Evaluation Report ERC2014-03, Pyraflufen-ethyl

Pest Management Regulatory Agency
23 October 2014
ISSN: 1911-8082 (PDF version)
Catalogue number: H113-26/2014-3E-PDF (PDF version)

This page is a summary of the Evaluation Report. If you would like more detail, please request the full Evaluation Report.

To obtain an electronic copy of the document, Evaluation Report ERC2014-03, Pyraflufen-ethyl, please contact our publications office.

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

Summary

Table of Contents

Registration Decision for Compound Pyraflufen-ethyl

Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the  Pest Control Products Act and  Regulations, has granted conditional registration for the sale and use of Nufarm Pyraflufen-ethyl Technical and NUP6D 04 Herbicide, containing the technical grade active ingredient pyraflufen-ethyl, to be used on field corn, soybeans and wheat as preseed or pre-emergence application for broadleaf weed control in Canada.

An evaluation of available scientific information found that, under the approved conditions of use, the product has value and does not present an unacceptable risk to human health or the environment.

Although the risks and value have been found acceptable when all risk reduction measures are followed, the applicant must submit additional scientific information as a condition of registration.

This summary describes the key points of the evaluation, while the Science Evaluation of Evaluation Report ERC2014-03, Pyraflufen-ethyl provides detailed technical information on the human health, environmental and value assessments of Nufarm Pyraflufen-ethyl Technical and NUP6D 04 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 (for example, those most sensitive to environmental contaminants). These methods and policies also consider the nature of the effects observed and the uncertainties when predicting the impact of pesticides. For more information on how the PMRA regulates pesticides, the assessment process and risk-reduction programs, please refer to the following:

What Is Pyraflufen-ethyl?

Pyraflufen-ethyl is the active ingredient in the end-use product NUP6D 04 Herbicide. It belongs to the phenylpyrazole chemical family and is a contact herbicide for control or suppression of several emerged broadleaf weeds, specifically lamb's-quarters, redroot pigweed, volunteer canola, dandelion, flixweed, wild buckwheat, kochia and stinkweed, prior to emergence of wheat (spring, durum, and winter), field corn, and soybean. As an inhibitor of protoporphyrinogen oxidase (PPO), pyraflufen-ethyl results in cell membrane destruction and necrosis. The foliage of sensitive plants turns yellow and brown with leaf burn, followed by death of the whole plant.

Pyraflufen-ethyl is classified as a Group 14 herbicide by the Weed Science Society of America and as a Group E herbicide by the Herbicide Resistance Action Committee.

Health Considerations

Can Approved Uses of Pyraflufen-ethyl Affect Human Health?

NUP6D 04 Herbicide, containing pyraflufen-ethyl, is unlikely to affect your health when used according to the proposed label directions.

Potential exposure to pyraflufen-ethyl may occur through the diet (food and water) or when handling and applying the product. When assessing health risks, two key factors are considered:

  • the levels where 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). 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 where 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 technical grade active ingredient pyraflufen-ethyl was of low acute toxicity by the oral, dermal and inhalation routes of exposure. Pyraflufen-ethyl was minimally irritating to the eyes and non-irritating to the skin, and did not elicit an allergic skin reaction. Consequently, these findings do not trigger a requirement for hazard labelling.

The end-use product NUP6D 04 Herbicide, containing pyraflufen-ethyl, was of low acute toxicity via the oral, dermal and inhalation routes of exposure. It did not cause an allergic skin reaction. It was severely irritating to the eyes and extremely irritating to the skin. Consequently, the hazard signal words "DANGER - CORROSIVE TO EYES AND SKIN" are required on the label.

In laboratory animals given daily oral doses of pyraflufen-ethyl over a long period of time, effects on the liver, kidney, and blood forming system were observed. Pyraflufen-ethyl did not cause cancer in the rat and did not damage genetic material. It caused an increase in the incidence of liver tumours in the mouse. Pyraflufen-ethyl affected immune response in male rats at a very high dose. Abortions were observed in pregnant rabbits at a dose causing death in the mothers. When pyraflufen-ethyl was given to pregnant or nursing rats, no effects on the developing fetus or juvenile animal were observed at doses that were toxic to the mother, indicating that the young were not more sensitive to pyraflufen-ethyl than the adult animal. Pyraflufen-ethyl did not affect the reproductive system.

The risk assessment protects against the effects of pyraflufen-ethyl by ensuring that the level of human exposure is well below the lowest dose at which these effects occurred in animal tests.

Residues in Water and Food

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

Aggregate dietary intake estimates (food plus drinking water) revealed that the general population and children 1-2 years old, the subpopulation that would ingest the most pyraflufen-ethyl relative to body weight, are expected to be exposed to less than 1% of the acceptable daily intake. Based on these estimates, the chronic dietary risk from pyraflufen-ethyl is not of health concern for all population subgroups.

The lifetime cancer risk from the use of pyraflufen-ethyl on field corn, soybeans and wheat is not of health concern.

Animal studies revealed no acute health effects. Consequently, a single dose of pyraflufen-ethyl is not likely to cause acute health effects in the general population (including infants and children).

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 an unacceptable health risk.

