percent resulted from U.S.8.R. tests. This total energy release is of use in estimating the amount of carbon 14 produced. Incidentally, it is assumed that the carbon 14 is distributed moreor less uniformly around the world. Table 2 also showsthat of the 193 million tons energy equivalent releasing fission products, about 161 million tons were seattered globally.2 Approximately two-thirds of this amount originated from U.S.S.R. tests but will account for about threequarters of the long-term fallout in the United States because of meteorological factors. This is because there will be more deposition in the North Temperate Zone from a nuclear detonation in the lower atmosphereat a northerly latitude than from the same shot at an equatorial site. Atmospheric tests at the Nevada Test Site have contributed very little to the deposition of long-lived radioisotopes but at times have been the source of relatively high amounts of short-lived radioactive materials including iodine 131 in the local environment. At the time of a nuclear detonation somethinglike 200 differ- ent radioactive substances are formed by fission. ones are created by induced activity. Additional Although these ma- terials emit only radiations with which we are already familiar—gamma rays and beta particles—it appears at first glance to be almost an impossible task to consider them individually and in the aggregate for an appraisal of their health hazard. Fortunately, for an analysis of the problem, most of the radio- nuclides are of little health consequences because of their short radioactive half-lives or other characteristics such as being: highly insoluble. In fact, it is possible to estimate the radiation doses to various organs of the body by considering only five principal radionuclides in fallout that are deposited internally, i.e., iodine 131, strontium 90, strontium 89, cesium 137 and carbon 14. To these internal doses there must be added those to the whole body due to the radiations from fallout material outside the body. The problem of estimating these latter radiation doses is again simplified by considering first cesium 137 and then lumpingail of the remaining radionuclides together in the calculations. B. WHOLE BODY EXPOSURES Background Information Fallout particles consisting of inert materials together with the associated radioactive materials settle to the earth’s surface where most of them remain and thus never get inside our bodies. These external, man-made radionuclides, however, will irradiate the whole body by their penetrating gamma 4 ye PY te C 5 0 (j u 0 wed