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The Zurich authorities have given the go-ahead: most drinking water meets the strictest requirements. In contrast, groundwater is contaminated in many places by chlorothalonil metabolites.
The maximum value is nowhere exceeded in the water of the city of Zurich.
Here one community is drawing a well from the mains, there another buys drinking water from the neighboring village and feeds it for its own supply: these reports have been widely read in recent months, including in the canton of Zurich. The background in many cases was the same: the new evaluation of the pesticide chlorothalonil.
This fungicide has also been used in Switzerland since the 1970s, especially in agriculture. However, in the spring of 2019, the European Food Safety Authority found indications of a health hazard due to the degradation of the plant protection product. As a result, the federal government banned its use, and the Federal Office for Food and Veterinary Safety posted a warning on its website, against which the Syngenta chemical company filed a lawsuit and recently won a court case.
Adoption of the new assessment had far-reaching consequences: Suddenly, a new maximum value of 0.1 micrograms per liter is applied to degradation products, which experts say is at the limit of what can be measured . Cantonal chemist Martin Brunner told a news conference Tuesday that the alleged toxicity of the substances can now be discussed for a long time. According to the precautionary principle system, this is the value by which one has to orient oneself.
A unique measurement campaign to date
The Zurich event served to present the results of the measurements that have been carried out throughout the canton during the last twelve months. For the first time, they make it possible to obtain a complete picture of the contamination of Zurich’s groundwater and drinking water, which is based on data on a degradation substance called R471811. Not because it’s particularly toxic, as Brunner said. However, it is the metabolite that occurs in the highest concentration and therefore causes more problems to meet the maximum values. According to Brunner, it was the first time that Zurich water had been tested so extensively because an active ingredient was evaluated differently.
The main message of the press conference was: You can still enjoy Zurich’s “Hahnenburgers” without hesitation. The drinking water in the canton is of “good quality,” said government councilor Natalie Rickli (svp.), Whose health department is affiliated with the cantonal laboratory.
In the case of groundwater, on the other hand, the situation is different, as shown by measurement data from a representative selection of 100 locations in the most important groundwater resources. The maximum value has been exceeded at around 60 percent of the measurement points, with the highest concentrations measured in Zürcher Unterland, in the region around Winterthur and in the wine region.
In view of these numbers, nothing can be done, said building director Martin Neukom (gp.), Who is also responsible for the environment and agriculture in Zurich. The sale of protective agents containing chlorothalonil is now prohibited. In light of the other pesticides used in agriculture, gardens, or construction, Neukom advocated for greater prevention. The government of Zurich expressly welcomes the federal government’s pesticide action plan and the movement in the federal parliament for a binding reduction path.
Neukom’s construction department itself only has relatively little leverage. The building manager mentioned, for example, a project to use precision agriculture in a more targeted way to reduce the amount required, or to control washing stations and sprinklers on farms. Its strategy also includes the revitalization of rivers and streams. This facilitates the regeneration of the water and improves the quality.
Many churches acted quickly
There are two main reasons why the overall picture of drinking water is different from that of groundwater: First, the tap water in the city of Zurich and many lakeside communities comes from Lake Zurich, which is considered ” clean “, and the city of Winterthur gets it from the Tösstal. In addition, several municipal utilities have mixed spring and ground water. Therefore, the results of groundwater samples cannot be transferred one by one to drinking water.
Second, the hardest hit communities reacted quickly after the alarming initial findings and adjusted their supply networks to continue supplying clean water to their customers. For example, closing a pumping station or drawing water from another network. This has now led to the result presented on Tuesday: 80 percent of Zurich’s population lets out their tap water, which also meets the strictest legal requirements, with 20 percent exceeding the maximum value. This is particularly the case in the municipalities of the lowlands and the northeast of the canton. Two municipalities only achieved a value of less than 1 microgram per liter in August, ten times the current maximum.
This is how polluted the drinking water is in Zurich
Appearance of the degradation product of chlorothalonil R471811
Communities with contaminated water face a difficult task, because there is often no solution available overnight and it can also cost money. For example, dilution is only possible with large amounts of other water and only in a large reservoir, said cantonal chemist Brunner. These may not be the correct dimensions or may be in the wrong location. “It takes a lot of creativity and experience to reduce concentration.”
When opening a new water intake, according to Brunner, it is important to ensure that a municipality does not face any new problems, for example with fecal germs. It would also be possible to build new connection lines to other water supplies. But this is often time-consuming and expensive, Brunner said. Groundwater treatment is not a viable option for him as it is not technically feasible. He also believes that society has failed when it has to treat groundwater in order to drink it.
The cantonal laboratory and municipalities will continue to monitor the situation, according to the cantonal chemist. The proportionality aspect of the measures will also be discussed, he said. It’s about the question of how much something should cost and in what time it should be built. Previously, municipalities had to implement a measure within two years. This time frame can be extended in accordance with the latest federal instructions.
Farmers warn against scare tactics
The water quality findings have sparked various reactions. The Zurich Farmers Association warns against scare tactics, outlines legal procedures for approval of chlorothalonil and numerous open questions about the dangerousness of the substance. He also criticized the media for their panic and fear tactics and for portraying farmers as the only culprits. However, they only used a medium that the authorities had classified as harmless for decades.
Green liberals are calling for greater protection and better gripping of groundwater, as well as testing of all agricultural fertilizers that have been approved for more than twenty years. The Greens describe the groundwater findings as “alarming.” They expect the federal government and the canton to control the approval and use of pesticides more strictly.
An active ingredient against many fungi.
where. · Chlorothalonil (also chlorthalonil or tetrachloroisophthalonitrile) is an organic compound made up of eight carbon atoms, four chlorine and two nitrogen atoms that acts as a fungicide: the substance kills a whole range of fungi that can be dangerous to plants. In Switzerland, therefore, it was used since the 1970s to protect herbaceous crops such as cereals or potatoes, but also tomatoes, vines, and ornamental plants from various fungal diseases. The active ingredient was one of the best-selling phytosanitary ingredients in Switzerland.
According to the European Chemicals Agency (Echa), chlorothalonil is suspected of being carcinogenic. In rats and mice, according to a report by the European Food Safety Authority (Efsa) on chlorothalonil, both benign and malignant tumors were observed in the kidneys (as well as in a special part of the stomach) in experiments in which the animals were exposed to the substance for a short or long period. rodents that humans do not possess).
According to the Federal Office for Food and Veterinary Safety (FSVO), both FSVO and Efsa have not been able to rule out a health hazard from certain breakdown products of chlorothalonil in their risk assessments.
As of January 1, 2020, the active ingredient can no longer be used in Switzerland; The use of chlorothalonil is also not allowed in the EU.