Residue trials conducted throughout the United States, including representative Canadian growing regions, using pyraflufen-ethyl on field corn, soybeans and wheat are acceptable. The MRLs for this active ingredient can be found in the Science Evaluation of Evaluation Report ERC2014-03, Pyraflufen-ethyl.

Occupational Risks from Handling NUP6D 04 Herbicid

Occupational risks are not of concern when NUP6D 04 Herbicide is used according to the label directions, which include protective measures.

Farmers and custom applicators that mix, load or apply NUP6D 04 Herbicidecan come in direct contact with pyraflufen-ethylresidues on the skin. Therefore, the label specifies that anyone mixing/loading and applying NUP6D 04 Herbicidemust wear long pants, a long-sleeved shirt, socks and shoes. In addition, workers mixing and loading must wear chemical resistant gloves, and goggles or a face shield. The label also requires that workers do not enter treated fields for 12 hours after application. Taking into consideration these label statements, the number of applications and the expectation of the exposure period for handlers and workers, health risk to these individuals are not of concern.

For bystanders, exposure is expected to be much less than that for workers and is considered negligible. Therefore, health risks to bystanders are not of concern.

Environmental Considerations

What Happens When Pyraflufen-ethyl Is Introduced Into the Environment?

Pyraflufen-ethyl enters the environment when it is used as an herbicide for control of weeds on a variety of crops. Spray drift from ground applications and run-off from the site of application can enter non-target terrestrial and aquatic habitats. In both soil and water, pyraflufen-ethyl transforms quickly and is not expected to bioaccumulate. The major transformation products formed in soil and/or water are non-persistent to persistent. The major transformation product E-1 does not bioconcentrate in fish and further information is to be submitted regarding bioconcentration of the transformation product E-3. Although pyraflufen-ethyl is not likely to leach to groundwater, some of the major transformation products have the potential to leach through the soil profile and enter groundwater.

Overall, pyraflufen-ethyl and its major transformation products present a negligible risk to pollinators, birds, small mammals and fish (freshwater and marine). However, pyraflufen-ethyl may affect beneficial arthropods, terrestrial plants, freshwater algae and amphibians.

To reduce exposure of terrestrial plants and aquatic organisms, spray buffer zones between sites of application and non-target areas are required. Precautionary label statements will be used to inform users of all risks to the environment and to help reduce the potential for surface runoff.

Value Considerations

What is the Value of NUP6D 04 Herbicide?

NUP6D 04 Herbicide may be applied prior to seeding or emergence of wheat (spring, durum, winter), field corn, and soybean at a rate of 4.5 g a.i./ha in combination with a non-ionic surfactant (NIS) at 0.25% v/v to combat infestations of emerged broadleaf weeds; specifically to control lamb's-quarters and redroot pigweed and to suppress volunteer canola, dandelion, flixweed, wild buckwheat, kochia and stinkweed. NUP6D 04 Herbicide may be applied once per growing season by ground application equipment.

There are several Group 14 herbicides registered for application prior to crop emergence for control of emerged weeds, but none belong to the phenylpyrazole chemical family. The value of NUP6D 04 Herbicide relates to its potential contribution to herbicide resistance management as well as providing growers an additional weed control option within the Group 14 mode of action category.

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 NUP6D 04 Herbicide to address the potential risks identified in this assessment are as follows.

Key Risk-Reduction Measures

Human Health

Because there is a concern with users coming into direct contact with pyraflufen-ethylon the skin or through inhalation of spray mists, anyone mixing, loading and applying NUP6D 04 Herbicidemust wear long pants, a long-sleeved shirt, socks and shoes. In addition, workers mixing and loading must wear chemical resistant gloves, and goggles or a face shield. Standard label statements to protect against drift during application were also added to the label.

Environment

Precautionary statements to protect non-target terrestrial and aquatic organisms and no-spray buffer zones for non-target terrestrial and aquatic habitats are required.

To reduce the potential for runoff of pyraflufen-ethyl to adjacent aquatic habitats, precautionary statements for sites with characteristics that may be conducive to runoff and when heavy rain is forecasted are required.

To reduce the potential build-up of soil transformation products, precautionary label statements will be used.

What Additional Scientific Information Is Being Requested?

Although the risks and value have been found acceptable when all risk-reduction measures are followed, the applicant must submit additional scientific information as a condition of registration. More details are presented in the Science Evaluation of Evaluation Report ERC2014-03, Pyraflufen-ethyl or in the Section 12 Notice associated with these conditional registrations. The applicant must submit the following information within the time frames indicated.

Environment

A bioaccumulation study is being requested for E-3, a transformation product of pyraflufen-ethyl.

Other Information

As these conditional registrations relate to a decision on which the public must be consulted the PMRA will publish a consultation document when there is a proposed decision on applications to convert the conditional registrations to full registrations or on applications to renew the conditional registrations, whichever occurs first.

The test data cited in Evaluation Report ERC2014-03, Pyraflufen-ethyl (in other words, the test data relevant in supporting the registration decision) will be made available for public inspection when the decision is made to convert the conditional registrations to full registrations or to renew the conditional registrations (following public consultation). If more information is required, please contact the PMRA's Pest Management Information Service by phone (1-800-267-6315) or by e-mail (pmra.infoserv@hc-sc.gc.ca).

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