California Proposes No Significant Risk Levels (NSRLs) for 1-Bromopropane and Diethanolamine Under Prop 65

On August 22, 2025, California’s Office of Environmental Health Hazard Assessment (OEHHA) announced a proposed rulemaking to establish No Significant Risk Levels (NSRLs) for two chemicals under the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65). The proposed NSRLs are:

• 1-Bromopropane: 54 micrograms per day (µg/day)

• Diethanolamine (dermal exposure only): 6.4 µg/day

Both 1-bromopropane (CAS No. 106-94-5) and diethanolamine (CAS No. 111-42-2) are listed under Proposition 65 as carcinogens. 1-Bromopropane is primarily used as a solvent cleaner in degreasing, dry cleaning, asphalt production, and solvent and adhesive sprays. It also serves as an intermediate in pharmaceuticals, insecticides, quaternary ammonium compounds, flavors, and fragrances. Diethanolamine is widely used as a corrosion inhibitor in metalworking fluids, an emulsifier and dispersant in agricultural chemicals, in industrial gas purification, and in producing lubricants, diethanolamides, and diethanolamine salts of fatty acids. These derivatives are commonly found in consumer products such as cosmetics, shampoos, conditioners, and detergents.

These proposed NSRLs act as "safe harbor" levels, providing guidance to businesses on the exposure levels that do not require a Proposition 65 warning. The levels are based on extensive scientific review, including carcinogenicity studies in rodents conducted by the National Toxicology Program.

The public comment period remains open until October 6, 2025, with comments accepted through OEHHA's online portal or via mail.