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Summary of PSRD2023-01: Proposed Special Review Decision of Atrazine and Its Associated End-use Products

Notice to the reader:

The online consultation is now closed.

Health Canada's Pest Management Regulatory Agency
6 February 2023
ISSN: 2561-636 (PDF version)
Catalogue number: H113-30/2023-1E-PDF (PDF version)

Date issued: 2023-02-06
Consultation closes: 2023-03-23 (+45 days from date issued)

PSRD2023-01 is subject to a 45-day public consultation period, during which the public, including the pesticide manufacturers and stakeholders, may submit written comments and additional information. To participate in this consultation process, visit the Pest Management Regulatory Agency (PMRA) Publications Section.

Should you require further information, please contact the Pest Management Information Service.

Purpose of this summary

Health Canada consults people when a pesticide undergoes a special review, and a decision is proposed. The Proposed Special Review Decision (PSRD) document explains the basis for Health Canada's proposed decision.

This summary includes details from selected parts of the PSRD focussed on key aspects of the decision that are potentially of greatest interest to people in Canada. It is written to help improve the understanding of Health Canada's pesticide decisions.

The technical details of the scientific risk assessment and changes to the way atrazine is used in Canada are available in the PSRD document. If you would like to read the document, please visit the Request Publication page for PSRD2023-01: Proposed Special Review Decision of Atrazine and Its Associated End-use Products.

On this page

Atrazine and its uses

Atrazine is an agricultural herbicide registered for sale in Canada to control weeds in certain agricultural crops. Atrazine is not available for people in Canada to use in or around the home.

Commercial use of atrazine

Products containing atrazine are registered in Canada for use on:

Atrazine is applied to fields when these crops are in the very early stages of development or before they are planted. For any of these crops, pre-emergent application is allowed. This is when the product is applied to the soil to kill the weed seeds while they are starting to grow. Atrazine is also registered for post-emergent application on corn and sorghum. This is when the product is applied to the plants after they have emerged from the soil but before they are fully grown.

Atrazine can be applied to agricultural fields either mixed with water, liquid fertilizers, or other approved products (known as tank mix partners). Atrazine can also be incorporated into granular fertilizers (fertilizer impregnation) in commercial fertilizer facilities.

Commercial products containing atrazine

To view all the products containing atrazine registered in Canada:

  1. Access the Search Product Label.
  2. Under the header Filter, select the field "Active Ingredient - English."
  3. Enter "atrazine" in the Value area.
  4. Click the Search button.

Proposed special review decision for atrazine

Health Canada, under the authority of the Pest Control Products Act, determined that with the implementation of proposed label changes all but one use of atrazine meets the requirements for the protection of human health and the environment. The one use of atrazine shown to not meet the requirements for protection of human health is proposed to be cancelled. The cancelled use is the incorporation of atrazine into granular fertilizers (fertilizer impregnation) in commercial fertilizer facilities.

Risk assessments conducted by Health Canada assume that pesticides are used according to the product labels.

Learn more about:

Proposed label changes for protection of human health

Understanding the changes

Closed mixing/loading system: Before applying atrazine to agricultural fields, workers first mix it with water, a tank mix partner, or liquid fertilizers and then "load" or transfer the pesticide into the spray tank. A closed mixing/loading system is designed by the manufacturer to enclose the pesticide to prevent it from contacting workers while it is being handled. Closed mixing/loading systems limit exposure when the pesticide is removed from its original container, rinsed, mixed, diluted, or transferred.

Closed cab: Atrazine can be applied to fields in Canada using a sprayer behind a tractor or a self-propelled sprayer. A closed cab has the driver enclosed in a chemical resistant barrier that surrounds them. It prevents the driver from coming in contact with the pesticide as it is being sprayed.

Proposed label changes for protection of the environment

Understanding the changes

Environmental precaution statements: These statements inform users of the potential toxicity to animals, plants, and microorganisms in water and on land and that it is possible for atrazine to leach into the ground and contaminate groundwater.

Buffer zones: The buffer zones are to protect sensitive habitats that are close to where atrazine is applied.

Precautionary runoff statements: The statements are to inform users how to reduce the potential for atrazine to be carried away from fields by water and runoff to nearby aquatic habitats.

For more information on how Health Canada assesses and manages risk from pesticides, refer to this guidance document: PMRA Guidance Document, A framework for risk assessment and risk management of pest control products.

Reason for a special review of atrazine

A special review is triggered under certain circumstances, as described in Section 17 of the Pest Control Products Act. The scope of a special review only evaluates the aspects of concern that triggered the special review. The special review approach is described in the PMRA Guidance Document: Approach to Special Reviews of Pesticides.

