of industrial activities. Major contributors include mining, pulp and paper, and waste management operations. These industries can introduce arsenic into aquatic systems either directly or indirectly through WWTSs, thereby contaminating both surface and ground water.

Geographic factors play a role in arsenic water pollution as well. Regions with a high concentration of arsenic-intensive industries or areas with naturally occurring arsenic in the geological formations may show elevated levels of arsenic in local water bodies.

According to NPRI data, mining is the predominant source of arsenic releases to water, releasing a total of 187,785 kg over two decades. The releases peaked dramatically in 2005 with 40,935 kg and have generally trended downwards, with 1,660 kg emitted in 2022. The significant increase in water releases during the period of 2002 to 2008 was mainly attributed to one company. The releases don’t take into consideration the dam breach that occurred at Mount Polley Mine tailings in 2014 which released 259,050 kg of arsenic.

The second largest contributor is waste and municipal biosolids, mainly wastewater treatment facilities, which released a total of 61,061 kg of arsenic. The releases fluctuated over the years, reaching 3,571 kg in 2022. It is important to note that WWTSs do not generate arsenic; rather, the levels detected depend on the composition and origin of the incoming wastewater, commonly from industrial and domestic sources.

The pulp and paper industry has released a total of 56,523 kg of arsenic to water. The industry saw its highest water releases in 2004 at 3,758 kg and has managed a considerable reduction to 1,713 kg by 2022.

Figure 4: Releases of arsenic to water by industry type and number of facilities reporting to the NPRI from 2000 to 2022

Note: There was a large spike in arsenic releases to water (approximately 259 tonnes) in 2014, due to a tailings pond breach at the Mount Polley Mine. This spike has been removed from the graph since it represents an outlier data point and its removal better demonstrates ongoing sector trends for the remaining years shown in the chart.

Overall, releases to water have decreased from 12,176 kg in 2002 to 8,232 kg in 2022, a 32.3% reduction over two decades. It is important to note that the increase from mining releases to water from 2003 to 2008 was due to reporting from one facility; since 2006, this facility has changed to reporting their arsenic quantities as disposals to tailings (Figure 6) due to changes in regulations and reporting requirements.   In addition, the increase in the number of facilities reporting releases to water is due to the increase in mining production throughout the country.

2.1.3 Land releases

Note that releases to land from diffuse or non-point sources, such as the application of biosolids on agricultural land, are reported as on-site or off-site disposal via land application under the NPRI.

According to NPRI data, the pulp and paper sector is the largest source of releases to land releasing a total of 7,970 kg of arsenic, mainly from spills and other activities during operation such as deinking, adhesives, and other contaminants from recycled paper to produce clean pulp for making new paper products. This process generates sludge containing arsenic and other contaminants that can leach into soil and groundwater if not properly managed. This sector had relatively low releases initially, with an increase to 1,168 kg in 2007 before gradually decreasing to 202 kg by 2022.

Figure 5: Releases of arsenic to land by industry type and number of facilities reporting to the NPRI from 2000 to 2022

A significant drop in the reported arsenic releases to land from the electricity and combustion sector occurred after 2002 due to changes in NPRI reporting criteria, reclassifying some releases as disposals rather than direct releases (Figure 6).

For data consistency and to normalize the analysis, data reported as land release by the electricity sector prior to 2002 were assigned to on-site disposal.

2.1.4 Disposal, waste treatment and recycling

NPRI tracks releases of certain pollutants across Canada, including detailed data on disposal, waste treatment, and recycling activities. The inventory provides comprehensive information on the quantities of various substances, including arsenic. It also monitors how these substances are managed to prevent environmental contamination.

Arsenic on-site and off-site disposals are managed through several methods, each aimed at minimizing environmental and health risks. One common approach is stabilization and solidification, where arsenic is mixed with materials like lime or cement to transform it into less soluble forms, reducing the risk of leaching into groundwater. Another method used, primarily for hazardous waste, is secure landfilling, where arsenic waste is disposed of in specially designed landfills equipped with features like impermeable liners and leachate collection systems to prevent contamination of the surrounding environment. These methods are employed usually when there is hazardous waste present.

The mining industry is the primary contributor to arsenic disposal. Arsenic naturally occurs in many metal ores such as those of copper, lead, and gold, and is produced in significant quantities during their extraction and processing. This process leads to arsenic presence in the waste products or tailings. Arsenic disposals have significantly increased from under 10 million kg in 2005 to over 60 million kg in 2022, mainly driven by changes in the reporting requirements (starting with the 2006 data) as well as increases in demand and production, despite the number of facilities remaining relatively stable.

Figure 6: On and off-site disposals of arsenic by industry type and number of facilities reporting to the NPRI from 2000 to 2022

The treatment of arsenic-contaminated materials involves several advanced techniques aimed at removing or stabilizing arsenic to prevent environmental and health risks. Chemical precipitation is a widely used method where chemicals such as iron salts or lime are introduced to form insoluble arsenic compounds that can be easily separated from water. Adsorption employs materials like activated carbon or alumina to capture arsenic from liquids, effectively isolating it from water sources. Ion exchange involves resins that swap their ions for arsenic ions, cleansing the water as it passes through. Membrane filtration, including reverse osmosis, allows water to pass through a semi-permeable membrane that blocks arsenic, thus purifying the water. For solid wastes, vitrification transforms arsenic into a stable, glass-like material at high temperatures, which prevents leaching. Additionally, bioremediation utilizes microorganisms capable of metabolizing arsenic, converting it into less harmful forms.

Due to changes to the NPRI reporting requirements, quantities of substances in tailings from mining were partially captured by the off-site treatment category (Figure 7) before being reported as disposals beginning in 2006 (Figure 6).

Figure 7: Off-site treatment of arsenic by industry type and number of facilities reporting to the NPRI from 2000 to 2022

Secondary resource recovery or waste remediation, reported under the “recycling” category in the NPRI, involves the process of flotation, which separates arsenic waste from valuable minerals in industrial and mining byproducts. This method uses chemicals such as surfactants and modifiers to enhance the separation efficiency. The goal is to recover minerals like gold while safely disposing of arsenic, thereby reducing its environmental impact. This process not only helps in detoxifying arsenic containing waste but also supports the recycling of other materials.

There has been a slight increase in the number of facilities implementing remediation and recovery practices. Metal and mineral production has been the highest contributor with fluctuating amounts ranging from 300,000 to 900,000 kg.

Figure 8: Arsenic contained in materials sent for off-site secondary resource recovery or waste

2.1.5 Findings and recommendations

According to the NPRI, there is an overall downward trend in the total amount of arsenic released in Canada from 1993 to 2022. However, due to changes in data collection methods from the NPRI, it is challenging to determine the real impact prior to 2002, and that is why the focus is mostly on the period after that, 2002 and onwards.

Figure 9: Reported releases of arsenic into the air, land, and water bodies in Canada from 1993 to 2022 based on data from the NPRI

Nevertheless, the reduction of arsenic releases to environmental media are noticeable. The most noticeable change occurred in releases to the air, which have consistently decreased. Land releases remained low with occasional variations. Water releases have been slightly decreasing. A notable exception in the data is the spike in arsenic releases to water bodies in 2014, which is attributed to the Mount Polley mine tailings dam breach in British Columbia.

There has also been a sharp increase in arsenic disposals, mainly from the mining sector, despite a relatively stable number of reporting facilities. This suggests either increased industrial activity or improved reporting. The increase in disposals also indicates that more arsenic is being captured and managed rather than being released into the air, water, or land. Off-site treatment and recovery/remediation efforts have grown, reflecting better arsenic management. The data, therefore, reflects a general movement towards reducing arsenic pollution.

Figure 10: Reported releases of arsenic to all media per industry from 2000 to 2022 based on data from the NPRI

Overall electricity and combustion, mining, and metal and mineral production are the sectors with the highest decrease in arsenic as measured by the NPRI. However, mining and metal and mineral production are still the largest anthropogenic sources of arsenic, with releases to air being the most significant source of release to the environment.

It is recommended that release inventories continue to collect and report on industrial releases and improve data collection methods where possible.

2.2 Whales Initiative and the Pollutants Affecting Whales and their Prey Inventory Tool (PAWPIT)

As part of the Government of Canada’s Whales Initiative, ECCC took actions to reduce the threat of contaminants to endangered whales in Canada and their prey. ECCC developed an online inventory of pollutants affecting whales and their prey. The inventory tool (PAWPIT) shows estimates of pollutant releases by all identified sources within the habitats of Northern and Southern Resident Killer Whales, St Lawrence Estuary Belugas, and their primary prey. PAWPIT also displays estimated ambient contaminant loads in the Fraser and St Lawrence River Basins and indicates where environmental quality guidelines were exceeded.

PAWPIT uses publicly available environmental monitoring data collected and reported by various sources, including different levels of government (federal, provincial, regional, and municipal) as well as from the literature. Data gaps are filled by correlation and extrapolation of available data and results are reported as a range (low and high cases) due to the presence of non-detects.^{Footnote 1} While the database is geospatially allocated by source and by contaminant, releases are estimated based on available data to represent pollutant contributions per sector or type of activity. Although some of the areas of PAWPIT’s data collection overlap with data collected under the NPRI as reported by facilities, PAWPIT’s estimates for releases to water tend to be higher and the inventory captures releases of contaminants not included in the NPRI.

Based on a comparison between PAWPIT data covering the habitats of Northern and Southern Resident Killer Whales in British Columbia and NPRI data for arsenic releases in 2017, there are notable differences in specific sectors, particularly for water releases. The most significant discrepancy is observed in the total arsenic releases to water from various industrial sectors, landfill leachate, and surface water runoff from urban areas, with PAWPIT reporting 35,000 to 76,000 kg, whereas NPRI reports only 2,245 kg for the lower BC region covered by the PAWPIT analysis. This substantial difference suggests that NPRI methods and requirements for capturing releases may result in underestimating and underreporting of releases to water, indicating the need for continued environmental monitoring.

2.2.1 Landfill leachate

Under the Whales Initiative, municipal solid waste landfills were sampled across various provinces, including British Columbia (BC), Quebec (QC), and Nova Scotia (NS), and measured arsenic levels from 2019 to 2022. This data provides insights into both raw and treated landfill leachates, demonstrating initial contamination levels and the efficacy of treatment processes.

For instance, in BC, every sample of raw leachate tested positive for arsenic in dissolved metals, with concentrations ranging from 0.11 to 11.2 micrograms per liter (µg/L) and a median of 3.51 µg/L. Treatment processes, likely involving physical and chemical methods such as filtration and precipitation, reduce these concentrations slightly, as evidenced in the treated leachate, which ranged from 1.04 to 5.42 µg/L. Quebec showed more variability, with 77% detection of arsenic in raw leachate and concentrations up to 30.0 µg/L and a median of 4.96 µg/L in raw leachate, and a maximum of 21.8 µg/L and a median of 15.05 µg/L for treated leachate still showing potential exceedances of environmental safety thresholds. This is particularly relevant given that discharges to freshwater ecosystems are typically assessed against the Canadian Council of Ministers of the Environment (CCME) guideline of 5 µg/L for total arsenic.

Nova Scotia displayed the highest variability with arsenic levels in raw leachate detected up to 50.4 µg/L and a median of 10.1 µg/L. Treated samples indicated effective concentration reduction, though levels in some samples remained higher.

PAWPIT estimates pollutants from landfill leachate using available environmental monitoring data up to and including 2017. A notable difference with the NPRI is that PAWPIT reports a range of 5,000 to almost 36,000 kg of arsenic releases to water from landfill leachate, while NPRI does not report on these sources.

2.2.2 Findings and recommendations

The Whales Initiative data from municipal solid waste landfills in British Columbia, Quebec, and Nova Scotia from 2019 to 2022 reveals that arsenic is a common contaminant in landfill leachate, with varying effectiveness of current treatment processes across the provinces. While treatment methods have managed to reduce arsenic levels to some extent, concentrations in treated leachate still often exceed environmental safety thresholds, particularly in Quebec and Nova Scotia, requiring further studies to identify the causes and enhance treatment strategies accordingly.

PAWPIT has identified surface water runoff as a significant contributor of contaminants to freshwater and coastal water, estimating much higher releases of arsenic to water from nonpoint sources than the NPRI. PAWPIT's use of environmental monitoring and extrapolated data allows for a more comprehensive assessment, capturing releases from smaller or unreported sources that may otherwise go unnoticed which, along with NPRI’s reporting framework, can help better estimate total arsenic releases and improve accuracy. Potentially expanding PAWPIT’s modeling or approach to other regions of Canada could help provide a more comprehensive understanding of trends.

2.3 Wastewater monitoring program

ECCC’s wastewater monitoring program has been generating a large dataset on levels of chemical substances in wastewater influents, effluents, and biosolids since 2009, providing a comprehensive image of the chemical substance landscape within Canadian WWTSs. The objective of the datasets is to increase the understanding of the levels of chemical substances entering municipal wastewater and the subsequent release to the environment. This information is used to refine modeling predictions of environmental exposure and fate of chemical substances, establish baseline levels of substance concentrations and removals, contribute to departmental initiatives such as PAWPIT, and assess performance of risk management measures over time.

Arsenic concentrations were recently measured in samples of raw influent, final effluent, and treated biosolids collected from 27 WWTSs in 2018, 2019, and 2021. Arsenic concentrations were previously measured and reported in raw influent, final effluent, and treated biosolids collected from 25 WWTSs sampled between 2009 and 2012 in warm and cold seasons (Wong & Smyth 2016). The WWTSs participate in this program on the condition of anonymity, therefore no information on facility location is included.

Wastewater is not a primary source of arsenic. Instead, it collects arsenic from various origins including groundwater in arsenic-rich regions, industrial activities like mining, residues from past use of arsenic-based agrochemicals, residential sewage, and older household water wells. WWTSs can act as a pathway of arsenic to the environment via effluent and application of biosolids to agricultural fields.

2.3.1 Arsenic in wastewater influent

In the study of total arsenic in wastewater influent, two distinct periods were focused on: 2009 to 2012, and 2018 to 2021. For the period spanning 2009 to 2012, 191 influent samples were analyzed, with arsenic detected in 30% of these samples. The detected concentrations ranged from 0.12 µg/L to 3.00 µg/L with outliers as high as 7.06 µg/L. In contrast, the later period of 2018 to 2021 saw arsenic detected in all 132 influent samples. During this period, arsenic concentrations ranged from 0.38 µg/L to 3.83 µg/L. The differences in sample detection and concentrations over the two periods could potentially be attributed to changes in sampling techniques and the use of more sensitive analytical instruments.

Figure 11: Total arsenic concentration (µg/L) in raw influent between 2009 and 2021

Note: The line within the boxes indicates median, the box edges represent the interquartile range (IQR) which are 25th and 75th percentiles, and the whiskers below and above the boxes extend to the smallest and largest value, respectively, no further than 1.5 times the IQR. Dots indicate individual data points (coloured = detect, grey = non-detect). The grey line for 2018 to 2021 indicates the detection limit.

2.3.2 Arsenic in wastewater effluents

The concentration of arsenic in wastewater effluents was examined during the same time periods as influents: from 2009 to 2012 and from 2018 to 2021. Between 2009 and 2012, arsenic was found in 20% of 191 effluent samples, with detected concentrations varying from 0.12 to 4.39 µg/L (Figure 11). By contrast, in the later period of 2018 to 2021, arsenic was detected in all 132 samples, with concentrations ranging from 0.11 to 2.42 µg/L (Figure 11). Furthermore, another test was conducted to look at the presence of dissolved arsenic between 2018 and 2021. Here too, arsenic was found in 100% of samples, with a range from 0.10 to 2.33 µg/L (Figure 13).

Figure 12: Total arsenic concentrations (µg/L) in final effluent between 2009 and 2021

Note: The line within the boxes indicates median, the box edges represent the IQR, and the whiskers below and above the boxes extend to the smallest and largest value, respectively, no further than 1.5 times the IQR. Dots indicate individual data points (coloured = detect, grey = non-detect). The grey line for 2018 to 2021 indicates the detection limit.

Figure 13: Dissolved arsenic concentrations (µg/L) in final effluent between 2018 and 2021

Note: The line within the boxes indicates median, the box edges represent the IQR, and the whiskers below and above the boxes extend to the smallest and largest value, respectively, no further than 1.5 times the IQR. Dots indicate individual data points (coloured = detect). The grey line indicates the detection limit.

In comparing arsenic levels between the two periods, statistical tests revealed that the arsenic concentration in the more recent samples was significantly higher than in the older samples (Figure 12). Similar to influent data, these changes could be due to changes in sampling techniques and equipment.

Moreover, a separate test compared the total and dissolved arsenic concentrations for 2018 to 2021. While the difference was statistically significant, it was small (only 0.03 µg/L), indicating that arsenic is primarily found in its dissolved form in the effluent (Figure 14). Dissolved arsenic is more bioavailable, making it more easily absorbed by aquatic organisms and plants.

Figure 14: Total and dissolved arsenic concentrations (µg/L) in final effluent between 2018 and 2021

Note: The line within the boxes indicates median, the box edges represent the IQR, and the whiskers below and above the boxes extend to the smallest and largest value, respectively, no further than 1.5 times the IQR. Dots indicate individual data points (coloured = detect). The grey line indicates the detection limit.

Therefore, the study suggests an increased presence of arsenic in wastewater over time, mostly present in its dissolved form. Additional testing indicated that the change over time was not due to changes in wastewater quality over time. As discussed below, arsenic concentrations in biosolids did not change with time.

Figure 15: Total arsenic concentrations (µg/L) in raw influent (black) and final effluent (blue) in all WWTSs between 2009 and 2021

Note: The line within the boxes indicates median, the box edges represent the IQR, and the whiskers below and above the boxes extend to the smallest and largest value, respectively, no further than 1.5 times the IQR. Dots indicate individual data points (blue and black = detect, grey = non-detect). The grey line for 2018 to 2021 indicates the detection limit.

Possible explanations for the observed increases in wastewater influent and effluent (Figure 15) could include changes in laboratory procedures for wastewater samples, or more sensitive analytical instruments.

2.3.3 Arsenic removal from wastewater treatment systems

The effectiveness of removing arsenic from wastewater and partitioning it to solids before the water is discharged back into the environment varies depending on both the nature of the arsenic and the kind of treatment process used. To measure how well arsenic was removed, a formula was used that compares the arsenic levels before and after treatment. The results were expressed as a percentage.

The study found that on average, about 47% of arsenic was removed from the water phase during treatment. However, there was a wide range of effectiveness, with some facilities managing to remove as much as 98% of it. More advanced treatment systems generally did a better job at removing arsenic.

Some of the data even showed negative removal rates, meaning the arsenic levels apparently increased after treatment. These negative numbers might be due to issues with how the water flows through the treatment system (for example, recirculating load), variations in measurement techniques, or time delays between influent and effluent sampling. Specifically, treatment types like facultative and aerated lagoons, which hold water for longer periods, were more likely to show these negative removal rates.

Statistical tests showed that these differences in arsenic removal between treatment types were not just random; they were statistically significant. The most effective treatment type removed on average up to 67% of arsenic, while the least effective treatment type actually increased arsenic levels by 1%. The different types of treatments and their performance can be observed in Figure 16.

Therefore, the study indicates that arsenic removal is a complex issue that depends on several factors, including the type of treatment used. 

Figure 16: Removals of total arsenic during wastewater treatment by treatment types between 2009 and 2021

Note: type. FL = facultative lagoon, AL = aerated lagoon, PT = primary treatment, ST = secondary treatment, AT = advanced treatment. Note that an extreme outlier under ST (-584%) is not shown. The line within the boxes indicates median, the box edges represent the IQR, and the whiskers below and above the boxes extend to the smallest and largest value, respectively, no further than 1.5 times the IQR. Dots indicate individual data points (black = removals calculated using detects, grey = removals calculated where one value was the detection limit).

2.3.4 Arsenic in biosolids

In the period from 2009 to 2012, total arsenic was measured in 135 biosolids samples and was detected in every sample. The detected concentrations ranged from 0.05 milligrams per kilogram (mg/kg) to 12.2 mg/kg. A subsequent measurement period from 2018 to 2021 involved 101 biosolids samples, and once again, total arsenic was detected in every sample, this time ranging from 1 to 17 mg/kg. Statistical tests were employed to compare the arsenic concentrations between these two periods, revealing no significant differences. However, it is worth noting that the analytical methods used for the more recent samples were more rigorous, rendering the newer data more reliable.

An analysis was conducted to assess how different solids treatment methods impact the levels of arsenic in biosolids, as treated biosolids are often used for agricultural and landscaping purposes. The findings were significant, indicating that the type of treatment does affect arsenic concentrations. Specifically, aerobic treatments, which use oxygen in the process, resulted in biosolids with lower arsenic levels, around 3 mg/kg. In contrast, anaerobic treatments, which operate in the absence of oxygen, produced biosolids with higher arsenic levels, around 5 mg/kg. Typically, low-arsenic biosolids are suitable to be used in farms for crops; moderate levels can be used for landscaping or reclamation, and high levels are restricted to industrial sites or landfill covers where exposure is minimal.

Figure 17: Total arsenic concentrations (mg/kg dry weight) in treated biosolids between 2009 and 2021

Note: The line within the boxes indicates median, the box edges represent the IQR, and the whiskers below and above the boxes extend to the smallest and largest value, respectively, no further than 1.5 times the IQR.

2.3.5 Findings and recommendations

The study conducted between 2018 and 2021 has shed light on significant aspects concerning the presence and treatment of arsenic in wastewater. Notably, the research consistently detected arsenic in all influents, effluent, and biosolids samples, reaffirming its persistent existence within wastewater matrices. Furthermore, the efficacy of arsenic removal during the wastewater treatment process showed variability, with the extent of removal largely dependent on the specific treatment methods employed.

One important observation in this report is the higher arsenic concentrations found in samples collected between 2018 and 2021, in both influent and effluent, when compared to earlier samples obtained from 2009 to 2012. However, the arsenic levels in biosolids remained relatively constant over time. This apparent increase in arsenic concentrations in recent samples appears to be a result of advancements in sample preparation, digestion, and analytical methods, rather than a genuine escalation in arsenic levels within wastewater.

Considering these findings, it is recommended to continue periodic monitoring of arsenic in wastewater. Maintaining consistency in sampling, preparation, and analytical procedures is crucial, while also acknowledging the potential for ongoing evolution and enhancement of these techniques. It is important to recognize that wastewater treatment systems are not explicitly designed for arsenic removal. Therefore, any risk management strategies should primarily emphasize controlling arsenic at its upstream sources to mitigate its impact on the environment. It is recommended to complete further studies to identify the source of the variation of arsenic levels upstream.

2.4 Environmental effects monitoring

Some regulations require environmental effects monitoring (EEM) as a condition for the authorization to deposit effluent into waters frequented by fish. Environmental effects monitoring involves assessing whether effluents are having an effect on fish, fish habitat, and use of fish by humans. It may also involve investigating the cause of an effect and identifying solutions to eliminate it. Environmental effects monitoring supports the Government of Canada in assessing the performance of regulations for protecting the environment.

EEM encompasses various activities to ensure comprehensive environmental protection:

Effluent Characterization: Analyzing the chemical composition of effluents to detect harmful substances

Water Quality Monitoring: Regular testing of water bodies receiving effluents to ensure they meet quality standards

Sublethal Toxicity Testing: Assessing the effects of effluents on aquatic life over time without causing immediate death

Biological Monitoring: Examining the health of fish populations, benthic invertebrate communities, and analyzing fish tissues for contaminants

Cause Investigation: Determining the origins of observed environmental impacts

Solution Identification: Developing and implementing strategies to reduce or eliminate negative effects on the ecosystem

EEM is a requirement under two significant Fisheries Act regulations administered by ECCC:

Pulp and Paper Effluent Regulations (PPER): These regulations focus on the control of acute lethality rates, biochemical oxygen demand (BOD), and total suspended solids (TSS) in the effluent discharged from pulp and paper mills. Arsenic is not monitored under these regulations at the current time, although the proposed modernization of the regulations would include arsenic in the list of substances to be measured through effluent characterization and water quality monitoring.

Metal and Diamond Mining Effluent Regulations (MDMER): These regulations stipulate periodically monitoring and reporting of deleterious substances including arsenic, pH levels, and toxicity in the effluents from metal and diamond mining operations.

2.4.1 Arsenic compliance in metal and diamond mining effluent

The compliance indicator for arsenic measures the annual percentage of test results from metal and diamond mines that meet the authorized regulatory limits set by the MDMER. These regulations aim to protect aquatic environments and fish habitats by restricting the concentration of arsenic in mining effluent to a maximum monthly mean concentration of 0.10 milligrams per liter (mg/L) for new mines, and 0.30 mg/L for existing mines.

The compliance data is provided by owners and operators of metal and diamond mines to ECCC as required under the regulations. The compliance percentage is calculated by dividing the number of monthly mean results that meet the authorized limits by the total number of reported results.

Between 2003 and 2023, compliance rates for arsenic varied from 99.5% to 100%. This means that during this period, 99.5% to 100% of the test results for arsenic in mining effluent met regulatory limits with high adherence to environmental standards with minimal exceedances. Out of 151 mines subject to the Regulations, only 4 mines, 2.6% of the total, didn’t fully comply with reporting in 2023.

2.4.2 Findings and recommendations

Assessing the chemical composition of effluents, monitoring water quality, and evaluating the health of aquatic life, EEM helps identify potential impacts and their causes, guiding efforts to mitigate negative effects.

High compliance rates for arsenic in mining effluents (99.5% to 100% from 2003 to 2023) demonstrate adherence to regulatory standards. However, minor gaps remain in reporting, as evidenced by 4 facilities failing to submit reports in 2023. Continued monitoring and improved reporting are recommended to continue protecting aquatic environments and ensure long-term sustainability.

2.5 Conclusion

Current programs, such as the NPRI, provide valuable insights into arsenic releases from key industrial sectors, including mining, metal and mineral production, and energy production. Complementary tools like PAWPIT further capture data from additional sources, particularly highlighting releases to water that might otherwise go unnoticed. The Wastewater Monitoring Program also adds depth by assessing arsenic levels in influents, effluents, and biosolids, while EEM evaluates the impacts on aquatic ecosystems, ensuring compliance with regulatory standards.

Overall, the data shows that arsenic releases to the environment from industrial sources have declined significantly since 2002. However, there are still uncertainties with regards to quantities of arsenic released from smaller facilities that do not meet NPRI thresholds, and non-industrial sources including residential areas, agriculture, and small-scale commercial activities. Additional monitoring of surface water runoff and landfill leachate could help to improve information on arsenic releases from these source sectors and provide a more accurate insight of the potential environmental impact posed by arsenic. Expanding data collection from inventory programs like the Air Pollutant Emissions Inventory (APEI) to collect arsenic data, could fill gaps in air emissions data by including estimates for mobile, residential, agricultural, and natural sources that are not covered under the NPRI. Enhanced and more frequent localized monitoring, along with consistent reporting standards and advanced analytical techniques, could improve arsenic management and support more effective environmental protection strategies.

3. Arsenic in the environment

Arsenic enters the environment through a combination of natural processes and human activities. Naturally, arsenic is released from the weathering of rocks and volcanic eruptions, which can deposit arsenic into soils and water bodies. This natural occurrence is influenced significantly by local bedrock geology, leading to varying concentrations in different regions. Additionally, arsenic can be released through geothermal activities and forest fires. Natural concentrations of arsenic in soil range from 4 to 150 mg/kg, while levels in surface and groundwater vary from 0.001 to 0.005 mg/L.

