Raw water and tap water: TFA, the omnipresent PFAS

Drinking water is a major concern regarding pollution. It is also the most regulated element of our food supply in France. PFAS, also known as "perennial pollutants," are at the forefront of a scene already crowded with other pollutants due to their extreme persistence. Which of these molecules are likely to end up in our drinking water?

The latest national campaign by the Nancy Hydrology Laboratory (LHN), part of theFrench Agency for Food, Environmental and Occupational Health & Safety (ANSES), analyzed drinking water specifically targeting this class of chemical compounds. The results were published on December 3, 2025. What can we conclude from this? report of 60 pages, of these 647 samples in raw water and 627 in distributed water?

35 PFAS examined

The collection of sampling points visited represents 20 % of the water distributed in France. They were chosen according to different typologies: high flow rate, randomly selected sampling site, sites designated by the Regional Health Agencies for their " vulnerability or as potential sources of pollution.

35 PFAS were sought in samples taken in metropolitan and overseas France by the Regional Health Agencies.

• 20 “perennial pollutants” listed in the European directive on waters intended for human consumption applicable at the latest from January 12, 2026. Nine of them never appear in the analyses of this report presented yesterday by the LHN. These are hydrophobic molecules. (…) "And so it's quite logical that they were never found during this campaign."explains Xavier Dauchy.
• Fifteen others were selected by ANSES and LHN for their chemical affinity with water, or in other words, their ability to persist in water. The newly added PFAS were chosen based on existing scientific data or information provided by the Regional Health Agencies (ARS).

The list retained by the LHN includes long-chain PFAS (more than three carbon chains) and incorporates others with ultra-short chains (less than three carbon chains) including trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFMSA).

Some PFAS are present, but at low levels…

Of the 35 PFAS analyzed, 20 were detected in at least one raw water sample and 19 in the distributed water. Among the long-chain PFAS most frequently found in samples, in both raw and treated water, were PFHxS, PFOS, and PFHxA. In treated water, PFBA, PFPeA, and PFOS sometimes showed individual values exceeding 100 ng/L (nanograms per liter, which expresses the mass of dissolved or dispersed substances in one liter of water). This quality threshold of 100 ng/L, to put it in the context of European Union regulations, is the maximum concentration allowed for 20 PFAS!

A key point to remember amidst a report that is difficult for the layperson to decipher: the LHN and Anses note that the water intake sites, the largest in terms of water flow, " are relatively exposed to the various routes of PFAS dissemination.Water resources are " vulnerable [when they are] near PFAS-emitting activities, and more disturbingly, " "Some potential sources are probably still poorly identified and therefore poorly characterized.".

TFA, sought after, ubiquitous, and a molecule of interest

The most surprising result is certainly the predominant presence of TFA, or trifluoroacetic acid: 92% of both raw and distributed water samples contained it! When you look, you find!", one of the members of the LHN working group said ironically during the press conference. "The data from the laboratory campaign confirmed our belief that TFA was a molecule of interest.".

Ultra-short-chain PFAS warrants the full attention of health authorities due to its widespread presence, although concentrations vary from one sample to another. The maximum concentration recorded by the LHN is 25 μg/L, admittedly lower than the French health guideline value of 60 μg/L for drinking water. However, this 25 μg/L exceeds the target limit of 10 μg/L. recommendation from the High Council for Public Health in 2024. One European country has adopted an even lower limit: the Netherlands with an indicative health value of 2 μg/L. As a reminder, it is not part of the list of 20 "perennial pollutants" already included in the European directive.

Another ultra-short-chain PFAS to watch out for

Trifluoromethanesulfonic acid (TFMSA) is another surprise in the report's findings. It appears in these official data for the first time in France. It is used as a catalyst or reagent in numerous chemical syntheses, as well as an electrolyte in lithium batteries. Its presence is not as high as that of TFA, but it too is among the top five most prevalent substances in the samples. It is also an ultra-short-chain PFAS, present in 131 of the samples, with a median concentration of 28.5 ng/L in the distributed water (0.0285 μg/L).

And what about PFAS pesticides?

The report does not mention the link between PFAS pesticides and their degradation into TFA, brought to light by NGO alert campaigns in 2023. The LHN “ is not intended to duplicate existing operational surveillance."We are told at a press conference. Danish researchers have determined that at least seven active ingredients in pesticides can produce TFA (transient factor analogous to flaccid paralysis). Several European countries, including France, have called for an accelerated review of the quality limits for these products. However, we are not necessarily in alarm zones with regard to health standards. (For pesticides, if the quality limit is exceeded but the value remains below the health value, the water is still drinkable. However, measures must be taken by the operator to restore compliance. A health value depends on the current state of knowledge about the substance. - Ed.)“.

No link between ultra-short-chain PFAS and other PFAS

One might have imagined that long-chain PFAS could degrade into TFA or TFMSA. The report refutes this idea. There is no co-occurrence between these short-chain PFAS and the other PFAS analyzed during the campaign. "No statistical link could be established between the presence of TFA/TFMSA and that of the others" (…). This leads us to believe that the major sources of TFA and TFMSA emissions are unrelated to those of other PFAS.”