In 2017, Health Canada initiated a special review of atrazine. Health Canada received additional information and an analysis of this information indicated that the criteria listed in subsection 17(1) of the Pest Control Products Act had been met, and a special review was warranted.

Aspects of concern

The identified aspects of concern are:

Understanding the aspects of concern

Toxicology endpoints: Effect levels that form the basis of the reference values, which are then used in risk assessment. Reference values are the levels of atrazine that people, animals, plants, and microorganisms can safely be exposed to without any harmful effect on health.

Drinking water: Both surface water and groundwater can be used as sources of drinking water in Canada. Both types of water are considered in drinking water risk assessments.

Surface water: Atrazine can be present in surface water when it is applied to an agricultural field and then makes its way towards a body of water, such as a lake or river, through either the air or in water runoff.

Groundwater: Atrazine can be present in groundwater because it could move downwards through the soil to leach into a water source deep in the ground.

For more information on how special reviews are initiated in Canada, refer to the Pest Control Products Act and this guidance document:

Atrazine use in other countries compared to Canada

Atrazine is used in several other countries, including the United States, Australia, and New Zealand. Decisions about these products may differ because of country-specific laws and policies, or because of differences in how a pesticide is used in the country.

Atrazine use in the European Union

The use of atrazine in the European Union Member States (EU) was banned in 2004 due to concerns about atrazine leaching into groundwater. At that time, the levels of atrazine in EU groundwater monitoring data were higher than their set policy-based threshold.

In 2013, Health Canada initiated a special review based on the EU's decision to ban atrazine. Rather than setting a policy-based threshold for atrazine in groundwater, Health Canada used a risk-based approach to determine the potential risk to human health from the level of atrazine found in Canadian drinking water. Health Canada conducted a drinking water risk assessment. This assessment included looking at how the pesticide moves in the environment to get into drinking water, and the effects it could have on human health. It considered Canadian water monitoring data that measured the levels of atrazine and its chlorinated break-down products in drinking water sources, as well as the level of harm or toxicity of atrazine.

In 2017, after the assessment and considering all comments received during the public consultation period, Health Canada concluded there were no risks of concern to human health or the environment from exposure to atrazine in drinking water. The full details of this risk assessment and decision can be found in these documents that you can request access to:

Atrazine use in the United States of America

Atrazine is used more in the United States than in Canada. In Canada, atrazine is only used in commercial settings on crops of corn, sorghum and switchgrass and can only be applied once or twice a year. In the US, atrazine is used on more crops and in other areas, at higher application rates, and can be applied more often throughout the growing season than in Canada. It is also used domestically on residential lawns.

It is important to consider the more limited use of atrazine in Canada when putting information about atrazine into context.

Learn more about Atrazine used in the United States.

Key evidence to support this proposed special review decision for atrazine

In 2017, Health Canada conducted a special review of atrazine and its chlorinated break-down products. The review concluded that there were no risks of concern to human health and the environment from exposure in drinking water sourced from groundwater.

During consultation, Health Canada received new information about atrazine that led to the initiation of a second special review. As part of this review, Health Canada requested additional information about specific areas of concern under section 19 of the Pest Control Products Act.

In addition to the information requested under section 19, Health Canada considered relevant scientific information to evaluate the aspects of concern for atrazine. This meant over 1400 scientific studies were reviewed, including published scientific literature and unpublished registrant-submitted data.

A full list of all sources of information used in the risk assessment and proposed special review decision are in the Proposed Special Review Decision (PSRD) document. Additional information sources were reviewed but if they are not listed in the PSRD document, it means they were not relevant or did not meet our requirements for use in the risk assessment.

You can find more information about:

Human health

To understand if atrazine meets the requirements for protection of human health, Health Canada updated the toxicology endpoints and health reference values. These are the levels of atrazine that people can safely be exposed to. The reference values were compared to:

How atrazine enters the human body

Atrazine can enter the human body in different ways. It can enter through:

Health Canada considered these key exposure pathways when conducting its assessment.

For more information on how Health Canada assesses pesticide exposure, refer to the guidance document: Science Policy Note SPN2014-01, General Exposure Factor Inputs for Dietary, Occupational, and Residential Exposure Assessments.

Exposure to atrazine in the diet

One way people may be exposed to atrazine is through the foods they eat and the water they drink. Drinking water is one of the aspects of concern of this special review. Because of this, Health Canada's dietary assessments have been updated to incorporate:

The dietary risk assessment looks at the amount of pesticide residue in food and drinking water. The results showed that exposure to atrazine and its break-down products (metabolites) in Canadian food and drinking water sources continue to meet Health Canada's current requirements for protection of human health.

Being a bystander

When atrazine is applied to an agricultural field, particles of the pesticide may drift off-target (called spray drift) and potentially expose a bystander. To minimize this, updates to the spray drift statements are being proposed for the labels.

