PFAS in first-time mothers from Sweden: temporal trends and the impact from fish/seafood consumption and drinking water exposure

Per- and polyfluoroalkyl substance (PFAS)-contaminated drinking water has been a significant source of human exposure to PFAS in Uppsala, Sweden. Herein, we investigated temporal trends of PFAS in serum samples collected three weeks after delivery from first-time mothers in Uppsala (1996-2022; n = 869), to determine whether efforts to remediate drinking water contamination have reduced maternal PFAS exposure. In addition, the impact of fish/seafood consumption as an exposure source was evaluated. PFAS were analysed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and temporal trends were evaluated using adjusted cubic spline models. Linear (lin) and branched (br) perfluorooctane sulfonate (PFOS) and perfluoroctanoate (PFOA) showed declining temporal trends, likely due to international regulation and phase-out initiatives. Later initiatives to restrict use and emissions of perfluorononanoate (PFNA), perfluorodecanoate (PFDA) and perfluoroundecanoate (PFUnDA) likely explained the initial increased concentrations by 3-7% per year, up to 2007 or 2010, followed by decreasing trends, on average 2-3% per year. Drinking water contamination was likely responsible for the increase in serum br and lin perfluorohexanesulfonate (PFHxS) concentrations early in the study period, followed by a decline over the last decade associated with remediation of the drinking water contamination around 2012. However, even after remediation, drinking water appeared to contribute to perfluoropentanesulfonate (PFPeS) and PFHxS. Fish/seafood consumption was significantly associated with serum levels of lin PFOS, PFNA, PFDA, and PFUnDA. Overall, PFAS exposure among first-time mothers in Uppsala has declined, resulting in a marked reduction in the proportion of mothers exceeding the serum reference value established by the European Food Safety Authority. Nevertheless, 54% of the mothers sampled from 2018 to 2022 still exceeded this level, showing that efforts to reduce PFAS exposure must continue for many years to come.