Pyrethroid insecticides, particularly bifenthrin, frequently exceed acute toxicity thresholds for benthic and pelagic organisms in urban surface waters. Major non-agricultural sources of these insecticides to surface water include stormwater discharges and wastewater treatment plant effluents. The washoff of pyrethroid active ingredients in different formulation types (emulsifiable concentrate, suspension concentrate, granular) were measured from concrete, turf and soil in small scale rainfall simulation experiments. These experiments were used to predict formulation and surface specific washoff coefficients. Washoff coefficients were combined with historical precipitation, river flow and insecticide application data to predict pyrethroid concentrations in the American River, California, from 1995 to 2010 following calibration of the model to limited monitoring data from 2009-2010. The potential impacts of changes in insecticide formulation on water quality were predicted using the model.

Pyrethroid insecticides: Surface water quality impacts and potential solutions

243rd National Meeting (2012)

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