California Proposition 65 Notice: Warning Rules and Penalties

A California Proposition 65 warning is the notice a business must give before exposing anyone in California to one of roughly 900 chemicals the state has identified as causing cancer, birth defects, or other reproductive harm.¹ The warning has to carry specific content, appear in a specific format, and reach the consumer through the right channel for how the product or exposure is delivered. Get any of those pieces wrong and the business can face civil penalties of up to $2,500 per violation per day, usually in a lawsuit filed by a private enforcer rather than a state agency.

When a Warning Is Required

The statute prohibits any business from knowingly exposing someone to a listed chemical without first giving a clear and reasonable warning.² “Knowingly” doesn’t mean intent to harm. If the chemical is present and the business knows or reasonably should know that an exposure is occurring, the obligation attaches.

The list is maintained by the Office of Environmental Health Hazard Assessment (OEHHA) and is updated at least once a year.³ It ranges from well-known substances like lead and formaldehyde to chemicals tied to specific industrial processes.

Not every trace exposure counts. OEHHA has set “safe harbor” thresholds for many listed chemicals, and exposures below those levels do not trigger the warning requirement.⁴ For carcinogens, the threshold is the No Significant Risk Level: the daily intake calculated to produce no more than one additional cancer case per 100,000 people exposed over a 70-year lifetime. For reproductive toxicants, the threshold is the Maximum Allowable Dose Level, set at one-thousandth of the level at which no reproductive harm has been observed.⁵ The burden of proving an exposure stays below the threshold rests on the business, not on whoever brings the enforcement action.⁶

Who Has to Warn

Primary responsibility sits upstream: the manufacturer, producer, packager, importer, or distributor. These businesses can either put the warning on the product themselves or supply the warning materials and notice to the retailer.

Retailers aren’t fully insulated. A retailer carries independent responsibility when it sells the product under its own brand, introduces the listed chemical through its own processing, covers or removes a warning the manufacturer already applied, or has actual knowledge of the exposure in cases where the manufacturer can’t readily be compelled to warn.⁷ If a supplier fails to provide a warning, the retailer can still end up in the enforcement crosshairs.

Businesses and Exposures That Are Exempt

Several categories sit outside the law entirely:

Businesses with fewer than 10 employees are exempt from the warning requirement and from the ban on discharging listed chemicals into drinking water sources.⁸
All federal, state, and local government agencies are exempt, as are public water system operators.⁸
Where federal law governs warnings for a particular exposure and preempts state requirements, Proposition 65 does not apply to that exposure.⁶
Newly listed chemicals get a 12-month grace period before the warning obligation kicks in.⁶
A chemical that is a natural constituent of a food, or is present only because the food absorbed it from the growing environment, doesn’t trigger a warning, provided its presence doesn’t result from human activity. The business invoking this defense has to prove it.

What the Warning Has to Say

The current content rules took full effect on August 30, 2018, replacing older generic language. A compliant long-form warning has four elements:⁹

A warning symbol: a black exclamation point inside a yellow equilateral triangle with a bold black outline. If the label isn’t printed in color, the symbol can appear in black and white. It goes to the left of the warning text and must be at least as tall as the word “WARNING.”
The word “WARNING” in all capital letters and bold type.
Identification of at least one specific chemical responsible for the exposure. If both a carcinogen and a reproductive toxicant are involved, at least one of each must be named. The template reads: “This product can expose you to chemicals including [chemical name], which is known to the State of California to cause cancer.”
A reference to www.P65Warnings.ca.gov for more information.

OEHHA publishes distinct templates for a carcinogen alone, a reproductive toxicant alone, both from different chemicals, and a single chemical listed as both. The wording differs between templates, so the right one has to be matched to the exposure.⁹

Short-Form Warnings and the 2025 and 2027 Deadlines

A shorter label version is also permitted and can be used regardless of package size, provided the text is at least 6-point type.¹⁰ The short form used to be able to skip chemical names entirely. That changed on January 1, 2025: short-form warnings must now include at least one chemical name. Businesses using older short-form warnings have a three-year transition period to update them, running through the end of 2027.¹¹ Short-form templates follow the same carcinogen, reproductive, or both structure as the long form, with abbreviated phrasing like “Cancer risk from exposure to [chemical name]” or “Can expose you to [chemical name], a carcinogen.”

