Using field data to assess the effects of pesticides on Crustacea in freshwater aquatic ecosystems and verifying the level of protection provided by water quality guidelines

The authors developed a model to determine how many crustacean taxa are adversely impacted by contamination at water quality standard levels and for seven days following exposure. Based on a review of papers evaluating Daphnia magna and other crustacean toxicology, they identified mesocosm studies that allowed them to establish the levels at which species are harmed by pesticide doses. They used field pesticide measurements to convert them to toxicity units (by dividing by the LC50, EC50, or 5% hazard concentration). The toxicity unit model was then used to convert pesticide water quality guidelines into estimates of the proportion of taxa that would be impacted by a pesticide if found at various water quality guidelines. Water quality guidelines from the US, Canada, UK, Australia and New Zealand, and the EU for different active ingredients. Their analysis found that 63% of chronic water quality guidelines and 88% of acute guidelines are not protective of crustaceans and could lead to adverse impacts in species. In particular, several of the US EPA guidelines, including imidacloprid, may affect more than 50% of crustaceans in natural lentic systems (the guidelines are intended to be protective of at least 95% of species). These results suggest that water quality standards based on single species tests may not be adequate to protect crustaceans. Since the model only accounted for results up to seven days after application, it may not include potential post-exposure recovery. The authors suggest that interspecific differences in pesticide susceptibility and the interactions of pesticides with water bodies should be accounted for more thoroughly in water quality guidelines to ensure their effectiveness.

Guy, M., L. Singh, and P. Mineau
Integrated Environmental Assessment and Management
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