125-14-6535 oo apparently not been significantly severe to result in clinically evident hypothyroidiss but by currently acceptable criteria, in these individuals. there is evidence of impaired thyroid reserve If left untreated, it would be anticipated that thyroid functior would continue to decrease in this group to the point of clinical hypothyroidism. The data also indicate that the frequency of an elevated serum TSH, the earliest biochen— ical evidence of impaired thyroid function, is also significantly more cormon in the Rongelap population than in the control-unexposed groupThere are several other exposed Rongelap individuals in whom results of basal TSH, and at least one TRH test, have suggested the possibility they may also have evidence of impaired thyroid function” These data indicate that in addition to thyroid nodularity, which is a well-.. recognized manifestation of exposure to radioactive iodine or external radiation, biochemical evidence of thyroid dysfunction can appear 25 years or longer after an initial thyroid dose of as low as 350 rads.(Conard, R-A. et al. BNL Report 50424, Brookhaven ‘National Laboratory, Upton, N.¥., December, 1975). 3. Rationale: 7 oe The exposed Marshallese constitute a unique population accidentally exposed to ‘acute and long-term effects of fallout from a ground/sea leval 15 MI thermonuclear weapon. The radiation characteristics are different from those under observation in Japan and in other nuclear reactor or weapons-test accidents. This prospective study, now in its twenty-fifth year, has provided unique epidemiological data on 244 exposed individuals, particularly in relation to thyroid pathology. In recent years, we have seen an unusually high prevalence of biologic hypothyroidism, previously- unsuspected. Although a significant number of people suffered beta burns, no skin cancer has been detected, but continual monitoring is necessary. One man, exposed at one year of age, died of acute myelogenous leukemia at age 19. Since pre-accident- vital statistics are almost totally unreliable, one of the important goals of the study is to establish the incidence and/or prevalence of those pathologic conditions most frequently associated with radiation in a control/comparison group of Marshallese. Due to cultural, geographic and political problems, the accunuv—lation of this type of data is proceeding very slowly. The lack of reliable vital Statistics, coupled with the small size of the exposed group, makes the statistical . analysis of the data very difficult. In addition, one should recognize that with the Westernization of the Marshallese culture following the accident, consumption and/or exposure to a number of potent carcinogenic agents has occurred. These other independent variables, i-e., smoking, chemical carcinogens, etc., should not be underestimated in the analysis of selected cancers, for example, lung, GI, CU. In the case of thyroid neoplasia, (Larsen, P.R., et al. 1978, p. 101). these carcinogens would have Little effect. Late Biologic Effects of Tonizing Radiation I. . IAEA, Vienna, , *