Sagat re henen ts Ter SURES tease DS RADIATION STANDARDS, INCLUDING FALLOUT 341 effect, upon nontarget nations of the Northern Hemisphere what has been recommended as an upperlimit for tolerable exposure of a population tomanmaderadiation. This 10 roentgens of whole body radiation at a low dose rate would, if administered to an entire population, produce a change in the numberof genetically defective individuals born alive. At the present timethis is estimated to be probably 4 percent of all births. (That estimate is somewhat higher than what is used in the recent Federal Radiation Council paper, because they considered only very severe defects, and this estimate is for all grades of evident defect. My figure is based on the United Nations Scientific Committee report on “The Effects of Genetic Radiation.”) A 10-roentgen dose to a population might increase the freqency of genetically defective persons born in that population from 4 to 5 percent, or perhaps less. This would not occur until many generations have passed, and if the exposure were limited to a single generation, the level would gradually drop back again to the original level of 4 percent. Even if the doubling dose, that is, the dose of radiation which would double the total number of mutations occurring spontaneously in the popu- lation, turned out to be as low as 10 roentgens instead of the value of 40 to 60 which was assumed in making that calculation, one would still not expect the level of genetically defective births in a population exposed to 10 roentgens to rise above 8 percent of all births. This is a frightful conclusion, and yet it is nevertheless in a certain sense somewhat reassuring if applied to the genetic effects of a major nuclear war. Finally, I would like to emphasize a point made in the 1960 report of the NAS Genetics Committee respecting the extent of damage in human populations due to unfavorable mutant genes. The damage is not simply a question of the frequency of these genes. It also dependson the relative amounts of harm they do to individuals and to society. As the report states: “How, for example, does one measure quantitatively the relative importanceof a stillbirth, a feeble-minded child, and a death during adolescence?” Or, one might add, of a death very soon after conception, when the mother is often unaware that an abortion has occurred? In this connection I can only recommend for study the thought-provoking appraisal of the question by Prof. Sewall Wright, which was printed as an addendum to the 1960 report of the NAS Committee. All members of the Committee were not in agreement with Wright in his considerations, but all of them, I think, are fully agreed that much study of this sort is needed before we can reach a just appraisal of genetic damage to a population. Representative Price. Thank you very much, Dr. Glass, for a very effective paper. Incidentally, the entire statement will be included in the record. (The statement follovrs:) STATEMENT or H. BENTLEY Gass, PROFESSOR, DEPARTMENT oF BIOLOGY, JOHNS HorpKINS UNIVERSITY, BALTIMORE, Mb. I believe I am expected to summarize whatever developments have occurred since the hearings of 1959 in our understanding of the genetic effects of radiation and fallout. In certain respects this task has been greatly simplified for me by the 1960 Report of the National Academy of Sciences Committee on the Genetic Effects of Atomic Radiation, of which Iam amember. This report was itself designed to update the earlier report of that Committee, dating from 1956. count eee eeSS - ree vaptutitnrpged nat nsemmantets 5p FaRoteAeeastSALEONES RSE