Proposed Registration Decision PRD2021-04, Pyridate and Tough 600 EC Herbicide

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Pest Management Regulatory Agency
6 July 2021
ISSN: 1925-0886 (PDF version)
Catalogue number: H113-9/2021-4E-PDF (PDF version)

Summary

This page is a summary of the consultation document. If you would like to comment, please request the full consultation document.

To obtain a full copy of Proposed Registration Decision PRD2021-04, Pyridate and Tough 600 EC Herbicide please contact our publications office.

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

Table of contents

Proposed registration decision for pyridate

Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the Pest Control Products Act, is proposing registration for the sale and use of Pyridate Technical and Tough 600 EC Herbicide, containing the technical grade active ingredient pyridate, for selective suppression or control of certain emerged broadleaf weeds. Tough 600 EC Herbicide may be applied pre-plant and/or pre-emergence in corn (field and sweet), mint, chickpeas, lentils, field peas and canola, and post-emergence in corn (field and sweet), chickpeas and mint.

Pyridate was previously registered by the PMRA between 1990 and 2002 (Decision Document E91-01, Pyridate Herbicide). This represents a new registration for pyridate and its associated end-use product.
An evaluation of available scientific information found that, under the approved conditions of use, the health and environmental risks and the value of the pest control products are acceptable.

This Summary describes the key points of the evaluation, while the Science Evaluation of Proposed Registration Decision PRD2021-04, Pyridate and Tough 600 EC Herbicide provides detailed technical information on the human health, environmental and value assessments of pyridate and Tough 600 EC Herbicide.

What does Health Canada consider when making a registration decision?

The key objective of the Pest Control Products Act is to prevent unacceptable risks to people and the environment from the use of pest control products. Health or environmental risk is considered acceptable if there is reasonable certainty that no harm to human health, future generations or the environment will result from use or exposure to the product under its proposed conditions of registration. The Act also requires that products have value when used according to the label directions. Conditions of registration may include special precautionary measures on the product label to further reduce risk.

To reach its decisions, the PMRA applies modern, rigorous risk-assessment methods and policies. These methods consider the unique characteristics of sensitive subpopulations in humans (for example, children) as well as organisms in the environment. These methods and policies also consider the nature of the effects observed and the uncertainties when predicting the impact of pesticides.
For more information please refer to the following:

Before making a final registration decision on pyridate and Tough 600 EC Herbicide, Health Canada's PMRA will consider any comments received from the public in response to PRD2021-04. Health Canada will then publish a Registration Decision on pyridate and Tough 600 EC Herbicide, which will include the decision, the reasons for it, a summary of comments received on the proposed registration decision and Health Canada's response to these comments.

For more details on the information presented in this Summary, please refer to the Science Evaluation of PRD2021-04.

What is pyridate?

Pyridate is a contact herbicide that inhibits photosynthesis in plants. Pyridate is to be used alone or in combination with other herbicides for selective suppression or control of certain emerged broadleaf weeds either prior to planting or in labelled crops.

Health considerations 

Can approved uses of pyridate affect human health?

Tough 600 EC Herbicide, containing pyridate, is unlikely to affect your health when used according to label directions.

Potential exposure to pyridate may occur through the diet (food and drinking water), when handling and applying the end-use product, or when coming into contact with treated surfaces. When assessing health risks, two key factors are considered:

The dose levels used to assess risks are established to protect the most sensitive human population (for example, children and nursing mothers). As such, sex and gender are taken into account in the risk assessment. Only uses for which the exposure is well below levels that cause no effects in animal testing are considered acceptable for registration.

Toxicology studies in laboratory animals describe potential health effects from varying levels of exposure to a chemical and identify the dose level at which no effects are observed. The health effects noted in animals occur at doses more than 100-times higher (and often much higher) than levels to which humans are normally exposed when pesticide products are used according to label directions.

In laboratory animals, the acute toxicity of the technical grade active ingredient pyridate was low by the oral, inhalation and dermal routes. Pyridate was minimally irritating to the eyes. It was mildly irritating to the skin and caused an allergic skin reaction; consequently, the signal word “CAUTION” and the hazard statements “SKIN IRRITANT” and “POTENTIAL SKIN SENSITIZER” are required on the label.

