California Prop 65 Warning Requirements and Penalties

California Prop 65 warning requirements apply to any business with 10 or more employees that exposes people in California to one of more than 900 chemicals the state has listed as causing cancer or reproductive harm. If that describes your product, facility, or workplace, you must give a “clear and reasonable” warning before the exposure happens, in a format the state has pre-approved, or risk civil penalties of up to $2,500 per violation per day.¹² The warnings run on an opt-out model: the burden is on you to prove an exposure is low enough to skip the label, not on anyone else to prove it is high enough to require one.

Who Has to Comply

Prop 65 reaches almost any business selling into California, including out-of-state companies that ship products in. The statute’s definition of a “person in the course of doing business” carves out three groups that fall outside both the warning and discharge rules:

Businesses with fewer than 10 employees, counting full-time and part-time together.
Government entities at the city, county, state, and federal levels.
Public water systems as defined in state law.

A business with nine employees that hires a tenth crosses the threshold the day the tenth starts.³

Who in the Supply Chain Owns the Warning

For consumer products, the regulations put primary responsibility on the manufacturer, producer, importer, or distributor. That upstream company can satisfy the duty two ways: label the product directly, or send the retailer written notice along with warning materials (shelf tags, signs) and confirm the retailer received them.⁴

Retailers generally just have to post or display the materials they receive. But a retailer takes on independent warning liability when it sells the product under its own private label, when it adds a listed chemical itself, when it covers up or removes an existing warning, or when it has actual knowledge of an exposure and no upstream business is subject to California jurisdiction.⁴ That last trigger catches a lot of online retailers importing goods from overseas suppliers with no California presence.

What the Warning Has to Say

OEHHA regulations provide “safe harbor” warning language. If you follow the safe harbor format, your warning is legally presumed clear and reasonable. The standard safe harbor warning uses a black exclamation point in a yellow triangle, the signal word “WARNING,” and a statement identifying whether the exposure involves a chemical known to cause cancer, reproductive harm, or both.⁵

Short-form warnings are available where label space is tight. They use the same yellow triangle and signal word with condensed text set in at least 6-point type. A rule change is coming: short-form warnings on products manufactured on or after January 1, 2028 must name at least one listed chemical for each type of harm (cancer, reproductive toxicity, or both). Products manufactured before that date can keep using the current short-form text, which does not require naming a specific chemical.⁵

Translations

If you already provide consumer information or facility signage in a language other than English, the Prop 65 warning generally has to appear in that language too. OEHHA publishes sample translations, but the English regulatory text controls if any wording question arises.⁶

Where the Warning Has to Appear

Safe harbor delivery methods vary by setting. For consumer products in a store, you can put the warning on the product label, post a sign or shelf tag at the point of display, or use an electronic device that delivers the warning before purchase. Workplaces with potential chemical exposures typically post signs in areas where exposure is likely, positioned so workers see them before entering. Residential property owners (apartment buildings, for example) may need to notify tenants in writing or by posted notice about exposures from building materials or maintenance chemicals.⁵

Online and Catalog Sales

Internet sellers have to get the warning in front of the buyer before the purchase closes. Regulations give three safe harbor options: display the warning directly on the product page, provide a clearly marked hyperlink using the word “WARNING” that links to the full warning text, or otherwise prominently display the warning before checkout.⁵ A warning buried in general site content doesn’t satisfy the rule. Some retailers trigger a pop-up when the buyer enters a California zip code.

When You Don’t Need a Warning

Not every trace of a listed chemical requires a label. The statute exempts exposures that fall below scientifically established thresholds, with the business carrying the full burden of proving the exemption applies.

For cancer-causing chemicals, the threshold is the No Significant Risk Level (NSRL), defined as the exposure level that would cause no more than one additional cancer case per 100,000 people exposed daily over a lifetime. For reproductive toxins, the Maximum Allowable Dose Level (MADL) sits at 1,000 times below the level at which no observable harmful effect has been found.⁷

OEHHA publishes specific NSRL and MADL values for many listed chemicals. Acrylamide, for instance, has an NSRL of 0.2 micrograms per day; lead has a MADL of 0.5 micrograms per day for reproductive toxicity.⁸⁹ When no official safe harbor level exists for a chemical, you can still claim the exemption by developing your own risk assessment using scientifically valid methods, but the testing is expensive and you own the risk if a court disagrees.

