Re-evaluation Decision RVD2014-01, Propoxur

Pest Management Regulatory Agency
30 April 2014
ISSN: 1925-1025 (PDF version)
Catalogue number: H113-28/2014-1E-PDF (PDF version)

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

To obtain a full copy of Re-evaluation Decision RVD2014-01, Propoxur please contact our publications office.

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

Summary

Table of Contents

Re-evaluation Decision for Propoxur

After a thorough re-evaluation of the insecticide propoxur, Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the  Pest Control Products Act, is proposing continued registration for the sale and use of some propoxur uses in Canada and the phase-out of uses with risk concerns.

An evaluation of available scientific information found that under the revised conditions of use, some uses of products containing propoxur have value and do not present unacceptable risks to human health or to the environment. These uses include indoor crack and crevice applications of Commercial class products in commercial areas and outdoor uses of Domestic and Commercial class products, as well as bait trays. As a condition of continued registration of these uses, new risk-reduction measures are to be implemented.

Certain uses of propoxur are to be phased out because either registrants do not support continued registration or a human health risk of concern has been identified. These are: use to control biting flies including mosquitoes, black flies, gnats, sandflies and punkies, use in pet collars, all indoor uses of Domestic class products except bait trays, and indoor uses of Commercial class products in residential areas.

The regulatory approach regarding the re-evaluation of propoxur was first presented in Proposed Re-evaluation Decision PRVD2011-09, Propoxur, a consultation document.Footnote 1 This Re-evaluation Decision DocumentFootnote 2 describes this stage of the PMRA's regulatory process concerning the re-evaluation of propoxur and summarizes the Agency's decision, the reasons for it and, in Appendix I, a summary of comments received during the consultation process and the PMRA's response to these comments. Additional data was received during the consultation process and some assessments were revised as a result. These revised assessments are presented in appendices II and III. This decision is consistent with the proposed re-evaluation decision stated in PRVD2011-09. To comply with this decision, registrants of propoxur products will be informed of the specific requirements affecting their product registration(s) and of the regulatory options available to them.

For more details on the information presented in this Re-evaluation Decision, please refer to the related Science Evaluation section of the previously published consultation document on propoxur (PRVD2011-09).

What Does Health Canada Consider When Making a Re-evaluation 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 pesticide under its conditions or proposed conditions of registration.Footnote 3 The Pest Control Products Act also requires that products have valueFootnote 4 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 risk assessment methods as well as policies that are rigorous and modern. These methods consider the unique characteristics of sensitive subpopulations in both humans (for example, children) and 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 present when predicting the impact of pesticides. For more information on how the PMRA regulates pesticides, the assessment process and risk-reduction programs, please visit the Pesticides and Pest Management section of the Health Canada's website at www.healthcanada.gc.ca/pmra.

What is Propoxur?

Propoxur is a non-systemic carbamate insecticide that is currently registered for use to control a broad range of insect and arthropod pests on a wide variety of sites including: structures (indoors and outdoors), transportation vehicles (for example, boats, ships, trucks, trains), on companion animals, in human habitat and recreational areas (for biting fly and mosquito control) and in residential outdoor areas.

The currently registered labels indicate that propoxur is applied by both ground and aerial means, using mist blowers, foggers and ultra-low volume application equipment to control mosquitoes and other biting flies. Cats and dogs are treated using slow release pet collars. Propoxur is also applied to other sites using pressurized spray cans, hand held and backpack sprayers, and paste applicators by professional applicators and casual users such as home owners.

Health Considerations

Can Approved Uses of Propoxur Affect Human Health?

With the exception of bait trays, additional risk-reduction measures are required for propoxur. Propoxur is unlikely to affect your health when used according to the revised conditions and label directions.

Potential exposure to propoxur may occur through the diet, when handling and applying the product, or when entering or contacting treated sites. 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. In laboratory animals, a single high dose of propoxur caused high oral toxicity, low dermal toxicity, and slight inhalation toxicity. Propoxur is a mild eye irritant, and is not a skin irritant or sensitizer. Acute overexposure to propoxur can inhibit cholinesterase, an enzyme necessary for normal functioning of the nervous system. Clinical signs typical of cholinesterase inhibition were observed by all routes of exposure in acute toxicity studies and included tremors, shortness of breath, salivation, and apathy. The onset of neurotoxicity was rapid but the effects were transient.

