The National Food Safety Agency (ANSES) studied water samples throughout the country, including overseas territories, in particular looking for 157 pesticides and their metabolites, i.e. components resulting from their degradation.
“Of the 157 molecules searched, 89 were quantified at least once”says ANSES. “The quantification frequencies are quite similar between raw water/treated water and between groundwater/surface water”she observes.
One case in particular caught the attention of experts: the metabolite of chlorothalonil – the most frequently found metabolite, “in more than one out of two samples” – which leads to overruns of the quality limit (0.1 µg/litre) “in more than one out of three samples”.
This metabolite comes from the degradation in the environment of chlorothalonil, a fungicide yet banned in France since 2020.
A pesticide banned in France
“These results show that, depending on their properties, certain pesticide metabolites can remain present in the environment for several years after the banning of the active substance from which they originated”concludes ANSES.
The European Commission had not renewed in 2019 the authorization of chlorothalonil, marketed by the German Syngenta, and France had granted a grace period until May 2020 for the disposal of stocks of this product.
Brussels then underlined that it was “impossible to date to establish that the presence of metabolites of chlorothalonil in groundwater will not have harmful effects on human health”.
The Commission quoted the conclusions of the European Food Safety Authority, which considered that chlorothalonil “should be classified as a category 1B carcinogen”i.e. carcinogenic “Assumed”.
The Paris basin and the Great West particularly concerned
It is impossible, for the time being, to precisely determine the percentage of the population concerned, as R471811 has not yet been integrated into the surveillance plans of all the regional health agencies (ARS).
Nevertheless, ANSES certifies in its report that large densely populated areas are affected, such as the entire Paris basin, capital included. The Syndicat des eaux d’Ile-de-France (Sedif), which serves 4 million users, confirms that more than 3 million of them receive water whose R471811 content is four to five times higher than the regulatory threshold. .
In the Great West, the situation is no different. “We have been looking for this molecule since January and we find it almost everywheresays in the columns of Le Monde Mickaël Derangeon, vice-president of Atlantic’Eau, one of the public water services in Loire-Atlantique. Of our 550,000 subscribers, 490,000 receive water that is not compliant.”
That is approximately 90% of the population served, which receives water whose content of R471811 (one of the metabolites of chlorothalonil) is two to six times above the quality standard.