PERSISTENCE OF TRANSLOCATIONS AFTER ACCIDENTAL EXPOSURE TO IONIZING-RADIATION

Purpose: To assess the validity of translocations for retrospective bi odosimetry using FISH chromosome painting of peripheral lymphocytes in repeated samples of people accidentally exposed to radiation. Materia ls and methods: Blood samples from five people exposed to mainly whole -body irradiation of gamma-rays from a radiation accident in Estonia i n 1994 were taken at 2-4 month intervals. A total of eight samplings w ere carried out, including one directly after the accident. Fluorescen ce in situ hybridization with probes for chromosomes 1, 2 and 4 was pe rformed on metaphase preparations from 48 h whole blood cultures; 1500 cells were scored from each individual per time point. Results: Trans locations remained relatively stable during 2 years after exposure in all subjects. A noticeable decrease in complete translocation yields a nd a significant decrease in incomplete translocations were observed i n one person. In addition to whole-body exposure, he had also been exp osed to partial-body irradiation. Due to the overall persistence of tr anslocations, dose estimates were very similar throughout the 2 year p eriod. A rapid decline in dicentric frequencies was noted during the f irst year after exposure. Conclusions: The results suggest that during 2 years the yield of translocations in peripheral lymphocytes remaine d at a constant level after whole-body exposure. This finding supports the use of translocations for retrospective dosimetry, at least withi n this relatively short period of follow-up. In the case of partial-bo dy irradiation, however, the elimination of co-existing unstable aberr ations reduced the translocation yield over time. Follow-up will be co ntinued in order to determine the stability of translocations over lon ger times.