Canton of Zurich – Measurements: Too much chlorothalonil residues in groundwater – News

• Over the past twelve months, Zurich has tested its groundwater and drinking water for residues of the pesticide chlorothalonil.
• In the case of groundwater, waste exceeds the prescribed maximum value in many places.
• The building manager, Martin Neukom, sees the need for action.

First of all clear: depending on the canton, anyone who wants to drink water in the canton of Zurich can do so without hesitation. “We have very good quality drinking water,” says Natalie Rickli. Measurements show that 20 percent of drinking water contains too much chlorothalonil residue: the maximum value of 0.1 micrograms per liter is exceeded.

What is chlorothalonil?

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Chlorothalonil has been used as a fungicide in agriculture since the 1970s. The active ingredient protects grains, vegetables, and vines from fungal attack. The pesticide was also used on lawns, flowers, shrubs, and ornamental plants.

The European Food Safety Authority evaluates the fungicide as “probably carcinogenic”. Therefore, the use of chlorothalonil has been banned in Switzerland since the beginning of 2020.

However, this legal maximum is very low, according to Zurich health director Natalie Rickli. Water, which slightly exceeds the value, is not harmful to health. However, measures are necessary: ​​for example, affected communities improve their drinking water by adding clean water.

Unlike drinking water, 60 percent of samples taken from groundwater exceed the limit value. According to the responsible building manager, Martin Neukom, the values ​​are questionable and clearly too high. “In my opinion, the big alarm is clearly wrong,” says Neukom. “To say that we do nothing, but it would not be appropriate”

However, the canton can only act preventively with regard to the protection of groundwater. Because sometimes pesticide residues remain in groundwater for decades, even if a pesticide is no longer used.
“That is why it is so important that these substances do not even get into the environment,” says Neukom. That is why the canton supports a project that aims to reduce the use of pesticides in agriculture.