Occurrence of Pyrethroids in Bed and Suspended Sediments in California

Pyrethroids have been detected in sediments collected over the past decade from a variety of California locations. While most published studies sampled in close proximity to pyrethroid application, the studies included in this chapter focused on watersheds located farther from pyrethroid sources. The four watersheds in this chapter varied considerably in size (1-100,000 km 2 ) and included both agricultural and urban land use. Four pyrethroids (bifenthrin, λ-cyhalothrin, τ-fluvalinate and permethrin) were detected in bed and suspended sediments. Bifenthrin and permethrin were detected the most frequently and at the highest concentrations, with maximum concentrations of 24 and 70 ng/g dry weight, respectively. Occurrences of individual pyrethroids were correlated to higher use in some but not all cases.