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

Introduction

The Government of Canada aims to reduce the risks of toxic substances to Canadians and the environment through risk management actions under the Chemicals Management Plan. Performance measurement evaluations are an important part of the overall chemicals management process that provide Canadians with information on the effectiveness of risk management actions in place for toxic substances.

In 1994, the Government published a Priority Substance List assessment on risks of cadmium and its compounds. The assessment concluded that several inorganic cadmium compounds were likely toxic to human health and the environment. For this reason, they were added to Schedule 1, the List of Toxic Substances, under the Canadian Environmental Protection Act, 1999 in 2000. Based on past assessment activities and risk management actions, it was determined that the risks of inorganic cadmium compounds were addressed by the implementation of the Toxic Substances Management Policy and existing measures for key industrial sectors or similar pollutants. As a result, no substance-specific risk management approach or strategy for cadmium was developed.

For substance-based performance measurement evaluations, it is important to find out whether the risk management approach taken by the Government has resulted in effective risk management action. Effective risk management actions will result in progress to achieve the risk management objectives set by the Government for that substance. No objectives were previously developed for cadmium, but using the objectives of the Toxic Substances Management Policy for guidance, and considering objectives proposed for other toxic metal substances, the following objectives are proposed for the purposes of this evaluation:^{Footnote 1}

• Risk management objective: to achieve the lowest level of anthropogenic (human caused) releases of inorganic cadmium compounds that are technically and economically feasible, taking into consideration socioeconomic factors
• Environmental objective: to reduce Canadian anthropogenic releases of inorganic cadmium compounds so as not to exceed levels expected to cause adverse effects to the environment, taking into consideration natural background concentrations

This report evaluates whether the objectives set for inorganic cadmium compounds have been met, the successfulness of the Government of Canada’s risk management approach in achieving the objectives, and whether additional action is required. An evaluation of the effectiveness of the Government of Canada’s actions to protect human health will be prepared by Health Canada.

Cadmium in the environment

Cadmium is an elemental metal that is found naturally in the earth’s crust. In the environment it quickly bonds with other elements to form inorganic cadmium compounds. Natural processes like forest fires, volcanic activity, erosion, weathering, and oceanic cycling can release cadmium to the environment. However, human activities such as coal burning, metal production, manufacturing processes, use and disposal of products, and land application of sewage sludge release much more cadmium than natural sources.

Cadmium is produced primarily as a by-product of zinc refining and may be found in many different products like batteries, paints and coatings, ceramics, and plastics and solar cells. The 1994 Assessment noted several sectors and sources of concern that release inorganic cadmium compounds to the environment which may result in levels that cause environmental harm. These include metal production (particularly base metal smelting and refining), stationary fuel combustion (power generation and heating), transportation, solid waste disposal, and land application of sewage sludge. 

Cadmium does not break down in the environment, and may be found in air, water, soil, sediment, plants, and animals, including humans. Inorganic cadmium compounds are formed as small particles in air as a result of cadmium emissions from high temperature activities such as metal production and refining or combustion processes. These airborne particles eventually fall to the ground, but may first be carried by winds to areas far away from the source.

Inorganic cadmium compounds may enter freshwater by falling from the air, surface water runoff from rain events, or by direct releases from industrial sources. Cadmium compounds are easily dissolved in water and as a result may be carried downstream, away from the initial point of release. Once in water, inorganic cadmium compounds can also end up in the sediment by attaching to small floating particles that then fall to the bottom. If conditions in the sediment or overlying water change, the inorganic cadmium compounds can re-dissolve from the sediment and once again enter the water.

Animals can take up cadmium when inorganic cadmium compounds are present in the food, water, or air that they eat, drink, or breathe. Cadmium accumulates in the bodies of animals (bioaccumulation) and, in high enough levels, can cause reduced growth, changes to organ weights and organ damage, cancer, reduced ability to reproduce, cognitive and developmental delays, and changes in behaviour.

