In 2022, the Canton of Zurich tested the surroundings of waste incineration plants for dioxins and published the results in November. The sample from the Josefwiese was within the range of the legal test value of 20 nanograms of toxicity equivalent per kilogram (ng TEQ/kg). Based on this result, City Councilor Simone Brander, head of the Department of Civil Engineering and Waste Management, commissioned an in-depth investigation. In cooperation with the cantonal Office for Soil Protection, soil samples were taken from nine unpaved areas of the Josefwiese and analyzed at Empa.

Empa chemist Markus Zennegg provides information on the measurements after the city's press conference. Image: City of Zurich

The new samples from the meadow area were below the test value of 20 ng TEQ/kg. However, analyses on certain other areas showed values of up to 48 ng TEQ/kg in the top soil layer. These values are well below the decontamination value of 100 ng TEQ/kg. However, in case of repeated contact with the contaminated soil, a health risk cannot be ruled out. The use of the affected areas must therefore be restricted for children under six years of age as a precautionary measure in accordance with legal requirements. The city has thus decided to clean up the affected parts of the Josefwiese. In total, an area of 6000 m² of the approximately 21,000 m² site will be decontaminated.

Markus Zennegg, a chemist at Empa's Advanced Analytical Technologies laboratory, led the sample analysis and considers the city's approach appropriate. "In principle, all people are exposed to a certain level of dioxins through their food intake. This exposure should, however, not be increased further by the possible ingestion of contaminated soil, especially in young children." By covering the affected areas and then decontaminating them, this goal can be achieved, Zennegg said.

To the press release of the City of Zurich (in German)