The La Rochelle agglomeration has discovered two by-products of herbicides in its drinking water, one of which is currently banned, and the other will be banned soon. The community has filed a formal complaint about this issue. The Fraise-Bois Boulard water station, located in a forest purchased by the agglomeration, has been given enhanced protection to reduce exposure to pesticides. According to a public analysis released on September 18, based on samples collected on September 4, the La Rochelle Agglomeration Community (CdA) found two herbicide by-products that exceeded the alert threshold of 0.1 microgram (μg) per liter: S-metolachlor and flufenacet. S-metolachlor has been banned since 2024 for use on crops like corn, soy, and sunflower, while flufenacet, a herbicide used on barley and wheat, is banned from sale since 2025 and from use starting December 10, 2026. Guillaume Krabal, the vice-president of the agglomeration in charge of water, expressed his surprise: "We don't understand." On Friday, September 25, the community filed a complaint against an unnamed entity for pollution with the public prosecutor, hoping that the judiciary would take up the case to trace the source. The area has had a long history of health alerts related to banned or dangerous substances since 2021. These include water contamination with chlorotoluron, record levels of prosulfocarb in the air, and pollution of a water source with chlorothalonil—two herbicides and a fungicide. The two molecules detected this time had never been found at such high concentrations before: "We test a list of about 300 molecules established by the Regional Health Authority," explains Serge Ceaux, director of water for the CdA. "We had already detected traces above the detection threshold, at 0.01 μg per liter, but never more." The two substances found are metabolites—products resulting from the breakdown—of well-known pesticides: S-metolachlor and flufenacet. "When I learned this, I contacted the farmers in the region," says Guillaume Krabal. "They were shocked because they say they have not started sowing due to lack of rain: there is therefore no reason to use flufenacet." The agricultural chamber, when contacted by Reporterre, did not follow up on the issue. A previous complaint filed in 2021 following the contamination of the Clavette water source led to an investigation initiated by the prosecutor of La Rochelle. Searches had taken place in agricultural operations in the region, but the procedure was closed without conclusion due to the failure to identify the responsible parties. The water drawn from the contaminated capture area, flowing through a pipeline of about twenty kilometers, supplies 20,000 people in the agglomeration of Bourgneuf, Montroy, and part of the central area of La Rochelle. In an agglomeration of just under 200,000 inhabitants where the League against Cancer in Charente-Maritime has identified no fewer than four pediatric cancer clusters, this detection reignites concerns. However, the risk assessment proves difficult: while studies confirm the effects on human health of S-metolachlor—a suspected carcinogen—and flufenacet—a PFAS-type eternal pollutant and endocrine disruptor—their by-products remain little studied. "The ESA-flufenacet detected is considered relevant by Anses, but there is very little data," laments Pauline Cervan, a toxicologist at the NGO Générations Futures, who had campaigned for the ban on the herbicide. "Its chronic effects are almost not studied, like most of the metabolites." The presence of these molecules, which fell below the detection threshold in two control samples taken since September 18, questions the effectiveness of strategies to combat agricultural pollution. Inaugurated in 1925, the Fraise-Bois Boulard water source was the subject of many protection measures under the Grenelle environmental initiative: after purchasing the forest where the installations are located, the CdA had implemented assistance for virtuous agricultural practices (reduction of pesticides, maintenance of meadows, reduction of water consumption) that could go up to 300 euros per hectare. Despite this, the metabolites found their way to the pumps. "We experiment and we play our role in information relay," notes modestly Guillaume Krabal. "But without national assistance, there will be no progress." Already fragile, the legal framework for the protection of water capture zones has recently been further weakened. Made public this week, the draft decree implementing the highly controversial agricultural emergency law saw the number of sensitive water capture points—capable of being subject to pesticide restrictions—drop from 6,000 to 2,300 in France. "Fraise-Bois Boulard is part of the capture points that will not be protected," sighs Serge Ceaux. Spokesperson for the association Avenir santé environnement 17, which has been at the forefront of mobilization following pediatric cancers, Franck Rinchet-Girollet expresses a muted anger: "Programs like ReSources, such as those implemented by the CdA, only work if farmers are willing: as long as we remain in the incentive-based approach, we won't move forward." And he concludes: "The only solution is to shift the agricultural model and ban dangerous substances."