Keywords: chronic occupational radiation exposure, DNA strand breaks ratio, low radiation, lymphocytes, DNA repair, ionising radiation
Evaluation of chronic occupational radiation exposure by the measurement of residual/initial DNA strand breaks ratio
The comet assay was used to examine radiation workers who deal with radioisotopes such as iodine-125, iodine-131 and technetium-99m. In this study, lymphocytes from test and control donors were exposed to γ-radiation at 0, 1, 2, 4 and 6 Gy. A significant difference (P < 0.05) between the test and the control group in the level of initial damage was observed immediately after exposure. In addition, the level of the residual damage of samples from the test group after 24 hours was slightly higher than the control group. The subsequent measurement of the ratio of residual/initial breaks, representing the fraction of remained DNA break, demonstrated a lower value in the test group. These results indicated an enhanced DNA repair in the test group that led to the decline in residual/initial ratio. However, the high initial damage might be due to the presence of fragile sites in the genome of the test group.