Proposition 65 (formally titled "The Safe Drinking Water and Toxic Enforcement Act of 1986") is a California law passed by direct voter initiative in 1986 by a 63%-37% vote. Its goals are to protect drinking water sources from toxic substances that may cause cancer and birth defects and to reduce or eliminate exposures to those chemicals generally, for example in consumer products, by requiring warnings in advance of those exposures.
Proposition 65 is administered by Cal/EPA's California Office of Environmental Health Hazard Assessment (OEHHA). Proposition 65 regulates substances officially listed by California as having a 1 in 100,000 chance of causing cancer over a 70-year period or birth defects or other reproductive harm in two ways. The first statutory requirement of Proposition 65 prohibits businesses from knowingly discharging listed substances into drinking water sources, or onto land where the substances can pass into drinking water sources. The second prohibits businesses from knowingly exposing individuals to listed substances without providing a clear and reasonable warning.
An official list of substances covered by Proposition 65 is maintained and made publicly available. Chemicals are added to or removed from the official list based on California's analysis of current scientific information. All substances listed show their known risk factors, a unique CAS chemical classification number, the date they were listed, and, if so, whether they have been delisted.
Proposition 65 remains politically controversial even after 25 years, in large part because, in effect, it puts the burden of proof on business instead of government to make a key scientific determination about safety levels for specific toxic chemicals that the businesses are knowingly exposing members of the public to. According to the California Environmental Protection Agency, "Proposition 65 has... increased public awareness about the adverse effects of exposures to listed chemicals.... [and] provided an incentive for manufacturers to remove listed chemicals from their products.... Although Proposition 65 has benefited Californians, it has come at a cost for companies doing business in the state." The law has also been criticized for the proliferation of "bounty hunter" lawsuits. Attorneys have collected more than two-thirds of the money paid by businesses to settle Proposition 65 lawsuits since 2000.