Identification and quantification of PFAS in the tap water of a French City, Besançon

In France, information on per- and poly-fluoroalkyl substances (PFAS) in residential tap water is still limited or non-existent. In this study, we conducted a local survey to compare human exposure to PFAS in 28 private family households in a medium-sized French city (Besançon). We present the results on the identification and quantification of 65 PFAS substances in residential tap water. Concentrations of PFAS were assessed by a French accredited laboratory. A total of 74 tap water samples were analyzed, revealing the presence of 12 individual molecules, 8 of which are among the 20 regulated substances. Forty-one samples contained a mixture of 2 to 10 different PFAS substances, the most frequently quantified molecules being trifluoroacetic acid (100%), perfluorooctanoic acid (48.6%), perfluorooctane sulfonic acid (44.6%), perfluorobutanoic acid (27.0%), perfluoropentanoic acid (50.1%), and perfluorohexanoic acid (23.0%). The corresponding cumulative concentrations (sum of 65 substances) ranged from 440 ng/L to 3,805 ng/L, showing significant variability. However, in terms of regulations, all values were below the 100 ng/L limit for the sum of the 20 molecules. Trifluoroacetic acid, which is not on the regulatory PFAS list, was systematically found in all the water samples analyzed and the results clearly highlighted the dominance of this PFAS. In tap water, trifluoroacetic acid was quantified at concentrations ranging from 440 to 3,800 ng/L (average value of 1096 ± 575 ng/L), i.e., 4 to 38 times higher than the regulatory threshold of 100 ng/L. This study underlines the need to monitor not only the 20 substances listed in the European Directive, transposed into French law, but also other PFAS, and, above all, to include trifluoroacetic acid.