As previously mentioned, human activities significantly elevate arsenic concentrations in various regions due to industrial and agricultural practices. Mining and smelting release arsenic into the air, water, and soil, while the use of arsenic-based pesticides and herbicides contaminates agricultural lands. The production of certain chemicals and wood preservation processes further contributed to environmental arsenic levels. Improper disposal of industrial waste and agricultural runoff may exacerbate this contamination. These anthropogenic sources, combined with natural geochemical processes, may result in increased arsenic levels, necessitating stringent monitoring and risk management measures to protect human health and the environment.

To address arsenic levels, benchmarks are established through rigorous scientific testing to determine safe concentrations of arsenic in the environment. These benchmarks serve as critical reference points, indicating acceptable levels of arsenic based on extensive research and environmental guidelines. By comparing real-world measurements to these standards, potential risks in different media can be assessed, guiding environmental monitoring and risk management actions to protect human health and ecological integrity.

Environmental monitoring programs are essential for tracking arsenic levels and other toxic substances in the environment. These programs systematically collect and analyze samples from air, water, sediments, fish, and wildlife. The data obtained helps identify contamination sources, assess progress against benchmarks, detect trends over time and, in the context of the PME report, helps assess progress in meeting the environmental objective for arsenic. For further details on the various monitoring programs discussed in this section, please refer to the Annex in section 9.

3.1 Air

Arsenic in the air originates from both natural sources, like volcanic eruptions and soil erosion, and human activities, such as mining, smelting, and fossil fuel combustion. Once released in the air, arsenic compounds are attached to particulate matter (PM) and become part of its chemical composition. Most arsenic is found in small particles known as PM_2.5, which can travel long distances from hundreds to thousands of kilometres before settling, affecting areas far from the source of emission. This deposition can harm plant and animal life, disrupt ecosystems, and contaminate water supplies.

Due to the effects of PM-bound arsenic on the environment and human health, measuring its concentrations has been part of several monitoring programs in Canada. Since 2004, the National Air Pollution Surveillance (NAPS) program has been measuring and reporting arsenic and other contaminants in PM_2.5 for urban and regional air across Canada. The Great Lakes Basin (GLB) Monitoring and Surveillance Program has assessed arsenic and other contaminants in PM₁₀ around the Great Lakes since 1995. Recently, arsenic measurements were made using passive air sampling techniques under the Assessing Toxicity of Urban Source Sectors in Air (ATOUSSA) study and the Global Atmospheric Passive Air Sampling (GAPS) Program that have expanded the capabilities of monitoring air quality on a global scale.

3.1.1 Benchmark levels of arsenic in air

Arsenic and its compounds are listed as toxic under CEPA and priority pollutant lists of the United States Environmental Protection Agency. As a result, and considering the already known effects of arsenic in air quality, some provinces in Canada such as Alberta, Quebec and Ontario have established air quality standards for arsenic in outdoor ambient air. These standards are based on the mean concentration of arsenic in particulate matter over specified durations, such as annually or over a 24-hour period.

For regulatory purposes, particles are classified by their diameter as PM_2.5 (fine) particles and PM₁₀.  Depending on the particle size and sources of emissions, PM contains a broad range of chemical species, including elemental and organic carbon compounds, oxides of silicon, aluminum, and iron, trace metals, sulfates, nitrates, and ammonium. Arsenic is mostly found in PM_2.5. Based on NAPS data collected at all sites in 2019 and 2023, between 85% and 98% of arsenic in particulate matter is found in the PM_2.5 fraction size.

3.1.2 Arsenic concentrations in air PM across Canada

The NAPS and GLB monitoring networks analyze arsenic in PM over a 24-hour period using PM_2.5 or PM₁₀ samplers that collect particles of a specific size and sampling volume.  Concentrations of arsenic in air PM measured by these networks are summarized in Table 2.  This table also includes arsenic concentrations in air PM that have been assessed through targeted studies, including the Oil Sands and Near-Road air quality study monitoring programs.

Note: BG = background site, MECP = Ontario Ministry of the Environment Conservation and Parks, a site located close to highway 401. The Global Atmospheric Passive Sampling - Mega Cites (GAPS-MC) site is located in downtown Toronto. ATOUSSA = Assessing Toxicity of Urban Source Sectors in Air

Figure 19: Average concentrations of arsenic as measured in the Canadian atmosphere under NAPS from 2004 to 2019 (from Table 2)

Note: For the classification of NAPS site types in each province, refer to Section 9.3, Table 6. Urban sites in this figure include general exposure population, point source influenced and traffic source influenced sites.

ECCC monitoring data from all monitoring networks or special studies indicated that the measured 24-hours concentrations of arsenic at each site, were at least 10 times lower than the ambient air quality criteria of 300 ng/m³ (24-hour averaging time) set by the Ontario Ministry of the Environment, Conservation and Parks. Also, the annual average arsenic concentrations did not exceed any of the annual ambient air quality guidelines, including the most stringent standard of 3 ng/m³ set by Quebec.

In addition to analyzing the total amount of arsenic in particulate matter, samples are tested to evaluate the amount of PM_2.5-arsenic present in the form of water-soluble compounds. This information contributes toward understanding long- and short-term negative environmental effects of particulate matter and sheds light on transportation of metallic substances through air. NAPS data show that the average solubility of arsenic in PM_2.5 at all sites varies from 65% to 78%. This means that a significant portion of arsenic released in the atmosphere as part of particulate matter is dissolved in precipitation like rain or snow which falls to the ground or enters surface water. The dissolved arsenic can then be taken up by plants and animals. Therefore, the release of arsenic to atmospheric particulate matter may have an important impact on the levels observed in soils, sediments, and surface waters, as well as aquatic life. 

Temporal trends from both NAPS and GLB programs show that arsenic concentrations are slowly decreasing across Canada. As shown in Figure 20, all three GLB sites show an initial increase from 1995 to the early 2000s, followed by a significant decline. This decline, as Li et al. (2020) suggest, might be attributed to various national and international control strategies. For example, the discontinuation of chromated arsenical-treated wood by the United States Environmental Protection Agency in 2003, voluntary industry actions in Canada, and the enhanced control efficiencies across industries have played a part. This is further supported by the reduction in the emission of PM₁₀, which plummeted from 37,000 tonnes in 1990 to 15,000 tonnes in 2017, as reported by ECCC. Similarly, trend analysis of NAPS monitoring data also shows overall arsenic concentrations have decreased by about 15% from 2004 to 2019 (Figure 21).

Figure 20:  Trend of the natural log of arsenic concentrations at three sites around the Great Lakes

Note: A green x represents measured values, the red line is the calculated trend, and the blue line is the seasonal trend. t_1/2 is the half-life or time required for the initial concentration of arsenic to decline to half.

Figure 21: Trend of the natural log of arsenic concentrations at all NAPS sites from 2004 to 2019  

Note: A green x represents measured values, the red line is the calculated annual trend, and the blue line is the seasonally smoothed trend. t_1/2 is the half-life or time required for the initial concentration of arsenic to decline to half. NAPS = National Air Pollution Surveillance

The seasonal variations of trace metal composition of atmospheric aerosols are controlled by several meteorological factors such as temperature, humidity and wind velocity and direction. Cold seasons are usually characterized by persistent thermal inversions, high precipitation and low wind velocities which favor the accumulation of human-made releases in PM_2.5 such as vehicular exhaust. Dry climate conditions during the warm seasons favour the formation and lift-up of dust particles, which is often the reason for elevated concentrations of crustal elements in the atmospheric aerosols during that time of the year (Celo et al., 2010). The seasonality trend of arsenic concentrations in PM_2.5 were dependent on the geographical location of the site. Higher concentrations of arsenic were recorded during warm seasons in Atlantic Canada, Quebec, and Ontario, whereas higher concentrations were recorded during cold seasons in Western Canada.

3.1.3 Sources of arsenic in PM

The potential sources of arsenic in particulate matter were investigated in several studies. For example, analysis of metal data from seven selected NAPS sites obtained between May 2004 and December 2006 identified industrial releases from metal-processing, building material manufacturing facilities, and mining, as potential sources of arsenic at urban sites (Celo et al.  2010).  Studies of the potential pollution sources in Southern Ontario (Sofowote et al.  2015, Yasine et al., 2024) concluded that the non-ferrous metal smelting industry and coking are the most probable source of arsenic in the region. Recent studies of PM_2.5 composition in dense traffic areas in Toronto and Vancouver, appear to indicate that traffic does not have a significant effect on arsenic concentrations in particulate matter; regional and local industry releases were the main contributors of this element (Dabek-Zlotorzynska et al.  2019, Celo et al.  2021).

Through the GLB program, a back trajectory cluster analysis method (Figure 22) was used to trace the air flow patterns to pinpoint likely sources of arsenic releases at the three Great Lakes sites (Burnt Island, Egbert, and Point Petre) (Li et al. 2020). Results from this analysis suggest that significant arsenic contributions are coming from the south, especially from the United States, impacting locations such as Egbert. Prominent sources were identified around Hamilton in Canada, as well as cross-border regions including parts of New York State, Pennsylvania, and the area where Ohio meets West Virginia. These three sites were further studied by Li et al. (2020). Their study made use of the enrichment factor (EF), a measure used to identify the influence of human activity on arsenic levels. An EF below 10 indicates that the arsenic is most likely from natural sources, while a value above 10 points indicates that it is caused by human activities. The median EF values observed at the three sites were between 120 and 160, indicating a significant human influence. This is in line with other metals like lead and zinc, though some metals like copper, cadmium, and selenium demonstrated even higher EF values.

Figure 22: Back trajectory cluster results show source areas where arsenic is coming from based on the concentrations of arsenic on particles in air at Burnt Island, Egbert, and Point Petre monitoring stations

A study of the sources of particulate matter components in the Alberta Oil Sands Region showed that arsenic is most likely emitted from a mixed combustion source, such as coke, or the process gases generated from oil and gas upgrading processes (Phillips-Smith et al.  2017). However, concentrations of arsenic measured at sites in the Alberta Oil Sands Region (0.02-0.19 ng/m³) were comparatively low (Mamun et al., 2021).

Wildfires were also an important contributor to the elevated concentration of arsenic in air particulate matter in the Alberta Oil Sands Region (Mamun et al., 2021). As can be seen in Figure 23, spikes in both PM_2.5 and arsenic concentrations were observed during intensive forest fires events in Alberta during the summer of 2016. Other studies have also confirmed that wildfires are a significant source of arsenic emissions in the air.

Figure 23:  Measured 24-hour concentrations of As in PM_2.5 in the Alberta Oil Sands Region during 2016 and NAPS sites measured during 2023  

3.1.4 Arsenic levels across the globe

Concentrations of arsenic in air PM measured in Canada are generally lower than levels reported in other countries (Celo et al. 2010). In 2019, the GAPS program measured the arsenic concentration at 51 sites worldwide. The recorded arsenic levels spanned from 0.0003 to 5.89 ng/m³ across most sites, with two outliers at 39.6 and 56.8 ng/m³ in Argentina and Barbados (Figure 24). The results indicated that Canadian levels were generally on the lower end.

Figure 24: Total arsenic concentration (ng/m³) as measured in global atmosphere using passive sampling under the GAPS program in 2019 (n = 1 at each site)

3.1.5 Findings and recommendations

Results from the NAPS, GLB, ATOUSSA and GAPS networks show that arsenic concentrations are higher near densely populated urban and industrial areas potentially influenced by metal production, mining, construction, vehicular traffic and contributions from the United States. 

Temporal trends reveal a significant decline in Canada since the early 2000s, likely due to control strategies like the discontinuation of chromated arsenic-treated wood and improved particulate matter controls across industries. Although arsenic concentrations have shown a decline in recent years, large releases of arsenic are observed during wildfire events. This will be important to track over coming years, with ongoing climate change and the increase of wildfires across Canada.

Arsenic concentrations in PM_2.5 at all measured sites across the country are below the most stringent provincial air quality standard. Overall, Canada's data reflect relatively low arsenic exposure levels compared to global averages, emphasizing the importance of ongoing monitoring and risk management actions to maintain and improve air quality, particularly in industrial and urban environments.

3.2 Aquatic environment

The federal government oversees networks that monitor water bodies throughout Canada, in collaboration with provincial, territorial, and U.S. partners. ECCC's role is to assess the impact of both human-made and natural contaminants on transboundary waters. These networks track a variety of pollutants, whether dissolved, attached to suspended particles, settled in sediments, or accumulated in aquatic flora and fauna. While some substances, like metals, have been monitored since the networks' inception, others have been incorporated over time to address specific concerns, such as those included in Canada’s Chemicals Management Plan.

The study, “Occurrence of Arsenic Contamination in Canada: Sources, Behavior, and Distribution” (Wang and Mulligan, 2006), provided an in-depth analysis of arsenic contamination across Canada. It explored both natural and anthropogenic sources, detailing the distribution of arsenic in air, soil, sediments, water, and biota. The study highlighted the environmental and health risks posed by arsenic exposure, examining its transport mechanisms, chemical behavior, and toxicity. Additionally, it discussed emerging remediation strategies, emphasizing the need for improved regulations, monitoring, and further research to mitigate arsenic contamination effectively. Aquatic conditions such as pH, redox potential, and dissolved oxygen influence arsenic behavior. Alkaline and low oxygen conditions, for example, enhance the release of arsenic from sediments due to the reduction of metal oxides that bind arsenic. Conversely, oxidizing conditions tend to stabilize arsenic in less toxic forms, reducing its mobility.

3.2.1 Benchmarks for arsenic levels in aquatic environments

In response to the need to protect aquatic ecosystems, the Canadian Council of Ministers of the Environment (CCME) established Canadian water quality guidelines (CWQG) which recommend the following maximum arsenic concentrations: 5.0 µg/L for fresh water and 12.5 µg/L for marine water (CCME 2001).

The CCME also established two key sediment quality guidelines: the Interim Sediment Quality Guideline (ISQG) and the Probable Effect Level (PEL) [CCME 1999]. These guidelines provide benchmarks for the protection of aquatic life from contaminants like arsenic in sediments, utilizing data from the Biological Effects Database for Sediments (BEDS), which includes extensive studies on arsenic concentrations and their observed biological impacts.

The ISQG represents a concentration below which adverse biological effects are expected to be rare. It is derived from the 15th percentile of concentrations associated with biological effects and the 50th percentile of concentrations with no observed effects. This conservative threshold aims to minimize risks to aquatic organisms. The PEL indicates a concentration above which adverse biological effects are more likely. It is calculated using the 50th percentile of concentrations associated with observed biological effects and the 85th percentile of concentrations with no effects. The PEL serves as a higher-risk threshold, identifying levels where impacts on aquatic life are more probable. For arsenic in freshwater sediments, the ISQG is set at 5.9 µg/g dry weight (dw), while the PEL is set at 17.0 µg/g dw (CCME 1999a). These guidelines help inform environmental management by defining contaminant levels that pose varying degrees of risk to the aquatic ecosystems. In aquatic environments, arsenic undergoes various chemical and microbiological processes. Its uptake by aquatic organisms is influenced by phosphorus levels in the water. Notably, arsenic does not biomagnify in freshwater food chains.

The Canadian Environmental Quality Guidelines also address arsenic interactions within soil environments, emphasizing their impact on plant health, particularly in irrigation and livestock watering contexts. For agricultural water, the guidelines recommend a maximum arsenic concentration of 100 µg/L for irrigation water to prevent soil accumulation that could harm plant growth, and 25 µg/L for livestock water to ensure the safety and health of animals, which may be more sensitive to arsenic exposure than plants (CCME 1999b).

3.2.2 Sediments

Under the CMP, the sediment monitoring program has been conducted on a regular basis since the mid-2000s on surface sediments mainly in the Great Lakes-St. Lawrence River basin with limited collections from the Atlantic Provinces and British Columbia between 2011 and 2014. The information provided here is based on analyses of total recoverable (TR) metals. This analysis method focuses on identifying metals in the environment that can be absorbed by organisms, termed as bioavailable metals. However, it is important to note that even minor changes in how this analysis is conducted can introduce some inaccuracies or biases in the findings. Therefore, these results should be interpreted with caution, especially considering that the sensitivity of these methods to detect metals like arsenic, known as method detection limits, can vary significantly across different sampling events. Table 3 presents arsenic results measured in the Canadian environment since 1968. The spatial distribution of arsenic in sediments in Canada is shown by region from 2008 to 2019 in Figure 25.

Detailed maps of arsenic concentrations in each region are shown in Figures 26 to 37 for the same time period. The variation in the colors used for these Figures is established in relation to the sediment quality criteria.

Table 3 and Figure 25 provide an overview of arsenic concentrations in different regions. Monitoring regions with average arsenic concentrations below the ISQG threshold include Lac des Deux Montagnes, Lac Saint-François, Lac Saint-Louis, Lac Saint-Pierre, Petit Bassin de la Prairie, Port de Québec, Port de Trois-Rivières, St. Lawrence Fluvial Section, Ontario Tributaries, Lake St. Clair, St. Clair River, and St. Mary’s River.

Regions with average levels between the ISQG and PEL include Atlantic, Port of Montreal, St. Lawrence Upper Estuary, Lake Erie, Detroit River, Georgian Bay, Lake Huron, Lake Superior, and Pacific.

Lake Ontario is the only area with average values exceeding the PEL limit. Other areas with outliers exceeding the PEL limit include Atlantic, Port of Montreal, Ontario Tributaries, Georgian Bay, Lake Huron, and Lake Superior.

Note: N/A = Not Available

Figure 25: Distribution of arsenic concentrations in sediments in the Canadian environment

3.2.2.1 Pacific Region

Surficial sediment samples and a sediment core were collected in southern British Columbia between 2011 and 2014 as part of the CMP program. The results for arsenic are presented in Figure 25 in relation to the other Canadian samples and in Figure 26 for their locations.

The median and mean values are 6.47 µg/g and 6.14 µg/g, respectively, with a maximum value of 10.1 µg/g observed at Frederick Lake. A sediment core was also collected from the Still Creek site. Concentrations of arsenic in the core show a gradual increase beginning in the early 1960s, likely attributed to industries located nearby in the Vancouver Industrial Park, suggesting that there are current active source(s) of arsenic.

Figure 26: Arsenic concentrations in sediments collected between 2011 and 2014 in Southern British Columbia

3.2.2.2 The Great Lakes

Results for arsenic in Great Lakes sediments are shown in Figure 27 for years of 1968 to 1973 and Figure 28 for years of 2013 to 2018. The median, mean, maximum, and standard deviation for each of the sampling campaigns and for each of the lakes are presented in Table 3 and Figure 25 for national comparison. Figures 29 to 31 show the arsenic profiles measured in the various sediment cores collected in the Great Lakes between 2007 and 2018.

Figure 27: Arsenic concentrations in Great Lakes surface sediments for the 1968 to 1973 sampling campaigns

Figure 28: Arsenic concentrations in the Great Lakes surface sediments for 2013 to 2018 sampling campaigns

Lake Superior, St. Mary’s River, Lake Huron, and Georgian Bay

Arsenic concentrations in Lake Superior, Lake Huron, and Georgian Bay are also seen in Figures 28 and 29 and concentrations were similar to the ones found in Lakes Erie and Ontario in the early 2000s (Gewurtz et al. 2008). Early work by Kemp et al. (1978) identified that since the late 1800s, all concentrations reflect some degree of human-made impact. Lake Superior background concentration for arsenic is 5.0 µg/g, Lake Huron is 4.7 µg/g, and Georgian Bay is 6.0 µg/g (Kemp, et al, 1978, Gewurtz et al 2008). Background values suggest a significant portion of arsenic found in the sediment can be explained through natural sources such as bedrock and surrounding soils. However, mining activities around the upper lakes, as well as aerial deposition from more distant sources, are also a source (Kemp, et al. 1978, Kerfoot et al. 1999). 

The mean value for Lake Superior using data collected during this time period was reported as 8.0 µg/g, with a maximum reported value of 20 µg/g, while Lake Huron had a mean reported value of 9.2 µg/g and maximum value of 63.4 µg/g (Gewurtz et al. 2008). Incorporating data from 2015 and 2016 into the dataset resulted in increased values for both lakes, with Lake Superior increasing to 12.4 µg/g and 42 µg/g respectively, and Lake Huron increasing to 14.1 µg/g and 77 µg/g. Georgian Bay had a mean of 11.5 µg/g and a maximum of 31.2 µg/g (Gewurtz et al. 2008), increasing to 19.4 µg/g and 60 µg/g, respectively. It should be noted that these represent significant increases when compared to the historical data from the period of 1968 to 1973. Further review should be conducted to ensure that historical values are directly comparable to more modern sampling and analytical techniques.

Arsenic concentrations in sediments have increased across all water bodies. Mean values in Lake Superior rose from 1.12 µg/g in 1973, to 12.4 µg/g in 2016; an order of magnitude increase. Lake Huron had a slightly lower historic mean arsenic concentration at 1.12 µg/g and matched the Lake Superior rate of increase to 14.12 µg/g in 2017. Georgian Bay had a higher initial mean concentration in 1973 at 5.23 µg/g, and showed a similar trend of increase to 19.38 µg/g in 2017. Arsenic concentrations are unavailable for the 1968 to 1973 time period for St. Mary’s River. The mean concentration was 4.73 µg/g, with a median of 3.2 µg/g for the river in 2017. With similar increases in both Lake Superior and Lake Huron, it could be surmised that St. Mary’s River followed the same increasing trend. Table 4 highlights the significant change between sampling time periods, in both the number of stations above the CCME ISQG and PEL, identified as “percent change”. These represent significant changes in concentration, even when compared to data from Gewurtz et al. (2008), suggesting the need for further study to determine a mechanism for ongoing contamination.

Note: N/A = not available

The profiles of sediment cores taken from Lakes Superior and Huron show different temporal variation between the two (Figure 29). Both Lake Superior cores show a significant peak in concentration, with the eastern site (LS-80) peak occurring just after the year 1700, and the western site (LS-169) occurring later, near the end of the 1700s. Both sites rapidly return to pre-peak levels, then show a steady increase in concentrations to the current timeframe. Both cores indicate similar concentrations at the surface, LS-80 at 13 µg/g and LS-169 at 14 µg/g, and are only slightly higher than the Lake Superior sediment mean concentration of 12.4 µg/g.

Lake Huron had two cores sampled, but station LH-100 has no available dating information. Unlike Lake Superior, the core at station LH-43 does not have a peak concentration in the 1700-1800 timeframe. Rather, it shows very little increase, remaining at a steady concentration slightly higher than the estimated background concentration for the lake as a whole of 4.7 µg/g (Gewurtz et al. 2008). However, LH-43 has a rapid increase in As concentration beginning around 2005, to a high value of 34 µg/g in the top-most slice (2015). While LH-100 has no dating information, the core depth is similar to that of LH-43. Unlike LH-43, however, LH-100 shows only a minor increase in arsenic concentration of 2 µg/g between the bottom-most slice at 6 µg/g, and the surface measurement. Additional work in Lake Huron is suggested in order to gain a better understanding of arsenic concentrations over time.

Figure 29: Arsenic concentrations measured in sediment cores collected from Lake Superior (2016) and Lake Huron (2017) (WQMS, unpublished)

Lake Erie, St. Clair River, Lake St. Clair, and Detroit River

Maps of the spatial distribution of arsenic concentrations in Lake Erie and the connecting channel between Lakes Huron and Erie are also shown in Figures 27 and 28. Lake Erie arsenic concentrations are highest on the south-west shore near Cleveland, historically an industrial and manufacturing center, and in the eastern basin. Average background concentrations of arsenic for Lake Erie were calculated to be 9 µg/g (Kemp et al. 1978, Gewurtz et al. 2008). Median arsenic concentrations for Lake Erie in 2014 were 12.9 µg/g, which are only slightly higher than values reported by Marvin et al. (2002) and Mudroch et al. (1988). However, average concentrations for the lake are significantly higher at 26.05 µg/g (Table 3). Unlike other metals identified by Marvin et al (2002), arsenic contamination appears to be increasing over time.

Examining three sediment cores from Lake Erie, the spatial trend shows arsenic decreasing in the western basin and increasing moving east. Station LE-970 in the western basin has the lowest arsenic concentrations of the three cores, the highest value being measured in the early 1980s of 6.52 µg/g. LE-970 shows a steady decrease in concentration until just after 2010, when arsenic concentrations begin to rise again to a surface measurement of 5.24 µg/g.  The station in the central basin, LE-880, shows a steady decline in arsenic concentrations from a peak in the mid-1960s of 18.2 µg/g, to concentrations in the surface sediment of 7.81 µg/g. The eastern basin station, LE-879, is similar to the central basin, except for the surface sediments which show a marked increase in arsenic concentrations to 27.2 µg/g. Given the sudden significant increase, additional sampling should be carried out to confirm this value.

Figure 30: Arsenic concentrations measured in sediment cores collected from Lake Erie in 2014 (WQMS, unpublished)

Concentrations of arsenic in the St. Clair River averaged 5.16 µg/g in 2014. Lake St. Clair was lower, averaging 3.1 µg/g, while the Detroit River average concentration was 7.6 µg/g. These values are significantly lower than those of the upper lakes, similar to concentrations identified by Gewurtz et al (2008). Concentrations in Lake St. Clair remained the same as those measured in 2001 (Gewurtz et al. 2007).

Lake Ontario

The south shore and major sedimentary basins of Lake Ontario were sampled in 2018. Complete data from Station 1034 is available, located in the central basin of Lake Ontario (Figure 31). However, Station LO-1004 is incomplete, as dating information is unavailable. Background arsenic concentrations for Lake Ontario were calculated to be less than 5 µg/g, while concentrations in the early 2000s at the 75th percentile were 29.5 µg/g (Gewurtz et al. 2007). Average surficial arsenic concentrations in the lake in samples collected in 2018 was 19.9 µg/g, and the maximum value was 38 µg/g. Examining the profile of LO-1034, it appears that arsenic reached a peak concentration in the 1980s, and since then has been slowly declining to a surface concentration in the core of 17 µg/g. However, LO-1004 shows a significantly different history. Arsenic concentrations at this station peaked near the bottom of the core, at 116 µg/g, suggesting this was much earlier in the core time-period. Concentrations slowly dropped for several periods, before increasing again to a value of 52 µg/g just below the surface and then dropping to 45 µg/g at the surface. Concentrations could be due to the station’s location at the mouth of the Niagara River, which has been a significant source of contamination for Lake Ontario.

Figure 31: Arsenic concentrations measured in a sediment core collected from Lake Ontario in 2018 (WQMS, unpublished)

3.2.2.3 St. Lawrence River

Results for arsenic in sediments of the St. Lawrence River are presented in Figures 32 to 36 for samples collected between 2008 and 2018. The river has been separated into several sectors to better illustrate the data. The average pre-industrial arsenic concentration is estimated at 6.0 µg/g for pre-1850 deposits in Lake Saint-François, 5 µg/g in Lake St. Louis, and 2 µg/g in Lake St. Pierre (Saulnier and Gagnon, 2006). The averages, maximums and standard deviations for each of the sampling campaigns and for each of the lakes are presented in Table 3 and Figure 25 for a national comparison.

