Assessing Acute Public Health Impact from Insecticide Applications for Controlling the Mosquito-Borne West Nile Virus. S. Schettler, M. R. Seeley, R. J. Blanchet, and T. S. Bowers, Gradient Corporation
West Nile Virus (WNV) was first identified in North America in New York City (NYC), in late August, 1999, following detection of an unusual cluster of encephalitis. In an attempt to control mosquito populations and reduce risk of exposure to WNV, NYC implemented a mosquito-borne disease control plan, involving potential application of insecticides. Due to potential for human exposure to occur during insecticide applications, we calculated risk-based exposure concentrations (RBCs) for acute exposures. RBCs were calculated for 5 insecticides, as well as a synergist, which are registered for use in New York. The 5 insecticides include the organophosphates malathion and naled, and the pyrethroids permethrin, resmethrin and sumithrin; the synergist is piperonyl butoxide. We evaluated exposures occurring due to inhalation of insecticide spray-drift; dermal contact due to direct-deposition of spray drift; and incidental ingestion due to hand-to-mouth behavior. For malathion and naled we used Acute Toxicity Values (ATVs) recommended by USEPA. For the pyrethroids and piperonyl butoxide we derived ATVs from relevant studies identified in USEPA’s "TOX 1-Liner" databases. Because RBCs for children will be most restrictive (i.e. lower) these RBCs were compared to maximum air concentrations immediately after spraying. RBCs ranged from 0.9 mg/m3 for naled, to 549 mg/m3 for piperonyl butoxide. For the pyrethroids and piperonyl butoxide, maximum air concentrations were well below RBCs, indicating that typical adverse health effects are not expected due to acute exposures. Although the maximum air concentration for malathion was slightly greater than the RBC (57 vs. 51 mg/m3), these concentrations are sufficiently close that typical adverse health effects are also not expected for malathion. For naled the maximum air concentration is significantly greater than the RBC (18 vs. 0.9), such that typical adverse health effects may be expected following acute exposure to naled.
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