Pesticides and tap water
In 2023, a national Anses campaign revealed that a residue of chlorothalonil, a banned fungicide, was present in more than one in two drinking water samples in France. Since then, the regulatory situation has changed. Here is what the official sources say, and what our laboratory reports establish.
1 in 2
samples contained the metabolite R471811 during the Anses campaign
1 in 3
exceeded the 0.1 µg/L limit then applicable to this metabolite
≈ 20%
of the water distributed in France covered by the abstraction points analysed
0.9 µg/L
new reference value for R471811 since the Anses opinion of April 2024
Sources: Anses campaign report published on 6 April 2023, Anses opinion of 29 April 2024.
Background
A banned fungicide that leaves traces
Chlorothalonil is a fungicide marketed by Syngenta and long used on cereals. In France, 1,710 tonnes were sold in 2016.
In April 2019, the European Commission refused to renew its authorisation through Implementing Regulation 2019/677. It considered that harmful effects of the chlorothalonil metabolites found in groundwater could not be ruled out. France allowed a period for existing stocks to be used up until May 2020.
When it comes to health classification, the nuance matters. Chlorothalonil is officially classified as a category 2 carcinogen (suspected effect) in the European Union. In its 2018 assessment, the European Food Safety Authority (EFSA) proposed category 1B (presumed carcinogen). This classification concerns the parent molecule, not automatically its breakdown products.
The current problem comes precisely from these breakdown products, known as metabolites. They form in the soil and then migrate into groundwater, and some remain there for years after the ban. Switzerland was the first to detect them, in 2019. These data prompted Anses to look for them in France.
Reading the figures correctly
A third of samples, not a third of the French population
The figure most widely reported in the media comes from the Anses campaign carried out from 2020 to 2022 on more than 136,000 analysis results. The metabolite R471811 appears in more than one sample in two, and exceeds the quality limit in more than one sample in three.
What this figure does not say. It relates to samples chosen to represent about 20% of the water distributed. It does not mean that a third or half of the population drinks affected water. An exploratory campaign looks for substances that are rarely monitored; it does not measure the exposure of each household.
The maximum concentrations recorded reached 2 µg/L. At the time, the transitional health value set by the Ministry of Health was 3 µg/L, as the government's answer to the National Assembly points out.
What has changed
April 2024: two metabolites, two statuses
In 2021, Anses had classified R471811 as relevant as a precaution, for lack of sufficient data. This status imposes the quality limit of 0.1 µg/L. On 29 April 2024, the agency revised its position in a new opinion.
Metabolite R471811
Reclassified as non-relevant
The 0.1 µg/L limit no longer applies. It now falls under an indicative value of 0.9 µg/L. As early as 2022, Anses considered it neither mutagenic nor genotoxic.
Metabolite R417888
Classified as relevant
The 0.1 µg/L limit applies. Pending a definitive health value, a transitional value of 3 µg/L serves as a benchmark. The campaign found it above 0.1 µg/L in about 3% of samples.
Direct consequence: water declared non-compliant in 2023 because of R471811 has no longer been non-compliant since April 2024. The ARS Hauts-de-France regional health agency explains this change in detail, and several prefectures repealed their derogation orders as a result.
Also worth bearing in mind: the 0.1 µg/L limit is not a toxicity threshold. The Ministry of Health describes it as an indicator of the deterioration of the water resource, with no health significance in itself. Whether water remains drinkable is determined by a different value, set substance by substance.
The current situation
Pesticides in water remain a real issue
The reclassification of R471811 does not settle the question of pesticides in tap water. According to the Ministry of Health's answer to the Senate published in September 2025, 74.7% of the population received water that was continuously compliant for pesticides and their metabolites in 2023. This rate was 84.6% in 2022.
The ministry specifies that most of these exceedances remain limited in concentration or duration. Only 7 situations led to restrictions on the use of water for drinking in 2023. The drop is also explained by broader monitoring than before.
In April 2025, three ministries published a roadmap to better protect water abstraction areas. The detailed figures are given in the Ministry of Health's 2024 national pesticides report.
Water treatment
Why these metabolites are hard to treat
R471811 is a highly soluble molecule that moves very easily in water. That is what makes it hard to retain, including in treatment plants.
