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Pesticides in tap water: why the thresholds of the health authorities worry

While one in five households consumed water contaminated with pesticides, ANSES decided to raise the thresholds, thus making the quality compliant.

This is one of the health issues that regularly comes up on the table: the quality of drinking water . According a joint survey of the World and of France 2 , 20% of the population in mainland France consumed water that would exceed the required quality thresholds in 2021, compared to 5.9% in 2020.

And precisely, a news has again made speak at the end of last September. Whereas they were considered until now as potentially dangerous for human health, two metabolites resulting from a pesticide were eventually reassessed by the National Agency for Health, Food, Environment and Labor Safety (ANSES).

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Now deemed “not relevant”, these two substances have seen their maximum authorized threshold be automatically increased from 0.1 micrograms per liter (µg/L) to 0.9 µg/L. For some households, this means that, despite their higher concentration, tap water will once again be in line with consumption. This was not the case before, since compliance was only valid below 0.1 µg/L.

Many associations and collectives warn of health risks.

Where does our tap water come from?

The least we can say is that drinking water makes its way to our tap. In France, it comes mainly from groundwater or rivers, lakes and dams .

Before arriving here, it undergoes a more or less advanced treatment within the 15,000 stations that cover the territory. Objective: to eliminate microorganisms and substances potentially harmful to human health, but also to ensure “the microbiological and physico-chemical quality of water”, such as its mineral or trace element content, emphasizes ANSES .

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And who is in charge monitor and analyze the quality of our water? This mission is the responsibility of the Regional Health Agencies (ARS). “The ARS define the substances to be searched for in water and analyzed, depending on the populations and areas concerned”, explains to news.fr toxicologist Pauline Cervan .

For example, mountainous areas with little agriculture tend to have better water quality because less pesticide is used there.

Pauline Cervan Toxicologist

Regulatory values and health values

What exactly are we tracking in our water? “We find what we want to look for! “Slips Pauline Cervan . Residues of drugs , type pollutants heavy metals (like lead or cadmium), pesticide

To determine whether or not these substances are dangerous (in other words, “relevant” or “irrelevant”) for human health, the health authorities have defined maximum authorized thresholds, on the basis of “regulatory values”, measured in micrograms per liter (µg/L).

“When this threshold is exceeded, it means that the quality of the water distributed to the tap is deteriorating”, emphasizes ANSES . Should we expect the water to be shut off automatically if the regulatory value is exceeded?

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No, reassures Pauline Cervan . The quality of the water is reduced, of course, but the water remains consumable. “The distributor must do everything to limit this contamination and restore the quality of the water. »

Different actions can be taken depending on the context: increased protection of the resource, interconnections between different raw water resources, dilution, enhanced treatment of the water distributed.


What if I still drink my glass of water? “There is no immediate risk to health if we exceed the regulatory value, it is an indicator of water quality”, sums up the toxicologist. On the other hand, some substances are also classified according to health values which , as their name suggests, determine health risks.

One in five French people has consumed water that has exceeded its quality threshold

According to a survey by Le Monde and France 2, which cross-referenced huge public databases, 20% of the population in mainland France consumed water that would exceed the required quality thresholds in 2021, compared to 5.9% in 2020. These figures are expected to be confirmed by the Ministry of Health in December.

Metabolites, preferred targets

For years, pesticides and their metabolites are the preferred target of health authorities. More sought after, they are therefore more often detected.

“The metabolites come from the transformation of the active substance of the pesticide. Once spread in the fields and in the soil, the active substance degrades with the sun, the humidity… and it becomes the metabolite”, summarizes the specialist, also a member of the collective. Future Generations .

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In the case of its two reassessments at the end of September 2022, ANSES looked into the toxicity of metabolites S-metolachlor ESA And S-metolachlor NOA , from an active substance herbicide used since 2005, particularly in the cultivation of maize. “They are mainly found in Hauts-de-France and Brittany, because of the important cultivation of this cereal”, underlines Pauline Cervan .

A raised threshold that poses a problem

Until now, the regulatory value of the two metabolites, then considered “relevant”, was set at 0.1 µg/L. But since the end of September, ANSES has reconsidered the classification of these substances, finally considering that they were “not relevant” for health.

Consequently, their maximum authorized threshold has automatically increased from 0.1 µg/L to 0.9µg/L . In other words, the health authorities now tolerate a nine times higher concentration of these metabolites in the water, without this changing the quality or the dangerousness of the water. And this is where it gets stuck for associations and collectives.

Research on pesticides and metabolites in drinking water is more numerous in France. (©Jean-Paul BARBIER)

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“A loophole in the regulations”

The metabolites comply with regulatory thresholds, but do not have health values. This means that since the end of September, denounces Pauline Cervan , their level has been greatly increased on the basis of insufficient data concerning their dangerousness for human health.

The problem with metabolites is that when they are put on the market, their toxicity (carcinogenic, endocrine-disrupting, etc.) is not assessed over the long term. There is a loophole in the regulations. Raising the authorized thresholds of metabolites in water ultimately means exposing consumers to potentially dangerous substances.

Pauline Cervan Toxicologist

For its part, ANSES points out that the classification of a metabolite can change over time “thanks to the acquisition of new scientific knowledge relating to the criteria on the basis of which this classification is established”. “A metabolite can therefore go from a classification of relevant to irrelevant, and vice versa”, justifies the organization.

Over the past decade, sanitary control of the quality of water intended for human consumption has evolved in terms of the performance of analytical methods. In addition, more and more active substances and metabolites are being sought. Finally, the uses of plant protection products also change over time.


Nowadays, according to data from the National Institute for the Industrial Environment and Risks ( Ineris ), more than twenty pesticides or metabolites do not have health values.

Sources: https://actu.fr/planete/pollution/pesticides-dans-l-eau-du-robinet-pourquoi-les-seuils-des-autorites-sanitaires-inquietent_54589647.html