California to Add Atrazine to Proposition 65 List

California’s Office of Environmental Health Hazard Assessment (OEHHA) intends to add the herbicide atrazine to its list of chemicals regulated under Proposition 65, a law intended to protect state residents from substances that cause cancer, birth defects, or reproductive harm. In its notice of intent to update the Proposition 65 list (PDF), OEHHA explains that atrazine meets the listing requirements due to the International Agency for Research on Cancer’s classification of the herbicide as a Group 2A carcinogen, IARC’s designation for substances that are probably carcinogenic to humans. The OEHHA notice explains that substances identified by IARC as human or animal carcinogens are required by California law to be listed as known carcinogens under Proposition 65. 

IARC’s determination is based on a “combination of limited evidence for cancer in humans and sufficient evidence for cancer in experimental animals” as well as “the combination of limited evidence for cancer in humans and strong mechanistic evidence in experimental systems,” according to a Q&A published by the agency (PDF). IARC notes that limited evidence links atrazine, which is banned in the European Union but still widely used in the U.S., with a type of non-Hodgkin lymphoma.

OEHHA is accepting public comment on whether atrazine meets the requirements for being listed under Proposition 65 as causing cancer until Nov. 9. For more information about atrazine and Proposition 65, see OEHHA’s notice.