Chromosome analysis of lymphocytes from radiation workers in tritium-applying industry
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Objectives: The frequency of chromosomal aberrations (CA) and micronuclei (MN) in peripheral blood lymphocytes was compared in two groups of persons occupationally exposed to tritium either through the use of luminous paints or in the weapons industry, with the aim of finding a correlation between the CA and MN assays, the extent of radiation hazard, and the duration of occupational exposure to chemical forms of tritium and the ability of the latter to induce hazards in human lymphocytes. Methods: CA analysis and the cytochalasin B micronucleus test were performed. Urinary tritium in both groups was measured using a liquid scintillation method. For purposes of comparison, 2 control groups (40 persons) were examined; 24 exposed individuals were matched to their controls according to age, sex, and smoking habits. Results: Values recorded for the frequency of CA in the group of workers handling tritium in luminous dial painting were 0.015 +/- 0.014 dicentrics/cell, 0.023 +/- 0.017 total u...nstable CA/cell, and 0.035 +/- 0.019 MN/binucleated cell. Urinary levels of tritium in this group of employees ranged from 1.35 to 9.43 MBq/l. As compared with their matched controls, in these workers the differences in the yield of CA as well as in MN were statistically highly significant (P LT 0.005 and P LT 0.003, respectively). The same parameters analyzed in workers employed in the armament industry gave values of 0.001 +/- 0.003 dicentrics/cell, 0.010 +/- 0.008 total unstable CA/cell, and 0.021 +/- 0.029 MN/binucleated cell. No detectable concentration of urinary tritium was found. As compared with their matched controls, in these workers the differences were also statistically significant (P LT 0.027 and P LT 0.012, respectively). The yield of CA, particularly the yield of dicentrics, was significantly higher (P LT 0.005) in the group of luminous dial painters as compared with the weapons industry workers. The difference found in the yield of MN between the two groups of workers was also statistically significant (P LT 0.084). Intercontrol differences in the yields of spontaneous CA as well as in MN were insignificant (P LT 0.683 and P LT 0.735, respectively). The results are discussed with respect to individual variations in the response to low doses of ionizing radiation, disorders in the handling of radionuclides, the duration of occupational exposure, and the chemical properties of the radionuclides used. Conclusion: Tritium in the chemical form of luminous paint is a more powerful clastogenic agent than tritium gas. Statistical analysis demonstrated that lymphocyte effects are due to the concentration of tritium in urine rather than to the duration of occupational exposure. Since the radiation hazard measured by the MN assay did not differ from that determined by the CA assay, the MN test can be recommended as a rapid assay for screening purposes in cases of occupational exposure to low radiation doses.