Frequencies of micronuclei in bank voles from zones of high radiation at Chornobyl, Ukraine

A population of Clethrionomys glareolus (bank vole) from a highly radioacti ve area within the Chornobyl, Ukraine exclusion zone was sampled in June 19 97 and in June and October 1998. Internal radiation doses from radiocesium were estimated to be as high as 8 rads/d. Total dose, which takes into acco unt the internal dose from radiostrontium and the surrounding environment, was estimated to be 15 to 20 rads/d. In contrast, individuals from a refere nce population lying outside of the exclusion zone registered negligible le vels of contamination. We used the micronucleus test in a double-blind stud y to analyze blood samples from 58 individuals. We scored more than 600,000 polychromatic erythrocytes (PCEs) but could not reject the null hypothesis that the frequency of micronucleated PCEs in voles exposed to radiation wa s equal to the frequency in unexposed voles. Results of our study stand in sharp contrast to earlier reports of increased frequencies of micronuclei i n rodents exposed to fallout of the Chornobyl accident, but with radiation doses that were orders of magnitude lower than those reported here. Radiore sistance and experimental methods are possible explanations for these diffe rences in the results.