Radioactive contamination of mushrooms and wild game

Soil contamination with caesium-137 in Germany in 1986 (becquerels per square metre)

Mainly as a result of the Chornobyl reactor accident, certain species of mushrooms and wild game are still highly contaminated with caesium-137 in some areas of Germany. This applies especially to Southern Germany, which was particularly affected by the Chornobyl fallout in 1986 – in particular Southern Bavaria and the Bavarian Forest but also parts of Upper Swabia.

In the last years values of up to several thousand becquerel per kilogram were measured in wild game and certain edible mushrooms.

In Germany it is not permitted to market food with more than 600 becquerel caesium-137 per kilogram. However, this limit does not apply for private use. Mushroom pickers and hunters should therefore find out about their additional radiation exposure.

If wild game or wild growing mushrooms are consumed in usual amounts, the additional radiation exposure is comparatively low.

Those who wish to reduce their personal exposure should not excessively eat wild game self-hunted or mushrooms self-picked in the most affected areas of Germany.

These most affected regions (see map on soil contamination with caesium-137) include above all

• the Bavarian Forest and adjacent areas,
• the Donaumoos area southwest of Ingolstadt,
• the region around Mittenwald and
• the region Berchtesgadener Land.

Edible wild mushrooms

The level of contamination of edible wild mushrooms varies depending on the species and the place they grow.

Bay bolete (Imleria badia)

At the sampling areas examined by the BfS

• wood hedgehog (Hydnum repandum),
• terracotta hedgehog (Hydnum rufescens),
• ivory woodwax (Hygrophorus eburneus),
• larch woodwax (Hygrophorus lucorum),
• trumpet chanterelle (Cantharellus tubaeformis),
• bay bolete (Imleria badia),
• tawny grisette (Amanita fulva),
• blue spot knight (Tricholoma columbetta),
• blackening brittlegill (Russula nigricans) and
• Lepista glaucocana

reached activity levels of more than 1,000 becquerel per kilogram of caesium-137 in the last three years (2021 to 2023).

The contamination of mushrooms depends on both the caesium-137 level near the mycelium and the special accumulation capacity of the respective mushroom species. The contamination of a mushroom species is very site specific and varies even within the same area a lot more than from year to year. Further information can be found in the BfS report "Radioactive contamination of edible fungi: Current measured values" (in German, with English summary).

Wild game

Depending on the region and the animal species, the contamination level of wild game may differ substantially. In highly affected areas levels of caesium-137 in meat of wild boar are sporadically still exceeding tenfold and more the threshold for marketing of 600 becquerel per kilogram.

The peak values measured in a research project on the current contamination situation of wild boars in Germany were about 17,000 becquerel caesium-137 per kilogram in the Bavarian Forest during the sampling period from 2017 to 2020. Measurement data collected within the scope of the national measurement program (IMIS) in the period from 2020 to 2022 reached maximal levels

• of about 1,200 becquerel caesium-137 per kilogram for wild boars,
• of about 330 becquerel caesium-137 per kilogram for roe deer and
• of about 63 becquerel caesium-137 per kilogram for red deer.

In most cases, significantly lower levels were determined.

The strong differences between the various types of wild game are mainly due to the dietary behaviour of the individual animal species. Since the contamination of deer truffle, which grows below the surface and is fed on by wild boar, is extremely high (the values are more than ten times higher than those of edible mushrooms), meat of wild boar is clearly higher contaminated than the meat of other wild game species.

Contamination will decline over the medium-term

The fact that the contamination of food from forests may be significantly higher than that of agricultural products, is due to the diverse nature of forest soils and agriculturally used soils. While caesium-137 is easily available in the upper organic layers of forest soil, it is strongly bound to clay minerals present in arable soils, so that plants can hardly absorb it up via their roots.

Radiocaesium migrates very slowly into deeper layers of forest soils. As a result of this migration and of the radioactive decay, the activity concentrations in mushrooms and wild game will gradually decrease in the next years. An accurate forecast is only possible if the local soil contamination and the ecological conditions at the respective location are known.