We provide the Proposition 65 disclaimer to be compliant with the Safe Drinking Water Act of 1986 (California Proposition 65).
The Proposition requires that companies with 10 or more employees selling products to consumers in the State of California provide a “clear and reasonable” warning about the potential exposure to listed chemicals, unless the company can prove that the exposure poses no significant risk of harm.  A Proposition 65 warning means the subject company has either tested the product and determined a warning label is required or elected to provide a warning, out of an abundance of caution, merely because the product contains a listed chemical regardless of whether exposure to the product poses a "risk of significant harm."  A warning has been provided out of an abundance of caution.
The California Office of Environmental Health Hazard Assessment (OEHHA) states on its website: "The fact that a product bears a Proposition 65 warning does not mean by itself that the product is unsafe."