Proposed Re-evaluation Decision PRVD2017-18, Permethrin and Its Associated End-use Products

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The online consultation is now closed.

The online consultation is now closed.
The online consultation is now closed.
The online consultation is now closed.
The online consultation is now closed.
The online consultation is now closed.

Pest Management Regulatory Agency
19 October 2017
ISSN: 1925-0967 (PDF version)
Catalogue number: H113-27/2017-18E-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 PRVD2017-18, Permethrin and Its Associated End-use Products please contact our publications office.

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


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 postmarket 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, and it will include a summary of the comments received during the consultation and the 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 Permethrin

An evaluation of available scientific information has determined that under the proposed conditions of use, the human health and environmental risks estimated for permethrin meet current standards for most uses. As a requirement for the continued registration of permethrin, new risk-reduction measures are proposed for certain commercial-class end-use products registered in Canada. Additionally, the following uses are proposed for cancellation due to lack of data to assess their risks to human health:

  • Use in mushroom houses
  • Application using foggers and hand-held mist sprayers/blowers
  • Application of domestic-class products using foggers, hand-held mist sprayers/blowers

Any additional data/information submitted during the consultation period to further refine the health risk assessment will be considered, and may or may not result in a change to this proposal.

This Proposed Re-evaluation Decision (PRVD2017-18) is a consultation document that summarizes the science evaluation for permethrin and presents the reasons for the proposed re-evaluation decision.

This consultation document (Proposed Re-evaluation Decision PRVD2017-18, Permethrin and Its Associated End-use Products) 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 permethrin.

The PMRA will accept written comments on this proposal up to 90 days from the date of publication of PRVD2017-18. 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 DIR2016-04, Management of Pesticides Re-evaluation Policy 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 of PRVD2017-18.

What Is Permethrin?

Permethrin is a broad spectrum synthetic pyrethroid insecticide. It is registered for use on a wide range of crops including grains and oilseeds, legumes, horticultural crops, mushroom houses, ginseng, greenhouse and field grown ornamentals as well as tobacco. It is also registered for use on livestock, companion animals, forestry and woodlots, feedlots, termite treatment, pet premises, kennels, indoors and outdoors of homes, agricultural, commercial and institutional building, military clothing, mosquito netting and to soil around honey bee hives.

Permethrin end-use products are applied by farmers, farm workers and professional applicators using conventional aerial and ground equipment on crops and pour-ons, ear tags and in backrubbers for livestock. Permethrin end-use products are also applied by pest control operators using typical application equipment; and by the general public as spot-on, treated collars, spray, powder and shampoo treatments on companion animals, and ready to use and pressurized spray cans for use indoors and outdoors. The PMRA plans to publish a document in the future providing a broader examination of spot-on products for pets.

Health Considerations

Can Approved Uses of Permethrin Affect Human Health?

Additional risk-reduction measures are required on labels of products containing permethrin. Products containing permethrin are unlikely to affect your health when used according to the proposed label directions.

Exposure to permethrin may occur through the diet (food and drinking water), when handling and applying end-use products containing permethrin or when entering or contacting treated sites. When assessing health risks, two key factors are considered:

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

The dose levels used to assess risk are established to protect the most sensitive human population (that is, 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 the 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 more than 100-times higher (and often much higher) than levels to which humans are normally exposed when pesticide-containing products are used according to label directions.

In laboratory animals, technical grade active ingredient permethrin was highly acutely toxic via the oral route. It was of low acute toxicity by the dermal and inhalation routes, was minimally irritating to the eyes and mildly irritating to the skin. In one of two animal studies, permethrin demonstrated an allergic skin reaction. Transient itching, burning, tingling or numbness of the skin has been noted in humans exposed dermally to permethrin.

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 permethrin 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 the nervous system, the liver and on body weight. Following extended dosing, benign lung tumors in mice and liver and thyroid tumors were seen in rats. There is evidence of sensitivity of the young when directly exposed to permethrin. The risk assessment protects against the effects of permethrin by ensuring that the level of human exposure is well below the lowest dose at which these effects occurred in animal tests.

Pesticide Residues in Food and Drinking Water

Dietary risks from food and drinking water are not of concern when products containing permethrin 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 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. For the cancer assessment, a lifetime cancer risk that is less than one-in-a-million (1 × 10-6) is generally considered an acceptable risk for the general population when exposure occurs through pesticide residues in/on food and drinking water, and to otherwise unintentionally exposed persons.

The dietary assessment for permethrin included the potential for exposure to permethrin residues in treated crops and animal commodities (including imports), and drinking water for the general population and different subpopulations, including children and women of reproductive age.

The acute, chronic and cancer dietary exposure estimates were based mostly on monitoring data and included experimental processing factors when available. Field trial data and maximum residue limits (MRLs) were also used for commodities where monitoring data were not available. In addition, for the chronic and cancer assessments, domestic/import statistics and percent crop treated information were used, where available. Estimated environmental concentrations (EECs) in drinking water were based on the modelling of permethrin residues in surface and ground water using the application rates for tomato, as this crop had the highest annual application rate across Canada.

