: a ee . oe 2 in ‘ = , -& tb ein Kaen, te 6 days when the body levels were at their highest, the maximum permissible concentrations were ap- proachedorslightly exceeded only in the case of strontium-89 and the isotopes of iodine. At that time the concentrations were believed to be too lowto result in any seriouseffects. Body levels fell rapidly, so that by 2 and 3 years post exposure they were far below the accepted maximum permissible level; even by 6 months activity in the urine was barely detectable. In 1958 analyses of bone samples on one of the men who died showed a body burden of 3.7 nCi “Sr. Beginning in 1957, gamma spectroscopy by use of a low-level counting chamber was addedto the techniques of radiochemical analysis. The return of the Rongelapese to their home island (which after careful survey was considered safe for habitation, despite a persisting low level of radioactive contamination) wasreflected in a rise in their body burdensandincreased urinary excretion of certain radionuclides. During the 4 years after the original contaminating event, additional weaponstests held in the area contributedslightly to the fission products in the environment. Since the diet includes a variety of imported foods, the people may have been delayed in reaching equilibrium with the environmentalfission products. Body burdens of gamma-emitting fission products (such as '*’Cs and ®°Zn) were measured in a whole-body counter and checked by radiochemical analysis of urine specimens. Thelevels of internal contamination per unit weight appeared to be about the samefor juveniles as for adults, male and female. Widevariations in levels of contamination were found, apparently dueto differences in diet, metabolism, and age. Body burdensof °°Sr were estimated from urinary excretion as determined by radiochemical analyses. Both the external dose measurements on Rongelap Island andthelevels of radioactive iso- topes 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 wCi, 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 Ci. The mean bodyburden of *Zn estimated from wholebody counting data was, in 1958, after the return to Rongelap, 0.36 Ci, 8 times as high as in 1957, and 0.44 pCi in 1959. In 1961 the mean '3"Cs 5908298 body burden was 0.67 Ci, whichis slightly higher than the meanvalueof a similar group obtained in 1959; it was 300 times that of the medical team, who were measuredat the same time for comparison. It appeared at this time that the people were approaching equilibrium with their environment. The *Zn level dropped to 0.071 wCi in 1959. With a larger detector and a longer counting time than previously employed, it was possible to identify and quantify °°Co for the first time in these people; the meanlevel of *°Co was about 11% of the "°Zn level (7.6 nCi). A small amountof residual 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 pCi/l or 14% higher than measured in the 1959 medical survey. In 1962 the mean urinary *°Sr level was 114 pCi/g Ca, giving an estimated body burden of 12.0 nCi. Analysis of bones from the deceased Rongelap woman (1962) gave an estimated body burden of 11.4 nCi. These levels represent about a 6-fold increase in °°Sr over the 1958 levels. The levels of “"Sr in 1962 and 1963 hovered around the 12.0-nCi level in adults and about 22 nCi in children, about 5 and 10% respectively of the maximum permissibie level (for members of the population at large). It thus appears that body burdensof *’Sr have reached equilibrium with the environmental °’Sr. Little or none of the present body burden of the exposed group can be considered residual from their initial exposure, since little difference has been noted between the body burdens in exposed and unexposed populations living on Rongelap Island. The possible relation of interna] absorption of radioiodinesinitially in the fallout to the recent developmentof thyroid nodules will be referred to later. No other effects of such exposure have been detected. / OTHER STUDIES Studies of Genetically Inherited Characteristics: Blood grouping studies in the Marshallese showeda rela- tively high B gene frequency, a high N gene frequency, an extremely high R' gene frequency, and total absence of Kell and Diegofactors.'' These characteristics differ from those of Polynesians and suggest relationship with Southeast Asians and Indonesians. Haptoglobin studies showed the frequency of the Hp' gene to be higher than in Euro-