What a Proposition 65 warning actually means

• That the product is unsafe. The warning is triggered by a disclosure threshold, not by a finding of harm.
• How much of the chemical is present. The warning names a chemical, not a quantity.
• That the product is illegal. Prop 65 is a warning law, not a ban.
• That a competitor without a warning is cleaner. It may have measured below the safe-harbour level, or it may not be sold in California, or the seller may have taken a different legal view.

OEHHA publishes No Significant Risk Levels for carcinogens and Maximum Allowable Dose Levels for reproductive toxicants. These function as safe harbours: an exposure at or below the published level is deemed not to require a warning, which gives a business certainty rather than leaving it to argue the point.

For a carcinogen, the no-significant-risk level is defined as the exposure that would result in not more than one excess case of cancer in 100,000 individuals exposed over a 70-year lifetime. A person exposed at that level for seventy years would have no more than a one-in-100,000 chance of developing cancer as a result. Warnings are not required if exposures are at or below the safe-harbour level, or if the business can show the exposure poses no significant cancer risk or is substantially below the level observed to cause reproductive effects.

Because the list is long, the penalty structure makes over-warning cheaper than under-warning, and establishing that an exposure sits below a safe harbour costs money. For a company selling a low-margin product into California, printing a warning is often the economically rational choice regardless of what the product contains.

The practical consequence for a shopper is that the presence of a warning carries much less information than its absence, and neither is a substitute for knowing what a product is made of. On cookware specifically, a Prop 65 warning is a reason to ask the manufacturer what the listed chemical is and where it occurs in the product — not a reason to assume a hazard, and not a reason to dismiss the question.

1. Read which chemical is named. Warnings since 2018 generally name at least one. That is the actual information.
2. Ask where it occurs. In the cooking surface, in a handle, in the packaging? A reputable manufacturer will answer.
3. Check the route. Prop 65 covers exposure through use, which is different from a chemical merely being present in a component you never contact.
4. Do not treat absence as certification. A product without a warning has not been certified by anyone.
5. Fall back on composition. What a product is made of is more informative than whether its seller chose to print a warning.

Most often on cookware and on mattresses. For cookware, the relevant question is usually a glaze or a component alloy — and FDA's separate lead leach limits for ceramicware are a more directly useful standard, because they are a test with a numeric limit rather than a warning requirement.

For mattresses and furniture, the more informative label is the TB117-2013 tag required under California's SB 1019, which states whether flame retardant chemicals were added. That is a yes-or-no fact about the product rather than a legal threshold about the seller.

We have not attached product picks to this page. It is an explainer about a legal disclosure requirement, and bolting products onto it would be a stretch — the cookware check and the material table are where the buying decisions live.