Per- and polyfluoroalkyl substances, better known as PFAS, have become one of Europe’s most closely watched drinking-water contaminants. Often called “forever chemicals” because many resist natural degradation, PFAS can persist in groundwater, rivers, soils and human bodies for years or even decades. A new analysis of national drinking-water rules finds that European Union member states have largely adopted the bloc’s legally binding PFAS limit, but have done so with important differences that could leave residents in different countries protected to different degrees.
The study, published in Nature Water, examines how EU countries implemented the Drinking Water Directive requirements that took effect in January 2026. The directive introduced two ways of regulating PFAS in drinking water: a “sum of PFAS” parameter with a limit value of 0.1 micrograms per litre, and a broader “PFAS total” parameter with a limit of 0.5 micrograms per litre. The first covers a defined group of PFAS compounds, while the second is intended to capture a wider range of substances, depending on the analytical method used by authorities.
According to the researchers, all but one EU member state have adopted the 0.1 microgram-per-litre limit for the sum of PFAS. Several countries have also introduced the 0.5 microgram-per-litre limit for total PFAS, but only alongside the sum-of-PFAS requirement. No member state has adopted the total-PFAS parameter on its own. This pattern suggests that national regulators generally view the narrower sum parameter as the essential legal safeguard, while treating the broader total measure as an additional tool for surveillance or risk management.
The distinction between these parameters is technically significant. PFAS is not a single chemical but a large family containing thousands of fluorinated compounds with different structures, uses and toxicological profiles. Laboratory testing cannot necessarily identify every PFAS molecule in a water sample. Instead, regulators rely on targeted methods that quantify selected compounds or on broader analytical approaches that estimate total organic fluorine or related chemical categories. The choice of method can therefore influence which substances are detected, how concentrations are reported and whether a sample appears to comply with a legal limit.
The analysis also found that national authorities frequently went beyond the minimum requirements of the directive. Nine member states implemented a limit for the sum of four specific PFAS: perfluorooctanoic acid, or PFOA; perfluorooctane sulfonic acid, or PFOS; perfluorononanoic acid, or PFNA; and perfluorohexane sulfonic acid, or PFHxS. These compounds are among the most extensively studied PFAS and have been associated with concerns involving immune function, development, metabolism and other health effects. PFOA and PFOS, in particular, have been widely restricted or phased out in many applications, although they can remain in the environment because of their persistence.
The four-compound approach has moved faster than the broader European framework, the researchers report, but it has also emerged in a more uneven and fragmented way. Some countries have established additional national thresholds, monitoring obligations or enforcement arrangements, while others have stayed closer to the minimum wording of the directive. The result is a regulatory landscape in which the same measured PFAS concentration may trigger different responses depending on where the water is sampled. For a contaminant that can travel across borders through rivers, groundwater and industrial supply chains, such variation may complicate prevention and accountability.
PFAS contamination can originate from numerous sources, including firefighting foams, industrial production, metal plating, water-resistant textiles, food-contact materials and some consumer products. Once released, many compounds move readily through water and can be difficult to remove using conventional treatment. Activated carbon and high-pressure membrane technologies such as reverse osmosis can reduce PFAS concentrations, but they may be expensive, energy-intensive or challenging to operate at large scale. Treatment also transfers contaminants into concentrated waste streams, meaning that removing PFAS from drinking water does not necessarily eliminate the underlying pollution problem.
The researchers identify an institutional challenge as well. In some national systems, agencies responsible for monitoring water quality are separate from bodies responsible for legal oversight and enforcement. That division can make it harder to connect laboratory findings with rapid mitigation, identify polluters or coordinate action among water suppliers, environmental regulators and public-health authorities. A sample may reveal a worrying trend, yet the response can be slowed if responsibilities are divided among institutions with different mandates, databases and procedures.
Another complication involves trifluoroacetic acid, or TFA, a highly mobile and persistent fluorinated compound that can enter water through industrial processes and the breakdown of certain chemicals, including some fluorinated pesticides and refrigerants. TFA is structurally different from many of the long-chain PFAS that dominate public debate, and its regulatory treatment varies. However, if TFA is considered a toxicologically relevant pesticide metabolite under applicable rules, supplying drinking water that meets legal requirements could become substantially more difficult. Its mobility and resistance to removal make it a particular concern for vulnerable water supplies.
The European experience illustrates the difficulty of regulating a rapidly expanding chemical family with incomplete toxicological and environmental data. Uniform limits can provide a common baseline, but effective protection also depends on consistent monitoring, transparent analytical methods, clear enforcement and measures that prevent contamination at its source. The new assessment suggests that Europe has taken a major step by making PFAS limits legally effective, yet the uneven national approaches could determine whether that step produces genuinely equal protection—or a patchwork in which the safety of drinking water depends on the country in which it is tested.
Subject of Research: Implementation of European Union drinking-water limits for per- and polyfluoroalkyl substances (PFAS).
Article Title: Implementation of the Drinking Water Directive limit values for per- and polyfluoroalkyl substances in Europe.
Article References: Hansen, S.F., Hjorth, R., Baun, A. et al. “Implementation of the Drinking Water Directive limit values for per- and polyfluoroalkyl substances in Europe.” Nature Water (2026). https://doi.org/10.1038/s44221-026-00670-5
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s44221-026-00670-5
Keywords: PFAS, forever chemicals, drinking water, European Union, Drinking Water Directive, PFOA, PFOS, PFNA, PFHxS, water quality, environmental health, chemical regulation
