Forever chemicals turned up at about 60% of French river sites in a 20-year study

Per- and polyfluoroalkyl substances, the persistent compounds known as forever chemicals, were found at about 60% of the sites in France’s national river and lake monitoring records. Researchers at RPTU University Kaiserslautern-Landau in Germany combed through more than 20 years of that data. They released the findings on Nov. 9, in a paper published in Water Research.

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The same analysis covered 1,731 chemicals in all, a far wider net than earlier work that often looked at pesticides alone. What came back is a picture of waterways polluted almost everywhere, with protected areas faring better but not safely.

PFAS at six in ten monitoring sites

According to the RPTU release distributed through EurekAlert, PFAS turned up at about 60% of sites and are now the second most frequently detected group of chemicals in the dataset. Urban areas averaged between 6 and 11 different PFAS compounds in a year. Lead researcher Danisa Lione said researchers still know relatively little about how PFAS affect aquatic ecosystems, which is the gap the project was built to start narrowing. The release credits the analysis to the Landau campus of RPTU University Kaiserslautern-Landau, and its authors paired the chemical records with toxicity data for aquatic species to judge which organisms are most exposed to harm.

The data come from the French Naiades system, the public Naiades portal where records on the quality of rivers and lakes can be searched by basin, region or monitoring station. The portal carries the logos of the French Republic, the Office francais de la biodiversite and the geological survey BRGM. The U.S. Environmental Protection Agency explains that PFAS are a large family of thousands of chemicals that break down very slowly, which is how the nickname arose.

Protected areas help, with limits

One result cuts in favor of conservation. Samples from protected areas averaged 9 chemicals each, against 13 outside them. Lione said protected areas do significantly reduce the number and frequency of pollutants, a statement the release carries as a direct quotation. The same release adds that the reduction does not amount to full protection, since organic pollutants were detected in nearly all of the water bodies studied.

The paper’s full name is blunt: it says pesticides and organic pollutants pervasively threaten aquatic ecosystems, even in protected areas. The release adds that earlier studies often covered only certain groups such as pesticides, which is what made a 1,731-chemical sweep unusual. Casting the net that wide is also what pulled PFAS into view alongside the older farm-chemical concerns, since the monitoring records span many families of compounds at once.

The number matters because many of France’s best-managed stretches of river sit inside parks and reserves where farming and industry are restricted. A drop of four chemicals per sample is real, but a sample from a reserve still holds close to a dozen. Averages hide spread, and the release gives no per-site breakdown, so the 9 and 13 describe typical samples rather than the best and worst rivers.

Who bears the risk: plants, invertebrates and fish

The team compared measured concentrations with known toxicity to aquatic organisms. Aquatic plants proved the most affected group, followed by invertebrates and then fish. Restrictions on especially problematic pesticides improved conditions for aquatic plants, but the researchers saw no comparable gain for animals. Detecting a compound does not equal harm; the researchers translated concentrations into risk using published toxicity data for aquatic species, which is how plants, invertebrates and fish came to be ranked.

Widening the view beyond pesticides changed the arithmetic. Including non-pesticide organic pollutants raised the estimated risk by 26% for fish and 48% for aquatic invertebrates compared with a pesticide-only analysis. Researcher Jakob Wolfram described the French data as offering an unprecedented look at the problem because of its breadth. The 26% and 48% figures describe estimated risk rather than measured harm, and they come from comparing two modeling choices: pesticides only versus all organic pollutants.

The peer-reviewed study is listed as Water Research, DOI 10.1016/j.watres.2026.127223, and was published online on Oct. 27 ahead of the university’s announcement. The EPA’s PFAS hub notes that researchers are still working out how much exposure is harmful and how to remove and dispose of the compounds. Publication on Oct. 27 and the press announcement on Nov. 9 are separate dates, so the paper has been available to specialists for about two weeks.

Open questions remain about the study itself. The release does not state how many sites were sampled, and it gives conflicting totals for the number of individual measurements, so the paper will need to settle the scale. Until it does, the 60% figure is best read as the share of monitored sites with a PFAS detection, which is the scope the release gives it, and not as a measure of how much of any river is contaminated. The risk figures also depend on the toxicity values used for each chemical, which means they are estimates built on laboratory data. Lione and Wolfram built the work on records the public can already search, which leaves the dataset open to replication.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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