63 hypothyroidism in the two most growth-retarded boys with subsequent growth response to thyroid hormone treatment. Thyroid function tests in cases with thyroid abnormalities also indicated reduced thyroid function in someother children. Preliminary indications are that thyroid hormone treatment instituted in the exposed population in September1965 is having a beneficial effect in re- ducing thyroid nodules and stimulating growth of children. The importance of these thyroid developments in the Marshallese is discussed. OTHER STUDIES Hematological studies show that the leukocyte and platelet levels of the peripheral blood of the ex- Laat, | posed Rongelap people seem to have recovered to levels equal to those of the unexposed population. Nal (TI) crystal in a portable shadow-shield type of counter. The Rongelap residents exposed in 1954 and the unexposedresidents were indistin- guishable by this method, both groups showing elevated '*°Cs body burdensof 10 to 20 nCi;kg body weight, orslightly less than 1 Ci total body burden and about ooo this much for °°Co body burdens. These levels are about the same as or slightly lower than those reported previouslyfor the 1961 survey. Urine specimenswere also ana- lyzed radiochemicallyfor °°Sr and '°’Cs, The °°Sr levels remain nearly the same as those found in 1961. In a comparison of the ***Cs excretion rate with the body burdens, a mean fractional excretion rate of 0.00553/day was found. The blood levels of the Utirik population showed Acknowledgments blood cultures showed a low incidence of 2-hit was necessary to carry out these surveys successfully. The authors are deeply grateful for valuable no obvious abnormalities and were similar to those previously noted. . Chromosome studies of white cells of 51 peripheral aberrations in the exposed people which was quite significant in view of the absence of any such aber- The cooperation of many agencies and persons assistance to many individuals too numerous to name. Weare particularly grateful to the people rations in the comparison population. Blood volume and red blood cell volume studies showed that people of Rongelap havesignificantly reduced levels as compared with Americans. Cau- of Rongelap and Utirik Atolls for their cooperation in these examinations. Manyofficials of the Atomic Energy Commis- erally show this phenomenon. ogy and Medicine, and Mr. W.A. Bonnet and Mr casiansliving in the Marshall Islands did not genAging studies have been repeated with the addi- tion of several new parameters.(vibratory sense, light extinction test, body potassium levels, and blood serum cholesterol) and with morerefined Statistical analysis. Curves of response for each aging parameterand anover-all biological age score curve are presented. Nosignificant increase in aging effects in the exposed population compared with the unexposed population could be detected. The over-all correlation of the biological age scores with chronological age was good. It was concludedthatthe tests employed may not have been sensitive enoughto detect subtle effects of aging at this exposurelevel. sion, particularly Dr. Charles L. Dunham and Dr H.D. Brunerandtheirstaff of the Division of BiolNeil Rassmussen of the Honolulu Operations Of- fice, were most helpful in coordination of arrangements and in supporting the surveys in every wav possible. Weare grateful to the officials of the Department ofthe Interior, particularly Mrs. Ruth Van Cleeve and the officials of the Trust Territory of the Pacific Islands, including High Commis- sioners Mr. W.M. Goding and Mr. W.R. Noorwood; the Acting Director of Medical Services. Dr. L.A. Howe; the District Administrator for the Marshall Islands, Mr. Dwight Heine, and his As- sistant, Mr. Danny Akimoto; the Director of the Majuro Hospital, Dr. John Iaman, and members of his staff; the Trust Territory Representative at ESTIMATION OF INTERNAL BODY BURDENS OF RADIONUCLIDES In the 1965 survey whole-body counting was done on 179 people with an 11'%-in.-diameter Kwajalein, Mr. R. McKay, and Dr. Ezra Riklon at the Ebeye Hospital; all were most helpful. The Pacific Missile Range Facility at Kwajalein wasofgreat assistance in furnishing necessaryair- lifts and materials. Mr. Frank Granich and others