title: Mutagenic and alkylating activities of organophosphate impurities of commercial malathion.
abstract: The purpose of this study was to determine if 4 major organophosphate impurities of malathion were active as alkylators of nitrobenzylpyridine (NBP) or as mutagens in the Salmonella typhimurium bioassay. Malathion, isomalathion, O,O,O-trimethyl phosphorothioate, O,O,S-trimethyl phosphorothioate, and O,S,S-trimethyl phosphorodithioate produced alkylated NBP at varying rates. In order of increasing NBP reactivity, the compounds ranked: O,O,O-trimethyl phosphorothioate = O,O,S-trimethyl phosphorothioate less than O,S,S-trimethyl phosphorodithioate less than isomalathion = malathion. At 37 degrees C, the most reactive compounds produced an NBP alkylation rate equal to approximately 25% of the rate produced by methyl methanesulfonate, a potent Salmonella mutagen. However, none of the organophosphates were mutagenic in S. typhimurium TA97, TA98 and TA100 when tested by the standard plate-incorporation method or by the preincubation modification of the plate-incorporation method. The possible relationships between NBP reactivity and the biological activities of these organophosphates are discussed.
mesh_terms: D000477:Alkylating Agents; D008294:Malathion / Q000031:analogs & derivatives / Q000633:toxicity*; D009152:Mutagenicity Tests; D009153:Mutagens; D012486:Salmonella typhimurium / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D000477:Alkylating Agents; D009153:Mutagens; D008294:Malathion