6 since the original contaminating event, additional weaponstests held in the area have contributed to the fission products in the environment. Since the diet includes a variety of imported foods, the people are notliving in a “closed”environment, and therefore may not be rapidly approaching equilibrium with the environmentalfission products, as might be expected underother circumstances. Body burdens of gamma-emittingfission products (such as Cs'*" and Zn**) were measured in a whole-body counter and checked by radiochemical analysis of urine specimens. The levels ofinternal contamination per unit weight appeared to be about the samefor juveniles as for adults, male and female. Wide variations in levels of contamination in any group were found, apparently due to differences in diet and metabolism. Body burdensof Sr®*° were estimated from urinary excretion as determined by radiochemical analyses. Both the external dose measurements on Rongelap Island and thelevels of radioactiveisotopes in the food on the island indicated that some increase in Cs**", Zn**, and Sr®° body burdens was to be expected when the people returned there in 1957, The Cs'** body. burden in 1958 was about 0.68 nC, about 60 times as great as in 1957, and ’ the urinary Cs'*" level rose by a factor of 140; the mean body burden for 1959 was 0.57 pC. The mean body burden of Zn® estimated from wholebody counting data was, in 1958, after the return to Rongelap, 0.36 uC, 8 times as high as in 1957, and 0.44 uC in 1959. In 1961 the mean Cs'*” body burdenin adult males was 14.7 myC/kg, whichis not significantly different from the mean value of a similar group obtained in 1959; it was 300 times that of the medical team, who were measured at the same time for comparison. The Zn® level in adult males (1.51 mpC/kg) dropped to 17% of the mean value measured in 1959. With a larger de- tector and a longer counting time than previously employed,it was possible to identify and quantify Co®° for the first time in these people; the mean level of Co®® was about 11% of the Zn® level. A small amountofresidual activity wasstill present after the subtraction of K*° and the above radionuclides from the total spectrum. The mean level of urinary excretion of Sr®° was 7.2 pC/I| or 14% higher than measured in the 1959 medical survey. In 1962 the mean urinary Sr® level was 114 pC/g Ca, giving an estimated body burdenof 12.0 mpC. Analysis of bones from the deceased Ron- gelap woman (1962) gave an estimated body 90001384 burden of 11.4 myC. Theselevels represent about a sixfold increase in Sr®° over the 1958 levels. Little of the body burden of the exposed group is apparently dueto theirinitial exposure, since at presentthereis little difference between thelevels of the exposed and unexposed populationsliving on Rongelap Island. The body burdensare of small significance in termsof radiation hazard. OTHER STUDIES Studies of genetically inhertted characteristics. Blood grouping studies in the Marshallese showeda rela- tively high B gene frequency, a high N genefre- quency, an extremely high R' gene frequency, and total absence of Kell and Diego factors.'° These characteristics differ from those of Polynesians and suggest relationship with Southeast Asians and Indonesians. Haptoglobin studies showed the frequency of the Hp’ geneto be higher than in European populations thus far tested and consistent with populations living near the equator. Thedistribution of haptoglobin types showed the population to be relatively homogeneous. Transferrins in all sera were type CC, the common European type. B-Amuino-iso-butyric acid urinary levels showed the Marshallese to be the highest excreters ofthis acid of any population thus far reported. Levels in the exposed group were about the same asin the unexposed group, and no correlation was found with body burden level of radionuclides; this indicates that there is probably no correlation with radiation exposure. Hemoglobin types were considered normal(all had type AA,). Sickling tests showed no sickling tendency in any of the people. Glucose-6- phosphate dehydrogenase of the red cells appeared to be normal in the Marshallese. Studies of Gm phenotypes showed the Marshallese to have 100% Gm‘**) and nearly 100% Gm‘). There was a complete absence of Gm* and a high frequency of Gm-like (Gm*). Considerable caution must be exercised in evaluating the results of these studies on genetically inherited characteristics because of the small numberof samples tested. The data do seem to indicate relative homogeneity of the population and closest kinship with people of Southeast Asia. These data also maybe useful as a base line should genetic changes appearin later generations, possibly related to radiation exposure. Results of other laboratory studies included the following: Serum protein levels were generally on the high side of normal; electrophoretic patterns