Proposed Registration Decision PRD2020-13, Trinexapac-ethyl and MODDUS

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Pest Management Regulatory Agency
9 September 2020
ISSN: 1925-0886 (PDF version)
Catalogue number: H113-9/2020-13E-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 PRD2020-13, Trinexapac-ethyl and MODDUS please contact our publications office.

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

Table of contents

Proposed registration decision for trinexapac-ethyl

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 Trinexapac-ethyl Technical and MODDUS, containing the technical grade active ingredient trinexapac-ethyl, for use on spring wheat, winter wheat, barley and oat as a plant growth regulator to reduce susceptibility to lodging (falling/leaning over).

Trinexapac-ethyl is currently registered for use on turf. For details, see Proposed Regulatory Decision Document PRDD2001-05, Trinexapac-ethyl, and Regulatory Decision Document RDD2002-01, Trinexapac-ethyl.

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 PRD2020-13, Trinexapac-ethyl and MODDUS provides detailed technical information on the human health, environmental and value assessments of trinexapac-ethyl and MODDUS.

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 trinexapac-ethyl and MODDUS, Health Canada’s PMRA will consider any comments received from the public in response to PRD2020-13 document. Health Canada will then publish a Registration Decision on trinexapac-ethyl and MODDUS, 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 PRD2020-13.

What is trinexapac-ethyl?

Trinexapac-ethyl is a plant growth regulator that inhibits the biosynthesis of gibberellin. Gibberellin is a plant hormone that promotes growth of various plant organs. By inhibiting gibberellin, trinexapac-ethyl treatment reduces plant height thereby reducing the tendency to lean or fall over.

Health considerations

Can approved uses of trinexapac-ethyl affect human health?

MODDUS, containing trinexapac-ethyl, is unlikely to affect your health when used according to label directions.

Potential exposure to trinexapac-ethyl may occur through the diet (food and water) or when handling and applying the end-use product, exposure may also occur 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 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 trinexapac-ethyl was of low acute toxicity by the oral, dermal, and inhalation routes. Trinexapac-ethyl was minimally irritating to the eyes, slightly irritating to the skin and caused an allergic skin reaction; consequently, the hazard statement “POTENTIAL SKIN SENSITIZER” is required on the label.

In laboratory animals, the end-use product MODDUS was of low acute toxicity by the oral, dermal, and inhalation routes. MODDUS was not irritating to the skin and did not cause an allergic skin reaction. MODDUS was moderately irritating to the eyes; consequently, the signal word and hazard statement “WARNING - EYE IRRITANT” 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 trinexapac-ethyl to cause neurotoxicity, immunotoxicity, chronic toxicity, cancer, reproductive and developmental toxicity, and various other effects. The most sensitive endpoints for risk assessment were effects on body weight, effects in the brain, and fetal death. There was an indication that the young were more sensitive than the adult animal. 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 water and food

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

Aggregate acute dietary (food plus drinking water) intake estimates for females 13–49 years of age are expected to be less than 72% of the acute reference dose, and are not of health concern.

Aggregate chronic dietary (food plus drinking water) intake estimates for all population subgroups are expected to be less than 47%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 an unacceptable health risk.

MRLs for trinexapac-ethyl determined from the acceptable residue trials conducted throughout Canada and the United States on wheat and barley can be found in the Science Evaluation of PRD2020-13.

Occupational risks from handling MODDUS

Occupational risks are not of concern when trinexapac-ethyl is used according to the proposed label directions, which include protective measures.

Farmers and custom applicators who mix, load or apply MODDUS as well as field workers entering recently treated fields of wheat (spring, durum and winter), barley and oats can come in direct contact with trinexapac-ethyl residues on the skin and through inhalation. Therefore, the label specifies that handlers mixing/loading and applying MODDUS must wear coveralls over long-sleeved shirt, long pants, chemical-resistant gloves, shoes and socks (gloves are not required inside a closed cab or cockpit) as well as goggles during mixing and loading.

The label also requires that workers do not enter treated fields of wheat (spring, durum and winter), barley and oats 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, the health risk to these individuals are not of concern.

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

A standard label statement to protect against drift during application is on the label. Therefore, health risks to bystanders are not of concern.

Environmental considerations

What happens when trinexapac-ethyl is introduced into the environment?

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

Trinexapac-ethyl is a plant growth regulator and can enter the environment when applied as a foliar spray to reduce height and susceptibility to lodging in cereal crops (in other words, wheat, barley and oat). It is expected to move inside the plants and inhibit the growth of leaves and stems. Trinexapac-ethyl is not expected to move through the soil and reach groundwater however, its transformation product, trinexapac acid, has a potential to persist and accumulate and can move through the soil and reach groundwater. In water bodies, trinexapac-ethyl and its breakdown products are not persistent and are not expected to move to sediments. Trinexapac-ethyl is not expected to be found in the air or to travel long distances from where it was applied. Trinexapac-ethyl and trinexapac acid are not expected to build-up in the tissues of organisms.

When trinexapac-ethyl is used in accordance with the label and the required precautions, the environmental risk is acceptable.

Value considerations

What is the value of MODDUS?

MODDUS is used to reduce height and lodging of wheat, barley and oat crops thereby maximizing harvestable yield.

Lodging can reduce photosynthesis and carbohydrate movement within plants, which contributes to uneven maturity, increased likelihood of the development of diseases on foliage and grain, reduced grain yield and quality as well as a reduction in the efficiency of the harvesting operation. MODDUS represents a new active ingredient that may be used as a crop growth management aid to reduce height and lodging in wheat and barley and is the only one available for use in oat.

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 Trinexapac-ethyl Technical and MODDUS 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 trinexapac-ethyl on the skin or through inhalation of spray mists, anyone mixing, loading and applying MODDUS must wear coveralls over long-sleeved shirt, long pants, chemical-resistant gloves, shoes and socks (gloves are not required inside a closed cab or cockpit) as well as goggles during mixing and loading. The label also requires that workers do not enter treated fields of wheat (spring, durum and winter), barley and oats for 12 hours after application. In addition, standard label statements to protect against drift during application are present on the label.

Environment

To protect the environment, the following risk mitigation measures are being proposed:

Next steps

Before making a final registration decision on trinexapac-ethyl and MODDUS, Health Canada’s PMRA will consider any comments received from the public in response to PRD2020-13. Health Canada will accept written comments on PRD2020-13 up to 45 days from the date of publication of PRD2020-13. 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 the Health Canada makes its registration decision, it will publish a Registration Decision on trinexapac-ethyl and MODDUS (based on the Science Evaluation of PRD2020-13). In addition, the test data referenced in PRD2020-13 will be available for public inspection, upon application, in the PMRA’s Reading Room (located in Ottawa).

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