In the recast 2020 EU Drinking Water Directive and the German Drinking Water Ordinance (Trinkwasserverordnung) from 2023, parametric values for per- and polyfluoroalkyl substances (PFAS) have been set for the first time. These non-natural, industrially produced chemicals are released into the environment via a large number of products and processes. The detection and monitoring of compounds that are currently difficult or impossible to analyze poses new challenges for water analysis.
The EU Directive 2020/2184 of the European Parliament and of the Council of December 16, 2020 on the quality of water intended for human consumption was published on December 23, 2020 and transposed into national law with the German Drinking Water Ordinance (TrinkwV), which came into force on June 24, 2023. The revised Directive 2020/2184 also includes per- and polyfluoroalkyl substances (PFAS) with two new parametric values for the first time.
What are PFAS?
PFAS are synthetic, industrially produced chemicals. They have water, grease and dirt-repellent properties and have been used since the 1950s, for example in galvanic baths, fire extinguishing foams, non-stick coated cookware, outdoor clothing and food packaging. Due to the persistence of perfluorinated compounds, which are often formed in the environment as final degradation products of polyfluorinated precursors, coupled with the mobility of short-chain PFAS and the bioaccumulation potential of long-chain PFAS in the human body, their production and use are to be largely restricted in the EU in future.
PFAS in the EU Drinking Water Directive
Annex I of the new directive provides for a parametric value (Sum of PFAS) of 0.1 µg/L for the sum of the concentrations of a selection of 20 perfluoroalkyl acids (PFAAs) listed in Annex III. These 20 target compounds thus represent only a very small subset of all known PFAS. PFAAs containing a perfluoroalkyl unit with three or more (maximum 13) carbon atoms are thus regulated. This approach does not differentiate between the different toxicities of PFAAs with different alkyl chain lengths. If a PFAA contamination is present in drinking water, this may lead to a more stringent assessment in the future, especially if a high proportion of short-chain PFAAs of low toxicity is present. In addition, the sum parameter PFAS Total was introduced with a parametric value of 0.5 µg/L for the sum of all PFAS. However, no definition of the term PFAS can be found anywhere in the EU Directive.
Technical guidelines are now available: Methods for monitoring Sum of PFAS and PFAS Total
The new parameters should only be applied once technical rules for monitoring this parameter have been developed. These technical rules were originally supposed to be available by January 12, 2024, but were actually published on August 7, 2024 with the Commission Notice C/2024/4910 “Technical guidance on analytical methods for the monitoring of per- and polyfluorinated alkyl substances (PFAS) in water intended for human consumption”.
Scientists from the Water Chemistry Research Section at TZW were part of an international consortium consisting of the IWW, the University of Örebro/Sweden, and the University of Copenhagen/Denmark. In a consultancy project for the EU Commission, the consortium compared numerous existing analytical methods (target/non-target analysis, sum parameters) with regard to their suitability for determining Sum of PFAS and PFAS Total. The results were incorporated into a draft of these technical rules. As the technical rules are now available, the Member States can decide whether to apply either one of the parameters Sum of PFAS or PFAS Total or both. In Germany, only the parameter Sum of PFAS (under the name Summe PFAS-20) with a limit value of 0.1 µg/L (valid from January 12, 2026) is implemented in the new Drinking Water Ordinance. In addition, Germany introduced the additional parameter Summe PFAS-4 with a limit value of 0.02 µg/L or 20 ng/L (valid from January 12, 2028) for the sum of the concentrations of the four PFAS PFOA, PFNA, PFHxS and PFOS. This parameter was derived taking into account the Tolerable Weakly Intake (TWI) of 4.4 nanograms per kilogram of body weight set by the European Food Safety Authority (EFSA) in 2020.
