California Proposition 65, formally the Safe Drinking Water and Toxic Enforcement Act of 1986, is a state law that requires businesses to warn people before exposing them to chemicals the state has identified as causing cancer or reproductive harm, and prohibits those businesses from discharging the same chemicals into sources of drinking water.1Office of Environmental Health Hazard Assessment. Proposition 65 California voters approved it as a ballot initiative in November 1986. The yellow triangle warning labels you see on products and posted inside businesses across the state exist because of this law.
The Two Things the Law Actually Requires
Every other piece of Proposition 65 flows from two obligations. A business may not knowingly release a listed chemical into any source of drinking water.2Justia. California Health and Safety Code 25249.5-25249.13 – Safe Drinking Water and Toxic Enforcement Act of 1986 And a business may not knowingly expose anyone to a listed chemical without first giving a clear and reasonable warning.3Office of Environmental Health Hazard Assessment. Businesses and Proposition 65 The chemical list, the labels, the exposure thresholds, and the lawsuits all exist to put those two rules into practice.
Who Has to Comply
Proposition 65 applies to any business with ten or more employees that operates in California. Businesses with nine or fewer employees are exempt, as are all local, state, and federal government agencies and operators of public water systems.4California Legislative Information. California Health and Safety Code 25249.10 For consumer products, the law places the primary responsibility for providing warning materials on the producer or packager rather than the retailer, unless the retailer itself introduced the listed chemical.5California Legislative Information. California Health and Safety Code 25249.11
Being outside California does not get a business off the hook. Out-of-state companies that sell into California, including internet retailers, must provide warnings for exposures that happen inside the state.6Proposition 65 Warnings Website. Frequently Asked Questions for Businesses A product shipped to a California address will be used in California, so in practice any product sold to a California customer needs compliant labeling. Online sellers also have to show the warning before the purchase is completed, not in post-sale paperwork. Some satisfy this with a pop-up triggered when the buyer enters a California zip code.
The Chemical List
California maintains a list of roughly 900 chemicals identified as causing cancer or reproductive harm. The list was first published in 1987 and must be updated at least once a year.7Office of Environmental Health Hazard Assessment. About Proposition 65 A chemical’s presence on this list is what triggers the warning and discharge rules.
Chemicals get added in a few ways. The state’s qualified scientific experts can add them after their own review. Chemicals are also added when they are identified under the California Labor Code or when an authoritative body formally designates them as carcinogens or reproductive toxicants. Those authoritative bodies include the U.S. Environmental Protection Agency, the U.S. Food and Drug Administration, the National Institute for Occupational Safety and Health, the National Toxicology Program, and the International Agency for Research on Cancer.8Office of Environmental Health Hazard Assessment. How Chemicals Are Added to the Proposition 65 List
Businesses do not have to comply the day a chemical is added. The warning requirement takes effect 12 months after listing.4California Legislative Information. California Health and Safety Code 25249.10 The drinking water discharge prohibition takes effect 20 months after listing.9Office of Environmental Health Hazard Assessment. The Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) – A Summary
What a Compliant Warning Looks Like
The statute calls for a “clear and reasonable warning” but does not dictate one exact format. Instead, the state publishes safe harbor regulations that spell out specific content and delivery methods. A business that follows the safe harbor language gets a presumption of compliance, which matters a great deal in litigation.3Office of Environmental Health Hazard Assessment. Businesses and Proposition 65
Consumer Product Labels
A safe harbor warning on a consumer product must include the triangular warning symbol (a black exclamation point inside a yellow triangle with a bold black outline), a signal word such as “WARNING” or “CA WARNING,” and the name of at least one listed chemical for each type of harm being warned about. A product warning for both cancer and reproductive toxicity needs at least one chemical name for each category.6Proposition 65 Warnings Website. Frequently Asked Questions for Businesses When a label is not printed in color, the symbol can appear in black and white.10Proposition 65 Warnings Website. Warning Symbol
Workplaces, Buildings, and Environmental Releases
Warnings are not just for packaging. Businesses have to warn people about exposures in physical locations too, including workplaces, parking garages, apartment buildings, and retail stores. That usually takes the form of posted signs near entrances. Environmental warnings cover chemical releases into the air or water. The same safe harbor rules apply, with the delivery method shifting from labels to posted signs or distributed notices.
