Aberrations of Genetic Material as Biomarkers of Ionizing Radiation Effects

Abstract

The observation of chromosome aberration frequency in lymphocyte karyotype is the conclusive method to assess the absorbed dose of ionizing radiation. Our study compared the incidence of chromosome aberrations in occupationally exposed healthy medical workers and in not exposed healthy population. We analyzed the effect of working place, dose by thermo luminescence dosimeter (TLD), duration of occupational exposure (DOE) and age on the sum of aberrant cells and aberrations. The four-year study included 462 subjects with a mean age of 42.3 years, who were occupationally exposed to ionizing radiation and 95 subjects with a mean age of 35.2 years, who were not exposed to ionizing radiation, during the same time period and from the same territory. All of them possess TLD which is read by a scanner for thermo luminescence dosimeters. Modified Moorhead’s micro method for peripheral blood lymphocytes and conventional cytogenetic technique of chromosome aberration analysis were used for the analysis of chromosome aberrations. Stained preparations (Gyms) are observed in immersion by light microscope. The karyotype of 200 lymphocytes in metaphase is analyzed; the most characteristic aberration: dicentric, then the ring and acentric fragments. The incidence of chromosome aberrations was found to be 21.6% in the exposed group and 2.1% in the controls, while the “findings within the limits” (non-specific chromosome lesions – gaps, breaks, elongations, and exchanges) were equal in the two groups (22%). Among occupationally exposed medical workers, the highest incidence was found in nuclear medicine workers (42.6%), then in orthopedists (27.08%). There is a highly significant difference of the number of aberrant cells and the sum of chromosome aberrations between the exposed and control groups ( p < 0.001). The sum of chromosome aberrations and the number of aberrant cells were in positive correlation with the duration of exposure ( p < 0.001), and to a less degree of probability with the age ( p < 0.05) in the exposed workers. In the controls, this correlation was negative and insignificant. The group of subjects with a duration of occupational exposure up to 15 years had a significantly smaller number of aberrant cells and chromosome aberrations in comparison to the subjects with longer duration of occupational exposure, over 15 years.