Developing a trophic bioaccumulation model for PFOA and PFOS in a marine food web

Food web (or trophic) bioaccumulation models are useful tools for estimating the bioaccumulative tendencies of persistent organic pollutants, and are regularly used for regulatory assessment of industrial chemicals. Current models are mostly designed for neutral, lipophilic compounds, yet numerous compounds of concern are ionizable and/or proteinophilic, exhibiting unique bioaccumulation behaviour. In this study, an existing model was modified to evaluate bioaccumulation of two ionizable perfluoroalkyl acids (PFAAs) in a marine food web: perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). The model was tested against measured concentrations of PFOA and PFOS from a bottlenose dolphin food web in Charleston Harbor, SC. Both compounds were expected to bioaccumulate in this food web. Predicted concentrations of PFOS were in better agreement with empirical measurements compared to PFOA. This study supports the utilization of holistic measures of bioaccumulation (i.e., the trophic magnification factor, or TMF), particularly in food webs containing water- and air-respiring organisms.