What Does a Prop 65 Warning Mean?

The California Office of Environmental Health Hazard Assessment (OEHHA) says Proposition 65 requires businesses to provide a clear and reasonable warning before they knowingly and intentionally cause an exposure to a chemical listed as known to the state to cause cancer or reproductive toxicity. OEHHA says a business that provides a Proposition 65 warning is telling you that using a product or entering a location can expose you to a significant amount of a chemical that causes cancer or reproductive harm, and that a business does not need to provide a warning when exposure from an individual product or location is too low to significantly contribute to an overall risk of cancer or harmful reproductive effects.

OEHHA also says it is aware that some businesses provide unnecessary warnings as a litigation-avoidance strategy, a practice it does not endorse, and that warnings should not be given for non-existent or insignificant exposures because they do not further the purposes of the law. It says businesses are not legally required to follow its safe harbor warning regulations and can develop their own clear and reasonable warnings, but many choose to use them to benefit from safe harbor protections. An OEHHA example of a full-length safe harbor warning for a consumer product says the product can expose you to chemicals including formaldehyde, which is known to the State of California to cause cancer, and toluene, which is known to the State of California to cause birth defects or other reproductive harm, and directs readers to www.P65Warnings.ca.gov.

The warning rules have changed over time. OEHHA says its revised clear and reasonable warning regulations were adopted on August 30, 2016, and became operative on August 30, 2018. Its later amendments to the short-form warning, effective January 1, 2025, make the short-form warning more informative by adding at least one chemical name, give businesses that rely on the existing short-form warnings three years to transition, and provide an unlimited sell-through period for products manufactured and labeled with the existing short-form warnings before or during that transition.

OEHHA says Proposition 65 requires the list of chemicals known to the state to cause cancer or reproductive toxicity to be revised and republished at least once a year. Under the Proposition 65 regulations, a chemical is included on the cancer list if it is identified by reference in the California Labor Code as causing cancer, and a chemical is included if the International Agency for Research on Cancer classifies it as carcinogenic to humans (Group 1), or as probably or possibly carcinogenic to humans (Group 2A or 2B) with sufficient evidence of carcinogenicity in experimental animals. OEHHA says enforcement is carried out through civil lawsuits brought by the Attorney General, any district attorney or certain city attorneys, and that private parties acting in the public interest may also sue, but only after providing notice of the alleged violation to those officials and to the business accused of the violation.