To provide an overview, researchers from ZHAW and ETH Zurich, on behalf of the Federal Office for the Environment (FOEN), compiled and analyzed 1070 PFAS soil measurements. The evaluation shows that PFAS are detectable in over 99 percent of soil samples. Elevated levels are found in areas with suspected use of fire-fighting foam or sewage sludge. The measurements come from cantonal investigations and the National Soil Monitoring.
The median PFAS content stands at 2.4 micrograms per kilogram, surpassing the median of 1.4 micrograms per kilogram from the ZHAW study in 2022. The difference can be explained methodologically: while the 2022 study depicted the baseline contamination of Swiss soils, the new evaluation also includes measurements from cantonal investigations of urban soils or suspected areas. 'The evaluation paints a more comprehensive picture of the contamination situation of Swiss soils and emphasizes that PFAS are present throughout the soils,' says ZHAW expert Basilius Thalmann, co-author of the study.
Hotspots for Fire-fighting Foam and Sewage Sludge
The investigation confirms that areas with specific sources such as the use of fire-fighting foam exhibit significantly higher concentrations compared to forest areas or grassland in mountainous regions. The application of sewage sludge is also considered a risk factor for increased contamination. However, there are also sites where sewage sludge was applied that did not show elevated levels.
The results represent a significant expansion of the knowledge on the contamination situation in Swiss soils. 'We are not surprised by the results, but we consider them worrisome. They provide an important basis for decision-making in execution by the federal government and cantons,' Thalmann says.
Downloads and Further Information
Original publication: Glüge J., Rudin E., Thalmann B., Scheringer M. (2026). PFAS Concentrations in Swiss Soils – An Overview. On behalf of FOEN.
Swiss soils investigated for environmentally harmful PFAS for the first time, press release from January 4, 2023.
Invisible Threat: PFAS in Swiss Pastures, feature on the 3Sat program nano from February 10, 2026.
What are PFAS? Per- and polyfluorinated alkyl substances (PFAS) are a group of thousands of synthetic chemicals. They are water-, grease-, and dirt-repellent and very stable. As they hardly decompose in the environment, they are often referred to as 'forever chemicals.'
Contact
Basilius Thalmann, Lecturer, Research Group Soil Ecology, ZHAW Institute for Environment and Natural Resources, Department Life Sciences and Facility Management, +41 58 934 52 89, basilius.thalmann@zhaw.ch
Elvira Rudin, Doctoral Student, Research Group Soil Ecology, ZHAW Institute for Environment and Natural Resources, Department Life Sciences and Facility Management; Research Group Environmental Chemistry, Institute for Biogeochemistry and Pollutant Dynamics ETH Zurich, +41 44 632 78 66, elvira.rudin@usys.ethz.ch
Beatrice Huber, Media Relations ZHAW Department Life Sciences and Facility Management, +41 58 934 53 66, beatrice.huber@zhaw.ch
ZHAW Media Office, +41 58 934 75 75, medien@zhaw.ch