In May, the world revealed that 97% of French groundwater was contaminated by one or more pesticides, or by degradation products of these substances: metabolites. In particular, 20% of aquifers present levels higher than regulatory quality thresholds, but the reality could be even more worrying. In a report made public on Tuesday, October 15, the Générations Futures association identified several dozen pesticide metabolites that the authorities consider to pose a risk of groundwater contamination and which, however, are not subject to any monitoring. They are not sought in groundwater, nor at the end of the chain, in tap water.
Générations Futures estimates that, according to current knowledge, there are fifty-six of these substances, a dozen of which are particularly problematic for groundwater. Two of them concentrate, according to the association, a large part of the risks: DIPA (diisopropylamine) and TFA (trifluoroacetic acid). The first is a metabolite of a herbicide, triallate, authorized since the 1960s and which was withdrawn from the French market last year. The second belongs to the family of perfluoroalkyl and polyfluoroalkyl substances, PFAS, called “eternal pollutants” due to their persistence in the environment and in contaminated organisms. It comes, among other things, from the degradation of a herbicide called flufenacet, still authorized in Europe and France.
In just a few years, the issue of metabolites in water has become critical. These substances are the cause of numerous non-compliance in water intended for human consumption. In 2022, according to official data, almost 11 million French people received tap water that did not meet quality criteria. “Despite the seriousness of the situation, today we only see the tip of the icebergsays Pauline Cervan, a former industry regulatory toxicologist and lead author of the report. We are largely unaware of the real state of our water resources and, therefore, the quality of the tap water distributed to tens of millions of people. »
And with good reason: today, while 188 molecules have been the subject of at least one analysis since 2022, three pesticide metabolites, derived respectively from chlorothalonil, chloridazone and S-metolachlor, are solely responsible for the majority of the excesses. These substances have been used for more than half a century without their metabolites having been investigated, although sometimes their potential to contaminate groundwater has been known for a long time. And in both cases, ten years passed between the first alerts at European level and the entry into force of the first surveillance measures in France.
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