Proposition 65, officially known as the Safe Drinking Water and Toxic Enforcement Act of 1986, was enacted as a ballot initiative in November 1986. The proposition protects the state’s drinking water sources from being contaminated with chemicals known to cause cancer, birth defects or other reproductive harm, and requires businesses to inform Californians about exposures to such chemicals.
Proposition 65 requires the state to maintain and update a list of chemicals known to the state to cause cancer or reproductive toxicity.
Further information about Proposition 65 can be found here