Concentrations of atrazine were measured in the air in Canadian agricultural regions when atrazine would likely be used on crops. Health Canada has conducted a bystander inhalation assessment using the maximum measured air concentration from the available data. Bystander inhalation exposure levels were shown to meet Health Canada's requirements for protection of human health.

Exposure when working with atrazine

Agricultural workers can be exposed by mixing, loading, and applying atrazine. Exposure is likely in the form of skin contact and inhalation. Atrazine can be mixed with granular fertilizer in commercial fertilizer facilities. When a fertilizer is mixed with a pesticide, it is called an impregnated fertilizer. Workers mixing atrazine with granular fertilizer could be exposed to atrazine at a level that exceeds the requirements for protection of human health. Risks could be lowered by using additional personal protective equipment, or by using a closed transfer system. However, because feasible management measures were not identified for mixing atrazine with granular fertilizer in commercial facilities, Health Canada is proposing to cancel this use.

The worker risk assessment for the other uses of atrazine showed that exposure to atrazine continues to meet Health Canada's current requirements for protection of human health with the proposed updates to the label.

Potential effects of atrazine on human health

The large amount of data generated from the hundreds of scientific studies on atrazine and its metabolites shows that at certain levels, these chemicals can potentially cause harmful effects in the bodies of mammals, including humans. The risk assessment conducted by Health Canada considered all the known potential health effects associated with atrazine and identified the dose levels where health effects may happen.

Uses for a pesticide are only approved when the potential exposure level is at least 100-fold lower than the level where there are no health effects. To ensure the protection of human health, there is a large margin between the amount of pesticide that is legally allowed for use and the level at which health effects may occur. In addition, specific scientific assessments are conducted for vulnerable and sensitive subgroups, including children and pregnant people.

A couple of the key health effects included in the assessment are discussed below.

Potential hormonal effects

As part of the risk assessment, Health Canada considered potential hormonal effects including endocrine effects. The review of data re-confirmed that the most sensitive effect atrazine can cause is to suppress luteinizing hormone (LH). Suppression of LH levels is the crucial event of the cascade of changes leading to adverse reproductive and developmental effects. This is why the LH endpoint was used to establish the toxicology reference values for both atrazine and its important metabolites. Uncertainty factors were applied so that the established health reference values are at least 100 times lower than lowest dose levels where no hormone-related effects were seen in laboratory animals. Uncertainty factors are added when studies on laboratory animals are used to make decisions on human health.

More information on how and when uncertainty factors are applied is described in: Science Policy Note: The Application of Uncertainty Factors and the Pest Control Products Act Factor in the Human Health Risk Assessment of Pesticides.

Below is a summary of the information on this important endpoint that was used in the human health risk assessment.

In a laboratory setting, atrazine was given to rats and rabbits to investigate how the pesticide can cause developmental, reproductive, and hormonal effects in the test animals. These studies included dosing animals during critical windows of development, at the expected peak time of hormonal surges, and during puberty.

A 2010 study, conducted by Reproductive Toxicology Division of the National Health and Environmental Effects Research Laboratory of the US Environmental Protection Agency, used the most scientifically complete study design to measure the effects of atrazine on LH suppression. This study was used to establish toxicology reference values.

Potential cancer effects

Review of the data on cancer effects in rats showed that human health is not affected in the same way. Below is an explanation of why cancer effects can look different in laboratory rats when compared to humans.

Health Canada assessed the potential for atrazine to produce tumours in various organs.

Mammary gland tumours were observed in one specific strain of laboratory rat, called Sprague-Dawley (SD), following prolonged exposure to atrazine. There has been in-depth scrutiny by multiple regulatory authorities on this topic. Health Canada also conducted an independent evaluation of all sources of scientific information and data on this matter.

In the rat strain tested, these tumours were caused by suppression of the LH surge. This led to changes in the rat reproductive cycle, which then led to accelerated reproductive aging. Formation of mammary gland tumours is an expected spontaneous event that happens because of reproductive aging in some strains of rats.

However, reproductive aging in humans is brought about by different processes. In humans, reproductive aging is defined by a lower number of egg cells in ovaries, not by suppression of the LH surge. Other than in the SD strain of rats, mammary gland tumours were not observed in any other strains of rats and mice tested. This is how the scientists at Health Canada made the conclusion that there was no evidence to link atrazine with breast cancer effects on human health.

Environment

The environmental risk assessment for atrazine was updated because new information and data were available on how atrazine moves in the environment and how it can harm animals, plants, and microorganisms.

How atrazine enters the environment

In agricultural fields, atrazine breaks down slowly and has the potential to accumulate in soil. Atrazine can leach into soil and can be found in groundwater. Label statements are required to inform users of the potential for atrazine to leach into the ground and contaminate groundwater.

