In California, it is a requirement to label products that contain chemicals that may cause cancer, birth defects, or reproductive harm. Products that are sold outside of California are not required to have the carcinogen warning label, even if they contain the same substances.
Warning Label Requirements
Companies often label such products, irrespective of whether they will be sold in California or transported outside of the state. This is why if you live outside of California, you may encounter two different art products containing the same chemicals, but only the one that has been produced in California will have the warning label.
California’s Proposition 65, also called the Safe Drinking Water and Toxic Enforcement Act, came into law in 1986 and is intended to help people make informed decisions about protecting themselves from chemicals that could cause harm.
As part of the law, the state is required to publish a list of chemicals that are ‘known to the State of California to cause cancer or reproductive toxicity.’ The list is updated at least once a year and contains nearly 1000 chemicals. The complete list can be found here on the California Office of Environmental Health Hazard Assessment (OEHHA) website.

Artists’ materials with the Proposition 65 warning aren’t necessarily more hazardous than those without it. Products sold outside of California are not required to have the warning label even if they contain the same substances.
Why some products have carcinogen labels and others don’t
As part of the law, most manufacturers selling products in California must provide ‘clear and reasonable warnings’, unless the expected level of exposure would pose no significant cancer risk. Businesses decide whether to put warning labels on their products based on their knowledge of the types of chemicals in them.
Products that are sold outside of California are not required to have the warning label, even if they contain substances that might cause cancer. Some companies that sell products all over the world might only label those sent to California, even though all their products contain the same compounds.

As of August 2018, the label is required to name at least one chemical of concern. The label doesn’t have to list all of them, although the manufacturer might choose to do so.
How to get more information about what’s in the product
While manufacturers are required to put warning labels on products for California, they’re not required to provide the OEHHA with information about the products. This means the OEHHA cannot offer information to help consumers figure out what the potential risk is with a specific product.
Before August 2018, manufacturers didn’t have to specify which chemical(s) of concern were in their products. This means any products made before this date might not list any specific chemicals. As of August 2018, the label is required to name at least one chemical of concern. The label doesn’t have to list all of them, although the manufacturer might choose to do so.
For any product made after August 2018, the Prop 65 labels typically say something like this:
WARNING: This product can expose you to [name of chemical], which is known to the State of California to cause cancer.
Businesses are not required to use this exact wording, so it can vary between labels. It must however be a ‘clear and reasonable warning’.

ACMI-certified product seals indicate when products have been evaluated by a qualified toxicologist and are labelled in accordance with federal and state laws in the USA.
If you find a carcinogen warning label on a product and want more information:
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- Find the name of the manufacturer by checking the package and any information that comes with the product. The contact information is often on or in the package as well, but if it isn’t, you can look it up online by searching the manufacturer’s name.
- Contact the manufacturer to find out what potentially hazardous substance(s) the product contains.
- Ask the manufacturer how a person might be exposed to the chemical(s) of concern from this product. Some common exposure routes include inhalation, contact with food, transfer to food or drink from unwashed hands etc. How a chemical is ingested can have a bearing on the level of risk, which depends on each individual chemical.
- Find out what the manufacturer knows about the hazards of the chemical(s) in the product. Do the risks include cancer, reproductive harm, or both?
- Ask the manufacturer if there are ways to reduce any risk of exposure to the hazardous substance while using the product (this information may be found on the product label, or on an accompanying material safety data sheet, or MSDS).
Once you know which chemical(s) the product contains, you can usually find more information about it from other sources. For example, the OEHHA has fact sheets on many common chemicals on its website at www.p65warnings.ca.gov/fact-sheets. You can also find information on some specific products on the OEHHA website.
For more information and frequently asked questions about carcinogen labels and Proposition 65, go to: www.p65warnings.ca.gov.