Proposed Re-evaluation Decision PRVD2016-17, Cyfluthrin


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Pest Management Regulatory Agency
16 September 2016
ISSN: 1925-0967 (PDF version)
Catalogue number: H113-27/2016-17E-PDF (PDF version)

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 Re-evaluation Decision PRVD2016-17, Cyfluthrin please contact our publications office.

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


Table of Contents

General Introduction

In Canada, pesticides are regulated under the Pest Control Products Act, administered by Health Canada's Pest Management Regulatory Agency (PMRA). All pesticides are registered (that is, approved) if a rigorous scientific assessment indicates that the health and environmental risks are acceptable and the products have value. The Pest Control Products Act also contains provisions for post-market reviews of registered pesticides namely, re-evaluation and special reviews, to assess whether pesticides continue to meet Health Canada's health and environmental standards, and whether they can continue to be used in Canada.

As part of the decision making process, before making a final decision, the PMRA consults with the members of the public and other interested stakeholders on all proposed major decisions such as new registrations, re-evaluations and special reviews. The PMRA encourages the public and stakeholders to participate in the consultation process. The proposed decisions are made based on the information available at the time, and the PMRA will consider the comments and information received during consultation using a science-based approach before making a final decision. The final decision will be published on the Pesticides and Pest Management portion of Health Canada's website, and it will include a summary of the comments received during the consultation and PMRA's responses to the comments.

The registration status of products and conditions of use of pesticide products on the market are not impacted by proposed re-evaluation or special review decisions. This may be the case only when final decisions are made. However, at any point during the re-evaluation or special review of a pesticide, the Pest Control Products Act allows the PMRA to cancel or amend the registration of registered pest control products, if there are reasonable grounds to believe this is necessary to deal with a situation that endangers human health or safety or the environment.

Proposed Re-evaluation Decision for Cyfluthrin

An evaluation of available scientific information has determined that under the currently labelled conditions of use, the human health risks estimated for cyfluthrin meet current standards for most uses. As a requirement for the continued registration of cyfluthrin, new risk-reduction measures are proposed for the commercial-class end-use products registered in Canada. Based on potential risks of concern for residential exposure, all domestic-class products are proposed for cancellation and some residential uses are also proposed to be removed. Consideration of any additional data/information submitted during the consultation period to further refine the health risk assessment may or may not result in a change to this proposal.

Proposed Re-evaluation Decision PRVD2016-17, Cyfluthrin is a consultation document that summarizes the science evaluation for cyfluthrin and presents the reasons for the proposed re-evaluation decision.

The information in PRVD2016-17 is presented in two parts. The Overview describes the regulatory process and key points of the evaluation, while the Science Evaluation provides detailed technical information on the assessment of cyfluthrin.

The PMRA will accept written comments on Proposed Re-evaluation Decision PRVD2016-17, Cyfluthrin up to 90 days from the date of publication. Please forward all comments to Publications.

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

The PMRA's 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. Regulatory Directive DIR2012-02, Re-evaluation Program Cyclical Re-evaluation, presents the details of the current re-evaluation approach.

For more details on the information presented in this summary, please refer to the Science Evaluation part of PRVD2016-17, Cyfluthrin.

What Is Cyfluthrin?

Cyfluthrin is a synthetic pyrethroid insecticide. There are two technical grade active ingredients, three commercial class and four domestic class end-use products registered. The commercial class cyfluthrin products, targeting flying and crawling insects, are applied by pest control applicators to residential and commercial sites using hand pressurized and power operated sprayers. They are also applied by farmers to livestock housing structures. The other commercial products are for use by the cattle industry as a pour on to control horn fly and lice, or as an insecticide impregnated ear tag for horn fly control. The domestic products are available as pressurized spray cans for use indoors to target household pests such as ants, earwigs, cockroaches and spiders.

Health Considerations

Can Approved Uses of Cyfluthrin Affect Human Health?

Products containing cyfluthrin are unlikely to affect human health when used according to the proposed revised label directions.

