37 Rongelapas a result of their fallout radiation ex- mass and/or total blood volumewith total body weightused as a base line. During the 1963 survey, similar studies were performed on 21 Marshall posure. Attemptsat 8 and 9 years post exposure to obtain suitable blood cultures had not been entirely successful. However, during the 10-year Islanders, but these data were related to total survey a slight modification of the Moorehead technique’® resulted in a series of satisfactory cultures on 51 peopie: 30 in the higher exposure group (175 rads), 13 in the lower exposure group (69 rads) and 8 from the unexposed Rongelapese who were on another island at the time of the accident. The detailed results of these studies are presented in Appendix 14.* body water as determined by tritiated water.'° Results showedthat in all instances but one the values for red cell mass and total blood voiumefell below normallevels for persons living in temperate zones of the United States. The present study was undertaken during the surveys in 1965 and 1966. A total of 19 Caucasian Americans (3 females and 16 males) living in the Marshall Islands for periods of 3 monthsto 9 years were examined by the same techniques.* Theresults of these studies on each individual are presented in Appendix 15, along with data on the 21 Marshallese in whom these studies were carried out in 1963. The data were programmed and analyzed by a high speed digital computer. Re- Table 25 summarizes the results. A higher in- cidence of aneuploid cells was noted in the exposed group, but the difference was not great enoughto be significant. Unexpectedly, the lower exposure group showed more aberrations than did the more heavily exposed group,and the latter group showed even less aberrations than the unexposed. How- gression lines obtained for the Caucasians and the ever, the incidence of 2-hit aberrations was significantly higher ( p <(0.004) in the exposed groups Marshallese are presented in Figure 67 along with regression lines of Moore” and Siri" for Americans. The Marshallese regression lines for both blood and did appearto be radiation induced. Figure 66 shows a dicentric and a ring form noted in chromosomespreads from two exposed individuals. volume and red cell colume have very nearly the same slopes as the lines of the Siri and Moore groups, but they are significantly below thelatter (significant at the 1% level). The Caucasiansliving in the Marshall Islands also show regression lines for blood volumeand red blood cell volume with slopes similar to those of the Marshallese and the Siri and Moore groups. Comparison ofthe regression lines showsno significant difference between OTHER LABORATORY STUDIES Total Blood Volume and Red Cell Volume Previous studies (1961, 1962) with °'Cr-labeled erythrocytes on Marshallese subjects living in their native environment have shown reduced redcell *We are grateful to Dr. Shields Warren and his group at the Cancer Research Institute in Boston for carrying out the chromosome analyses. *Weare grateful to Dr. W_E. Siri, University of California. for carrying out the tritium-water analyses. Table 25 Summary of Chromosome Findings Group No. of persons persons cells scored with 2n46 aberrations No. of of cells Exposed 30 1500 10 Exposed 69 rads 13 650 8 8 400 5.5 175 rads Unexposed No. of Percent with Chromosomeaberrations Fragments Dicentrics 12 Lt 6 - 5 11 (84.6%) 10 2 1 8 9 ~ - - (40% ) 5 (62.5%) ExRings changes Total Total aberrations 22 cells with aberrations Chro- Tso- matid chromatid breaks gaps (1.46%) (1.33%) 20 43 15 21 (3.23%) 18 (2.77%) 31 + 6 5 9 (2.25%) 8 (2.0%)