Discharge Prohibition

In addition to its warning requirements, Proposition 65 contains a separate prohibition under Health & Safety Code §25249.5 against the knowing discharge or release of a listed chemical into any source of drinking water or into water or onto land where it will pass into drinking water. This discharge prohibition applies to businesses with 10 or more employees. The discharge prohibition is distinct from the warning requirement and applies regardless of whether the quantity of chemical discharged causes a ‘significant risk’ as defined under the warning provisions. The threshold is whether the discharge creates a ‘significant risk’ of exposure to the population served by the drinking water source.

California Health & Safety Code §25249.5 (discharge prohibition); §25249.7 (penalties apply equally).

Manufacturing facilities and industrial operations must assess whether their processes discharge listed chemicals to water or land that could reach drinking water sources. Unlike the warning provisions (which apply only to exposures above NSRL/MADL), the discharge prohibition has a lower threshold and broader application. Businesses operating near groundwater recharge zones or surface water sources used for drinking water must conduct source-water protection assessments for Proposition 65-listed chemicals. Environmental compliance programmes should specifically address Prop 65 discharge obligations alongside NPDES and Clean Water Act requirements.