Chromosome aberrations in nuclear power plant workers: the influence of dose accumulation and lymphocyte life-time.

Chromosome analyses were performed in blood lymphocytes of 22 nuclear power plant workers with a mean accumulated radiation dose of 390 mSv (270-530 mSv). Nineteen workers had received 300 mSv 4-16 years prior to sampling. The frequency of dicentrics and ring chromosomes (1.75 x 10(-3)) was significantly elevated as compared to a control group (0.58 x 10(-3)). Based on the initial slope of an in vitro 60Co gamma-ray curve, a biological dose estimate of only 110 mSv was derived. This can be interpreted in terms of an "equivalent-acute" dose at the time of blood sampling which can be derived by weighting annual doses during working periods of 12-30 years for a mean life-time m of lymphocytes. The annual doses were additionally weighted for a uniform distribution during a whole year. Using m = 10 years, a mean "equivalent-acute" dose of 90 mSv (64-157 mSv) is obtained, which compares more closely to the biologically estimated dose than 20 mSv (7-71 mSv) based on m = 4.3 years.