Systematical cytogenetic analysis of stable and unstable chromosomal aberrations in peripheral blood of NPP workers

The purpose of this study is to investigate the relationship between stable and unstable chromosome aberration frequency in peripheral blood lymphocytes using Giemsa staining and FISH chromosome analysis. 15 Nuclear Power Plant's workers occupationally exposed to external radiation, with high (> 500 mSv) and intermediate lifetime cumulative doses and 15 healthy individuals, not occupationally exposed to radiation from administrative staff of Kozloduy NPP have been selected. The cytogenetic results in 10 years following systematic investigations by conventional analysis are shown. A total 14 610 metaphases was scored from 15 NPP workers and 15 controls. Mean frequency of dicentrics in workers group was 1,25 x 10-3 dic/cell. The mean frequency was 0,27 x 10-3 dic/cell in controls. It was observed 5 times lower dicentric frequency in controls then in workers, but it is not significant. It is known that dicentrics are unstable type of aberrations and their persistence depends on lymphocytes life time (about 3 years). The results are consistent with recent findings for Nuclear power workers by Giemsa staining. Dose-response dependence, genome frequency of translocations and dicentrics per 100 cells in NPP workers and controls are presented. The overall mean total translocation frequency for control group was 1.7x10-3 tr/cell and 5.4x10-3 tr/cell. When compared to unexposed controls the yields of translocations were significantly higher, but no dose dependence was apparent. Chromosome analysis of radiation exposed populations, using techniques to identify stable aberrations, offers the opportunity to examine the relative effectiveness of different exposure conditions and is of particular relevance since chromosome rearrangements are of prime importance in process of carcinogenesis. Such studies should therefore aid the understanding of risks associated with radiation exposure