Health effects in animals given daily oral doses of propoxur over longer periods of time included cholinesterase inhibition and liver toxicity. No treatment-related effects, including effects on cholinesterase activity, were observed in rabbits exposed to repeated dermal applications of propoxur at the limit dose. Cholinesterase inhibition was the most sensitive endpoint in repeated dose inhalation studies in rats. The severity of neurotoxicity increased with repeated inhalation, but not repeated oral dosing.

There was evidence of urinary bladder and liver carcinogenicity in rats after long-term oral or inhalation exposure. The genotoxicity data for propoxur yielded both positive and negative results. Supplementary evidence in public literature suggests that propoxur can suppress the immune system.

There was no evidence of increased susceptibility of the young in reproduction or developmental toxicity studies. In reproductive studies, maternal cholinesterase activity was the most sensitive endpoint, although cholinesterase inhibition was not measured in offspring. When pregnant animals were orally exposed to propoxur, effects on the developing fetus were only observed at doses that caused death in the mother. Young juvenile rats demonstrated sensitivity to cholinesterase inhibition when compared to adult animals in single dose oral studies.

Implementation of the risk reduction measures will minimize human exposure and ensure any exposure is well below the lowest dose at which the above mentioned effects occurred in animal tests.

Residues in Food and Drinking Water

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

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 drinking water is acceptable if it is less than 100% of the acute reference dose or chronic reference dose (acceptable daily intake). 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.

Exposure for all Canadians through drinking water is minimal since propoxur is primarily registered for indoor, non-dietary use. The only registrant-supported outdoor uses are structural applications to the perimeter of buildings. This indicates that the exposure of environmental compartments to propoxur, such as surface, ground and drinking water will be minimal.

Although propoxur is not applied directly to crops, human dietary exposure to propoxur was estimated from residues in food commodities, resulting from exposure in treated areas (for example, food handling establishments). This exposure to propoxur represents 72% of the acute reference dose and 33% of the chronic reference dose for the most highly exposed subpopulation of children aged 1-2 years old, and is not of concern (refer to Appendix IV of Re-evaluation Decision RVD2014-01, Propoxur). The lifetime cancer risk is 2 × 10-7 for the general population and is not of concern (refer to Appendix IV of RVD2014-01). A lifetime cancer risk that is at or below 1 × 10-6 (one in a million) usually does not indicate a risk concern for the general population when exposure occurs through pesticide residues in/on food and drinking water, and to otherwise unintentionally exposed persons.

Overall, the PMRA has concluded that risks to health from dietary (food and drinking water) exposure to propoxur are not of concern.

Exposure in Residential and Other Non-Occupational Environments

Propoxur is currently used in and around homes, either through application of domestic-class products by residential applicators or by application of commercial-class products by professional pest control operators. Indoor applications can be crack and crevice treatment, perimeter treatment, or spot surface treatment. Propoxur is also used in residential bait trays and in pet collars.

Residential handler non-cancer and cancer risks are not of concern.

For residential applicators applying domestic-class products, including pet collars and bait trays, the calculated dermal and inhalation margins of exposure (MOEs) are greater than the target MOE for all residential applicator exposure scenarios and are not of concern. The calculated dermal and inhalation cancer risks are below 1 × 10-6 and are also not of concern.

For postapplication exposure following indoor application of propoxur, non-cancer risks of concern were identified for children. Cancer risks were identified for most uses. Therefore, risk mitigation is required for indoor application.

For indoor postapplication exposure, the calculated dermal and inhalation MOEs for adults and youths are greater than the target MOE and are not of concern. The calculated inhalation and incidental oral treated surface-to-hand-to-mouth MOEs do not meet the target MOE for children and are of concern.

Calculated dermal cancer risks are above 1 × 10-6 and are of concern for residential postapplication exposure scenarios involving perimeter treatment. Inhalation cancer risks are above 1 × 10-6 and are of concern for all surface treated residential postapplication exposure scenarios. Dermal cancer risks are below 1 × 10-6 and are not of concern for residential postapplication scenarios involving crack and crevice treatment. Incidental oral cancer risks are below 1 × 10-6 and are not of concern for all residential postapplication scenarios.

To mitigate risk from indoor applications of propoxur, propoxur must not be applied to indoor residential use sites, including homes, hospitals, schools, public buildings, day-care facilities, motels, hotels, passenger areas of trains, buses or airplanes, or other indoor locations where children may be exposed.

