The Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) established strict standards for over 1000 compounds, metals, and chemicals (click here for the full list) in the State of California. This legislation requires a warning label on any product sold in California if it may contain any of the listed chemicals exceeding the safe harbor threshold. These thresholds are set, by law, to an extremely low limit, 1000 times lower than the highest levels known to be safe. For example, the Prop 65 threshold for lead requiring a warning label is .5mcg per day. This is 1000 times lower than the highest level of lead known by California NOT to cause reproductive harm. In other words, the Prop 65 warning threshold for lead incorporates a 1000-fold safety factor below the level found to have NO observable effect on humans or animals. The warning threshold is so low that current testing technology cannot reliably determine whether a sample exceeds the threshold or not.
The levels Prop 65 has specified for lead are far more stringent than the levels deemed safe by the other 49 US states, the Food and Drug Administration (FDA), the World Health Organization (WHO), Canada and the European Union (EU).