In March 2015 the International Agency for Research on Cancer (IARC) reviewed the scientific literature on five pesticides as part of the monograph program to evaluate the carcinogenic risks of chemicals. In particular, the IARC working group classified the organophosphate insecticides malathion and diazinon, and the herbicide glyphosate as probable human carcinogens. Two other organophosphate insecticides, tetrachlorvinphos and parathion were classified as possible human carcinogens. (Guyton KZ, Loomis D, Grosse Y, et al. Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon, and glyphosate. Lancet Oncol 2015 Mar 20. E-pub ahead of print).
The consensus decisions were based on epidemiologic data, animal bioassays and mechanistic studies. Data from large case-control and cohort studies, including the Agricultural Health Study, from DCEG investigators that showed increased risks of non-Hodgkin lymphoma (De Roos, 2003; Alavanja, 2014), and cancers of the lung (Beane Freeman, 2005; Jones, in press) and prostate (Koutros, 2013) made important contributions to these evaluations. Former OEEB Branch Chief Aaron Blair (now Emeritus) chaired the IARC meeting. IARC is planning a review of some organochlorine insecticides and some chlorphenoxy herbicides in May 2015.