5 APPRAISAL OF THE ACCEPTABILITY OF POSSIBLE DAMAGE If extrapolation to very low exposure levels is justified, it may be expected that some damage, however slight, will be produced by radioactive fallout, in the present and future generations. Estimates of the number of individuals in the world’s population who may show some damage in the course of time (many generations in the case of genetic damage) are large in absolute terms. Whether they are considered to be small in comparison to the unavoidable damage caused by spontaneous mutations and the presently accepted hazardsof life, depends on the ethical and emotional makeupof the individual and, therefore, there can be honest dif- ferences of opinion. It is a fact, however, that we accept death and maiming through preventable accidents. (Most automobile accidents could be prevented by reducing the speed limit to 10 miles per hour). We discount the harm by considering the advantages. Also, in the case of most accidents the individual at least believes he can exercise some control. The fallout hazard is essentially beyond the control of the individual and involves, also, his descendants. This has a strong emotional impact. Ionizing radiation has played an important part in manyof the scientific and technological advances of this century. It is also an unavoidable by-product of the “atomic age.” A certain amount of exposure, even under the most rigid controls, is inevitable. Thus, diagnosis of disease by means of x-rays necessarily involves irradiation of the body region under examination, even when the most stringent protective measures are employed. The NAS Committee on Genetic Effects of Atomic Radiation, recognizing the benefits as well as the harm that might result from the ever increasing production and use of ionizing radiation in our civilization, has recommended “that the general public of the United States be protected, by whatsoever controls may prove necessary, from receiving a total reproductive lifetime dose (conception to age 30) of more than 10 roentgens of man-made radiation to the reproductive cells.” The same Committee emphasizes that this is a reasonable but not a harmless average dose for the whole population, insofar as genetic effects are concerned. This means, in effect, that if this average 30-year dose is not exceeded, tht resently predictable genetic damage to the population is expected to be tolerable. The same Committee estimated that a dose of 10 r to the population of the United States would give rise to some 50,000 new instances of tangible inherited defects in the first genera- tion and about 500,000 per generation ultimately, assuming an indefinite continuation of the 10 r increased rate and also assuming a stationary population. The total number of mutants that would be induced by this radiation dose to the population of the United States and passed on to the next total generation, was estimated to be roughly 5,000,000 by six geneticists on the NAS Committee. These increases in the number of children with tangible inherited defects and the total number of mutants in the United States, therefore, are considered tolerable by present genetic standards. By the same token, the genetic damage that may be expected from the estimated gamma ray fallout dose of 0.1 r in 30 years, which is 100 times less, must be considered negligible. The significance of possible somatic injury from fallout may be appraised similarly by reference to the “genetic dose” of 10 rin 30 years. Since fallout gamma rays reach the body essentially from all directions, the dose to the gonads is considerably less than that to the surface of the body. It may be assumedtherefore, that in a fallout field that would give a gonad dose of 10 r of penetrating gammaradiation in 30 years, this is also the approximate dose in rads received by internal organs such as the blood forming organs and the skeleton. Consequently, the genetically acceptable dose corresponds to a dose rate in these organs of 0.33 rad per year. The estimated bone marrow dose rate froma Sr®® concentration in bone of 20 upc per gram of Ca is 0.03 rad per year and that in bone is 0.056 rad per year. Hence the possible increase in the leukemia death rate attributable to Sr®° in the skeleton would be 9% of that resulting from the genetically acceptable dose rate. The corresponding figure for the possible increase in the death rate from bone sarcoma is 17%. Hence, by the standards used by the Genetics Committee in arriving at the average population gonad dose of 10 r in 30 years, the possible increase in death rate from leukemia or bone sarcomaattributable to the estimated fallout, is well below the acceptable degree of damage. The same reasoning and conclusion apply to any other possible effect of fallout radiation of comparable dose rate in 275