The 2025 Short-Form Warning Change
California amended its safe harbor regulations effective January 1, 2025. Short-form warnings now have to include at least one chemical name, which was not previously required. Businesses using older short-form labels have a three-year transition period, so the deadline to update falls around January 1, 2028.11Office of Environmental Health Hazard Assessment. Proposition 65 Clear and Reasonable Warnings – Safe Harbor Methods and Content If you rely on the short-form format, the transition is better handled now than at the deadline.
When No Warning Is Required
A warning is not required for every trace amount of every listed chemical. The regulations set two exposure thresholds below which no warning is needed.
- The No Significant Risk Level, or NSRL, applies to chemicals that cause cancer. It is the daily exposure level that would result in no more than one additional cancer case per 100,000 people exposed over a lifetime.
- The Maximum Allowable Dose Level, or MADL, applies to chemicals that cause reproductive harm. It is set at one-thousandth of the level at which no observable reproductive effects occur.
The burden of proof is where this gets uncomfortable for businesses. In an enforcement action, the defendant has to demonstrate that the exposure meets the safe harbor criteria. The plaintiff does not have to prove the exposure is dangerous.4California Legislative Information. California Health and Safety Code 25249.10 Proving an exposure sits below the threshold requires laboratory testing that can be expensive and slow, which is why many businesses label even when the exposure may be minimal.
Foods carry an additional wrinkle because some listed chemicals occur naturally in crops and animal products. The law exempts naturally occurring chemicals in food, but the exemption is hard to use. A business claiming it must prove three things: that the chemical exists naturally in the area where the food is grown or raised, that it did not result from any human activity (including historical pollution or agricultural runoff), and that good manufacturing practices have reduced the chemical to its lowest feasible level. All three elements fall on the business.
Federal law can also preempt Proposition 65 in narrow cases. When a federal statute governs warnings for a particular product in a way that overrides state authority, the Proposition 65 warning obligation does not apply to that exposure.4California Legislative Information. California Health and Safety Code 25249.10 This comes up most often with certain FDA-regulated products, though successful preemption claims are relatively uncommon.
How the Law Is Enforced
Proposition 65 is enforced through civil lawsuits. The California Attorney General has primary enforcement authority. District attorneys can bring cases, and so can city attorneys in cities with populations over 750,000.12Proposition 65 Warnings Website. Who Enforces Proposition 65 The bigger engine of enforcement, though, is private citizens. Any person acting in the public interest can sue a business for a violation.
A private enforcer has to clear two procedural hurdles before filing suit. First, a 60-day notice goes to the alleged violator, the Attorney General, and the relevant local prosecutor. Second, when the alleged violation involves the warning requirement, that notice must include a certificate of merit. The certificate confirms the person filing it consulted with an expert who reviewed the facts and exposure data and concluded there is a reasonable and meritorious case.13California Legislative Information. California Health and Safety Code 25249.7
Violations carry civil penalties of up to $2,500 per day for each violation. Because a single unlabeled product sold across many days can count as multiple violations, penalty exposure adds up quickly. Private enforcers are entitled to 25 percent of the civil penalties collected, and settlements frequently include substantial attorney fee payments.13California Legislative Information. California Health and Safety Code 25249.7 Most Proposition 65 cases settle. Settlements must be reported to the Attorney General.14State of California – Department of Justice – Office of the Attorney General. Proposition 65 Enforcement Reporting
What a Prop 65 Warning Means If You See One
A Proposition 65 warning does not mean a product is unsafe or banned. It means the business has concluded that use of the product could expose you to a listed chemical above the safe harbor level, or, more commonly, that the business has chosen to warn rather than test to confirm the exposure is below that level.15Proposition 65 Warnings Website. Proposition 65 Warnings – Your Right to Know The label tells you a listed chemical may be present. It does not tell you the dose, the probability of harm, or how the exposure compares to what you encounter in everyday life.
If a warning concerns you, the state recommends contacting the manufacturer or importer to ask which chemical prompted the warning and how to reduce exposure. For warnings posted at physical locations like storefronts or apartment buildings, the property manager or landlord should be able to identify the chemicals involved.15Proposition 65 Warnings Website. Proposition 65 Warnings – Your Right to Know Chemical-specific fact sheets are available at p65warnings.ca.gov.