Blood volume studies with °'Cr-labeled sodium chromate showeda significant reduction in red among theolder group. This creates certain difficulties in interpreting someofthestudies to be outlined. Islands for more than | year mayalso haveslightly lowered values. Tritiated water has been used to establish the relationship of blood volumeto lean body mass. Further studies on blood volume determinations are presentedlater. limit the procedures and methods that can be used. cell mass and/or plasma volume. However, there is some indication that Americans living in the OTHER BACKGROUND !NFORMATION As mentioned in previous reports, several diffi- culties were associated with carrying out the ex- aminations as well as interpreting the findings. 1. The language barrier made examinations difficult, since very little English is spoken by the Marshallese. However, there were sufficient En- glish-speaking Marshallese to assist the medical team in most instances. 2. The lack of vital statistics or demographic data on the Marshallese imposes a serious difficulty in interpretation and evaluation of the medical data. Trust Territory officials are attempting to improve registration of such data. 3. There is uncertainty on the part of some of the Marshallese as to their exact ages, particularly 4. The conditions of field examinations naturally COMPARISON POPULATIONS During the first 2 years, two separate groups of Marshallese people were used for comparison, each comparablein size with the exposed Rongelap group and matchedfor age and sex. However, both groups were found to be unstable, with a large attrition rate over the 2 years, which made them unsatisfactory. At the time of the 3-year survey, it was found that during the preceding [2 months the Rongelap population at Majuro Atoll had doubled because of the influx of relatives who had come back from otherislands to live with them. These people had been away from Rongelap Atoll at the time of the accidental exposure. This group matched reasonably well for age and sex and was of comparable size. Since the return of ~ the people to Rongelap, however, this group has about doubled in size. Table 2 shows the various Marshallese populations that have been examined since 1954. Table 2 Marshallese Populations Examined Since 1954 Group Original number in group Number living (1966) Frequency of exams Subyect Nos. Exposed Rongelap* Ailingnae** Uurik 67 19 157 58 15 133 Annual Annual 3-4 years I- 8h L- ah 2101-2257 99 37 Li5 L68f Annual since 1957 1955-1956 1954 only 801-1073 1000-1082 700- BOO 60 104 Annual Annual Unexposed Rongelap Rita Majuro Children Conceived After the Fallout Of exposed parent(s) Of unexposed parents *Includes 3 zn” utero children. ** Includes | in utero child. 63tt B7- | vl BO1-1074 +Individuals have been added since 1957 when this group wasfirst availuble 7tLive births.