Proposed Re-evaluation Decision PRVD2020-09, Piperonyl Butoxide and Associated End-use Products

Pest Management Regulatory Agency
17 September 2020
ISSN: 1925-0967 (PDF version)
Catalogue number: H113-27/2020-9E-PDF (PDF version)

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Table of contents

Proposed re-evaluation decision

Under the authority of the Pest Control Products Act, all registered pesticides must be regularly re-evaluated by Health Canada’s Pest Management Regulatory Agency (PMRA) to ensure that they continue to meet current health and environmental safety standards and continue to have value. The re-evaluation considers data and information from pesticide manufacturers, published scientific reports, and other regulatory agencies. Health Canada applies internationally accepted risk assessment methods as well as current risk management approaches and policies.

Piperonyl butoxide is a synergist that is always co-formulated with an insecticide. It does not have a direct pesticidal mode of action, but acts to increase the overall efficacy of other active ingredients. It is registered for use in restricted, commercial and domestic products on outdoor ornamentals, pastures, livestock, companion animals, structural sites (indoor and outdoor), clothing, stored grains, home and garden, and lakes, ponds, and reservoirs. Products containing piperonyl butoxide are available in various formulations including dusts, pressurized products, pastes, solutions, and emulsifiable concentrates. A list of the registered products in Canada that contain piperonyl butoxide can be accessed through the PMRA's label transcription service.Footnote 1

Most piperonyl butoxide-containing products were registered prior to the development of modern standardized label language and the labels do not contain comprehensive use directions. Considering the very large number of piperonyl butoxide products currently registered and the variability with regards to the description of their uses on the labels, a scenario-based approach was used to identify the piperonyl butoxide use pattern, rather than a label-based approach. High-level use pattern summary tables were prepared that outlined the different use scenarios for piperonyl butoxide and these tables were shared with registrants and user groups for consultation, and for their comments and clarifications. These tables were used as the basis for the risk assessment of piperonyl butoxide.

As a result of the use pattern consultation, it was determined that the dietary assessment would be limited to specific scenarios on commercial class piperonyl butoxide product labels. In addition, uses for which no data were available, such as application to stored grain and seeds, water, and pastures; space sprays when livestock (other than chickens) are present; spot on application to poultry; dust application in food-handling establishments; and all food and garden uses on domestic-class products were not included in the dietary risk assessment. Summary tables of the uses that were used as the basis of the risk assessment can be found in Appendix I of PRV2020-09.

This document (PRVD2020-09, Piperonyl Butoxide and Associated End-use Products) presents the proposed regulatory decision for the re-evaluation of piperonyl butoxide including the proposed risk mitigation measures to protect human health and the environment, as well as the science evaluation on which the proposed decision was based. All products containing piperonyl butoxide registered in Canada are subject to this proposed re-evaluation decision.

This document (PRV2020-09) is subject to a 90-day public consultation period, during which the public, including the pesticide manufacturers and stakeholders, may submit written comments and additional information to the PMRA. The final re-evaluation decision will be published taking into consideration the comments and information received.

Outcome of science evaluation

Piperonyl butoxide is of value to users as it enhances the effectiveness of other co-formulated active ingredients that control a broad spectrum of insect pests on a wide variety of sites, including commercial and domestic agricultural and structural uses. Piperonyl butoxide is a component of the integrated pest management of common household pests, such as bed bugs, cockroaches, fleas, and indoor ants. When used for treatment of lice on mattresses, bedding, furniture, and garments, piperonyl butoxide does not have acceptable value.

With respect to human health, risks have been shown to be acceptable with mitigation measures required for most uses considered in the risk assessment. As previously discussed, some uses for which no data were available were not included in the dietary risk assessment (for example, application to stored grain, water, and pastures; space sprays when livestock are present; all food and garden uses on domestic-class products). For several uses, risk associated with consumers, bystanders or workers have not been shown to be acceptable. These include domestic-class products used as total release foggers, indoor use of domestic-class dust products, indoor space sprays for domestic-class pressurized products; outdoor insect control using pressurized domestic- and commercial-class products; and broadcast application for bed bug control on commercial-class dust and pressurized product labels. Exposure from the remaining uses is unlikely to affect human health when used according to the proposed label directions.

In terrestrial environments, piperonyl butoxide is not expected to pose a risk to populations of birds, mammals, earthworms, non-target arthopods and terrestrial plants. Because piperonyl butoxide is always co-formulated with an insecticide, the labels for all co-formulated insecticides include mitigation measures that will also reduce the risks associated with piperonyl butoxide. In aquatic environments, spray buffer zones required for insecticides that are co-formulated with piperonyl butoxide will help mitigate potential risks associated with piperonyl butoxide. When used according to instructions on end-use product labels, environmental risks associated with piperonyl butoxide are acceptable.

