Stable chromosome aberrations in atomic bomb survivors: Results from 25 years of investigation

Frequencies of stable chromosome aberrations from more than 3,000 atomic bo mb survivors were used to examine the nature of the radiation dose response . The end point was the proportion of cells with at least one translocation or inversion detected in Giemsa-stained cultures of approximately 100 lymp hocytes per person. The statistical methods allow for both imprecision of i ndividual dose estimates and extra-binomial variation. A highly significant and nonlinear dose response was seen. The shape of the dose response was c oncave upward for doses below 1.5 Sv but exhibited some leveling off at hig her doses. This curvature was similar for the two cities, with a crossover dose (i.e. the ratio of the linear coefficient to the quadratic coefficient ) of 1.7 Sv (95% CI 0.9, 4). The low-dose slopes for the two cities differe d significantly: 6.6% per Sv (95% CI 5.5, 8.4) in Hiroshima and 3.7% (95% C I 2.6, 4.9) in Nagasaki. This difference was reduced considerably, but not eliminated, when the comparison was limited to people who were exposed in h ouses or tenements. Nagasaki survivors exposed in factories, as well as peo ple in either city who were outside with little or no shielding, had a lowe r dose response than those exposed in houses. This suggests that doses for Nagasaki factory worker survivors may be overestimated by the DS86, apparen tly by about 60%. Even though factory workers constitute about 20% of Nagas aki survivors with dose estimates in the range of 0.5 to 2 Sv, calculations indicate that the dosimetry problems for these people have little impact o n cancer risk estimates for Nagasaki. (C) 2001 by Radiation Research Societ y.