PFAS in Drinking Water: Technical Analysis of a New Regulatory Era for Water Utilities

Since 12 January 2026, the European Union has reached a major milestone in the protection of public health and water resources. The transition period provided for under Directive (EU) 2020/2184 (recast Drinking Water Directive) has now ended. From now on, the systematic and harmonised monitoring of per- and polyfluoroalkyl substances (PFAS) is a legal obligation for all Member States. 

1. A dual-threshold regulatory framework 

The Directive now requires compliance with two distinct limit values, reflecting complementary monitoring objectives: 

→ “Sum of PFAS” (0.10 μg/L) 

This parameter specifically targets 20 individual substances considered of concern. Listed in Annex III of the Directive, they include 10 perfluoroalkyl carboxylic acids (PFCAs) and 10 perfluoroalkyl sulfonic acids (PFSAs), with carbon chain lengths ranging from 4 to 13 atoms. The limit value is set at 100 ng/L for the sum of these compounds. 

→ “PFAS Total” (0.50 μg/L) 

This parameter takes a much broader approach by covering all per- and polyfluoroalkyl substances. The limit value is set at 500 ng/L. The objective is to capture the total organofluorine load, including thousands of molecules not covered by the “Sum of PFAS”. 

In accordance with Article 13(7) of the Directive, and following consultations with Member States, technical guidelines (C/2024/4910) have been published to define the analytical methods applicable to these two parameters. 

2. Analytical control: requirements for the “Sum of PFAS” 

The assessment of compounds under the “Sum of PFAS” relies on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The EN 17892:2024 standard, used as the reference analytical method, recommends two methodological approaches: 

• Part A (Direct injection): a rapid method in which unfiltered drinking water samples are injected directly into the LC-MS system. 

• Part B (SPE enrichment): this method involves solid-phase extraction (SPE) to concentrate the sample, providing higher sensitivity and lower quantification limits. 

3. The technical challenge of “PFAS Total” 

The comprehensive measurement of PFAS represents a major scientific challenge, as no single method can quantify all compounds in this chemically diverse group. Three approximation methods are currently validated by the Commission: 

1. TOP assay (Total Oxidizable Precursors)  

This method uses chemical oxidation to convert PFAS precursors into measurable perfluorocarboxylic acids. However, it may lead to underestimation, as some compounds (notably perfluorinated ethers) are not fully oxidised. 

2. EOF-CIC (Extractable Organic Fluorine)  

This method measures extractable organic fluorine via combustion and ion chromatography. The result, expressed in ng/L of fluorine, is converted into PFOA-equivalent using a conversion factor of 1.45 (thus, 345 ng/L F corresponds to 500 ng/L PFAS Total). 

3. LC-HRMS (High-resolution mass spectrometry)  

This non-targeted approach enables the detection of a much broader range of compounds. However, it remains semi-quantitative and requires a high level of expertise to interpret signals and minimise false positives. 

4. The critical case of trifluoroacetic acid (TFA) 

TFA is an ultra-short-chain PFAS (2 carbon atoms), characterised by high mobility, persistence, and strong hydrophilicity. It enters the water cycle through the degradation of pesticides, refrigerants, or industrial discharges. In many Member States, concentrations measured in untreated water frequently exceed the 0.50 μg/L threshold, thereby surpassing the parametric value for “PFAS Total”. 

To address this issue, the Commission requires a four-step reporting protocol: 

1. Measure [PFAS Total] using an approximation method. 

2. Measure [TFA] specifically using a targeted analytical method compliant with the Directive. 

3. Report three values: [PFAS Total], [TFA], and the difference [PFAS Total] – [TFA]. 

4. If the result is negative, the measurement is considered inconclusive. 

5. Performance criteria 

To ensure measurement reliability, the Directive establishes several analytical requirements at the point of compliance: 

• Limits of quantification (LOQ)  

The overall LOQ must be ≤ 30% of the parametric value, i.e. 30 ng/L for Sum of PFAS. However, the Commission recommends an individual LOQ of ≤ 1.5 ng/L for each of the 20 substances. For “PFAS Total”, the LOQ must be ≤ 150 ng/L. 

For the most toxic compounds identified by EFSA (PFHxS, PFOA, PFOS, PFNA), even lower target limits are recommended. 

• Measurement uncertainty  

The Directive sets a maximum expanded uncertainty of 50% at the parametric value level. In practice, European laboratories generally achieve better performance, with uncertainties ranging from 18% to 39% depending on the method used. 

• Validation of measurements  

At ultra-trace levels (ng/L), environmental and laboratory conditions become limiting factors. Member States must ensure that analytical methods used for monitoring and compliance demonstration are validated in accordance with EN ISO/IEC 17025 or an equivalent internationally recognised standard. 

• Current limitations  

Unlike the “Sum of PFAS”, methods for measuring “PFAS Total” are not yet fully harmonised at the European level. Available data on measurement uncertainty and LOQ remain limited, making it difficult to fully assess compliance with regulatory performance criteria for this global parameter. 

6. Immediate actions in case of exceedance 

The entry into force of these requirements means that any non-compliance must trigger immediate corrective actions to protect public health. 

Water managers, under the supervision of national authorities, must: 

• Inform the public transparently about risks and precautionary measures. 

• Shut down wells or abstraction points where PFAS levels are excessive. 

• Implement specific treatment processes (activated carbon, ion exchange resins, or reverse osmosis) to remove contaminants. 

• Restrict water use if necessary until compliance is restored. 

Conclusion 

The implementation of these provisions is part of the “Zero Pollution” Action Plan. The new reporting framework now requires systematic transmission of data on exceedances and incidents to the Commission. 

Beyond tap-level compliance, a comprehensive approach is required, including risk assessment from the abstraction area onwards. Anticipating pollution sources, combined with mastering complex analytical protocols (particularly for PFAS Total and TFA), is essential for ensuring sustainable and secure water resource management. 

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Authors: Floriane DEMAILLY & Loris MISTRULLI

References: 

• Directive (EU) 2020/2184: Directive (EU) 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the quality of water intended for human consumption (recast), OJ L 435, 23.12.2020, pp. 1–62. Available on : http://data.europa.eu/eli/dir/2020/2184/oj (accessed on 24/02/2026). 

• Commission Notice C/2024/4910: Technical guidelines regarding methods of analysis for monitoring of per- and polyfluoroalkyl substances (PFAS) in water intended for human consumption, OJ C, C/2024/4910. Available on : http://data.europa.eu/eli/C/2024/4910/oj (accessed on 24/02/2026).