Carcinogen

A carcinogen under Proposition 65 is a chemical that is ‘known to the state to cause cancer.’ Chemicals are added to the Proposition 65 list as carcinogens through four mechanisms: (1) formal identification by the state’s Carcinogen Identification Committee (CIC) of OEHHA’s Scientific Advisory Panel; (2) required listing of chemicals identified by an authoritative body (such as IARC, US EPA, NTP, FDA) as causing cancer; (3) formal identification under California’s Labor Code (occupational carcinogens); or (4) chemicals identified in regulations as causing cancer via other state or federal processes. The No Significant Risk Level (NSRL) is the relevant safe harbour threshold for carcinogens. Vinyl acetate was added as a carcinogen effective January 3, 2025.

California Health & Safety Code §25249.8 (listing mechanisms); Title 27 CCR §§25302, 25305, 25306 (listing mechanisms); OEHHA Proposition 65 list.

Products or business operations that expose consumers, workers, or the public to a listed carcinogen above its No Significant Risk Level require a Proposition 65 warning. Businesses must identify all listed carcinogens potentially present in their products (via testing or supplier declarations) and assess whether exposure levels exceed the NSRL. The burden of proof in enforcement actions lies with the defendant: the defendant must show that the level of exposure is below the NSRL once the plaintiff establishes that a listed carcinogen was present.