The term little brown mushroom (LBM) refers to any of a large number of small, dull-coloured agaric species, with few uniquely distinguishing macromorphological characteristics.
Additionally, Boring ubiquitous mushroom (BUM) describes groups of difficult to identify larger agarics, many of which are in the genus Hebeloma.
Due to the wide spread of their mycelium, mushrooms tend to accumulate more radioactive caesium-137 than surrounding soil and other organisms.
State agencies (e.g. Bellesrad in Belarus) monitor and analyze the degree of radionuclide accumulation in various wild species of plants and animals.
This is an issue not only in Poland, Belarus, Ukraine and Russia: the fallout also reached western Europe, and until recently the German government discouraged people gathering certain mushrooms.