BIODOSIMETRY AFTER ACCIDENTAL RADIATION EXPOSURE BY CONVENTIONAL CHROMOSOME ANALYSIS AND FISH

A Cs-137 source was Stolen from a radioactive waste depository in Esto nia on 21 October 1994 and kept in a private house for 4 weeks. This r esulted in the death of one person, acute radiation injuries to four p eople and exposure of several other people to lower doses of radiation . Analysis of chromosomal aberrations in peripheral blood lymphocytes was used in the assessment of radiation exposure of 18 people involved in the accident. Dose estimation assessment based on the frequencies of dicentric chromosomes was performed both by the standard method and by considering possible dose protraction and non-uniform exposure. Co nsiderable differences in dose estimates were obtained depending on th e approach used, ranging from about 1 Gy to almost 3 Gy in the patient s most heavily exposed. In view of the deterministic health effects ob served in some of the subjects, it was concluded that the dose estimat es involving information on dose protraction were more realistic than those obtained by comparison with the standard high dose-rate calibrat ion curve; Chromosome painting analyses using fluorescence in situ hyb ridization, with a probe cocktail for chromosomes 1, 2 and 4 and centr omere detection, were performed in parallel. Good agreement on dicentr ic chromosome frequencies was observed between the conventional and pa inting analyses. The frequencies of complete translocations were compa rable with the frequencies of dicentric chromosomes. In addition to th e complete translocations, a pronounced increase in the frequency of i ncomplete translocations was observed. Dose estimates performed on the basis of FISH translocation frequencies were consistent with the dice ntric analysis.