38 high incidenceof diabetes. Serum assayfor vitamin lese people has been complicated by several things. The people were evacuated from their island soon This studyof the internal contamination of the Marshallese has provided information (1) on the movement of Cs'**, Zn**, and Sr®® from the environment to man; (2) on the rate of equilibration of these isotopes with the environment; and (3) on the discrimination factors between food and man. taminating event, additional weapons tests held IMPORTANCE OF MEDICAL SURVEYS B,,. showed genegally high levels; the explanation was not apparent. Radionuclide body burden evaluation in the Marshal- after the accident and did not return until 3 years later. During the 5 years since the original con- in the area have contributed to the fission products in the environment. Finally, since the diet includes a variety of imported foods, the people are not living in a “closed” environment, and therefore may not be rapidly approaching equilibrium with the environmental fission products, as might be expected under other circumstances. Body burdens of gamma-emitting fission prod- ucts (such as Cs'*7 and Zn**) were measured ina whole-body counter and checked by radiochemical analysis of urine specimens. Body burdensof Sr°° were estimated from urinary excretion as determined by radiochemical analyses. Both the external dose measurements on Rongelap Island and the levels of radioactive isotopes in the food on the island indicated that some increase in Cs'*7, Zn**, and Sr°® body burdens wasto be expected when the people returned there in 1957. The Cs'** body burden in 1958 was about 0.68 uC, about 60 times as great as in 1957, and the urinary Cs'*? level rose by a factor of 140; the mean body burden for 1959 was 0.57 uC. The mean body bur- den of Zn® estimated from whole-body counting data was, in 1958, after the return to Rongelap, 0.36 uC, 8 times as high as in 1957, and 0.44 pC in 1959. Thus, whereas the Cs'*’ levels appear to have reached a maximum and actually to have dropped in 1959, the Zn* levels have showna continued increase which is probably related to the long biological half-life of the latter. The Sr’° level in 1958 estimated from excretion data was 2 mp, about 20 times as high as in 1957 before the return to Rongelap. The estimated body bur- den in 1959 increased to 6.0 mpC, about 20% of the estimated ultimate equilibrium value, Little of the body burden of the exposed group is apparently due to their initial exposure, since At present thereislittle difference betweenthe levels The Japanese populations of Hiroshima and Nagasaki being studied by the Atomic Bomb Casualty Commission and the Marshallese population of Rongelap comprise the only large groups of people exposed to acute doses of ionizing radia- tion. The two studies parallel each otherbutdiffer in certain important respects. The smaller number of people in the Marshalles: sopulation and the paucity of vital statistics maxe statistical analysis of data on this group much moredifficult. However, the Marshallese studies have the advantages that the dose of radiation received by the people is better known; that the findings during the early, acute period after exposure are well documepted; and that the people did not suffer from trauma, thermal burns, or marked psychic disturbance, although they did have the complications of beta burns andinternal absorption of radionuclides. Study of both groups has yielded valuable information on the acute effects in human beings of radiations from atomic bomb detonations. Examinations for the more subtle late effects of radia- tion exposure are now receiving considerable em- phasis. In the case of the Japanese, increased incidence of leukemia and possibly other malignancies as well as cataracts already has been reported. In view of this finding, the next 5 years will be the critical period for the development of leukemia in the Marshallese. Animal experimentation has indicated the possibility that still other late effects may occur in the human being such as premature aging, shorteningof life span, increase in degenerative diseases, genetic changes, etc. Therefore, con- tinued careful examination of these populationsis extremely important in order that such effects may be documented, and therapeutic procedures instituted wherever possible, should such effects of the exposed and unexposed populationsliving develop. In addition, in the case of the Marshal- have reached their estimated equilibrium values, fluence of persisting low levels of radioactive materials on Rongelap Atoll on the body burdens of radionuclides of the people living there. on Rongelap Island. When these three isotopes the body burdenswill still be of small significance in terms of radiation hazard. lese, continued evaluation Is indicated of the in-