Natural radioactivity and total K content in wild-growing or cultivated edible mushrooms and soils from Galicia (NW, Spain)

The radioactive isotope, 40K, of naturally occurring potassium (0.012%) is present in the Earth’s crust in a low percentage of all potassium, leading to its presence in almost all foodstuffs. The impact of 40K activity concentrations was assessed in wild and cultivated edible mushrooms and in growing substrates. Samples were analysed by gamma spectroscopy. In the wild mushroom species, the average activity concentration of 40K was 1291 Bq kg−1 dry weight (dw), approximately 140 Bq kg−1 fresh weight (fw), with a range of average values per species from 748 in Lactarius deliciosus to 1848 Bq kg−1 dw in Tricholoma portentosum. The cultivated species presented an average value of 1086 Bq kg-1 dw; and the soils, compost of cultivation and wood of substrate are 876, 510 and 59.4 Bq kg−1 dw, respectively. The total K content reached a maximum of 59,935 mg kg−1 dw in T. portentosum. The transfer factors (TF > 1) suggested that mushrooms preferentially bioconcentrated 40K. Cantharellus cibarius, Craterellus tubaeformis, Hydnum repandum and T. portentosum by most TF could be considered as bioindicators of 40K. Taking into account that the annual radiation dose of 40K due to the average consumption of mushrooms analysed (0.15 μSv/year) is very low, it can be concluded that the consumption of these mushrooms does not represent a toxicological risk for human health. Finally, according to the total K content, from the nutritional point of view, these mushrooms could be considered as a potential source of potassium for the human diet.