Evaluating Human Health Risk of Aerial Ultra-Low Volume Insecticide Applications for Adult Mosquito Management

HIGHLIGHTS Two models estimated potential exposure to naled, an organophosphate insecticide, during ultra-low volume adult mosquito control applications. The estimated maximum exposure was well below EPA reference dose values. When naled is used for mosquito control following label guidelines, human health risk is negligible. ABSTRACT. Risk characterization for insecticides used in mosquito management requires assessment of exposure amount, frequency, timing, and likelihood of contact. Naled (Dibrom, AMVAC Chemical Corporation, Commerce, CA), the insecticide used for this study, is an organophosphate employed for adult mosquito management because of predicted low environmental effects in wetland habitats, high relative density of droplets, and excellent efficacy against mosquitoes. Our study used the current United States Environmental Protection Agency reference dose (RfD) of naled, 0.01 mg/kg body weight per day, and human data were configured for a 78 kg (172 lb) adult and 10 kg (22 lb) child located at the highest concentration in the deposition models for a continuous naled contact of 2 hrs. Two dispersion models, AERMOD and AGDISP, were used to estimate potential ground-level exposure following an ultra-low volume naled application for adult mosquito control. The models were run under stable and high-wind conditions, as well as using 5-year meteorological conditions for the application season in Salt Lake City, Utah. Resulting exposure estimates were 2.5% for adults and 14.7% for children using the adjusted naled RfD at 0.01 mg/kg per day. Our findings support prior research suggesting very low potential exposures to naled under realistic field conditions. Thus, routine naled aerial applications applied in accordance with pesticide label parameters pose negligible human health risks when used for adult mosquito management. Keywords: Adulticide, AERMOD, AGDISP, DDPV, Mosquitoes, Naled, Organophosphates, Risk assessment, ULV, Vector management.