The Canadian Department of Environment and Climate Change and the Department of Health recently issued a joint notice, publishing the Final Assessment of Benzotriazole and Benzothiazole Substances. The notice proposes to list six benzothiazole substances under Part 2 of Schedule 1 of the Canadian Environmental Protection Act (CEPA), which enumerates toxic substances. Additionally, a draft Risk Management Approach has been released to outline proposed measures for controlling certain chemical substances.
Assessment Findings
According to the notice, 2-mercaptothiazole (MBT) and its precursor substances (including salts, compounds containing disulfide or sulfamoyl bonds, and derivatives bonded to methyl thiocyanate) meet the criteria for "toxic substances" under Section 64 of the Canadian Environmental Protection Act. Specifically, the six benzothiazole substances listed in Table 1 may pose risks to the environment and human health, and are proposed for inclusion in Part 2 of Schedule 1 to enable further regulatory controls. In contrast, the nine benzotriazole substances listed in Table 2 do not meet the criteria under Section 64, and the government will not take action at this time.
Table 1 Substances in the Benzothiazoles Subgroup
|
CAS RN |
DSL name |
Common name and/or acronym |
|
95-31-8 |
2-Benzothiazolesulfenamide, N-(1,1-dimethylethyl) |
TBBS |
|
95-33-0 |
2-Benzothiazolesulfenamide, N-cyclohexyl- |
CBS |
|
120-78-5 |
Benzothiazole, 2,2’-dithiobis- |
MBTS |
|
149-30-4 |
2(3H)-Benzothiazolethione |
MBT |
|
2492-26-4 |
2(3H)-Benzothiazolethione, sodium salt |
SMBT |
|
4979-32-2 |
2-Benzothiazolesulfenamide, N,N-dicyclohexyl- |
DCBS |
Table 2 Substances in the Benzotriazoles Subgroup
|
CAS RN |
DSL name |
Common name and/or acronym |
|
95-14-7 |
1H-Benzotriazole |
Benzotriazole |
|
3147-75-9 |
Phenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)- |
UV-329 |
|
3846-71-7 |
Phenol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)- |
UV-320 |
|
3896-11-5 |
Phenol, 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methyl- |
UV-326 |
|
29385-43-1a |
1H-Benzotriazole, 4(or 5)-methyl- |
Tolyltriazole |
|
36437-37-3 |
Phenol, 2-(2H-benzotriazol-2-yl)-4-(1,1-dimethylethyl)-6-(1-methylpropyl)- |
UV-350 |
|
70321-86-7 |
Phenol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)- |
UV-234 |
|
80595-74-0 |
1H-Benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-5-methyl- |
NA |
|
94270-86-7a |
1H-Benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-ar-methyl- |
NA |
Risk Management Objectives and Measures
The Canadian government plans to implement a series of risk management measures to reduce the levels of MBT and its precursors in water to below their Predicted No-Effect Concentration (PNEC) of 2.1 µg/L. The proposed measures include:
- Tire and Rubber Manufacturing Industry: Develop release guidelines to reduce emissions of MBT and its precursors. Additionally, encourage companies to adopt best management practices, such as the Environmental Management Operational Norms for the Chemical, Plastics, and Rubber Industries, and consider other regulatory and non-regulatory tools to achieve risk management objectives.
- Metalworking Fluids Industry: Continuously monitor the use of MBT and its precursors in this industry to determine whether future risk management actions are needed.
- Certain Mining Sub-sectors: After developing analytical methods, monitor and oversee these sub-sectors to measure concentrations of MBT in industrial wastewater and its levels in receiving waters, in order to determine whether risk management measures are required.
Public Consultation and Next Steps
The government invites industry and other stakeholders to submit comments and information by May 7, 2025. Following the public comment period, the Canadian government will initiate the development of specific risk management tools. The formulation and implementation of the risk management plan will follow the provisions and timelines of the Canadian Environmental Protection Act. It is anticipated that risk management proposals will be introduced within 24 months of the recommendation to add MBT and its precursors to Schedule 1 of the CEPA, with finalization to be completed within 18 months thereafter.
