Proposition 65 - California

California Proposition 65 - In Plain English

What is Proposition 65?

Proposition 65—or as it is commonly called, Prop. 65—is the Safe Drinking Water and Toxic Enforcement Act of 1986, a ballot initiative [link to attached] passed by the voters in November 1986. It is administered by the Office of Environmental Health Hazard Assessment (OEHHA), which is part of the California Environmental Protection Agency (Cal/EPA).

What does Proposition 65 do?

Prop. 65 provides that persons doing business in California may not expose individuals to chemicals known to cause cancer and/or reproductive toxicity without first giving clear and reasonable warning, nor discharge such chemicals into drinking water.

Prop. 65 requires the State to publish a list of chemicals known to cause cancer or birth defects or reproductive harm. The list was first published in 1987 and is updated at least once a year. There are currently over 800 chemicals and substances on the list. The list is administered by OEHHA.

The list of chemicals include both individual chemicals and categories of chemicals. The chemical may be present, for example, in common household products such as food, drugs, dyes, or solvents. Listed chemicals may also be used in manufacturing and construction, or they may be byproducts of chemical processes, such as motor vehicle exhaust.

How does a chemical get on the list?

A chemical can be placed on the list in any of the following four ways:

    State's Qualified Experts Mechanism

    The Governor appoints the members to the Science Advisory Board and they are designated as the "State's Qualified Experts." The Science Advisory Board evaluates chemicals to determine if they have been clearly shown to cause cancer or birth defects or other reproductive harm. The Board consists of two independent committees of scientists and health professionals:

    OEHHA staff scientists compile relevant scientific evidence on various chemicals for the committees to review before making their decisions whether to list a chemical.

    Authoritative Body Mechanism

    Chemicals can be listed if an organization designated as an "authoritative body" by the state's Science Advisory Board has identified the chemical as causing cancer or birth defects or other reproductive harm. The designated authoritative bodies are:

    • U.S. Environmental Protection Agency
    • U.S. Food and Drug Administration
    • National Institute for Occupational Safety and Health
    • National Toxicology Program
    • International Agency for Research on Cancer

    Formally Required to Label Mechanism

    A chemical can be listed if an agency of the state or federal government requires that the chemical be labeled or identified as causing cancer or birth defects or other reproductive harm. Most chemicals listed in this manner are prescription drugs that are required by the U.S. FDA to contain warnings relating to cancer or birth defects or other reproductive harm.

    Labor Code Listing Mechanism

    Chemicals meeting certain scientific criteria and identified by the California Labor Code as causing cancer or birth defects or other reproductive harm. This method established the initial chemical list following voter approval of Prop. 65 in 1986 and continues to be used as a basis for listing as appropriate.


Warning Requirement

Businesses are required to provide a "clear and reasonable" warning before knowingly and intentionally exposing anyone to a listed chemical. This warning can be given by a variety of means, such as by labeling a consumer product, posting signs at the workplace, distributing notices at a rental housing complex, or publishing notices in a newspaper. A business may choose to provide a warning simply based on its knowledge, or assumption, about the presence of a listed chemical without attempting to evaluate the levels of exposure. Manufacturers, distributors, and retailers are subject to the warning requirement regardless if they are located in California or not. Once a chemical is listed, businesses have 12 months to comply with warning requirements.


  • "Knowingly" means aware that the chemical was present. The courts have interpreted this phrase very broadly.
  • "Intentionally" means intending to sell a product or perform some other act, with the requisite knowledge.

Discharge Prohibition

Prop. 65 also prohibits companies that do business within California from knowingly discharging listed chemicals into sources of drinking water. Once a chemical is listed, businesses have 20 months to comply with the discharge prohibition. "Source of drinking water" is very broadly defined as "either a present source of drinking water or water which is identified or designated in a water quality control plan adopted by a regional board as being suitable for domestic or municipal uses." A "significant" amount is any detectable amount, unless the discharger can show that the amount would meet the "no significant risk" or "no observable effect" test for carcinogens and developmental toxins, respectively.


