Exposure and magnification of PFAS in a temperate estuarine food web, including top predators

The Western Scheldt is a polluted temperate estuary in the Netherlands and a hotspot for per- and polyfluoroalkyl substances (PFAS), leading to environmental concerns. To assess PFAS contamination, several biota types were sampled in 2023. Reference data was available from 2006 to 2008 and reference material was collected from the Wadden Sea. A spatial gradient in stable isotopes and PFAS concentrations was observed in the estuary. PFAS concentrations were positively correlated with trophic level. For most biota, concentrations were significantly lower than 2006-2008, but significantly higher than the Wadden Sea. Whole-body burdens for marine mammals were extrapolated from liver concentrations to allow further comparison between trophic levels. Biota Magnification Factors for perfluorooctane sulfonic acid (PFOS) ranged between 0.1 and 34, and the Trophic Magnification Factor was 5.7. PFOS concentrations exceeded the European threshold level in flounder and, partly, other fish. Results point at risk of sublethal effects in estuarine biota at several trophic levels.