Chromosomal aberrations after exposure to low doses of ionizing radiation.
OBJECTIVE
To compare the incidence of chromosomal aberrations (CA) in healthy medical workers occupationally exposed to ionizing radiation (IR) and in non-exposed healthy population.


METHODS
This was a 4-year study with 462 subjects, mean age 42.3 years, occupationally exposed to IR (exposed group - E), and 95 subjects, mean age 35.2 years, not exposed to IR (control group - C), during the same time period and from the same territory. Thermoluminescence dosimeters (TLD) were used for assessment of IR exposure. Modified Moorhead's micro method for peripheral blood lymphocytes and conventional cytogenetic technique of CA was used for analysis of CA. The karyotype of 200 lymphocytes in metaphase was analysed by immersion light microscope.


RESULTS
The average annual absorbed dose measured by TLD was 14.5 mSv in group E and 2.8 mSv in group C exposed to natural level of radioactivity. The incidence of CA was 21.6% in group E and 2.1% in group C (p <0.05), while non-specific chromosomal lesions (gaps, breaks, elongations) were equal in both groups (22%). In group E, the highest incidence was found in nuclear medicine workers (42.6%), then in orthopedic surgeons (27.08%). Highly significant difference (p <0.001) was found in the number of aberrant cells and the sum of CA between group E and C. The sum of CA and the number of aberrant cells were positively correlated with the duration of exposure (p < 0.001), and to a lesser degree with age (p < 0.05) in group E. In group C, this correlation was negative and insignificant. In group E, subjects with duration of occupational exposure (DOE) up to 15 years (subgroup E I=327) had significantly less number of aberrant cells and CA in comparison with the subjects with DOE over 15 years (subgroup E II=135) (p < 0.01).


CONCLUSIONS
Long-term occupational exposure to low doses IR contributes to the development and increased frequency of specific CA (like dicentrics), but varies in relation to different working places. The majority of subjects had no other genetic modifications (non-specific chromosomal lesions) affected by low doses of IR.
University of Belgrade, Faculty of Medicine, Institute of Occupational Medicine and Radiological Protection, Belgrade, Serbia. m.masha@beotel.net
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Milacic
D000328:Adult; D002869:Chromosome Aberrations; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008214:Lymphocytes / Q000528:radiation effects*; D016273:Occupational Exposure; D011832:Radiation Injuries / Q000473:pathology; D011834:Radiation Monitoring; D011839:Radiation, Ionizing; D018570:Risk Assessment