A Proposition 65 Warning is necessary due to a California law known as the "California Safe Drinking Water and Toxic Enforcement Act of 1986," or "Proposition 65." This law requires that a warning be given when a product contains certain chemicals designated by the State of California, even if only in extremely low, trace amounts, and even if they do not make the product unsafe. The list of chemicals designated by the State of California has grown to include over 900 chemicals, and includes naturally occurring items like wood dust. Proposition 65 warnings appear in California on products ranging from potato chips and balsamic vinegar to luggage.
The California government has stated: "The fact a product bears a Proposition 65 warning does not mean by itself that the product is unsafe. You could think of Proposition 65 more as a 'right to know' law than a pure product safety law." April 2012, CA Office of Environmental Health Hazard Assessment.