title: Predicted transport of pyrethroid insecticides from an urban landscape to surface water.
abstract: The authors developed a simple screening-level model of exposure of aquatic species to pyrethroid insecticides for the lower American River watershed (California, USA). The model incorporated both empirically derived washoff functions based on existing, small-scale precipitation simulations and empirical data on pyrethroid insecticide use and watershed properties for Sacramento County, California, USA. The authors calibrated the model to in-stream monitoring data and used it to predict daily river pyrethroid concentration from 1995 through 2010. The model predicted a marked increase in pyrethroid toxic units starting in 2000, coincident with an observed watershed-wide increase in pyrethroid use. After 2000, approximately 70% of the predicted total toxic unit exposure in the watershed was associated with the pyrethroids bifenthrin and cyfluthrin. Pyrethroid applications for aboveground structural pest control on the basis of suspension concentrate categorized product formulations accounted for greater than 97% of the predicted total toxic unit exposure. Projected application of mitigation strategies, such as curtailment of structural perimeter band and barrier treatments as recently adopted by the California Department of Pesticide Regulation, reduced predicted total toxic unit exposure by 84%. The model also predicted that similar reductions in surface-water concentrations of pyrethroids could be achieved through a switch from suspension concentrate-categorized products to emulsifiable concentrate-categorized products without restrictions on current-use practice. Even with these mitigation actions, the predicted concentration of some pyrethroids would continue to exceed chronic aquatic life criteria.
authors.affiliation: Agricultural and Environmental Chemistry Graduate Group, University of California, Davis, California, USA.
authors.forename: Brant
authors.initials: B
authors.lastname: Jorgenson
authors.forename: Erica
authors.initials: E
authors.lastname: Fleishman
authors.forename: Kate H
authors.initials: KH
authors.lastname: Macneale
authors.forename: Daniel
authors.initials: D
authors.lastname: Schlenk
authors.forename: Nathaniel L
authors.initials: NL
authors.lastname: Scholz
authors.forename: Julann A
authors.initials: JA
authors.lastname: Spromberg
authors.forename: Inge
authors.initials: I
authors.lastname: Werner
authors.forename: Donald P
authors.initials: DP
authors.lastname: Weston
authors.forename: Qingfu
authors.initials: Q
authors.lastname: Xiao
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Young
authors.forename: Minghua
authors.initials: M
authors.lastname: Zhang
mesh_terms: D002140:California; D004784:Environmental Monitoring / Q000379:methods; D007306:Insecticides / Q000032:analysis* / Q000633:toxicity; D009570:Nitriles / Q000032:analysis / Q000633:toxicity; D011722:Pyrethrins / Q000032:analysis* / Q000633:toxicity; D045483:Rivers / Q000737:chemistry; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000633:toxicity
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; D014874:Water Pollutants, Chemical; C099952:bifenthrin; C052570:cyfluthrin
keywords: Environmental fate; Environmental modeling; Pesticide runoff; Pyrethroids