A study by Eawag and EPFL published in 2020 compared several treatments. In treatment plants, activated carbon retains R471811 but quickly becomes saturated and has to be renewed often. Reverse osmosis removed all the metabolites tested by at least 98%.
The pilot trials by the City of Lausanne confirm that R417888 is retained more easily on activated carbon than R471811. Eawag summarises these results in a dedicated fact sheet.
Our laboratory reports
What our tests establish on chlorothalonil
Phoenix Gravity
Our current filters. Report RaYnu 2510041B (2025) measures a reduction of more than 99% for the pesticides and herbicides tested, with outlet concentrations below 0.001 µg/L.
The previous generation. Envirotek report 14-260 measures chlorothalonil: 50.2 µg/L at the inlet, less than 0.5 µg/L at the outlet, i.e. a reduction of more than 99.9%.
These results relate to the parent molecule. The metabolites R471811 and R417888 do not appear in our published reports. We therefore do not give any reduction rate for these two molecules.
Each report states the concentrations measured, the volumes tested and its limitations. A result applies to a specific substance, under the test conditions.
In practice
Get to know your water in three steps
Check your municipality's test results
The results of official health monitoring are public. On the Ministry of Health's drinking water quality page, choose your region, then your department, your municipality and your network. Look for the lines chlorothalonil R471811 and R417888.
Read your network's annual summary
Every year, the ARS (regional health agency) writes a note on the quality of the water distributed, which is enclosed with your bill. You can also find it on the infofacture map.
Compare with the contaminants tested
Set the substances measured in your area against those covered by the Phoenix Gravity reports. The raw data are also freely available on data.gouv.fr.
Key points
- Chlorothalonil has been banned in France since 2020, but its metabolites persist in some groundwater.
- The one-third figure relates to samples from an exploratory campaign, not to the whole population.
- Since April 2024, R471811 has been classified as non-relevant. R417888 remains subject to the 0.1 µg/L limit.
- Our reports cover the chlorothalonil parent molecule, not its metabolites.
- Your municipality's test results remain the best starting point.
Frequently asked questions
Your questions about chlorothalonil
Is tap water still safe to drink?
In the vast majority of cases, yes. The health authorities distinguish between the quality limit, which signals deterioration of the water resource, and the health value, which determines whether the water can be drunk. In 2023, only 7 situations led to restrictions on drinking because of pesticides.
What is the difference between chlorothalonil and its metabolites?
Chlorothalonil is the substance sprayed on crops. In the soil, it breaks down into several different molecules, the metabolites. They do not have the same properties, the same toxicity or the same behaviour when it comes to filtration.
Why write more than 99% rather than 100%?
A laboratory measures down to a given limit. An outlet concentration below this limit means that it is below the measurable threshold, not that it is zero.
Why is the Black Berkey® no longer available?
Its withdrawal stems from a regulatory dispute in the United States. The US Environmental Protection Agency (EPA) reclassified the filter as a pesticide product because of the silver used in its filter media. The Phoenix Gravity New Millennium Edition™ elements have taken over. They are compatible with Berkey® systems and have their own reports, which you can view on the Phoenix tests page. The historical Black Berkey reports remain available on the dedicated page.
Sources
- Anses: Emerging pollutants in drinking water, results of the latest national campaign (April 2023)
- Anses: Full report of the national occurrence campaign for emerging compounds
- Anses: Opinion of 29 April 2024 on the metabolites R417888 and R471811
- ARS Hauts-de-France: Chlorothalonil metabolites
- French Senate: Ministry of Health's answer on emerging pollutants (September 2025)
- French Ministry of Health: 2024 report on tap water quality with regard to pesticides
- Implementing Regulation (EU) 2019/677 on the non-renewal of chlorothalonil
- EFSA: Peer review of the active substance chlorothalonil (2018)
- EPFL, Eawag: Removal of chlorothalonil metabolites in drinking water treatment (2020)
- Eawag: Fact sheet on chlorothalonil metabolites
- City of Lausanne: Results of the chlorothalonil treatment pilot trials (2023)
- RaYnu: Report 2510041B, pesticides and herbicides, Phoenix Gravity (2025)
- Envirotek Laboratories: Report 14-260, Black Berkey elements (2014)
- French Ministry of Health: Drinking water quality, results by municipality