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Listing Mechanism
Definition
A listing mechanism is one of four approved processes through which OEHHA adds chemicals to the Proposition 65 list as known to cause cancer or reproductive toxicity. The four mechanisms are: (1) the Formally Required Mechanism (chemicals identified by an authoritative body such as IARC, NTP, US EPA, or FDA as causing cancer or reproductive harm); (2) the State’s Qualified Experts mechanism (CIC or DARTIC determination based on scientific evidence review); (3) the Labor Code Mechanism (chemicals listed as occupational carcinogens under the California Labor Code); and (4) the Regulations/Administrative Action Mechanism (chemicals listed through specified state or federal regulatory processes). Each mechanism has distinct criteria, procedures, and timelines.
Source
California Health & Safety Code §25249.8; Title 27 CCR §§25302–25306 (listing mechanisms).
Practical Explanation (Compliance Context)
Understanding the listing mechanism for a specific chemical is important because it determines: the strength of evidence supporting the listing (and potentially the strength of a delisting challenge); the timeline for formal listing after a committee vote; and the regulatory context for setting safe harbour levels. Businesses using chemicals that appear on the Proposition 65 list should verify the listing mechanism and date, as this affects both their compliance obligations and potential legal defenses.