Special Review Decision SRD2024-01, Potassium dimethyldithiocarbamate and its associated end-use products

Pest Management Regulatory Agency
26 February 2024
ISSN: 2561-6269 (PDF version)
Catalogue number: H113-17/2024-1E-PDF (PDF version)

Summary

Table of contents

• Special review decision for potassium dimethyldithiocarbamate and associated end-use products
• Special review decision for potassium dimethyldithiocarbamate
• Risk mitigation measures
• Implementation of the special review decision
• Next steps
• Other information
• Evaluation approach
• Appendix I Registered products containing potassium dimethyldithiocarbamate in Canada

Special review decision for potassium dimethyldithiocarbamate and associated end-use products

Under the authority of the Pest Control Products Act, pesticides are regulated by Health Canada's Pest Management Regulatory Agency (PMRA) on behalf of the Minister of Health. The Pest Control Products Act prescribes both the pre-market and post-market assessment (re-evaluations and special reviews) of pesticides to determine the acceptability or continued acceptability of human health and environmental risks, and acceptable value of a pesticide in Canada. Unlike a re-evaluation, a special review is triggered only under certain circumstances, as described in section 17 of the Pest Control Products Act, and the intent of a special review is to address specifically the identified aspect(s) of concern. The special review approach is described in the PMRA Guidance Document: Approach to Special Reviews of Pesticides. More details on the legislative framework are provided under the Legislative Framework Section of this document.

Health Canada evaluates the aspects of concern that prompted the special review in accordance with subsection 18(4) of the Pest Control Products Act. The internationally accepted science-based approach is used for the assessment of the aspect(s) of concern, similar to all other scientific assessments (for example, new product registrations, re-evaluations). This step includes both risk assessment and risk management to address the concerns identified. Health Canada's approach to risk and value assessments as well as risk management is outlined in the PMRA Guidance Document: A Framework for Risk Assessment and Risk Management of Pest Control Products.^{Footnote 1}

Potassium dimethyldithiocarbamate is a broad-spectrum biocide registered in Canada for use as a slimicide in industrial fluids and as a material preservative for variety of substances including metal working fluids and brine solutions. Currently registered pest control products containing potassium dimethyldithiocarbamate are listed in Appendix I.

Pursuant to subsection 17(1) of the Pest Control Products Act, Health Canada conducted a special review of all registered pest control products containing potassium dimethyldithiocarbamate based on the toxicology data submitted under section 12 of the Pest Control Products Act following the re-evaluation of sodium and potassium dimethyldithiocarbamate salts (PRVD2011-05 and RVD2012-01). Note that registrants of the active ingredient sodium dimethyldithiocarbamate voluntary discontinued registration of all products containing sodium dimethyldithiocarbamate in 2022. The identified aspects of concern for this special review are:

• Potential cancer and non-cancer risks from occupational handler and postapplication exposure.

To assess the aspects of concern, Health Canada considered the information that prompted the special review and other relevant information currently available, including existing assessments from the re-evaluation of potassium dimethyldithiocarbamate (PRVD2011-05 and RVD2012-01).

This document (Special Review Decision SRD2024-01, Special Review Decision: Potassium Dimethyldithiocarbamate and its Associated End-use Products) presents the final regulatory decision ^{Footnote 2} for the special review of potassium dimethyldithiocarbamate. All pest control products containing potassium dimethyldithiocarbamate that are registered in Canada are subject to this special review decision. Prior to finalizing this decision, Health Canada published the Proposed Special Review Decision PSRD2022-02, Special Review of Potassium Dimethyldithiocarbamate and its Associated End-use Products: Proposed Decision for Consultation^{Footnote 3}, which underwent a 45 day public consultation period ending on 22 October 2022. No comments were received during the public consultation period conducted in accordance with section 28 of the Pest Control Products Act. Therefore, this decision is consistent with the proposed regulatory decision as described in PSRD2022-02.

A reference list of information used as the basis for the proposed special review decision is included in PSRD2022-02. No further information was provided since PSRD2022-02. Therefore, the complete reference list of all information used in this final special review decision is included in PSRD2022-02.

Special review decision for potassium dimethyldithiocarbamate

Health Canada has completed the special review for potassium dimethyldithiocarbamate. Under the authority of the Pest Control Products Act, Health Canada has determined that continued registration of all products containing potassium dimethyldithiocarbamate is acceptable. The assessment of the aspects of concern from this special review found that most uses of potassium dimethyldithiocarbamate products meet the current standards for the protection of human health when used according to revised conditions of registration which includes new mitigation measures. Brine curing/brine solutions (leather industry) uses are cancelled due to lack of data to assess exposure. Label amendments, as summarized below and listed in Appendix II of SRD2024-01, are required.

Risk mitigation measures

Registered pesticide product labels include specific directions for use. Directions include risk mitigation measures to protect human health and must be followed by law. The required amendments, including any revised/updated label statements and/or mitigation measures, as a result of the special review of potassium dimethyldithiocarbamate, are summarized below. Refer to Appendix II of SRD2024-01 for details.

