Aquatic Effects of Aerial Spraying for Mosquito Control over an Urban Area
Donald P. Weston; Erin L. Amweg; Abdou Mekebri; R. Scott Ogle; Michael J. Lydy
Abstract
In an effort to combat West Nile Virus, planes were used to disperse insecticide over the city of Sacramento, CA. Nearly 50,000 hectares were treated with pyrethrins and the synergist piperonyl butoxide
(PBO). Widespread dispersal of insecticide over a metropolitan area, coupled with extensive pre-treatment data on the area's urban creeks, provided a unique opportunity to study the effects of mosquito
control agents on aquatic habitats within an urban setting. There was no evidence of aquatic toxicity from the two active ingredients in the product applied. However, the PBO concentrations were high
enough to enhance the toxicity of pyrethroids already existing in creek sediments from general urban pesticide use. PBO concentrations of 2-4 µg/L were high enough to nearly double the toxicity of the
sediments to the amphipod Hyalella azteca. Though the increased toxicity was modest, it was unexpected to find environmental synergy at all. Risk assessments for mosquito control agents have focused on
the active ingredients, but have failed to recognize the potential for interactions with pesticides previously existing in the environment, which in this case appeared to represent a risk to aquatic life
greater than that of the active ingredients themselves.
Full article appeared in: Environmental Science and Technology (2005) 40:5817-5822.
Electronic reprint available free of charge at here.
