Chemicals Listed Effective January 27, 2023 as Known to the State of California to Cause Cancer: 1-Bromo-3-Chloropropane, 1-Butyl Glycidyl Ether, and Glycidyl Methacrylate

Effective January 27, 2023, the Office of Environmental Health Hazard Assessment (OEHHA) is adding 1-bromo-3-chloropropane (CAS RN 109-70-6), 1-butyl glycidyl ether (CAS RN 2426-08-6), and glycidyl methacrylate (CAS RN 106-91-2) to the list of chemicals known to the State of California to cause cancer for purposes of Proposition 65^[1]. The listing of these chemicals is pursuant to the “Labor Code” listing mechanism^[2]. The warning requirement for significant exposures to these chemicals will take effect on January 27, 2024.

The basis for the listings was described in a public notice published in the December 2, 2022, issue of the California Regulatory Notice Register (Register 2022, No. 48-Z). The title of the notice was “Notice of Intent to List Chemicals by the Labor Code Mechanism: 1-Bromo-3-Chloropropane; 1-Butyl Glycidyl Ether; and Glycidyl Methacrylate.” The publication of the notice initiated a public comment period (December 2, 2022 – January 9, 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 Title 27, Cal. Code of Regs., section 25904. As the lead agency for the implementation of Proposition 65, OEHHA evaluates whether a chemical’s listing is required.

OEHHA’s Determination 

1-Bromo-3-chloropropane, 1-butyl glycidyl ether, and glycidyl methacrylate meet the requirements for listing as known to the state to cause cancer for purposes of Proposition 65.

IARC has published on its website “IARC Monographs on the Identification of Carcinogenic Hazards to Humans, Volume 125 “Some Industrial Chemical Intermediates and Solvents” (IARC, 2020).  IARC concluded that 1-bromo-3-chloropropane and 1‑butyl glycidyl ether are “possibly carcinogenic to humans” (Group 2B) based on sufficient evidence of carcinogenicity in animals and strong evidence in experimental systems that they each exhibit key characteristics of carcinogens (IARC, 2020).  IARC concluded that glycidyl methacrylate is “probably carcinogenic to humans” (Group 2A) based on sufficient evidence of carcinogenicity in animals, strong evidence that the chemical belongs, on the basis of mechanistic considerations, to a class of reactive glycidyl epoxides, and strong evidence in human primary cells that the chemical exhibits key characteristics of carcinogens (IARC, 2020).