percent resulted from U.S.S.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 radiations while their shorter range beta particles will contribute a muchless biologically significant exposureto the skin. Table 2 also shows that of the 193 million tons energy equiva- half-life is approximately 30 years. Thus, it is possible for cesium 137 to remain in our environment for long periods of more orless uniformly around the world. lent releasing fission products, about 161 million tons were scattered 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 detona- tion in the lower atmosphere at 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 in- cluding iodine 131 in the local environment. At the time of a nuclear detonation somethinglike 200 differ- ent radioactive substances are formed by fission. Additional ones are created by induced activity. Although these materials emit only radiations with which we are already familiar—gamma raysand 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 radionuclides 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 fall- out material outside the body. The problem of estimating these latter radiation doses is again simplified by considering first cesium 137 and then lumping all 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 sur- face where most of them remain and thus neverget inside our bodies. These external, man-made radionuclides, however, will irradiate the whole body by their penetrating gamma 4 Of the radionuclides that contribute to external radiation, the most important single one is cesium 137. Its radioactive time without losing muchofits activity, although there can be loss or reduction in availability of the material through normal weathering processes. Still cesium 137 does have a short enoughhalf-life so that most of the radiations are released within the lifetime of a man. All radioactive materials in fallout, except cesium 137, which remain outside the body may be conveniently lumped together to estimate their contribution to external exposures. These usually are called “short-lived” even though some do have halflives of upwards of one year. In spite of the fact that nearly all of the radiation exposure received from these short-lived radionuclides is completed within a year after the radionuthe clides are created the total amount of exposure during year maybe greater than that received from cesium 137 within 30 years. Cesium 137 also is one of the two (carbon 14 is the other) principal radionuclides deposited internally that irradiate the whole body. It is not a major source of the total whole radiation dose except in such cases as that of Eskimos whose diet is largely caribou or reindeer meat. The food chain (lichen-caribou-Eskimo) reflects the relatively high surface contamination of cesium 1387 on the lichens. The Data The highest whole body exposures from nuclear weapons tests ever reported by the United States were about 175 roent- gens to 64 Marshallese following the March 1, 1954 surface nuclear test detonation at the Pacific Proving Ground.’ This situation resulted from a shifting of the winds so that the local heavy fallout from this large yield surface burst occurred, in part, across the islands instead of the open sea. The Marshallese were evacuated, given medical treatment and returned to their homeisland of Rongelap on June 29, 1957 3). after radiation levels had subsided to acceptable levels (fig. —all born been have children From 1956 to 1962 about 24 normal—and four persons have died from natural causes.® (Oneof these had been on another island and received 69 roentgens exposure.) Four deaths have occurred in the comparison population of like size. There were, of course, noticeable and effects immediately after the irradiation such as nausea 5