A 20-year study reveal decrease in per- and polyfluoroalkyl substances (PFAS) in a pelagic seabird from the Western...

Despite the first ban on perfluorooctane sulfonic acid (PFOS) in 2009, it remains unclear whether Europe, a key regulator, has effectively reduced per- and polyfluoroalkyl substances (PFAS) in the environment over the past 20 years. This study investigates the levels and temporal trends of 19 PFAS compounds in the livers of 62 Scopoli's shearwaters (Calonectris diomedea) collected from the Mediterranean basin during 2003-2022. Over the past two decades, PFAS concentrations showed an overall significant decrease of 77%. PFOS was the most frequently and predominantly detected chemical in livers, closely followed by perfluorotridecanoic acid (PFTrDA) and perfluoroundecanoic acid (PFUnDA). However, the contribution of PFTrDA (32.4%) surpassed that of PFOS (30.3%) in 2009-2014, which can be attributed to its increased use as a substitute following the regulation on PFOS in 2009. Perfluoroalkyl carboxylic acids (PFCAs), along with PFOS, showed a general decline over the study periods, with the largest decrease occurring after 2015, corresponding to the regulations on PFCAs. An odd-numbered, long-chain PFCAs accumulation trend was observed in samples. Principal component analysis showed a shift from PFOS to PFCAs in Scopoli's shearwater PFAS patterns over 20 years. Our results offer valuable insights into the environmental behavior of PFAS, the complex interactions between regulations and compounds and their transfer to the marine ecosystems. Despite widespread declines, their persistent detection underscores the need for enhanced international cooperation efforts to comprehensively mitigate PFAS emissions, including those from developing regions and unregulated sources.