73 probably with less internal absorption of radionu- clides, since their stored water and food were cov- ered, and they have had nothyroid effects (see Appendix 2). Evaluation of the effects of radiation exposure in humanbeings (patients, physicians using radiation, accident cases, etc.) is always difficult because of uncertainties regarding exact dosage,fractionation and dose-rate effects, partial-body exposure, complicating diseases, etc. The doses received by the Marshallese, like most human exposures, could be only roughly estimated, although the hematological data were compatible with thecalculated whole-body doses. Even greater uncertainties were encounteredin estimating the doses due to internal absorption of radionuclides. The data on the effects of fallout radiation in the Marshallese have provided important information that will apply in a general way to any population exposed acutely to fallout. However, the effects may be modified in othersituationsif nuclear explosions occur in regions with different terrain, soil types, climate, and availability of protective measures. C. ACUTE EFFECTS The most serious acute effects of the exposure in the Marshallese were due to penetrating gam- ma radiation. These included transient anorexia, nausea, and vomiting andsignificant depression of the peripheral blood elements in many members of the higher exposure Rongelap group. The hematological depression was not sufficient to produce definite clinical signs and required no specific therapy. Contamination of the skin in the Rongelap group resulted in wide-spread beta burns on parts of the body not covered by clothing and in spotty epilation of the scalp. These effects were probably aggravated by delay in decontamination and by perspiration due to the warm climate causing the fallout to stick to the skin. The superficial nature of the lesions, rapid healing with minimalresidual skin changes, and regrowth of hair were no doubt due to the low average energy of the beta radiation in the fallout. Thelack of recognizable acute effects from the internal absorption of radionuclides is noteworthy in view of the serious thyroid abnormalities that later developed. Because of residual contamination ontheislands, radiological monitoring of personnel and environment has been an importantpart of the surveys in evaluating body burdens of radionuclides in the Rongelap and Utirik »eople. Recently the areas undergoing such monitoring have includedBikini Atoll and the people who have returned to live there, and theywill also include Eniwetok when its people return home. D. LATE EFFECTS The possible emergenceof late effects of exposure in the Marshallese has received considerable attention in follow-up examinations. Exceptfor the thyroid lesions and the one case of leukemia, only a few findings possibly related to radiation exposure have been seen; otherwise the general incidenceofillnesses and the overall physical condition have been similar in the exposed andin the unexposed comparison groups. The increase in miscarriages andstillbirths among the exposed Rongelap women duringthefirst 5 years after exposure may or may not have been related to radi- ation effects. No genetic effects have been noted in the children born of exposed parents; this is not surprising in view of the generally negative findings in the much larger Japanese study. Thefindings of persistent chromosome aberrationsin cultured peripheral blood lymphocytes at 10 vears post exposure and a possible somatic mutation in hemoglobin in several of the exposed group suggest that genetic mutations mayalso be present. The possibility of genetic effects in the offspring is of serious concern to the exposed people and deserves further study. Effects of radiation onlife shortening or mortal- ity are difficult to evaluate because of the small numberof people and the differences in age distribution between the exposed and comparison groups. The only death that mayberelated to exposure is that from leukemia. The occurrenceof a few additional cases of cancer (other than thyroid) cannot be ascribed definitely to radiation exposure. The lack of skin cancer from beta burns may be related to the minimal natureofthe residual skin changes, probably dueto insufficient radiation injury to the dermis, but the possibility of skin cancer developing must be kept in mind because the latent period may be very long. The developmentof a case of acute leukemia in the Rongelap boy may or may notberelated to radiation exposure. However, this disease appears to be even rarer in the Marshall Islands than in the U.S. It is noteworthy that his disease was the