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

Abstract

Per- and polyfluoroalkyl substances (PFASs) have been a focal point of environmental chemistry and chemical regulation in recent years, culminating in a shift from individual PFAS regulation toward a PFAS group regulatory approach in Europe. PFASs are a highly diverse group of substances, and knowledge about this group is still scarce beyond the well-studied, legacy long-chain, and short-chain perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs). Herein, quantitative and semiquantitative data for 43 legacy short-chain and ultra-short-chain PFASs (≤2 perfluorocarbon atoms for PFCAs, ≤3 for PFSAs and other PFASs) in 46 water samples collected from 13 different sources of German drinking water are presented. The PFASs considered 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 sum target PFAS concentrations). “PFAS total” parameters like the adsorbable organic fluorine (AOF) and total oxidizable precursor (TOP) assay were found to provide only an incomplete picture of PFAS contamination in these water samples by not capturing these highly prevalent ultra-short-chain PFASs. These ultra-short-chain PFASs represent a major challenge for drinking water production and show that regulation in the form of preventive measures is required to manage them.

Occurrence, Distribution, and Environmental Behavior of Persistent, Mobile, and Toxic (PMT) and Very Persistent and Very Mobile (vPvM) Substances in the Sources of German Drinking Water

“…In three groundwater samples, none of the PMT/vPvM substances were detected. In a parallel study focusing on PFAS, two of these three samples also showed the lowest PFAS concentrations of the sample set …”

“…Substances for analysis were then prioritized based on current data and analytical reference standard availability. Per- and polyfluoroalkyl substances (PFAS) from these lists were not included, as they are presented in a parallel study . Second, compounds that were deemed not feasible to measure using the selected HILIC-MS/MS, RPLC-MS/MS, and GC-MS/MS methods, or because reference standards were not available, were also excluded.…”

Future regulation for the reduction of PFAS pollution in aquifers and for the improvement of drinking water quality

“…Sulla scorta delle risultanze conseguite nel corso di un'altra recente ricerca, svolta in Germania (Neuwald et al 2022) presso 13 differenti siti di produzione acquedottistica, si è concluso che la vera sfida futura riguarda le PFAS a catena ultracorta. Questi composti, caratterizzati da un numero di atomi di perfluorocarburo variabile da 2 a 3, paiono essere onnipresenti nei serbatoi sotterranei di acqua destinata all'uso umano e con concentrazioni molto elevate, pari al 98% della somma delle PFAS tradizionali come PFOA, PFOS e PFBA.…”

PhotoTOP: PFAS Precursor Characterization by UV/TiO2 Photocatalysis

“…Besides high-resolution mass spectrometry (HRMS), which considerably helped to increase knowledge about distinct identities of numerous new PFAS, − there are also sum-parameter approaches that are necessary due to the fact that many PFAS are not readily ionizable or extractable from their matrix . While parameters such as total fluorine (TF) and absorbable and extractable organic fluorine (AOF, EOF) , have their individual advantages they also go along with the loss of information on identity of individual PFAS, their properties, fate, and toxicity (e.g., chain length, bioaccumulation) …”