Early research on the subject was largely confined to short-lived species of animals such as rats. and mice and to brief experiments of a year or two at most. Considerable uncertainty exists, however, in extrapolating the results of these experiments when calculating the effect of long-duration, low-intensity exposures on man. These data must be Internal emitters. Radioactivity accumulates in the human body followin; prolonged exposure to certain radioactive isotopes in air, water, or food, inasmuch as these isotopes are selectively absorbed by various organs of the body. Depending upon the rates of absorption and excretion, the energy of the radioactivity, and the sensitivity of the organs to radiation damage, it is possible to arrive at a figure for the permissible concentrations of the radioactive elements in air and water consumed by human populations. All the values of the biological reac- tions required for the calculations (such as rate of absorption, sensitivity, etc.) are not known accurately, and the calculated results must be qualified with arbitrary “safety factors" which may or may not be fully justified. Research programs to obtain better data are in effect at the Los Alamos Scientific Laboratory and at Argonne National Labora~ tory, and it is planned to encourage the initiation of research projects in this field at other AEC facilities and at private institutions during the next year. Radiation Injury and Long-Term Effects Radiation cataract studies. The appearance of incipient cataracts among a few nuclear physicists (off the nroject) who had been exposed to cyclotron-produced radiation led to the Commission's request last year that the Division of Medical Sciences of the National Research Council make a thorough study of the problem. The Committee on Radiation Cataracts of the National Research Council, established for the purpose, assisted in studying the cases of radiation cataracts, recommended a sound research program, and screened research proposals for their scientific merit. As a result of their recommendations, approval was given during the quarter to research projects on radiation cataracts at four universities - Harvard, Lassachusetts Institute of Technology, University of Chicaso, and State University of Iowa. These are listed in further detail in Appendix D. Other proposals are under consideration, and related studies are being made at Oak Ridge National Laboratory and Argonne na- tional Laboratory. At the suggestion of the Committee on Ophthalmology of the National Research Council, the Atomic Bomb Casualty Commission (with funds pro- vided by the U. S. Atomic Onergy Commission) sponsored a survey to determine what, if any, late ocular effects have resulted from the atomic - l2 - sy Ame ated ea Duta 0 ean ed ge prea cee cate ene ee oe Re AS et Sete et mes ee een nembeenas supplemented therefore by lifetime chronic exposure studies on relatively long-lived species such as the dog, and by a more critical survey of the fragmentary data available on man in the records of radiologists. The mouse genetic program recently established at Oak Ridge may be important in establishing the effects of the low level exposure on large segments of human population.