Proposed regulatory decision for piperonyl butoxide

Under the authority of the Pest Control Products Act and based on the evaluation of currently available scientific information, Health Canada is proposing continued registration of piperonyl butoxide in Canada, provided that the proposed risk mitigation measures are in place to protect human health and the environment. Several uses, where the value or risks associated with consumers, bystanders or workers have not been shown to be acceptable, are proposed for cancellation.

In addition, where data were unavailable to support certain uses that could result in dietary exposure, cancellation is also proposed. Furthermore, only the uses explicitly identified in the summary tables outlined in Appendix I of PRV2020-09 were included in the risk assessment. All other uses are proposed for cancellation due to lack of supporting use information.

Proposed risk mitigation measures

As a result of the re-evaluation of piperonyl butoxide, Health Canada is proposing further risk-reduction measures, in addition to those already included on piperonyl butoxide labels. The updated label statements and mitigation measures, required as a result of the re-evaluation of piperonyl butoxide, are summarized below. Refer to Appendix IX of PRV2020-09 (proposed label amendments) for details.

Human health


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


International context

Piperonyl butoxide is currently acceptable for use in other Organisation for Economic Co-operation and Development (OECD) member countries, including Australia, the European Union and the United States. No decision by an OECD member country to prohibit all uses of piperonyl butoxide for health or environmental reasons has been identified.

Next steps

The public, including the registrants and stakeholders, are encouraged to submit additional information that could be used to refine risk assessments during the 90-day public consultation periodFootnote 2 upon publication of this proposed re-evaluation decision.

All comments received during the 90-day public consultation period will be taken into consideration in preparation of the re-evaluation decision document,Footnote 3 which could result in revised risk mitigation measures. The re-evaluation decision document will include the final re-evaluation decision, the reasons for it and a summary of comments received on the proposed re-evaluation decision with Health Canada’s responses.

Additional scientific information

Data are required to confirm that the application rates and use directions on current product labels are consistent with the rates used in the residential, bystander and occupational risk assessments. Many current labels do not have any rate specified, or the rate is presented in a form that cannot be used for risk assessment purposes (for example, spray for five seconds). Registrants are required to provide data that bridges the use directions and/or the rate on the label, to a rate that can be expressed in units of the amount of piperonyl butoxide per surface area (for example, mg a.i./cm2) for surface applications, or amount of piperonyl butoxide per air volume (for example, mg a.i./m3) for space spray or fogging applications. Data are required for the following products:

In addition, for several uses where risks were shown to be acceptable at the highest rate assessed, limited label rate use/directions are available. Consequently, additional label information is required to support the risk assessment proposal, and further confirm what use directions/mitigation will be required in the final re-evaluation decision.

Registrants are encouraged to contact the PMRA for guidance on how to meet this data requirement. Only products supported by data demonstrating that the rates used in the risk assessments are not exceeded will be considered for continued registration. A Notice, pursuant to paragraph 19(1)(a) of the Pest Control Products Act, will be issued to affected registrants in the near future and will include additional guidance on how to satisfy this data requirement.

Although not required during the consultation period, the registrants and other stakeholders may submit information that may address uncertainties in the available information database of piperonyl butoxide to support refinement of the risk assessment and, subsequently, change the proposed mitigation. Providing data, or an acceptable rationale to waive data, is recommended if registrants wish to maintain certain limited uses, such as the restricted use with rotenone for direct application to ponds, lakes, reservoirs, and streams.

For the dietary assessment, registrants may also propose alternative mitigation measures, provided these result in acceptable dietary exposure. For example, registrants may wish to propose a lower maximum application rate instead of reducing the number of applications, or may propose to revoke additional MRLs to allow for higher cumulative outdoor application rates in Canada. In addition, stakeholders are encouraged to comment on the feasibility of the proposed mitigation and their potential impact on associated pest management practices.

Revisions to the proposed mitigation measures for occupational and residential uses may be considered if clarifications to the piperonyl butoxide use pattern or chemical-specific studies are provided during the comment period. Examples of this information include (but are not limited to):


Footnote 1

The PMRA’s pesticide label search database is available online in the Pesticides portion of Pesticide labels can also be accessed on a mobile device using the pesticide label app available in the Pesticides portion of

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Footnote 2

“Consultation statement” as required by subsection 28(2) of the Pest Control Products Act.

Return to footnote 2 referrer

Footnote 3

“Decision statement” as required by subsection 28(5) of the Pest Control Products Act.

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