For postapplication exposure from use of pet collars containing propoxur, non-cancer risks of concern were identified for children. Therefore, risk mitigation is required.

For exposure to people interacting with pets wearing pet collars, the calculated dermal MOEs for all age groups meet the target MOE and are not of concern. The calculated lifetime cancer risks for pet collars are below 1 × 10-6 when using registrant submitted residue data and are not of concern. The incidental oral MOE for treated pet-to-hand-to-mouth for children does not meet the target MOE and is of concern.

To mitigate the risk to children from pet collar applications of propoxur, all pet collar products containing propoxur will be phased out.

There are no risk concerns for residential bait trays.

Postapplication exposure from use of bait trays was considered to be negligible because the active ingredient is enclosed in a self-contained unit and is not available for exposure.

Outdoor residential non-cancer and cancer risks are not of concern.

Postapplication exposure from outdoor applications of propoxur were considered to be negligible, provided that outdoor applications are not made to vegetation, plants, grass or any area accessible to children.

Outdoor residential crack and crevice, structural and stinging insect nest treatments must be limited to areas not frequented by, or inaccessible to, children and the potential for postapplication exposure is minimal. To minimize potential exposures for outdoor treatments propoxur must be limited to crack and crevice, structural and stinging insect nest treatments and must not be applied to vegetation, plants, grass and/or any area accessible to children.

Occupational Risks from Handling Propoxur

Occupational non-cancer and cancer risks are not of concern, provided that risk mitigation measures are taken.

For commercial applicators or pest control operators (PCOs) applying propoxur products, the calculated dermal and inhalation MOEs exceed the target MOE for almost all scenarios using baseline personal protective equipment and are not of concern.

The calculated dermal and inhalation cancer risks are below 1 × 10-5 for most scenarios using baseline personal protective equipment and are not of concern.

Mechanically-pressurized handgun application of emulsifiable concentrates and solutions are of concern for non-cancer and cancer risks. The MOEs did not meet the target MOE, and the cancer risks were above 1 × 10-5 for mechanically-pressurized handgun. Therefore, mitigation is required for this application equipment.

All possible mitigation measures to reduce occupational exposures from use of mechanically-pressurized handgun equipment including personal protective equipment were considered; however, continued application by this method was still not considered to be acceptable. Product labels will be revised to prohibit application using mechanically-pressurized handgun equipment.

Occupational non-cancer and cancer risks are not of concern for postapplication workers.

For workers entering treated sites, it was assumed that postapplication worker exposure would be similar to or less than people exposed in residential areas. The calculated residential dermal and inhalation MOEs exceed the target MOE for adults and are therefore, not of concern for workers. The calculated residential dermal and inhalation cancer risks are below 1 × 10-5 and are also not of concern for workers.

Clarification of the use instructions on the label is required in order to be consistent with the assumptions used in the exposure assessment and/or to be consistent with the mitigation measures for residential areas. These include limiting applications in indoor non-residential areas to perimeter and crack and crevice application only. Outdoor applications must be limited to crack and crevice, structural and stinging insect nest treatments and must not be applied to vegetation, plants, grass and/or any area accessible to children.

Environmental Considerations

What Happens When Propoxur Is Introduced into the Environment?

Propoxur does not pose a potential risk to terrestrial and aquatic organisms since, based on the use pattern, the environmental exposure is expected to be negligible. Additional risk-reduction measures are not needed.

Propoxur is moderately persistent to persistent with the main route of dissipation being biotransformation in soil. Propoxur is not expected to volatilize significantly. Propoxur is mobile in soil. Therefore, there is a potential for propoxur to move to groundwater and surface water, if propoxur was registered for significant outdoor use. However, according to the use pattern of propoxur, the environmental exposure is expected to be minimal.

Propoxur would pose a risk to terrestrial and aquatic organisms if there was environmental exposure. However, the use pattern indicates that potential exposure of non-target organisms is expected to be minimal.

Value Considerations

What Is the Value of Propoxur?

Propoxur is registered in Canada for the control of a wide spectrum of pests on a large number of sites.

In Canada, propoxur is registered to control a wide range of insect and arthropod pests such as: ants, beetles, cockroaches, flies, fleas, millipedes, mites, mosquitoes, spiders, sow bugs, ticks, wasps, and other insect pests on the following sites:

  • on and in structures (commercial, industrial, institutional and residential);
  • in transportation vehicles such as ships, trains, trucks, etc.;
  • in outdoor residential sites;
  • on companion animals (cats and dogs); and
  • in human habitats and recreational sites to control black flies and mosquitoes.

