Radiocaesium in game animals in the Nordic countries

Forest ecosystems in the Nordic countries have been shown to be very important for the overall transfer of Chernobyl radiocaesium to man. One of the major pathways of radiocaesium to man is through game animals, mainly moose and roe deer. As most of the game meat is consumed by the hunters - about 3000 000 in Sweden - and their families, these constitute the critical group. Aggregated transfer factors of between 0.01 and 0.03 m2 kg-1 were found for moose and 0.03 to 0.14 for roe deer. The considerable variation for roe deer is a result of the large seasonal variation in 137Cs activity concentrations in these animals with a peak value in August and September when the fruitbodies of fungi having high activity concentrations of 137Cs, are abundant. In Sweden where annually between 100 000 and 135 000 moose are harvested the calculated annual transfer of 137Cs by moose to man after the Chernobyl accident has been between 2.4 and 2.7 GBq, corresponding to an annual collective dose of 30 and 33 manSv. The corresponding transfer by roe deer lay been between 560 and 1 400 MBq, corresponding to an annual collective dose of 7 to 17 manSv. During the post-Chernobyl years there has been very little or no decrease in 137Cs acitivity concentrations in moose and roe deer. The effective ecological half-life of radiocaesium in the forest ecosystem in the Nordic countries seems therefore to be very long and we suggest that the physical half-life is the best estimate. (orig.)