according to the mode of exposure: penetratingir- radiation,skin irradiation, and internalirradiation. PENETRATING RADIATION Oneof the earliest findings indicative ofa significant exposure in these people was lowering of levels of leukocytes and platelets of the peripheral blood. This was most markedin the 64 people on Rongelap who had received 175 rads, and was less markedin the other groupsreceiving less exposure. The hemopoietic depression was roughly proportionalto the dose of radiation received. Even in the 157 Utirik people who received only an estimated 14 rads, it was possible to distinguish slight platelet depression in the group as a whole. The smaller group on Ailingnae and Rongerik showed peripheral blood levels between those of the high and low exposure groups. The chronological records of blood findings on the group exposed on Rongelap are presented in Figures 49, 50, 56, and 65 and Appendix 8, and on the Ailingnae and Utirik groups in Appendices 9 and 10. Lymphopenia of about half the level of the comparison Marshallese population was evident when the people exposed on Rongelap-werefirst examined on their arrival at Kwajalein 3 daysafter exposure (see Figures 49, 50, and 65). In children <5 vears of age the lymphocytes dropped to 25% of the levels in the comparison children, but showeda slight rise during the following weeks. The lymphocyte level showed slight increase by ! year. In the following year mean counts ap- proachedthelevels of the comparison population but remainedslightly below (see Figures 50 and 65). Neutrophil levels Auctuated considerably during the first month; possibly this was related to the prevalence of beta burnsof the skin during that period. Neutrophil depression became evident by 5 and 6 weeks post exposure (see Figures 49 and 65), with levels reaching about half that of the comparison population in the adults andslightly 9008281 Erythropotetic depression has not been a consist- ent finding as with the leukocytes and thrombocytes. Slight depression of red blood counts, hematocrits, and hemoglobin has been noted at times. Bone marrow smears taken at 6 months showed no gross abnormalities. Smears takenat8, 9, and 10 years showed an alteration in the myeloid-erythroid ratio manifested by an increased numberofred cell precursors. Depression of peripheral blood elements in the Ailingnae and Rongerik groups was not so pronounced as in the Rongelap group. However,a slight lag in complete recovery in the Ailingnae peripheral blood count has also been noted. The persistent depression of peripheral blood elements in the exposed people makesit appearlikely that there is slight residual bone marrow damage. A general anemic tendency has been evident in both exposed and unexposed Marshallese. PriceJones curves, on the average, showed slight microcytic tendency. Serum iron levels have been generally normal, and the cause of this anemic tendency has been undetermined. Reticulocyte counts have been aboutthe samein the exposed as in the unexposed people. Clinical findings, except for radiation-induced Jesions of the skin, patchy epilation, and early gastrointestinal symptoms, revealed no clear-cut disease processes or symptomswhich could bere- Mee sie at surable amounts of radioactive material had also been absorbed internally. The effects of the radiation can best be summarized under three headings it was noted that neutrophilic leukocytosis was possible in people showing casualinfections at this time. Neutrophil levels recovered more rapidly than lymphocyte levels and reached near control levels by | year. Subsequent annual surveys have revealed that recovery does not appear to have been complete, particularly in younger and older age groups, during the 10-year period. Early platelet counts showed less fluctuation than other blood counts andfairly consistently showed increasing depression, reaching levels of about 30% that of the comparison population by the 4th week. A spurt of recovery to about 75% of comparison levels occurred duringthe following few weeks, which was followed by slower recovery but with mean levels never reaching higher than 90 to 95% that of the comparison population during the 10 years post exposure (see Figures 56 and 65). TEE RC NIE ROE ARIpe LEI teepot ageing erante nap ee chemical analyses of the urine showed that mea- parent increased infectious processes, and, indeed, rae ation and the beta irradiation of the skin, radio- lowerin the children <5 years of age. This degree of neutropenia was insufficient to result in any ap- CPPoke WER ie phocytes were considerably depressed and thatsignificant doses of radiation had probably been received. In addition to the whole-body doseof radi-