Proposed special review decision PSRD2026-02, Halohydantoins and associated end-use products

Health Canada
Healthy Environments and Consumer Safety Branch
Pesticides Regulatory Directorate
26 August 2026
ISSN: 2561-6366 (PDF version)
Catalogue number: H113-30/2026-2E-PDF (PDF version)

Summary

Table of contents

• Proposed special review decision for halohydantoins and associated end‑use products
• Proposed special review decision for Halohydantoins
• Risk mitigation measures
• Human health
• Next steps
• Other information

Proposed special review decision for halohydantoins and associated end‑use products

Under the authority of the Pest Control Products Act, pesticides are regulated by Health Canada 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.

Health Canada evaluates the aspect(s) 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).

Pursuant to subsection 17(1) of the Pest Control Products Act, Health Canada initiated a special review of some registered pest control products (see Appendix I of the full version of PSRD2026-02, Halohydantoins and associated end-use products) containing, halohydantoins^{Footnote 1} based on the USEPA 2021 Interim Registration Review Decisions for Inorganic Halides and Halohydantoins. The identified aspects of concern are:

• Potential occupational inhalation risk for workers handling (bromine- and chlorine-based) halohydantoin products formulated as granules.
• Potential residential postapplication cancer risk from incidental oral exposure to bromate in outdoor swimming pools treated with bromine-based halohydantoins and in swimming pools, spas and hot tubs in combination with electrolysis, ozonation or ultraviolet devices.

Pursuant to subsection 18(4) of the Pest Control Products Act, Health Canada has evaluated the aspects of concern that prompted the special review of pest control products containing halohydantoins, which are relevant to human health.

Halohydantoins are antimicrobial active ingredients registered for domestic use in outdoor and indoor swimming pools, spas and hot tubs and for commercial use in industrial process fluids (paper/paper mills, cooling water systems, and industrial processing waters). Currently registered products containing halohydantoins that relate to the aspects of concern have been considered in this special review. The commercial-class products registered in Canada are formulated as tablets, granules, and pastes and the domestic-class products registered in Canada are formulated as tablets and granules. Commercial class products formulated as tablets and pastes fall outside the scope of the aspect of concern that prompted the special review, therefore are not considered in the assessment.

This document (PSRD2026-02) presents the proposed special review decision for halohydantoins, including the proposed amendments (risk mitigation measures) to protect human health, as well as the science evaluation on which the proposed decision is based. This document is subject to a 45-day public consultation period,^{Footnote 2} during which the public (including the pesticide manufacturers and stakeholders) may submit written comments and additional information to Pesticides Publications Section. The final special review decision will be published after taking into consideration the comments and information received during the consultation period that are directly related to the assessment of the aspects of concern for this proposed special review decision.

Proposed special review decision for halohydantoins

Health Canada, under the authority of the Pest Control Products Act has conducted an evaluation of available relevant scientific information related to the aspects of concern for human health in accordance with subsection 18(4) of the Pest Control Products Act. Based on the evaluation of the aspects of concern, Health Canada is proposing for public consultation, pursuant to section 28 of the Pest Control Products Act, the continued registration of certain uses and formulations of halohydantoins products registered for sale and use in Canada under section 21 of the Pest Control Products Act.

The assessment of the aspects of concern from this special review indicates that the risks to human health from the following uses of halohydantoin products are considered to be acceptable provided that proposed mitigation measures are implemented:

• Use of halohydantoin products (formulated as tablets or in pre-filled cartridge) in hot tubs and spas (indoor and outdoor) and indoor pools

The following uses and formulations are proposed for cancellation since risks to human health were not shown to be acceptable:

• Use of halohydantoin products in outdoor pools
• Use of halohydantoins in swimming pools, spas and hot tubs in combination with electrolysis, ozonation or ultraviolet devices
• Open pour granular product formulations

The following products are not impacted by this special review and remain registered without any required mitigation:

• Commercial-class halohydantoin products formulated as pastes or tablets

The proposed additional mitigation measures are summarized below, and details are outlined in Appendix II of PSRD2026-02.

Risk mitigation measures

Registered pesticide product labels include specific directions for use. Directions include risk mitigation measures to protect human health and the environment and to ensure the product has acceptable value which must be followed by law. The proposed label amendments, including revised/updated label statements and/or mitigation measures as a result of the special review of halohydantoins, are summarized below.

Human health

Risk mitigation:

The following risk mitigation measures are proposed to address the aspect of concern relating to potential occupational and residential inhalation risk from handling bromine and chlorine-based halohydantoin products formulated as granules:

• Cancellation of seven commercial-class granular products for use in industrial process fluids (Reg No. 23561, 25261, 25406, 31847, 33163, 27261, 28557)
• Cancellation of one domestic-class granular open pour product (Reg No. 31696) for use in swimming pools, hot tubs and spas.

The following risk mitigation measures are proposed to address the aspects of concern relating to potential residential postapplication cancer risk from incidental oral exposure to bromate in outdoor swimming pools treated with bromine-based halohydantoins and in swimming pools, spas and hot tubs treated with bromine-base halohydantoins in combination with electrolysis, ozonation or UV devices:

• “DO NOT use in outdoor pools.”
• “Outdoor hot tubs and spas must be covered when not in use.”
• “Do not use this product with an electrolysis device (for example, a chlorine generator).”
• “Do not use this product with ozonation.”
• “Do not use this product with ultraviolet (UV) disinfection.”

Next steps

Health Canada will accept written comments on this proposal up to 45 days from the date of publication of this document (“consultation period”). Comments on the proposed decision can be submitted during the consultation period to Health Canada through Pesticides Publications Section, or the Public Engagement Portal (Public Engagement Forms - Consultation Comment). For more information or if you have questions, contact Health Canada’s Pesticides Information Service.

Before making a special review decision on halohydantoins under section 21 of the Pest Control Products Act, the comments received during the consultation period will be taken into consideration in preparation of the final special review decision document. A science-based approach will be applied in making a final decision on halohydantoins. In accordance with subsection 28(5) of the Pest Control Products Act, Health Canada will then publish a final special review decision document, which will include the decision, the reasons for it, a summary of the comments received during the consultation period that are directly related to the assessment of the aspects of concern for this proposed special review decision, and Health Canada’s response to these comments.

Refer to Appendix I of PSRD2026-02 for details on specific products impacted by this proposed decision.

The following additional data may be submitted during the consultation for consideration during the final decision phase:

Human health

No additional scientific data are being requested. However, during the consultation period, the registrants and other stakeholders may consider submitting the following information, if available, that could help address uncertainties in the available information for halohydantoins and support revised assessments.

The evaluation of any additional data would be based on the scientific merit and relevance to the risk assessment. While additional data may reduce uncertainty in the risk assessment, continued registration of any uses would be based on the acceptability of risk assessed using a science-based approach.

• Repeat-dose inhalation toxicity study
• Data regarding feasibility of closed loading transfer system for granular formulations
• Data regarding inhalation exposure for closed loading transfer systems for granular formulations
• Pool and spa-specific data
  • Bromate concentration
  • Exposure time
  • Ingestion rates
  • Exposure frequency
  • Swimmer exposure study (biomonitoring)

Other information

The relevant confidential test data on which the proposed decision is based (see References Section of PSRD2026-02) are available for public inspection, upon application, in Pesticides Regulatory Directorate’s Reading Room. For more information, please contact the Pesticides Information Service.