73 probably with less internal absorption of radionu- clides, since their stored water and food were covered, and they have had no thyroid effects (see Appendix 2). Evaluation ofthe effects of radiation exposure in human beings (patients, physicians using radiation, accidentcases, 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 the calculated whole-body doses. Even greater uncertainties were encountered in estimating the doses due to internal absorption of radionuclides. The data on the effects of fallout radiation in the Marshailese have provided importantinfor- mation that will apply in a general way to any population exposed acutely to fallout. However, the effects may be modified in othersituations if 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- maradiation. These included transient anorexia, nausea, and vomiting and significant depression of the peripheral blood elements in many members of the higher exposure Rongeiap group. The hematological depression was not sufficient to producedefinite clinical signs and required no specific therapy. Contamination of the skin in the Rongelap groupresulted in wide-spread beta burns on parts of the body not covered by clothing and in sporty 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 minimal residual skin changes, and regrowth of hair were no doubt dueto the low average energy of the beta radiation in the fallout. The lack of recognizable acute effects from the internal absorptionof radionuclides is noteworthy in view of the serious thyroid abnormalities that later developed. Because of residual contaminationontheislands, radiological monitoring of personnel and environment mw’ an importantpart of the surveys in I0Cb1 10 evaluating body burdens of radionuclides in the Rongelap and Utirik people. Recently the areas undergoing such monitoring have included Bikini Atoll and the people who have returned to live there, and they will 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. Except for the thyroid lesions and the onecase 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 maynot have beenrelatedto 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. The findings of persistent chromosomeaberrations in cultured peripheral blood lymphocytes at 10 years 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 offspringis of serious concern to the exposed people and deserves further study. Effects of radiation onlife shortening or mortality are difficult to evaluate because of the smail number of 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 occurrence of 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 natureof the residual skin changes, probably dueto insufficient radia- tion 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 developmentofa case of acute leukemia in the Rongelap boy may or maynot berelated 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