Two other exemptions matter. A business cannot be held liable for failing to warn about a chemical during the first 12 months after it is added to the list.⁷ And where federal law preempts state warning authority for a particular product, Prop 65’s warning requirement doesn’t apply.

One boundary worth flagging: the safe harbor thresholds also control the law’s separate prohibition on knowingly discharging listed chemicals into water or onto land where they will likely reach drinking water sources.¹⁰ Posting a warning doesn’t legalize a discharge; the discharge itself is the violation, and it’s enforced on its own track.

Penalties and How Enforcement Actually Happens

Civil penalties run up to $2,500 per day for each violation, and they stack. A product sold without warnings at several locations over several months can produce staggering exposure very quickly.²

The Attorney General, district attorneys, and city attorneys in larger jurisdictions can enforce the law. In practice, most enforcement comes from private plaintiffs. Prop 65 allows any private citizen or organization to sue a business in the public interest, which has made it one of the most actively litigated environmental statutes in the country.

Before suing, a private enforcer must send a 60-day notice of the alleged violation to the business and to the relevant government prosecutors. If no public prosecutor takes the case within that window, the private party can proceed.² If you receive a 60-day notice, that window is your opportunity to evaluate, cure, or negotiate before the suit lands.

In private enforcement actions, 75 percent of any civil penalty goes to the state’s Safe Drinking Water and Toxic Enforcement Fund, and 25 percent goes to the enforcer who filed the notice.² Attorney fees are separate from the penalty and cannot be swapped for a reduction in penalty payments.¹¹ In a representative year, hundreds of consent judgments and out-of-court settlements have produced tens of millions of dollars in total payments, with attorney fees taking the largest single share. The economics explain why most matters settle and why building compliance in from the start costs a fraction of defending even one notice.

Checking Whether a Chemical in Your Product Is Listed

OEHHA maintains the official list and publishes it as a downloadable file on its website.¹² The Governor is required by statute to update the list at least once a year as scientific evidence develops.¹³ The current inventory covers more than 900 substances, including heavy metals like lead and cadmium, industrial solvents, pesticide ingredients, food-processing byproducts like acrylamide, and certain pharmaceutical compounds. Common consumer-product triggers include lead in dietary supplements and imported spices, BPA in some plastic bottles and can linings, acrylamide in fried and baked starchy foods, and mercury in certain fish species.¹⁴ Warnings also appear routinely on furniture, electronics, building materials, automotive parts, and art supplies. Before shipping anything into California, cross-check your ingredient and material disclosures against the current list, and if a listed chemical shows up, decide early whether to test for a safe harbor exemption or warn.

1
California Legislative Information. California Health and Safety Code 25249.6 – Required Warning Before Exposure to Chemicals Known to Cause Cancer or Reproductive Toxicity
2
California Legislative Information. California Health and Safety Code 25249.7 – Enforcement
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California Legislative Information. California Health and Safety Code 25249.11 – Definitions
4
Legal Information Institute. 27 CCR 25600.2 – Responsibility to Provide Consumer Product Warnings
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OEHHA. Frequently Asked Questions for Businesses
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Proposition 65 Warnings. Sample Warnings and Translations for Businesses
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California Legislative Information. California Health and Safety Code 25249.10 – Exemptions
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Office of Environmental Health Hazard Assessment. Proposition 65 No Significant Risk Levels (NSRLs) and Maximum Allowable Dose Levels (MADLs)
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Office of Environmental Health Hazard Assessment. Lead
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California Legislative Information. California Health and Safety Code 25249.5 – Prohibition on Contaminating Drinking Water with Chemicals Known to Cause Cancer or Reproductive Toxicity
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California Department of Justice. Regulations
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Office of Environmental Health Hazard Assessment. The Proposition 65 List
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California Legislative Information. California Health and Safety Code HSC 25249.8 – List of Chemicals Known to Cause Cancer or Reproductive Toxicity
14
Proposition 65 Warnings. Foods and Beverages