Chemicals Listed Effective November 17, 2023 as Known to the State of California to Cause Cancer: Coal-Tar Pitch, Fluoro-Edenite Fibrous Amphibole, and Silicon Carbide Whiskers

Effective November 17, 2023, the Office of Environmental Health Hazard Assessment (OEHHA) is adding coal-tar pitch, fluoro-edenite fibrous amphibole, and silicon carbide whiskers to the list of chemicals known to the State of California to cause cancer under the Safe Drinking Water and Toxic Enforcement Act of 1986, sections 25249.5 et seq. of the Health and Safety Code, otherwise known as Proposition 65. The listing of these chemicals is pursuant to the “Labor Code” listing mechanism (Health and Safety Code, section 25249.8(a); Cal. Code of Regs., title 27, section 25904).

The basis for the listings was described in a public notice published in the September 22, 2023 issue of the California Regulatory Notice Register (Register 2023, No. 38-Z). The title of the notice is “Notice of Intent to List Chemicals by the Labor Code Mechanism: Coal-Tar Pitch, Fluoro-Edenite Fibrous Amphibole, and Silicon Carbide Whiskers.” The publication of the notice initiated a public comment period (September 22, 2023 – October 23, 2023). No comments were received during the comment period.  

A complete, updated Proposition 65 chemical list is available on the OEHHA website.

Background on Listing by the Labor Code Mechanism 

Health and Safety Code section 25249.8(a) incorporates California Labor Code section 6382(b)(1) into Proposition 65. The law requires that certain substances identified by the International Agency for Research on Cancer (IARC) be listed as known to cause cancer under Proposition 65. Labor Code section 6382(b)(1) refers to substances identified as human or animal carcinogens by IARC. OEHHA has adopted regulations concerning these listings in California Code of Regulations (CCR), title 27, section 25904. As the lead agency for the implementation of Proposition 65, OEHHA evaluates whether a chemical’s listing is required.

OEHHA’s Determination 

Coal-tar pitch, fluoro-edenite fibrous amphibole, and silicon carbide whiskers meet the requirements for listing as known to the state to cause cancer for purposes of Proposition 65 (CCR, title 27, section 25904(b)(3)).

IARC has published on its website “IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 100F, Chemical Agents and Related Occupations" (IARC, 2012) and “IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 111, Some Nanomaterials and Some Fibres” (IARC, 2017). IARC concluded that coal-tar pitch and fluoro-edenite fibrous amphibole are classified in Group 1 (“carcinogenic to humans”) and that silicon carbide whiskers are classified in Group 2A (“probably carcinogenic to humans”). IARC concluded that there is sufficient evidence of carcinogenicity in humans and animals for coal-tar pitch and fluoro-edenite fibrous amphibole (IARC, 2012; IARC, 2017). IARC concluded that there is sufficient evidence of carcinogenicity in animals for silicon carbide whiskers (IARC, 2017).