A Proposition 65 notice is the “WARNING” you see on California products, buildings, and parking garages telling you that being there or using the item may expose you to a chemical the state has identified as causing cancer or reproductive harm. It comes from California’s Safe Drinking Water and Toxic Enforcement Act of 1986, and it applies to almost every business with ten or more employees that sells into or operates in California.1Office of Environmental Health Hazard Assessment. Proposition 65 The rule behind it is simple: no business can knowingly expose anyone in California to a listed chemical without first giving a “clear and reasonable warning.”2California Legislative Information. California Code Health and Safety Code 25249.6 – Required Warning Before Exposure to Chemicals Known to Cause Cancer or Reproductive Toxicity
The Office of Environmental Health Hazard Assessment (OEHHA) keeps the official list, which currently runs to roughly 875 chemicals covering everything from lead and mercury to acrylamide, bisphenol A, and inorganic arsenic.3Office of Environmental Health Hazard Assessment. The Proposition 65 List The list is updated regularly, so compliance is not a one-time job.
What a Compliant Notice Must Contain
A business can technically warn in any way that qualifies as “clear and reasonable,” but OEHHA has published specific formatting rules that give a warning “safe harbor” — meaning a court will treat it as legally adequate if challenged. Nearly every business follows the safe harbor format because anything else invites a fight.
A safe harbor Prop 65 notice must include:
- A yellow equilateral triangle with a black outline containing a bold black exclamation point. Black-and-white is acceptable if the rest of the label is not printed in color.4California Office of Environmental Health Hazard Assessment. Warning Symbol – Proposition 65 Warnings
- The signal word WARNING in all capitals and bold.
- A statement that the product or area can expose the consumer to a chemical known to the State of California to cause cancer, birth defects, or other reproductive harm, plus a reference to www.P65Warnings.ca.gov.
- The name of at least one listed chemical the product or place exposes you to.
- The warning in any non-English language that also appears in the consumer information on the product label.
The chemical-naming rule is where the format is tightening. Products manufactured and labeled before January 1, 2028 can still use the older short-form warning that did not name a specific chemical. From that date forward, even short-form warnings have to name at least one chemical for each hazard endpoint (cancer, reproductive harm, or both).5California Office of Environmental Health Hazard Assessment. Frequently Asked Questions for Businesses
How the Notice Has to Reach the Consumer
The warning has to reach the person before the exposure, and the delivery method depends on how the product is sold or where the exposure happens.
On Products in Stores
A manufacturer can print the warning directly on the packaging, or it can send written notice and warning materials to the retailer, who then posts shelf tags, signs, or another conspicuous display near the product.6Legal Information Institute. California Code of Regulations Title 27 25600.2 – Responsibility to Provide Warnings Retailers are generally not on the hook for product warnings when the manufacturer has handled labeling. The main exceptions: the retailer sells the product under its own brand, has covered or altered an existing warning, or has actual knowledge of the exposure and no manufacturer is reachable in California. Manufacturers and retailers can also allocate warning responsibility between themselves by written agreement, so long as the consumer still gets an adequate warning.
Online and Catalog Sales
For internet sales, the warning has to appear on the product display page, or through a clearly marked hyperlink using the word “WARNING” that leads to the full warning text, or otherwise be shown prominently before checkout. A notice buried in terms of service or sent in a post-purchase confirmation email does not satisfy the rule.
Buildings, Garages, and Apartments
For environmental exposures inside a building, parking structure, or apartment complex, businesses post the notice at public entrances so someone would see it before walking in. Placement has to be prominent enough that a reasonable person would notice before encountering the chemical.
When a Notice Is Actually Required
A chemical being on the list does not automatically trigger a warning. If the exposure a product or place creates is low enough, no notice is required.
For carcinogens, the threshold is the No Significant Risk Level (NSRL), 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 equivalent is the Maximum Allowable Dose Level (MADL), set at one-thousandth of the level that produced no observable reproductive harm in studies.7California Legislative Information. California Code Health and Safety Code 25249.10 Below those levels, the warning requirement does not apply.
The catch is that the burden of proving the exposure is below the threshold sits entirely on the business. There is no penalty for over-warning, and there can be significant liability for guessing wrong on the low side. That asymmetry is why so many products carry a Prop 65 notice regardless of the actual risk.
Grace Period for New Chemicals
When OEHHA adds a chemical to the list, businesses have 12 months before the warning requirement takes effect for that chemical.7California Legislative Information. California Code Health and Safety Code 25249.10 Within that window, a business cannot be sued for failing to warn about the newly listed chemical.
Who Doesn’t Have to Warn
Three categories fall outside the notice rule entirely:
- Businesses with fewer than ten employees.8California Legislative Information. California Code HSC 25249.11 – Definitions
- Government agencies at the city, county, state, and federal level.
- Public water systems, which are governed by separate drinking water rules.
The employee-count exemption is the one businesses ask about most. The statute does not spell out how to count part-time workers or independent contractors toward the ten-person threshold.9Office of Environmental Health Hazard Assessment. Businesses and Proposition 65 A business that crosses the line mid-year is subject to the warning rule immediately, with no separate grace period for growing past nine employees.
Penalties for a Missing or Defective Notice
Prop 65 violations carry civil penalties of up to $2,500 per day for each violation.10California Legislative Information. California Code HSC 25249.7 – Enforcement Enforcement runs on two tracks. The Attorney General, district attorneys, and city attorneys can bring cases, but most Prop 65 enforcement is done by private citizens and organizations acting as “private attorneys general.” A private plaintiff who wins keeps 25% of any civil penalties and recovers attorney’s fees on top; the remaining 75% goes to OEHHA.11California Department of Justice. Regulations
Before filing suit, a private enforcer has to serve a 60-day written notice on the alleged violator, the Attorney General, and the local district attorney or city attorney. A notice targeting a warning violation must include a certificate of merit, signed by someone stating they have consulted with a person who has relevant expertise and believes there is a reasonable case.10California Legislative Information. California Code HSC 25249.7 – Enforcement If the Attorney General or a local prosecutor takes the case and pursues it diligently within the 60-day window, the private suit is barred. Otherwise, the private plaintiff can proceed.
If You Receive a 60-Day Notice
A 60-day notice is not a lawsuit yet, but ignoring it is expensive. Many cases settle, and attorney’s fees in settlements routinely exceed the penalty amounts themselves. The realistic response is to evaluate the alleged exposure, assess whether a warning was required, and either fix the labeling or negotiate a settlement well before the 60 days run out.
Why You See These Notices Everywhere
The reason the same yellow triangle appears on a parking garage, a coffee shop, a hardware store aisle, and a bag of chips is largely economic. Testing every product against NSRL and MADL thresholds costs money; posting a warning does not. With daily penalties of up to $2,500 and any citizen able to file suit, blanket warnings are the cheaper hedge for many businesses. Researchers have described the result as “warning fatigue,” where notices lose their power because they are everywhere.
OEHHA’s push to require specific chemical names in warnings, including the 2028 extension of that requirement to short-form warnings, is aimed at making the notices actually informative.5California Office of Environmental Health Hazard Assessment. Frequently Asked Questions for Businesses For a consumer looking at a notice today, the practical move is to check the chemical name (if one is listed) and the P65Warnings.ca.gov reference on the warning itself for information on what the exposure is and how it typically occurs.