The acute dietary exposure (from food and drinking water) estimates at the 95th percentile were at or below 16% of the acute reference dose for all subpopulations, with children 1-2 years old being the highest exposed subpopulation. The chronic non-cancer dietary exposure estimates to permethrin from food and drinking were below 2% of the acceptable daily intake for all subpopulations with infants (< 1 year old) being the highest exposed subpopulation. The dietary cancer assessment based on the current use pattern indicated that cancer dietary risk from exposure to permethrin may be of concern. However, when mitigation measures are considered for existing uses (in other words, five applications are proposed for use on tomato instead of the six applications stated on the current labels.), the cancer risk from food and drinking water exposure is estimated as being at the threshold of acceptability (1 × 10-6) for the general population and thus, is not of concern.

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. Each MRL value defines the maximum concentration as parts per million (ppm) of a pesticide allowed in or on certain foods 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 for permethrin are currently specified for a wide range of commodities. 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 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 specified MRLs, regulated under the Pest Control Products Act, for pesticides or food commodities.

Risks in Residential and Other Non-Occupational Environments from Permethrin

Risks to residential handlers are not of concern for most uses when permethrin is used according to the proposed label directions.

Residential exposure may occur from the application of domestic class products containing permethrin to residential lawns, gardens and trees, outdoor and indoor environments, and pets. These products can be applied by manually pressurized handwand, aerosol can, trigger spray bottles, and spot-on treatments (pets).

For all domestic class products, no risks of concern were identified for most scenarios of individuals applying permethrin. However, no data were available to assess exposure when using hand-held mist sprayers/blowers and foggers. Therefore, products that need to be applied using this equipment are proposed for cancellation. For other products that could be applied using this equipment, label directions are proposed prohibiting application with these types of equipment.

Non-occupational risks for residential postapplication exposure are not of concern for most uses when permethrin is used according to the proposed label directions.

Residential postapplication exposure may occur while performing activities in treated areas. Treated areas include those treated by residential handlers as well as residential areas treated by commercial applicators. Exposure would be predominantly by dermal and inhalation routes. Incidental oral exposure may also occur for young children playing in treated areas or in contact with treated pets.

For most residential postapplication activities no risks of concern were identified for any population, provided mitigation measures, such as lower application rates, are implemented. Risks of concern were identified for postapplication exposure after indoor solid fogger application and indoor broadcast application. These uses are proposed for cancellation as mitigation is not considered to be feasible. For incidental oral exposure, no risks of concern were identified for young children.

Incidental oral, dermal and inhalation scenarios, when applicable, were aggregated with background (chronic) dietary exposure (food and drinking water). The aggregate cancer risk was determined using biomonitoring data. The calculated cancer risk was slightly above the threshold of acceptability. However, when considering the proposed mitigation measures, the conservatisms and uncertainties associated with use of biological monitoring data, and the degree to which the cancer threshold was exceeded, the aggregate cancer risk was considered to be not of concern.

Occupational Risks from Permethrin

Occupational risks to handlers are not of concern for most uses when permethrin is used according to the proposed label directions.

Occupational handler risk assessments consider exposure to workers applying permethrin in agricultural, commercial, and residential sites, and to military clothing. No risks of concern were identified for most of the commercial applicator scenarios in agricultural, commercial, and residential sites and for military clothing using baseline personal protective equipment. As such, no mitigation measures are required for these scenarios. Mitigation measures, such as additional personal protective equipment, are proposed for applicators using mechanically pressurized handgun and airblast equipment. No data were available to assess exposure when using foggers and hand-held mist blowers. Label statements are proposed to prohibit application using these types of equipment.

Risks to commercial applicators using spot-on products on pets were assumed to be similar to or less than residential application risks for this same use scenario. No risks of concern were identified for residential application of spot-on treatments on pets.

No risks of concern were identified for the industrial treatment of wood using a linear system.

Occupational risks for postapplication workers are not of concern for most uses when permethrin is used according to the proposed label directions.

Occupational postapplication risk assessments consider exposures to workers entering treated agricultural and residential sites, and military personnel wearing treated uniforms. Based on the current use pattern for permethrin, risks to workers performing agricultural activities, such as thinning, pruning and harvesting of all crops, meet current standards and are not of concern for most scenarios, provided mitigation measures such as restricted-entry intervals are implemented. The restricted-entry intervals required to mitigate agricultural postapplication risk range from 0.5–15 days. No risks of concern were identified for military personnel wearing treated military uniforms.

Postapplication exposure following livestock treatment is expected to be minimal. Postapplication exposure in feedlots is expected to be low due to the lack of postapplication activities where workers may come in contact with treated surfaces.

