• Risk assessment;
  • Mosquito management;
  • Insecticides;
  • Synergists;
  • Nontarget receptors


West Nile virus (WNV) has been a concern for people across the United States since the disease was initially observed in the summer of 1999. Since 1999, WNV has caused the largest arboviral encephalitis epidemic in US history. Vector control management programs have been intensively implemented to control mosquitoes that carry WNV. Our deterministic ecological risk assessment focused on 6 common mosquito adulticides used in vector control, including 3 pyrethroids (d-phenothrin, resmethrin, and permethrin), pyrethrins, and 2 organophosphates (malathion and naled). Piperonyl butoxide, a synergist for the pyrethroids, was also assessed. Both aquatic and terrestrial nontarget organisms were considered for acute and chronic exposures to the adulticides. Tier I exposure estimates were derived from ISCST3 and AERMOD for deposition and air concentrations affecting terrestrial organisms and PRZM-EXAMS for standard pond concentrations affecting aquatic organisms. Nontargets exposed to adulticides included small mammals, birds, as well as aquatic vertebrates and invertebrates in a pond subject to receiving the chemical via drift and runoff. Risk quotients were obtained by comparing exposures to toxic endpoints. All risk quotients were low indicating that risks to ecological receptors most likely were small.