Key findings

Releases from human activities

Most of the cadmium released to the environment from human activities is released to air, primarily from sectors of concern identified in the 1994 Assessment. Releases from the sectors of concern have declined over time according to the Air Pollutant Emissions Inventory.

• Significant decreases in emissions were realized by the non-ferrous smelting and refining sector, resulting in changes to the overall profile of cadmium releases
• Releases from residential/commercial/institutional heating and manufacturing play a much larger role in the emissions profile in 2020 than in 1994

Cadmium releases to water are about half as much as that released to air according to the National Pollutant Release Inventory. Releases were lower in 2020 than in 1994 but releases have remained relatively stable over the last 10 years.

• Releases declined from sectors of concern identified in the 1994 Assessment, especially from non-ferrous metal production and processing
• Most of the cadmium released to water comes from wastewater treatment^{Footnote 2} and pulp and paper manufacturing^{Footnote 3}. Releases from these sectors have remained relatively unchanged since 2002. Neither was identified as a sector of concern for cadmium releases in the 1994 Assessment

Wastewater treatment plants are effective at removing cadmium entering the municipal wastewater system.

• Cadmium entering wastewater treatment plants comes from industrial processes and/or use and disposal of cadmium products. Treatment processes remove most cadmium from wastewater. Low levels of cadmium were found in treated wastewater
• Sewage sludge treated and applied to land in the form of municipal biosolids typically had levels lower than compost standards

Releases of cadmium to land are very small according to the National Pollutant Release Inventory.

• Releases of cadmium to land from sectors of concern identified in the 1994 assessment are usually not significant
• Releases to land mostly come from manufacturing pulp and paper and wood products. These were not identified as a concern in the 1994 assessment

Over time, more cadmium was disposed of by more facilities, but the amount of cadmium deposited in hazardous solid waste landfills remained relatively unchanged.

• More waste was transferred for treatment before disposal and less waste was transferred for metals recycling and recovery operations. Most of the waste transferred comes from only a small number of facilities in the non-ferrous smelting and refining industry
• Most cadmium waste was disposed of by hazardous waste landfills

Currently operating large municipal solid waste landfills are unlikely to be major sources of cadmium release. However, because it may take several years for cadmium to be drawn from waste materials through rain filtering through the contaminated materials, this liquid (leachate) should be periodically monitored.

• Cadmium was found in less than half of leachate samples and about 87% of municipal solid waste landfills send their leachate to wastewater treatment plants
• Levels of cadmium in municipal solid waste landfill leachate in Canada are about the same as those found in other developed countries

Some sources of cadmium are not captured in existing release inventories. Releases of cadmium to the environment may be underestimated.

• The Pollutants Affecting Whales and their Prey Inventory Tool includes estimates of releases from a significant number of facilities and sources that do not report to the National Pollutant Release Inventory, leading to a much larger number of estimated releases to land and water, despite covering a much smaller area of Canada
• A comparison of release estimates with levels of cadmium measured in water indicates that some sources of metals (as well as other pollutants) may be missing from release estimates. For example, surface water runoff may also represent a significant source of cadmium entering water

Levels of cadmium in the environment

Industrial releases have declined and levels in the environment have mostly followed the same trends. Cadmium appears to be present in all environmental media at relatively low levels across Canada, with the exception of some hotspots.

Human sources contribute to cadmium levels in air that are above natural background concentrations, but ambient air quality guidelines have not been exceeded and levels in air are decreasing in most locations.

• Urban areas have higher cadmium concentrations than rural areas
• Metals production and processing and coal and fossil fuel combustion are the main sources of cadmium found in air
• Industrial and traffic sources in the United States contribute to cadmium levels in Canadian air
• Cadmium falling from the air by gravity or rain appears to be an important contributor to cadmium levels in water and sediment in some regions

Sediment concentrations of cadmium across Canada showed the greatest cause for concern compared to other environmental media due to a number of locations with levels that were higher than environmental quality guidelines.