Human health

To protect workers from occupational exposure in industrial facilities or in material preservation scenarios, the following risk-reduction measures are required:

• Cancellation of the brine curing/brine solutions uses due to lack of data to assess exposure
• Requirement for a closed loading and transfer system
• For metal working fluid (cutting fluid) uses, restrict application rate to a maximum rate of 80 ppm

Implementation of the special review decision

Regulatory Directive DIR2018-01, Policy on Cancellations and Amendments Following Re-evaluation and Special Review provides general timelines for implementation of post-market decisions.

When conducting human health risk assessments, risks from exposure to a pesticide are estimated by comparing potential exposures with the most relevant endpoint from toxicology studies, with standard protection factors incorporated to further protect human health, including the most sensitive population. These factors provide an inherent level of protection from exposures that could result in adverse effects to human health. Furthermore, Health Canada applies additional protection factors if warranted by the hazard profile of the pesticide or by the quality and completeness of the underlying data. When risks of concern are identified in the human health exposure scenarios, it does not necessarily mean that exposure will result in adverse effects, but mitigation measures to reduce potential risks would be required in order to support continued registration of the product/use.

Potential and relative health risks are thus considered acceptable during the general 24 month implementation period unless there is evidence from incident reports or other sources of real-world post-market surveillance data suggesting that there are adverse health effects occurring as a result of the use of the product(s) according to the currently approved label/use conditions. Other considerations may include how widely the product is used, the populations potentially exposed to the product and/or other factors. Taking into consideration these factors, the general 24 month implementation timeline for label amendments for pest control products containing potassium dimethyldithiocarbamate is considered appropriate.

Refer to Appendix I for details on specific products impacted by this decision.

Next steps

To comply with this decision, the required label amendments (Appendix II of SRD2024-01) must be implemented no later than 24 months after the publication date of this decision document (SRD2024-01). Accordingly, both registrants and retailers will have up to 24 months from the date of this decision document to transition to selling the product with the newly amended labels. Similarly, users will also have the same 24-month period from the date of publication of this decision document to transition to using the newly amended labels, which will be available on the Public Registry.

Other information

Any person may file a notice of objection^{Footnote 4} regarding this decision on potassium dimethyldithiocarbamate within 60 days from the date of publication of SRD2024-01. For more information regarding the basis for objecting (which must be based on scientific grounds), please refer to the Pesticides section of Canada.ca (Request a Reconsideration of Decision) or the PMRA's Pest Management Information Service.

The relevant confidential test data on which the decision is based (as referenced in PSRD2022-02) are available for public inspection, upon application, in the PMRA's Reading Room. For more information, please contact the Pest Management Information Service.

Evaluation approach

Legislative framework

The Minister of Health's primary objective under the Pest Control Products Act (the Act) subsection 4(1) is to prevent unacceptable risks to individuals and the environment from the use of pest control products.

As noted in the preamble of the Act, it is in the national interest that the attainment of the objectives of the federal regulatory system continue to be pursued through a scientifically-based national registration system that addresses risks to human health, the environment and value both before and after registration and applies to the regulation of pest control products throughout Canada; and that pest control products with acceptable risk and value be registered for use only if it is shown that their use would be efficacious and if conditions of registration can be established to prevent unacceptable risks to human health and the environment.

For the purposes of the Act, the health or environmental risks of a pest control product are acceptable if there is reasonable certainty that no harm to human health, future generations or the environment will result from exposure to or use of the product, taking into account its conditions of registration as per subsection 2(2) of the Pest Control Products Act.

Risk for the human health and environment, and value are defined under the Act subsection 2(1) as follows:

Health risk, in respect of a pest control product, means the possibility of harm to human health resulting from exposure to or use of the product, taking into account its conditions or proposed conditions of registration.

Environmental risk, in respect of a pest control product, means the possibility of harm to the environment, including its biological diversity, resulting from exposure to or use of the product, taking into account its conditions or proposed conditions of registration.

Value, in respect of a pest control product, means the product's actual or potential contribution to pest management, taking into account its conditions or proposed conditions of registration, and includes the product's (a) efficacy; (b) effect on host organisms in connection with which it is intended to be used; and (c) health, safety and environmental benefits and social and economic impact.

When evaluating the health and environmental risks of a pesticide and determining whether those risks are acceptable, subsection 19(2) of the Pest Control Products Act requires Health Canada to apply a scientifically-based approach. The science-based approach to assessing pesticides considers both the toxicity and the level of exposure of a pesticide in order to fully characterize risk. Health Canada's approach to risk and value assessment is outlined in A Framework for Risk Assessment and Risk Management of Pest Control Products^{Footnote 5}.

Appendix I Registered products containing potassium dimethyldithiocarbamate in Canada