Radioactive contamination of fungi – Cesium 137 Radiation exposure of chestnut boletus, chanterelle mushrooms and cards

The increased radioactivity of fungi has been known since the global nuclear weapon fallout and was extensively investigated after the Chernobyl reactor accident. In Europe, due to the half-life of around 30 years, the radiation exposure of forest mushrooms is now largely caused by cesium 137.
Undisturbed forest soils form a sink for many substances. Due to the special dynamics of forest soils, radiocesium and other pollutants often remain in the humus layer or in the uppermost mineral soil layers. It is precisely in these soil layers that the mycelia of many fungi are located and from here supply their aboveground fruit bodies with nutrients. It is therefore not surprising that they accumulate radionuclides. And the radiation exposure of humans caused by radioactivity from mushrooms will remain an issue

The main results are:
The regional cesium-137 deposition by the Chernobyl fallout and thus the level of the Cs-137 contamination of the soil plays an important role for the level of radioactivity of the fungi
The location conditions (soil type, pH value, soil moisture, etc.) are a major influencing factor
Fungi accumulate Cs-137 species-specifically (genetically determined ability to accumulate)
The cesium-137 measured values ​​fluctuate considerably in small locations even with the same species (up to a factor of 10)

Cesium 137 readings ​​on the radiation exposure of fungi from Germany

The radioactivity of mushrooms, in particular the edible mushrooms consumed by the population, is regularly checked on a random basis and measured values ​​are published. Measurements are carried out on behalf of federal authorities and also state institutions. Due to the increased cesium-137 deposition caused by the Chernobyl fallout in the federal states of Baden-Württemberg and Bavaria, the relevant state offices are increasingly examining samples of fungi for radioactive contamination. For example the Bavarian State Office for the Environment.

Umweltanalysen.com has investigated the radioactive contamination of fungi in several research projects commissioned by the BMU since 1986. The research projects were mainly carried out in areas of southern Germany that are particularly affected by the Chernobyl fallout. In addition, our own investigations were carried out.

In some regions of Germany particularly affected by the Chernobyl fallout, especially in southern Germany, cesium 137 contamination over 600 Bq / kg fresh weight can occur occasionally or regularly in some types of fungus.

Own research

In 2018, some mushroom samples were taken in an area of the Bavarian Forest National Park. The area is one of the areas most heavily contaminated by the Chernobyl fallout in Germany. The cesium-137 and potassium-40 activity measurements of the fungus samples were carried out at the laboratory for radioisotopes of the Georg-August-Universität Göttingen. The measurement error was <10%. The results are given in Table 1.

Tab. 1: Cesium-137 activity of chestnuts and porcini mushrooms from the Bavarian Forest National Park. Date of discovery 18.09.2018

Fund date	Species	Species	Cs-137 [Bq/kg FW]	Cs-137 [Bq/kg DW]
18.09.2018	Chestnut boletus	Imleria badia	2924	28660
18.09.2018	Chestnut boletus	Imleria badia	2983	30520
18.09.2018	Chestnut boletus	Imleria badia	1612	21250
18.09.2018	Chestnut boletus	Imleria badia	1011	8364
18.09.2018	Boletus	Boletus edulis	659	5376
18.09.2018	Boletus	Boletus edulis	651	6235
18.09.2018	Boletus	Boletus edulis	560	5384

The Cesiums 137 activity is given based on fresh weight (FW) and dry weight (DW). The species-typical differences in the Cs-137 contamination between chestnuts and boletus are clearly visible.
We investigated the correlation of the cesium 137 activity in the soil with the mycelium occurrence of different types of fungi by means of DNA sequencing.

Radioactivity in chestnut boletus, chestnut bolete – Imleria badia (Syn.Xerocomus badius, Boletus badius)

The chestnut boletus, belonging to the boletaceae, are popular edible mushrooms. The chestnut boletus is widespread all over Europe, with a focus on coniferous forests. The Röhrling occurs almost everywhere in Germany, likes to grow in acidic locations and is, for example, a mushroom popular with mushroom collectors in the Bavarian Forest.

