Water-Quality Monitoring of Chemicals Used to Combat West Nile Virus

West Nile Virus, a mosquito-borne disease, was first detected in the United States in 1999 in New York City. Since then, air and ground spraying of insecticides and insecticide briquettes have been used throughout neighborhoods in the New York metropolitan area to reduce mosquito populations and thus the risk of human illness. This project was initiated to develop and test analytical methods to detect toxicologically relevant amounts of these insecticides. Ground-water and surface-water samples from the New York metropolitan area are analyzed for methoprene (an insect growth regulator), malathion (an organophosphate), two pyrethroid compounds (phenothrin and resmethrin), and piperonyl butoxide (a chemical synergist used with pyrethroids) using a newly developed gas chromatography / mass spectrometry (GC/MS) method. Methoprene acid, a methoprene degradate, was analyzed using immunoassay. More recently, passive in-situ samplers, semipermeable membrane devices (SPMDs), have been used to measure the bioavailability of these chemicals to fresh- and saltwater fish. All analyses have method reporting limits in the part-per-trillion range. These data are necessary for environmental risk assessment. The analytical methods used is this study are valuable for acquiring knowledge about the fate and transport of these mosquito insecticides and synergist in water.