title: Joint acute toxicity of esfenvalerate and diazinon to larval fathead minnows (Pimephales promelas).
abstract: California (USA) agriculture employs pyrethroid and organophosphate insecticides to control insects in orchards and other crops. Diazinon and esfenvalerate were selected for this study because of their application overlaps. Toxicological and biochemical responses of larval fathead minnows (Pimephales promelas) exposed singly and in combinations to esfenvalerate and diazinon were determined. Exposures were 96-h static renewal tests that used standard U.S. Environmental Protection Agency acute toxicity test methods. After pesticide exposures, larvae were evaluated for carboxylesterase and acetylcholinesterase activity, and histopathological effects. Carboxylesterase activity was examined because of its potential influence on the toxicity of both organophosphates and pyrethroids. In vivo studies demonstrated that diazinon significantly inhibited carboxylesterase activity at nominal water concentrations as low as 50 microg/L. However, esfenvalerate did not affect carboxylesterase activity at any concentration tested. Liver glycogen depletion was the only histopathological effect observed; this effect was demonstrated with the individual pesticides and pesticide combinations (i.e., mixtures). The combinations of diazinon and esfenvalerate causing acute toxicity to fathead minnow larvae appeared to be greater than additive (i.e., synergistic) in all three tests.
authors.affiliation: U.S. Environmental Protection Agency, Region IX, Sacramento, California 95814, USA. denton.debra@epa.gov
authors.forename: Debra L
authors.initials: DL
authors.lastname: Denton
authors.forename: Craig E
authors.initials: CE
authors.lastname: Wheelock
authors.forename: Shauna A
authors.initials: SA
authors.lastname: Murray
authors.forename: Linda A
authors.initials: LA
authors.lastname: Deanovic
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Hammock
authors.forename: David E
authors.initials: DE
authors.lastname: Hinton
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D043182:Carboxylesterase; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors; D003530:Cyprinidae / Q000254:growth & development* / Q000378:metabolism; D003976:Diazinon / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000633:toxicity*; D007814:Larva / Q000201:enzymology / Q000254:growth & development; D007928:Lethal Dose 50; D009570:Nitriles; D011722:Pyrethrins / Q000633:toxicity*; D013997:Time Factors; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D004791:Enzyme Inhibitors; D009570:Nitriles; D011722:Pyrethrins; D014874:Water Pollutants, Chemical; D002265:Carboxylic Ester Hydrolases; D043182:Carboxylesterase; D000110:Acetylcholinesterase; D003976:Diazinon; C017690:fenvalerate