Chromosomal approaches to the dose assessment in human exposure to ionizing radiation

Biological dosimetry based on aberration analysis of lymphocyte chromosomes has been successfully applied particularly in cases of accute exposures to relatively high doses of low LET radiation, which provides valuable information on the risk assessment as well. However, many uncertainties will remain for the low level exposures as well as high LET radiation. In responce to the obvious need for risk assessment and radiation protection standards, we have studied the kinetics of the lymphocyte chromosome aberrations in long-term exposure to low level radiations. Studies of Thorotrast patients and technicians involved in radiological work showed that the aberration frequency in lymphocytes is a function of the dose rate to the lymphocytes, A, production rate constant, a, renewal rate of lymphocytes, λ, and survival after a single path of ionizing particle, S, and can be expressed by the general formula: AaS/(A+λ+AS). For the dose assessment in neutron exposures, the levels of residual chromosome aberration in lymphocytes from A-bomb survivors in Hiroshima and Nagasaki were analysed in relation to the recently revised dosimetric system, DS86. In contrast to the estimate provided by DS86, the chromosomal data indicate a possibility that there was a significant contribution of neutrons to survivors in Hiroshima. (author)