Agriculture pollutes our drinking water
There’s no doubt that those driving the initiatives are tackling a very real and serious problem – recent studies confirm widespread contamination of our groundwater by pesticides, particularly in agricultural areas in on the Swiss Plateau2. In fact, pesticide use in Swiss agriculture is even considerable by international standards, with more than 2,000 tons of pesticides being sprayed onto crops every year. Rain washes some of these chemicals into the groundwater, along with their transformation products, known as metabolites. In cool aquifers, degradation takes place slowly and so these chemicals accumulate. Certain pesticides, such as the herbicide atrazine, are detectable for decades, even if the substance has long been banned. Which is why the drinking water initiative3 is demanding that subsidies should only be paid out to farms that do not use synthetic pesticides.
The problem of metabolites
While not all pesticide metabolites are hazardous, research keeps identifying new risks. Some metabolites are more soluble in water and have a much longer life than the original substance. A good example here is chlorothalonil, a fungicide currently approved in this country for combatting fungal infections in vegetable and cereal cultivation. Yet as it may cause cancer, the European Food Safety Authority has recently stepped up its risk profile4. As a result, the EU Commission has not renewed authorisation, so the fungicide is to be banned in Switzerland too.
All this doesn’t solve the problem – for Swiss groundwater is already too heavily contaminated with metabolites of chlorothalonil. Karin Kiefer, a doctoral student at ETH Zurich, examined 31 groundwater samples at Eawag and detected a new transformation product of chlorothalonil in 20 cases5. On average, it was more than five times the threshold value, with the highest concentration some 27 times higher. The affected water catchments should now be treated within a month – but given the extent of pollution in arable farming areas and the dearth of purification techniques, this will hardly be possible.
A comprimise is urgently needed
Clean drinking water is a priceless commodity. If we want to keep drinking water safe in Switzerland in the long term, we must cut the use of hazardous pesticides in agricultural areas as quickly as possible. In 2017, the Federal Council accordingly adopted an action plan for reducing pesticides6 based on a comprehensive risk analysis. To date, however, the plan is no more binding than the Federal Council’s recently published intention to “examine” possible legal bases for protection from pesticide pollution in the context of agricultural policy from 2022 on.