BIOLOGICAL DOSIMETRY OF RADIATION WORKERS AT THE SELLAFIELD NUCLEAR FACILITY

The British Nuclear Fuels pie facility at Sellafield performs a range of nuclear-related activities. The site has been in operation since 19 50 and has, in general, employed a stable work force, many of whom hav e accumulated relatively high occupational exposures to ionizing radia tion. This paper compares the physical dosimetry with two biological e nd points for evaluating radiation exposure: fluorescence in situ hybr idization with whole-chromosome painting probes to quantify stable chr omosome aberrations (translocations and insertions), and glycophorin A (GPA) analysis of variant erythrocytes. For the cytogenetic analyses, 81 workers were evaluated in five dose categories, including 23 with minimal radiation exposure (less than or equal to 50 mSv) and 58 with exposures ranging from 173 to 1108 mSv, all but 3 being >500 mSv. In a univariate analysis, the mean stable chromosome aberration frequencie s showed a significant increase with dose category (P = 0.032), and wi th cumulative dose when dose is treated as a continuous variable (P = 0.015). The slope of the dose response for stable aberrations is 0.79 +/- 0.22 aberrations per 100 cells per sievert (adjusted for smoking s tatus), which is less than that observed among atomic bomb survivors, and suggests a dose and dose-rate effectiveness factor for chronic exp osure of about 6. Analyses of the data for GPA N/O and N/N variants fr om 36 workers revealed no correlation with dose. Neither was there a c orrelation between the frequencies of N/O GPA variants and stable aber rations, although a weak negative association was observed between N/N variant frequency and stable aberrations (r = -0.38, P = 0.05). These results provide clear evidence for the accumulation of stable aberrat ions under conditions of chronic occupational exposure to ionizing rad iation and show that stable chromosome aberrations are a more sensitiv e indicator for chronic radiation exposure than GPA variants. In compa rison with human studies of brief exposure, chronic low-dose exposures appear substantially less effective for producing somatic effects as reflected by stable chromosome aberrations. (C) 1997 by Radiation Rese arch Society.