IARC: Herbicides Atrazine and Alachlor Are "Probably Carcinogenic"
The International Agency for Research on Cancer (IARC) has classified the herbicides atrazine and alachlor as Group 2A carcinogens, the agency’s designation for substances that are probably carcinogenic to humans. According to a Q&A published by IARC (PDF), the two herbicides are probable human carcinogens due to 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.” IARC’s findings are described in an article published online on Nov. 21 in The Lancet Oncology. Further details will appear later in a new volume of the agency’s monographs series.
Limited evidence links atrazine, which is banned in the European Union but still heavily used in the U.S. and in countries in Africa, Asia, and Latin America, with a type of non-Hodgkin lymphoma. And one large cohort study of pesticide applicators found that alachlor, which IARC describes as “once one of the most heavily used herbicides globally,” may cause laryngeal cancer in humans. Alachlor use today is down following regulatory restrictions on the herbicide that the agency says began in the 1990s. Both atrazine and alachlor are used on crops such as corn, but atrazine is also used to treat turf and lawns.
“For each of these pesticides, factory and agricultural workers have the highest exposures, which can occur during pesticide production and agricultural or horticultural activities, primarily via inhalation and dermal absorption,” the Lancet Oncology article explains.
IARC also evaluated the carcinogenicity of the fungicide vinclozolin, which it says is mainly used on fruits and vegetables. The agency classified vinclozolin as possibly carcinogenic to humans, in Group 2B, based on “sufficient evidence for cancer in experimental animals and strong mechanistic evidence in experimental systems.” According to IARC, vinclozolin is still used in some countries but is restricted in the U.S. and has been withdrawn from the European Union.
A summary of IARC’s evaluation can be found in The Lancet Oncology. The full article is available free of charge to registered users (registration is also free). Further details can be found in a news article on IARC’s website.