Table 1 Grouped values (+ SD) of hematologic data obtained from persons who had 400-cell leukocyte differential counts in 1981. Using analysis of variance andt-tests, no significant differences were found among the exposure groups or between exposed groups and the comparison population. Monocytes/pl Basophils/p1 Mean Corpuscular Volume(fl) Rongelap(46) 3544139 338+ 166 3754167 9.3421 7.7417 11.6420 91.745 14.24+1.6 Comparison (103) 3864177 10.8+21 90.0+5 14.2+1.4 Exposure Group(n) Ailingnae (13) Utirik (108) for mean corpuscular volume and hemoglobin level, also from 1981, are shown in the same table. In 1982 the following special tests were performed: serum erythropoietin assays were obtained on many individuals, including all those with elevated or high-normal hemoglobin levels, using a sensitive radioimmunoassay, and serum calcium andserum protein levels, as well as serum protein electrophoresis, were done on all exposed individuals. Theresults are discussed below. Monocytes. The normal monocyte concentration in peripheral blood is approximately 300/u1 with an upper limit of normal of about 800/ ul.” Values abovethis could be 1) occasionally normal; 2) the result of statistical variabil- ity inherent in a differential count; 3) due to.a variety of infectious and granulomatous diseases; and 4) an accompaniment of a malignant process, including preleukemia. Mean values were similar in all exposure groups. Using analysis of variance andt-tests, significant differences were not found amongthe four exposure groups or between exposed groups and the comparison population. Four persons from Utirik and two from the comparison population had counts exceeding 800/,1. All but one(a person from Utirik who hasnot presented for reexamination) were normal whenretested. _ Basophils. These cells normally numberless than 200/,y1, with a mean of 40/1. Basophiliais often seen in the various myeloproliferative syndromes. There werenostatistically significant differegces among the exposure groups. The highestggrecorded 120/,1, was in the unexposed popul#tion. 90.4+5 88.945 Hemoglobin (g/dl) 13.94+1.2 14.2+1.7 Mean Corpuscular Volume (MCV). An increase in the size of erythrocytes is most often due to alcoholism ora deficiencyof folic acid or vitamin Bie. It can also be seen with aplastic anemia, sideroblastic anemia, preleukemia, and occasionally with solid tumors. There were no statistically significant differences in MCV among the exposure groups. The upperlimit of normalfor the MCVis about 100 ff. In 1981 one person from Rongelap, a 70-year-old woman, exceeded this (MCV of 102 fl). Her serum Biz level was found to be low (108 pg/m)), although intrinsic factor antibodies were absent. She was started on parenteral vitamin Bye. Hemoglobin. There were no statistically significant differences in mean hemoglobin level among the exposure groups. The upperlimits of normal in Marshallese have been found to be approximately 17.7 g/dl for men and 15.7 g/dl for women. These are identical to values found in a normal U.S. population.’ Polycythemiais seen most often in heavy smokers, but it can also occur with the myeloproliferative syndromesand certain solid tumors, particularly those of renal or hepatic origin. Polycythemia vera, amyeloproliferative disorder, characteristically has a depressed level of serum erythropoietin. No low levels were found in any person tested. High erythropoietin levels are characteristic of the polycythemias due to solid tumors. No high levels were found in any nonanemic individual. ’ Serum Calcium. Hypercalcemia (serumcal- cium > 10.5 mg/dl) can be caused by, among other things, parathyroid adenomas and mariy malignantdiseases, usually metastatic tumors.