Prop 65 Warning Labels: Requirements, Responsibility, and Penalties

Proposition 65 warning labels are notices California requires on products, buildings, and workplaces when a business knowingly exposes people to any of more than 900 chemicals the state has linked to cancer, birth defects, or other reproductive harm.¹ They come from the Safe Drinking Water and Toxic Enforcement Act of 1986, a voter-approved initiative, and they reach far beyond California because any company with 10 or more employees selling into the state has to comply.

What a Prop 65 Warning Actually Tells You

A warning does not mean the product will make you sick. It means the product contains a listed chemical at a level the business has not confirmed to be below the state’s safe-harbor threshold. Many companies choose to add a warning as a precaution rather than pay to test their products and prove the exposure is low enough to skip the label. The result: warnings appear on items where the real risk ranges from meaningful to negligible.

This “overwarning” problem is well documented. When the same yellow triangle turns up on coffee, lumber, shoes, and an amusement park entrance, the label starts to fade into background noise, and research has found many consumers ignore the warnings entirely. The labels still do useful work for chemicals with well-established risks at common exposure levels, like lead in certain ceramics or cadmium in jewelry. The practical read: pay closer attention to a warning that names a specific chemical you can research than to a generic notice that names nothing.

What Has To Appear on the Label

California’s regulations spell out how a Prop 65 warning must look. Every warning includes a triangular symbol showing a black exclamation point inside a yellow triangle with a black border, the word “WARNING” in bold capital letters, and language identifying the type of harm.² When the product label is not printed in color, the symbol can be black and white. The warning text can never appear smaller than 6-point type.³

Long-Form Warnings

A long-form warning names at least one specific chemical and spells out the harm. For a carcinogen, it reads something like: “This product can expose you to chemicals including [chemical name], which is known to the State of California to cause cancer.” For reproductive toxicants, the language swaps to “birth defects or other reproductive harm.” Products containing both types of chemicals combine the statements, and every version points to www.P65Warnings.ca.gov.²

Short-Form Warnings and the 2028 Change

A condensed short-form warning is available for product labels, and under current regulations it must also name the specific chemical. It uses briefer language such as “Cancer risk from exposure to [chemical name]” or “Can expose you to [chemical name], a carcinogen,” followed by the P65Warnings.ca.gov reference.⁴ Products manufactured and labeled before January 1, 2028, can still use an older short-form format that does not identify the chemical.⁵ After that date, every short-form warning has to name the substance. Until then, the nameless version you see on an older package is still legal.

Warnings on Online Listings

Products sold online must carry a Prop 65 warning before checkout. The regulations offer three acceptable methods: showing the full warning on the product listing page, providing a clearly marked hyperlink using the word “WARNING” (or “CA WARNING” or “CALIFORNIA WARNING”) that links to the warning text, or otherwise prominently displaying the warning before the sale.³ Burying it in general site content does not count. If the physical product uses a short-form label, the online notice can use the same short-form text.

Which Businesses Have To Warn

The warning duty falls on any “person in the course of doing business” with 10 or more employees, whether full-time or part-time.⁶ That definition reaches well beyond California headquarters. If your product ends up on a California shelf or in a California online cart, you are covered.

Three categories fall outside the definition:

Companies with fewer than 10 employees.
Federal, state, and local government agencies.
Entities operating public water systems.

Those carve-outs focus the compliance burden on mid-size and larger commercial operations.⁶

How a Chemical Gets on the List, and When a Warning Kicks In

The Office of Environmental Health Hazard Assessment (OEHHA) maintains the official registry, updates it at least once a year, and currently lists over 900 substances spanning heavy metals like lead, combustion byproducts, pesticides, pharmaceutical ingredients, and common industrial additives.⁷ A chemical’s mere presence in a product is not the trigger, though. The trigger is exposure above a safe-harbor level.

