57 mass and/ortotal blood volume with total body Rongelap as a result of their fallout radiation ex. posure. Attempts at 8 and 9 years post exposure to obtain suitable blood cultures had not been entirely successful. However, during the 10-year survey a slight modification of the Moorehead technique”® resulted in a series of satisfactory cultures on 51 people: 30 in the higher exposure weight used asa baseline. During the 1963 survey, similar studies were performed on 21 Marshall Islanders, but these data were related to total body water as determined bytritiated water.” Results showed thatin all instances but one the ‘values for red cell mass andtotal blood volumefell below normallevels for persons living in temperate zones of the United States. The present study was undertaken during the surveys in 1965 and 1966. total of 19 Caucasian Americans (3 females and 16 males) living in the MarshallIslands for periods of 3 monthsto 9 years were examined by the same techniques.* Theresults of these studies on each individualare presented in Appendix 15, along with data on the 21 group (175 rads), 13 in the lower exposure group (69 rads) and 8 from the unexposed Rongelapese who were on anotherisland at the time of the accident. The detailed results of these studies are presented in Appendix 14.* Table 25 summarizes the results. A higherincidence ofaneuploid cells was noted in the exposed group, but the difference was not great enough to be significant. Unexpectedly, the lower exposure group showed more aberrations than cid the more heavily exposed group,andthelatter group showed even less aberrations than the unexposed. However, the incidence of 2-hit aberrations was significantly higher ( p <0.004} in the exposed groups Marshallese in whom these studies were carried out in 1963. The data were programmed and analyzed by a high speed digital computer. Re- gression lines obtained for the Caucasians and the Marshallese are presented in Figure 67 along with regression lines ofMoore”* andSiri’’ 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 chromosomespreadsfrom two exposedindividuals. voiume and red cell colume have very nearly the same slopes as the lines of the Siri and Moore Total Blood Volume and Red Cell Volume groups, but theyare significantly below thelatter (significant at the 1% level). The Caucasiansliving in the Marshall Islands also show regression lines Previous studies (1961, 1962) with *'Cr-labeled erythrocytes on Marshallese subjects living in their slopes similar to those of the Marshaliese and the OTHER LABORATORY STUDIES for blood volumeand red blood cel! volume with Siri and Moore groups. Comparison ofthe regres- native environment have shown reducedredcell sion lines showsnosignificant difference between *We are grateful to Dr. Shields Warren and his groupat the CancerResearch 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 ChromosomeFindings No. of persons with aberrations Chromosomeaberrations Fragments Dicentrics 12 11 6 - 5 No. of persons No.of cells scored Percent ofcells with 2n3446 Exposed 30 1500 10 Exposed 69 rads 13 650 8 11 (84.6%) 10 2 1 8 400 5.5 > (62.5%) 9 - - Group 175 rads Unexposed (40%) Total aberrations Total cells with aberrations 22 20 43 | 15 8 21 (3.23%) 18 (2.77%) 31 4 - 9 (2.25%) 8 (2.0%) 6 3 . ExRings changes (1.46%) (1.33%) ChroIsomatid chromatid breaks gaps