EFFECTS OF FALLOUT RADIATION 293 changes that occur with aging would be difficult to detect over this period of time. During the 4-year survey, data have been collected in an attempt to obtain semiquantitative estimates of biological age by scoring the degree of certain criteria such as greying of the hair, skin looseness, skin retractility, arcus senilis, retinal arteriosclerosis, accommodation, and blood pressure. These data have not been completely analyzed yet. 3. Degenerative diseases have not been found to be increased in the exposed people. No malignancies have been detected. In the irradiated Japanese an increased incidence of leukemia has been noted (17, 18). There have been no cases of leukemia or leukemic tendency noted in the Marshallese. (No cases have shown decrease in _ alkaline phosphatase of neutrophils, nor have increased levels of basophils been noted.) Since the incidence of malignancy or leukemia would be expected to be relatively low with the dose of irradiation received and since such 2 small population is involved, the probabilities are good that such effects will not be observed in the Marshallese. 4. Ophthalmological changes related to late effects of radiation (8, 20) have not been seen. Slit-lamp observations over the past 4+ years have revealed no polychromatic plaques or cataracts. No differences were found in visual acuity in the exposed and unexposed children. 3. Genetic effects. No specific studies for genetic effects have been conducted; however, no abnormalities have been noted in the 18 babies born of irradiated parents. In viewof the generally negative findings in the studies of the first-generation offspring of the irradiated Japanese (19), it is unlikely that genetic studies in this group will be fruitful. 6. Beta-irradiation. No late effects of @-irradiation of the skin such as chronic radiation dermatitis or premalignant or malignant changes have been found in the Marshallese. 7. Body burdens of radioactive isotopes. The present body burdensof radioactive isotopes absorbed from both the initial contaminating event and the present habitation on Rongelap are far below the accepted tolerance levels, and the hazard from this exposure is unlikely to result in any late effects. Even though, as pointed out, the radioactive contamination of Rongelap island is considered perfectly safe for human habitation, the levels of activity are higher than found in other inhabited locations in the world. The habitation of these people onthe island, therefore, affords a most valuable ecological radiation study on human beings. Since only small amounts of isotopes are necessary for tracer studies, the various radioisotopes present can be traced from thesoil, through the food chain, and into the human being, where the tissue and organ distribution, biological half- lives, and excretion rates can be studied. Such investigations will be done by the use of whole-body y-ray spectroscopy of the people and of sample materials, and by radiochemical analysis of soil, food, and human excreta.