Businesses with less than 10 employees and government agencies are exempt from Prop. 65's warning requirements and prohibition on discharges into drinking water sources. Businesses are also exempt from the warning requirement and discharge prohibition if the exposures they cause are so low as to create no significant risk of cancer or birth defects or other reproductive harm.

How much of the chemical needs to be present before a company must provide a warning?

Of the over 800 substances that are on the list of chemicals known to cause cancer, birth defects or other reproductive harm, OEHHA has developed threshold levels for about 300 of the chemicals to guide businesses in determining whether a warning is necessary or whether discharges of a chemical into drinking water source are prohibited. If the chemical is at or below the levels listed, it is known as a "safe harbor" from Prop. 65 warning requirements or discharge prohibitions. These safe harbor numbers consist of no significant risk levels (NSRLs) for chemicals listed as causing cancer and maximum allowable dose levels (MADLs) for chemicals listed as causing birth defects or other reproductive harm. If there is no safe harbor number established then it is the burden of the business to prove there is no risk.

For carcinogens, the "no significant risk level (NSRL)" is the level of exposure that would result in no more than one excess case of cancer in 100,000 individuals exposed to the chemical over a 70-year lifetime. In other words, a person exposed to the chemical at the NSRL for 70 years would not have more than a "one in 100,000" chance of developing cancer as a result of that exposure.

For developmental toxins (birth defects or other reproductive harm), the "no observable effect level (NOEL)" is determined by identifying the level of exposure that has been shown to not pose any harm to humans or laboratory animals. Prop. 65 then requires the NOEL to be divided by 1,000 in order to provide an ample margin of safety. The maximum allowable dose level (MADL) is the level at which a chemical would have no observable effect assuming exposure at 1,000 times that level. Thus, businesses subject to Prop. 65 must provide a warning if they cause exposures to developmental or reproductive toxicant chemicals at a level over 1/1000th of the "no observable effect level."

What must the warning say?

The statute governing Prop. 65 provides some "safe harbor" warning language for consumer products:

  • For carcinogens: "WARNING: This product contains a chemical known to the State of California to cause cancer."
  • For reproductive toxins: "WARNING: This product contains a chemical known to the State of California to cause birth defects or other reproductive harm."

Other safe harbor warning language has been established for occupational and environmental exposures, for alcoholic beverages, and for restaurants. Without safe harbor warning, specific warning language must be negotiated to prevent potential liability.

How is Proposition 65 enforced?

Prop. 65 is not enforced by OEHHA or any other governmental regulatory agency. Instead it is enforced when legal action is brought against a business that allegedly has failed to warn or has discharged a listed chemical into a source of drinking water. There are three ways that Prop. 65 can be enforced:

  • The California Attorney General can bring a Prop. 65 enforcement action.
  • Any district attorney or city attorney (for cities whose population exceeds 750,000) may also enforce Prop. 65. Any party (individual or group) acting in the public interest may enforce Prop. 65 by filing a lawsuit against a business alleged to be in violation of the law.

Penalties for violating Prop. 65 by failing to provide warnings can be as high as $2,500 per day for each violation.

How is a business notified that it may be in violation of Proposition 65?

A party, acting in the public interest and alleging that a business is in violation, must first send the business a notice of the alleged violation 60 days before filing a suit. This is known as a 60-day notice letter. In the interim, the Attorney General may take over the case. Public prosecutors do not need to send 60-day notices.

Because Prop. 65 is not enforced by a government agency, a business should seek legal advice upon receiving a 60-day notice letter.

Where can I get more information on Proposition 65?

For general information on the Prop. 65 list of chemicals, go to OEHHA's Prop. 65 program or call 916-445-6900.

For enforcement information, go to California Attorney General's Office or call 510-622-2160.

For Prop. 65 experts in litigation, chemical testing labs or consultants go to Prop. 65 Clearinghouse Experts or call 415-391-9808.


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