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 lesser extent of vomiting and diarrhea (in one-tenth of them). Onlya few in the Ailingnae group complained of these symptoms, and no one in the Rongerik and Utink groups. The gamma exposure is thoughtto have been sufficient to account for 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 symptoms lasted only about two days and hadlargely disappeared bythe time the people arrived at Kwajalein. b. Depression of Blood Elements. The early hematological findings and the findings in subsequent years are presented in tabular form in Appendix 6 and graphically in Section III. C. The early findings are summarized here and the later ones in Section III. 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 markedin the 64 people on Rongelap who hadreceived 175 rads andless so in other groupsreceiving less exposure. The hemopoietic depression was roughly proportionalto the gamma doseof radiation received. Even in the 157 Utink people who received only an estimated Table 4 Nausea and Vomiting in Rongelap Group?? Incidence, % Age at exposure, yr No. Nausea Vomiting <5 26 13 51 85 44 38 4 . Table 5 Mean Blood Counts at Peak Depression in Rongelap Group?? Percent of control Age <5 Neutrophils Lymphocytes Platelets 56 25 23 Age >5 64 55 34 14 rads, it was possible to distinguish slight platelet depression in the group as a whole. The smaller groups on Ailingnae and Rongerik showed periph- eral 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 contributed to it significantly. The hematological depression was greater in the children, particularly those exposed at <5 years of age (see Table 5). The changes are enumerated below in moredetail. Lymphopenta 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% of the level of the comparison children but showed slight rise during the following weeks. The lymphocyte levels showed a slight increase by one year. Veutropht \evels showed considerable fluctuation during the first month, possiblyrelated to the prevalence of beta burns of the skin duringthat period. Neutrophil depression became evident by 5 to 6 weeks post exposure, the level dropping to about half the control level in adults andslightly lower in children aged <5 (Table 5). Neutrophils recovered more rapidly than lymphocytes and reached near control 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 of recovery to about 75% of control levels occurred 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. Erythropotetic 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. These cells were not found subsequently, although an occasional binucleated lymphocyte was seen. c. Clinical Findings. The development ofsignificant depression of peripheral blood leukocytes and platelets during the first 6 weeks was cause for considerable apprehension among the medical