Proposition 65, or 'Prop 65', is a California law passed in 1986 to protect drinking water sources from toxic substances that cause cancer and birth defects and to reduce or eliminate exposures to those chemicals. Prop 65 requires warnings in advance of those exposures. It is administered by California EPA's California Office of Environmental Health Hazard Assessment (OEHHA). Prop 65 regulates substances officially listed by California as causing cancer or birth defects or other reproductive harm in two ways. First, businesses are prohibited from knowingly discharging listed substances into drinking water sources, or onto land where the substances can pass into drinking water sources. Second, businesses are prohibited from knowingly exposing individuals to listed substances without providing a clear and reasonable warning, such as a sign or label. The State of California manages a Prop 65 list of these potentially harmful chemicals.