Emerging PFAS in songbird eggs from a Belgian hotspot site

The Flanders region (Belgium) has several per- and polyfluoroalkyl substances (PFAS) hotspots due to industrial activities, including a fluorochemical plant (FCP) near Antwerp. Previous studies in this area reported exceptionally high levels of legacy PFAS in soils, invertebrates and birds using targeted liquid chromatography-mass spectrometry (LC-MS/MS) methods. In this study, bird eggs were used as biomonitoring tools to comprehensively investigate PFAS bioaccumulation near the hotspot through suspect and non-target high-resolution mass spectrometry (HRMS) screening. A total of 40 eggs (26 Great tit Parus major, 14 Blue tit Cyanistes caeruleus) were collected from three sites near the FCP during the 2022 breeding season. Suspect screening was based on two PFAS lists covering over 10,000 compounds, and non-targeted analysis using the FluoroMatch software. In addition to target PFAS, 62 compounds spanning 16 classes were identified and assigned Confidence Levels 2 or 3. Semi-quantification revealed notably high levels of emerging PFAS, particularly homologues of ether-substituted perfluoroalkyl sulfonic acids (PFESAs) and pentafluorosulfide perfluoroalkyl sulfonic acids (SF₅-PFSAs), including the first detection of SF₅-PFSA C6 in biota. Quantification and semi-quantification showed the highest levels of some PFAS ever measured in bird eggs, with compounds identified by HRMS contributing up to 15 % of the total PFAS burden. This is the first study to report such a broad and highly concentrated profile of emerging, largely non-oxidizable PFAS in bird eggs, underscoring the importance of suspect and non-targeted analysis. These rarely monitored PFAS should be considered for inclusion in both human and environmental monitoring programmes and risk assessments.