Mutagenic and alkylating activities of organophosphate impurities of commercial malathion

Mutat Res. 1985 Jan-Feb;155(1-2):1-6. doi: 10.1016/0165-1218(85)90018-7.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alkylating Agents*
  • Malathion / analogs & derivatives
  • Malathion / toxicity*
  • Mutagenicity Tests
  • Mutagens*
  • Salmonella typhimurium / drug effects
  • Structure-Activity Relationship


  • Alkylating Agents
  • Mutagens
  • Malathion