The Lake Washington PCB/PBDE Study: Modeling Bioaccumulation of PCBs in Lake Washington Fish

High polychlorinated biphenyl (PCB) concentrations in Lake Washington fish prompted the Washington Department of Health to issue a fish consumption advisory in 2004. To address PCB bioaccumulation in Lake Washington fish, King County was awarded a Puget Sound Action Agenda: Technical Investigations and Implementation Assistance Grant by the U.S. Environmental Protection Agency. An investigation of PCB loadings to Lake Washington was complemented by the development of 1) a contaminant fate model and 2) a bioaccumulation model to predict tissue PCB concentrations in Lake Washington fish. This presentation will describe the bioaccumulation model - a Gobas-type food web model adapted to Lake Washington. The model predicts whole-tissue contaminant concentrations in food web components (e.g., phytoplankton, zooplankton, benthic invertebrates, and fish) by calculating chemical uptake from ingestion and respiration as well as elimination from respiration, excretion, metabolism and growth dilution. The required model inputs include the food web structure of Lake Washington for the taxa of interest as well as physical and chemical parameters (e.g., biota lipid content, concentration of suspended solids, organism wet weight). The model was run using both water and sediment PCB concentrations derived from empirical data and those predicted by the fate model. To test the model performance, model predictions were compared to observed PCB concentrations in Lake Washington biota. Overall, the model performed best using water and sediment concentrations predicted by the fate model; almost all predicted PCB concentrations fell within a factor of two of average observed concentrations in Lake Washington biota. This model was used to estimate the magnitude of reductions in water and sediment PCB concentrations necessary to bring PCBs in Lake Washington fish to safe levels