• In particular, the Great Lakes, parts of the St. Lawrence, and the Atlantic sector had median concentrations above guideline levels
• It is important to consider the bioavailability of cadmium (the amount of cadmium in the environment that can be taken up by an organism) in assessing impacts to the environment. This is demonstrated by conflicting data patterns for water, fish and sediments for the Great Lakes region

Cadmium was found in both terrestrial and aquatic wildlife. 

• Levels found in land based animals are typically lower than those expected to cause effects. However, the impact of cadmium at very low levels has not been well studied in wild animals and there may be potential impacts to behaviour or immune responses that are not obvious in post-mortem examinations
• The impacts of the cadmium levels found in fish are unclear as there are no known guidelines for fish to indicate at what levels cadmium in the body leads to negative health effects. Cadmium does not appear to biomagnify, meaning that adverse impacts seen due to high cadmium levels in sediments may be more visible in small bottom feeding fish and animals than the fish that eat them
• Additionally, the relative burden of cadmium in the mixture of contaminants to which wildlife and fish are exposed is difficult to estimate

It is difficult to compare sampling undertaken in different media because they are often collected at different locations at different times, but it is possible to identify some hotspots where cadmium levels may be of concern in one or more media.

The Great Lakes:

• The Great Lakes region is the most well studied and has the most comprehensive datasets
• Looking at the data from all environmental media, it appears that Lake Erie and the connecting channels of the lower Great Lakes may be more greatly impacted by cadmium pollution than other areas in Canada. This is evidenced by observations of higher cadmium levels in air in the Great Lakes regions (Windsor, Hamilton) compared to other regions, sediment levels well above the threshold effects levels, particularly in the western basin of Lake Erie, exceedances of water quality guidelines, and observations of higher levels in fish from this area compared to other areas. However, observations of cadmium levels in wildlife were no higher in the Great Lakes region compared to other areas of Canada

Locations near industrial operations:

• Higher levels of cadmium were observed in wildlife, fish, and sediment near active and closed mining and smelting operations (for example Columbia River, St. Lawrence, Grand Lake, Kejimijujik) and marine transportation of ores (as seen in Quebec City)
• Data from metals mining operations showed that cadmium concentrations released in effluent and concentrations in exposure areas are declining. However, some reference and exposure areas still have cadmium levels exceeding environmental quality guidelines
• Cadmium levels in air, fish, and wildlife did not appear to be higher near oil sands operations than elsewhere in Canada. These findings are consistent with the release inventory data where the metals and ore industry is the primary source of cadmium releases and oil and gas production contributes much smaller amounts
• Data for cadmium in the environment near other industrial sources were not available

Habitat for endangered whales and their prey:

• Additional hotspots and industrial sources may be discovered as work continues to identify sources of contaminants of concern in the critical habitat areas of endangered whales and their prey
• Data from the Pollutants Affecting Whales and their Prey Inventory Tool suggests there may be sources of cadmium releases not currently captured by existing federal release inventories. In addition, surface water runoff may be a large contributor to cadmium levels in the Fraser River basin and St Lawrence River

Risk Management actions

Actions have been taken to manage the risks of cadmium to the environment starting from the early 1990s. Although none have targeted cadmium directly, they have resulted in decreases in releases of cadmium to the environment.

• 24 relevant risk management measures have been put in place: 20 for sectors of concern identified in the 1994 assessment and 4 for other sectors determined to be relevant
• No relevant action was taken to reduce cadmium releases from the transportation sector which was noted to be of concern in the 1994 assessment. Limited data on the transportation sector was available to be considered in this evaluation
• Cadmium has not been the primary target for any risk management action; however, it is addressed through efforts to manage more broadly the release of metals and particulate matter from industrial sectors

Clear targets and objectives were only set for 11 of 24 instruments.

• 3 achieved their objectives, 1 did not achieve its objective, and 7 are in progress so it is too soon to say whether they have been successful
• It was not possible to draw a link between successful risk management instruments and trends in industrial releases for any given sector. This was due to the limited number of instruments that have undergone instrument based performance measurement and little data available on the rates of implementation of non-regulatory instruments

Voluntary instruments accounted for one third of relevant instruments.

