The life of pesticides does not stop at the fields. Once spread, they infiltrate the soil, are transformed, and sometimes end up in the water tables pumped to supply the water supply networks. And therefore, ultimately, in tap water. The vast majority of water analyzes reveal nothing alarming, but some networks show levels of certain molecules beyond the quality thresholds.
>> INFOGRAPHICS. What we know about pesticide residues in the tap water of thousands of municipalities (and uncertainties about their toxicity)
Is your municipality affected? On the occasion of the broadcast of a “Complément d’Enquête” survey on France 2 and an article by WorldThursday September 22, franceinfo has created a search engine that compiles data from the Ministry of Health. It will allow you to know the number of samples, taken between January 2021 and July 2022, during which molecules of pesticides, or their metabolites (derivatives of pesticides), were sought. And if exceedances of the quality threshold (most set at 0.1 μg/L) were observed.
A municipality is sometimes crossed by different distribution networks, on which samples are taken. It is therefore possible that by typing the name of your municipality, you will find several results. The data provided by the Ministry of Health indicates details on the network and the district it supplies (indicated in the second column in the table below). This can help you find the result that concerns you.
Does exceeding the quality limit for a molecule mean that drinking tap water is toxic?
For most of the molecules concerned, the health authorities explain that these overruns do not mean that drinking the water is toxic. It is still declared “non-compliant with quality requirements”, and the manager is required to implement measures to stem the phenomenon. The water therefore continues to be distributed, as long as it does not exceed a second threshold, called “maximum sanitary value” (Vmax). This threshold is set according to the toxicological data of the substance in question. For the ESA metolachlor, which often appears in the table above, this “Vmax” is set at 510 μg/L, a threshold never exceeded over the period we studied.
On the other hand, for certain molecules, this second threshold does not exist. D‘after ANSES data, there are thus 23 pesticides or metabolites for which the authorities have not defined a maximum health value. Due to a lack of scientific knowledge and knowledge of toxicological limits, “Anses may not be able to provide Vmax”, Explain the organism. It is therefore difficult to know from what threshold drinking water containing these molecules becomes dangerous. In some cases, the health authorities have defined a “transitional health value”: a new limit that does not provide, for the moment, for an automatic ban on the consumption of tap water, but which reinforces surveillance. For example, for desphenyl chloridazone (one of the most frequent molecules in terms of excess), this new threshold is set at 3 μg/L.
No sample has tested pesticide molecules in the distribution network of my municipality. How to explain it?
There are hundreds of molecules of pesticides and metabolites, and not all of them are systematically searched for in tap water. This list is defined locally. It depends on the phytosanitary products most used on the territory; the population density in the territory of the water distribution network; the ability of laboratories in the region to detect such and such a new metabolite molecule; financial resources from the ARS to carry out these costly operations.
Moreover, having no pesticide molecule tested during sampling does not mean that your tap water is not monitored. Many other parameters are scrutinized in your municipality: microbacteria, acidity, nitrates… To consult the list, you can consult the details of the analysis results on the website of the Ministry of Health.
Finally, in some municipalities, we noticed imperfections in the data published by the ministry. For several towns in Ile-de-France, for example, no analysis is recorded, because they have only been informed about the town where the water production plant is located. Thus, the town of Issy-les-Moulineaux is supplied by the factory of Choisy-le-Roi: it is necessary to consult the site of the Syndicat des eaux d’Ile-de-France (Sedif) to find out, and search for Choisy -le-Roi to find out the results of pesticide analyzes concerning the municipalities that the plant distributes.
To carry out this work, franceinfo.fr worked with the “Complément d’Enquête” teams and the datajournalist Alexandre Lechenet. From an initial data compilation work carried out by the latter, we carried out our own analysis. It is based on data from the SISE-Eaux database, which is a national tool for monitoring the quality of water intended for human consumption. This tool monitors dozens of parameters, concerning micro-organisms (bacteria, viruses…), nitrates, radioactivity, lead… Pesticides being only part of these parameters, it was necessary to filter the SISE-Eaux database using a list of pesticide molecules defined upstream.
To produce this initial list, with the aim of approaching completeness, we have compiled the pesticide databases established by ANSES (here or here), the Ministry of Ecological Transition, Sandre, also supplemented by our cares. In the end, we collected the results for 1,137 pesticide molecules or their metabolites. From then on, we were able to analyze the results of the samples by compiling the data by molecule, distribution network, municipality.