J The one case ofcancer that developed in the exposed group occurred at 5 years after exposure, too soon,it is believed, to bear any particularrelation to radiationexposure. Leukemia surveys in- cluding physical findings, studies of white cell counts and types, alkaline phosphatasestaining, and basophil counts of 4000 white ceils showed no evidence of leukemia or leukemic tendency. One child in the irradiated group has hadslightly elevated basophils but no otherpositive findings. The cardiovascular and arthritis surveys, as well as the general results of the physical examinations, have not shown any apparent increased incidence of degeneratwe diseases in the exposed people. No radiation-induced cataracts have been observed in any of the exposed people. Genetic effects have not been specifically studied because of the small numberof people involved. No apparent radiation-induced genetic changes have been detected on routine physical examination in the first-generation children of exposed parents, with the possible exception of suggestive evidenceof increased miscarriages andstillbirths in the exposed women andtheslight retardation of growth noted in the male children of exposed parents. BETA IRRADIATION OF THE SKIN It was impossible to get an accurate estimate of the radiation dose to the skin. Beta burns of the skin and epilation appeared about 2 weeks after exposure, largely on parts of the body not covered by clothing. About 90% of the people had these burns, and a smaller number developed spotty epilation of the scalp. Most of the lesions were superficial; they exhibited pigmentation and dry, scaly desquamation, and were associated with little pain. Rapid healing and repigmentation followed. Somelesions were deeper, showed wet des- quamation, and were more painful. A few burns became secondarily infected and had to be treated with antibiotics. Repigmentation of the lesions gradually took place in most instances, and the skin appeared normal within a few weeks. However, in about 15% of the people, deeperlesions, particularly noted on the dorsum ofthe feet, continued to show lack of repigmentation with varying degrees ofscarring and atrophyofthe skin. By 6 vears the only residual effects of beta radiation of the skin were seen in 10 cases which showed varying degrees of pigment aberrations, scarring, and atrophyatthesite of the former burns. During the past several years an increased numberofpig- mented maculae and moles have been noted in previously irradiated areas of the skin, but these have appeared to be quite benign. Numerous histopathological studies have been made,'** and the changes found have been con- sistent with radiation damage. At no time have changes been observed either grossly or microscopically indicative of malignant or premalignant change. Spotty epilation on the heads was short lived, regrowth of hair occurring about 3 months after exposure and complete regrowth of normal hair by 6 months. No further evidence of epilation has been seen. An interesting observation noted duringthefirst few months after exposure was the developmentof bluish-brown pigmentation of the semilunar areas of the fingernails and toenails in about 90% of the people. By 6 months this pigmentation had disappeared, having grown out with the nail. The cause of this phenomenonhas not been explained. INTERNAL IRRADIATION Radiochemical analyses of numerous urine samples of the exposed population showedinternal absorption of radioactive materials, probably brought about largely through eating and drinking contaminated food and water and to a lesser extent through inhalation. During the first few days when the body levels were at their highest, the maximum permissible concentrations were approachedorslightly exceeded only in the case of strontium-89 andthe isotopes of iodine. The concentrations were believed to be too low to result in any serious effects. Bodylevels fell rapidly. so that by 2 and 3 years post exposure, they were far below the accepted maximum permissible level: by 6 months activity in the urine was barely detectable In 1958 analyses of bone samples on oneof the men who died showed 3.7 strontium-90 units/g calcium. Beginning in 1957, gammaspectroscopy by use of a low-level counting chamber was added to the techniques of radiochemical analysis. The return of the Rongelapese to their homeisland (which after careful survey was consideredsafe for habitation, despite a persisting low level of radioactive contamination) was reflected in a rise in their body burdens‘and increased urinary excretion of certain radionuclides. During the years