The acute toxicity of the end-use product, Tough 600 EC Herbicide containing pyridate, was low via the oral, dermal and inhalation routes of exposure. It was moderately irritating to the eyes and skin and caused an allergic skin reaction; consequently, the signal word “WARNING” and the hazard statements “EYE AND SKIN IRRITANT” and “POTENTIAL SKIN SENSITIZER” are required on the label.

Registrant-supplied short- and long-term (lifetime) animal toxicity tests, as well as information from the published scientific literature, were assessed for the potential of pyridate to cause neurotoxicity, chronic toxicity, cancer, reproductive and developmental toxicity, and various other effects. The most sensitive endpoints for risk assessment were effects on body weight and neurobehavioural changes. There was no evidence to suggest that pyridate damaged genetic material. Pyridate caused benign liver tumours in one mouse study; however, the concern for these tumours and the overall concern for carcinogenicity is low. There was an indication that the young were more sensitive than adult animals in one rabbit study in which non-serious effects were observed in the absence of maternal toxicity. The risk assessment protects against the effects noted above and other potential effects by ensuring that the level of exposure to humans is well below the lowest dose at which these effects occurred in animal tests.

Residues in food and drinking water

Dietary risks from food and drinking water are not of health concern.

Aggregate acute dietary (food plus drinking water) intake estimates for the general population and all population subgroups are expected to be less than 21% of the acute reference dose, and are not of health concern.

Aggregate chronic dietary (food plus drinking water) intake estimates for the general population and all population subgroups are expected to be less than 43%of the acceptable daily intake, and are not of health concern.

The Food and Drugs Act prohibits the sale of adulterated food, that is, food containing a pesticide residue that exceeds the established maximum residue limit (MRL). Pesticide MRLs are established for Food and Drugs Act purposes through the evaluation of scientific data under the Pest Control Products Act. Food containing a pesticide residue that does not exceed the established MRL does not pose a health risk of concern.

MRLs for pyridate determined from the acceptable residue trials conducted throughout Canada, the United States and Austria on field corn, sweet corn, mint, chickpeas, lentils, dry field peas and canola can be found in the Science Evaluation of this document.

Occupational risks from handling Tough 600 EC Herbicide

Occupational risks are not of health concern when Tough 600 EC Herbicideis used according to the proposed label directions, which include protective measures.

Workers mixing, loading or applying Tough 600 EC Herbicide, and workers entering recently treated fields can come in direct contact with pyridate residues on the skin and through inhalation. Therefore, the label specifies to wear protective eyewear (goggles or face shield) during all mixing and loading activities. In addition, anyone mixing, loading, applying, or performing clean-up and repair activities with up to 448 L per day of Tough 600 EC Herbicide must wear coveralls over a long-sleeved shirt, long pants, socks, chemical-resistant footwear and chemical-resistant gloves. When mixing, loading, applying, or performing clean-up and repair activities with more than 448 L of product per day, workers must wear chemical-resistant coveralls over a long-sleeved shirt, long pants, socks, chemical-resistant footwear and chemical-resistant gloves. When applying more than 500 L product per day, a closed-cab tractor is required. Gloves are not required when applying within a closed-cab tractor.

The label also requires that workers do not enter or be allowed into treated fields during the preharvest intervals (PHIs) or the restricted-entry intervals (REIs) as specified in Appendix I, Table 9.

Taking into consideration the label statements, the number of applications and the duration of exposure for handlers and postapplication workers, the risks to these individuals are not of health concern.

Health risks in residential and other non-occupational environments

As Tough 600 EC Herbicide is a commercial agricultural end-use product, a residential exposure assessment is not required.

Health risks to bystanders

Bystander risks are not of health concern when Tough 600 EC Herbicideis used according to the proposed label directions and spray drift restrictions are observed.

Environmental considerations

What happens when pyridate is introduced into the environment?

When used according to label directions, the risks associated with pyridate are acceptable from the viewpoint of environmental protection.