How the Warning Has to Reach the Consumer

Delivery depends on the exposure channel.

Physical products. A label fixed to the product or its immediate packaging is the cleanest route. A shelf tag or sign at the point of sale also works.

Online sales. The warning has to reach the buyer before the purchase is completed. Three methods are allowed: display the warning directly on the product page, provide a clearly marked hyperlink using the word “WARNING,” “CA WARNING,” or “CALIFORNIA WARNING” that leads to the full warning text, or otherwise display the warning prominently before checkout.⁷ A warning tucked somewhere in the site’s general content that a buyer would have to hunt for doesn’t satisfy the rule.¹²

Catalog sales. The warning has to appear in the catalog itself, clearly tied to the specific product.

Physical locations. Exposures at a workplace, restaurant, parking garage, apartment building, or similar site are usually addressed through posted signs at or near the point of exposure. OEHHA has issued separate templates for occupational exposures, food service establishments, and residential rental properties.¹³

Non-English information. If the product’s consumer-facing information or a facility’s signage appears in a language other than English, the warning may need to be provided in that language too.¹⁴ OEHHA publishes sample translations. The English version of the regulatory text controls where any ambiguity exists.

What Happens if You Don’t Comply

Enforcement doesn’t rely on state regulators alone. Anyone can sue “in the public interest,” and private enforcers file most Proposition 65 cases.

Before filing, a private enforcer must serve a 60-day notice of violation on the alleged violator, the California Attorney General, and the relevant local prosecutor. The notice must include a certificate of merit signed by the attorney (or the individual, if unrepresented) attesting that someone with relevant expertise has reviewed the facts and believes there is a reasonable case. If the Attorney General or a local prosecutor takes up the case and pursues it diligently during that 60-day window, the private action is blocked.¹⁵

A business found in violation faces civil penalties of up to $2,500 per violation per day the violation continues.¹⁵ Most cases settle. Settlements usually combine civil penalties, plaintiff’s attorney’s fees, and an agreement to bring the product or facility into compliance. Attorney’s fees often make up the largest share of the payment. The California Attorney General, district attorneys, city attorneys, and certain other prosecutors all have independent authority to bring enforcement actions.

Getting an Advance Opinion From OEHHA

A business that believes its product or operations don’t actually require a warning can ask OEHHA for a Safe Use Determination, which is a written opinion from the agency applying the law to a specific set of facts. To be eligible, the business must have 10 or more employees, the chemical must already be listed, and the request has to involve a current or planned activity rather than a hypothetical. OEHHA won’t issue a determination if the same matter is already in litigation, under a notice of violation, or in an administrative proceeding. A determination applies only to the specific business, product, and chemical covered; another company can’t borrow it for a similar product.¹⁶

1
Office of Environmental Health Hazard Assessment. The Proposition 65 List
2
California Legislative Information. California Health and Safety Code 25249.6
3
Office of Environmental Health Hazard Assessment. Proposition 65 List of Carcinogens or Reproductive Toxicants
4
Office of Environmental Health Hazard Assessment. Proposition 65 No Significant Risk Levels and Maximum Allowable Dose Levels
5
Office of Environmental Health Hazard Assessment. California Proposition 65 Safe Harbor Numbers Development
6
California Legislative Information. California Health and Safety Code 25249.10
7
Office of Environmental Health Hazard Assessment. Regulations on Proposition 65 Title 27, Division 4
8
California Legislative Information. California Health and Safety Code 25249.11
9
Office of Environmental Health Hazard Assessment. Title 27 California Code of Regulations Article 6 Clear and Reasonable Warnings
10
Legal Information Institute. California Code of Regulations Title 27 25602 – Methods of Transmission
11
Office of Environmental Health Hazard Assessment. Proposition 65 Clear and Reasonable Warnings – Safe Harbor Methods and Content
12
Proposition 65 Warnings Website. Frequently Asked Questions for Businesses
13
Office of Environmental Health Hazard Assessment. Proposition 65 Law and Regulations
14
Proposition 65 Warnings Website. Sample Warnings and Translations For Businesses
15
California Legislative Information. California Health and Safety Code 25249.7
16
Office of Environmental Health Hazard Assessment. Proposition 65 Safe Use Determination (SUD) Process