Estimation of Residual Radiation from Chromosomal Aberrations

Estimation of Residual Radiation from Chromosomal Aberrations

When one is irradiated, abnormalities appear among chromosomes in the irradiated
nuclei of a cell. Since this frequency of chromosomal aberration is closely related to the

triangles) and at 2.4 km or more away (denoted by circles). The initial radiation dose
given by the T65D and DS86 are denoted by almost straight lines, dashed and solid ones,
respectively. The broken curves are obtained by subtraction of the contribution of the
initial radiation given by DS86 from the solid curves and can be attributed to the effects
of fallout contribution. The peak values 0.06 Gy and 0.3 Gy obtained from unstable and
stable chromosomal aberrations exceed the initial radiation dose at 2.0 km and 1.6 km,
respectively from the hypocenter. In the regions beyond these distances the effects of
exposure by fallout exceed those from the initial radiation. It should be noted that the
estimated dose based on the frequency of chromosomal aberration in circulating
lymphocytes represents the effects averaged over the whole body and do not include
local effects from the insoluble radioactive fine particles which are considered in the
case of the analysis of the incidence rates of acute diseases.
The chromosomal aberration of a larger sample of survivors had also been
investigated by the RERF study group 23 years after the bombing and the RERF have
denied the existence of chromosomal aberration in the distant region. In the RERF
investigation, however, the distant survivors with dose estimation <0.01 Gy and the
entrant survivors who were not in the city at the explosion time (NIC) were used as the
control group. The frequency of chromosomal aberration of this control group is more
than four times the control figure used world-wide and about ten times that used by
Sasaki and Miyata.