• In general, no objectives or targets were set for them and there was limited information available on their implementation as no reporting was required
• Little information was available on the rates of implementation of best available technologies and best environmental practices to reduce releases of cadmium and other substances. Information on their rates of implementation would inform risk managers whether further work is needed or if all facilities have worked to reduce their releases as much as possible

It is difficult to evaluate the success of multi-sectoral risk management actions.

• While useful to target many substances across a range of industrial sectors, the administration of such instruments is challenging and progress reporting is inconsistent

Collaborations with international and domestic partners are important for managing risks in areas beyond federal jurisdiction and for managing risks of toxic substances for species at risk.

• Success has been realized in terms of reducing releases and remediating contaminated sites in Ontario, although recent actions under the Canada-Ontario Agreement have been refocused on other contaminants. Risks from cadmium levels in the Great Lakes remain, and further action on cadmium should be considered in future iterations of the agreement
• Internationally, progress has been made under the Convention on Long-range Transboundary Air Pollution, and Canada has reduced its cadmium emissions to be in compliance with the Convention commitments
• Environmental data suggest that Canada may still be receiving cadmium from sources of release in the United States. This issue may be relevant to consider in future revisions to the Canada-US Water Quality Agreement and the Canada-US Air Quality Agreement

Results of the evaluation

Evaluation of the risk management approach

Controlling overall releases of metals in particulate matter appears to be effective at controlling cadmium releases for many of the sectors of concern, particularly those where air is the primary release pathway. However, the decision not to develop a risk management strategy or approach for cadmium specifically led to gaps for some sectors where no relevant instruments were developed despite being listed in the 1994 assessment as potentially posing a risk to the environment.

Progress in achieving the risk management objective

Based on the evidence available, there has been progress toward achieving the risk management objective. Releases of cadmium have been reduced; however, without information being collected on rates of implementation of best management practices and best available technologies, there is not enough information to determine whether facilities have reduced their releases to the lowest levels technically and economically feasible and whether the risk management objective has been achieved.

Progress in achieving the environmental objective

Environmental data show that levels of cadmium in the environment have been significantly reduced over time and are not a concern in most areas. However, there are still some hotspots where levels are above those thought to cause negative effects. The environmental objective has therefore not yet been achieved, though there has been progress made towards its achievement.

Response to new or emerging exposure sources

Sectors of concern identified in the 1994 Assessment account for the majority of reported releases to air, water, and land. However, as these sectors have reduced their releases, other sectors that were not identified as concerns in the 1994 Assessment have begun to make up a larger part of the cadmium releases profile. In 1994, sources of concern were responsible for nearly 100% of total releases reported to NPRI; in 2020, they were only responsible for 50%. Releases from wastewater treatment facilities and the pulp and paper industry now make up 40% of total reported releases. However, there is some uncertainty in the methods used to estimate low concentrations of cadmium releases from wastewater treatment facilities. The use and disposal of cadmium-containing products or other sources, such as facilities not meeting NPRI reporting requirements, may account for much of the cadmium entering and released from wastewater treatment facilities, since limited transfers are reported from NPRI facilities to wastewater treatment. These are not sources of cadmium that have been considered in previous risk assessment work. Similarly, releases from pulp and paper facilities have not been considered. No risk management for these sources relevant to cadmium has been put in place to date.  

Evaluation of efforts to communicate risks to the public

The information available on risks of cadmium to the environment on Environment and Climate Change Canada’s web pages is spread across many pages and different communications material which may make it difficult for the public to find information about environmental risks of cadmium relevant to them. Newly developed interactive pages are becoming more easily accessible and are useful to provide engaging visual information that can be filtered to levels of interest to individuals. While environmental datasets are publicly available, without scientific analyses these data may not be useful for a general audience and do not provide meaningful information about levels of toxic substances in the Canadian environment. Environment and Climate Change Canada’s social media postings related to cadmium and its risks to the environment have been minimal.

