Proposed Re-evaluation Decision PRVD2017-04, Diflufenzopyr-sodium

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Pest Management Regulatory Agency
20 June 2017
ISSN: 1925-0967 (PDF version)
Catalogue number: H113-27/2017-4E-PDF (PDF version)

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Table of Contents

Proposed Re-evaluation Decision for Diflufenzopyr-Sodium

After a re-evaluation of the herbicide diflufenzopyr-sodium, Health Canada’s Pest Management Regulatory Agency (PMRA), under the authority of the Pest Control Products Act and Regulations, is proposing continued registration of products containing diflufenzopyr-sodium for sale and use in Canada.

An evaluation of available scientific information found that products containing diflufenzopyr-sodium do not present unacceptable risks to human health or the environment when used according to the revised label directions. As a requirement of the continued registration of diflufenzopyr-sodium uses, new risk reduction measures are proposed to be included on the labels of all products.

This proposal (PRVD2017-04) affects all end-use products containing diflufenzopyr-sodium registered in Canada.

Proposed Re-evaluation Decision PRVD2017-04, Diflufenzopyr-sodium is a consultation document that summarizes the science evaluation for diflufenzopyr-sodium and presents the reasons for the proposed re-evaluation decision.

The information in Proposed Re-evaluation Decision PRVD2017-04, Diflufenzopyr-sodium is presented in two parts. The Overview describes the regulatory process and key points of the evaluation, while the Science Evaluation provides additional technical information on the assessment of diflufenzopyr-sodium.

The PMRA will accept written comments on PRVD2017-04, Diflufenzopyr-sodium up to 90 days from the date of publication of PRVD2017-04. Please forward all comments to Publications.

What Does Health Canada Consider When Making a Re-evaluation Decision?

The PMRA pesticide re-evaluation program considers potential risks, as well as value, of pesticide products to ensure they meet modern standards established to protect human health and the environment.

What is Diflufenzopyr-sodium?

Diflufenzopyr-sodium is a post-emergent herbicide which is applied using ground application equipment to field corn, non-cropland, fallow cropland, pasture and rangeland for the control of broadleaf weeds. Diflufenzopyr-sodium inhibits the transport of naturally occurring auxin and synthetic auxin-like compounds in plants.

Health Considerations

Can Approved Uses of Diflufenzopyr-Sodium Affect Human Health?

Diflufenzopyr-sodium is unlikely to affect your health when used according to the revised label directions.

People could be exposed to diflufenzopyr-sodium by working as a mixer/loader/applicator, by entering treated sites, or by consuming food and water. The PMRA considers two key factors when assessing health risks:

  • the levels at which no health effects occur and
  • the levels to which people may be exposed.

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 exposure is well below levels that cause no effects in animal testing are considered acceptable for continued registration.
Occupational exposures to workers mixing, loading and applying the herbicide using a ground sprayer or handheld sprayer, as well as to workers re-entering treated sites, are not of concern when diflufenzopyr-sodium is used according to the label directions, which include protective measures. Taking into consideration the current use of diflufenzopyr-sodium in Canada, the risk to workers is not a concern.

Residential exposure to diflufenzopyr is not expected based on the use pattern. Dietary exposure to diflufenzopyr-sodium through consumption of food commodities and drinking water is not of concern. Additional label statements are proposed to be added to the product labels to update to the current labelling standard.

Maximum Residue Limits

The Food and Drug 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. Each MRL value defines the maximum concentration in parts per million (ppm) of a pesticide allowed in or on certain foods. Food containing a pesticide residue that is at or below the established MRL does not pose an unacceptable health risk. Canadian MRLs are currently specified for some commodities, as found in the MRL database on the Pesticides and Pest Management portion of the Health Canada website. Residues in all other agricultural commodities, including those approved for treatment in Canada but without a specific MRL, are regulated under subsection B.15.002(1) of the Food and Drugs Regulations, which requires that residues not exceed 0.1 ppm.

No changes are proposed to the current MRLs for diflufenzopyr-sodium.

Environmental Considerations

What Happens When Diflufenzopyr-Sodium is Introduced into the Environment?

Diflufenzopyr-sodium is not expected to pose unacceptable risk to the environment when used according to the proposed label directions.

Diflufenzopyr-sodium can enter the environmental when it is applied as an herbicide to fields. In soil, diflufenzopyr-sodium breaks down quickly and is not expected to persist. In water, diflufenzopyr-sodium mixes readily and breaks down more slowly than in soil. Diflufenzopyr is not expected to enter the air or be transported over long distances. Diflufenzopyr-sodium has properties that indicate that it has a moderate to high potential to be mobile in soils, but because it breaks down quickly in soil, it is unlikely to reach groundwater. Diflufenzopyr is not expected to build-up in the tissues of organisms.

Diflufenzopyr is toxic to non-target plants and aquatic organisms. Updated spray buffer zones are proposed to reduce exposure to non-target plants and aquatic organisms. Updated environmental label statements are required. There are no concerns about diflufenzopyr-sodium or its major breakdown products affecting any other non-target organisms. Diflufenzopyr-sodium is not expected to pose a risk of concern to non-target terrestrial and aquatic species when used according to the proposed label directions.

Value Considerations

What is the Value of Diflufenzopyr-sodium

Diflufenzopyr-sodium is a commonly used post-emergence herbicide in field corn (especially conventional glyphosate intolerant varieties), which is one of the most important arable crops grown in Eastern Canada. In Western Canada, it is a significant component of chemfallow practices and provides an additional weed management option for post-harvest weed control.

Measures to Minimize Risk

Labels of registered pesticide products include specific instructions for use. Directions include risk-reduction measures to protect human health and the environment. These directions must be followed by law. As a result of the re-evaluation of diflufenzopyr-sodium, PMRA is proposing further risk-reduction measures related to the environment for product labels:

  • Buffer zone and label statements to protect non-target terrestrial plants and aquatic organisms.

In addition, the following measures are required to update to the current labelling standard:

  • Restricted-entry interval of 12 hours.
  • Precautionary label statement to minimize bystander exposure from spray drift.
  • Environmental hazard label statements.

What Additional Scientific Information is Required?

No additional data are required.

Next Steps

Before making a final re-evaluation decision on diflufenzopyr-sodium, PMRA will consider any comments received from the public in response to PRVD2017-04, Diflufenzopyr-sodium. A science-based approach will be applied in making a final decision on diflufenzopyr-sodium. PMRA will then publish a Re-evaluation Decision that will include the decision, the reasons for it, a summary of comments received on the proposed decision and the PMRA response to these comments

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