Canada Proposes CEPA Schedule 1 Listing for Boric Acid and Benzothiazoles Following Updated Risk Assessments

On March 8, 2025, the Government of Canada published two regulatory proposals in the Canada Gazette to list boric acid, its salts and precursors, as well as certain substances in the benzotriazoles and benzothiazoles group, specifically 2-mercaptobenzothiazole (MBT) and its precursors, under Part 2 of Schedule 1 to the Canadian Environmental Protection Act, 1999 (CEPA). The proposals follow updated risk assessments that identified potential risks to the environment and, in the case of boric acid, to human health,. The public consultations are now open, providing stakeholders with an opportunity to submit comments and additional information by May 7, 2025.

1. Boric Acid, Its Salts and Precursors: Proposed Addition to Schedule 1

Background and Scope:

The updated assessment focuses on boric acid, a common substamce of concern. It includes any boron-containing substance that can release boric acid through environmental or physiological transformation pathways. Boric acid is found naturally and is widely used in industrial and consumer applications.

Between 2017 and 2020, Canada imported 54,810 to 65,795 tonnes of boric acid-related substances annually, with significant domestic use in sectors such as:

• Insulation and engineered wood manufacturing

• Agriculture and fertilizers

• Consumer and self-care products

• Oil and gas extraction

• Waste and water treatment

Environmental Risk:

A weight of evidence approach indicates that boric acid poses a low ecological risk in most sectors. However, the metal ore processing industry presents a localized environmental risk due to aquatic releases of boric acid. A predicted no effect concentration (PNEC) of 1.5 mg B/L has been established based on Canadian Water Quality Guidelines.

Boric acid is persistent in the environment but not considered bioaccumulative or biomagnifying.

Risk to Human Health:

Canadians are exposed to boric acid from natural sources (e.g. fruits, vegetables, drinking water) and products such as cleaning agents, cosmetics, and DIY materials. Urine and blood biomonitoring data were used to assess population-level exposure.

Key findings include:

• Higher boron levels in young children and women,

• Exposure margins in some products (e.g. toys, self-care items, flame retardants) may be insufficient to protect against health risks such as reproductive toxicity (e.g., reduced testicular weight)

Conclusion:

The assessment suggests that boric acid and its related substances:

• Meet CEPA section 64(a): harmful to the environment

• Meet CEPA section 64(c): pose a risk to human health

• Do not meet section 64(b): not a threat to life-supporting environmental systems

• Meet persistence but not bioaccumulation criteria under CEPA regulati

2. Benzotriazoles and Benzothiazoles Group (Including MBT)

Overview:

The government also published its final assessment of the benzotriazoles and benzothiazoles group, which includes:

• 9 benzotriazole substances (used in UV stabilizers, lubricants, cosmetics).

• 6 benzothiazole substances (including MBT and its precursors, used in rubber and automotive products).

Key Findings:

• Benzotriazoles: Do not meet CEPA section 64 criteria; no significant environmental or health risks identified.

• Benzothiazoles (MBT and precursors):

  • Meet section 64(a): pose environmental risks.

  • Do not meet section 64(b): no threat to environmental systems.

  • Do not meet section 64(c): no current threat to human health but remain substances of concern.

MBT is identified as a Group 2A carcinogen (probably carcinogenic to humans) by the IARC. Exposure scenarios - especially in rubber manufacturing and metalworking fluids – indicate a risk to the aquatic environment. While current public exposures are not of concern, elevated levels in the future could pose health risks.

Proposed Actions:

The Ministers recommend that MBT, its salts, and chemical derivatives be added to Part 2 of Schedule 1 of CEPA. A risk management approach document is available for public comment.

How to Participate in the Consultations

For both the boric acid and MBT proposals, interested stakeholders can provide input during the open public comment period. Comments should reference the Canada Gazette, Part I, the date of publication, and include any requests for confidentiality under section 313, of CEPA if applicable.

Regulatory Implications and Follow-up

These proposals do not impose any immediate new obligations, but allow for future risk management measures, such as pollution prevention plans, restrictions, or monitoring. Substances associated with health risks but currently at safe exposure levels may be tracked to monitor commercial use and emerging risks.

The Government will use the data collected through these consultations to:

• Inform future regulatory development,

• Track trends in chemical use.

• Evaluate the effectiveness of current and proposed risk management measures.