The channel of the St. Lawrence River runs through Quaternary deposits, mainly in the postglacial clay deposited under the Champlain Sea. Less than 3% of the suspended PM carried by the river waters originates from Lake Ontario, 32% originates from tributaries and 65% from bed and shoreline erosion, mainly in the river corridor and river estuary (Rondeau et al., 2000). This suggests that contamination in river sediments is of local origin and has little connection to the Great Lakes.

Upper St. Lawrence River

The Upper St. Lawrence River region includes the territory between Cornwall and Montreal and the Lake des Deux-Montagnes formed by the confluence of the Ottawa and St. Lawrence River (Figure 32). Average arsenic concentrations in surface sediments were 2.97 µg/g in Lake Saint-François, 8.7 µg/g in Lake Saint-Louis and 5.5 µg/g in Lake des Deux-Montagnes, between 2008 and 2018 (Table 3 and Figure 25). In the same order of presentation, the maximum concentrations measured were 9.75 µg/g, 8.7 µg/g, and 5.5 µg/g, respectively. The number of samples containing concentrations exceeding the ISQG criterion (5.9 µg/g) were 10.4% in Lake Saint-François, 21.4% in Lake Saint-Louis and 22.7% in Lake des Deux-Montagnes. In Lake Saint-Louis, 9% of samples exceeded the PEL criterion (17.0 µg/g), while only one sample exceeded this level in Lake des Deux-Montagnes.

The highest arsenic concentration (125.6 µg/g) was observed in Lake Saint-Louis. This area is known to have been the site of a smelter that operated between 1940 and 1990 (Pelletier 2009, 2019). Concentrations measured elsewhere in these lakes appear to correspond to residual ambient levels from a heavy industrial past in the Upper St. Lawrence (EC and MDDEP, 2007). It should be noted that the northern portion of Lake Saint-Louis receives turbid water from the Ottawa River, which partially drains the intrusive rocks of the Canadian Shield that likely contain higher levels of arsenic.

Figure 32: Arsenic concentrations in St. Lawrence River surface sediments for 2008 to 2018, and the sampling location and profiles for two sediment cores

In 1985, arsenic concentrations in Lake Saint-Louis were 4.9 µg/g (Champoux and Sloterdijk, 1988), but by 2003, this had risen to 8.5 µg/g, and to 8.7 µg/g in 2015 (Pelletier, 2009/2019). This represents an increase of approximately 77.6% from 1985 to 2015. Sediment cores taken in Lake Saint-Louis vary over the period, with the location at C1A exhibiting more significant increases during the post-industrial period up to the turn of the 1900s. Concentrations at this location then decreased until the 1920s, before increasing again to previous peak levels between 4 and 5 µg/g. The core at location C3B had consistent low concentration below 2 µg/g until the beginning of the 1900s. Concentrations then fluctuated around 3.0 µg/g until 1994 (the top of the core).

Fluvial Corridor

The Fluvial Corridor is the sector of the river between the mouth of Lake Saint-Louis and the entrance to Lake Saint-Pierre. This sector is mainly characterized by currents exceeding 3 m/s at certain locations. Sediment sampling is particularly difficult here because of the lack of depositional zones, requiring samples to be collected near the shores of the many islands or the shoreline of the river itself (Figure 33). It should be noted that the Petit Bassin de La Prairie is the channel used by commercial navigation to bypass the Lachine Rapids near Montreal Island. The area between Contrecœur and the entrance to Lake Saint-Pierre is not illustrated because no samples could be taken there due to the strong currents.

Figure 33: Arsenic concentrations in the sediments of the Fluvial Corridor for the sampling campaigns from 1989 to 2014

Average arsenic concentration in Petit Bassin de La Prairie in 2014 was 5.5 µg/g, with a maximum of 7.22 µg/g . This is lower than the average of 8.7 µg/g in Lake Saint-Louis (previous section), from which water flows. Thirty-three percent of the Petit Bassin de La Prairie stations exceeded the ISQG, while no stations exceeded the PEL.

For the rest of the Fluvial Corridor, concentrations are generally below the ISQG criterion except for the Contrecœur sector (Figure 33). The maximum concentration in the Contrecœur sector reaches 150.0 µg/g in a small channel between the islands near the industrial zone, home to several industries including iron and steel facilities, a base metal refinery, and a fertilizer bulk blending plant. For the sites in this area, 51.6% exceed the ISQG, while 28% of the sites exceed the PEL.

Lake Saint-Pierre

Lake Saint-Pierre is the last fluvial lake before the St. Lawrence estuary. It has a shallow depth of water on each side of the navigation channel located in its center. The upstream part of the lake is made up of the Sorel-Berthier archipelago, embedded in the post-glacial clay of the Champlain Sea which significantly restricts the speed of the currents. Due to the low mixing of the different water masses in the river, water from the Ottawa River flows along the north shore of the lake, while river water originating from the Great Lakes tend to flow through the center of Lake Saint-Pierre (Pelletier, 2008 and 2018).

Figure 34: Arsenic concentrations in the sediments of Lake Saint Pierre for the sampling campaigns from 1989 to 2016

Elevated concentrations measured in the channels between the Sorel-Berthier Islands probably come from the upstream portion of the river, most likely from Lake Saint-Pierre. Average arsenic concentrations have dropped slightly from 2.2 µg/g in 2003 (Pelletier, 2008) to 1.9 µg/g in 2012 (Pelletier, 2018), as seen in Table 3. The maximum value, however, increased from 4.9 µg/g to 6.4 µg/g, possibly due to the continuing increase in the areas upstream. Only 2.5% (8 samples) exceed the ISQG criterion, and no samples exceed the PEL.

Fluvial Estuary

The fluvial estuary is the sector of the St. Lawrence River between the mouth of Lake Saint-Pierre (Trois-Rivières) and the eastern extremity of Île d'Orléans (Figures 34, 35). The fluvial estuary is subject to tidal effects, and the currents are relatively strong along its entire length. There are very few areas of sedimentation except along shores sheltered from the current or in harbour enclosures such as the Harbour of Trois-Rivières and the Harbour of Quebec City. The concentrations measured in the Trois-Rivières sector in 2016 were similar to those obtained in 1989 (G.D.G. Environnement Ltée, 1990) (Table 3). No samples exceeded the ISQG, although 5 samples were within 0.05 µg/g of the threshold (5.9 µg/g). In 1989, the Quebec City area showed some elevated arsenic concentrations, with a maximum value of 26 µg/g (Procéan Inc., 1990). During this time, 14.5% of samples exceeded the ISQG, but only 1% (3 samples) exceeded the PEL. By 2012, concentrations have dropped, with a maximum measurement of 11.4 µg/g, and only 6.8% of samples exceeding the ISQG; no samples exceeded the PEL.

Figure 35: Arsenic concentrations in the sediments of the fluvial estuary of the St. Lawrence River, for the sampling campaigns from 1989 to 2012

Upper Estuary and the Saguenay Fjord

Arsenic concentrations are presented in Figure 36 for the Upper Estuary and the Saguenay Fjord, collected in 2009 (Pelletier, unpublished). Pre-industrial arsenic concentrations for this area were determined to be 2 µg/g (Saulnier and Gagnon, 2009). Average concentrations in 2010 were 7.6 µg/g, with a maximum concentration of 28 µg/g recorded downstream of Tadoussac. More than half of the samples were over the ISQG (52.8%) and 7.5% were over PEL. Higher concentrations were located near Rivière-du-Loup, where the Chutes du Loup flows into the river, likely due to runoff from agriculture and minor industrial activities. Two locations downstream of the Saguenay Fjord, Tadoussac also presented high concentrations, likely due to higher mobilization of sediments due to local geology.

Figure 36: Arsenic concentrations in the sediments of the Upper Estuary and Saguenay Fjord in 2010

3.2.2.4 Atlantic Region

Surface sediment samples and a sediment core were collected in the Atlantic region between 2011 and 2014 as part of the CMP program in order to provide an initial status report for several substances. The results for arsenic are presented in Figure 25 in relation to the rest of Canada and in Figure 37 for their location with the names of the lakes and streams visited, including the profile of the sediment core taken from the St. John River (SJR-12) in New Brunswick.

The average concentration was 69.1 µg/g (Table 3), however, this value is highly influenced by three extreme values: Lake William with a concentration of 858.0 µg/g, and Lake Banook with concentrations of 394.0 µg/g and 128.0 µg/g. Excluding these three samples significantly reduces the average to 15.8 µg/g. However, 64% of the samples still exceed the PEL, while another 88% exceed the ISQG. The sediment core collected from the St. John River (SJR) shows relatively stable arsenic concentrations during the last half of the 20th century with an average concentration of 5.7 µg/g which is well below the regional average, and slightly below the ISQG.

Figure 37: Arsenic concentrations in the sediments of the Atlantic Region from 2011 to 2019, including a sediment core in the Saint John River

Lake Banook is located in the heart of the City of Dartmouth and does not receive industrial discharges or sewage. It is a major aquatic recreation site hosting several annual regional, national, and international paddling competitions. Despite significant urbanization in the last part of the 20th century, the water of this lake is relatively clean. However, it sometimes has algae blooms in the summer prohibiting swimming and the hills surrounding the lake are conducive to regular rainwater overflow (C. Garron and B. Lalonde, Personal communications). Lake William is located north of Halifax and Dartmouth, and water flows through the Shubenacadie Canal to Lake Charles and then south to Lake Micmac and Lake Banook. Nova Scotia has more than 360 abandoned gold mines, including the Montague Gold District, which operated in the vicinity of Lake William and Lake Charles between 1863 and 1940 (Clark et al. 2021). Average arsenic concentrations measured in tailings located at the Montague mine site were approximately 13,600 mg/kg, and as high as 41,300 mg/kg (Drage, 2015). It is highly likely that the three highest arsenic measurements, located in this area, are tied to the mine operation. Additional elevated arsenic concentrations through the area may also be due to historic metal mining, as well as long-range atmospheric deposition (Roberts et al. 2019).

3.2.3 Surface water – oceans, rivers, lakes & precipitation

Arsenic enters surface waters, including rivers, lakes, and streams, through both natural sources (like regional geology) and human activities, such as industrial discharges, mining, and agricultural runoff. Monitoring arsenic levels helps assess the effectiveness of pollution control measures and their impact on aquatic life, indicating whether environmental risks have been reduced. Decreasing arsenic levels signify progress towards achieving environmental objectives.

ECCC has been monitoring metals, including arsenic, in surface waters since 1986 under the Canada Water Act. The program monitors key water quality parameters, including physical-chemical attributes, nutrients, and metals. Arsenic monitoring is crucial for assessing long-term trends in water quality across Canada.

The monitoring of surface water quality in Canada is divided into three main categories based on environmental conditions and program priorities:

1. Inland Rivers and Streams: The long-term network includes 220 sites representing various land uses, transboundary waters, reference locations, urban sites, and high-risk areas for water quality impairment. These sites inform national water quality status and trends, as well as Canadian Environmental Sustainability Indicators (CESI) like the Water Quality Index (WQI). The CESI program classifies its core long-term monitoring sites according to the dominant land-use(s) within a site’s drainage area, which broadly captures the types of environmental pressures that a site may be experiencing. Classifications include remote/least impacted sites and land-uses such as agriculture, forestry, mining, oil sands, populated areas, as well as different combinations of these categories.
2. Connecting Channels of the Great Lakes: These large river-like channels connect the Great Lakes and are heavily influenced by upstream lake water quality. Monitoring focuses on comparing contaminant levels as water flows from one lake to the next, providing insight into toxic chemical inputs from industrialized shorelines, particularly along the Niagara and Detroit Rivers.
3. Open Waters of the Great Lakes: Due to the vast size and depth of the Great Lakes, water quality monitoring resembles oceanographic studies, conducted from research vessels in the spring and fall. As binational waters, monitoring activities are coordinated with the U.S. through the Great Lakes Water Quality Agreement (GLWQA).

In addition to long-term sites, short-term monitoring is conducted at numerous locations near point source releases like mining, power generation, and smelters. These shorter-term datasets are not included in long-term trend analyses due to comparability issues.

Figure 38: Long-term water quality monitoring sites

3.2.3.1 Spatial distribution and trends of arsenic concentrations in Canadian surface water and comparisons to Water Quality Guidelines

Arsenic concentrations in surface waters are summarized by drainage areas and Pearse regions. Drainage areas include five major ocean drainage basins: the Atlantic Ocean, Hudson Bay, Gulf of Mexico, Pacific Ocean, and Arctic Ocean. There are also 25 Pearse regions evaluated.

Figure 39: Median arsenic concentrations (µg/L) for each Pearse drainage region in Canada

Note: There are no data available for the Northern Ontario, Great Lakes, and Northern Quebec drainage regions.

From 2004 to 2020, arsenic concentrations ranged from <0.01 to 59.5 µg/L across Canada. The lowest median concentration was found in the Atlantic Ocean drainage area (0.27 µg/L), while the highest median concentration occurred in the Hudson Bay drainage area (1.27 µg/L). In general, arsenic concentrations are lower in the Pacific and Atlantic Ocean drainage areas, possibly owing to regional geology.

Figure 40: Boxplot of arsenic concentrations (µg/L) by ocean drainage regions

Note: In each box, the central line represents the median value while the upper and lower edges of the box represent the 75th and 25th percentiles respectively. Lines extending from the boxes to show the extent of values up to 1.5 times the interquartile range (range from the 25th to 75th percentiles) above and below the box. Dots show values that lie outside the range of the whiskers, commonly referred to as outliers.

Across the various analyses, sites within the Assiniboine-Red drainage region had the greatest concentrations of arsenic and exceedances of the guideline value from all Pearse regions evaluated. The median concentration of arsenic in the Assiniboine-Red drainage region is 4.96 µg/L and nearly surpasses the CCME guideline value of 5 µg/L. This region encompasses southern Saskatchewan and Manitoba and the major rivers in the region are the Qu’Appelle, Assiniboine, and Red rivers. The region encompasses approximately 190,000 km² and the majority of land is used for agricultural production (73.2%) while natural and semi-natural areas (23.7%) and built-up areas (3.1%) made up the remaining land-use categories (StatCan, 2016). Of the six sites included in this drainage region, five are CESI sites. Four of these are being influenced by agriculture with farmland covering more than 75% of their respective drainage areas, while the final site experiences a mix of agriculture and mining influences. Of the six sites, five exhibit no detectable trend in arsenic concentrations, while the final site (Assiniboine River at Hwy 8 bridge, SA05MD0002) had a decreasing trend in arsenic concentrations.

Since the total fraction of water quality samples includes suspended particles, values using the dissolved fraction were compared against the total fraction. In each of the sites, the concentration of arsenic in the dissolved fraction ranged from 80% to 95% of the concentration in the total fraction. Even when discounting suspended particles, the concentration of arsenic in this drainage region is much higher than those found in other regions. This is likely the result of a combination of industrial sites which are not captured by NPRI and agricultural sites in the area. Geology is not expected to have significant impact in this area.

Figure 41: Boxplot of arsenic concentrations (µg/L) by Pearse drainage regions, arranged by their median values

Note: The Pearse region names have been abbreviated as follows: Arctic Coast-Islands (AC), Assiniboine-Red (ASN), Churchill (CH), Columbia (COL), Fraser-Lower Mainland (FRA), Keewatin-Southern Baffin Island (KEE), Lower Mackenzie (MAC), Lower Saskatchewan-Nelson (LSK), Maritime Coastal (MAR), Missouri (MIS), Newfoundland-Labrador (NFL), North Saskatchewan (NSK), North Shore-Gaspé (GSP), Okanagan-Similkameen (OKA), Ottawa (OTT), Pacific Coastal (PAC), Peace-Athabasca (ATH), Saint John-St. Croix (SJC), South Saskatchewan (SSK), St. Lawrence (STL), Winnipeg (WPG), Yukon (YKN).

Classifications from the CESI program were used to group sites by land-use type. These can be found in the CESI Water Quality in Canadian Rivers report.

Figure 42: Boxplot of arsenic concentrations (µg/L) by combined CESI site classifications

Sites classified under agricultural land use showed the highest median arsenic concentrations (2.3 µg/L), whereas populated and mixed forestry/mining sites had lower medians (0.44 to 0.47 µg/L). Reference sites showed the lowest concentrations (0.09 µg/L).

Most sites showed stable or decreasing arsenic levels, with only a few sites displaying upward trends, mainly in populated and mixed forestry/mining categories.

The median arsenic concentrations range from 0.27 µg/L in the Atlantic Ocean drainage area to 1.27 µg/L in the Hudson Bay drainage area. The Assiniboine-Red drainage region has the highest median concentration of arsenic at 4.96 µg/L, while regions like Keewatin-Southern Baffin and North Shore-Gaspé have the lowest median concentrations. The median concentration of arsenic in the Assiniboine-Red drainage region is close to the CCME guideline value of 5 µg/L.

Land-use classifications impact arsenic concentrations, with agricultural areas showing significant influence, especially in regions like Assiniboine-Red where agriculture dominates land use. While most sites showed no detectable trend in arsenic concentrations, one site in the Assiniboine-Red drainage region showed a decreasing trend.

Agriculturally influenced sites exhibited the highest median arsenic concentration at 2.3 µg/L, suggesting a potential link between agricultural practices, such as the legacy use of arsenic-based pesticides, and elevated arsenic levels in surface water. This is particularly notable in the Assiniboine-Red drainage region, located within the Hudson Bay drainage area, which is known for its intensive agricultural activities. Despite this, the data also suggest that geographic and regional characteristics play a crucial role in arsenic distribution, as evidenced by the relatively modest arsenic concentrations in agricultural sites in Prince Edward Island, which contrasts with the higher levels observed in the prairie regions of Manitoba, Saskatchewan, and Alberta.

Moreover, the analysis identified a frequency of arsenic concentration exceedances of the CCME guideline for the protection of aquatic life, set at 5 µg/L for freshwater environments. The majority of sites showed fewer than 5% of samples exceeding this guideline, with agricultural sites being the notable exception, where more than 25% of samples exceeded the guideline values, driven primarily by sites within the Assiniboine-Red drainage region.

Trend analyses conducted on the CESI sites revealed mostly decreasing or stable arsenic concentrations over the 16-year monitoring period, with a small number of sites across various classifications showing increasing trends. These trends indicate a slow rate of change in arsenic concentrations, unlikely to result in significant environmental or health impacts in the near future. Nonetheless, these findings highlight the importance of continued monitoring of arsenic levels in surface waters to manage and mitigate potential risks to water quality and public health.

3.2.3.2 Trends of Arsenic Concentrations in Water in the Great Lakes Connecting Channels and Comparisons to Water Quality Guidelines

From 1980 to 2003, the concentrations of arsenic in water within the Niagara and St. Lawrence rivers ranged between <0.100 µg/L and 5.000 µg/L. The median value was 0.600 µg/L, and the average was 0.653 µg/L. However, from 2003 to 2019, arsenic concentrations in the connecting channels exhibited a wider range, between <0.010 µg/L and 9.490 µg/L. The median concentration increased to 0.880 µg/L, with an arithmetic mean of 0.914 µg/L. Over the period of 1978 to 2019, particulate phase concentrations varied from <0.001 µg/g to 30 µg/g, with median and arithmetic mean values of 10.180 µg/g and 10.47 µg/g, respectively. Notably, concentrations tended to increase downstream, from the upper connecting channel sites in the St. Clair River through the Niagara and into the St. Lawrence River. Furthermore, concentrations typically peaked at downstream sites where upstream/downstream monitoring occurred, such as in St. Clair and Niagara, indicating the presence of inputs along these channel lengths. Lower values observed at Wolfe Island may be attributed to the longer residence time of Lake Ontario (6 years compared to 2.6 years for Lake Erie) and the settling of particle-bound arsenic to the lake bottom.

Within the reporting framework of the Niagara River Toxics Management Plan (NRTMP), ECCC assesses water quality parameters against the strictest criteria available to the Four Party agencies (ECCC, Ontario Ministry of the Environment, Conservation and Parks, United States Environmental Protection Agency, and New York State Department of Environmental Conservation). For arsenic, the NRTMP adopts the water quality criteria of 5.00 µg/L from the 1994 Ontario Provincial Water Quality Objectives, which is also the current CCME long-term Water Quality Guideline for the Protection of Aquatic Life. Applying this criterion to the 2003 to 2019 whole water dataset from the connecting channels identifies two exceedances: one at Niagara-on-the-Lake (7.94 µg/L in 2016) and another at Wolfe Island (9.49 µg/L in 2013). Before the analytical method change in 2003, these guidelines were not exceeded in water at the connecting channel sites, except for a measurement of 5.00 µg/L at Niagara-on-the-Lake in December 1983.

Comparing the particulate phase data against sediment guidelines developed by a workgroup of the St. Lawrence Action Plan (EC and MDDEP, 2007) shows exceedances of the ISQG in 200 samples at Point Edward (93% of the 214 samples taken between 2003 and 2019), 212 samples at Port Lambton (96% of the 220 samples between 2003 and 2019), 235 samples at Wolfe Island (91% of the 258 samples between 1988 and 2019), 874 samples at Fort Erie (99% of the 884 samples between 1983 and 2019), and 1045 samples at Niagara-on-the-Lake (99.9% of the 1046 samples between 1980 and 2019). Application of the sediment guidelines’ Occasional Effect Level (OEL, 7.6 µg/g) reduces these numbers to 152 exceedances at Point Edward (71% of all samples), 175 exceedances at Port Lambton (80% of all samples), 758 exceedances at Fort Erie (86% of all samples), 195 exceedances at Wolfe Island (76% of all samples), and 82 exceedances at Niagara-on-the-Lake (98% of all samples). Application of the CCME PEL (17 µg/g) identifies 19 exceedances at Niagara-on-the-Lake, 2 exceedances at Fort Erie, and 1 exceedance at each of Point Edward, Port Lambton and Wolfe Island.

With the exception of particulate samples at Niagara-on-the-Lake and the water dataset prior to 2003, the analysis of long-term data in arsenic concentrations indicates downward trends for ECCC monitoring sites in the Great Lakes connecting channels. Between 1980 to 2003, trends in water concentrations at Fort Erie, Niagara-on-the-Lake, and Wolfe Island do show increases; however, the increases are virtually negligible. From 2003 to 2019, water arsenic concentrations appear to be declining by approximately 0.94% per year at Point Edward, 0.91% per year at both Port Lambton and Fort Erie, 0.07% at Niagara-on-the-Lake, and 1.1% at Wolfe Island. It should be pointed out that the adjusted p value of 0.909 at Niagara-on-the-Lake suggests that the result is likely by chance and does not provide sufficient evidence to support the presence of the trend at this site. Downward trends also appear to be present in particulate phase arsenic. Particulate phase concentrations declined by approximately 1.85% per year at Point Edward, 2.54% per year at Port Lambton, and 0.38% per year at Wolfe Island. Niagara River concentrations show a decrease at Fort Erie (0.09% per year) and an increase at Niagara-on-the Lake (0.14% per year); however, the adjusted p values of 0.267 and 0.082, respectively, suggest that there is less evidence to support the presence of these trends.

Figure 43: Sampling locations for the connecting channels

Analysis of arsenic concentrations in whole water samples from the connecting channels reveals a notable range of concentrations over the years, with a gradual increase in the median concentration observed from the period of 1980 to 2003 as compared to the period 2003 to 2019. Specifically, arsenic concentrations ranged from less than 0.100 µg/L to 5.000 µg/L in the earlier period, with median values rising from 0.600 µg/L to 0.880 µg/L in the latter period.

Two exceedances of the Ontario Provincial Water Quality Objectives and the CCME guideline for arsenic, set at 5.00 µg/L for the protection of aquatic life, were recorded: one at Niagara-on-the-Lake and another at Wolfe Island.

Particulate phase arsenic concentrations, which provide another perspective on arsenic pollution, showed that concentrations tend to increase downstream. This pattern suggests the presence of arsenic inputs along the length of these connecting channels, with higher concentrations observed in areas with upstream/downstream monitoring setups, such as in St. Clair and Niagara. The comparison of particulate phase data against sediment guidelines developed by the St. Lawrence Action Plan further underscores the prevalence of arsenic, with numerous exceedances of both the ISQG and OEL recorded across multiple sites.

Despite these concerns, the long-term trend analysis of arsenic concentrations in both whole water and particulate phases indicates generally downward trends at most ECCC monitoring sites in the Great Lakes connecting channels. This suggests that efforts to control arsenic pollution are having a positive impact, though the pace of improvement varies across different sites. The decline in particulate phase arsenic concentrations, in particular, points to a gradual reduction in arsenic levels within the ecosystem.

3.2.3.3 Spatial and temporal trends of arsenic concentrations in the Great Lakes and comparisons to Water Quality Guidelines

Flowing waters in tributaries and connecting channels within transboundary watersheds are known as "lentic" systems. These environments tend to have higher concentrations of contaminants due to the constant flow of water. Great Lakes waters are known as "lotic" systems, where the water is still and sediments settle, resulting in lower contaminant levels.

The Laurentian Great Lakes are transboundary (US-Canada) waters that comprise an important aquatic system, holding approximately 20% of the global freshwater supply. Protection, conservation and restoration of the Great Lakes environment is a priority for both the United States and Canada. Arsenic is measured with other parameters of concern in Great Lakes waters in support of the binational Great Lakes Water Quality Agreement. It is included among a suite of total metals that is monitored as part of the Great Lakes Surveillance Program (GLSP), which is ECCC’s ship-based, long-term water quality monitoring program on the Great Lakes. Spatial patterns in water quality can be determined using the network of the GLSP. Samples are taken from both nearshore and offshore environments, in both Canadian and US waters with the exception of the 2019 campaign in Lake Superior in which only Canadian waters were sampled. Using offshore stations alone, where sites are removed from variability due to watershed sources, temporal trends can be detected that may not be evident in tributaries and nearshore waters. Monitoring for contaminants in the Great Lakes offshore is therefore a powerful method for detecting trends over time in the aquatic environment.

Figure 44: Spatial distribution of arsenic in Great Lakes surface waters from 2015 to 2019

A statistical analysis of temporal trends is conducted using offshore data only in order to maximize the probability of detecting trends, should they exist. The definition of offshore varies by Great Lake; for Lake Superior, these are stations with a total water depth of 150 m or greater; for Lake Huron and Georgian Bay 50 m or greater; for Lake Ontario 100 m or greater. For Lake Erie, the data are divided instead by basin (west, central, and east). The trend data are shown in Figure 45. There is evidence of a decline only in Lake Superior over the time considered here (2003 to 2019). This may be due to reductions in the levels of arsenic in precipitation. Due to its very large surface area relative to its watershed, atmospheric inputs are most significant for Lake Superior. The interpretation here is that arsenic declines in precipitation are reflected in the lake water trend for Lake Superior, but in the other lakes this overarching basin-wide declining trend in precipitation is masked by the influence of other sources. The Great Lakes are known to respond very slowly to changes in loadings, and the downstream Great Lakes will respond both to in-basin (watershed) sources as well as inputs from the upstream Great Lakes. The lakes are therefore responding to both contemporary and historic adjustments to inputs, exports, and transport.

