Chromosomal aberrations in subjects exposed to ionizing radiation.

Occupational exposure to low doses of ionizing radiation is a particularly delicate subject for investigation, due to the cumulative effects of chronic exposure. It is extremely important to consider and to measure the biological response to given conditions of exposure. The aim of this study was to establish possible recovery from DNA damage in subjects professionally exposed to radiation in their working area by examinations for chromosomal aberrations (CA) at two different times. The first group (I) was composed of 30 professionally exposed subjects in whom unstable CA (dicentrics, ring, acentric fragments, chromatid, chromosomal breaks, and chromatid interchanges) were identified at time zero. After removal from the radiation area, they were re-examined 9 months later. The second group (II) contained 64 healthy individuals, not professionally exposed to ionizing radiation or other known mutagenic agents. In the group of exposed individuals, five (16.67%) subjects exhibited permanent unstable CAs, even after 9 months absence from the radiation. When the nonexposed and exposed groups were compared, an increase of unstable aberrations (p < 0.05) was observed in the exposed group. Nevertheless, a statistically significant decrease of dicentrics, acentric fragments, and ring frequencies was observed in exposed individuals after 9 months away from the radiation area. However, chromatid and isochromatid break frequencies increased slightly but not significantly after 9 months. The detected CAs corresponded to the total effective doses of radiation measured in our subjects. The existence of CAs in some individuals even after absence from the radiation area suggests that the time necessary for the damaged DNA to recover is extremely variable and indicates interindividual differences in radiosensitivity as well as differences in the cellular-reparation response.