T9 PM Pyrethroid Insecticides in Urban and Agricultural Environments
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 339-340

(LYD-1117-740135) Relative contributions of agricultural or urban pyrethroid usage to toxicity in California streams.

Lydy, M¹, Weston, D², You, J¹, ¹ Southern Illinois University, Carbondale, IL, USA² University of California-Berkeley, Berkeley, CA, USA

ABSTRACT- Due to the increasing regulatory restrictions on organophosphate pesticides, pyrethroid pesticides have replaced the organophosphates for many residential and agricultural uses. Urban use of pyrethroids, in particular, has increased significantly due to professional pest control and retail sales for home usage. This study was designed to compare and contrast agricultural and urban usage of pyrethroids and the resulting toxicity noted in these two landscapes. About 150 agricultural sediment samples and 50 urban samples were taken from water bodies throughout California. These sediments were analyzed for 28 pesticides including chlorpyrifos, 20 organochlorine insecticides, and the following pyrethroids: bifenthrin, lambda-cyhalothrin, deltamethrin, esfenvalerate, permethrin, cyfluthrin and cypermethrin. Acute toxicity tests (10-day) with Hyalella azetca were also conducted on all samples. Nearly 80% of the agricultural sediments contained measurable pyrethroid concentrations, while 100% of the urban samples contained pyrethroids. Of these samples, 70% of the urban sites were acutely toxic to H. azetca, and 20% of the agricultural sites were toxic. Using a toxic unit approach, it was found that pyrethroids were likely the sole or major contributor to much of the toxicity in both landscapes. In addition, all of the tested pyrethroids had higher median and maximum concentrations in urban versus agricultural sites. The relative composition of the pyrethroids differed, however, with esfenvalerate often detected in the agricultural setting, while bifenthrin and cyfluthrin dominated the urban samples. The data show that agricultural use of pyrethroids may be causing more widespread toxicity to aquatic invertebrates simply because of the greater amount of land devoted to agriculture in the study area, but the magnitude of pyrethroid concentrations and severity of toxicity is often greater in urban environments.

Key words: pyrethroid insecticides, toxicity, sediments, urban