2. Gamma (Whole-Body) Dose The fallout (where seen) resemled snow or mist and > deposited rela- tively homogeneously so that the individuals on each island were considered to have received about the same estimated dose of gamma radiation. The children may have had a somewhat higher dose than that calculated for the adults because, being smaller, their bodies offered less self-shielding. This possibility is supported by the higher incidence of early nausea and vomiting and the greater depression of bleod elements in the young children. The flimsy houses afforded little attenuation of the radiation. The whole-body doses were calculated from measurements with radiation field survey instruments held 3 ft above the ground, made about a week after the detonat.on, by extrapolation to the time of exposure with the energy spectrum and decay taken into consideration. Table 1 shows the caiculated zamma doses for the different populations exposed. In view of the 27 geometry of exposure, the midline doses to individ- uals were higher than those obtained with the usual bilateral exposure of xradiation. More detailed treatment of the acute exposure estimates may be found in ref. 2. 3. Skin Dose The dose to the skin surface was much greater than the whole-body gamna dose because of the large amount of particulate radiation absorbed by the skin. The actual skin doses, alrhough impossible to calculate, probably amounted to more than 1000 rads, and their range of values, due to different amounts of fallout sticking to different areas, accounted for the spotty nature and varying intensity of lesiors. The extensiveness of the veta burns in each islind group correlated roughly with the amount of fallout visible on their isiand. Most of the skin dose was due to fallout deposited direetly on the skin, but some was due to beta radiation from fallout on the ground (estimated at Rongelap to be 2000 rads at the level of the dorsum of the feet, on the basis of continuous exposure and no shielding). It was fortunate that the beta radiation had an average energy insufficient to penetrate deeply into the skin and therefore resulted for the most part in superficial damage burns. The average beta particle probably did not penetrate much beyond the basal layer of the skin (“100 ym). However, since epilation occurred in many peo- . ple, the region of the hair follicles must have received an absorbed dose at least equal to the minimal epilating dose of 400 rads of 200-kVp x rays. 4&. Internal Doses Internal absorption of radiounclides was due to inhalation as the radioactive cloud passed over and to ingestion of food and water contaminated with fallout, water probably being a maior source. Drinking water is: obtained by collecting rainfall from the roofs into catchments, and a slight rain was reported on Rongelap the night of the fallout. Since the cisterns vere almost empty, the dilution effect was minimal. Water was being rationed at that time, and it was drunk in spite of warnings from the health aide. On Rongerik food and water were better protected from fallout deposition. internal levels of radionuclides absorbed from the fallout were assessed by numerous radiochemical analyses of urine samples, beginning 15 days post - lll -