hae - 12 - Normally, about 1 in 30 persons may be expected to show some manifestation of genetic disease at birth or during childhood, the periods when serious genetic defects become apparent. This, on the average of 12 births per year assumed to occur in the Bikini population,would yield about 0.36 of a case of a genetic defect before adult life. Exposure of the population to 200 millirems per year is calculated to increase the expectation of genetic defects from 3.0% to 3.2% and the estimated number of defects would be increased from -36 to .38 among the 12 individuals born each year. With respect to cancer mortality, U. S. vital statistics provide an incidence of about 1 cancer death per year in a population of 600 people. The conservative estimate of the BEIR report is that .0002 deaths may be expected per year per rem. Thus, an annual exposure of 200 mrem would result in an estimated 2.4% increase over the normal number of cancer deaths. This would raise the expected cancer incidence from 1 to 1.024 deaths per 600 people per year. These estimates of risk can be translated into terms of L additional cancer death in 40 years or 1 additional genetic defect in 50 years for the 600 in the population. If a nonlinear dose-effect relationship is ultimately accepted by the scientific community, the risk estimate will be significantly lower. ‘It must be recognized that in dealing with small populations, statistical variation affects the number of genetic defects or cancer deaths that occur in any one year. Thus, any population of 600 persons in the United States might experience as many as a few cancer deaths in some years and none in wim 5000.95.90