Understanding Prop 65

California Proposition 65, formally the Safe Drinking Water and Toxic Enforcement Act of 1986, requires a clear and reasonable warning before a business exposes people in California to a chemical on the state's list of chemicals known to cause cancer or reproductive toxicity. The state must revise and republish that list at least once a year (Health and Safety Code 25249.8(a)). Businesses with fewer than 10 employees are outside the law (HSC 25249.11(b)).

Two exposure levels:

• NSRL (No Significant Risk Level) — for chemicals listed as causing cancer. It is the level calculated to result in one excess case of cancer in an exposed population of 100,000, assuming lifetime exposure at that level (27 CCR 25703(b)).
• MADL (Maximum Allowable Dose Level) — for chemicals listed as causing reproductive toxicity. It is the no-observable-effect level divided by 1,000 (27 CCR 25801(b)).

A business that shows an exposure falls below these levels does not need to warn, and the burden of showing it is on the business (HSC 25249.10(c)).

Safe-harbor warning formats (27 CCR 25603, as amended effective January 1, 2025):

• Both formats start with the yellow warning triangle and the word WARNING: (or CA WARNING: or CALIFORNIA WARNING:) and point to www.P65Warnings.ca.gov.
• Full-length warning — names at least one listed chemical, for example: "This product can expose you to chemicals including [chemical], which is known to the State of California to cause cancer. For more information go to www.P65Warnings.ca.gov."
• Short-form warning — also names at least one chemical, for example: "Can expose you to [chemical], a carcinogen. See www.P65Warnings.ca.gov."
• The older short form that names no chemical ("Cancer - www.P65Warnings.ca.gov.") may still be used on a product manufactured and labeled before January 1, 2028 (27 CCR 25603(c)).

WARNING: The civil penalty for a violation is up to $2,500 per day for each violation (HSC 25249.7(b)(1)). If you receive a notice, see Responding to a Prop 65 60-day notice.