Consequences of the Chernobyl fallout for wild populations in South-Eastern Sweden

An investigation was carried out in Sweden aimed at studying the impact of the Chernobyl fallout on the environment. Wild small mammals (orders Rodentia and Insectivora) were used as biological indicators of radioactive contamination of a region of south-eastern Sweden. The animals were captured in three differently contaminated areas, and for control, in an area with negligible fallout. The results obtained show that the activity in the captured animals was correlated with surface deposition. The differences between the species investigated and the influence of feeding habits on the contamination levels are discussed. A mutagenicity test (bone marrow micronucleus test) was also performed on the rodents in order to verify the occurrence of a genetic damage. A positive correlation between the increase of genetic damage and both 137Cs content in muscle and surface contamination in trapping sites was found. The estimated doses absorbed by the investigated animals were too low to explain the obtained effects. An explanation of this discrepancy between dose and measured biological effect is not available, yet similar results have been repeatedly reported after the Chernobyl accident and should be matter of further discussions. It is possible that an increased frequency of chromosomal aberrations might occur already at minimal dose gradients. (author)