There is potential for postapplication exposure in mushroom houses. Currently, there are no data to estimate exposure to workers entering treated mushroom houses. No data are available to also determine transferable residues of permethrin from treated surfaces, or air concentrations after application. Therefore, a postapplication exposure assessment could not be conducted for mushroom houses. Thus the use is proposed for cancellation.

Risks for postapplication workers in residential areas were assumed to be similar to or less than residential postapplication risks for this same use scenario. No risks of concern were identified for residential postapplication scenarios provided that measures required to mitigate residential postapplication risk are implemented.

Environmental Considerations

What Happens When Permethrin Is Introduced into the Environment?

Permethrin is not expected to pose a risk of concern when used according to proposed label directions. Permethrin may pose a risk to aquatic organisms, bees, beneficial insects and birds; therefore, preventative measures to reduce risk to these organisms are proposed. When proposed label directions are followed, the risks are considered acceptable.

When permethrin is released into the environment, it can enter soil and surface water where it can persist under certain conditions. In soil, permethrin binds strongly to soil particles, making it unlikely to move downward in the soil and reach groundwater. In aquatic environments, permethrin rapidly moves out of water and into sediment where it can persist. Permethrin is unlikely to persist in air or move in air to remote locations such as the arctic. Permethrin is not likely to accumulate to levels of concern in the tissues of organisms, such as fish.

In terrestrial environments, permethrin can pose a potential risk to bees and other pollinators, as well as beneficial insects and birds if they are exposed to high enough levels of this pesticide. The risk to bees can be reduced by restricting or prohibiting the application of permethrin during the crop blooming period. The risk to beneficial insects living in habitats adjacent to the application site may be reduced by minimizing spray drift. Precautionary label statements are proposed on permethrin product labels to inform users of the potential hazard to bees, beneficial insects and birds and indicate the risk reduction measures that must be followed.

In aquatic environments, water modelling indicates that permethrin may be found at concentrations that pose risks of concern to aquatic invertebrates, fish and amphibians. Canadian water monitoring information confirms that, although rarely detected, permethrin can be found in aquatic environments at concentrations that would be expected to pose risks to aquatic invertebrates, fish and amphibians. Spray buffer zones are therefore proposed to protect aquatic organisms from spray drift. To reduce the risks of permethrin being carried in runoff to aquatic environments, in addition to precautionary label statements, a mandatory requirement for the construction and maintenance of a 10 m vegetative filter strip between the area of application and waterbodies is proposed.

Value Considerations

What is the value of permethrin?

Permethrin has one of the broadest use patterns for the synthetic pyrethroids. It contributes to resistance management by helping delay the development of resistance when used in rotation with other insecticides with different modes of action. Permethrin has a role in an integrated pest management approach for pests in structural sites. It is used by professional pest control applicators in residential settings to treat for bedbugs and fleas. Domestic products containing permethrin are registered for use against a broad spectrum of pests, such as ants, cockroaches and fleas. These products are of benefit for homeowner use along with other control methods, such as prevention and non-chemical treatments, in the management of pests in and around the home. Various types of domestic permethrin products are used to control fleas, ticks, mosquitoes and lice on dogs.

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 permethrin, the PMRA is proposing the following risk-reduction measures for product labels:

Human Health

  • Cancellation of use in mushroom houses due to lack of data to assess this use.
  • Cancellation of certain application types (fogger, handheld mist blower/airblast) due to lack of data to assess these application types, and cancellation of other application types (indoor broadcast, indoor solid fogger).
  • A 60-day plant-back interval for all non-registered agricultural food/feed crops.
  • For agricultural uses a restricted-entry interval of 12 hours for most crops and activities, and a longer interval for certain crops and activities (for example, hand-harvesting of grapes and sweet corn).
  • The number of applications on tomato per year to be reduced from six to five applications.
  • Additional personal protective equipment requirements for all agricultural product labels as well as all mechanically pressurized handgun applications, mosquito abatement truck mounted mist blower and airblast applications, and wood treatment in enclosed linear systems.
  • The rate for application to lawns and turf is proposed to be limited to the lower registered rate of 0.123 g a.i./m2.
  • Additional label statements to minimize human exposure from spray drift or spray residues for domestic and commercial products used in residential areas.


  • Environmental hazard statements for bees, beneficial insects, birds and aquatic organisms.
  • To reduce risk to pollinators, application is to be restricted or prohibited during the crop blooming period.
  • Label directions to minimize spray drift in order to reduce risk to beneficial insects living in habitats adjacent to the application site.
  • Spray buffer zones for non-target aquatic habitats.
  • Precautionary statements for sites with characteristics that may be conducive to runoff and when heavy rain is forecasted, in order to reduce the potential for runoff of permethrin to adjacent aquatic habitats.
  • A mandatory vegetative filter strip between the treatment area and the edge of a water body to reduce run-off of permethrin to aquatic environments.

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 permethrin, the PMRA will consider all comments received from the public in response to PRVD2017-18. 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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