Many older mushroom pickers are still familiar with the scientific species name Xerocomus badius. However, molecular biological, genetic and morphological analyzes had shown that the Xerocomus badius does not belong to the Xerocomus group, Gelari et al. (2013), Šutaras (2008). Vizzini renamed the species Imleria badia in 2014 after creating the genus Imleria. Vizzini named the generic name Imleria in honor of the Belgian mycologist Louis Imler (1900-1993).
The mycelium of the chestnut boletus is classified as a long distance exploration type (Agerer 1990).

Chestnut boletus are one of the types of mushrooms that accumulate cesium 137 particularly strongly. From the 2018 mushroom report, the BfS gives 150 and 85 Bq / kg fresh weight for Freising, 150 Bq / kg for Siegenburg, 510 Bq / kg for Aufham / Högl, 400 Bq / kg and 39 Bq / kg.

In the long term, the radiation exposure of chestnut boletus (Imleria badia) due to radiocesium decreases. Figure 01 shows the time course of the contamination for Lower Saxony. The decrease in cesium 137 activity since 1986 and the higher exposure compared to boletus and honey fungus can be clearly seen.

Literature

Agerer R., Gronbach E., 1990: Xerocomus badius. In Agerer R (ed) Colour Atlas of Ectomycorrhizae, plate 49, Einhorn-Verlag, Schwäbisch Gmünd.

Aumann, D. C., Clooth, G., , Steffen, B., Steglich, W., 1989:, Komplexierung von Caesium-137 durch die Hutfarbstoffe des Maronenröhrlings (Xerocomus badius). Angewandte Chemie, Volume 101, Issue 4, April 1989, pp. 495–496.

Boulois H., D. de; Joner E.J.; Leyval, C.; Jakobsen, Iver; Chen, B.D.; Roos, Per; Thiry, Y.; Rufyikiri, G.; Delvaux, B.; Declerck, S., 2007: Role and influence of mycorrhizal fungi on radiocesium accumulation by plants. Journal of Environmental Radioactivity. 2008;99:785-800. https://doi.org/10.1016/j.jenvrad.2007.10.008. Abstract

Bresinsky, A.,  Jahn, A., 2011: Strahlende Pilze. Radiocäsium aus Kernwaffentests und dem Tschernobylunfall. Der Tintling 71. Heft 4/2011: 51–64.

Büntgen, U., Jäggi M., Egli S., 2019: No radioactive contamination from the Chernobyl disaster in Hungarian white truffles (Tuber magnatum). Environmental Pollution 252 1643. Link

Büntgen, U., Jäggi M., Stobbe U., Tegel W., Sproll L., Eikenberg Egli S. , 2019: All-clear for gourmets: truffles not radioactive. Biogeosciences, 13, 1145–1147.

Fielitz U., 2005: Untersuchungen zum Verhalten von Radiocäsium in Wildschweinen und anderen Biomedien des Waldes

Gelardi M., Vizzini A., Ercole E., Voyron S., Sun J.-Z., Liu X.-Z. (2013): Boletus sinopulverulentus, a new species from Shaanxi Province (central China) and notes on Boletus and Xerocomus. Sydowia 65(1): 45–57. Abstract

Index Fungorum – Imleria

Kabei E., Popitz Spuhler A., 2018: Radioaktive Kontamination von Speisepilzen Aktuelle Messwerte (Stand: 2018) Fachbereich Strahlenschutz und Umwelt, BfS

Kammerer, L., Hiersche L., Wirth, E., 1994: Uptake of radiocaesium by different species of mushrooms. J Environ Radioact 23:135–150.

Kalač, P., 2012: Radioactivity of European wild growing edible mushrooms. In: Mushrooms: Types, Properties and Nutrition. S. 215 – 230. ISBN 978-1-61470-110-1 Editors: S. Andres and N. Baumann. Text als pdf

Mello,  A., Murat C., Vizzini A., Gavazza V., Bonfante P., 2004: Tuber magnatum Pico, a species of limited geographical distribution: its genetic diversity inside and outside a truffle ground. Environ Microbiol 7(1):55–65. Link.

Šutara, J., 2008: Xerocomus s. l. in the light of the present state of knowledge. Czech Mycol. 60(1): 29–62.

Steiner, M., Hiersche, L., 2011: Radioaktive Kontamination von Pilzen und die daraus resultierende Strahlenexposition des Menschen. In: Mycologia Bavarica. Band 12, 2011, S. 69–85.