For carcinogens, that level is called a No Significant Risk Level (NSRL): the daily exposure that would cause no more than one additional cancer case in 100,000 people exposed daily over a lifetime.⁸ For reproductive toxicants, it is a Maximum Allowable Dose Level (MADL): the highest dose showing no observable reproductive effect, divided by 1,000 to build in a safety buffer.⁹ A business whose product exposes users below these thresholds does not have to warn, but the business carries the burden of proving it. OEHHA has published NSRL or MADL values for many listed chemicals but not all; where no official number exists, a company can rely on its own scientifically valid risk assessment, held to the same standards OEHHA uses.¹⁰

The statute targets “knowing and intentional” exposure. A business does not have to prove its product is dangerous at the level present. If a listed chemical is there above the threshold and the business knows about it, the warning has to appear.

Signs in Buildings, Parking Garages, and Workplaces

Prop 65 warnings are not just for product labels. Businesses must post them at physical locations where exposures happen. Enclosed parking garages need signs at every vehicle and pedestrian entrance, at least 20 by 20 inches with 72-point type, readable under normal lighting. When other entrance signage appears in languages besides English, the Prop 65 sign has to match. Designated smoking areas require signs at the entrance and inside the area.

Apartment buildings and other rental properties handle it differently. For exposure sources other than parking garages or smoking areas, owners with 10 or more employees can deliver the warning through a lease addendum or annual notice instead of a physical sign. Workplace warnings follow similar logic: if a business knows employees are exposed to listed chemicals on the job, it has to provide notice. An employee who sees a posted warning can ask the property manager or employer which specific chemical prompted it.

Who Is Responsible: Manufacturer or Retailer

Primary responsibility sits upstream, with the manufacturer, producer, packager, importer, or distributor. Those parties must either put the warning on the product label or send written notice and warning materials to the retailer.⁵ Retailers must then place and maintain the warnings they receive. A retailer who peels off a warning sticker or covers a label takes on full liability.

Retailers pick up direct responsibility in a few other situations: when they sell a product under their own brand or private label, when they knowingly add a listed chemical, or when they have actual knowledge of an exposure and no upstream party has a California agent or place of business.¹¹ “Actual knowledge” here means the retailer has received specific, reliable information identifying the product causing the exposure. Manufacturers and retailers can also sign written agreements to reallocate responsibility between themselves.

Enforcement and Penalties

The Attorney General, district attorneys, and city attorneys can all enforce Prop 65, but most enforcement comes from private parties suing “in the public interest.” Before filing, a private plaintiff must send a written 60-day notice to the alleged violator, the Attorney General, and the local district attorney or city attorney.¹² That window lets public prosecutors take over the case. If none step in within 60 days, the private lawsuit can go forward.

Civil penalties run up to $2,500 per day for each violation.¹² Because the amount accrues daily and per violation, a company selling several unlabeled products can rack up serious liability fast. Courts weigh the nature and severity of the violation, the economic effect of the penalty on the violator, whether the business made good-faith efforts to comply, and the deterrent value of the fine. The private-enforcement structure also lets prevailing plaintiffs recover attorney fees, which is a large part of why so many companies attach warnings by default rather than test their way out of them.

1
Office of Environmental Health Hazard Assessment. Proposition 65
2
Legal Information Institute. California Code of Regulations Title 27, 25603 – Consumer Product Exposure Warnings – Content
3
New York Codes, Rules and Regulations. California Code of Regulations Title 27, 25602 – Consumer Product Exposure Warnings – Methods of Transmission
4
New York Codes, Rules and Regulations. California Code of Regulations Title 27, 25603 – Consumer Product Exposure Warnings – Content
5
P65Warnings.ca.gov. Frequently Asked Questions for Businesses
6
California Legislative Information. California Health and Safety Code 25249.11 – Definitions
7
Office of Environmental Health Hazard Assessment. How Chemicals Are Added to the Proposition 65 List
8
Legal Information Institute. California Code of Regulations Title 27, 25705 – Specific Regulatory Levels Posing No Significant Risk
9
Legal Information Institute. California Code of Regulations Title 27, 25801 – General
10
Office of Environmental Health Hazard Assessment. Proposition 65 No Significant Risk Levels (NSRLs) and Maximum Allowable Dose Levels (MADLs)
11
Cornell Law School. California Code of Regulations Title 27, 25600.2 – Responsibility to Provide Consumer Product Exposure Warnings
12
California Legislative Information. California Health and Safety Code 25249.7