When pyridate is used as a ground spray application to control herbicides, it rapidly breaks down in the presence of water and moisture to the major transformation product, pyridafol, and does not remain in the environment. Pyridate and pyridafol will not move from the treatment area to the air, and, therefore, will not be transported to another area through the air or atmosphere. Pyridafol can remain in the environment and move downward in the soil and reach groundwater. Pyridafol can also move off the treatment area to reach surface waters such as ponds, streams, and rivers. However, there is no known toxicity of pyridafol to terrestrial or aquatic life. Pyridate and its breakdown products are not expected to accumulate in animal tissues.

Pyridate can affect pollinators, non-target terrestrial plants, and small wild mammals following application. Pyridate can also affect some aquatic life if it enters ponds, streams, or rivers after it is sprayed. Precautions and no-spray buffer zones are required to reduce environmental exposures to pyridate. When pyridate is used in accordance with the label and the required precautions, the resulting environmental risk is considered to be acceptable.

Value considerations

Tough 600 EC Herbicide provides suppression or control of certain emerged annual broadleaf weeds in agricultural settings.

What is the value of Tough 600 EC Herbicide?

Tough 600 EC Herbicide provides suppression or control of certain emerged annual broadleaf weeds and has good tank mix flexibility for use in field and sweet corn. It has activity on important weeds present in agricultural systems. Control of broadleaf weeds with Tough 600 EC Herbicide in mint has been identified as a priority by Canadian growers.

The registration of Tough 600 EC Herbicide would provide Canadian growers with access to a product that is currently available in the United States for similar uses. Tough 600 EC Herbicide also has a new mode of action for managing weeds in mint. Tough 600 EC Herbicide may be particularly useful in managing weeds that have developed resistance to other modes of action when used in tank mix with other herbicides.

Measures to minimize risk

Labels of registered pesticide products include specific instructions for use. Directions include risk-reduction measures to protect human and environmental health. These directions must be followed by law.

The key risk-reduction measures being proposed on the label of Pyridate Technical and Tough 600 EC Herbicide to address the potential risks identified in this assessment are as follows.

Key risk-reduction measures

Human health

To reduce the potential of workers coming into direct contact with pyridateon the skin or through inhalation, workers mixing, loading and applying Tough 600 EC Herbicideand performing cleaning and repair activities must wear personal protective equipment as specified below.

Wear protective eyewear (goggles or face shield) during mixing and loading. In addition, wear coveralls over a long-sleeved shirt, long pants, socks, chemical-resistant footwear and chemical-resistant gloves while mixing, loading, applying, or performing clean-up and repair activities with up to 448 L product per day. When mixing, loading, applying or performing clean-up and repair activities with more than 448 L product per day, wear chemical-resistant coveralls over a long-sleeved shirt, long pants, socks, chemical-resistant footwear and chemical-resistant gloves. When applying more than 500 L product per day, a closed-cab tractor is required. Gloves are not required when applying within a closed-cab tractor.

Risks to workers are not of health concern when Tough 600 EC Herbicide is used according to the proposed label directions and when adhering to restricted-entry intervals (REIs) as specified in Appendix I, Table 9.

Furthermore, a standard label statement to protect against drift during application is present on the label.

Environment

Next steps

Before making a final registration decision on pyridate and Tough 600 EC Herbicide, Health Canada's PMRA will consider any comments received from the public in response to PRD2021-04. Health Canada will accept written comments on this proposal up to 45 days from the date of publication of PRD2021-04. Please note that, to comply with Canada's international trade obligations, consultation on the proposed MRLs will also be conducted internationally via a notification to the World Trade Organization. Please forward all comments to Publications. Health Canada will then publish a Registration Decision, which will include its decision, the reasons for it, a summary of comments received on the proposed decision and Health Canada's response to these comments.

Other information

When Health Canada makes its registration decision, it will publish a Registration Decision on pyridate and Tough 600 EC Herbicide (based on the Science Evaluation of PRD2021-04). In addition, the test data referenced in PRD2021-04 will be available for public inspection, upon application, in the PMRA's Reading Room.

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