Long term trends of legacy per- and polyfluoroalkyl substances (PFAS), their substitutes and precursors in archived wildlife samples from the German Environmental Specimen Bank

Systematic, up-to-date environmental monitoring data and temporal trends on PFAS are urgently needed to inform about their exposure from a rapidly changing PFAS market. The present study analysed long-term PFAS trends in three wildlife species in Germany: herring gull (Larus argentatus, eggs, 1988-2020) in a coastal food web, zebra mussel (Dreissena polymorpha, 1995-2018) as a filter feeder and common bream (Abramis brama, livers, 1996-2020) as a higher order consumer, the latter two in mainly benthic food webs. Retrospective trend analyses of 58 PFAS were carried out in about 60 archived samples of the German Environmental Specimen Bank (ESB) and complemented by the total oxidizable precursor (TOP) assay to quantify the formation potential from precursors of perfluorinated alkyl acids (PFAAs) over time. In all samples, concentrations of C8 PFAS decreased, above all perfluorooctanesulfonic acid (PFOS; by 4 µg kg^-1 per year) and its precursors. However, PFOS concentrations remained high in herring gull eggs (30 µg kg^-1) and bream livers (100 µg kg^-1) despite early restrictions. Concentrations of C10-C13 perfluorocarboxylic acids (PFCAs) increased in herring gull eggs until 2014 (∑=9.0 µg kg^-1) and C14 PFCA continued to rise until 2020 (0.65 µg kg^-1). In zebra mussels, the upwards trends of trifluoroacetic acid (TFA) and precursors of the short-chain C4-C7 PFCAs were even more pronounced - among them the 6:2 fluorotelomer sulfonamidopropyl betaine (6:2 FTSA-PrB). These results show that long-chain PFAS continue to accumulate in wildlife despite being restricted and that their substitutes, the (ultra)short-chain PFAS increase in concentration.