Atrazine can be carried away from fields in water through runoff to nearby aquatic habitats. Studies have shown that less than 2% of applied atrazine is expected to be transported away from the field in runoff. Standard precautionary runoff statements are required on product labels to inform users of the potential for atrazine to travel away from fields in runoff and inform users on how to prevent this from happening.

Potential effects of atrazine on the environment

The large amount of data generated from the scientific study of atrazine and its break-down products shows that these chemicals have the potential to cause harmful effects on animals, plants, and microorganisms in the environment. The environmental risk assessment conducted by Health Canada considered the harm (or toxicity) of atrazine and how algae, plants, birds, mammals, amphibians, fish, insects, and other invertebrates could be exposed. Although some toxicity information is available for the break-down products of atrazine, the data indicates that these metabolites have similar or lower toxicity compared to atrazine itself.

Key environmental effects included in the assessment are discussed here.

Potentials effects of atrazine on terrestrial life

Plants, animals, and other organisms on land could be exposed to atrazine by:

For birds and mammals, the risk assessment shows that there are potential risks for feeding at the site of atrazine application. This risk is expected to be low because of how birds and mammals could be exposed to atrazine in the environment:

For bee larvae, the risk assessment shows the use of atrazine poses a potential risk. This risk is expected to be low because of how bee larvae could be exposed to atrazine in the environment:

For non-target plants, the risk assessment shows there is potential risk of exposure to atrazine from direct overspray and from spray drift at the time of application. Off-field, risks can be mitigated with spray buffer zones, which requires users to leave a certain distance of crop untreated downwind from where the pesticide was applied.

The following spray buffer zones are proposed for atrazine:

The risk assessment shows that the use of atrazine meets the requirements for protection of insects and earthworms.

Lean more about:

Potential effects of atrazine on aquatic life

Plants, animals, and other organisms in water can be exposed to atrazine from spray that drifts into aquatic habitats at the time of application. Spray buffer zones are required to manage risks to aquatic life from spray drift. These organisms can also be exposed to atrazine because it could be applied to an agricultural field and then carried through runoff into a body of water.

For amphibians, the risk assessment shows potential long-term (or chronic) exposure risks. The most sensitive habitats identified are shallow farm ponds and wetlands. The risk is expected to be low based on an in-depth analysis of information and data. Below is a summary of this analysis and assessment.

A total of 17,527 recent surface water samples were analysed for atrazine concentrations in Canada. Of those, 6750 samples were from Ontario and Quebec where most of Canadian corn is produced.

Further analysis was conducted by looking at average concentrations at the 12 sites and comparing these to long-term toxicity of atrazine to amphibians. The available monitoring data showed no chronic risks to amphibians.

The environmental risk assessment considered a large number of water monitoring samples obtained in Canada from 2006 through to 2019. Although the availability of monitoring data for shallow farm ponds and wetlands is limited, the available water monitoring data from these types of sites are consistent with the larger database of data for flowing waterbodies. Recent monitoring data, provided by Environment and Climate Change Canada from shallow waterbodies in corn growing areas of Ontario, are also consistent with the larger water monitoring database showing concentrations do not indicate risks for amphibians.

As part of efforts to provide continuous oversight for registered pesticides in Canada, Health Canada has taken the following actions:

Learn more about:

Actions and next steps

Before making a final special review decision on atrazine, Health Canada will consider all comments and information received from the public in response to the consultation document. A science-based approach will be applied in making a final decision on atrazine. Health Canada will then publish a special review decision document, which will include the decision, the reasons for it, a summary of the comments received on the proposed decision, and Health Canada's response to these comments.

Information Health Canada would like submitted on human health

During the consultation period, Health Canada encourages comments to be submitted on certain key areas, including, but not limited to:

Information Health Canada would like submitted on the environment

During the consultation period, Health Canada encourages the submission of atrazine water monitoring data from shallow waterbodies in corn growing regions in Canada.

How to get involved

This consultation is open for comment from 6 February 2023 to 23 March 2023 (45 calendar days).

To comment on PSRD2023-01:

  1. Request the full consultation document to read the Science Evaluation that is the basis of this proposed regulatory decision.
  2. Submit comments to the PMRA Publications Section.

All comments received will be considered. A final special review decision will consider additional scientific information provided during the public comment period.

Please refer to the document title (for example: PSRD2023-01, Atrazine and Its Associated End-use Products) when providing comments.

Related information

The technical details of related scientific risk assessments and changes to the way atrazine has been used in Canada over the years are in the following list of documents. If you would like to read a document, please visit the publications page and make a request.

Pesticides and pest management consultations:

Decisions and updates:

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