Elucidating the fate of perfluorooctanoate sulfonate using a rainbow trout (Oncorhynchus mykiss) physiologically-based toxicokinetic model

• Published in: The Science of the total environment Vol. 691; pp. 1297 - 1309
• Main Authors: Vidal, Alice, Babut, Marc, Garric, Jeanne, Beaudouin, Rémy
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.11.2019; Elsevier
• Subjects: Elimination route contribution; Environmental Sciences; Perfluorooctanoate sulfonate; Physiological multicompartment model; Rainbow trout; Simultaneous uptake pathway; Simultaneous uptake pathway; Elimination route contribution; Physiological multicompartment model; Perfluorooctanoate sulfonate; Rainbow trout; SIMULTANEOUS UPTAKE PATHWAY; ELIMINATION ROUTE CONTRIBUTION; PHYSIOLOGICAL MULTICOMPARTMENT MODEL; RAINBOW TROUT; PERFLUOROOCTANOATE SULFONATE
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.07.105

Per- and poly-fluorinated substances (PFAS) are widely found in freshwater ecosystems because of their resistance to degradation. Among them, several long-chain perfluoroalkyl acids bioaccumulate in aquatic vertebrates, but our understanding of the mechanisms of absorption, distribution and elimination is still limited in fish. For this purpose, we developed a 10-compartment physiologically-based toxicokinetic (PBTK) model to elucidate perfluorooctane sulfonate (PFOS) kinetics in adult rainbow trout. This PBTK model included various physiological characteristics: blood perfusion to each organ, plasmatic fraction, PFOS free fraction, and growth of individuals. The parameters were optimized using Bayesian inferences. First, only PFOS absorption by diet was considered in the model as well as its elimination by urine, bile and feces. Then two mechanistic hypotheses, assumed to govern PFOS toxicokinetics in fish, namely the enterohepatic cycle and the absorption and elimination though gills, were tested. Improvement of the model's fit to the data was studied in each organ by comparing predictions with observed data using relative error. The experimental data set was obtained from an exposure experiment, where adult rainbow trout were fed with a PFOS-spiked diet for 42 days, followed by a 35-day depuration period. In all cases, PFOS concentrations were accurately predicted in organs and feces by the model. The results of this PBTK model demonstrated that feces represented the major elimination route for PFOS while urine was a minor route. Also, PFOS branchial uptake can be substantial despite low concentrations of the compound in water, and elimination through gills should not be neglected. Finally, the enterohepatic cycle is likely to play a minor role in PFOS toxicokinetics. Overall, this PBTK model accurately described PFOS distribution in rainbow trout and provides information on the relative contribution of absorption and elimination pathways. [Display omitted] •A PBTK model describing PFOS kinetics was calibrated for simultaneous uptake pathways.•Fish growth was modeled to correct PFOS dilution in organs.•PFOS was more eliminated by feces while urine was a minor excretion route.•Gill absorption and excretion cannot be neglected.•The enterohepatic cycle was not supported by model outputs.