Prop 65 Requirements: Warnings, Responsibility, and Penalties

If your business has ten or more employees and either operates in California or sells products to California consumers, Proposition 65 requirements mean you must give a clear and reasonable warning before exposing anyone to a chemical on the state’s list of substances known to cause cancer or reproductive harm, and you cannot discharge those chemicals into sources of drinking water.¹ Violations carry civil penalties of up to $2,500 per day.²

Does Prop 65 Apply to Your Business

Prop 65 covers any “person in the course of doing business” with ten or more employees. Companies with fewer than ten workers are exempt, as are all federal, state, county, and local government agencies and entities operating public water systems.³

The reach extends past state lines. If you manufacture in another state but sell into California, including through online marketplaces, you have to comply. The law follows the product into California, not the company’s headquarters.

What Triggers a Warning

The Office of Environmental Health Hazard Assessment (OEHHA) publishes the list of chemicals, updates it at least once a year, and makes it available to download along with any established safe harbor exposure levels.⁴⁵ Hundreds of substances appear on it, from industrial solvents to chemicals found in everyday food and consumer goods.

If a product you make or sell contains a listed chemical and can expose a person to it, you need to warn before the exposure happens. The statute uses a “knowingly” standard, but that doesn’t require intent to harm. You’re considered to know about an exposure if you know, or reasonably should know, that your product contains a listed chemical at levels that could trigger the requirement.

Safe Harbor Levels

Not every trace amount triggers a warning. OEHHA has set numeric thresholds for many listed chemicals: No Significant Risk Levels (NSRLs) for carcinogens and Maximum Allowable Dose Levels (MADLs) for reproductive toxicants.⁶ If exposure from your product falls below the applicable threshold, no warning is required.

The catch is that the burden of proof is entirely on the business. If you’re sued, you have to show the exposure is under the safe harbor. For carcinogens, you need to show no significant risk over a lifetime. For reproductive toxicants, you need to show no observable effect at 1,000 times the actual exposure level.⁷ That’s why many businesses add a warning label rather than invest in the testing needed to prove the exemption.

Not every listed chemical has a published NSRL or MADL. When no safe harbor number exists, you either provide the warning or run your own scientifically valid risk assessment to show the exposure is safe.

The 12-Month Grace Period for New Listings

When a chemical is newly added to the list, the warning requirement doesn’t kick in right away. The statute gives you 12 months from the listing date before you have to warn.⁷ Use that window to test, reformulate, or roll out new labels. Once the 12 months are up, full enforcement applies.

What a Compliant Warning Must Contain

California regulations spell out the format. Getting the warning wrong can be as costly as skipping it.

Full Warnings

A standard Prop 65 warning must include a black exclamation point inside a yellow equilateral triangle with a bold black outline, the word “WARNING” (or “CA WARNING” or “CALIFORNIA WARNING”) in bold capital letters, the name of at least one listed chemical in the product, a statement that the chemical is known to the State of California to cause cancer or reproductive harm (or both, depending on the chemical), and the URL www.P65Warnings.ca.gov.⁸ If a product contains chemicals listed for both cancer and reproductive harm, name at least one from each category.

The triangle goes to the left of the warning text and must be at least as tall as the word “WARNING.”⁹ If the label isn’t printed in color, the symbol can appear in black and white.

Short-Form Warnings

For on-product labels where space is tight, a shorter version is allowed. Short-form warnings still require the triangle symbol (except on food products), the word “WARNING” in bold capitals, and the name of at least one listed chemical. Text must be at least 6-point type and no smaller than the largest font used for other consumer information on the product. Food products using the short-form warning omit the triangle and direct consumers to www.P65Warnings.ca.gov/food instead of the standard URL.

Online Sales and Non-English Labels

Products sold online need a warning shown to the buyer before they complete the purchase, in addition to any label on the physical product. The warning can appear on the product display page or through a clearly marked hyperlink. If a product’s label or packaging carries any consumer information in a language besides English, the Prop 65 warning must also appear in that language.¹⁰

Who Is Responsible: Manufacturer or Retailer

Primary responsibility sits with the manufacturer, producer, packager, importer, supplier, or distributor, not the retailer.¹¹ Those upstream companies comply either by placing the warning directly on the product label or by sending written notice with the required warning language to the retailer.

