A recent study found excessive levels of nitrates in 15% to 20% of underground water samples in Switzerland, according to the Federal Office for the Environment (FOEN).
Underground water is the source of most of Switzerland’s (80%) drinking water.
The data was collected at 600 water testing sites between 2007 and 2017. In 2014, 15% of samples had nitrate levels exceeding the 25 mg/l limit set out in regulations protecting water quality. In 2017, 12% of samples exceed the limit. Results by testing station can be seen here.
Nitrates can react with certain compounds in the stomach to form compounds that have been found to be carcinogenic in animal tests, according the the World Health Organisation (WHO). High levels of nitrates are also associated with other health conditions.
In addition to high levels of nitrates, over half the samples contained pesticide residues. Much of the pollution comes from agriculture, particularly on Switzerland’s highly populated plateau where there is much intensive farming. In these regions, 40% of samples also had excessive nitrate levels.
Atrazine, an agrochemical banned more than 10 years ago was found in some samples.
Jacques Bourgeois, director of the Swiss farmers union, told RTS that new measures to control the use of pesticides were introduced in 2017 after these samples were taken. These measures reduced the use of phytosanitary products by 27%, he said.
Bourgeois called on cantons to finish the job of creating protected water catchment zones.
The FOEN report concluded by stating that Swiss underground water continues to provide outstanding drinking water in sufficient quantities.