an outbreak of Mediterranean fruit flies in California. In order to demonstrate the chemical's safety, B. T. Collins, director of the California Conservation Corps, publicly swallowed a mouthful of dilute malathion solution. Carcinogenicity Malathion is classified by the IARC as probable carcinogen (group 2A). Malathion is classified by US EPA as having "suggestive evidence of carcinogenicity". This classification was based on the occurrence of liver tumors at excessive doses in mice and female rats and the presence of rare oral and nasal tumors in rats that occurred following exposure to very large doses. Exposure to organophosphates is associated with non-Hodgkin's lymphoma. Malathion used as a fumigant was not associated with increased cancer risk. Between 1993 and 1997, as part of the Agricultural Health Study, no clear association between malathion exposure and cancer was reported. Amphibians Malathion is toxic to leopard frog tadpoles. Resistance Because it is an acetylcholinesterase inhibitor, this resistance is a type of AChEI resistance. Malathion resistance is thought to always be due to either increased carboxylesterase concentrations or altered acetylcholinesterases. COE because it metabolizes malathion but into non-malaoxon products, altered AChEs because we mean specifically those altered to be less sensitive to malathion and malaoxon. See also Isomalathion Pesticide toxicity to bees References External links Malathion Technical Fact Sheet - National Pesticide Information Center Malathion General Fact Sheet - National Pesticide Information Center Malathion Pesticide Information Profile - Extension Toxicology Network ATSDR ToxFAQs CDC - NIOSH Pocket Guide to Chemical Hazards Re-evaluation of Malathion by the Pest Management Regulatory Agency of Canada Acetylcholinesterase inhibitors Antiparasitic agents Endocrine disruptors Insecticides Organophosphate insecticides Phosphorodithioates