Groundwater quality

Groundwater does not naturally contain any persistent synthetic substances. Nitrate and residues of plant protection products have a long-lasting adverse impact on groundwater quality. Along watercourses, micropollutants from industry, commerce and households are also found in groundwater.


Nitrate exceeds the limit value of 25 mg/l in groundwater at 18% of monitoring sites across Switzerland. In areas where arable farming is predominant, concentrations are now above the limit at more than 50% of monitoring sites.


Pesticides exceed the limit value of 0.1 micrograms per litre at around 2% of monitoring sites every year. In addition, pesticide degradation products (known as metabolites) occur in concentrations of more than 0.1 micrograms per litre at one in three groundwater monitoring sites across Switzerland. Metabolites significantly impair the quality of groundwater, particularly on the Swiss Plateau.

Volatile organic compounds

Volatile halogenated hydrocarbons are the most frequently detected volatile organic compounds (VOC) in groundwater, exceeding the limit value at 3% of monitoring sites. In contrast, monocyclic aromatic hydrocarbons (MAH) and polycyclic aromatic hydrocarbons (PAH) are only rarely found.


Pharmaceuticals occur in groundwater at around 15% of the monitoring sites throughout Switzerland. Groundwater resources in unconsolidated aquifers next to rivers are the most affected. The pharmaceuticals enter rivers and streams via sewers and sewage treatment plants, and finally infiltrate into groundwater.


Per- and polyfluoroalkyl substances (PFAS) are found in Swiss groundwater at almost half of the NAQUA monitoring sites. PFAS concentrations exceeding 0.1 micrograms per litre in groundwater are frequently due to the use of firefighting foams containing PFAS. These chemicals can also reach groundwater from landfill sites or via infiltration of river water.

Further information


Last modification 12.10.2023

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