With nearly €1.5 billion of investment, four new wastewater treatment facilities, including a wastewater and stormwater retention basin with a capacity equivalent to 20 Olympic swimming pools, the French government and local authorities have spared no effort to make the Seine swimmable for the Olympic Games, and then for the public from 2025 onwards. The Seine's "swimmability" only provides information on its bacteriological quality, through the monitoring of two families of bacteria (Escherichia coli and enterococci). Another type of pollution, chemical in origin, goes under the radar. A report published on Monday, May 27 revealed "widespread contamination" of waterways in Europe by trifluoroacetic acid (TFA), a "forever chemical" as little known as it is regulated, resulting in particular from the degradation of pesticides belonging to the large family of per- and polyfluoroalkyl substances (PFAS).
The associations of the Pesticide Action Network Europe (PAN Europe) took water samples from 23 rivers and six aquifers in 10 European Union countries (including France, Germany, Spain, Belgium, Austria, and the Netherlands). The analyses were carried out by the renowned Water Technology Centre in Karlsruhe (Germany). The results show the presence of PFAS in all samples, and TFA in over 98%. There is currently no specific standard for this substance, but in almost 80% of the samples, TFA concentrations exceed the limit of 500 nanograms per liter – set for the total amount of PFAS present – of the European Drinking Water Directive, which comes into force from 2026. TFA levels detected ranged from 370 ng/l in the Salzach River, Salzburg, to 3,300 ng/l in the Elbe River, Hamburg (Germany), with an average of 1,180 ng/l.
"This is without doubt the most significant and widespread contamination of European surface and groundwater by a man-made chemical," commented Salomé Roynel, coordinator of the PAN network. Le Monde submitted the results to several experts. All found them "worrisome." "This widespread contamination is very worrying, especially as the levels reported are quite high," said Ian Cousins, professor of environmental chemistry at Stockholm University.
With a concentration of 2,900 ng/l, the Seine is the second most TFA-polluted river after the Elbe. The sample was taken in April next to Notre Dame de Paris, not far from the future public swimming site due to open in the summer of 2025. What is the concern for the health of future swimmers, Olympians, and ordinary people alike? "Occasional swimming won't affect people, but I'd advise against regular bathing," advised toxicologist Jacob de Boer (Vrije Universiteit Amsterdam). "Based on current knowledge of TFA toxicity, I wouldn't worry about swimming in the Seine," said Cousins.
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