Potential exposure to cyfluthrin may occur through the diet (food and drinking water), when handling and applying products containing cyfluthrin or during 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). 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 at which no effects are observed. The health effects noted in animals occur at doses which are much higher than levels to which humans are normally exposed when pesticide products are used according to label directions. The human health hazard identification for cyfluthrin was based on data for cyfluthrin and beta-cyfluthrin due to the similarity in chemical structure, mode of toxic action and toxicological findings for these two chemicals.

In laboratory animals, the technical grade active ingredients cyfluthrin and beta-cyfluthrin were of high acute toxicity by the oral route. Both chemicals were of low acute dermal toxicity and were moderately acutely toxic through inhalation exposure. Cyfluthrin was mildly irritating to the eyes and non-irritating to the skin whereas beta-cyfluthrin was slightly irritating to the eyes and mildly irritating to the skin. Neither cyfluthrin nor beta-cyfluthrin caused an allergic skin reaction. The findings of the acute oral toxicity testing trigger the requirement for a hazard signal word to appear on the labels of both chemicals.

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 cyfluthrin to cause neurotoxicity, immuno-toxicity, chronic toxicity, cancer, reproductive and developmental toxicity, and various other effects. The most sensitive endpoints for risk assessment were effects on the nervous system and body weight. There is some concern for increased sensitivity of the young exposed to cyfluthrin. There was no evidence of carcinogenicity in mice after longer-term dosing with cyfluthrin; however, an equivocal increase in urinary bladder tumours was noted in female rats. The risk assessment protects against the above-noted effects by ensuring that the level of human exposure is well below the lowest dose at which these effects occur in animal tests.

Residues in Food and Drinking Water

Dietary risks from food and drinking water are not of concern when products containing cyfluthrin are used according to the proposed label directions.

Reference doses define levels to which an individual can be exposed over a single day (acute) or lifetime (chronic) and expect no adverse health effects. Generally, dietary exposure from food and water is acceptable if it is less than 100% of the acute reference dose (ARfD) or chronic reference dose (acceptable daily intake or ADI). An acceptable daily intake is an estimate of the level of daily exposure to a pesticide residue that, over a lifetime, is believed to have no significant harmful effects.

Cyfluthrin is a mixture of four diastereoisomers present in somewhat similar ratios. Beta-cyfluthrin contains the same four diastereoisomer pairs as cyfluthrin; however, the two diastereoisomer pairs considered insecticidally active are enriched in beta-cyfluthrin. Cyfluthrin and beta-cyfluthrin are thus structurally identical, differing only in the ratio of the stereoisomers. Analytical methods for current residue monitoring do not distinguish between cyfluthrin and beta-cyfluthrin; therefore, the dietary risk assessments were conducted by combining the uses of both chemicals. Only cyfluthrin is currently registered in Canada; import maximum residue limits (MRLs) are being proposed for beta-cyfluthrin.

Based on the registered uses for cyfluthrin (and the proposed uses for beta-cyfluthrin outlined in PRD2016-21), residues in drinking water are not anticipated. Therefore, risks from exposure to residues in food only were assessed.

Acute and chronic dietary exposures to cyfluthrin were estimated from residues of cyfluthrin and beta-cyfluthrin in treated crops and animal commodities (including imports). Acute dietary exposure is of concern when considering potential residues in milk and dairy food forms. Therefore, as explained below, for the purposes of risk mitigation, potential residues in milk and dairy food forms were excluded from the dietary exposure assessment.

Acute (probabilistic) and chronic dietary exposures were conducted for the general population and different subpopulations, including children and women of reproductive age. For the general population and all subpopulations, the acute dietary exposure estimates from food only range from 18% to 39% of the ARfD, while the chronic dietary exposure estimates range from 1% to 5% of the ADI. Thus, acute and chronic dietary risks are not of concern provided that cyfluthrin is not applied to lactating cattle.

