[Evolution of the ideas on genetic hazards of ionizing radiation in humans].

Based on the reports of UNSCEAR for the period from 1958 to 2001 the paper presents a retrospective analysis of the use of direct methods and the doubling dose method for quantitative determination of the genetic risk of human exposure expressed as different hereditary diseases. As early as 1962 UNSCEAR estimated the doubling dose (a dose causing as many mutations as those occurring spontaneously during one generation) at 1 Gy for cases of exposure to ionizing radiations with low LET at a low dose rate and this value was confirmed in the next UNSCEAR reports up to now. For cases of acute irradiation the doubling dose was estimated at 0.3-0.4 Gy for the period under review. The paper considers the evolution of the concepts of human natural hereditary variability which is a basis for assessing the risk of exposure by the doubling dose method. The level of human natural genetic variability per 1,000,000 newborns is estimated at 738,000 hereditary diseases including mendelian, chromosomal and multifactorial ones. The greatest difficulties in assessing the doubling dose value were found to occur in the case of multifactorial diseases the phenotypical expression of which depends on mutational events in polygenic systems and on numerous environmental factors. The introduction in calculations of the potential recoverability correction factor (PRCF) made it possible to assess the genetic risk taking into account this class of hereditary diseased. The current estimate of genetic risk is 3000-4700 genetic diseases in the first generation per 1,000,000 newborns after exposure of the parental generation to 1 Gy at low dose rate. A certain part of genetic changes after exposure of the parental generation to radiation will express themselves in the second generation, in grandchildren (1150-3200 cases or 56% of the effect predicted for the first generation), and in succeeding generations.