Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 4361
Title: The interactive neurobehavioral toxicity of diazinon, malathion, and ethoprop to juvenile coho salmon
Author: C. A. Laetz, D. H. Baldwin, V. Hebert, John D. Stark, N. L. Scholz
Publication Year: 2013
Journal: Environmental Science & Technology
Volume: 47
Issue: 6
Pages: 2925-2931
Keywords: pesticides,toxicity,AChE,organophosphate

In western North America, mixtures of current use pesticides have been widely detected in streams and other aquatic habitats for threatened and endangered Pacific salmon and steelhead (Oncorhynchus sp.). These include organophosphate insecticides that inhibit acetylcholinesterase (AChE) enzyme activity in the salmon nervous system, thereby disrupting swimming and feeding behaviors. Several organophosphates have been shown to interact as mixtures to produce synergistic AChE inhibition at concentrations near or above the upper range of surface water detections in freshwater systems. To evaluate potential synergism at lower concentrations (near or below 1 part per billion), juvenile coho (Oncorhynchus kisutch) were exposed to a range of mixtures of diazinon-malathion and ethoprop-malathion below a cumulative 0.05 of the predicted EC50 for AChE inhibition, as determined from single chemical concentration−response curves. Brain enzyme inhibition was concentration-dependent, with a 90% reduction and a significant decrease in spontaneous swimming speed at the highest binary mixture concentrations evaluated (diazinon-malathion at 2.6 and 1.1 μg/L, respectively; ethoprop-malathion at 2.8 and 1.2 μg/L, respectively). Brain enzyme activity gradually recovered over six weeks. Our findings extend earlier observations of organophosphate synergism in salmon and reveal an unusually steep concentration−response relationship across a mere 2-fold increase in mixture concentration.

Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize habitat effects on ecosystem processes, ecological interactions and the health of organisms.