a en te al cell mass and/or plasma volume. However, there among the older group. This creates certain diffhculties in interpreting someof the studies to be outlined. 4, The conditionsof field examinations naturally limit the procedures and methods that can be used. establish the relationship of blood volume to lean COMPARISON POPULATIONS Blood volume studies with °*'Cr-labeled sodium chromate showeda significant reduction in red is some indication that Americansliving in the Islands for more than 1 year mayalso haveslightly lowered values. Tritiated water has been used to ‘body mass. Further studies on blood volume determinationsare presented later. OTHER BACKGROUND INFORMATION As mentioned in previous reports, several difficulties were associated with carrying out the examinations 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 medi- ~ cal data. Trust Territory officials are attempting to improve registration of such data. 3. There is uncertainty on the part of someof the Marshallese as to their exact ages, particularly Duringthefirst 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 12 months the Rongelap population at Majuro Atoll had doubled becauseofthe 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 comparablesize. 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 Frequency living (1966) of exams Subject Nos. Exposed Rongelap* Ailingnae** Uutirik 67 38 157 133 99 168+ 19 Annual 13 Annual 3-4 vears l- 1- 86 86 2101-2257 Unexposed Rongelap Rita Mayjuro 57 115 ‘ Annualsince 1957 1955-1956 1954 only 801-1073 1000-1082 700- 800 Children Conceived After the Fallout Of exposed parent(s) Of unexposed parents *Includes 3 un” utero children. **Includes | zn utero child. 5008252 63tT 60 104 Annual Annual 87- 151 801-1073 tIindividuals have been added since 1957 when this group was first available. tt Live births.