Data from regional health agencies, and collated by Le Monde, found that supplies to about 20 percent of the population, up from 5.9 percent the year previously, failed to consistently meet regional quality standards. 

The study highlighted regional differences in tap water quality. Hauts-de-France water was the most likely to be affected, with 65 percent of the population there drinking water contaminated by unacceptable pesticide levels. In Brittany, that level fell to 43 percent; 25.5 percent in the Grand-Est, and 25 percent in the Pays de la Loire.

Occitanie, in southwest France, meanwhile, showed the lowest level of non-compliance with standards, with just 5.1 percent of the region’s population affected by high pesticide levels in their tap water. However, figures show that 71 percent of people in one département in the region, Gers, were supplied with water containing high levels of pesticides.

Regional discrepancies in testing, including what chemicals are tested for, mean that results and standards are not uniform across France. Tap water in Haute-Corse is tested for 24 pesticide molecules; in Hauts-de-Seine, that figure rises to 477. 

One reason for regional testing standards are differences in local agricultural requirements.

Part of the increase in the year-on-year number of households supplied with affected water may also be explained by the fact that tests in many regions now seek to trace more molecules, Le Monde noted.

Water quality standards in France are strict – with a limit for pesticide residues set at 0.1 microgramme per litre, so the “high” levels found in tap water supplies may not represent a danger to health.

The question of the level of health risk to humans, therefore, remains unclear. The Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail (Anses) has not defined a maximum safety level for 23 pesticides or their metabolites. Le Monde cites two metabolites of chloridazone, a herbicide used until 2020 on beet fields, for which only provisional safety levels in tap water have been set. 

Many of these molecules and their long-term effects remain unknown – and “the long-term health effects of exposure to low doses of pesticides are difficult to assess,” admits the Ministry of Health.

Michel Laforcade, former director general of the ARS Nouvelle-Aquitaine told Le Monde that health authorities have “failed” on this subject. 

“One day, we will have to give an account,” he said. “It may not be on the same scale as the contaminated blood affair, but it could become the next public health scandal.”

In December 2020, the Direction générale de la santé (DGS) recommended “restricting uses of water” as soon as the 0.1 micrograms per litre quality threshold is exceeded, in cases of residues for which there is no formal maximum health value.

But this principle is not always applied, according to France 2’s Complètement d’enquête programme.

In December 2021, the DGS asked the Haut conseil de la santé publique (HCSP) “for support on the management of health risks associated with the presence of pesticides and pesticide metabolites in water intended for human consumption.”

The HCSP, in response, said that “an active and urgent policy must be implemented to reduce the contamination of resources by pesticides”.