Proposed Registration Decision PRD2022-05, Prohexadione-calcium and Anuew Plant Growth Regulator

Pest Management Regulatory Agency
3 March 2022
ISSN: 1925-0886 (PDF version)
Catalogue number: H113-9/2022-5E-PDF (PDF version)

Summary

Table of contents

• Proposed Registration Decision for Prohexadione-calcium
• What does Health Canada consider when making a registration decision?
• What is Prohexadione-calcium?
• Health considerations
• Environmental considerations
• Value considerations
• Measures to minimize risk
• Next steps
• Other information

Proposed Registration Decision for Prohexadione-calcium

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 Nufarm Prohexadione Calcium Technical Plant Growth Regulator and Anuew Plant Growth Regulator, containing the technical grade active ingredient prohexadione-calcium, for growth management of the following turfgrass species: Bentgrass, annual and perennial Poa annua, Kentucky bluegrass, perennial ryegrass, tall fescue and fine fescue, growing on golf courses, sod farms, sports fields, municipal sites and cemeteries.

Prohexadione-calcium is currently registered for use on apple, cherry and strawberry. For details, see Regulatory Note REG2006-07, Prohexadione Calcium and Proposed Registration Decision PRD2009-05, Prohexadione Calcium.

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 PRD2022-05, Prohexadione-calcium and Anuew Plant Growth Regulatorprovides detailed technical information on the human health, environmental and value assessments of prohexadione-calcium and Anuew Plant Growth Regulator.

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:

• Protecting Your Health and the Environment
• Pesticide Registration Process
• Pesticide Risk Reduction Program.

Before making a final registration decision on prohexadione-calcium and Anuew Plant Growth Regulator, Health Canada’s PMRA will consider any comments received from the public in response to PRD2022-05. Health Canada will then publish a Registration Decision on prohexadione-calcium and Anuew Plant Growth Regulator, 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 PRD2022-05.

What is Prohexadione-calcium?

Prohexadione-calcium is a plant growth regulator used for growth management of select turfgrass species.

Health considerations

Can approved uses of Prohexadione-calcium affect human health?

Anuew Plant Growth Regulator, containing Prohexadione-calcium, is unlikely to affect your health when used according to label directions.

Potential exposure to prohexadione-calcium 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 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 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 dose levels 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 prohexadione-calcium was of low acute toxicity by the oral, dermal, and inhalation routes of exposure. It was minimally irritating to the eyes and non-irritating to the skin, and did not cause an allergic skin reaction.

The acute toxicity of the end-use product Anuew Plant Growth Regulator containing prohexadione-calcium was low via the oral, dermal and inhalation routes of exposure. It was minimally irritating to the eyes and skin and did not cause an allergic skin reaction.

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 prohexadione-calcium 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 kidneys, decreased body weight, and abortions. There was no evidence of increased sensitivity of the young compared to adult animals. 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.

Risks in residential and other non-occupational environments

Residential risks are not of concern when Anuew Plant Growth Regulator is used according to the proposed label directions and re-entry intervals are observed.

Adults, youth and children golfing or playing on treated turf can come into direct contact with Anuew Plant Growth Regulator residues. Therefore, the label requires that all individuals not enter treated golf courses, sports fields, municipal fields and cemeteries until sprays have dried. Taking into consideration the label statements, number of applications and duration of exposure, risks to individuals golfing and playing on treated turf are not a concern.

Occupational risks from handling Anuew Plant Growth Regulator

Occupational risks are not of concern when Anuew Plant Growth Regulatoris used according to the proposed label directions, which include protective measures.

Workers who mix, load and apply Anuew Plant Growth Regulatoras well as postapplication workers entering freshly treated sites can come in direct contact with Anuew Plant Growth Regulatorresidues on the skin. Therefore, the label specifies that anyone mixing/loading and applying Anuew Plant Growth Regulatormust wear a long-sleeved shirt, long pants, chemical-resistant gloves, shoes and socks.

The label also requires that workers not enter treated fields until sprays have dried, except for sod farms where re-entry is permitted following the restricted-entry interval (REI) of 12 hours. Taking into consideration these label statements, the number of applications and the exposure period for workers, risks to these individuals are not a concern.

To address potential exposure to bystanders, best practice label statements are required to prohibit the presence of individuals in the treated area during application and to minimize human exposure from spray drift.

Environmental considerations

What happens when Anuew Plant Growth Regulator is introduced into the environment?

When Anuew Plant Growth Regulator, containing prohexadione-calcium, is used according to the label, the risks to the environment are acceptable.

Prohexadione-calcium is not expected to build-up in the environment, and toxicity to non-target organisms is expected to be low. When used as per the label directions, the product Anuew Plant Growth Regulator is expected to pose acceptable risks to the environment.

Value considerations

What is the value of Anuew Plant Growth Regulator?

Anuew Plant Growth Regulator is a plant growth regulator used for slowing vertical growth, reducing mowing frequency and enhancing colour and quality of select turfgrass species growing on golf courses, sod farms, sports fields, municipal sites and cemeteries.

Anuew Plant Growth Regulator will serve as an additional option for turfgrass growth management and align with an option that is presently available to users in the United States.

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 Anuew Plant Growth Regulator 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 Anuew Plant Growth Regulatoron the skin or through inhalation of spray mists, anyone mixing, loading and applying Anuew Plant Growth Regulatormust wear a long-sleeved shirt, long pants, chemical-resistant gloves, shoes and socks. In addition, a restriction from applying in and around homes and a standard label statement to protect against drift during application were added to the label.

Environment

A precautionary label statement stating, “toxic to aquatic plants,” and 1 m aquatic spray buffer zones are required.

Next steps

Before making a final registration decision on prohexadione-calcium and Anuew Plant Growth Regulator, Health Canada’s PMRA will consider any comments received from the public in response to PRD2022-05. Health Canada will accept written comments on this proposal up to 45 days from the date of publication of PRD2022-05. 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 prohexadione-calcium and Anuew Plant Growth Regulator (based on the Science Evaluation of PRD2022-05). In addition, the test data referenced in this consultation document will be available for public inspection, upon application, in the PMRA’s Reading Room. For more information, please contact the PMRA’s Pest Management Information Service.