Excluding fumigants, there are a few alternative active ingredients to propoxur registered in Canada with a broad spectrum of control of structural pests. Such active ingredients include silicon dioxide (diatomaceous earth and silica aerogel), boric acid and synthetic pyrethroids.

Propoxur is important for the purpose of resistance management of structural insect pests.

Propoxur's broad spectrum of control of insects and arthropods makes it valuable as an alternative active ingredient to the synthetic pyrethroids (resistance mode of action (MoA) group 3 insecticides) which are also registered for the control of a wide range of structural pests and account for the majority of products registered in Canada for this use.

Propoxur is a MoA group 1A insecticide. In recent years, the registrations of several carbamate and organophosphate insecticides (MoA group 1A and 1B insecticides, respectively) that were used within structures have been discontinued (for example, bendiocarb, chlorpyrifos, diazinon) or their use patterns have been amended, limiting their use to specific sites or to specific application methods (for example, dichlorvos, propetamphos). This limits the availability of active ingredients from MoA groups 1A and 1B to rotate with the synthetic pyrethroids (MoA group 3 insecticides) leading to the potential for limited resistance management options.

Propoxur is characterized as providing rapid knockdown and has a long residual action.

Knockdown, which is characterized as an insect's inability to walk or fly, is rapid with propoxur. Residual action allows propoxur to continue to kill insect pests even after the spray has dried. These traits are important for the control of public health pests such as mosquitoes and cockroaches where immediate and prolonged reduction of a pest population is required.

Alternative active ingredients are available for mosquito control and the pet collar uses of propoxur.

Mosquito control includes the use of pesticides to control the larval and adult stages. Alternative active ingredients to propoxur are available in Canada for the control of mosquito larvae and adults.

Alternative active ingredients to propoxur are available in Canada for the control of fleas and ticks on cats and dogs. These include active ingredients formulated into pet collars and shampoos. Veterinary drugs are also available for control of fleas and ticks on dogs and fleas on cats.

Measures to Minimize Risk

As a result of the revised human health risk assessment, for which further data and the most current exposure methodology was used, there continues to be a high level of concern for pet collar and indoor products containing propoxur applied to residential areas. All pet collar, indoor domestic-class products (except bait trays), and application of commercial-class products in indoor residential areas will be phased out for propoxur as additional mitigation measures are not feasible, and based on available scientific information, these uses do not meet Health Canada's current standards for human health protection and pose unacceptable risks to human health.

Registered pesticide product labels include specific instructions for use. Directions include risk-reduction measures to protect human and environmental health. These directions are required by law to be followed.

As a result of the re-evaluation of propoxur, the PMRA is requiring further risk-reduction measures. These measures, in addition to those already identified on existing propoxur product labels, are designed to further protect human health and the environment. The following additional key risk-reduction measures are required.

Additional Key Risk-Reduction Measures

Human Health

  1. To protect commercial mixers, loaders, and applicators: mechanically-pressurized equipment must not be used.
  2. To protect workers entering treated sites: indoor applications to commercial locations will be limited to perimeter application using manually-pressurized handwand, and crack and crevice applications.
  3. To protect residents and residential applicators: all indoor domestic-class products (except bait trays) will be phased out and commercial-class products must not be applied to indoor residential use sites, including homes, schools, public buildings, day care facilities, motels, hotels, passenger areas of trains, buses or airplanes, and other indoor locations where children may be exposed. Specific directions for outdoor domestic-class and commercial-class products are also required.
  4. To protect homeowners/pet owners: all pet collar products will be phased out.

Label amendments to be implemented are found in Appendix V.

What Additional Scientific Information is Being Requested?

No further information is required at this time as a condition of continued registration or to address uncertainties in the risk assessment.

Other Information

Any person may file a notice of objectionFootnote 5 based on scientific grounds regarding this decision on propoxur within 60 days from the date of publication of this Re-evaluation Decision Document. For more information regarding the basis for objecting (which must be based on scientific grounds), please refer to the Pesticides and Pest Management portion of Health Canada's website (Request a Reconsideration of Decision) or contact the PMRA's Pest Management Information Service.

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