Five rivers in Switzerland’s central plateau region are heavily polluted in spring and summer by a cocktail of different pesticides, of which a third are problematic and exceed official limits, according to a study commissioned by the government.
Researchers from the Federal Institute of Aquatic Science and Technology identified 104 different pesticides in water samples taken between March and July 2012 from medium-sized rivers that cross five cantons: Menthue (Vaud), Salmsacher Aach (St Gallen), Furtbach (Zurich), Surb (Aargau) and Limpach (Solothurn).
The accumulated concentration of chemical substances exceeded one milligram per litre in 78% of samples. The institute said about 40 of the pesticides identified are «problematic» as they exceed the maximum concentrations stipulated in water protection laws.
Juliane Hollender, head of the institute’s environmental chemistry department and co-author of the study, said she was surprised by the results. «Swiss waters do not seem to be as clean as people like to keep stressing.»
She said the concentration of substances was certainly problematic, but it was especially important to evaluate properly the toxicity of the pesticide cocktails found in the rivers.
Although it was not possible to draw conclusions on the overall quality of the water, the authors of the study, published in the Aqua&Gas review, expressed concerns about the impact of the pesticides on aquatic life.