a PLATELETS x 10°/ pI 3 RONGELAP Figure 7. AILINGNAE UTIRIK CONTROL Individual platelet counts beyond the range 120,000 to 372,000/y1. (See legend for Figure 5.) from the mean for leukocytes and platelets and less than two standard deviations below the mean for hemoglobin. As shown in Table 2, the occurrence of values exceeding these limits was not significantly more frequent in radiation-exposed groups than in the comparison population, but again there were tendencies toward variation on the basis of sex. The increased platelet concentration in females, regardless of group, has already been mentioned. Low platelet or leukocyte concentrations were infrequently observed in both sexes and were rarely persistent, and probably resulted from technical errors (Figures 5, 7). Relative leukocytosis occurred in one~quarter to one-third of all groups studied (Figure 5). Hemoglobin concentration above 17.2 g/dl occurred only once in a single female out of an average of more than 150 studied on seven occasions during the five-year period, whereas approximately one-third of the men, both control and radiation-exposed, exhibited a relative erythrocytosis (Table 2, Figure 6). Anemia, on the other hand, if defined as hemoglobin concentration below 12.0 g/dl, was several times more frequent in the female populations than in their male counterparts (Table 2, Figure 6), especially in younger women. It is notable that lowered hemoglobin occurred twice as frequently (73%) in the CD la c- C4 ory co control population as in the exposed female groups (36% of those on Rongelap, 28% of those on Utirik). A tendency toward microcytosis has been noted previously in these women, but serum iron concentrations and reticulocyte counts have been normal, and vitamin B,9 levels have been considerably elevated (7). Despite the frequency of mild anemia by hemogram criteria, symptoms or signs of clinically significant anemia were rare. Previous studies have also indicated that total blood volume and red cell mass may be generally lower in -— 2? =-