Perfluorooctanesulfonate (PFOS) exposure in ringed seals (Pusa saimensis) in Lake Saimaa, Finland.

Perfluorooctanesulfonate (PFOS) is common in the environment, highly accumulative, toxic, and thus a good indicator for per- and polyfluorinated alkyl acid (PFAS) contamination. In this study, PFOS was analysed from the tissues of Saimaa ringed seal (Pusa saimensis) pups and adults to investigate the exposure to PFAS in Lake Saimaa. Additionally, a toxicity evaluation was performed for the seals based on the thresholds from the literature, PFOS concentration data from the national exposure database, and the current study. For all studied specimens, the highest PFOS concentrations were found in the liver, but interestingly, high concentrations were also observed in the kidneys of lanugo pups. The toxicity evaluation indicated that the PFOS concentrations in the prey fish are so high that the tolerable daily and weekly intake values from literature as well as the environmental quality standards calculated in this study were exceeded. Furthermore, a mixture of PFAS has been observed in the fish of Lake Saimaa, which means that these seals are exposed to multitudes of PFAS. This mixture of PFAS may be more harmful than PFOS alone and together with PFOS toxicity evaluation results, despite the confounding factors of the assessment, this raises concern that PFAS contamination in Lake Saimaa may cause detrimental effects in Saimaa ringed seals.