---- NX counts 8 males exposed at <5 vrs oid — Count on No 34 exposed at [ vr old AML 1972) 03 —--~ Unexposed males of same age WBC x 10 F interesting that radiochemical analvsis of bone samples showed 9Sr levels about the sameas in people living in New York. Retrospective study ofhematological data. The hema- tological data gathered over the 18-year period on 22 =x = 7 64 = = \ 24) depression of neutrophils both during the immedi- zo ate post-exposure period and in subsequentvears. Theleast difference appeared to be in the erythropoietic system. Morphological studies of peripheral Be Zo 1 f-—- Months —+— > = x Years Timeafter exposure + eo ; e OF —-— Unexposed males of same age — 7 1 3» 7777 Mcounts on 8 males exposed at C5 yrsold | + L 4| ? Counts on No. 34 exposed at | yr old (AML 1972) gon - 2 \ASe x | aed i- - = 40* yee. 30H blood smears revealed no significant abnormalities until the developmentof leukemia; unfortunately no bone marrow examinations had been made before. Since the Marshallese children are pronetofrequent infections associated with granulocytosis,it was of interest to comparethis response in the subject with leukemia andin the other exposed bovs. The records showed that the white ceil countexceeded 10,000 a total of 36 times in 131 counts (27%) in the other 8 exposed boys and onlv once 0 45- - the subject with leukemia (No. 54) were compared with the meanlevels of 8 other Rongelap boysexposed at <5 vears of age and of 8 unexposed bovs in the same age range (Figure 52). The percentage differences in mean peripheral blood levels between subject No. 34 and his exposed peers are given in Table 36 for the first year and for the subsequent years. The subject with leukemia showed greater 1 i 2 61 a » Months + pi 4 2 . 8 1 12 Years Timeafter exposure wo 16 4 BRI ! 30% —-— Unexposed males of same age Neut lymph 23d a---- X of males exposed at <5 yrs old i No. 54 exposed att vr old (AML 1972) |Monthsk Years Timeafter exposure — Figure 32. Mean levels of WBC, Ivmphocytes, neutrophils, platelets. hematocrit, and neutrophil /‘lvmphocyte ratio for subyect with leukemia (No. 54. solid line in each case) compared with those of exposed (--—) and unexposed | — —- —) bovs in sameage range, over 18 years since exposure. in 18 counts (5%) in subject No. 54. However, if this indicated a reduction in marrow reserve in this boy, the reduction apparently was insufficient to result in any illness serious enough to require hospitalization. Other data related to leukemia were generally negative in subject No. 54, includingalkaline phosphataselevels of neutrophils, basophil counts, Australia antigen, and blood proteins (except for a slightly elevated gamma globulin level, which is common in the Marshallese). Chromosomestud- ies of the peripheral blood made 12 years after exposure and of the bone marrow during his terminal illness did not show aneuploidy or structural changes of the chromosomes. However, increased chromosomebreakage (11% of the cells) was noted terminally, which may have been related to radiation exposure to chemotherapy, or possibly to his disease. Discussion. It is possible that radiation exposure was involved in the etiology of leukemia in subject No. 54. Radiation exposure has long been associated with the developmentofthis disease (in physicians, particularly radiologists,!#?-148 in pa-