Non-targeted analysis reveals hundreds of per- and polyfluoroalkyl substances (PFAS) in UK freshwater in the vicinity of a fluorochemical plant

There are now over 7 million recognised per- and polyfluoroalkyl substances (PFAS), however the majority of routine monitoring programmes and policy decisions are based on just a handful of these. There is need for a shift towards gaining a better understanding of the total PFAS present in a sample rather than relying on targeted analysis alone. Total PFAS methods help us to understand if targeted methods are missing a mass of PFAS, but they do not identify which PFAS are missing. Non-targeted methods fill this knowledge gap by using high resolution mass spectrometry to identify the PFAS present in a sample. In this manuscript we use complimentary targeted and non-targeted analysis (NTA) to detect hundreds of PFAS in five freshwater samples obtained from the Northwest of the UK. Targeted analysis revealed PFOA at a maximum concentration of 12,100 ng L⁻¹, over three orders of magnitude greater than the proposed environmental quality standard (EQS) of 100 ng L⁻¹. A conservative assessment calculated an average total PFAS concentration of approximately 40 μg L⁻¹ across all samples. A suspect screening approach identified between 1175 (least conservative) to 89 (most conservative) PFAS at confidence level 4. Exploratory data analysis was used to identify 33 PFAS at confidence level 3 and 10 PFAS at a confidence level of 2. Only 8 of these 43 PFAS (representing 17% of the total PFAS peak area) are regularly monitored in the UK as part of the UK DWI 47 PFAS. Our results suggested the presence of a novel group of unsaturated perfluoroalkyl ether carboxylic acids (U-PFECAs) related to EEA-NH_4, a perfluoroalkyl ether carboxylic acid (PFECA), providing an example of the benefits of non-targeted screening. This study highlights the merits of non-targeted methods and demonstrates that future monitoring programmes and regulations would benefit from incorporating a non-targeted element.