ABSTRACT

The results of many-years studies ofthe efficiency of low-dose (up to 0.5 Gy) ionizing radiation carried out on cells in a tissue culture and on blood lymphocytes of humans (adults and children) are reviewed. It was found in laboratory studies and studies performed in areas contaminated with radionuclides as a result of the Chemobyl accident that the descendants of irradiated cells exhibit genome instability. This instability manifests itself as delayed cell death, an increased incidence of cells with micronuclei, a decrease in proliferative activity, the loss of capacity for adaptive response, increased sensitivity to subsequent irradiation, and increased frequency of sister chromatid exchanges. The results of studies of the adaptive response in a population of human blood lymphocytes are presented. It was found that, in all populations examined, there are individuals who do not develop adaptive response and individuals exhibiting an increased radiosensitivity after adaptive irradiation (0.05 Gy). On the basis of the own results and literature data, possible mechanisms of the effects of low-dose ionizing radiation are discussed. It is concluded that (a) irradiation with low doses may lead to the formation of a population having new properties and (b) the effects and the mechanisms oftheir realization may differ from those operating upon irradiation with high doses.