The Food and Drugs Act prohibits the sale of adulterated food; that is, food containing a pesticide residue that exceeds the specified MRL. Pesticide MRLs are specified for Food and Drugs Act purposes through the evaluation of scientific data under the Pest Control Products Act. An MRL represents the maximum amount of residues that may remain on food when a pesticide is used according to label directions, and serves as a food safety standard. The Canadian Food Inspection Agency is responsible for monitoring the Canadian food supply for pesticide residues and the determination of compliance with MRLs specified by Health Canada.

Canadian MRLs are currently specified for residues of cyfluthrin on animal commodities. MRLs for the importation of all petitioned beta-cyfluthrin uses have been proposed. Residues for cyfluthrin and beta-cyfluthrin in all other agricultural commodities are regulated under Subsection B.15.002(1) of the Food and Drugs Regulations, which requires that residues do not exceed 0.1 ppm. A complete list of MRLs specified in Canada can be found on the PMRA's MRL Database, an online query application that allows users to search for MRLs, regulated under the Pest Control Products Act, both for pesticides or food commodities.

Risks in Residential and Other Non-Occupational Environments

Risks to residential handlers are not of concern.

Residential handler exposure may occur from applying domestic-class products containing cyfluthrin to indoor environments. Residential handler risks are not of concern.

Residential risks from certain postapplication exposures to children are of concern due to potential for incidental oral exposure of cyfluthrin. Mitigation to limit exposure to children is proposed.

Residential postapplication exposure may occur while performing activities in residential areas treated with cyfluthrin. Treated areas include areas treated by residential handlers using domestic-class products, as well as residential areas treated by commercial applicators. Exposure would be dermal and by inhalation. Incidental oral exposure may also occur for children playing in treated areas.

The following postapplication scenarios were assessed: broadcast application, band and spot application, bedbug application, and crack and crevice application. Risks of concern were identified for children from incidental oral exposure for all scenarios except crack and crevice application of commercial-class products. Label directions are proposed to specify that in residential areas, only crack and crevice applications will be permitted. In addition, after consideration of the incident reports involving cyfluthrin, it is also proposed that entry by residents, workers and others will not be permitted until 8 hours after application.

Residential areas are defined as any use site where bystanders including children could be exposed during or after application. This includes homes, schools, public buildings or any other areas where the general public including children could be exposed.

Crack and crevice application is defined as an application of pesticides with the use of a pin stream nozzle, into cracks and crevices in which pests hide or through which they may enter a building. It does not permit the treatment of surfaces. Such openings commonly occur at expansion joints, between different elements of construction, and between equipment and floors. These openings may lead to voids such as hallow walls, equipment legs and bases, conduits, motor housings, and junction or switch boxes.

Therefore, for the commercial-class product containing cyfluthrin currently registered in Canada for residential use, label amendments are proposed to specify that the product must only be applied using low pressure sprayer equipment with a pin stream nozzle to direct sprays into cracks and crevices. Also, the directions for use are proposed to be modified to provide specific directions for crack and crevice applications. In addition, based on potential risks of concern identified for children for most scenarios, and the fact that domestic-class products cannot be applied as crack and crevice only, all domestic-class products are proposed for cancellation.

Aggregate risks are not of concern when the above-noted proposed mitigation is considered.

Aggregate exposure is the total exposure to a single pesticide that may occur from food, drinking water, residential and other non-occupational sources, and from all known or plausible exposure routes (oral, dermal and inhalation)

Aggregate risks are not of concern when cyfluthrin is applied as a crack and crevice spray only in residential areas.

Occupational Risks

Occupational risks to handlers are not of concern when products containing cyfluthrin are used according to the current label directions.

Risk estimates associated with mixing, loading and applying activities are not of concern when current mitigation measures (personal protective equipment, including chemical-resistant gloves and a respirator) are considered.

Occupational postapplication risks to workers are not of concern when products containing cyfluthrin are used according to the proposed label directions.

Occupational postapplication risk assessments for cyfluthrin consider exposures to workers entering treated sites (for example, food processing plants, warehouses, office buildings) and performing various activities. Current uses of cyfluthrin in indoor commercial areas are crack and crevice applications, band and spot applications, and bedbug application. Broadcast application is limited to livestock housing only.