Figure 45: Arsenic concentrations in the Great Lakes, 2003 to 2019 (ug/L)

Note: Box and whisker plots show the distribution of arsenic concentrations in the spring of each sample year. With the exception of Lake Erie, only offshore waters are shown. These data best illustrate long-term trends, away from the influence of nearshore sources. A temporal trend (decreasing) is only observed for arsenic in Lake Superior (solid line).

Overall, the data from 2003 to 2019 shows that arsenic concentrations in the Great Lakes have remained below the CCME long-term water quality guideline for the protection of aquatic life, which is set at 5 µg/L. Notably, the highest concentrations of arsenic were observed in Lake Ontario, with a mean concentration of 0.846 µg/L, followed by Lake Erie, Lake Huron, Lake Superior, and Georgian Bay, in descending order of concentration levels.

A detailed statistical analysis of temporal trends in offshore waters highlighted a significant decline in arsenic concentrations only in Lake Superior during the period considered. This decline is attributed to reductions in arsenic levels in precipitation, a significant source of arsenic for Lake Superior due to its large surface area relative to its watershed. In contrast, no significant changes were observed in the arsenic concentrations of Lake Huron, Georgian Bay, and Lake Ontario, and while variations were noted in the different basins of Lake Erie, they did not constitute a significant trend.

3.2.4 Biota – Fish Contaminants Monitoring Program (FCMP)

The analysis of arsenic concentrations in fish across the Great Lakes and elsewhere in Canada can yield valuable insights into the complex dynamics of arsenic exposure in aquatic ecosystems. It is evident that arsenic concentrations vary significantly among fish species, and these variations cannot be reliably predicted solely by the level of fish species in the food chain. Instead, bioaccumulation of arsenic in fish species appears to be influenced by factors such as dietary sources of arsenic and the capacity of fish to regulate internal arsenic levels. There is no compelling evidence supporting the biomagnification of arsenic within the fish food web; instead, biodilution appears to be the prevailing trend.

In some instances, factors like body size, diet, and foraging habitat may offer useful insights into explaining the variability of arsenic concentrations in fish at specific sites. Notably, the highest concentrations of arsenic were observed in fish from the Lower Great Lakes and St. Lawrence River regions. Additionally, an intriguing observation is the apparent increase in arsenic concentrations in lake trout from the Lower Great Lakes, particularly Lake Ontario, since the mid-1980s, while concentrations in certain prey fish, such as rainbow smelt, have declined. Importantly, less than 1% of fish displayed arsenic body burdens associated with negative impacts on fish health, and an even smaller fraction had whole-body arsenic concentrations exceeding human consumption guidelines (3.5 mg/kg fresh weight). Overall, there is limited evidence to suggest significant adverse effects of arsenic on fish populations at representative sites within the national monitoring network.

From an ecological perspective, comprehending the factors that drive arsenic accumulation in fish is of paramount importance. This understanding can inform mitigation strategies, especially in regions with established anthropogenic sources of arsenic, such as mining activities. Furthermore, the observed interspecies differences in arsenic concentrations underscore the importance for risk assessments to consider data from a range of species.

Regarding public health concerns, the study suggests that the risk associated with consuming fish containing elevated arsenic levels is minimal. Nonetheless, vigilance remains crucial, particularly in areas where fish consistently exhibit higher arsenic concentrations.

Additional details on the fish data are available in Table 7 of section 9.6 in the Annex of this report. 

3.2.4.1 Impacts of arsenic on fish

Chronic arsenic exposure can affect fish growth and reproduction, reducing egg production due to potential endocrine-disrupting effects (Davey et al., 2007). Studies have shown reductions in growth and survival in fish exposed to arsenic at specific body burdens (Gilderhus, 1966; Tsai and Liao, 2006). McIntyre and Linton (2012) concluded that chronic arsenic exposure impacts occur when whole body fish tissue arsenic concentrations reach 2 to 5 mg/kg wet weight. However, only three out of over 1900 fish measured had concentrations within this range.

Several factors influence arsenic toxicity and bioavailability. The type of arsenic is crucial, with inorganic forms being more toxic than organic ones (Kumari et al., 2017; McIntyre and Linton, 2012). The oxidation state also matters, and physical water quality parameters like hardness, pH, and dissolved organic carbon (DOC) can impact arsenic toxicity depending on its form. Salinity and temperature can influence toxicity, with arsenic (V), also known as arsenate, being more toxic to trout at colder temperatures (McGeachy and Dixon, 1989).

Fish are dietary items for humans and wildlife. The Canadian human health guideline for arsenic consumption in fish tissues is 3.5 mg/kg wet weight. However, as walleye are often consumed by humans, this poses some risk. Yet the proportion of inorganic arsenic in walleye is likely lower than in lower-level fish species, reducing the risk to human health. Fish convert inorganic arsenic to organic forms, and studies suggest that the risk of arsenic exposure to the public from fish consumption is low, even in areas with known arsenic contamination (Tanamal et al., 2021).

3.2.4.2 Interspecies differences

Significant differences in arsenic levels were seen among different species of fish living at the same site (Figure 46), but no clear link between their positions in the food web and arsenic levels was found. For instance, in Lake Ontario's Niagara Basin, top predator lake trout (trophic level 4) had significantly higher arsenic levels than prey fish (trophic level 3). However, in Lake Edouard, QC, omnivorous shiner species (trophic level 3) had arsenic levels comparable to lake trout, while insect-eating brook trout (trophic level 3) had notably lower arsenic levels. Unlike many contaminants that undergo biomagnification, that is toxin concentrations increase as one moves up the food chain, arsenic undergoes a process known as biodilution, especially in its inorganic form, leading to higher concentrations in lower food web organisms like plankton and algae as compared to fish.

Analysis of lake trout and smelt from the Great Lakes showed significant differences in arsenic concentrations. Arsenic concentrations were generally higher in lake trout, but differences were inconsistent across locations. Although lake trout exhibited a broader variability in arsenic concentrations, sites with high arsenic levels in smelt also tended to have elevated levels in lake trout, suggesting that lake trout can still effectively indicate arsenic pollution. These species-specific differences are likely due to different fish dietary habits and arsenic processing efficiency.

A fish species' dietary niche plays a crucial role in arsenic accumulation, and environmental factors and dietary preferences influence arsenic accumulation in fish across regions. Fish feeding in open waters, or the pelagic zone, tend to accumulate more arsenic than those closer to shore, in the littoral zone. Fish that eat plankton, like alewives, accumulate more arsenic than insect-eating or fish-eating counterparts, likely due to their high consumption of algae, which is a significant arsenic source.

Figure 46: Comparison of mean concentrations of whole-body arsenic (As) burdens in multiple species of fish from the same site

3.2.4.3 Spatial and temporal trends

Arsenic concentrations in top predator fish from various sites are shown in Figure 47. Predatory fish from the Great Lakes-St. Lawrence River area had the highest average arsenic levels. Species like lake trout and walleye in places like Georgian Bay, Eastern Lake Erie, all Lake Ontario locations, and the St. Lawrence River ranked in the top 25% for arsenic levels. The highest arsenic values were found in lake trout from Georgian Bay and Lake Ontario, walleye from the St. Lawrence River, and chain pickerel from the Lower Salmon River, NB. Conversely, fish from the prairies and southern BC had lower arsenic concentrations, usually falling within the bottom two quartiles.

To account for variations in arsenic accumulation among coexisting fish species, analyses were conducted within single species across sites instead of combining data for all species. Lake trout, walleye, and smelt were compared. Length-adjusted arsenic concentrations in lake trout were highest in Lake Ontario, particularly in the Eastern and Niagara basins. Moderate levels were observed in other Great Lakes areas, while the lowest concentrations were found in remote locations like Lake Athabasca and Lake Edouard. For walleye, the lowest arsenic levels were reported in the west, contrasting with the highest levels in the St. Lawrence River. Similarly, arsenic levels in rainbow smelt closely mirrored those in lake trout, with the highest concentrations in Lake Ontario.

Findings on arsenic in mussels supported the fish data, showing consistently higher arsenic levels in Lake Ontario. However, differences between fish and mussels at specific sites suggest that factors like mobility and habitat might influence arsenic exposure, with mussels reflecting more localized conditions compared to the broader range covered by lake trout.

Figure 47: Whole body mean concentrations of arsenic (mg/kg wet weight) of top predatory fish in Canadian water bodies from 2010 to 2018

Figure 48: Mean whole body concentrations of arsenic (mg/kg wet weight) in rainbow smelt in Canadian water bodies from 2010 to 2018

The range of arsenic concentrations in Canadian fish, from 0.003 to 3.89 mg/kg wet weight indicates both natural and anthropogenic sources of arsenic. While direct correlations between arsenic in water and fish are not always clear, the general trend suggests that fish from areas with higher arsenic levels in the environment tend to have increased arsenic burdens. Potential pathways of arsenic to the lower Great Lakes include wastewater effluent and agricultural use of biosolids, with urban runoff from road salting potentially exacerbating winter arsenic mobilization.

High arsenic levels in Canadian fish have often been linked to areas around active or historical gold mines, though not all mine tailings result in fish contamination, depending on arsenic's integration into the food web. In Kejimkujik Lake, Nova Scotia, which was impacted by historic gold mining, fish were found to have high mercury levels, but relatively low arsenic concentrations compared to other regions examined.

Associated with silver and uranium mining, Great Bear Lake in NWT, has sediments contaminated with mine waste. However, little arsenic has been detected in the water column, suggesting arsenic is effectively immobilized in sediments and is not elevating fish arsenic concentrations. Similarly, in Lake Edouard, Quebec, despite its history with nickel and copper mining, lake trout showed some of the lowest arsenic levels. The origins of elevated arsenic in fish from the lower Great Lakes remain uncertain.

Temporal trends in the annual arsenic body burdens of Great Lakes fish, with long-term data available, were analyzed. The most extensive data set belonged to rainbow smelt, stretching back to the late 1970s in some locations, while data for trout mainly covered trends from 2000 onwards, with limited earlier records. These trends are summarized in Table 5.

Note: An asterisk (*) indicates a variation in the trend from earlier years.

Across the majority of Great Lakes sites, a decrease or stability in arsenic levels within fish species was observed, although notable increases were recorded downstream. The specific trends varied by lakes and species, reflecting the dynamic nature of environmental arsenic exposure over time and space.

In Lake Superior, no significant changes in arsenic levels were detected across all species. By contrast, Lake Huron saw a significant decrease in smelt arsenic levels, with a suggested decline in Georgian Bay yet consistent levels elsewhere. Interestingly, lake trout in Lake Huron maintained arsenic body burdens similar to those measured decades ago.

Western Lake Erie's arsenic trends remained unchanged from 1979 to 1989, followed by a significant decrease of arsenic in walleye from 2007 to 2014, whereas smelt arsenic levels stayed the same. Conversely, lake trout in Eastern Lake Erie exhibited a non-significant decrease in arsenic levels from 2006 to 2018, despite historical data suggesting an increase from the mid-1980s.

Lake Ontario presented a complex pattern, with prey fish like rainbow smelt showing significant declines in arsenic levels at most sites, except the eastern basin. Meanwhile, arsenic levels in lake trout fluctuated, increasing in certain areas between the late 1970s and early 1980s as compared to the mid-2000s to 2010, highlighting a possible shift in environmental arsenic sources or bioavailability, potentially influenced by changes in diet or increased arsenic inputs to the lake.

3.2.4.4 Factors that impact arsenic accumulation

Correlations between various biological metrics and whole-body arsenic concentrations in fish were observed. It was found that characteristics such as length, weight, sex, and age could influence how much arsenic a fish accumulates. This is because larger or older fish might change their diets or habitats, potentially leading to greater contaminant exposure.

For lake trout, a clear correlation was established between fish length and arsenic levels across all sites, indicating that larger lake trout tend to carry more arsenic. This pattern was similar for weight, showing that as lake trout grow heavier, their arsenic burden increases. However, this relationship wasn't consistent for walleye, where only in the St. Lawrence River did larger fish have significantly higher arsenic concentrations, suggesting that the link between size and arsenic accumulation can vary by location.

No consistent trend was observed when comparing arsenic concentrations based on where the fish feed or what they were consuming, indicating a complex interaction between a fish's diet, habitat, and arsenic exposure. In some instances, however, a fish's position in the food chain, known as Delta 15N (δ¹⁵N) and whether it fed closer to shore or in deeper waters did show significant relationships with arsenic levels, suggesting that these factors may play roles in arsenic accumulation.

The results underscore the complexity of arsenic bioaccumulation in fish, suggesting it is influenced by a combination of factors, including diet changes and habitat preferences, rather than just the size or age of the fish. At the site level, a variety of parameters were significant in predicting arsenic levels in fish, highlighting the importance of local environmental conditions and food web dynamics in understanding arsenic exposure. Therefore, different factors are affecting arsenic levels in fish, from their physical characteristics to the broader ecosystem they inhabit.

Figure 49: The relationship between arsenic body burden and fish length, age and Delta 15N (δ¹⁵N) for lake trout from sites across the national network

3.2.5 Findings and recommendations

There is a gradual and significant increase in arsenic concentrations in sediment cores measured in various sites within the Great Lakes. Concentrations at some local spots indicate ongoing arsenic pollution likely attributed to nearby industrial activities.

In terms of surface waters, the data indicates mostly stable or decreasing trends in arsenic concentrations with some sites showing a slow rate of increase. There were also specific sites with high concentrations of arsenic identified, particularly in agriculturally dominated regions such as the Assiniboine-Red drainage region, where arsenic concentrations are influenced by land use. Additionally, arsenic levels tend to increase downstream in the Great Lakes connecting channels, indicating localized impacts and the presence of arsenic inputs along these water bodies. In this area, the majority of monitoring sites reported arsenic concentrations below the CCME long-term water quality guideline for the protection of aquatic life. However, there have been exceedances at specific locations, such as Niagara-on-the-Lake and Wolfe Island.

The monitoring of arsenic in surface waters and the Great Lakes, including the establishment of long-term monitoring sites, suggests a robust framework for collecting data. However, the presence of regions with limited data, particularly in northern areas, and the variability in arsenic levels across different water bodies indicate a need for continued and possibly expanded monitoring efforts to ensure a complete understanding of arsenic distribution and trends in Canadian waters.

The temporal trends in arsenic in Great Lakes fish generally show a decrease or stability, although there are variations by lakes and species. The data suggests that sediments in both deeper waters and nearshore areas contain elevated levels of arsenic, largely attributed to anthropogenic sources such as industrial pollution. This arsenic buildup in sediments likely plays a role in arsenic exposure for aquatic organisms. The fact that fish feeding in these areas show varying arsenic concentrations further supports the idea that these sediment-bound pollutants are influencing the ecosystem, though the interaction between fish diet, habitat, and arsenic exposure remains complex.

There were also various sites with high concentrations of arsenic in fish including the Great Lakes-St. Lawrence River area, particularly Georgian Bay, Eastern Lake Erie, all Lake Ontario locations, and the St. Lawrence River. These areas showed the highest average arsenic levels in fish, indicating regional hotspots of arsenic contamination. Anthropogenic sources were identified as a major contributing factor to arsenic pollution in these areas. Nevertheless, over 99% of fish across Canada were not negatively impacted by arsenic contamination, suggesting a varied level of concern depending on geographic and ecological contexts.

In most cases, arsenic levels in fish from across Canada did not exceed the risk-based guideline for human health consumption. Continuous monitoring and research on the chronic arsenic exposure levels for fish might be required to further understand and mitigate arsenic pollution, especially in identified hotspots and for species showing increases in arsenic levels over time.

The dynamic of arsenic pollution in aquatic environments primarily involves anthropogenic sources entering the water and eventually settling in sediments, where the arsenic can remain for extended periods. This long-term accumulation of arsenic in sediment poses ongoing risks to aquatic ecosystems. The observed relationship between where fish feed—whether closer to shore or in deeper waters—suggests that fish feeding in areas near sediment impacted by arsenic are more likely to accumulate higher levels of the toxin. This pattern indicates that fish populations in these regions, particularly those feeding near or on contaminated sediments, may be more vulnerable to arsenic exposure. Additional studies are needed to better understand and confirm the relationship between fish feeding behaviors, sediment contamination, and arsenic accumulation, to more effectively address and mitigate the ecological impacts of arsenic pollution.

3.3 Wildlife

3.3.1 Benchmark levels of arsenic in wildlife

Establishing safe arsenic levels for animal health is complex due to the diverse effects of arsenic across various animal species, breeds, and even individuals. Factors such as age, health status, and diet composition, including other minerals and chemicals, can significantly alter an animal's arsenic tolerance. Additionally, arsenic exists in several chemical forms, each with differing toxicities. The intricacies of arsenic metabolism and its potential for bioaccumulation in different tissues add layers of complexity to setting universally safe levels. As a result, creating standards to ensure safety for all animals is a challenging task that needs comprehensive research and a tailored strategy.

Technological advancements are paving the way for the use of cellular testing to examine arsenic's effects on animal cells which allows scientists to estimate its impact on cellular functions and genetics. The identification of harmful arsenic levels provides a pathway towards the establishment of benchmarks for wildlife.  However, for the current analysis, as no relevant guidelines or standards exist, concentrations of arsenic in wildlife will be assessed against background concentrations and in terms of increasing or decreasing trends.

Toxicological effects and risks of arsenic exposure

Arsenic exposure can have harmful effects on wildlife, but these effects vary depending on the level and type of exposure. Laboratory studies have shown that high arsenic exposure can negatively impact reproduction, development, growth, and survival in birds and mammals. Birds that have been exposed to toxic levels may show signs like muscle incoordination and weakness, leading to death, while mammals can suffer from appetite loss, dehydration, and trembling.

In Canada, wildlife arsenic exposure is generally low, but higher levels have been found in areas with mining activity or pesticide use. For example, in Yellowknife, arsenic contamination from historical gold mining has been linked to brain and eye abnormalities in muskrats and red squirrels. Similarly, an insecticide containing arsenic used to control the mountain pine beetle in British Columbia was found to stunt bird growth.

Arsenic toxicity also depends on its chemical form. Inorganic arsenic is more toxic than organic compounds. Some organic forms, like arsenobetaine, are non-toxic and commonly found in marine wildlife. Marine animals often have higher levels of arsenic, but mostly in non-toxic forms.

Temporal trends in wildlife

Long-term monitoring is crucial for detecting changes in wildlife exposure to contaminants. Under the Northern Contaminants Program, arsenic trends in the kidney have been measured in caribou from three Arctic regions. The Porcupine herd in the northern Yukon showed a decline in kidney arsenic concentrations, while the Qamanirjuaq and Tay/Finlayson herds showed no significant changes. Similarly, moose from the Yukon showed a decline in kidney arsenic concentrations from 1994 to 2003. However, liver samples from ringed seals from three Canadian sites between 1998 and 2019 showed no change in arsenic concentrations.

Figure 50: Arsenic concentrations (ppm, dry weight) in kidney of the barren-ground Porcupine caribou herd from the northern Yukon from 1993 to 2021 (n = 600 individuals)

Figure 51: Arsenic concentrations (ppm, dry weight) in liver of ringed seal from three collection sites at Arviat (Nunavut; n = 195 individuals), Nain (Newfoundland/Labrador; n = 94 individuals) and Sachs Harbour (Northwest Territories; n = 116 individuals) from 1998 to 2019

Arsenic in eggs of various gull species (aquatic feeders) and the European starling (terrestrial feeder) have been also monitored from 2008 to 2020.

Figure 52: Monitoring locations of eggs under the CMP. Eggs of aquatic-feeding gulls are collected annually from 14 colonies across Canada (red circles) plus 5 Great Lakes colonies (not shown)

Note: Eggs of European starlings (an indicator of terrestrial exposure) are also collected annually at 5 large metropolitan areas (yellow stars) and from nest boxes within these areas that are associated with 3 land-use types: in close proximity to landfill sites, within urban/industrial centres, and 10 to 40 kilometres outside urban/industrial areas (rural).

For gulls monitored under the CMP, arsenic trends were assessed from 2008 to 2020. There were significant declines in arsenic concentrations in eggs from both marine and freshwater gull colonies. Terrestrial starlings also showed a similar decline in arsenic concentrations in eggs. However, it's worth noting that the overall arsenic concentrations in eggs were relatively low, which can introduce uncertainties in quantification. The potential influence of improved analytical techniques with lower detection limits in recent years on these trends is unclear. Nevertheless, the data suggests that arsenic concentrations in eggs across Canada have not increased during this period.

Spatial patterns in wildlife

Arsenic levels in wildlife in Canada vary across different environments and species. In marine environments, birds and mammals like gulls and seals have higher arsenic concentrations, mainly due to arsenobetaine, a non-toxic form of arsenic found in seawater. In contrast, species that feed in freshwater habitats like bald eagles and minks have much lower arsenic levels in their livers.

Egg studies from 2016 to 2020 show that gull eggs from marine environments have higher arsenic levels (0.20 to 0.35 ppm) than those from freshwater or terrestrial habitats. However, arsenic concentrations in terrestrial starling eggs are low, regardless of the nesting site, indicating a lack of increased exposure in different environments.

Figure 53: Mean concentrations of arsenic in gull eggs across Canada from 2016 to 2020 (ppm, dry weight)

Note: Location-specific values are means of measurements based on pooled samples composed of multiple eggs. Sample sizes of mean values ranged from 4 to 16 per colony site.

Figure 54: Mean concentrations (+ standard deviation) of arsenic in starling eggs at sites across Canada from 2016 to 2020 (ppm, dry weight). Three land-use types are indicated. Measurements were made on pooled samples composed of multiple eggs

Additionally, human activities have led to increased arsenic levels in some wildlife. Near historic gold mines in Canada that are no longer operating, small mammals show higher arsenic concentrations in their livers and kidneys. Birds like the American tree sparrow and gray jay also show elevated levels of arsenic when living near these contaminated sites. Agricultural practices using arsenic-based chemicals have increased arsenic levels in some birds.

In more remote areas, local geology and atmospheric deposition can affect arsenic exposure in wildlife. Moose, deer, and other herbivores show low but varying arsenic levels, influenced by their diet and habitat. Similarly, terrestrial carnivores like lynx and marten have low arsenic levels in their livers.

Studies on frogs in Alberta and the Northwest Territories from 2011 to 2018 show that adult wood frogs and northern leopard frogs have low arsenic concentrations. However, tadpoles and young frogs show higher levels, possibly due to increased exposure in water or their diet during their early stages of development.

Uptake routes and bioaccumulation of arsenic in wildlife

Arsenic has been extensively measured in various wildlife species across Canada from 1993 to 2021. The most commonly analyzed tissue is the liver, with arsenic concentrations ranging from 0.01 to 66 ppm (dry weight). Marine birds and mammals typically show higher arsenic levels compared to their terrestrial counterparts, as well as freshwater mammals and waterbirds (see Figure 55).

Out of 2,501 liver measurements from various wildlife species, 80% had mean arsenic concentrations below 4 ppm (dry weight). Kidney tissues also exhibited varying arsenic levels (0.02 to 10 ppm dry weight), with 94% of 2,225 measurements falling below 4 ppm (dry weight). Notably, the highest liver arsenic concentrations were found in certain marine birds from Baffin Bay (1998) and in an American tree sparrow from Yellowknife, Northwest Territories (see Figure 55). The highest recorded kidney concentration was in deer mice, also from Yellowknife, which has been affected by historic mining releases of arsenic.

Figure 55: Arsenic concentrations (ppm, dry weight) in liver and kidney of wildlife measured in Canada from 1993 to 2021

The accumulation of arsenic in wildlife is influenced by factors like proximity to point-source releases from human activities, diet, and the animal's ability to process and eliminate arsenic. Environmental factors such as pH and the chemical forms of arsenic also affect its uptake.

Generally, arsenic concentrations are higher in the liver and kidney compared to other tissues. In marine mammals and birds, liver concentrations can be 2 to 3 times higher than muscle. Arsenic in blood, indicative of recent exposure, varied in common eiders from Nunavut in 2013 and 2014, with mean concentrations ranging from 1.7 to 2.5 ppm (dry weight). Interestingly, arsenic accumulates in the nails of snowshoe hares but is usually undetectable in bones. In ringed seals, most of the arsenic burden (90%) is found in blubber as arseno-lipid compounds, in contrast to other tissues where arsenic also accumulates (Ebisuda et al. 2002).

Arsenic trends in gull eggs were categorized based on marine and freshwater habitats. The mean arsenic concentrations in eggs of marine gulls, freshwater gulls, and terrestrial-feeding starlings were 0.30 ppm, 0.06 ppm, and 0.04 ppm (dry weight), respectively (see Figure 56). The highest concentrations were recorded in marine gull colonies at Gull Island in Newfoundland and Kent Island in New Brunswick. It is important to note that eggs generally accumulate less arsenic than other bird tissues.

Figure 56: Arsenic concentrations (ppm, dry weight) in eggs of gulls from marine and freshwater habitat and starlings from terrestrial habitat from 2008 to 2020

The vast majority of gull and starling egg measurements (97% and 95%, respectively) had arsenic concentrations above the method detection limits. Additionally, arsenic was measured in eggs of snapping turtles (Chelydra serpentina) in Ontario, showing similar concentration ranges to those found in bird eggs.

Additional details on the wildlife data are available in Tables 8 and 9 of section 9.7 in the Annex of this report. 

3.3.2 Findings and recommendations

The research reveals that arsenic primarily accumulates in the liver and kidneys of vertebrate animals, though blubber may also contain much of the arsenic burden of some marine mammals. Wildlife inhabiting marine environments tend to exhibit higher arsenic concentrations than their counterparts in freshwater or terrestrial ecosystems. This is largely due to the biotransformation of inorganic arsenic into less toxic organic forms, such as arsenobetaine and arsenocholine, by marine organisms.  Notably, unlike some other contaminants, arsenic does not show an increase in concentration up the food chain.

Since 1993, arsenic levels within wildlife populations across Canada have been stable or declining. This trend suggests a reduction in pollution exposure, which is a positive indicator for ecosystem health.

Arsenic concentrations in Canadian wildlife generally align with natural background levels and are relatively low. However, these concentrations vary significantly based on several factors, including the habitat, dietary preferences, physiological characteristics, and specific environmental conditions of the animals in question. Notably, localized contamination sites, such as former mining areas and regions where monosodium methyl arsonate (an arsenic-based pesticide) was used, exhibit higher arsenic concentrations, particularly in small land mammals and insect-eating birds. Interestingly, starling eggs from industrial, landfill, or rural sites do not display significant differences in arsenic exposure.

Overall, the risk of arsenic toxicity to wildlife in Canada appears to be low. The majority of detected arsenic exists in non-toxic forms and falls within natural background levels. However, it is essential to recognize that limited research has been conducted on the subtle, non-lethal effects of arsenic exposure on free-ranging wildlife. Existing evidence, particularly from historical mining sites, suggests potential sublethal impacts on small mammals, warranting further investigation. This includes in-depth analysis of the types of arsenic compounds and monitoring close to contaminated sites to assess the risk of arsenic exposure more accurately in wildlife.

3.4 Conclusion of arsenic in the environment

The monitoring of arsenic levels in air across Canada indicates that industrial regions and densely populated areas exhibit elevated arsenic concentrations. Despite these localized spikes, the overall 24-hour and annual average concentrations of arsenic in PM_2.5 remain below provincial air quality guidelines. This suggests that current air quality management practices are effective in keeping arsenic levels within safe limits.

