Tritium on tap ? “Margeride water is of excellent quality!”, replies the mayor of Monts-de-Randon to the Criirad

Le granit de la Margeride libère naturellement du tritium. Midi Libre – LUC CRESPON LHERISSON

Francis Saint-Léger réagit à l’enquête révélée par Médiapart faisant état de seuils de tritium, un atome radioactif, au-delà du bruit de fonds naturel.

“Many people have been contacting me, worried, since the publication of this investigation”. The mayor of Monts-de-Randon, Francis Saint-Léger, has not hidden his annoyance since his small town of 1,200 inhabitants, created in 2019 from the merger of Rieutort-de-Randon, Saint-Amans, Servières, Estables and La Villedieu, appeared on the list of 2,300 towns and villages where drinking water analyses revealed the presence of tritium, a radioactive element above the background level of 2 becquerels per liter.

On the Lozère plateau, which peaks at 1,550 metres, the information from the CRIIRAD (Independent Research and Information Commission on Radioactivity) was all the more surprising since this radionuclide, derived from hydrogen, is mainly released by nuclear installations. “The national record is found in the Vienne, downstream from the Civaux power plant, 65 becquerels per litre. Tritium mainly comes from human activity, for example also in medical imaging, and here, it remains limited”, comments Francis Saint-Léger. He therefore conducted investigations with the relevant authorities, particularly the ARS, to understand how Monts-de-Randon found itself “pinned” by the Criirad.

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In its natural state

First element of response: “tritium exists in its natural state in certain geological soils, particularly granite”.However, the Margeride is one of the largest granite massifs in Europe and the background noise of tritium can reach, the elected official believes, “5 to 8 becquerels per litre. But there is a margin of error of 4 becquerels, which explains why we were able to have an analysis at 11 becquerels” , like other neighbouring communes.

These figures should also be put into perspective, says the Lozérien. The Criirad has communicated the list of municipalities where the tritium rate exceeded 10 becquerels per liter, “while the health authorities still consider that at 100 becquerels the drinking water is of excellent quality. The WHO, for its part, has set the alert threshold at 10,000 becquerels per liter, or 1,000 times more than the figure recorded in Monts-de-Randon”.

“Once, on a catchment”

Another fact to take into account is that this rate of 11 becquerels was recorded “only once, between 2016 and 2024, on just one of our twenty catchments and this one does not serve the entire municipality, but only about ten inhabitants, in Servières”. And, assures Francis Saint-Léger, these are very regularly monitored. “We do not draw from groundwater, but from the surface, in Charpal or Fortunio, and if the rain erodes the agricultural land, a few bacteria can be revealed, hence the large number of checks”, explains the elected official. He therefore affirms it, to reassure his population: “I cannot let it be said that the water of the Margeride is polluted. It is of excellent quality”.

Twenty Gard municipalities

The Criirad investigation, published Monday by Mediapart, revealed thresholds above 10 becquerels per liter also in the Gard department. Twenty municipalities exceeded it at least once, with concentrations reaching up to 18 becquerels in Nîmes, and 20 in Caveirac, Calvisson and Congénies, three cities that are nevertheless far from the Tricastin-Marcoule nuclear territory. “From a scientific point of view, this concentration raises some questions, however, it is not alarming. Even at 100 becquerels per liter, there is no danger to human health, we are on a precautionary principle”, analyzes Loïc Ducros, lecturer in environmental geosciences at the University of Nîmes.

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