Sum of PFAS can now be analytically monitored
The 20 individual compounds listed for the Sum of PFAS parameter cover a wide range of PFAAs with chain lengths from C4 to C13. At the time of publication of Directive 2020/2184, no analytical standards were available for two of the long-chain sulfonic acids, which are mandatory for quantitative analysis. Furthermore, isotopically-labelled standards, which are necessary for precise concentration determination in HPLC-MS/MS analysis in order to mathematically correct matrix effects and losses during sample preparation, were missing for individual PFAS in Annex III. These gaps have now been partially closed. However, it should be critically noted that the occurrence of PFAS with chain lengths > C10 in drinking water is extremely unlikely or almost impossible, as they are predominantly bound to solids in the environment or enriched in the vadose zone at the air/water interface. The strong tendency of these compounds to accumulate at interfaces also has an enormous impact on their analysis from water, as they also tend to adsorb here, e.g. on vessel walls, and there is therefore also a risk of strong underreporting and carry-over. However, as these substances are now regulated, the new European standard EN 17892 was developed in the technical committee CEN/TC 230 Water Analysis. This was published in August 2024 and is recommended in the technical guideline as the analytical method for sum of PFAS. It describes the two variants of HPLC-MS/MS determination: method with direct injection and method after solid phase extraction (SPE). This standard takes particular account of the improved detectability of long-chain PFAAs and the need for low limits of quantification (on average 1.5 ng/L per individual substance). DIN was in charge of the project. Through the DIN working group NA 119-01-03-02-21 AK “Per- and polyfluorinated alkyl substances (PFAS)”, a representative of TZW actively participated in this standardization project.
PFAS Total as a problematic parameter
There is currently no harmonized and standardized method for the parameter PFAS Total. As every analytical method has a certain analytical window, there can at best only be a proxy method for PFAS Total. As Directive 2020/2184 does not contain a definition of the term PFAS, it was determined in the consultation project with the Commission that the OECD definition from 2021 should be applied. According to this definition, any substance that contains at least one -CF2 or one -CF3 group counts as a PFAS, with a few exceptions. In total, around 6.5 million compounds belong to this group of substances. These include, for example, many active ingredients of pesticides and pharmaceuticals and their metabolites as well as the ultra-short-chain PFAAs trifluoroacetic acid (TFA) and perfluoropropionic acid (PFPrA). TFA in particular, which is currently still considered to be of low toxicity to humans, dominates the PFAS content in drinking water. The main cause of TFA contamination is the degradation of precursors, such as fluorocarbons used in refrigerants for air conditioning systems or pesticides. If the parameter PFAS Total were to be used for monitoring in an EU member state, numerous waterworks would exceed the parametric value of 0.5 µg/L after it came into force due to TFA concentrations alone. Therefore, the Commission proposes in Directive C/2024/4910 for PFAS Total that the TFA concentration should be determined separately and subtracted from the PFAS Total concentration including TFA. For methodological reasons, however, this leads to large inaccuracies, i.e. to inconclusive results, and can therefore not be recommended from an analytical point of view. This challenge does not currently exist for German waterworks with regard to TFA, as the parameter PFAS Total has not been included in the Drinking Water Ordinance and there is otherwise a comparatively high limit for TFA of 10 µg/L as a non-relevant pesticide metabolite (nrM) and a drinking water guideline value of 60 µg/L.
Focus on PFAS is important
Despite the lack of definitions and technically dubious specifications regarding the PFAS parameters in EU Directive 2020/2184 and all the resulting analytical challenges, it is to be welcomed that the PFAS substance group is now receiving a great deal of attention in the EU. This not only supports the EU's Zero Pollution Strategy, but also the efforts to achieve a far-reaching restriction of PFAS in the EU. However, the simple addition of PFAS concentrations without considering their toxicological relevance must be viewed critically and could lead to difficulties for affected water supplies in the future. This is particularly the case if toxicologically less critical, short-chain, mobile PFAAs, that are difficult to remove by treatment, such as perfluorobutanoic acid (PFBA), make a large contribution to the total concentration of PFAS. For the protection of human health, a sum parameter that covers both very short-chain and long-chain PFAS with completely different toxicological properties appears to make little sense.
Scientific article
Persulfate-based total oxidizable precursor (TOP) assay approaches for advanced PFAS assessment in the environment – A review - (Link to ScienceDirect)
Comprehensive expertise at TZW
TZW: DVGW-Technologiezentrum Wasser (German Water Centre) has been involved with the PFAS substance group from an early stage and has carried out extensive research in this field. In addition, numerous technical and scientific expertises have been prepared for clients from various sectors such as water supply, authorities, industry and infrastructure. The topics of PFAS transport in groundwater, mass transport of PFAS from contaminated soils into crops, and the release of PFAS from materials are therefore also part of the portfolio.
Info flyer ‘PFAS in the environment. Requirements and solutions’ (pdf-file)
Current research projects at TZW on the topic
PFClean - Innovative modular system for the sustainable reduction of PFAS contaminants from soil and groundwater
ZeroPM - Zero Pollution of persistent and mobile substances
KapilloPFAS - PFAS removal by means of nanofiltration
