Environment Lake Geneva drinking water safe despite pollutant, according to expert report
Despite elevated levels of the pollutant 1,2,4-triazole in drinking water from Lake Geneva, there is no danger according to an expert report. The report was commissioned by the cantons of Valais, Vaud and Geneva after the levels were above the reference value in the summer.
17.10.2025, 10:32
SDA
An adult would have to drink more than 900 liters of water a day to reach the theoretical threshold value above which a harmful effect can no longer be ruled out, as the cantons wrote in a joint statement on Friday. The expert assessment was carried out by the Swiss Center for Applied Human Toxicology (SCAHT).
According to the cantons, the experts saw no need to take strict or urgent regulatory measures to reduce 1,2,4-triazole levels.
1,2,4-Triazole is a component of pharmaceuticals and agrochemicals. It can also originate from the degradation of pesticides, biocides or medicines. The measured values are still above the federal reference value (0.1 μg/L), which was defined in the Drinking Water Ordinance.
Contaminated water is incinerated
According to the press release, the cantons want to continue monitoring the concentrations and reduce them below the reference value in the medium term.
In addition, the canton of Valais has demanded that the companies releasing this substance introduce measures and draw up a timetable to reduce discharges into the Rhone and Lake Geneva as far as possible.
The industry has therefore set up a task force of experts to carry out a thorough assessment of possible technical solutions. In the short term, the chemical company Syngenta wants to incinerate polluted water; in the longer term, processes such as carbon filtration or UV treatment are being tested.
