35 their accidental exposureto fallout. During the 1959 survey 76 exposed persons, includingtheir Fable 36 Residual GammaActivity, in counts/min/kg, in Marshallese After Subtraction of K*°, Zn**, and Cs'*’ Age, yr Rongelap exposed Rongelap unexposed Ailingnae Utirik t-15 >15 36.1 37.9 21.4 17.2 8.8 35.0 43.0 11.7 with age or sex. No significant difference was found between the Rongelap exposed and unexposed groups, which implies that no residual Zn*° activity remains in the Rongelap people from their original exposure. The 1959 mean body burden of Zn** was 0.44 uC as compared to 0.36 »C in 1958. Thus Z2n** body burdens do not seem to have reached a steady-state equilibrium with the environment, as is also the case with Cs'**. Since the source of Zn*° is fish, which continueto be a dietary staple, the - Zn" valuecan be expectedto increase still further. The mean Utirik Zn®* level in 1959 was about one-third the Rongelap meanvalue. Although Cs'* and Zn"’ comprise the major portion of gamma-emitting radionuclides present in the Marshallese (aside from the naturallyoccurring K'"), residual gamma activity 1s still pres- ent after subtraction of K*°, Zn®*, and Cs'"* con- tributions from the total spectrum in each subject (see Table 36). Analysis of the residual spectra did not indicate any readily identifiable photopeaks in the short counting time employed (5 or 10 min). This short counting time, along with the difficulties discussed earlier in exact calibration of absolute activities, makes the identification of minor photopeaks very difficult. Most of the difficulties can be circumvented in future field trips by the use of longer counting times, the use of an 8-in. crystal, duplication of the geometry byuse of the same standard chair, and a moreprecise calibration of the phantom. Summary and Conclusions Continuing annual medical surveys of the people of Rongelap Island were carried out in March 1959 and March 1960, 5 and 6 years after children, and 166 unexposed Rongelappeople, who served as a comparison population, were ex- amined. In addition, groups of children at Uurik, Majuro, and Kwajalein Atolls were examined as controls for the growth and developmentstudies on the exposed Rongelap children. The 1960 survey was brief, only the exposed people being examined. As a result of their exposure in 1954, many of the Rongelap people had experienced early symp- toms related to the gastrointestinal tract and skin. Later they developed a significant depression of their peripheral blood elements commensurate with the calculated dose of gammaradiation (175 r to 64 people and 69:r to 18 people), and beta burnsof the skin along with spotty epilation. In addition, radiochemical analyses of urine samples showed that they had acquired a low-level body burden of radionuclides. Certain other findings were possibly related to their radiation exposure, such as loss in weight of several pounds in most of the people during the first severa! monthsafter exposure and suggestive evidence ofslight lag in growth and developmentof the children based on studies of height, weight, and bone development (but inconclusive pending verification of exact ages of someof the children). In spite of the depression of hemopoiesis, no signs of radiation illness developed in the people related to such depression, and no deaths occurred that could be related to their radiation exposure. No specific therapy was given. Recovery of the peripheral blood elements, particularly lympho- cytes and platelets, was very slow over the ensuing years. The beta burns, which appeared about2 weeks after exposure, were, for the most part, superficial in nature and healed in several weeks, with only a few lesions showing later persisting changes. Specific therapy was not necessary in most cases. The hair regrew normally, beginning at 3 monthsafter exposure. The internally absorbed radionuclides caused no known acuteeffects and were excreted remarkably fast with barely detectable activity being found a year or twolater. On return of the people to Rongelap Island the very low levels of radioactive contamination re- maining there resulted in a rise in their body burdens of cesium-137, zinc-65, and strontium-90. The 5- and 6-year post-exposure surveys were aimed primarily at evaluating the general medical