Evaluating and applying sediment bioaccumulation models: A Great Lakes case study

Several models exist for predicting the uptake of hydrophobic, non-polar organic contaminants (e.g., dioxins, furans and PCBs) into biota from sediments. In order to promote the best science possible and to provide a consistent, scientifically-sound foundation for risk management decisions, Region 5 developed a guidance document that includes the following: (1) evaluation of various models available for predicting bioaccumulation (e.g., BCF, BAF, TBP and BSAF); (2) determination of data needs of the models; (3) preferred approaches for applying the models; (4) model validation using data from Great Lakes sediment sites; and (5) application of the BSAF model at a fictitious site. The draft Region 5 guidance is currently undergoing outside review. The guidance has been utilized, and an actual Great Lakes example will be presented. In this case study, the BSAF model was used in conjunction with risk assessment methodology to generate cleanup goals and assess risks under different remedial alternatives. Critical concepts in using the BSAF model that will be discussed include the following: fish species differences, modeling sediment concentrations to which the fish are exposed to, and using BSAF factors that take into account food chain effects.