Quantitative study of unstable chromosome aberrations following life time exposure of high background radiation in China

Objective: To obtain a quantitative data regarding high background radiation-induced human chromosome aberrations by using advanced techniques. Methods: Environmental exposure dose for each individual was carefully measured. The estimated life-time doses ranged 25.2-244.8 and 5.4-51.7 mGy for individuals from the high background radiation area (HBRA) and the control area, respectively. Peripheral blood specimens were taken from 28 family members of three different generations in both areas. Purified lymphocyte culture technique for chromosome preparation was adopted and a total number of 70000 metaphases were scored. Results: In the case of HBRA, the frequencies of Dic + Rc increased with age, but no age-dependency was observed in subjects from the control area. The mean aberration yields significantly in excess of control value were seen in two older age groups. The aberration frequencies increased in proportion to the cumulative dose of the individuals living in HBRA. The estimated rate of increase per mGy was 1.5 x 10-5 per cell. Conclusion: It seems that Dic can continuously accumulated over life-time chronic low dose exposure and can serve as a reliable biological indicator. When the dose reduces to about 50 mGy, however, it becomes difficult to use to current method for quantitative analysis