DNA damage evaluated by the comet assay in lymphocytes of Ukrainian children with detectable 137-Cs internal contamination

The comet assay is actually one of the most widespread tool to evaluate DNA damage. Its sensibility to low dose radiation has been tested in vitro, both there is a limited data showing its application and sensibility in chronic exposure situation, where the assay seem to be more useful. The influence of the internal contamination caused by the Chernobyl accident on the level of DNA damage was evaluated by the comet assay on lymphocytes of 56 Ukrainian children. The study was performed at the beginning of the 2003 year on children with demonstrable 137 Cs internal contamination caused by the food consumption. The children were selected for the study immediately after a 137 Cs whole body counter measurement of the internal contamination. The minimal detectable amount (MDA) of 137 Cs was 75 Becquerel. The control group included 29 children without a detectable internal contamination, while in the exposed group 27 children with the internal contamination over the MDA were included. Blood sample was taken by a finger prick, the alkaline version of the comet assay was used, in a combination with silver stained comets and arbitrary units for comet measurement. Factors like children disease, medical treatment, surface contamination of children living location, etc was considered in the study. Non significant differences (p>0.05) on DNA damage in control (10.15±7.27 Arbitrary Units) versus exposed (8.93±5.97 Arbitrary Units) group were found. These results suggest that low doses of Cs internal contamination are not able to produce detectable DNA damage under the conditions used for the comet assay in this study. Further studies considering highest exposition on chronically exposed people should be performed using this assay.