FISH examination of lymphocytes from Mayak workers for assessment of translocation induction rate under chronic radiation exposures

Purpose: To estimate the translocation-induction rate under chronic exposure conditions by measuring chromosome aberration frequencies in lymphocytes from Mayak nuclear workers using fluorescence in situ hybridization (FISH). Materials and methods: Lymphocytes were examined from 27 nuclear workers at the Mayak Production Association and two control individuals using FISH with probes for chromosomes 1, 2 and 4. Official doses derived from worker film-badge records varied from 0 to 8.50 Gy. Results: The mean (+/- SD) genome-equivalent translocation frequency (F-G) was 2.30 (+/-0.75)% in the zero-dose group (n=7), and Poisson regression analysis provided the best-fit equation of F-G(%)=2.96 (+/-0.39) +0.69 (+/-0.14)D+0.12(+/-0.05)A, where D is the film-badge-derived dose (Gy), and A is age centred at 67 years. The induction rate would increase to nearly 1% Gy(-1) if the radiation dose to bone marrow, one of the major organs for lymphocytes and where their precursor cells reside, is considered. Conclusion: The estimated induction rate in vivo appeared substantially smaller than linear coefficients estimated from various in vitro studies.