Preliminary Reanalysis of Radiation-Induced Chromosome Aberrations in Relation to Past and Newly Revised Dose Estimates for Hiroshima and Nagasaki A-Bomb Survivors

Summary

A comparison of the chromosome data from 408 atomic bomb survivors, 229 in Hiroshima and 179 in Nagasaki, was performed in terms of the frequency of cells with radiation-induced chromosome aberrations plotted against the existing A-bomb dosimetry system (T65D), and the new dosimetry systems from ORNL (Oak Ridge National Laboratory) and LLNL (Lawrence Livermore National Laboratory). Preliminary analysis-shows that the inter-city difference in aberration frequencies is still apparent at every T65D dose level, while the aberration frequencies based on both ORNL and LLNL systems do not differ strikingly between the two cities, particularly in the dose range below 200 rad.

In our previous cytogenetic study of atomic bomb survivors in Hiroshima and Nagasaki (Awa et al. 1978), we found a close relationship between radiation dose and frequency of cells with residual chromosome aberrations. Furthermore, we noted a difference in aberration frequencies between Hiroshima and Nagasaki: the frequency of aberrant cells was consistently higher in every dose range in Hiroshima than in Nagasaki. One possible explanation for this difference was thought to be the contribution of the neutron component released from the bomb at Hiroshima. Estimated radiation doses for individual survivors used in the cytogenetic study were derived from the T65D (tentative 1965 dose) system, currently in use at RERF, calculated by Auxier et al. (1966), and Milton and Shohoji (1968).

Recently, re-evaluation of A-bomb radiation air doses was made by Loewe and Mendelsohn (1981) of the Lawrence Livermore National Laboratory (LLNL), and independently by Kerr (1981) and his associates of the Oak Ridge National Laboratory (ORNL). The major difference between the existing T65D and the two new dosimetry systems is that for Hiroshima, the estimates for the relative magnitude of the neutron component are much lower for the ORNL and LLNL than for the T65D system.

The purpose of this study is to compare the somatic chromosome aberration frequencies from Hiroshima and Nagasaki A-bomb survivors, based on the T65D, ORNL and LLNL dose estimates.