5 The onecase of cancer that developed in the exposed group occurred at 5 years after exposure, too soon, it is believed, to bear any particularrela- tion to radiation exposure. Leukemza surveysincluding physical findings, studies of white cell counts and types, alkaline phosphatase staining, and basophil counts of 4060 white cells showed no evidence of leukemia or leukemic tendency. One child in the irradiated group hashadslightly 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 degenerative 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 apparentradiation-induced genetic changes have been detected on routine physical examination in the first-generation children of exposed parents, with the possible exception of suggestive evidence of increased miscarriages andstillbirths in the exposed -womenandtheslight 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 weeksafter 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 repigmentationfollowed. Somelesions were deeper, showed wet desquamation, and were morepainful. A few burns becamesecondarily 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 of scarring and atrophyof the skin. By 6 years the only residual effects of beta radiation of the skin were seen in 10 cases which showed varying degrees of pigment aberrations, scarring, 50007188 andatrophyatthesite of the former burns. During the past several years an increased numberofpigmented maculae and moles have been noted in previously irradiated areas of the skin, but these have appeared to be quite benign. Numeroushistopathological studies have been made,'*’ and the changes found have been consistent 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 wasshort 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 monthsafter exposure was the developmentof bluish-brown pigmentation of the semilunar areas of the fingernails and toenails in about 90% of the people. By 6 monthsthis pigmentation had disappeared, having grown outwith the nail. The cause of this phenomenonhasnot been explained. INTERNAL IRRADIATION Radiochemical analyses of numerous urine sam- ples of the exposed population showed internal absorption of radioactive materials, probably brought about largely through eating and drinking contaminated food and water andto a lesser extent through inhalation. During the first few days whenthe bodylevels were at their highest, the maximum permissible concentrations were approachedorslightly exceeded only in the case of strontium-89 and theisotopes of iodine. The concentrations were believed to be too low to result in anyseriouseffects. Body levels 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 whodied showed3.7 strontium-90 units/g calcium. Beginning in 1957, gamma spectroscopy by use of a low-level counting chamber was added to the techniquesof 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 burdens andincreased urinary excretion of certain radionuclides. During the years