Monitoring data for surface waters show that arsenic concentrations are mostly stable or decreasing over time. However, specific sites in the Great Lakes and agricultural dominated regions exhibit higher arsenic concentrations. While the majority of monitoring sites report arsenic levels below the CCME long-term water quality guideline for the protection of aquatic life, certain locations have recorded exceedances. These findings underscore the importance of continued monitoring to manage and mitigate arsenic pollution in water bodies.

Arsenic concentrations in sediments, particularly in the Great Lakes, are gradually increasing, with significant rises observed in some localized areas. These trends suggest that additional action and more comprehensive monitoring are necessary to address the increasing arsenic levels in sediments and their potential long-term impacts on the environment.

Extensive monitoring of arsenic in biota, including fish and wildlife, reveals that while arsenic primarily accumulates in the liver and kidneys of vertebrate animals, concentrations are generally low and align with natural background levels. Notably, higher arsenic levels are observed in marine environments compared to freshwater or terrestrial ecosystems. Temporal trends indicate stability or a decline in arsenic levels within wildlife populations, suggesting effective environmental management practices. However, specific hotspots, such as the Great Lakes-St. Lawrence River area, show higher arsenic levels in certain fish species, indicating the need for ongoing monitoring and research to fully understand the implications for human health and ecological systems.

4. Risk management actions

The risk management actions implemented by the Government of Canada to control releases of toxic substances to the environment encompass a variety of measures, including legislation and regulations, pollution prevention planning notices, codes of practice, performance agreements, guidelines, policies, and strategies.

These risk management measures are put in place through a combination of legislative processes, stakeholder consultations, regulatory enforcement, and compliance promotion mechanisms. They are designed to address specific sources of environmental contamination, mitigate risks, and promote sustainable practices across various industrial sectors.

Legislation and Regulations: Legislation and regulations establish legally binding requirements for environmental protection and pollution control. These laws set standards, enforcement mechanisms, and penalties for non-compliance, ensuring that industries and individuals adhere to environmental best practices. Regulations provide specific rules under broader legislative frameworks, addressing areas such as emissions limits, waste disposal, and resource conservation.

Pollution Prevention Planning Notices: Pollution prevention planning notices require facilities to develop and implement plans to prevent or minimize the creation and release of pollutants into the environment. These notices typically set out specific requirements for developing and implementing pollution prevention plans, and reporting on progress. They aim to encourage proactive measures to reduce pollution at the source and promote sustainable practices.

Codes of Practice: Codes of practice provide industry-specific guidance on best practices for environmental management. These voluntary or mandatory standards outline recommended procedures for minimizing environmental impacts, improving efficiency, and ensuring compliance with regulatory requirements. They serve as practical tools for businesses to align operations with environmental goals.

Performance Agreements: Performance agreements are formal agreements between regulatory authorities and industry stakeholders that outline specific environmental performance targets and commitments. These agreements may involve voluntary commitments by industry to reduce releases, improve environmental practices, or meet certain environmental standards. Performance agreements provide a flexible approach to environmental management and often include mechanisms for monitoring and reporting progress.

Guidelines: Guidelines offer specific recommendations or best practices for industries, activities, or processes to minimize their environmental impacts. They provide practical advice on how to achieve regulatory compliance and improve environmental performance. While guidelines are typically non-binding, they are often developed in consultation with industry stakeholders and may be referenced by regulatory authorities when assessing compliance.

Policies and Strategies: Environmental policies and strategies outline overarching goals, principles, and action plans for sustainable development and pollution control. These frameworks guide government decision-making, influence regulatory development, and promote long-term environmental protection initiatives. They may focus on climate change mitigation, conservation efforts, or industry-specific sustainability targets.

The following section will evaluate the impact of different measures on arsenic releases. Various risk management actions have been identified that exert either a direct or indirect impact on the management and control of arsenic in the environment. This was completed by identifying actions that impact sectors of concern from the PSL assessment and evaluating if they reduce arsenic either directly or as a byproduct through optimizing production processes. While provincial and territorial efforts have played an important role in reducing arsenic releases to the environment, they are beyond the scope of this report, which focuses only on federal actions, primarily those taken under CEPA or the Fisheries Act.  Actions taken under intergovernmental processes, such as those of the Canadian Council of Ministers of the Environment (CCME), as well as international actions relevant to managing arsenic levels are also discussed.

4.1 Mining

Canada’s mining industry is the leading global producer of potash, and it is among the top five global producers of cobalt, diamonds, fluorspar, gemstones, gold, indium, niobium, palladium, platinum, tellurium, titanium concentrate, and uranium. Nearly 200 mines are operated in Canada, generating significant economic output.

Environmental concerns in the mining industry include the use of chemicals in ore processing, like cyanide and sulfuric acid, to produce ore concentrates. These processes can release harmful byproducts. Drilling and blasting involve explosives and lubricants that contribute to pollution. Waste materials generated from the processing of mined ore, commonly known as tailings, are stored in ponds, and their management can lead to chemical leaching into ecosystems.

Arsenic-containing waste is a common byproduct in mining operations, particularly gold mining, as arsenic minerals are often present in ore. Improper storage and disposal of mining waste can pose significant environmental risk.

4.1.1 Metal and Diamond Mining Effluent Regulations (2002)

To protect water and fish habitat from pollution from mining operations, regulations under the Fisheries Act were put in place in 1977. The Metal Mining Liquid Effluent Regulations (MMLER) were intended to limit harmful substances from base metal, uranium and iron ore mines entering the environment. Arsenic was listed as a deleterious substance in the MMLER, with an effluent release limit of 0.5 mg/L as a monthly mean concentration.

In 1993, the Assessment of the Aquatic Effects of Mining in Canada (AQUAMIN) was initiated in response to the federal government’s commitment to update and strengthen the MMLER. The objective of AQUAMIN was to examine the effectiveness of the MMLER, by conducting an assessment of the environmental effects of mining, and to formulate, on the basis of this assessment, recommendations in three key areas: (1) amendments to the MMLER, (2) the design of a national environmental effects monitoring (EEM) program for metal mining, and (3) information gaps and research needs. AQUAMIN was directed by a steering group that included representatives of all stakeholder groups. The assessment of the effects of metal mining on aquatic ecosystems in Canada included a review of over 700 reports related to more than 95 Canadian mine sites and detailed case studies for 18 sites.

The recommendations of the report were considered and in 2002, the Metal Mining Effluent Regulations were put in place to regulate discharges of effluent containing deleterious substances from metal mines to fish frequented water bodies and require environmental effects monitoring. Environmental effects monitoring was intended to help inform possible future changes to the regulations based on the need for enhanced protection of the aquatic environment from risks posed by already regulated substances or new substances that would need to be regulated. These regulations also authorized the use of certain bodies of water for deposit of harmful substances.

In 2018, the regulations were amended to cover effluents from diamond mines, lower the limits of harmful substances in mining effluents, strengthen acute lethality testing requirements for mine effluent and streamline environmental effects monitoring requirements. Reflecting these changes, the regulations were renamed to the Metal and Diamond Mining Effluent Regulations (MDMER). The regulations were amended again in 2021 to require acute lethality testing for invertebrate species for deposits of saline (saltwater) effluent into marine environments.

Today, the MDMER help protect Canada’s lakes and rivers by setting strict limits on the quality of effluent that can be discharged by metal and diamond mines. The regulations authorize the deposit of effluent into water frequented by fish and places referred to in subsection 36(3) of the Fisheries Act. Effluent must meet concentration-based limits for arsenic, which allows a maximum monthly mean concentration of 0.10 mg/L for mines that began operation after June 2021 and 0.30 mg/L for previously existing mines. Effluent must also have a pH that is between a minimum and maximum level and must not be acutely lethal.

The data reported by owners and operators of metal and diamond mines under the MDMER, combined with annual reports prepared by ECCC, reveal some exceedances in the prescribed limits and requirements set by the regulations. These reports are essential for tracking compliance and assessing the environmental impact of mining operations on water bodies. In the report for 2022–2023, monitoring data showed a 99.8% compliance rate for arsenic across monitored mines with two exceedances for arsenic in 2021, four in 2022, and three in 2023. Prior to these, the last recorded exceedances occurred in 2014. Exceedances indicate areas where the mining operations fail to meet the set environmental standards.

4.1.2 Environmental Code of Practice for Metal Mines (2009)

The Environmental Code of Practice for Metal Mines provides a comprehensive framework designed to mitigate the environmental impacts associated with the metal mining sector. This code covers the full lifecycle of mining activities, from exploration and feasibility through to planning, construction, operations, and eventual closure. It addresses a wide range of environmental concerns, including the management of air releases, water, waste, and biodiversity conservation​​.

The code is aligned with the MDMER under the Fisheries Act, serving as a guiding document to promote best environmental management practices throughout the mining industry. While not legally binding, the code is influential, as it can be voluntarily adopted by mining companies, incorporated into environmental performance agreements between the industry and government, and used as a benchmark for best practices in environmental management​​.

By including guidance aimed at air quality and waste management, the code encourages the adoption of practices that can reduce the release of harmful substances, including arsenic, into the environment. For instance, by implementing advanced air emission controls and proper waste management procedures, mining operations can minimize the release of arsenic, which is often associated with the processing of certain ores. This not only helps in reducing the immediate environmental and health risks associated with arsenic releases but also contributes to the long-term sustainability and social responsibility of mining operations. While the code may be producing co-benefits with respect to arsenic releases through its comprehensive environmental management practices, the implementation of the recommendations in the code of practice is voluntary and is not tracked by ECCC.

4.1.3 Findings and recommendations

Federal risk management actions for the mining sector have been focused on controlling releases of harmful substances to water from mining effluent. Regulatory measures have generally been effective in reducing acute toxicity from mining effluent and most mines are compliant with the effluent release limits. Total arsenic releases have declined over the years, with declines in land, air and water releases. This decline occurs despite an increase in the number of operational facilities and production, suggesting that regulatory and voluntary measures have effectively prevented further escalation of releases to the broader environment beyond mine site boundaries.

Figure 57: Releases of arsenic from metal mines from 2000 to 2022

Note: There was a large spike in arsenic releases to water (approximately 259 tonnes) in 2014, due to a tailings pond breach at the Mount Polley Mine, which has been removed from the graph.

Nevertheless, as demand and productivity in the industry have increased, volumes of unwanted byproducts such as arsenic waste have increased accordingly. On-site arsenic disposals are accumulating at an increasingly higher rate, likely due to changing mineralogy of ore deposits, rising production levels, and the improved capture of arsenic to waste streams.  

To maintain existing progress on arsenic controls and enhance performance it is recommended to continue annual reporting under the MDMER and work with industry to address the causes of reported exceedances. Consideration should also be given to exploring ways to assess the extent of industry implementation of the voluntary code of practice.

4.2 Metal and mineral production

Canada's metal and mineral production sector produces critical materials such as iron, steel, copper, lead, zinc, nickel, aluminium, potash, and titanium dioxide.

In the production of base-metals, ore concentrates from mining operations and other feedstocks may be heated to either separate the metal from impurities or to produce a physical or chemical change in the feedstock. This step often releases particulate matter that contains metals, such as arsenic. The subsequent refining stages that further purify the metal to meet quality standards, may also potentially release heavy metals into the air and water. This sector primarily focuses on non-ferrous metals, distinct from iron and steel production.

In the production of iron and steel, the process begins with the extraction of raw materials, followed by pelletization, a critical step for iron ore. Here, fine iron ore particles are agglomerated into pellets, making them suitable for use in blast furnaces. Smelting in this sector involves the reduction of iron ore into molten iron in a blast furnace, using metallurgical coke as a reducing agent. Subsequent steps generally include the production of steel from iron in a basic oxygen furnace or an electric arc furnace. The smelting of ilmenite ore produces titanium dioxide and iron which can be transformed into steel. Similar to base metals, these processes emit particulate matter and can release heavy metals.

In the mid 1990s, a Strategic Options Process was launched with the establishment of issue tables to address environmental concerns from various industrial sectors, including iron and steel production and base metals smelting. Issue tables, which consisted of representatives from federal, provincial, and territorial governments, industry groups, and public advocacy organizations, reviewed release data and evaluated potential control strategies ranging from voluntary measures to strict regulatory frameworks. From 1995 to 1996, potential management options were evaluated for toxic substances released from iron and steel production, focusing on air and wastewater effluents. A variety of control measures were considered for this sector, from voluntary programs to federal regulations, ultimately recommending voluntary programs and non-regulatory environmental performance standards, with a backup of potential regulatory requirements. Similarly, from 1996 to 1997, the base metals smelting sector was evaluated, concentrating on toxic substances including inorganic arsenic compounds.  The final recommendations for this sector supported a blend of strengthened voluntary initiatives and environmental performance standards, supplemented by regulatory measures, if necessary, to effectively manage and reduce emissions of the toxic substances.

Base metals smelting and refining

4.2.1 Environmental Code of Practice for Base Metal Smelters and Refineries (2006)

The Environmental Code of Practice for Base Metals Smelters and Refineries serves as a guiding framework for the sector to mitigate its environmental impacts, including from arsenic releases. Key aspects of the code in managing arsenic include:

• Emission reduction - advocates for the adoption and maintenance of advanced pollution control technologies to reduce arsenic emissions during metal and mineral production
• Environmental performance standards - establishes metal air emissions limit targets for various metals including arsenic (0.3 µg/m3/24hrs), promoting the adoption of technologies and practices capable of meeting these limits
• Water and wastewater management - guidelines are provided for treating water and wastewater containing arsenic to recommend facilities meet a stringent value of 0.5 mg/L of arsenic in a monthly quality standard before discharge
• Waste management - recommends secure storage and treatment protocols for wastes to prevent environmental contamination
• Monitoring and reporting - recommends continuous monitoring of pollutant levels in the environment, including arsenic, and reporting to regulatory bodies to ensure adherence to environmental standards and facilitate timely interventions
• Community engagement and transparency - emphasizes open communication with local communities and stakeholders regarding pollutant management, enhancing mutual understanding and cooperation

The code of practice itself does not require reporting and its adoption is voluntary. However, from 2006 to 2018, the 11 facilities that implemented pollution prevention plans under the Pollution Prevention Planning Notice for Base Metal Smelters and Refineries and Zinc Plants (discussed below) reported fully implementing more than 80% of applicable recommendations from the code of practice. From 2018 to present, reporting on the code of practice continues as part of the Performance Agreement Concerning Air Pollutants for Base Metal Smelters and Refineries (also discussed below). To date, four facilities fully implemented an average of 92% of their applicable recommendations while the other four facilities have implemented 100% of their applicable recommendations.

4.2.2 Pollution prevention planning notice for base metal smelters and refineries and zinc plants (2006-2018)

In 2006, the Government of Canada published its “Notice requiring the preparation and implementation of pollution prevention plans in respect of specified toxic substances released from base metals smelters and refineries and zinc plants” under CEPA. This Notice required the base metals smelting and refining sector to prepare and implement pollution prevention plans by December 31, 2015. The risk management objective of this Notice was to consider the application of best available techniques to prevent and control pollution in order to avoid or minimize pollutants and waste and reduce risks to the environment or human health while meeting air emission targets.

The planning notice required specific facilities to develop and implement pollution prevention plans aimed at managing the release of designated toxic substances from base metals smelters, refineries, and zinc plants. The substances of concern included particulate matter containing metals, respirable particulate matter less than or equal to 10 microns (PM₁₀), and inorganic arsenic compounds.

Facilities subject to the planning notice were also required to consider best available techniques for pollution prevention and control, as outlined in the Environmental Code of Practice for Base Metals Smelters and Refineries. The effective implementation of these techniques is expected to provide a co-benefit in arsenic emission reductions.

From 2005 to 2018, the sector achieved significant emission reductions, meeting all targets specified in the notice for substances such as particulate matter. Reductions were achieved through improved air pollution controls and facility closures. By meeting particulate matter emission targets, the sector saw a 54% reduction in arsenic emissions, from 70 tonnes in 2005 to 36 tonnes in 2018.

4.2.3 Performance agreement concerning air pollutants from base metals smelters and refineries (2018-2025)

The environmental performance agreements aim to reduce air releases of sulphur dioxide (SO₂), PM, and metals from base metal smelters and refineries and were in effect until 2025. These agreements, initially involving 11 base metals facilities owned by 5 companies, focus on implementing base-level industrial emission requirements (BLIERs) and promoting continuous emission reductions. This approach directly impacts arsenic releases by enforcing broader pollution control measures (setting targets on particulate matter containing the toxic metals emitted by the sector) and encouraging best practices outlined in the environmental code of practice. The participant facilities agreed to:

• participate in a working group with representatives from federal and provincial governments, other companies in the base metals sector, and the Mining Association of Canada, with a particular focus on releases of key metals, fine particulate matter and fugitive particulate matter
• participate in bilateral discussions with ECCC to discuss reports and results and to identify possible methods to further reduce emissions
• report on progress towards implementing applicable recommendations in the 2006 Environmental Code of Practice for Base Metal Smelters and Refineries

The reports indicate that all facilities are meeting their targets and commitments. ECCC verifies annual reports submitted by facilities, which include data on their performance against the BLIER targets for sulfur capture rates and particulate matter emission intensity.

For 2022, the eight facilities still participating met their BLIER targets for sulfur capture rate and PM emission intensity. Additionally, the facilities reported on their progress toward implementing applicable recommendations in the environmental code of practice, with most achieving high implementation rates.

By targeting SO₂ and PM reductions and encouraging pollution control best practices, these agreements help mitigate arsenic releases. Arsenic is a component of PM from these facilities, so implementing the code of practice's recommendations ensures better management of arsenic and other metals, potentially reducing their releases. Emissions of arsenic decreased from 36 tonnes in 2018 to less than 15 tonnes by 2022.

Iron, steel, and ilmenite sector

4.2.4 Environmental Code of Practice for Integrated Steel Mills (2001)

The Environmental Code of Practice for Integrated Steel Mills outlines good environmental protection practices for facilities that process iron ore into iron using coke and then process the iron into steel. This includes considerations for air releases and water effluents, which are of the highest priority due to their significant impact on the environment. The code encompasses a broad range of operational activities within integrated steel mills, from coke making to steelmaking, and finishing operations​.

While the code does not directly address arsenic releases, the practices and technologies it recommends for controlling releases and effluents indirectly contribute to managing arsenic releases. For example, the code specifies emission guidelines for PM from various production processes, such as blast furnaces, basic oxygen furnaces and electric arc furnaces, which are also potential sources of arsenic when processing materials containing this element. By targeting reductions in PM releases, integrated mills may also reduce the release of arsenic contained within those particulates.

The implementation of environmental performance indicators for particulate releases is another way the code indirectly impacts arsenic releases. By encouraging facilities to limit particulate releases to specific amounts per tonne of product produced, the code promotes the adoption of best practices and technologies that can lead to the overall reduction of harmful releases, including those of arsenic.

Additionally, the code recommends practices for the collection and control of furnace releases and fugitive releases, which can include arsenic among other pollutants. By engineering adequately sized pollution capture and abatement systems in facilities and developing documented procedures for operations that are potential sources of releases, integrated steel mills can better control the release of arsenic into the environment.

The code of practice itself does not require reporting and its adoption is voluntary so it is difficult to estimate its exact impact on the sector in terms of reducing emissions and releases of arsenic. A third-party review conducted by Environment Canada in 2003 indicated varying degrees of implementation of the code of practice recommendations across the sector with integrated mills reporting a higher rate of implementation compared to non-integrated mills.

4.2.5 Environmental Code of Practice for Non-Integrated Steel Mills (2001)

The non-integrated mills segment of the steel sector describes facilities that recycle steel scrap into commodity-grade steel using electric arc furnaces.

This code of practice outlines environmental concerns and alternative methods, technologies, designs, practices, and procedures that will minimize the adverse environmental effects associated with non-integrated steel mills. It also contains recommendations considered to be reasonable and practical measures to preserve and enhance the quality of the environment that is affected by these mills. Environmental performance standards are included for atmospheric emissions, water and wastewater, solids, and environmental management practices.

The code of practice does not require reporting, and its adoption is voluntary, so it is difficult to estimate its exact impact on reducing arsenic. The overall objective of the code is to identify minimum environmental performance standards for new non-integrated steel mills and to provide a set of environmental performance goals for existing mills to achieve through continual improvement over time.

4.2.6 Code of Practice to Reduce Emissions of TPM and VOCs from the Iron, Steel and Ilmenite Sector (2016)

The code of practice recommends best practices to control and limit fugitive air releases of total particulate matter (TPM) and volatile organics compounds (VOCs) from facilities within the iron, steel, and ilmenite sector. It provides guidance on implementing measures to mitigate environmental impacts associated with these releases.

This code of practice indirectly impacts arsenic releases by documenting best practices and recommending continuous improvement in addressing fugitive air emissions within the sector. By focusing on reducing TPM and VOC releases, the initiative contributes to a broader reduction of harmful pollutants, including arsenic, given its presence in certain raw materials used by the sector.

4.2.7 Pollution Prevention Planning Notice for Iron, Steel and Ilmenite Sector (2017)

The pollution prevention planning notice requires facilities within these sectors to prepare and implement a pollution prevention plan that addresses these substances. This plan includes setting targets for SO₂ and nitrogen oxide (NOx) emissions, and it encourages the implementation of best practices to reduce fugitive VOC emissions where feasible. 

The notice, in effect from May 2017 to June 2028, applies to any owner or operator of a facility listed in the notice or any iron, steel, or ilmenite smelting facility that commenced operations between those dates. Facilities subject to this notice are required to prepare a pollution prevention plan by specified deadlines, submit declaration and progress reports, and implement the pollution prevention plan by May 2028. 

Although the focus is on SO₂, NOx, and VOCs, the pollution prevention and control measures indirectly impact the management and reduction of other emissions, potentially including arsenic, by promoting overall environmental responsibility and the adoption of best practices in emission control. The initiative also emphasizes the importance of regular monitoring and control of emissions from facilities within these sectors. Given facilities are still in the process of implementing their pollution prevention plans, it is not possible to assess the effectiveness of the notice at this time.

4.2.8 Environmental Performance Agreement for the Iron Ore Pelletizing Sector (2018)

This agreement between ECCC and two companies, effective from January 2018 to December 2025, focuses on implementing BLIERs for the iron ore pelletizing sector. The key requirements under this agreement include achieving and maintaining the BLIERs for releases of air pollutants including PM_2.5.

In terms of risk management objectives, the agreement sets out specific performance objectives for air pollutants including PM_2.5 releases. Companies are required to ensure new induration furnaces must emit less than or equal to 20 grams of filterable PM_2.5 per tonne of pellet throughput, while existing furnaces must meet a target of less than or equal to 40 grams.

Although the agreement focuses on PM_2.5, SO₂ and NOx, its implementation indirectly impacts arsenic releases by establishing reduction strategies that would provide co-benefits for other pollutants commonly associated with the iron ore pelletizing process. By targeting key pollutants and promoting cleaner production practices, the agreement contributes to an overall reduction in the environmental impact of iron ore pelletizing operations. From 2018 to 2022, both facilities have achieved their target levels.

4.2.9 Findings and recommendations

While there are still some important sources of arsenic releases from the sectors, overall, there has been a reduction of arsenic releases in the metal and mineral production sector by 87% from 2003 levels. This reflects that significant progress was made to protect the environment.

Base metals smelting and refining

Base metal production was identified as a substantive source of arsenic in the PSL1. Since then, there have been significant reductions, due to improved pollution controls and facility closures. Since the publication of the Environmental Code of Practice for Base Metals Smelters and Refineries in 2006, facilities have made significant progress in reducing emissions of toxic substances. Facilities subject to the pollution prevention planning notice have been reporting annually on their progress in implementing the 38 recommendations from the code of practice. From 2006 to 2018, the 11 base metals smelting facilities have, on average, fully implemented over 80% of applicable recommendations. Currently, four facilities have fully implemented an average of 92% of their applicable recommendations while the other four facilities have implemented 100% of their applicable recommendations

Following the publication of the Strategic Options Report, efforts were put in place to reduce emissions of arsenic, cadmium, lead, nickel and mercury. In 2018, an overall reduction of 93% of these metals was achieved compared to 1988 emission levels. These included results obtained during the lifetime of the pollution prevention planning notice (2006-2018), where arsenic emissions were reduced by 54%, (down to 36 tonnes). Additionally, all facilities met their pollution prevention plan 2008 particulate matter reduction targets, and eight out of nine met their 2015 targets.

The environmental performance agreement, which aims to reduce releases of SO₂, PM, and metals from base metal smelters and refineries until 2025, has shown positive progress so far. All participating facilities met their BLIER targets for SO₂ and PM in 2022.  Since the performance agreements have been in place, emissions of arsenic have decreased from 36 tonnes in 2018 to less than 15 tonnes in 2022.

Based on the reporting data and analysis undertaken to date, the code of practice, pollution prevention planning notice and performance agreements for the base metals smelting sector have been very effective in reducing arsenic releases, although the sector still remains the largest source of arsenic releases (Figure 58). Ongoing tracking and reporting will help to ensure the continued success of these measures.

Figure 58: Releases of arsenic from base metal smelting and refining facilities from 2000 to 2022

Note: 2021 air release data is likely overestimated due to a sampling error at one large facility.

Iron, steel, and ilmenite sector

While the iron, steel, and ilmenite sector has an impact on arsenic in Canada, its releases are approximately 100 times lower than those of the base metal smelting sector. The federal focus in the iron, steel, and ilmenite sector has been on mitigating environmental risks associated with air emissions, effluents, and solid waste through codes of practice, a pollution prevention plan notice, and performance agreements. While arsenic is not always explicitly targeted, the overarching initiatives contribute to its reduction as part of broader pollution control strategies.

The results from the Environmental Codes of Practice for Integrated and Non-Integrated Steel Mills are difficult to quantify due to their voluntary nature and lack of mandatory reporting requirements. Nevertheless, the adoption of best practices outlined in the codes of practice likely contributed to overall pollution reduction.

In a similar manner, the Environmental Code of Practice for the Iron, Steel, and Ilmenite Sector as well as the Pollution Prevention Planning Notice for the Iron, Steel and Ilmenite Sector have likely contributed to a reduction in arsenic releases as a co-benefit of broader particulate control strategies. However, the lack of specific data on arsenic reductions makes it challenging to evaluate its full impact.

In 2024, ECCC conducted a review of the levels of implementation of the recommendations from the three codes of practice for the iron and steel sector (Sections 4.2.4, 4.2.5, 4.2.6), which indicated that over 90% of the recommendations have been implemented.

The Environmental Performance Agreement for the Iron Ore Pelletizing Sector has shown measurable success, with participating facilities achieving their targets for PM_2.5 emissions between 2018 and 2022. While the agreement does not directly address arsenic, the implementation of cleaner production practices and reduction strategies for fine particulates has indirectly reduced arsenic emissions.

Despite these efforts, challenges in collecting specific arsenic data persist, similar to base metals smelting and refining, making it difficult to fully understand the scope of arsenic reductions and other environmental improvements in the sector. Consideration could be given to strengthening reporting requirements (where relevant) and integrating arsenic-specific targets into existing frameworks.

Figure 59: Releases of arsenic from iron, steel and ilmenite facilities from 2000 to 2022

4.3 Electricity and combustion

Canada's energy landscape is characterized by a diverse mix of power generation sources, heavily weighted towards renewable energies, with hydroelectric power leading as the predominant source. The country is also a significant player in nuclear energy, while fossil fuels, particularly natural gas and to a lesser extent coal, continue to play a critical role in ensuring grid stability and meeting peak demand. Biomass is increasingly utilized for both power and heating, particularly in rural or remote areas.

