Swiss Review 2/2021

Swiss Review / April 2021 / No.2 7 A subterranean aquatic temple – the Lyren drinking water reservoir in Zurich- Altstetten. Photo: Keystone Groundwater is at itsmost abundant under the valley fl oors and fertile plains of the Central Plateau – the ep- icentre of Swiss vegetable and cereal cultivation. Pesticides have been used for decades in this intensively farmed region, and not without con- troversy. The latest furore surrounds the fungicide chlorothalonil – an ac- tive ingredient in crop protection products used on farmland since the 1970s to prevent fungus. Chlorothalonil was banned at the end of 2019, a ft er the federal govern- ment determined that the substance had a potentially damaging e ff ect on health. Manufacturer Syngenta vehe- mently disputes the assertion that the substance is probably carcino- genic. The agrochemical company took legal action forcing the Federal O ffi ce for Agriculture to remove this claim from its website until the Fed- eral Supreme Court had given its de- fi nitive judgement on the ma tt er. However, the chlorothalonil ban is not the end of the problem, be- cause by-products of the fungicide, known asmetabolites, will continue to pollute the groundwater for years to come. The maximum legal value for toxicologically relevant sub- stances such as these in Swiss drink- ing water is 0.1 micrograms per litre. Yet this limit is exceeded in inten- sively farmed parts of the Central Plateau, such as the canton of Solo- thurn: “There are excessmetabolites in nearly all water catchments situ- ated in the valley plains – up to 20 times higher than the maximum ac- ceptable limit in some cases,” says Martin Würsten, the former head of Solothurn’s environmental o ffi ce. Since retiring, Würsten has been playing an active role in 4aqua – a group comprising dozens of experts and scientists who, in their own words, wish to givewater a “political voice grounded in facts”. One million inhabitants affected Würsten believes this voice has not been given enough a tt ention in re- cent decades. “While we have made leaps and bounds inwaste water pu- ri fi cation, we have hardlymade any progress in reducing the signi fi cant levels of water pollution caused by agriculture over the past 20 years,” he says. Würsten is also concerned that nowhere near all pesticides used on fi elds have been studied as closely as chlorothalonil was re- cently. In his view, “Something may not be seen as a health risk today, but it could well be in future”. This is why 4aqua wants the approval of synthetic pesticides to be subject to greater transparency and scrutiny. Some 370 substances are currently in use in Switzerland. Higher-than-recommended lev- els of pesticide have been found in the drinking water supplies of around one million people in the Central Plateau region. The govern- ment has given drinking water sup- pliers a two-year deadline to bring chlorothalonil levels below the per-