An evaluation of the occurrence and trends in (137)Cs and (40)K radioactivity in King Bolete Boletus edulis mushrooms in Poland during 1995–2019

B. edulis, collected from 33 forested or woodland sites across Poland over 25 years since 1995, were analysed for radiocaesium. The results ((137)Cs activity range: 25 to 10,000 Bq kg(-1) dry weight) provide a good indication of artificial radioactivity in this food material. The relatively higher levels detected in the earlier years, mostly in easterly location, is consistent with depositions from the projected Chernobyl incident (1986) fallout plumes. Nevertheless, the (137)Cs concentrations during 1995–2010 were, on average, higher than those reported by other studies for Polish B. edulis over the period 1986–1994. The data concurs with the general hypothesis and observations that deposited (137)Cs permeates slowly over time to deeper soil horizons which host the mycelial networks. This delay in availability shows that (apart from hotspots) higher contamination of fruiting bodies occurred around 10 to 20 years after the incident. Local consumers and recreational mushroomers were undoubtedly exposed, although reported (137)Cs concentrations suggest that serious breaches of regulated levels were uncommon.