Arsenic emissions from this sector primarily stem from the combustion of coal and biomass. Coal contains trace amounts of arsenic that can be released into the environment during combustion. When coal is burned, arsenic can be emitted as a gas or a particulate into the atmosphere, which can settle on land or water bodies, potentially leading to environmental and health risks. Modern coal-fired power plants in Canada are equipped with advanced emission control technologies such as electrostatic precipitators and flue gas desulfurization units that help reduce the release of arsenic along with other pollutants.

Biomass burning for power and heat can also emit arsenic, especially if the biomass material includes contaminated wood or agricultural residues. However, like coal, emissions depend significantly on the quality of the feedstock and the efficiency of the combustion technology. The Clean Electricity Strategy and Clean Electricity Regulations published in December 2024, reaffirm the federal government’s commitment for action on this sector.

4.3.1 New Source Emission Guidelines for Thermal Electricity Generation (2003)

The New Source Emission Guidelines for Thermal Electricity Generation in Canada set practical baseline standards for any fossil-fuel-based generating unit, including replacements using equivalent or steam-generating technology, with first commercial operation after April 1, 2003. These guidelines recommend limits on the releases of air pollutants including PM from new generating units operated for the sale of electricity. They aim to reduce releases of air-polluting discharges from future additions to electric generating system capacity using control methods available to the industry for the abatement of specified air pollutants​​.

While the guidelines do not specifically mention arsenic releases, the broader focus on reducing releases of PM and adopting cleaner combustion indirectly impacts arsenic releases. By encouraging the use of cleaner combustion processes and more efficient energy generation technologies, the guidelines contribute to the reduction of other pollutants, including arsenic. The use of cleaner fuels, such as natural gas and biofuels rather than coal, typically results in lower releases of pollutants, which aligns with the concept of pollution prevention​​.

4.3.2 Reduction of Carbon Dioxide Releases from Coal-Fired Generation of Electricity Regulations (2018)

The Reduction of Carbon Dioxide Emissions from Coal-fired Generation of Electricity Regulations, first introduced in 2012 and updated in 2018, primarily target the reduction of greenhouse gas (GHG) releases from coal-fired electricity generating units. These regulations aim to accelerate the phase-out of conventional coal-fired power generation by 2030, setting a performance standard of 420 tonnes of carbon dioxide per gigawatt hour (t/GWh) by December 2029. Compliance can be achieved through various means, including the installation of carbon capture equipment, transitioning to natural gas, or shutting down operations​​.

While these regulations directly focus on carbon dioxide releases, they indirectly impact arsenic releases due to the presence of arsenic in coal. By encouraging the phase-out of coal-fired generation or the adoption of cleaner technologies, the regulations contribute to reducing the overall emission of pollutants, including arsenic, which can be present in coal ash and releases. The shift towards cleaner energy generation methods, such as natural gas or carbon capture technologies, not only targets GHG releases but also helps mitigate the release of other harmful substances, including arsenic, from power plants.

The regulatory impact analysis statement highlights the commitment to reducing GHG releases and air pollutants, acknowledging that coal-fired electricity generating units are among the highest emitters in Canada. The 2018 amendments are expected to significantly contribute to Canada's reduction of GHG releases, with an anticipated reduction of approximately 94 megatonnes (Mt) of carbon dioxide equivalent (CO₂e) over the 2019 to 2055 period preventing the release of over 1000 tonnes of arsenic. This reduction is also expected to yield significant health and environmental benefits from improved air quality, alongside climate change benefits​​.

4.3.3 Findings and recommendations

Canada's efforts to reduce GHG emissions as part of its climate change strategy have been associated with substantial reductions in arsenic emissions within the power generation sector. This decline is primarily attributed to a strategic shift towards lower-GHG emitting energy sources and away from coal, advancements in combustion efficiency, and the implementation of advanced emission control technologies. The transition from fossil fuels to non-emitting sources such as hydro, wind, nuclear and solar has been a beneficial factor in reducing arsenic emissions, as these energy forms do not involve combustion processes that typically release arsenic found in fossil fuels.  Additionally, technological enhancements in combustion systems have increased fuel use efficiency, thereby decreasing the volume of arsenic-laden particulates per unit of energy produced.

As a result of these actions, combined with provincial initiatives and support for lower-emitting sources, arsenic emissions in the electricity sector have decreased markedly, with a reduction of 87% from 2003 levels, plummeting from 3,176 kg to just 409 kg by 2022.

Figure 60: Releases of arsenic from coal fired power plants from 2000 to 2022

Note: No releases to land were recorded since 2003. Releases to land prior to 2003 were removed from the graph as, according to the 2003 NPRI changes, these would be considered disposals.

4.4 Wastewater, municipal biosolids and waste

In Canada, the management of waste and municipal biosolids is a shared responsibility managed by a combination of federal, provincial, territorial and municipal actions aimed at protecting the environment and public health. Provincial and territorial governments are responsible for approval, licensing, and monitoring of waste management operations, such as landfills and recycling activities, as well as establishing programs to divert waste from disposal. Municipal governments are responsible for collection and diversion such as composting and recycling, as well as the disposal of solid waste within their jurisdiction.

Arsenic is present in different amounts in food and water making its way to wastewater through the human diet, where changes in population have a direct effect on wastewater levels.

Wastewater

4.4.1 Wastewater Systems Effluent Regulations (2009)

The Wastewater Systems Effluent Regulations (WSER) under Canada's Fisheries Act strategically address pollution by setting mandatory baseline effluent quality standards achievable through secondary level of treatment to protect aquatic life and human health. Applicable to wastewater systems discharging 100 m³ or more daily into fish-frequented waters, the regulations set limits on biochemical oxygen demand, suspended solids, un-ionized ammonia, and total residual chlorine, and prohibit the release of acutely lethal effluent. Exemptions include Arctic regions (Nunavut, Northwest Territories, and north of the 54^th parallel in Quebec and Newfoundland and Labrador), with specific equivalency agreements in place for Yukon and Quebec. System operators are required to regularly submit monitoring reports to demonstrate compliance, and there are provisions for transitional authorizations to accommodate upgrades in communities lacking adequate treatment.

While the WSER do not directly address arsenic releases, the requirement for secondary wastewater treatment indirectly contributes to reducing releases of arsenic and other hazardous substances entering aquatic ecosystems as communities with no or insufficient treatment install or upgrade treatment systems. This, in turn, helps in protecting both aquatic life and public health from the adverse effects of pollution.

4.4.2 CCME Canada-wide Strategy for the Management of Municipal Wastewater Effluent (2009)

The Strategy is a concerted effort across jurisdictions to address one of the largest pathways to the environment of water pollution in the country. This strategy outlines a harmonized approach to wastewater management, ensuring that wastewater facilities across Canada achieve at least secondary level of treatment. It sets National Performance Standards for effluent quality, including limits on carbonaceous biochemical oxygen demand, total suspended solids, and total residual chlorine, aimed at reducing the risks posed to human health and the environment from wastewater discharges​​. The federal Wastewater Systems Effluent Regulations were put in place to help implement the Strategy.

While the strategy itself does not directly address arsenic releases, its focus on improving wastewater treatment processes and effluent quality indirectly impacts the management of arsenic and other hazardous substances.

Biosolids

Biosolids, which are nutrient-rich organic materials derived from the treatment of domestic sewage in a wastewater treatment facility, are commonly repurposed as fertilizer to improve soil quality and promote plant growth, subject to strict quality and application standards. The use of biosolids is regulated to control contaminants and pathogens, ensuring that their application does not harm the environment or human health. This includes limits on metals such as arsenic.

The Canadian Food Inspection Agency (CFIA) regulates the import and sale of biosolid-based fertilizers under the Fertilizers Act, ensuring they meet safety standards for contaminants like arsenic. However, the manufacturing, application, and disposal of these products are governed by provincial and municipal regulations.

4.4.3 CCME Canada-wide Approach for the Management of Wastewater Biosolids (2012)

The CCME Canada-wide Approach for the Management of Wastewater Biosolids is a framework to address the increasing quantity of municipal biosolids produced as a result of new and upgraded wastewater facilities. This approach is designed to promote the beneficial use and sound management of municipal biosolids, municipal sludge, and treated septage across Canada, focusing on the utility and resource value of these materials while minimizing potential risks to the environment and human health​​​​.

The approach emphasizes the importance of considering the utility and resource value of biosolids, such as their nutrient content, organic matter, and energy. It encourages beneficial uses based on strategies that minimize environmental and health risks, as well as GHGs. Beneficial management practices for biosolids include composting, agricultural land application, and combustion for energy production, with a strong preference for these uses over disposal methods like combustion without energy capture or burial in landfills, which do not constitute beneficial uses​​.

While the approach might indirectly impact arsenic releases by promoting the beneficial use of biosolids and minimizing their disposal, the direct impact on arsenic releases specifically is not explicitly detailed. However, by encouraging practices that enhance the environmental and health safety of biosolid management, the approach contributes to the overall reduction of harmful substance releases, including potentially arsenic, into the environment​​.

4.4.4 CCME Guidance Document for the Beneficial Use of Municipal Biosolids, Municipal Sludge, and Treated Septage (2012)

The Guidance for the Beneficial Use of Municipal Biosolids, Municipal Sludge and Treated Septage is a comprehensive guide developed by the CCME in 2012, focusing on the environmentally beneficial and sustainable management of wastewater residuals. The document is aimed at regulators and waste generators, providing them with the necessary information to manage municipal biosolids, sludge, and treated septage effectively. Municipal biosolids, municipal sludge, and treated septage are all by-products of sewage treatment processes but differ in their treatment stages and applications. Municipal biosolids are derived from sewage that has been treated extensively to reduce pathogens and pollutants, making them safe for use as a nutrient-rich fertilizer. Municipal sludge is a semi-solid by-product from the initial wastewater treatment stages, requiring further treatment to become biosolids. Treated septage comes from septic systems, undergoing processing to remove contaminants before it can be safely disposed of or used. Each type requires careful handling to protect public health and the environment. The primary goal of the guideline is to ensure that these materials are handled in a way that benefits the environment while adhering to regulatory standards and practices​​​​.

The beneficial use of these materials involves applying them to land or using them in energy generation under specific conditions that ensure environmental protection. This approach supports nutrient recycling and organic matter addition to soils but requires careful management to prevent the leaching of arsenic and other contaminants into water sources or their release into the atmosphere. The document is comprehensive, covering all aspects of beneficial use, from planning and policy development to operational management and stakeholder consultation, emphasizing the importance of ongoing research and adherence to evolving scientific and technological standards​​​​.

While the guidance document does not address arsenic releases directly, its focus on the beneficial use and sound management of municipal biosolids and sludge could indirectly impact the handling of arsenic and other trace elements. By promoting best management practices for land application and energy generation from these residuals, the guidance ensures that any potential contaminants, including arsenic, are managed responsibly. This management minimizes the risk of environmental and human health impacts through the controlled use and processing of biosolids and sludge, which may contain trace elements like arsenic​​.

Solid waste

4.4.5 CCME Guidelines for Compost Quality (2005)

Published by the CCME, the guidelines are an updated version of 1996 guidelines. Its primary aim is to establish national standards for compost quality in Canada to ensure the safe use of compost products in agriculture, landscaping, horticulture, and other industries.

Arsenic can enter compost through various sources, including contaminated feedstock like food scraps, garden waste, and agricultural residues from areas with arsenic in the soil or water. Additionally, using water contaminated with arsenic during the composting process can introduce this element. Legacy arsenic from pesticides and herbicides previously used on plants can also contribute, as well as biosolids and manures from industries that use arsenic-based feed additives.

The guidelines were developed in collaboration with other regulatory bodies, such as the Bureau de normalisation du Québec (BNQ) and the CFIA, to provide a consistent framework while accommodating regional needs. The standards focus on four main criteria: foreign matter, maturity, pathogens, and trace elements, like arsenic, to ensure compost safety and minimize environmental and health risks.

The guidelines classify compost into two categories—Category A (unrestricted use) and Category B (restricted use)—based on the levels of contaminants. Regarding arsenic, the guidelines set maximum allowable concentrations in compost (13 mg/kg for Category A and 75 mg/kg for Category B), with cumulative additions to soil capped at 15 kg/ha. These limits help prevent toxic accumulation in soils, protecting plant, animal, and human health by minimizing exposure to potentially harmful trace elements like arsenic.

Hazardous waste

4.4.6 Cross-border Movement of Hazardous Waste and Hazardous Recyclable Material Regulations (2021)

The Cross-border Movement of Hazardous Waste and Hazardous Recyclable Material Regulations (XBR) regulate the transboundary movement of hazardous waste and hazardous recyclable materials into and out of Canada and between provinces or territories. They aim to ensure that hazardous waste and recyclable materials reach their intended destinations, thereby minimizing environmental risks​​.

The XBR directly impacts arsenic management by controlling the transboundary movements of waste that meet the definition of hazardous waste and hazardous recyclable material.  It ensures that arsenic-containing waste or material is managed in an environmentally sound manner, minimizing environmental risks. This is accomplished through stringent permit requirements for international movements, shipment tracking with movement documents, confirmation of disposal, and compliance with international agreements like the Basel Convention, which sets international requirements for transboundary movements of hazardous waste and other waste.

The XBR require detailed movement documents for each transboundary shipment, created using the Canadian Notification and Movement Tracking System (CNMTS). These documents, which include information about the shipper, carrier, and receiver, are crucial for tracking shipments and ensuring compliance with environmental standards. The regulations mandate that carriers be authorized to transport hazardous waste and materials, further reducing the risk of improper handling that could lead to environmental contamination​​. The instrument tracks the quantity of hazardous waste and hazardous recyclable material containing arsenic that was managed in an environmentally responsible manner, but not the quantity of the substance itself.

4.4.7 Findings and recommendations

Wastewater, municipal biosolids and waste management in Canada is governed by multiple jurisdictions, primarily at provincial, territorial, and municipal levels due to the division of federal and provincial responsibilities. Federal initiatives aim to support and harmonize these local programs to maintain consistent risk management standards across the country.

Given the shared responsibility in dealing with waste, the federal government is working with provinces and territories through the Canadian Council of Ministers of the Environment (CCME) to explore various solutions to minimize waste across the country.

According to the NPRI, wastewater and biosolids are the key representatives in this sector, while hazardous materials and waste are not considered significant contributors. An increase in arsenic releases from wastewater treatment facilities was observed from 2,613 kg in 2002 to 3,624 kg in 2022. However, the data reveals the increase in releases was accompanied by an increase in the number of facilities. This suggests that the amount of arsenic released per facility has remained relatively constant but there has been a need for more facilities which has resulted in the increase. The trend aligns with the increase in Canada's population from over 30 million to nearly 40 million people.

Figure 61: Releases of arsenic from sewage treatment facilities, waste treatment and disposal and municipal biosolids from 2000 to 2022

Facilities processing wastewater and biosolids do not generate arsenic but rather capture it from upstream sources. Therefore, it is crucial to continue monitoring arsenic levels in untreated wastewater to better understand upstream release patterns. To effectively identify and address the root causes, it is recommended to compare arsenic levels in wastewater from areas with varying industrial activity to determine whether non-industrial sources contribute significantly. If non-industrial sources are found to be a primary contributor, enhanced tracking and mitigation strategies for these sources should be developed.

4.5 Pesticides and fertilizers

The use of arsenic-containing pesticides and fertilizers in Canada was historically widespread but has been largely phased out over the last two decades mainly due to significant concerns with the toxic nature of arsenic and its potential environmental and health risks. Historically employed in various agricultural practices, as well as in wood treatment, these substances can contribute to soil and water contamination, posing long-term threats to ecosystems and human health. Arsenic-treated wood, which was historically used in products like fences and decks, can leach arsenic into surrounding soils, further exacerbating environmental exposure.

The PSL1 report on arsenic indicated that pesticides and wood preservatives were significant sources of arsenic releases. This raised concerns about the potential for arsenic to contaminate soil, water, and air, prompting the need for regulatory oversight to mitigate its impact.

4.5.1 Pest Control Products Act (2002)

The Pest Management Regulatory Agency (PMRA) under Health Canada developed a multifaceted approach to manage and mitigate arsenic releases from pesticides.

The regulatory framework established by the Pest Control Products Act (PCPA), serves as the cornerstone of this strategy, mandating rigorous pre-market and post-market evaluations of pesticides to ensure they meet contemporary health and environmental safety standards through regulating the sale and use of pesticides containing arsenic.

Historical use of arsenic in various products, including domestic and forestry applications, underwent re-evaluation, leading to the discontinuation of specific uses. Notably, the voluntary transition by industry away from chromated copper arsenate (CCA) treated lumber for non-industrial applications by 2003 marked a significant step towards reducing arsenic exposure.

Under the Toxic Substances Management Policy, ECCC in collaboration with the wood preservation industry and other stakeholders developed Technical Recommendation Documents (TRD) aimed to minimize arsenic releases. These documents provide guidance on facility design and operational practices to reduce environmental and worker exposure to wood preservative biocides, including arsenic.

The establishment of the Pest Control Products Sales Information Reporting Regulations by HC in 2006 enhanced the ability to monitor and assess the impact of arsenic-containing pest control products. There has been a slight increase in pesticides sales from 2013 to 2017 with sales remaining stable since then but fluctuating slightly year to year.

The ongoing evaluation of pesticides containing arsenic and continuous oversight of sales and use patterns demonstrates the dynamic regulatory landscape aimed at minimizing arsenic's environmental footprint. The PMRA continues to re-evaluate arsenic-containing pest control products to ensure compliance with the latest scientific standards and international guidelines, potentially leading to further restrictions or modifications in use.

4.5.2 Fertilizers Act and Regulations (1985)

The CFIA oversees the enforcement of these regulations developed under the authority of the Minister of Agriculture and Agri-Food, ensuring compliance through inspections and monitoring. The CFIA's mandate covers the safety of fertilizers and supplements, ensuring they do not pose risks to humans, animals, plants, or the environment​​. Legislation for fertilizers has been in place since around 1867. Most recently, the Fertilizers Act and Regulations were amended in 2020 as part of a modernization exercise to address deficiencies identified during a review of the regulations initiated in 2011. The amendments were established through a recommendation by both the Minister of Agriculture and Agri-Food and the Minister of Health.

The regulations specify standards that fertilizers or supplements must meet, such as not containing substances that would leave harmful residues in plants, not containing proteins derived from specified risk materials at levels that would be toxic and ensuring that nutrients are not present at toxic levels. There are also detailed requirements for the labeling and guaranteed analysis of fertilizers and supplements, including information about active ingredients and their concentrations​​.

These regulations indirectly impact arsenic releases by setting safety standards for fertilizers and supplements, including those derived from waste products such as biosolids, compost, wood ash and others, which could contain heavy metals like arsenic. By regulating the content and use of these products, the regulations help mitigate the potential for arsenic and other heavy metals to pollute the soil and water, thus impacting agriculture and the environment​​.

4.5.3 Findings and recommendations

The risk posed by the use of arsenic-containing pesticides has been controlled through collaborative actions between industry and governmental action. Although technical recommendation documents and enhanced sales information reporting have improved monitoring and mitigation of arsenic releases, it is important to continue re-evaluating arsenic-containing pesticides to ensure the ongoing effectiveness of control measures and be vigilant of emerging sources. Similarly, it is important to continue the monitoring of contaminant levels within fertilizers and continue promoting the use of safer pest control alternatives.

4.6 Contaminated sites, including legacy mines

The PSL1 report on arsenic also indicated that legacy mines were significant sources of arsenic releases. Legacy mining operations in Canada have resulted in numerous contaminated sites containing hazardous substances, including heavy metals such as arsenic.

The division of authority for managing contaminated sites in Canada is primarily based on jurisdictional ownership and the source of the contamination. Most contaminated sites fall under provincial or territorial jurisdiction, as they are located on non-federal lands. Provinces and territories regulate these sites through local laws governing environmental protection, mining, and land use, ensuring remediation is conducted according to regional standards. Municipal governments also play a role in managing urban and industrial sites, working under provincial oversight to address contamination effectively within their jurisdictions.

The federal government is responsible for contaminated sites located on federally owned lands, such as military bases, airports, Indigenous reserves, and federal facilities. The federal government oversees these sites through initiatives like the Federal Contaminated Sites Action Plan (FCSAP), which provides funding and guidance for the assessment and remediation of federal sites. Federal authority also extends to addressing transboundary pollution and ensuring compliance with international environmental agreements.

The federal government has also taken responsibility for a limited number of highly contaminated sites, such as Giant Mine and Sydney Tar Ponds. Giant Mine in Yellowknife, Northwest Territories, operating from 1948 to 2004, produced significant quantities of gold but also generated over 237,000 tonnes of arsenic trioxide dust, a highly toxic byproduct. The site's contamination has resulted in substantial risks to the environment and human health and has required extensive and ongoing remediation efforts.

4.6.1 The Federal Contaminated Sites Action Plan (2005)

The Federal Contaminated Sites Action Plan (FCSAP) was established with the goal of reducing environmental and human health risks associated with federal contaminated sites, while managing the federal financial liabilities they pose. The Federal Contaminated Sites Inventory currently contains over 7500 sites with contamination related to metals, metalloids and organometallic substances, including 39 sites that list arsenic as a direct contaminant currently in the process of remediation.

FCSAP operates under a policy framework designed to prioritize contaminated sites based on the severity of their environmental and human health risks. This approach ensures that resources are efficiently allocated to the sites that require the most urgent attention. Since its inception, FCSAP has made significant progress: assessment activities have been conducted at 10,960 sites, 7,700 site assessments have been completed, and remediation activities have been undertaken at 2,200 sites across Canada, with 1,040 sites fully remediated. Additionally, care and maintenance work are ongoing at various sites to maintain necessary systems and prevent increased reclamation and closure costs.

The program works with multiple stakeholders, including federal custodians, environmental consultants, contractors, and Indigenous communities. This partnership ensures a comprehensive management strategy for contaminated sites, addressing the needs of all parties involved and particularly focusing on those sites that impact Indigenous people living on reserves or in Northern communities.

4.6.2 Findings and recommendations

The area of contaminated sites is a major concern due to the large number of legacy sites in Canada. This concern is magnified by the significant increase in on-site disposals of arsenic at currently operating industrial sites, which have risen from under 10 million kgs in 2005 to over 60 million kgs per year, mainly impacted by the mining sector. The cumulative amount of arsenic and other hazardous materials disposed of at these sites is substantial, and when facilities cease operations, these contaminants will pose even greater environmental and financial risks unless the sites are properly closed and remediated.  Prioritizing high-risk sites, strengthening partnerships with Indigenous communities and other stakeholders, implementing long-term monitoring plans, and investing in innovative remediation technologies are critical to effectively managing both current and future contaminated sites. Responsibility for this task is shared among federal, provincial/territorial governments, and industry, depending on the site's specifics and regulatory framework.

4.7 Pulp and paper

The pulp and paper sector, although not specifically mentioned in the PSL1, releases levels of arsenic similar to the levels identified in the waste and municipal biosolids sector, according to NPRI data. The pulp and paper sector was therefore added to this analysis. The sector is integral to the global manufacturing landscape, primarily focused on producing pulp, paper, paperboard, and various paper products from wood fibers and recycled materials. This industry employs several critical processes and technologies. Pulping, the core process, is either mechanical, where wood chips are physically ground into fibers, or chemical, most commonly through the Kraft process, which uses chemicals like sodium hydroxide and sodium sulfide to dissolve lignin and separate fibers. Bleaching follows, especially for products requiring high brightness; historically this involved chlorine for chemical pulp such as Kraft pulp, but modern practices favor chlorine dioxide to reduce environmental impact.  Mechanical pulps typically are bleached (brightened) using sodium hydrosulphite, hydrogen peroxide, or a combination of these brightening agents.

Bleached or unbleached pulp is then formed into paper or paperboard in the papermaking process, where water is removed, and the material is dried and rolled. Throughout these stages, various chemicals are used and released, including sulfur compounds from the pulping process and potentially chlorine-related compounds from bleaching, though modern techniques have significantly mitigated these releases.

Pulp and paper mill operations often generate their own energy to power their operations and biomass combustion is widely used to meet these energy needs.

Regarding metal emissions, these are not typically primary concerns in main pulp and paper processes. However, trace metals like arsenic can be present in biomass used for energy generation, especially if previously treated with preservatives, and may be released during combustion processes in boilers used to generate energy for the mills. Additionally, any chemicals used in pulping and bleaching may contain trace metal impurities, which could become part of the releases, mainly to water.

4.7.1 Pulp and Paper Effluent Regulations (1992)

The Pulp and Paper Effluent Regulations were first developed under the Fisheries Act in 1971 to manage threats to fish, fish habitat, and to human health from fish consumption. They limit the deposit of harmful substances into fish-bearing waters by pulp and paper mills. The regulations were designed to encourage mills to modify their processes in order to improve water quality. The 1971 regulations differentiated between new, expanded, altered and existing mills. New, expanded and/or altered mills were subject to the prescribed limits. For mills already in operation, the limits served as non-enforceable guidelines. In 1992, the 1971 regulations were updated to expand coverage to all mills, and to drive further effluent quality improvements based on standards achievable using secondary wastewater treatment. After a transition period, all mills became subject to the regulations in 1996. The regulatory standards have remained unchanged since.

The regulations set limits for the maximum quantities of matter exerting biochemical oxygen demand (which consumes oxygen dissolved in water) and suspended solids that can be deposited from pulp and paper mills under prescribed conditions. The regulations do not allow the deposit of any effluent that is acutely lethal to fish. The PPER also contain requirements for mills to conduct environmental effects monitoring to identify effects of the effluent on fish, fish habitat and the use of fisheries resources. Facilities are required to submit monthly effluent reports that include the biochemical oxygen demand of matter in effluent, the quantity of suspended solids in effluent, effluent volume and summary results of rainbow trout acute lethality tests and Daphnia magna monitoring tests.

While the PPER primarily focus on the quality of water and the protection of aquatic life, they indirectly impact arsenic releases through the comprehensive management of pollutants and the requirement for environmental monitoring. However, the direct impact of PPER on arsenic releases specifically is less clear, as the regulations do not require the collection of data on this substance​​.

According to the 2022 Pulp and Paper Effluent Regulations Annual Report published by ECCC, the industry has maintained high compliance rates with the existing effluent regulations. The report indicates that 99% of tests for suspended solids and biochemical oxygen demand were within acceptable limits. Moreover, the report highlights a consistent effort across the industry to minimize the environmental impacts of effluent discharge, which includes both chemical and physical pollutants, into water bodies. However, the report also notes that more than half of the sublethal toxicity tests conducted on final mill effluents indicated impacts on growth and reproduction inhibition in laboratory test species. This means that while the effluent may not be immediately lethal to aquatic life, it can still adversely affect organisms over time by hindering their growth and reproductive capabilities. Currently, modernization of the PPER is being considered which would expand requirements for monitoring additional substances, including arsenic, in effluent and receiving waters.