No risks of concern were identified for workers entering treated sites for the current uses, provided that workers do not enter the treated site until 8 hours after application.

Environmental Considerations

What Happens When Cyfluthrin Is Introduced Into the Environment?

When used according to the proposed label directions cyfluthrin is not expected to pose risks of concern to the environment.

Cyfluthrin is used primarily indoors as a domestic and commercial insecticide. Limited outdoor uses include commercial pour-on and ear tag treatments for livestock. As a result of the limited outdoor use pattern, environmental exposure is expected to be minimal.

If cyfluthrin is released into the environment it can enter soil and surface water. Cyfluthrin is moderately persistent in soil, breaking down in the presence of sunlight and microbes. In water, cyfluthrin is non-persistent, being broken down rapidly by sunlight and microbes. Cyfluthrin is not expected to enter the atmosphere and be transported to areas far from where it was used. Laboratory studies indicate that cyfluthrin binds strongly to soil particles. It is not expected to move downward through the soil and enter ground water.

Cyfluthrin poses negligible risk to birds. At high enough doses it can be toxic to mammals, terrestrial and aquatic invertebrates and fish. The potential for terrestrial and aquatic non-target organisms to be exposed to cyfluthrin is expected to be minimal due to the limited outdoor use pattern. As a result, risk to these organisms is not of concern.

Value Considerations

Cyfluthrin has an important role in Integrated Pest Management (IPM) to help manage pests in structural sites. When pesticide treatments are needed, cyfluthrin can be used alone or in conjunction with another insecticide to target pests in specific locations in structural sites. Cyfluthrin, a synthetic pyrethroid, is important for the purpose of resistance management of insect pests in structural sites (residential and commercial sites). Cyfluthrin domestic products are of benefit to the homeowner to use with other control methods, such as prevention and non-chemical treatments, in the management of pests in the home.

Cyfluthrin has an important role in Integrated Pest Management (IPM) to control horn flies and lice on lactating dairy cattle. Cyfluthrin can be used with non-chemical methods in an IPM approach to control horn flies and lice on lactating dairy cattle. Cyfluthrin is one of the few insecticides registered for use on lactating dairy cattle for control of horn flies and lice.

Proposed 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 cyfluthrin, the PMRA is proposing further risk-reduction measures for product labels.

Human Health

To protect homeowners, the following requirements are proposed:

  • All domestic-class products are proposed for cancellation.
  • For the commercial-class products:
    • Application in residential areas to be limited to crack and crevice/void only, and use for bedbug treatment will be cancelled.
    • Application in non-residential areas can be maintained as band, spot, crack and crevice applications, and use for bedbug treatment is allowed.
  • As a result of the incident reports, entry to treated sites must occur no sooner than 8 hours after application.

To protect the general population from dietary exposure, the following requirements are proposed:

  • Use of cyfluthrin on lactating dairy cattle to be prohibited (both spot-on and ear tag products), and MRLs for cyfluthrin in milk and milk fat to be revoked.


Due to the limited outdoor use, the risk to terrestrial and aquatic organisms is expected to be minimal. However, precautionary statements are proposed to further protect the environment.

  • Toxic to aquatic organisms.
  • Toxic to small mammals.

The proposed mitigation measures are outlined in Appendix XI of PRVD2016-17.

What Additional Scientific Information Is Requested?

No additional data are required.

Next Steps

During the consultation period, registrants and stakeholder organizations may submit further data that could be used to refine risk assessments (exposure or use information), which could result in revised risk-reduction measures. Stakeholders who are planning to provide information of this type are advised to contact the PMRA early in the consultation period, for advice on studies or information that could be submitted to help refine the relevant risk assessments.

Before making a final re-evaluation decision on cyfluthrin, the PMRA will consider all comments received from the public in response to PRVD2016-17, Cyfluthrin. The 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's response to these comments.

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