11 diation, but the caustic nature of the fallout may have contributed. The G.I. symptoms in the Rongelap people consisted of anorexia and nausea (in about twothirds of them) and to a lesser extent of vomiting and diarrhea (in one-tenth of them). Onlv a few in the Ailingnae group complained of these symptoms, and no one in the Rongerik and Utirik groups. The gammaexposure is thoughtto have been sufficient to accountfor the G.I. symptoms, but the ingested radioactive material (estimated at about 3 mCi) may have contributed. The G.I. symptoms were more prevalent in the Rongelap children (see Table 4). These symptomslasted only about two days and had largely disappeared bv the time the people arrived at Kwajalein. b. Depression of Blood Elements. The early 14 rads, it was possible to distinguish slight platelet depression in the group as a whole. The smaller groups on Ailingnae and Rongerik showed peripheral blood levels between those of the high and low exposure groups. The hematological depression was thought to be due entirely to gamma radiation, since it was not considered likely that the dose from internally absorbed radionuclides contributedto it significantly. The hematological depression was greater in the children, particu- larly those exposed at <5 years of age (see Table 5). The changes are enumerated below in more detail. Lymphopenia to about half the level of the comparison Marshallese population was evident when the Rongelap people werefirst examined 3 days after exposure. In children <5 years of age the lymphocytes dropped to 25% ofthe level of the comparison children but showeda slight rise during the following weeks. The lymphocyte levels hematological findings and the findings in subsequent vears are presented in tabular form in Appendix 6 and graphically in Section III. C. The early findings are summarized here andthelater ones in Section ITI. C. Oneofthe earliest findings in the Marshallese indicative of significant exposure was lowering of leukocyte and platelet levels in the peripheral blood. This was most marked in the 64 people on Rongelap who kad received 175 rads andless so in other groups receiving less exposure. The hemopoietic depression was roughly proportionalto the gammadoseof radiation received. Even in the 137 Utirik people who received only an estimated Neutrophil levels showed considerable fluctuation during the first month, possibly related to the prevalence of beta burns of the skin during that period. Neutrophil depression became evident by 5 to 6 weeks post exposure, the level dropping to abouthalf the controllevel in adults andslightly lowerin children aged <5 (Table 5). Neutrophils recovered more rapidly than lymphocytes and Table 4 of recovery to about 75% of control levels occurred Nausea and Vomiting in Rongelap Group?? Incidence, % Age at exposure, vr No. Nausea Vomiting <3 26 13 51 85 44 38 4 Table 5 Mean Blood Counts at Peak Depression in Rongelap Group”? Percentof control Neutrophils Lymphocytes Platelets Age <5 Age >3 36 25 23 64 55 34 showeda slight increase by one year. reached nearcontrol levels by one year. Early platelet counts showed less fluctuation than other blood counts and decreased to about 30% of control levels by the fourth week. A spurt during the next few weeks, followed by slower recovery with mean levels never exceeding 90 to 95% of control levels during the first year. The platelet count is probably the most sensitive index of the severity of radiation exposure in the sublethal range. Erythropoetic depression has not been a consistent finding, and radiation effects on these cells have not been demonstrable by peripheral blood counts. Morphological changes. During the period when neutropenia was most severe, some people were found to have peculiar monocytic leukocytes that were thoughtto be large lymphocytes. Thesecells were not found subsequently, although an occasional binucleated lymphocyte was seen. ¢. Clinical Findings. The developmentofsignificant depression of peripheral blood leukocytes andplatelets during the first 6 weeks was causefor’ considerable apprehension among the medical