PFAS in the EU Drinking Water Directive: A critical view on the analytical and regulatory challenges associated with high TFA concentrations

www.tzw.de PFAS in the EU Drinking Water Directive Frank Thomas Lange PFAS Global 2025 virtual conference April 24, 2025 A critical view on the analytical and regulatory challenges associated with high TFA concentrations PFAS parameters in Directive (EU) 2020/2184 PFAS PFAS Total 0.50 µg/l Sum of PFAS 0.10 µg/l limit of quantification: ≤ 30 % of parametric value uncertainty of measurement: ≤ 50 % Article 13, paragraph 7 By 12 January 2024, the Commission shall establish technical guidelines regarding methods of analysis for monitoring of perand polyfluoroalkyl substances under the parameters ‘PFAS Total’ and ‘Sum of PFAS’, including detection limits, parametric values and frequency of sampling. 20 C4-C13 PFAAs LC-MS/MS analysis according to EN 17892 Where to measure PFAS Total? PFC Vorläufersubstanz en Source: precursors Sink: terminal degradation products e.g. fluorosurfactants in AFFF groundwater degradation processes transport of degradation products PFCAs, PFSAs, some additional PFAS e.g. fluorochemicals in paper-fiber biosolids drinking water Support for the EU Commission, DG ENV Consortium Service contract No. 090202/2023/890359/SER/ENV.C.2 Directive (EU) 2020/2184 –PFAS Total Parameter Parametric value Unit Notes PFAS Total 0.50 µg/l ‘PFAS Total’ means the totality of per -and polyfluoroalkyl substances. This parametric value shall only apply once technical guidelines for monitoring this parameter are developed in accordance with Article 13(7). Member States may then decide to use either one or both of the parameters ‘PFAS Total’ or ‘Sum of PFAS’. There is no exact definition of the key term “PFAS”. ! How many PFAS need to be analyzed? OECD (2021): All compounds with a −CF2− or −CF3group are PFAS (few exceptions) 6.5 million entries for PFAS in Pubchem1) 5.7 M with isolated CF3groups 0.67 M with isolated CF2groups 0.23 M with groups > CF2/CF3 Estimated <1% measurable by quantitative target analyses FlufenacetFluoxetin PFOA 6:2 FTAB HPFO-DA (GenX) Trifluoroacetate (TFA) Entrance pathways of TFA into the environment TFA (bio-)degradation of pesticide active ingredients → e.g. flufenacet manure (bio-)degradation of pharmaceuticals → e.g. sitagliptin urine industrial emissions primary source secondar y source photolysis of blowing agents & refrigerants (e.g. air conditioning) and atmospheric deposition Increasing TFA concentrations in groundwater Albers, C.N. & Sultenfuss, J., Environ. Sci. Technol. Lett. 2024, 11, 10, 1090–1095 Technical guidelines: PFAS Total proxies for PFAS Total, „tentatively acceptable“: TOP assay (targeted method) EOF (non-specific method) LC-HRMS (suspect target/ non-targeted method) „big points“ (max. 20 out of 100 points each) number of assessed PFAS/PFAS groups selectivity (risk for false positives/negatives) sensitivity (LOQ) uncertainty of measurement EOF: Principle of sample preparation EOF Y. Miyake et al. (2007) Adsorption weak anion exchanger Clean-up for F-removal 0.01% NH4OH in MeOH Elution e.g. with MeOH, 0.1% NH4OH in MeOH Combustion-Ion Chromatography (CIC) Utility of EOF-CIC for PFAS Total analysis •EOF has a low selectivity, i.e. broad analytical window: positive from the viewpoint of precautionary principle •However, it also discriminates substances during sample preparation, e.g. ultrashort-chain PFAS, such as TFA. •For EOF it is still unknown, how many drinking waters would exceed the parametric value of 0.5 µg/L. •For testing compliance with parametric value (0.5 µg/L) an additional convention is needed: PFOA-equivalents (345 ng/L F ≙500 ng/L PFOA) •Result: [PFAS TotalEOF-CIC PFOAeq] Utility of suspect target screening / NT analysis by LC-HRMS for PFAS Total analysis •PFAS are analyzed without prior transformation. •Broad analytical window, determined by sample preparation and the availability of suspect lists •Only ionizable PFAS can be detected. •Confirmation of compound identity depends on confidence levels. •No LC-HRMS standard method available for PFAS in drinking water. •Result dependent on the individual workflow •Semi-quantitative: critical for compliance testing •Result: [PFAS TotalHRMS] TFA concentration dominates PFAS Total Median (all samples) 0.25 µg/L Scheurer & Nödler (2021), Food Chemistry 351, 129304 Parametric value of the EU-DWD: 0.5 µg/L Global 2000: TFA: The forever chemical in drinking water (TFA: Die Ewigkeits-Chemikalie im Trinkwasser) (2024) How to take TFA into account? Recommendation of the Commission for reporting analytical results of PFAS Total Determine PFAS Total Determine TFA Calculate difference Check if difference < 0 How to take TFA into account? Small difference of comparable large numbers → inaccurate result! [PFAS Total]-[TFA] Ship: [TFA] [PFAS Tota] Conclusions •There is no appropriate method for compliance testing with the parametric value for PFAS Total in the DWD –only proxy methods. •Proxy methods for PFAS Total are considered rather supplementary screening tools in addition to Sum of PFAS. •High TFA concentration hamper the PFAS Total concept. •Sufficiently sensitive proxy methods should be further developed, harmonized and standardized (optimization for exclusion of TFA). •TFA should be measured and regulated separately. •Vision: Semi-quantitation by LC-HRMS (after standardization) should be considered in regulation for compliance testing? •Greater uncertainties of measurement need to be accepted (e.g. factor of 2-5) •Better to have semi-quantitative data than no data! Acknowledgements LUBW: TOP assay study (2021-2022) BMBF project PFClean (2023-2026) EU project ZeroPM (2021-2026) and …to all former and present involved colleagues at TZW Contact Dr. Frank Thomas Lange Department Water Chemistry / Section Water Chemistry Research Tel.: +49 721 9678-157 [email protected]