Cytogenetic biomonitoring of human radiation exposures: possibilities, problems and pitfalls.

The use of chromosome aberration analysis has progressed and is now generally recognized to provide a useful means for the assessment of dose and possible health consequences in human exposures to relatively high doses of ionizing radiations. The automated analysis of radiation-induced chromosome aberrations will facilitate the better understanding of the health effects of radiations on human populations, particularly of those at low levels. However, the reaction kinetics of chromosome aberrations in the low dose or low dose-rate exposures are not well delineated. In this paper, possible reaction kinetics of chromosome aberrations, particularly those in human lymphocyte, in low dose-rate exposures have been discussed based on the cytogenetic data on the Thorotrast patients, persons involved in the protracted occupational exposures and modulation of chromosome aberrations by radioadaptive response. In the protracted low dose-rate exposures, the levels of chromosome aberrations, whether they are stable- or unstable-type aberrations, are not in a simple function of the total accumulated dose due mainly to the lymphocyte kinetics and modulation by cellular stress response. If this formalism is realistic, the dissociation between levels of chromosome aberrations and cancer risks may be large for the low level protracted exposures.