California Proposes Prop 65 MADL for n-Hexane

California’s Office of Environmental Health Hazard Assessment (OEHHA) proposed two Maximum Allowable Dose Levels (MADLs) for n-hexane under Proposition 65, one for oral exposure to n-hexane, and one for inhalation exposure. The proposed oral MADL for n-hexane is 28,000 micrograms per day, and the proposed inhalation MADL for n-hexane is 20,000 micrograms per day.

Also known as the Safe Drinking Water and Toxic Enforcement Act of 1986, Proposition 65 prohibits knowingly exposing any individual to a listed chemical without first providing a “clear and reasonable warning” to such individual. The law provides an exemption from the need to provide a warning where exposures are below a "safe harbor" level—a no significant risk level (NSRL) for a carcinogen or an MADL for a reproductive toxicant.

OEHHA added n-hexane to the Proposition 65 list of reproductive toxicants on December 15, 2017. The warning requirements go into effect one year after a chemical is officially listed, which, in the case of n-hexane, is December 15, 2018. Written comments concerning the proposed MADLs are due by November 19, 2018. For more information, see OEHHA’s website.