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California Prop 65 Warning Requirements
Once a chemical is added to California's Proposition 65 list, businesses get a fixed clock to add warnings and, separately, to stop discharging it into drinking water sources.
Last reviewed 2026-09-27
What Prop 65 covers
Prop 65, at a glance
Proposition 65 requires California (via OEHHA, part of CalEPA) to maintain a list of chemicals known to cause cancer or reproductive/developmental harm, and requires businesses to warn Californians before knowingly and intentionally exposing them to a listed chemical above regulatory thresholds.
Businesses with fewer than 10 employees, and government agencies, are exempt from both the warning requirement and the discharge prohibition.
The list is updated at least annually; the most recent edition found was dated July 31, 2026.
A chemical can be listed through any of four mechanisms, including findings by OEHHA’s own science committees or by a designated authoritative body such as the U.S. EPA, FDA, NIOSH, the National Toxicology Program, or IARC.
OEHHA's 12-month and 20-month clocks
- Once a chemical is listed, covered businesses have 12 months to comply with the warning requirement.
- Once a chemical is listed, covered businesses have a separate 20 months to comply with the prohibition on knowingly discharging that chemical into a source of drinking water.
- OEHHA publishes 'safe harbor' numeric guidance levels (No Significant Risk Levels for carcinogens; Maximum Allowable Dose Levels for reproductive/developmental toxicants) that businesses can use to determine whether a warning is legally required.
Deadlines
- 1986-11-04 — Proposition 65 (the Safe Drinking Water and Toxic Enforcement Act of 1986) is approved by California voters at the state's general election. California Secretary of State — Historical Voter Registration and Participation in Statewide General Elections, 1910–2022as of 2026-09-27
- 2026-07-31 — Most recent Proposition 65 list edition found as of this review — check OEHHA’s list page directly for the current edition, since it is updated at least annually. OEHHA — Proposition 65 listas of 2026-09-27
How Rumzer helps
Related reading
Sources
- OEHHA — Proposition 65fetched 2026-09-27
- p65warnings.ca.govfetched 2026-09-27
- OEHHA — Proposition 65 listfetched 2026-09-27
- OEHHA — Proposition 65 in Plain Languagefetched 2026-09-27
Frequently asked questions
Questions about Prop 65.
How does Prop 65 work?
OEHHA adds a chemical to the Proposition 65 list when it meets one of four listing criteria. From that point, covered businesses have 12 months to add a warning where required, and 20 months to stop knowingly discharging the chemical into a drinking water source.
What triggers a Prop 65 warning?
A business "knowingly and intentionally" exposing a person in California to a listed chemical above the relevant safe-harbor level (the No Significant Risk Level for carcinogens, or the Maximum Allowable Dose Level for reproductive/developmental toxicants) must provide a clear and reasonable warning, unless exempt.
Is there a small-business exemption from Prop 65?
Yes — businesses with fewer than 10 employees are exempt from both the warning requirement and the discharge prohibition. Government agencies are also exempt.
How long do businesses have to comply after a Prop 65 listing?
12 months for the warning requirement, and a separate 20 months for the discharge-into-drinking-water prohibition.
Talk to us about Prop 65
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