PFAS: results of the national measurement campaign for drinking water
Gaining a better understanding of drinking water contamination
ANSES regularly conducts campaigns to measure the presence of emerging compounds in water, in order to improve knowledge of the contamination of raw and mains-supplied water in France. The compounds targeted in these campaigns are selected either because they are not already covered by regulatory monitoring of water, or because the available data on their presence are incomplete. This campaign, which began in 2023, concentrated on substances in the PFAS group (per- and polyfluoroalkyl compounds).
These substances have been the focus of numerous studies in recent years, particularly by ANSES, with a view to improving their detection, understanding their presence in the environment and assessing their potential toxicity. However, still not enough is known about the presence of PFAS in drinking water. Only a few of these substances are monitored.
The European Drinking Water Directive laid down an initial list of 20 PFAS to be monitored in the water distributed in France, by 12 January 2026 at the latest. The aim of ANSES's measurement campaign was therefore to gain a picture of their presence before this deadline and identify other PFAS that should also be monitored.
Thirty-five PFAS screened for in tap water
Fifteen additional PFAS were also screened for during this campaign, besides the 20 substances in the Directive. They were selected on the basis of a number of criteria, such as their physico-chemical properties (particularly their affinity for water) and the availability of data showing their presence in water, in France or abroad.
The sampling campaign took place throughout France, including in the overseas territories. Over 600 samples of raw water and the same number from mains-supplied water were analysed, twice as many as in previous campaigns. They were taken from abstraction sites representing in total around 20% of the mains-supplied water in France. Two-thirds of the samples were taken at points where a potential risk of PFAS contamination had been identified by the regional health agencies.
Some PFAS more common than others
Of the 35 PFAS screened for, 20 were detected in at least one raw water sample and 19 in at least one sample of mains-supplied water.
Among the detected substances were 11 PFAS listed in the Drinking Water Directive, three of which were found more frequently: PFHxS (21.7% of mains water samples), PFOS (19.1%) and PFHxA (16.1%). The Directive sets a quality limit of 100 ng/L for the sum of concentrations of the 20 PFAS it considers. Only a small proportion of the samples exceeded this value.
Of the other PFAS detected, four were "conventional". This refers to PFAS with chains of more than three carbon atoms. These PFAS, in particular 6:2 FTSA, were generally detected in samples that also contained at least one of the PFAS included in the Directive. This shows that the PFAS listed in the Directive are good indicators of the presence of conventional PFAS.
Five ultra-short-chain PFAS, i.e. compounds with one to three carbon atoms, were also screened for. Particular attention was paid to these substances, because this category is not represented in the 20 PFAS whose monitoring is provided for in the Directive. Their occurrence appears to be independent of that of conventional PFAS. Three of them were found in several samples. The most common, trifluoroacetic acid (TFA), was found in 92% of both raw and mains water samples. Its concentration varied greatly from one sample to another, with a median of 780 ng/L in mains-supplied water. The study also identified, for the first time in France, the significant presence of trifluoromethanesulfonic acid (TFMSA) in 13% of samples, with a median concentration of 28.5 ng/L in mains-supplied water.
Essential results for improving the monitoring of PFAS in water
The results of this campaign supplement the ANSES expert appraisal published in October 2025, in which the Agency made recommendations to improve the monitoring of PFAS in various compartments, including water. Certain PFAS detected during the measurement campaign could be added to the permanent monitoring plan for water, as recommended by the expert appraisal. This mainly concerns TFA (among the ultra-short-chain PFAS) and 6:2 FTSA (among the conventional PFAS), as among the substances not listed in the Directive, the latter was detected more frequently.