4.7.2 Code of Practice for the Management of Air Releases from Pulp and Paper Mills (2018)

The Code of Practice for the Management of Air Releases from Pulp and Paper Mills in Canada, effective since July 2018, sets forth recommendations for best practices to reduce releases of air pollutants including total particulate matter from facilities within the pulp and paper sector. This initiative underscores the industry's operational activities and the associated environmental concerns, particularly regarding atmospheric releases. Facilities are encouraged to implement these best practices to mitigate air releases and to report their emission levels. While the code directly targets TPM releases, the implementation of its recommendations indirectly impacts the releases of other pollutants, potentially including arsenic, by promoting cleaner operational practices and technological improvements within the industry. By reducing the overall pollutant releases, the code contributes to improving air quality and reducing the environmental footprint of the pulp and paper sector​​​​​​.

For facilities within the sector, adherence to the code involves implementing the outlined best practices, informing the Minister of the Environment of their intention to follow the code, and submitting emission assessment reports. These actions are designed to ensure that the facilities operate within the recommended emission limits, thereby fostering a healthier environment and community​​.

4.7.3 Findings and recommendations

Arsenic releases from the pulp and paper sector have decreased from 3,167 kg in 2002 to 2,188 kg in 2022, a reduction of 31%. While emissions of trace metals like arsenic are not primary concerns, they can occur from the inadvertent combustion of treated wood for power generation. 

Figure 62: Releases of arsenic from pulp and paper from 2000 to 2022

The PPER reporting shows that compliance rates with the regulatory limits are generally high. However, sublethal toxicity tests indicate effluents can still impact aquatic species' growth and reproduction and so there may be a need for more stringent limits.

The 2018 Code of Practice for the Management of Air Releases from Pulp and Paper Mills focuses on reducing air pollutants, including particulate matter. These actions could indirectly impact arsenic emissions, although the extent of this impact remains uncertain.

Continued and strengthened efforts to include trace metals like arsenic in monitoring protocols for both water and air releases from pulp and paper mills could help identify and address potential contamination sources more effectively. Expanding environmental effects monitoring requirements for arsenic from this sector, for example through the proposed modernization plans for the PPER, would provide more focused data to guide regulatory updates and contribute to future PME reporting.

4.8 Domestic and international agreements and collaboration

4.8.1 Multisector-Water: Canada-US Great Lakes Water Quality Agreement (1972)

The Canada-United States Great Lakes Water Quality Agreement (GLWQA) is a pivotal bilateral commitment aimed at restoring and protecting the Great Lakes' water quality. It was initially signed in 1972 and subsequently amended in 1978, 1987, and most recently in 2012, when both countries agreed to identifying and taking action on chemicals of mutual concern. As part of this initiative, the agreement supports the reduction of pollutants such as mercury and lead which often are emitted from similar sources as arsenic. Through the implementation of controls and remediation efforts aimed at chemicals of mutual concern, the agreement contributes to a broader reduction in the introduction and circulation of other harmful pollutants, including arsenic, into the Great Lakes ecosystem​​​​​.  The GLWQA generates progress reports to track advancements in meeting water quality objectives, assessing the effectiveness of implemented measures, and identifying ongoing challenges. These reports provide updates on efforts to control pollutants, restore degraded areas, and protect aquatic ecosystems. The latest progress reports are available on Binational.net, where stakeholders can access data, initiatives, and collaborative actions undertaken by both nations to uphold the integrity of the Great Lakes.

Key elements of the GLWQA involve commitments to action that are both immediate and long-term, enhancing accountability and transparency in environmental management practices. The agreement's modernized approach reflects current knowledge and emphasizes prevention, aiming to address not only existing environmental challenges but also to anticipate and mitigate future issues. It includes a series of annexes that cover a wide range of topics, from aquatic invasive species and habitat and species conservation to climate change impacts and pollution from chemicals of mutual concern​​​​.

Through the GLWQA, Canada and the US, along with other levels of government, Indigenous Peoples, non-governmental entities, and the public, are working together to ensure the Great Lakes remain a vital resource for safe, high-quality drinking water, recreation, economic activities, and wildlife habitat. The agreement's comprehensive and action-oriented framework demonstrates a binational commitment to environmental stewardship, showcasing the Great Lakes as a global model for freshwater protection and sustainability​​​​.

4.8.2 Canada Ontario Water Quality Agreement (1994)

The Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health (COA) is a collaborative effort between the Government of Canada and the Province of Ontario to address environmental challenges in the Great Lakes basin. The agreement is the mechanism by which Canada delivers on its obligations under the GLWQA discussed above.

While the COA primarily focuses on water quality and ecosystem health in the Great Lakes, its initiatives indirectly influence arsenic releases and contamination in several ways. Although, similar to the GLWQA, the COA does not directly specify measures for arsenic, the agreement's efforts to manage and reduce pollutants can also mitigate the introduction and spread of arsenic into the aquatic ecosystem. The reduction of harmful chemicals and the improvement of wastewater systems, as outlined in the agreement, contribute to minimizing the potential for arsenic contamination.

The COA is action-oriented, with commitments being time-bound and expected to be achieved within the span of the agreement. Progress is monitored and reported publicly through mechanisms like the Progress Report of the Parties and the State of the Great Lakes Report, which assess the health of the lakes against science-based indicators of ecosystem health. These reports are issued triennially under the GLWQA, providing transparency and accountability in the efforts to improve the Great Lakes' water quality and ecosystem health​​.

Furthermore, the agreement facilitates funding for projects aimed at reducing pollutants, such as phosphorus, that can have a broad impact on overall water quality and indirectly affect the bioavailability of arsenic and other toxic substances. Initiatives under the COA, like the Great Lakes Protection Initiative, work towards addressing significant threats to the water quality and ecosystem health of the Great Lakes, including reducing releases of harmful chemicals and engaging in actions to restore water quality in areas of concern.

4.8.3 Accelerated Reduction/Elimination of Toxics Program (1992 to 1994)

The Accelerated Reduction/Elimination of Toxics (ARET) program, initiated in the early 1990s by industry representatives and environmental non-government organizations and supported by ECCC, was a voluntary effort aimed at reducing or eliminating releases of harmful substances. This initiative brought together stakeholders from various sectors, including industry, provincial and federal governments, health and environmental groups, and labor organizations, to focus on a list of 117 substances, including arsenic. These substances were identified for their toxicity, persistence, and bioaccumulation potential. The program set ambitious goals to reduce releases of persistent, bioaccumulative, and toxic substances by 90% and other toxic substances by 50%, with a long-term aim of virtually eliminating releases of 30 specific substances​​.

The program aimed to significantly lower the release of substances into the environment, including arsenic, by encouraging voluntary actions which would reduce its potential harm to ecosystems and human health. Indirectly, the program influenced broader environmental management and pollution prevention practices within participating organizations.

In April 2000, ECCC undertook an evaluation of ARET to help the Department make a decision about its continued support and participation in the initiative.

The main focus of the evaluation was on assessing the effectiveness of the initiative, that is the extent to which participation in ARET could have been considered as being responsible for the reduction/elimination of emissions of toxic substances and in meeting reduction targets.

The main conclusion of the evaluation report was that ARET challenge targets were met, and in most cases exceeded, except for substances such as arsenic that are persistent and bioaccumulative. However, the evaluation also found that the ARET initiative was not one of the main factors in motivating industry to reduce releases of toxic substances. Other factors such as regulations, modernization, and business decisions played a more important role.

4.8.4 Findings and recommendations

The impact of domestic and international agreements on arsenic emissions is largely indirect but still significant due to co-benefits resulting from the reduction of other pollutants. Initiatives like the COA and the GLWQA primarily focus on improving water quality and reducing pollutants in the Great Lakes. While arsenic is not specifically targeted, these agreements contribute to its reduction by promoting the control of various harmful chemicals and improving wastewater systems, which can help reduce arsenic deposition and contamination in aquatic ecosystems. However, voluntary programs like ARET have proven less effective in driving substantial reductions in arsenic emissions.

International and intergovernmental collaboration is essential for addressing cross-border arsenic risks, as Canada continues to be affected by emissions originating in the U.S., particularly in regions close to the Great Lakes. For truly comprehensive arsenic management, coordinated multilateral action is required to address sources across globally competitive sectors, ensuring that emission control measures are effective and economically feasible.

4.9 Conclusions on risk management

Since the early 1990s, efforts to manage environmental risks have contributed to notable reductions in arsenic emissions from key sources identified in the PSL assessment, suggesting progress toward risk management goals. However, pinpointing whether these decreases stem directly from federal regulations, pollution controls, national and international partnerships, or broader industry trends proves challenging. This ambiguity arises due to the complex interplay of various regulatory measures, sector-specific factors, and economic variables that impact arsenic emissions.

In 2022, approximately half of the arsenic released in Canada was managed by seven federal regulations, with two explicitly targeting its release: the Metal and Diamond Mining Effluent Regulations under the Fisheries Act and the Pest Control Products Act, and one currently considering its inclusion: the Pulp and Paper Effluent Regulations under the Fisheries Act. The remaining four manage arsenic as part of broader controls on metals and particulate emissions: the Reduction of Carbon Dioxide Emissions from Coal-fired Generation of Electricity Regulations, the Wastewater Systems Effluent Regulations, the Cross-border Movement of Hazardous Waste and Hazardous Recyclable Material Regulations, and the Fertilizers Act and Fertilizers Regulations. The other half is managed as part of broader non-regulatory measures targeting metals and particulate emissions. These measures returned positive results from the base metal smelting and refining sector, the largest industrial source of arsenic emissions, reducing emissions of arsenic from more than 50,000 kgs in 2005 to less than 15,000 kgs in 2023 via a pollution prevention planning notice (2006 to 2018) and environmental performance agreements (2018 to 2025).

Assessing the cumulative effectiveness of multi-sectoral actions remains complex, given the inconsistencies in reporting across industries and the difficulty of attributing specific outcomes to individual regulatory or voluntary actions. Though preventive actions are assumed to discourage practices that would elevate arsenic emissions, this deterrence effect is largely intangible and difficult to quantify. Nevertheless, the overall impact of the various risk management measures on arsenic releases to the environment is significant. National arsenic releases have declined from over 200,000 kg in the early 2000s to under 50,000 kg in recent years, reflecting substantial progress.

5. Risk communication

As health risk communication will be evaluated under the human health component of the PME report, environmental risk communication mostly includes informing Canadians about the risks of chemicals to the environment and is essential for transparent government operations. ECCC actively communicates these risks through online webpages, publications, and news releases. A primary resource is the toxic substance webpage for inorganic arsenic compounds, which offers an overview of arsenic, its environmental sources, and links to risk assessment documents and risk management tools.  

Information on past and present risk management and assessment activities under the Chemicals Management Plan is posted on the Chemicals Management Plan webpage that is managed jointly by ECCC and HC. Additionally, work under the Chemicals Management Plan is communicated to stakeholders who have registered for email updates. These mail-outs are public notifications of publications, opening of comment periods or other relevant information.

Data collected by ECCC’s pollutant inventory and monitoring programs are made publicly available online on Canada’s Open Data Portal. These data are used in annual reporting of the Canadian Environmental Sustainability Indicators as part of commitments under the Federal Sustainable Development Strategy reporting. CESI indicators for releases of harmful substances to water and emissions of harmful substances to air include information on facility-based releases of arsenic. Additionally, the National Pollutant Release Inventory (NPRI) Substance Overview Storyboard on Arsenic provides accessible data and insights on arsenic releases.

All of this information is also reported in the annual CEPA reports along with information on the implementation of risk management actions. While ECCC has not released social media posts on arsenic, HC has made 7 posts on arsenic since 2012.

5.1 Findings and recommendations

The accessibility of information on arsenic in the environment varies significantly depending on the search terms used. While information from HC about arsenic can be found using keywords such as "arsenic risk” or “arsenic in the environment", ECCC websites require more targeted searches such as “inorganic arsenic compounds”. This indicates a potential barrier to information accessibility for the general public.

The readability of the webpages was also assessed to estimate the education level required to understand the content. On average, the material appears suited for readers with a higher education. While this level of complexity may be appropriate for professionals and academics in environmental science and policy, simplifying the language could improve accessibility and help ensure that a broader public audience can understand the risks associated with chemicals in the environment.

To improve public access to information on arsenic, the following approaches may be explored:

• Optimizing ECCC managed webpages aimed at the general public to ensure that references to toxic chemicals appear under broader, more general search terms
• Developing additional risk communication tools that may communicate risk to a wider audience, for example tools that are more visually appealing and interactive
• Simplifying the content where possible to make information more approachable for the average reader
• Launching targeted public awareness campaigns for toxic substances to help disseminate key information about contaminants such as arsenic in a clear and engaging manner

6. Evaluation of the effectiveness of risk management

Since no specific risk management strategy was created for arsenic, this evaluation proposed both an environmental objective and a risk management objective for arsenic.  The goal of the environmental objective is to ensure anthropogenic releases of inorganic arsenic compounds do not exceed levels expected to cause adverse environmental effects, considering natural background concentrations. The risk management objective is to achieve the lowest levels of anthropogenic releases of inorganic arsenic compounds that are technically and economically feasible, taking into consideration socioeconomic factors and focusing on actions taken since the 1993 assessment. Together, these objectives aim to assess how well the overall approach of the federal government has progressed in reducing Canadian anthropogenic releases of inorganic arsenic compounds and in protecting the Canadian environment from harmful effects.

To assist in this evaluation, additional questions were proposed in section 1.3 which can now be answered using the information presented in the previous sections of this report.  This report concludes the following:

Are environmental arsenic levels of concern and/or do they exceed risk-based guidelines?

Overall, arsenic levels across most regions are well-managed and not a widespread concern. Air quality monitoring shows that arsenic concentrations generally remain within provincial guidelines, even in industrial and densely populated areas. Similarly, water monitoring reveals that arsenic levels are stable or decreasing in most regions, with most sites falling below the guidelines for protecting aquatic life. In wildlife, arsenic levels align with natural background concentrations, and trends indicate stability or decline in most species. Nevertheless, there have been isolated instances where arsenic levels in fish exceeded the guideline limits. However, there are no established risk-based guidelines for wildlife, indicating a gap in understanding the full impact on ecological systems. Although most guidelines have not been significantly exceeded, further research is required to determine appropriate risk levels for wildlife and ecosystem health. While some localized areas require attention, the overall situation suggests positive progress in controlling arsenic levels.

Are there specific sites with elevated arsenic concentrations?

Although higher concentrations of arsenic have been detected in the air at certain specific sites, they generally remain below established guidelines. Elevated arsenic levels are more pronounced in aquatic environments, particularly in sediments near urban areas, where it tends to accumulate over time. Notable locations include areas of Lake Ontario, Lake Huron, Montreal, Lake Banook, and the Cornwallis River. These regions are of particular concern due to the ongoing accumulation of arsenic in sediments.

Contaminated sites such as legacy mines, which are defined by their elevated arsenic concentrations, have been identified in various areas. While there are active measures being taken to manage some of these contaminated sites, they remain among the most significant environmental concerns due to the long-term risks they pose to ecosystems and potentially to human health.

Operating mining sites contain elevated levels of arsenic due to on-site disposals. While these disposals have not been identified as an immediate environmental risk, as they are expected to be properly managed, the substantial quantities of arsenic present may pose a significant threat in the event of an unforeseen cessation of operations. Should these sites become unmanaged, the accumulated arsenic levels will be considerably higher than those of older mines, leading to greater environmental risks.

Considering the changes in arsenic levels over time, are additional protective actions required?

Overall, arsenic releases from key industrial sectors are decreasing or stabilizing including those included in the PSL1 Arsenic Report. This is supported by current data from the National Pollutant Release Inventory. Although these results are positive, some additional actions might be needed to ensure the trend continues.

On-site arsenic disposals, primarily from the mining sector, have increased significantly. While this trend does not present an immediate concern, planning for site closure and remediation is important to ensure that disposals are properly managed and secured for long term disposals in order to minimize risks, especially if companies cease operations unexpectedly. As seen with legacy mines, such events can leave behind a significant financial burden and environmental impacts.

Further environmental monitoring could be beneficial to evaluate the impact of recent management actions in certain sectors.  Newly implemented regulations in the metal and mineral production sector require more time to demonstrate their full impact. Continued monitoring is crucial to identify potential issues, particularly upstream sources of wastewater discharge, which may contribute to localized increases in arsenic and where there could be an opportunity to take additional action.

The electricity sector, particularly coal-fired power plants, has historically been a source of arsenic emissions through combustion byproducts, but advancements in emission controls and the switch to cleaner feedstocks have led to reductions. Continued regulatory oversight will help sustain progress across these industries.

In the area of waste and wastewater management, it is recommended to conduct thorough studies to identify the upstream sources of pollution. These studies should assess whether the contamination stems from natural geographic factors, residential or commercial sources, or industrial activities. Understanding these origins will enable the development of more targeted and effective pollution control strategies.

Continuing to implement monitoring protocols to include trace metals like arsenic in both water and air releases from pulp and paper mills could help identify and address potential contamination sources more effectively. In addition, expanding environmental effects monitoring for arsenic in this sector is recommended as it would provide more focused data to guide regulatory updates and future PME reporting.

Are companies implementing best practices to their fullest extent?

Overall, Canadian companies are making significant progress in implementing best practices, though there is room for improvement.

In the mining sector, results from actions such as the Metal and Diamond Mining Effluent Regulations indicate that most companies are meeting limits for harmful substances, including arsenic. To meet these requirements companies often adopt best practices. The sector achieved a 54% reduction in arsenic emissions between 2005 and 2018. However, occasional exceedances in effluent quality were observed, including for arsenic levels.

In the base metal smelting and refining sector, voluntary codes of practice, like the Environmental Code of Practice for Base Metal Smelters and Refineries, have seen widespread adoption with 4 facilities having fully implemented an average of 92% of their applicable recommendations while the other 4 facilities have implemented 100% of their applicable recommendations.

In the pulp and paper sector, data collected on submissions from regulated pulp and paper mills and off-site treatment facilities indicate that the number of toxicity tests passed remains at an average of 97% since the year 2000, indicating high levels of implementation.

Is current monitoring data sufficient to evaluate environmental outcomes?

The available arsenic monitoring data, while robust in some areas, has limitations that hinder a full evaluation of environmental outcomes. The gaps in regional coverage, variability in monitoring focus across different media, and the complexity of arsenic behavior in the environment make it difficult to draw definitive conclusions.

Air monitoring programs like GAPS and GLB primarily focus on Ontario, with limited data from other regions, while NAPS provides broader coverage but lacks PM speciation monitoring for arsenic in most provinces. Nevertheless, provinces conduct their own monitoring and often make data publicly available, helping to complement federal programs and improve overall coverage.

Programs that monitor aquatic environments have varied levels of data. While sediment cores provide useful historical data, coverage is mostly focused on the Great Lakes-St. Lawrence River basin with limited collections from the Atlantic provinces and British Columbia. The lack of data from other geographic areas limits the ability to fully understand the extent and sources of sediment-bound arsenic, potentially overlooking localized contamination and its ecological impacts. In contrast, the extent of monitoring of arsenic in surface waters and fish is robust and covers a wide geographical area of the country.

The geographic extent of arsenic monitoring in wildlife spans various regions across Canada, with significant focus on Arctic areas (for example, Yukon, Northwest Territories), industrially impacted regions (for example, Yellowknife), and marine environments (for example, Nunavut, Newfoundland and Labrador). Monitoring also occurs in agricultural and forested areas such as British Columbia and Alberta, as well as freshwater environments like the Great Lakes and St. Lawrence River.

Monitoring programs for arsenic in the environment are prioritized based on areas with known or potential contamination risks, such as regions affected by industrial activities, mining, agriculture, or historical pesticide use. These regions are monitored due to the higher likelihood of arsenic exposure, allowing researchers to focus on areas where environmental and human health risks are most significant. Additionally, sensitive ecosystems, such as Arctic regions, are often prioritized because of their vulnerability to bioaccumulation of contaminants. This targeted approach ensures that resources are allocated efficiently by concentrating efforts where the risks are highest, providing valuable insights into areas of greatest concern.

This evaluation of Canada's approach to managing inorganic arsenic compounds shows that the proposed environmental objective had been mostly met. Despite no specific risk management strategy, the goal of reducing anthropogenic releases of arsenic to levels below those that cause adverse environmental effects has seen progress. Nevertheless, the challenge remains in identifying sites where arsenic sources converge, as it is not logistically or economically feasible to monitor every location across the vast Canadian landscape. Many remote or less populated regions may harbour contamination that goes undetected without widespread monitoring. Thus, while targeted programs are practical, they may miss emerging or localized arsenic pollution outside known high-risk areas, making it difficult to capture a full picture of exposure across the entire country. For example, arsenic from historical mining operations in northern Ontario has been transported downstream into connected lakes and rivers, leading to elevated sediment concentrations.

With respect to the risk management objective for arsenic, which aims to achieve the lowest level of anthropogenic releases of inorganic arsenic compounds that are technically and economically feasible while considering socioeconomic factors, progress continues to be made. Improvements have been observed, particularly in sectors like metal and mineral production, where emissions have been substantially reduced through the adoption of more efficient pollution control technologies. However, it is crucial to remain vigilant and proactive, ensuring that progress is sustained, and new challenges are addressed effectively to uphold long-term environmental and public health goals.

7. Moving forward

The data collected on arsenic offers a solid understanding of the impact of arsenic in the environment and the success and progression of risk management measures to address it, helping shed light into other actions that could be taken to continue mitigating its risk.

While the following recommendations primarily target actions required for managing arsenic, it is important to recognize arsenic as just one of many substances and priorities overseen by the federal government.  Therefore, these recommendations should be evaluated and implemented alongside other relevant programs to maximize the effectiveness of interventions for arsenic and other substances of concern.

In general, it is important to continue monitoring arsenic impacts and control its releases to the environment from human activities. Monitoring is crucial, especially as population growth drives higher demand for services and products from all industrial sectors, potentially leading to increased emissions. There is also potential for enhancement in the knowledge base, particularly through the gathering of data from industrial and residential sources beyond the scope of NPRI reporting, to help improve estimates in government inventories of emissions and releases. This approach could identify localized arsenic issues, ensuring a more comprehensive understanding of its potential environmental impact. Inventory programs such as the APEI could be expanded to include arsenic to estimate releases from non-industrial sources. In addition, programs such as PAWPIT could be expanded to other geographical areas to help close the data gap on surface water runoff.

7.1 Industrial sectors

It is important to maintain the collection of data through reporting programs such as the NPRI. Additionally, it would be beneficial to broaden data collection efforts, when possible, to encompass industrial facilities that are currently outside the scope of NPRI requirements as this could help identify emerging sources and provide a better general analysis. It is also recommended to optimize data collection methods to obtain better quality of data and ensure continuity from year to year and through updates to reporting.

Mining

According to NPRI data, mining disposals have increased significantly over time, likely as a result of increasing production levels. While these disposals are currently managed, their scale relative to production presents potential risks. Without diligent oversight, there is a possibility that such waste could contribute to the development of future legacy sites. To mitigate this, it is essential that disposal practices follow sustainable methods, ensuring that waste materials are securely contained and treated to prevent future contamination. Monitoring and enforcement are key to ensure proper management of disposal which is critical to avoid leaving behind a legacy of pollution once mining operations cease.

Metal and mineral production

Given that the metal and mineral production sector is the primary contributor to arsenic releases, federal efforts to reduce emissions and releases are focusing on this sector. Within this sector, smelting and refining activities account for the largest share of arsenic releases. Targeted actions include PM emission targets and reporting requirements for metals, including arsenic, in air emissions and effluents.

Electricity and combustion

Continue the transition away from fossil fuels to alternative and renewable energy sources to maintain low arsenic releases. Ensure biomass feedstock consists of material free from added chemicals and contaminants.

Wastewater and biosolids

Possible sources of arsenic in wastewater and biosolids include the human diet, consumer products, regional geology and industrial discharges. Although encouraging the use of the most effective arsenic removal systems could help tackle the significant issue of arsenic in wastewater by lowering the rate at which arsenic is discharged, post processing, into water bodies, the main focus should be on identifying and addressing upstream sources. This would require a study considering the above-mentioned sources to identify the relative contribution of various upstream sources and, where possible, develop a strategy to address them.

Other sources

While no additional actions might be necessary in other sectors at the time, when resources allow it, conducting targeted studies of arsenic, possibly in conjunction with other metals, to identify emerging sources of contamination or localized issues is recommended, especially in sectors like pulp and paper.

7.2 Environmental media

Air

Continuing monitoring of arsenic concentrations in air is recommended especially in areas with high traffic and industrial activities. Additional research is required to determine specific sources of arsenic near traffic areas. The use of low-cost passive air samplers to expand the geographic scope of air monitoring for arsenic should be considered as resources allow, particularly in areas with limited historical data.

Continue promoting industry consideration of air quality guidelines to reduce arsenic releases, especially in urban and industrial areas, and maintain or enhance monitoring, as appropriate, to evaluate performance for applicable industrial sectors.

Increasing public awareness about the impact of forest fires on air quality and arsenic releases and the link between climate change and forest fires and encouraging preventive and mitigative actions is also recommended.

Sediments

Where resources allow it, consider expanding sediment monitoring in the Great Lakes and other affected regions to identify arsenic in other contaminated areas. This is recommended due to the significant increase in levels detected over various campaigns. It is also recommended to complete recurring monitoring in areas with significant pollution.

Surface waters

Continuing monitoring of arsenic concentrations in oceans, rivers, lakes, and precipitation, including other media around sites of concern to assess the effectiveness of existing actions.

Targeted monitoring is needed, particularly at sites where high concentrations of arsenic were found, or sites where concentrations exceeded guidelines (for example, Keg Lake in Nunavut, Moira Lake in Ontario, and Mitchell Brook in Nova Scotia).

Fish

Continuing monitoring of arsenic concentrations in fish, focusing on species-specific accumulation patterns and potential health impacts, mainly in areas where arsenic concentrations in fish have been found to be higher.

Biota

Continuing monitoring of arsenic exposure on wildlife, especially near contaminated sites like abandoned mines, is recommended to identify localized hotspots. Further investigation into the adverse effects of arsenic across different species is also advised as well as data on the chemical forms of arsenic and their rates of production and degradation in Canadian water, soil, sediment and biota, particularly in contaminated areas.

General recommendations

A follow-up evaluation of the effectiveness of risk management actions is recommended by 2035 to assess the implementation of any new measures, where warranted, and to collect additional performance measurement and environmental data. This data will be crucial for future evaluations and risk management efforts.

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9. Annex – overview of sources of data

9.1 Air - The Global Atmospheric Passive Sampling (GAPS) Program

The Global Atmospheric Passive Sampling (GAPS) Program, initiated in 2005 and expanded with the Megacities pilot project in 2018, aims to provide globally comparable data on persistent organic pollutants (POPs), emerging chemicals, and trace metals. Covering 60 core sites worldwide and 23 mega/major cities, including Toronto, GAPS has broadened its scope to assess the impact of arsenic releases on health and the environment.

The GAPS initiative produces crucial data on POPs and has recently advanced methods for detecting trace metals within the same polyurethane foam disk passive air samplers (PUF-PAS). The Megacities project, part of this initiative, focuses on urban centers like Toronto and has collected data on trace metals since 2018. This expansion complements the core program's efforts, which include a comprehensive year-long sampling at 41 sites in 2019, although analysis was only completed for samples from 33 sites. Future plans include quarterly sampling at all 60 sites biennially or triennially.