A retailer picks up the responsibility only in limited situations: it sells the product under its own brand or trademark, it introduced the listed chemical into the product, it covered up or altered an existing warning, it received warning materials from the manufacturer but failed to display them, or it has actual knowledge of the exposure and there is no manufacturer with a business presence or agent in California.¹¹

For internet sales, the retailer is responsible for actually posting the warning on its site, and manufacturers share liability when they fail to supply the retailer with the notice and warning language. If you’re a small retailer selling third-party products online to California buyers, make sure your suppliers are sending you the warning content you need.

The Drinking Water Discharge Ban

Prop 65 is more than a labeling law. It also prohibits businesses from knowingly releasing listed chemicals into any source of drinking water, or onto land where those chemicals are likely to reach a drinking water source through runoff or soil migration.¹² This covers both groundwater and surface water. The same “knowingly” standard applies: a violation occurs when a business knows it is releasing a listed chemical into water or onto land that drains into a water supply.

Penalties and Who Can Sue

Enforcement runs through civil lawsuits. The California Attorney General can bring an action, as can district attorneys and city attorneys in cities with populations over 750,000, along with city prosecutors who have the district attorney’s consent.²

The maximum civil penalty is $2,500 per day for each violation.² That per-day, per-violation math is what makes the exposure so large. A single unlabeled product line sold in California for a year can face theoretical penalties well into six figures, before attorney fees.

Private Enforcement and the 60-Day Notice

Any person can bring an enforcement action in the public interest, but they have to send a 60-day notice of the alleged violation to the business, the Attorney General, and the local district attorney or city attorney first. If none of those government offices files its own case within 60 days, the private party can proceed.²

For failure-to-warn claims, the person filing must also submit a certificate of merit. That certificate requires the filer or their attorney to confirm they consulted with a qualified expert who reviewed the facts and data about the chemical exposure, and that based on that review the case is reasonable and meritorious.² Without it, the private party has no authority to proceed.¹³

Private enforcement drives most Prop 65 activity, and the economics favor plaintiffs. A winning plaintiff recovers attorney fees; a business that successfully defends itself almost never recoups its legal costs. Businesses that test products, provide accurate warnings, and keep documentation are in the strongest position to resist weak claims.

Narrow Defenses Worth Knowing About

Federal Preemption

The warning requirement does not apply when federal law already governs warnings for a particular exposure in a way that overrides state authority.⁷ This comes up with products regulated by agencies like the FDA or EPA whose labeling schemes explicitly preempt additional state warnings. The exemption is narrow, and most consumer products still require Prop 65 compliance even if they carry federally mandated labels.

Naturally Occurring Chemicals in Food

If a listed chemical is naturally present in a food and was not introduced by any human activity, consuming the food may not count as an “exposure” under Prop 65. The business bears the burden of proving three things: the chemical occurs naturally in the growing or production area, it did not get there through any human activity (including historical pollution or distant runoff), and the company used good manufacturing practices to reduce the chemical to the lowest feasible level. Courts have read the “human activity” element broadly to include pollution from decades or even centuries ago, which is why warnings appear on products like coffee, fish, and certain vegetables rather than producers trying to litigate whether their chemicals are truly natural.

1
California Legislative Information. California Health and Safety Code HSC 25249.6 – Required Warning Before Exposure to Chemicals Known to Cause Cancer or Reproductive Toxicity
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California Legislative Information. California Health and Safety Code HSC 25249.7
3
California Legislative Information. California Health and Safety Code HSC 25249.11 – Definitions
4
OEHHA. The Proposition 65 List
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California Legislative Information. California Health and Safety Code HSC 25249.8
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OEHHA. Proposition 65 No Significant Risk Levels NSRLs and Maximum Allowable Dose Levels MADLs
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California Legislative Information. California Health and Safety Code HSC 25249.10 – Exemptions from Warning Requirement
8
Legal Information Institute. California Code of Regulations Title 27 25603 – Consumer Product Exposure Warnings
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Proposition 65 Warnings Website. Warning Symbol
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Proposition 65 Warnings Website. Sample Warnings and Translations for Businesses
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Legal Information Institute. California Code of Regulations Title 27 25600.2 – Responsibility to Provide Consumer Product Exposure Warnings
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California Legislative Information. California Health and Safety Code HSC 25249.5 – Prohibition on Contaminating Drinking Water with Chemicals Known to Cause Cancer or Reproductive Toxicity
13
California Department of Justice. Proposition 65 Regulations