Ultra-Short-Chain PFASs in the Sources of German Drinking Water: Prevalent, Overlooked, Difficult to Remove, and Unregulated

Per- and polyfluoroalkyl substances (PFASs) havebeen a focal point of environmental chemistry and chemicalregulation in recent years, culminating in a shift from individualPFAS regulation toward a PFAS group regulatory approach inEurope. PFASs are a highly diverse group of substances, andknowledge about this group is still scarce beyond the well-studied,legacy long-chain, and short-chain perfluorocarboxylates (PFCAs)and perfluorosulfonates (PFSAs). Herein, quantitative and semi-quantitative data for 43 legacy short-chain and ultra-short-chainPFASs (<= 2 perfluorocarbon atoms for PFCAs,<= 3 for PFSAs andother PFASs) in 46 water samples collected from 13 differentsources of German drinking water are presented. The PFASsconsidered include novel compounds like hexafluoroisopropanol,bis(trifluoromethylsulfonyl)imide, and tris(pentafluoroethyl)trifluorophosphate. The ultra-short-chain PFASs trifluoroacetate,perfluoropropanoate, and trifluoromethanesulfonate were ubiquitous and present at the highest concentrations (98% of sumtarget PFAS concentrations)."PFAS total"parameters like the adsorbable organicfluorine (AOF) and total oxidizable precursor(TOP) assay were found to provide only an incomplete picture of PFAS contamination in these water samples by not capturingthese highly prevalent ultra-short-chain PFASs. These ultra-short-chain PFASs represent a major challenge for drinking waterproduction and show that regulation in the form of preventive measures is required to manage them.