Understanding Prop 65
California's chemical disclosure law and what it means for your products.
California Proposition 65 — formally the Safe Drinking Water and Toxic Enforcement Act — requires businesses to provide clear and reasonable warnings before knowingly exposing California residents to any of 900+ listed chemicals known to cause cancer, birth defects, or reproductive harm.
Two exposure thresholds:
- NSRL (No Significant Risk Level) — for cancer-causing chemicals. Lifetime exposure below the NSRL is exempt from warning.
- MADL (Maximum Allowable Dose Level) — for reproductive toxicants. Daily exposure below the MADL is exempt.
Warning label formats:
- Short-form warning —
WARNING: Cancer and Reproductive Harm — www.P65Warnings.ca.gov(or single endpoint variant) - Long-form warning — names the specific chemical, exposure route, and includes the safe-harbor URL
TIP: Even if you don't sell directly into California, Prop 65 likely still applies. Big retailers (Amazon, Walmart, Target) require Prop 65 labels on all products regardless of destination.