"In this instance, it appeared the biggest concern was not the aquatic toxicity of the pyrethrin insecticide in the mosquito spray, but the fact that the non-toxic synergist actually synergized the 'wrong' thing - pyrethroid pesticides that were already in the creek sediments," said Weston.
"This is the first field study to show an interaction of PBO with something in the environment, so even a two-fold increase is a pretty major finding," added study co-author Michael Lydy, associate professor of zoology at Southern Illinois University.
Other co-authors of the study are Erin Amweg, a UC Berkeley post-doctoral researcher in integrative biology; Abdou Mekebri, a chemist at the California Department of Fish and Game; and R. Scott Ogle, a toxicologist at Pacific EcoRisk.
Pyrethroids have risen to dominance as organophosphate pesticides, including diazinon and chlorpyrifos, are phased out due to concerns over their effects on the human nervous system. (Organophosphates have been largely eliminated from residential use, but are still widely used on agricultural crops.) There are more than 1,200 pyrethroid-containing products on the market in California, ranging from cans of household bug killer to commercial pest control sprays.
Prior studies by Weston and colleagues have shown that pyrethroids exist in agricultural and urban streams at levels toxic to sensitive aquatic life. General urban pesticide use, such as applying insecticides on lawns, gardens and around the perimeter of homes, is likely responsible for the bulk of the pyrethroids found in the sediment of urban streams, the researchers said.
Based in part upon these prior findings, the California Department of Pesticide Regulation (DPR) announced earlier this month that it will begin re-evaluating some 600 pyrethroid-containing products. The re-evaluation process will likely help determine what urban pesticide use practic
Source:University of California - Berkeley