In a complementary initiative, in 2017 the Assessing Toxicity of Organics in Urban Source Sectors for Air (ATOUSSA) regional study was executed across six locations in the Greater Toronto Area in Ontario providing valuable information on arsenic releases as well.

9.2 Air - The Great Lakes Basin (GLB) Monitoring and Surveillance Program

The Great Lakes Basin (GLB) Monitoring and Surveillance Program has been monitoring POPs and other air pollutants around the Great Lakes since its establishment in the early 1990s. The GLB program measures arsenic in the air as part of the trace metals monitoring. The program has maintained consistent data collection methods over several decades, allowing for robust trend measurements.

Three primary sites in Ontario, Point Petre on the north shore of Lake Ontario, Burnt Island on Manitoulin Island in Lake Huron, and Egbert, located inland between the two other sites, have been at the forefront of this monitoring. Egbert, located approximately 70 km north of major populated and industrial areas, serves as a suburban monitoring point. Point Petre, on the other hand, offers a more rural perspective being situated about 100 km east. Burnt Island, the most remote of the three, is positioned roughly 400 km northwest.

Today, samples are only being collected at Point Petre.  This site is significant because it provides a unique dataset using consistent methods over several decades, enabling robust trend measurements over the long term.

9.3 Air - The National Air Pollution Surveillance (NAPS) Program

NAPS was established in 1969 to monitor and assess the quality of ambient air in Canadian neighbourhoods, mainly in urban areas. It is a joint program of the federal, provincial, territorial and some regional government partners. The primary purpose of the program is to support the development of Canada-wide air quality objectives for criteria air contaminants and subsequently to track progress towards achieving these objectives.

A variety of pollutants are monitored within NAPS, including ozone (O₃), oxides of nitrogen (NO/NO₂/NO_X), sulphur dioxide (SO₂), carbon monoxide (CO), fine and coarse particulate matter (PM_2.5 and PM_10-2.5), particle species, volatile organic compounds (VOCs), carbonyl compounds and semi-volatile organic compounds (SVOCs) including polycyclic aromatic hydrocarbons (PAHs) .

NAPS monitoring is conducted at over 200 sites, and as of 2023, the program includes 14 sites with PM_2.5 speciation nationwide. Most of these sites are located in major urban areas but some are in rural locations or in smaller communities with PM_2.5 impacts from local industrial sources.

As part of a comprehensive 2015 to 2016 near-road study, trace elements including arsenic were also monitored in particulate matter collected at three near-road monitoring stations established in the downtown area and near a busy highway in Toronto, and beside a major trucking route in Vancouver (Dabek-Zlotorzynska et al.  2019, Jeong et al.  2019, Celo et al.  2021). These sites are now included in the NAPS PM_2.5 speciation program.

The selection of sites was done in such a way as to meet the objective of producing air quality data representative of the major population centers of Canada along with measurements in rural areas impacted by regional transport or background sources (Canadian Council of Ministers of the Environment  2019, NAPS practical guide to monitoring and Quality Assurance/Quality Control, 2019). More information about the location of these sites and possible sources of air pollution can be found in a number of publications (Celo et al.  2010, Jeong et al.  2011, Phillips-Smith et al.  2017, Dabek-Zlotorzynska et al.  2019, Jeong et al.  2019, Jeong et al.  2020, Celo et al.  2021, Mamun et al.  2021).

Integrated sampling for fine particles (with diameter less than 2.5 µm, PM_2.5) and coarse particles (with diameter between 2.5 µm and 10 µm, PM_10-2.5) began in the NAPS network in 1984. In 2003, the NAPS PM_2.5 speciation program was initiated to expand upon existing PM monitoring activities to allow the accurate measurement of all the important components of PM_2.5 (Dabek-Zlotorzynska et al.  2011). As part of this program, analysis of trace elements in PM_2.5 by ICP-MS combined with microwave-assisted acid digestion was added. Implementing this sensitive method allowed for accurate and reliable measurements of the concentration of toxic elements, including arsenic, in air particulate matter at the NAPS PM_2.5 speciation sites (Celo et al.  2010). Measurement of water-soluble metals began in 2004 and acid digested metals measurements began in 2006. 

The NAPS monitoring protocol was also used to measure trace metals at seven sites in close proximity to oil sands processing activities for the years 2010 to 2017 (Mamun et al.  2021, Mamun et al.  2022). This study was part of the Enhanced Deposition Component of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring (JOSM) Program.

Note: Site types are defined as follows: General population exposure - sites located in an urban area where populations live, work, shop, play, and that are not classified as transportation or point sources; Point source–influenced - sites near (<10 km) a major stationary releases source located in an urban area; Transportation source–influenced - sites within 100 m of a major road or influenced by off-road vehicles and engines, rail, marine or aviation sources located in an urban area; Regional background - sites outside urban area; Urbanization descriptions are based on the following: Large urban area - large population center (population ≥100,000); Medium urban area - medium population center (population between 30,000 and 99,999); Small urban area - small population center (population between 1,000 and 29,999); Non-urban (rural) area - non-urban area (population <1,000).

9.4 Sediment - Great Lakes sediment monitoring

ECCC has played a pivotal role in sediment quality assessments across key Canadian water bodies, actively overseeing sediment quality evaluations for the St. Lawrence River since the early 2000s, and for the Great Lakes beginning in the early 2010s, collecting samples of metals such as arsenic and other substances. Historical foundations of this monitoring initiative are rooted in programs such as the St. Lawrence Action Plan (SLAP) and the Great Lakes Action Plan (GLAP). These early efforts provide valuable data on arsenic's spatial and temporal distribution, helping understand the context and pinpoint areas of high concentration.

The legacy of these projects is preserved in comprehensive databases. For instance, the national water quality database (NAQUA) has archived arsenic data from the Great Lakes starting in 1968. As a more recent undertaking, the CMP has enriched these databases by providing contemporary data on arsenic levels in sediments from the Atlantic and Pacific watersheds. While extensive monitoring has been conducted in the Great Lakes and the St. Lawrence River, other Canadian watersheds have had less frequent sediment quality assessments concerning arsenic. However, the 2008-initiated CMP program has aimed to address this gap. Through the CMP, sediment samples have been collected from various provinces between 2011 and 2014, thereby broadening the understanding of substances distribution in these regions.

Arsenic presents significant concern when found in aquatic sediments due to its origins from both natural phenomena and human-led activities. Given the potential environmental and health implications of high arsenic concentrations, consistent monitoring has been paramount.

The first systematic sediment collection campaigns were conducted in 1968 and 1969 in Lake Ontario and Lake Huron respectively, followed by Lake Erie in 1971, and Georgian Bay and Lake Superior in 1973. The majority of the samples were analyzed for metals, with a focus on mercury (Kemp and Thomas, 1976; Kemp et al., 1978).

A second large sampling effort occurred almost 30 years later, with sediment collected from Lakes Ontario and Erie in 1997 and 1998 (Marvin et al., 2003; Painter et al., 2001) and Lakes St. Clair, Superior, Huron and Georgian Bay in 2001 and 2002 (Gewurtz et al., 2007; Gewurtz et al., 2008). In addition to metals, the substances targeted at that time included polychlorinated biphenyls (PCBs), dioxins and furans, PAHs and some organochlorine substances, such as the pesticide DDT.

Finally, ECCC collected surficial sediments and sediment cores from Lake Erie, Lake St. Clair and the Detroit River in 2013 and 2014, Lake Superior in 2016, Lake Huron, Georgian Bay and the St. Mary’s River in 2017, and Lake Ontario in 2018 and 2019. The majority of samples were analyzed for metals, PCBs, organochlorine pesticides and PAHs. Several analyses of emerging substances of interest such as polybrominated diphenyl ethers (PBDEs), per- and poly-fluorinated alkyl substances (PFAS), antioxidants, phthalates, triclosan and bisphenol A (BPA) were also conducted under the CMP program.

The first sediment sampling campaigns in the St. Lawrence River were carried out in 1976 for the whole river (Cornwall to Quebec) and in 1979 at Lake Saint-François by research groups associated with Environment Canada (Sérodes, 1978; Sloterdijk, 1985). The main purpose of this work was to better understand the sedimentary dynamics of the St. Lawrence River and to develop a first overview of metal contamination (total metals), with a focus on mercury. For Lake Saint-François, it also aimed to determine the extent of PCB contamination.

It was not until the mid-1980s that systematic sampling campaigns were carried out in Lake Saint-Louis (1985), Lake Saint-Pierre (1986), the Petit Bassin de La Prairie (1987), Lake Saint-François and the national harbours of Montreal, Trois-Rivières and Quebec City (1989). Funded by the SLAP, this sampling aimed to establish the status of metal, PCB, and PAH contamination for the entire St. Lawrence River, to define critical areas of concern for aquatic life, and to develop sediment remediation scenarios in certain areas (Champoux and Sloterdijk, 1988; Hardy et al., 1991a and b; Lorrain and Jarry, 1993; Procéan inc, 1990; G.D.G. Environnement Ltée, 1990).

Collection work began at Lake Saint-François in 1999 and was repeated in 2008 and 2018 (Pelletier and Lepage, 2003; Pelletier, 2010; Pelletier, 2020). For Lake Saint-Louis sediments, sampling was carried out in 2003 and 2015 (Pelletier, 2009; Pelletier, 2019), while Lake Saint-Pierre was visited in 2003 and 2013 (Pelletier, 2008; Pelletier, 2018). In addition to the fluvial lakes, sampling was also carried out in the Lake des Deux Montagnes (2008), in the Upper Estuary (2009), in the Quebec City area (2012), and finally in 2014 in Le Petit Bassin de La Prairie (note these data are not published except for the Quebec City area under Pelletier and Blais (2018)). All of this work aimed to determine the evolution of the spatial dispersion of contaminants and to establish the temporal trend in order to evaluate the effectiveness of environmental measures introduced since the end of the 1980s. It should be noted that many of the samples collected over the last decade have served as a basis for the analyses of substances of emerging interest targeted by the CMP program.

9.5 Surface water

9.5.1 Water - arsenic monitoring in Canadian rivers

The Canada Water Act requires that the Government of Canada, in coordination with the provinces, conduct water quality monitoring in Canada to determine the status and trends in water quality in the country. ECCC has conducted metals monitoring in surface waters across Canada since 1986. Core water quality parameters monitored under the program include a number of physical-chemical parameters (temperature, pH, specific conductance, turbidity, cations), nutrients and metals. Arsenic is among the metals that have been monitored in surface waters from the onset of the program.

Historically, water monitoring programs were designed and conducted on a regional basis, with sampling protocols, analytical methods and site selection strategies varying from watershed to watershed, or from region to region. More recently, efforts have been made to coordinate metals monitoring nationally such that core network sites are monitored on a regular basis and sampling and analytical methodologies are more standardized across the country. That core network of sites is comprised of 220 long-term monitoring sites and includes a variety of land use types such as urban, agricultural, forestry and reference sites. The network is focused on sites of federal interest such as international and transboundary waterways, federal lands, waterways involving federal undertakings, and waterways at high risk of water quality or ecological impairment. As such, the network does not necessarily represent the full range of conditions across the country, but rather the range of conditions at the sites that are monitored. For example, inland rivers in Ontario are monitored solely by the provincial government.

In addition to those core long term sites, there are many hundreds of sites that have been monitored for metals for shorter periods of time, some of which are affiliated with point source releases of metals such as mining operations, power generation facilities, smelters and other industrial sources.

The current assessment of arsenic in Canadian surface waters does not include those shorter-term data records in this broader Canadian analysis as the long-term water quality monitoring network does not align with those point source industries, and short-term datasets are not sufficient to perform temporal trend analyses. However, in certain cases these short-term datasets were used to investigate specific questions.

9.5.2 Water - Great Lakes connecting channels

ECCC began water quality monitoring in the connecting channels of the Great Lakes with the establishment of a fixed sampling site on the Niagara River at Niagara-on-the-Lake in 1975. Over the next decade, additional sites were added on the St. Lawrence River at Wolfe Island (1976), upstream on the Niagara River at Fort Erie (1983), and at Point Edward and Port Lambton on the St. Clair River (1986).

Water quality monitoring in the connecting channels is undertaken as part of ECCC’s commitment to the GLWQA under the auspices of the International Joint Commission (IJC, 1989). More specifically, monitoring in the connecting channels is intended to aid in the evaluation of the effectiveness of pollution control programs carried out in the Great Lakes Basin and data generated from this sampling are used to identify exceedances of water quality guidelines, to assess current water quality conditions, and to evaluate trends.

9.5.3 Water - Great Lakes waters

Arsenic is measured with other parameters of concern in the Laurentian Great Lakes, a crucial transboundary aquatic system shared between the United States and Canada, in support of the binational GLWQA. It is included among a suite of metals that are monitored as part of the Great Lakes Surveillance Program (GLSP), which is ECCC’s ship-based, long-term water quality monitoring program. Spatial patterns in water quality can be determined using the network of the GLSP. Samples are taken from both nearshore and offshore environments, in both Canadian and US waters with the exception of the 2019 campaign in Lake Superior in which only Canadian waters were sampled. Using offshore stations alone, where sites are removed from variability due to watershed sources, temporal trends can be detected that may not be evident in tributaries and nearshore waters. Monitoring for contaminants in the Great Lakes offshore is therefore a powerful method for detecting trends over time in the aquatic environment.

For the GLSP, total metals are measured using ultra-trace clean techniques due to the great dilution capacity of the lakes and the potential for trace contamination by sample handling. Since 2003, monitoring and laboratory techniques have advanced sufficiently, and the data can be used to reliably demonstrate spatial and temporal trends in Great Lakes waters.

9.5.4 Water - Great Lakes precipitation

Monitoring stations for precipitation in the Great Lakes basin were established as part of the binational Integrated Atmospheric Deposition Network (IADN), designed to conduct air and precipitation monitoring in the Great Lakes Basin on a year-round basis. Although IADN has been discontinued, some activities have been maintained as part of ECCC’s Great Lakes monitoring programs. The concentrations measured in precipitation are used to evaluate spatial and temporal trends and to provide atmospheric loading estimates.

9.6 Biota - Fish Contaminants Monitoring Program (FCMP)

The Fish Contaminants Monitoring Program (FCMP) was initiated in 1976 and initially focused on the Great Lakes system. In 2006, the FCMP expanded its scope to include areas outside the Great Lakes, becoming national in scope. The program also began monitoring trends in priority pollutants and emerging chemicals of concern as part of the CMP.

In addition to the Great Lakes, the program monitors sites more removed from urban influence in the north, sites exposed to agricultural effluent, forestry, and mining in the Prairie Provinces, British Columbia, and Ontario, and sites near areas of higher population density and industry.

The data collection is primarily conducted by ECCC staff. In certain locations, aquatic biota is also collected by provincial, state, and federal agencies, Indigenous groups, and the public.

The main objective of the Fish Contaminants Monitoring Program is to determine ecosystem contaminant levels in freshwater environments to help understand the bioaccumulation of contaminants, including arsenic, in aquatic organisms. Top predator fish, such as lake trout and walleye, are the primary fish indicators due to their ability to accumulate elevated concentrations of some metals and their presence across Canada, providing insights into the health of aquatic ecosystems and potential risks to human health.

The FCMP was initiated in 1976. The objective was to collect a variety of biological samples in freshwater environments for the purpose of determining ecosystem contaminant levels. The FCMP has evolved over time; initially the program was part of Fisheries and Oceans Canada’s Contaminants Surveillance Program. The main objective of the program was to provide annual reports on the status and trends of toxic chemicals in the Great Lakes system generated from the analysis of persistent contaminant levels in field collections of sediment and fish throughout the basin. A subset of the samples collected during the field season formed the holdings of the Great Lakes Fisheries Specimen Bank, now renamed the National Aquatic Biological Specimen Bank (NABSB). A portion of samples collected from field sampling each year continue to be archived in NABSB and allow for the retrospective analysis of compounds of interest in aquatic biota from across Canada. The FCMP forms part of Canada's commitment under the GLWQA, under Annex 11 (Surveillance and Monitoring) and Annex 12 (Persistent Toxic Substances). Annually, two to four offshore sites are monitored on each Great Lake, with the exclusion of Lake Michigan.

In 2006, the FCMP, tissue archive, and staff migrated to ECCC. At the same time, the program expanded to include areas outside the Great Lakes and become national in scope. From 2006 to 2015, biota samples from many freshwater sites across Canada were collected and incorporated into the FCMP as part of the Clean Air Regulatory Agenda. The focus of these collections was primarily to assess concentrations of mercury and other contaminants in the environment from aerial deposition. Also in 2006, the FCMP began collecting and analyzing biota to monitor trends in priority pollutants and surveillance of emerging chemicals of concern as part of the CMP.

Note: Current monitoring sites are marked with asterisks.

9.7 Biota - wildlife

Arsenic concentrations in wildlife tissues were obtained from the Northern Contaminants Program (NCP), the CMP and published science articles.

The NCP, led by Crown-Indigenous Relations and Northern Affairs Canada, is a comprehensive initiative designed to monitor and assess the presence and impact of contaminants in the Canadian Arctic. The program's primary focus is on long-range contaminants that are transported to the Arctic region from other parts of the world.

The primary objective of the NCP is to safeguard the health and well-being of both the Arctic ecosystem and its inhabitants. By collecting data on contaminants like arsenic, the program aims to understand the sources, pathways, and effects of these contaminants on wildlife and, by extension, on Indigenous communities that rely on these animals for sustenance and cultural practices.

The monitoring efforts span across various regions of the Canadian Arctic, including the northern and central Yukon, and western Nunavut. Data collection has been ongoing for several years, with some datasets, like the one for the barren-ground Porcupine caribou herd, extending from 1993 to 2021, making it one of the longest monitoring periods for arsenic in wildlife.

The program encompasses a wide range of wildlife species, reflecting the diverse Arctic ecosystem. This includes:

• Terrestrial mammals like caribou, moose, and deer mice
• Marine mammals such as ringed seals and polar bears
• Birds, with a particular focus on various gull species, common eiders, and terrestrial birds like the European starling
• Amphibians, including wood frogs and northern leopard frogs
• Reptiles like the snapping turtle

Note: Mean type refers to calculation method based on dry weight (dw) or wet weight (ww) concentrations; sex: male (M), female (F), unknown (U), information not available (na); n: number of samples.

* single sample of five individuals (pooled).

** data from Crown-Indigenous Relations and Northern Affairs Canada (CIRNAC) as part of Northern Contaminants Program (NCP) monitoring.

*** While designated as a waterbird here, these birds could be also considered as marine - depending on where they are feeding - since locations of these colonies are in an estuarine environment.

Note: Data sources are names of ECCC project leads who provided data. Mean type refers to calculation method based on dry weight (dw) or wet weight (ww) concentrations; sex: male (M), female (F), unknown (U), information not available (na); n: number of samples. Conversion factors from wet weight to dry weight concentrations are in Table 10 below.

9.8 Wastewater - municipal wastewater effluent

The wastewater monitoring program has generated a large dataset on levels of chemical substances in wastewater influents, effluents, and biosolids since 2009.  Arsenic concentrations were recently measured in samples of raw influent, final effluent, and treated biosolids collected from 27 WWTSs in 2018, 2019, and 2021.  Arsenic concentrations were previously measured and reported in raw influent, final effluent, and treated biosolids collected from 25 WWTSs sampled between 2009 and 2012 in warm and cold seasons (Wong & Smyth 2016).

Selection of wastewater treatment systems (WWTSs)

Criteria for selection: The study included 27 WWTSs selected to represent a broad spectrum of treatment technologies and geographic diversity across Canada. The selection aimed to capture the variations in arsenic removal efficiencies across different types of wastewater treatment systems, from simple lagoon-based systems to advanced, nutrient-removal facilities. This diverse selection helps in understanding the efficacy of various treatment processes in arsenic removal.

Anonymity and representation: Participating WWTSs were guaranteed anonymity, identified only by their treatment process and operational scale. This approach facilitated the participation of WWTSs while ensuring data privacy. The plants selected for the study were representative of typical Canadian wastewater treatment scenarios, encompassing a range of sizes and technologies to ensure the findings were broadly applicable.

9.9 Air, water, land - National Pollutant Release Inventory

The National Pollutant Release Inventory (NPRI) is a comprehensive industrial reporting system in Canada that tracks and discloses information about pollutant releases, disposals, and transfers. Managed by ECCC, the NPRI plays a crucial role in promoting transparency and accountability in environmental practices. It requires industrial facilities across various sectors to report their releases of specified substances, including toxic chemicals, heavy metals, and hazardous materials.

One of the significant advantages of the NPRI is the publicly accessible database it maintains. The reported data is compiled and made available to the public, facilitating access to information on pollutant releases in different regions and sectors. This accessibility empowers citizens, communities, researchers, and policymakers to analyze the data and make informed decisions regarding environmental concerns.

When it comes to the ecological component of the arsenic PME, the NPRI is a valuable source of data. Arsenic, being a toxic substance, is included in the list of specified substances reported to the NPRI. By utilizing the data from the NPRI, evaluators can estimate the amount of arsenic released to the environment, including air, water and land. The information can help in identifying areas or industries with significant arsenic releases and guide the development of mitigation strategies to protect ecosystems.

To enhance clarity and transparency, the following table provides a mapping between the industry groupings used in this report and the corresponding subcategories from the NPRI. In several cases, the sectors presented in the report—such as “metal & mineral production” or “mining”—are not direct NPRI categories but are instead aggregates of multiple NPRI-defined sectors. This table is intended to support interpretation of the data by illustrating how each report-specific industry aligns with NPRI’s standardized sector classifications.

Table 11: Industry and associated activity

Industry	Associated activity
Chemical and Petrochemical Industry	All other basic inorganic chemical manufacturing
Chemical and Petrochemical Industry	Other basic organic chemical manufacturing
Chemical and Petrochemical Industry	Petrochemical manufacturing
Chemical and Petrochemical Industry	All other miscellaneous chemical product manufacturing
Chemical and Petrochemical Industry	Petroleum refineries
Chemical and Petrochemical Industry	Chemical fertilizer (except potash) manufacturing
Chemical and Petrochemical Industry	Resin and synthetic rubber manufacturing
Chemical and Petrochemical Industry	Mixed fertilizer manufacturing
Construction Materials	Cement manufacturing
Construction Materials	All other non-metallic mineral product manufacturing
Construction Materials	Lime manufacturing
Construction Materials	Gypsum product manufacturing
Construction Materials	Ready-mix concrete manufacturing
Education and Other Services	Universities
Education and Other Services	Dry cleaning and laundry services (except coin-operated)
Education and Other Services	Research and development in the physical, engineering and life sciences
Education and Other Services	Testing laboratories
Education and Other Services	Engineering services
Education and Other Services	All other professional, scientific and technical services
Electricity and Combustion	Fossil-fuel electric power generation
Electricity and Combustion	Other electric power generation
Electricity and Combustion	Nuclear electric power generation
Industrial and Consumer Products Manufacturing	All other miscellaneous manufacturing
Industrial and Consumer Products Manufacturing	Frozen food manufacturing
Industrial and Consumer Products Manufacturing	Other motor vehicle parts manufacturing
Industrial and Consumer Products Manufacturing	Automobile and light-duty motor vehicle manufacturing
Industrial and Consumer Products Manufacturing	Power, distribution and specialty transformers manufacturing
Industrial and Consumer Products Manufacturing	Motor vehicle brake system manufacturing
Industrial and Consumer Products Manufacturing	Commercial and service industry machinery manufacturing
Industrial and Consumer Products Manufacturing	Motor vehicle steering and suspension components (except spring) manufacturing
Industrial and Consumer Products Manufacturing	Aerospace product and parts manufacturing
Industrial and Consumer Products Manufacturing	Other transportation equipment manufacturing
Industrial and Consumer Products Manufacturing	Semiconductor and other electronic component manufacturing
Industrial and Consumer Products Manufacturing	All other plastic product manufacturing
Industrial and Consumer Products Manufacturing	Plastic film and sheet manufacturing
Industrial and Consumer Products Manufacturing	Plastic pipe and pipe fitting manufacturing
Industrial and Consumer Products Manufacturing	Other rubber product manufacturing
Metal & Mineral Production	All other miscellaneous fabricated metal product manufacturing
Metal & Mineral Production	Iron foundries
Metal & Mineral Production	Iron and steel mills and ferro-alloy manufacturing
Metal & Mineral Production	Aluminum rolling, drawing, extruding and alloying
Metal & Mineral Production	Coating, engraving, cold and heat treating and allied activities
Metal & Mineral Production	Cold-rolled steel shape manufacturing
Metal & Mineral Production	Machine shops
Metal & Mineral Production	Non-ferrous metal (except aluminum) smelting and refining
Metal & Mineral Production	Non-ferrous metal (except copper and aluminum) rolling, drawing, extruding and alloying
Metal & Mineral Production	Non-ferrous metal foundries (except die-casting)
Metal & Mineral Production	Other fabricated wire product manufacturing
Metal & Mineral Production	Steel foundries
Mining	Iron ore mining
Mining	Copper-zinc ore mining
Mining	Gold and silver ore mining
Mining	All other metal ore mining
Mining	Nickel-copper ore mining
Mining	Mined oil sands extraction
Mining	Uranium ore mining
Mining	Bituminous coal mining
Mining	Lead-zinc ore mining
Mining	Diamond mining
Mining	Other support activities for mining
Mining	In-situ oil sands extraction
Mining	Oil and gas extraction (except oil sands)
Mining	Potash mining
Mining	Shale, clay and refractory mineral mining and quarrying
Mining	Subbituminous coal mining
Mining	Non-conventional oil extraction
Mining	All other non-metallic mineral mining and quarrying
Mining	Asbestos mining
Pulp and Paper	Support activities for forestry
Pulp and Paper	Wood preservation
Pulp and Paper	All other miscellaneous wood product manufacturing
Pulp and Paper	Hardwood veneer and plywood mills
Pulp and Paper	Chemical pulp mills
Pulp and Paper	Particle board and fibreboard mills
Pulp and Paper	Paper (except newsprint) mills
Pulp and Paper	Newsprint mills
Pulp and Paper	Paperboard mills
Pulp and Paper	Mechanical pulp mills
Pulp and Paper	Sawmills (except shingle and shake mills)
Pulp and Paper	Waferboard mills
Pulp and Paper	Softwood veneer and plywood mills
Pulp and Paper	Structural wood product manufacturing
Waste and Municipal Biosolids	Steam and air-conditioning supply
Waste and Municipal Biosolids	Waste treatment and disposal
Waste and Municipal Biosolids	Sewage treatment facilities
Waste and Municipal Biosolids	Remediation services
Waste and Municipal Biosolids	Highway, street and bridge construction
Waste and Municipal Biosolids	Water supply and irrigation systems
Waste and Municipal Biosolids	Material recovery facilities
Waste and Municipal Biosolids	All other waste management services
Waste and Municipal Biosolids	Waste collection
Wholesale and Logistics	Lumber, plywood and millwork merchant wholesalers
Wholesale and Logistics	Marine cargo handling
Wholesale and Logistics	Petroleum, petroleum products, and other hydrocarbons merchant wholesalers
Wholesale and Logistics	Recyclable metal merchant wholesalers
Wholesale and Logistics	Other warehousing and storage
Wholesale and Logistics	Other airport operations
Wholesale and Logistics	Lessors of non-residential buildings (except mini-warehouses)