Proposition 65, officially the Safe Drinking Water and Toxic Enforcement Act of 1986, is a law that requires warnings be provided to California consumers when they might be exposed to chemicals identified by California as causing cancer or reproductive toxicity. The warnings are intended to help California consumers make informed decisions about their exposures to these chemicals from the products they use. The California Office of Environmental Health Hazard Assessment (OEHHA) administers the Proposition 65 program and publishes the listed chemicals, which include more than 850 chemicals. In August 2016, OEHHA adopted new regulations, effective on August 30, 2018, which change the information required in Proposition 65 warnings.
For background on the new Proposition 65 warnings, see https://www.p65warnings.ca.gov/new-proposition-65-warnings.
Proposition 65 and its regulations are posted at https://oehha.ca.gov/proposition-65/law/proposition-65-law-and-regulations.