Recommendations

Evaluating the effectiveness of risk management of toxic substances is important to ensure that all environmental risks have been considered and managed appropriately, particularly for substances that have not benefitted from the development of a substance specific risk management approach. A follow-up evaluation for cadmium should be completed by 2033 to re-evaluate whether the environmental and risk management objectives have been achieved.

To address the knowledge and risk management gaps identified in this evaluation the following recommendations are proposed:

Risk management and risk assessment

• Significant sources of release not considered in the 1994 Assessment should be studied further, and risk management for these sources should be considered as appropriate based on the outcomes of investigative work
• The government should consider risk management to control releases from commercial, residential and institutional heating sources in cooperation with provinces, territories, and municipalities as appropriate
• Information on rates of implementation of best environmental practices and best available technologies should be collected as part of instrument reporting requirements
• Periodic reviews of environmental codes of practice and guidelines should be conducted to ensure that they are current with technological advances and industry practices
• Collaborations with the United States, provinces and territories, and other partners should continue to help to address sources of cadmium entering the Canadian environment from beyond areas of federal jurisdiction

Research and monitoring

Release inventories and industrial monitoring:

• The federal government should consider identifying sources of cadmium releases to the environment and municipal wastewater that are not captured by NPRI on a national scale, as wastewater monitoring and data from PAWPIT suggest that these sources may be significant contributors to environmental cadmium levels
• Monitoring of wastewater influent, effluent and municipal biosolids should continue. Where possible, data collection should support the development of time series to better track changes in cadmium levels
• Leachate from municipal solid waste landfills should be periodically monitored as data show that more cadmium waste is being disposed of over time
• The results of monitoring from wastewater treatment and landfill leachate and other relevant industrial monitoring information should be used to better understand and quantify releases of cadmium to improve NPRI reporting

Air:

• Subject to available resources and through cooperation with provinces and territories, as appropriate, consider expanding existing air quality monitoring and atmospheric modelling for metals to fill gaps and provide improved national coverage, particularly in areas without ambient metals monitoring and near point sources of pollution. This would better inform risk management and risk assessment on sources of cadmium in air
• Existing ambient air quality guidelines for cadmium should be reviewed to determine their adequacy for protection of aquatic environments through atmospheric deposition and consider development of updated or new environmental quality guidelines, as needed

Aquatic environment:

• Work should continue to identify and manage, as appropriate, sources of cadmium releases in areas where levels remain above environmental guidelines in sediment and water. Particular attention should be paid to areas where levels are increasing or holding steady, taking into consideration natural conditions and potential contributions from the United States. Sources of sediment contamination in harbours may warrant further investigation
• The role and relative contribution of cadmium releases to air to levels in water and sediment from different sources of release, including forest fires, should be explored further
• Additional research on cadmium body burdens for aquatic species and potential impacts of cadmium in food web dynamics should be considered

Wildlife:

• Additional measurements for cadmium in wildlife should be collected near point-source emissions in Canada such as metal mines and ore smelters
• Further toxicological study of the effects of cadmium in wildlife should be considered, particularly for small mammals

Environmental effects monitoring programs:

• Further investigation should be considered for mining effluent exposure areas and reference areas where cadmium levels are higher than calculated guideline levels
• If amendments to the pulp and paper effluent regulations are proposed, requirements for effluent characterization for metals, including cadmium, should be considered to help assess the environmental impacts of cadmium releases from pulp and paper facilities and inform future performance measurement evaluations

Communication:

• The toxic substance webpage for cadmium should be the hub for environmental information about the substance and include links to the relevant resources and tools. Environment and Climate Change Canada should continue to maintain the page and ensure that its content is clear and up-to-date
• Information on levels of cadmium measured in the environment should be more accessible to the public
• The Government should track the frequency, successfulness and level of engagement of social media postings and work to improve messaging, as applicable, to better inform Canadians of environmental risks. Tracking of webpage visits should continue to provide information for future evaluations
• Increased targeted communication products (infographics, fact sheets, videos) to educate and communicate environmental risks of cadmium should be produced in plain language and be easily accessible