The Chernobyl reactor catastrophe casts a long shadow: In some regions of southern Germany, certain wild mushroom species can still be contaminated with radioactive cesium-137 above the limit value. This emerges from a current report by the Federal Office for Radiation Protection, which summarizes the test results from 2019 to 2021. It shows in detail where increased values are to be expected, which types of mushrooms are particularly affected and what contamination can occur after eating them.
Especially in September and October, many people like to be out and about with a basket in forests and meadows in search of delicious additions to the menu: the mushroom season is at its peak. But how did the radioactive contamination of the mushrooms actually develop? Above all, anyone who can personally remember the year 1986 knows that as a result of the Chernobyl reactor catastrophe, radioactive plumes reached Germany and polluted the environment. At that time, it was warned that wild mushrooms in particular could collect serious amounts of radioactive substances in their fruiting bodies. The persistent strain continued to be reported in the decades that followed. It is due to the radioactive cesium-137, which has a half-life of 30 years.
Still glowing mushrooms
The Federal Office for Radiation Protection in Salzgitter (BfS) is now providing information about the last recorded values. The mushroom report includes the test results for the years 2019 to 2021. Numerous wild-growing edible mushroom species in different regions were analyzed. As the BfS explains, the contamination of fungi depends both on the cesium-137 content in the area surrounding the fungal network (mycelium) in the soil and on the special accumulation capacity of the respective fungus species. "Anyone who now wants to collect mushrooms for their own consumption can use the current mushroom report from the Federal Office for Radiation Protection for orientation," says BfS President Inge Paulini.
The report shows that wild mushrooms are still in some cases significantly exceeding the limit that applies to mushrooms on the market. It is 600 becquerels of cesium-137 per kilogram of fresh mass. With some wild mushrooms, on the other hand, it reaches over 4000 becquerels. Mushrooms from the areas of Germany that were particularly affected by fallout after the reactor accident are most heavily contaminated. "In these areas - such as the Bavarian Forest, the edge of the Alps and the Donaumoos south-west of Ingolstadt - you should only consume mushrooms you have collected yourself in moderation to avoid unnecessary exposure to radiation," advises Paulini.
Varies greatly depending on the species
Bread stubble mushrooms were the bright frontrunners with 4000 becquerels of cesium-137 per kilogram of fresh mass during the period under study. These are edible mushrooms popular with mushroom connoisseurs, some of which are often found in forests. Other frequently collected species, such as trumpet chanterelles, chestnut boletes or various types of snails, reached 1000 becquerels per kilogram. However, there are also mushrooms with extremely low levels of contamination: fewer than ten becquerels per kilogram were found in some wild mushroom species, the ink cap and the honey honey fungus. The long list of harmless species is listed in the report.
In addition to the cesium-137 content of the mushrooms, the amount consumed is of course decisive for the radiation exposure of humans, emphasizes the BfS. If wild-growing edible mushrooms are consumed in the usual quantities, the additional radiation exposure is comparatively low. Nevertheless, it is worth avoiding particularly highly contaminated types of mushrooms if you regularly eat mushrooms you have collected yourself: an adult who eats a meal of 200 grams of mushrooms with 2000 becquerels of cesium-137 per kilogram every week experiences an additional annual radiation dose of 0, 27 millisieverts. This corresponds to a load that would occur with around 20 flights from Frankfurt to Gran Canaria. "However, it is ultimately a personal decision which additional radiation exposure is considered acceptable through the consumption of self-collected mushrooms," writes the BfS.