Two studies were conducted to investigate the washoff potential of pyrethroid residues arising from urban/residential use patterns.  Using a laboratory research track sprayer and indoor rainfall simulator, commercially available pyrethroid products were applied to small concrete slabs at typical label rates and subjected to a one-hour 25mm simulated rainfall event.  The first study examined washoff from 2 commercial formulations of the same active ingredient (AI) applied to a wide range of building materials including concrete, asphalt, wood, vinyl, stucco, and aluminum.  The second study further investigated the effects of formulation on driveway concrete using 17 commercial products covering a wide range of formulations and a number of different active ingredients.  Chemical analyses quantified the mass of active ingredients found in the washoff and results were expressed as percent of applied chemical washed off.  The studies found textured surfaces demonstrated reduced mass washoff compared to smoother surfaces and that, while pyrethroid AI's generally behaved similarly, different formulations could cause significant differences in washoff potential.

Washoff potential of pyrethroid products from external building materials and driveway concrete under indoor simulated rainfall conditions

248th National Meeting (2014)

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