California has enacted what is known as the Safe Drinking Water and Toxic Enforcement Act, also referred to as Proposition 65 (Prop 65). Prop 65 requires the State of California to publish and maintain a list of substances identified by the State of California as being potentially harmful. The list has continually expanded since the passage of Prop 65, and it currently contains over 900 substances.
The most recent list and other Prop 65 information are available on California's website: Proposition 65.