TABLE I Age at Exposure Group No. Thyroid Abnormalities (and % of age group)* Rongelap < 10 29%% 20 (70%) Ailingnae > 10 57 LO (17.5%) Utirik < 10 58 > 10 100 L (1.7%) 10 (10.0%) surgery Cancers 17 1 8 3 i 1 67. 2 * Among 653 unexposed Marshallese examined there were 31 thyroid tumors (4.72). ** 4 of these were exposed in utero, one of whom had nonmalignant thyroid tumors removed. , The above table sh.ws that of the 30 people who have developed thyroid abnormalities in the Rongelap-Ailingnae group,25 (including 20 of 29 children) have had thyroid surgery in the United States with 4 of the tumors proving to be cancer. In the Utirik group,of the 7 with surgery 3 had cancers. Most of thyroid tumors in the Rongelap group must unquestionably be related to radiation exposure. The relation to radiation exposure in the Utirik group is more puzzling. The occurrence of 3 cases of cancer of the thyroid in that group is considerably greater than expected based on normal occurrence in unexposed populations,and association with radiation exposure must be considered possible. However, based on the estimated thyroid doses in the Utirik group compared with the Rongelap group, the incidence of thyroid cancer in the Utirik group is considerably greater than would be expected and,conversely, the number of benign lesions is considerably less than would be predicted. In both groups, tumors are continuing’ to appear. Appendix 1 lists people in both Island groups who have had thyroid surgery. Appendix 2 lists those who developed thyroid nodules, but in whom surgery was not indicated. In addition there are some people (not listed), in whom, based on palpation, thyroid changes are suspected, but not definite enough to list as positive. In the past few years sensitive tests of thyroid function have become available. These tests have shown the presence of decreased thyroid function below normal levels (hypothyroidism) not only in those who have had tumors removed but also in a number of exposed Rongelap people who have not shown any tumors of the gland. This finding would seem to be associated with radiation-induced injury to the gland. Appendix 3 lists these people. The exposed Rongelap people have been treated with thyroid hormone since 1965 and this treatment has been important in (1) maintaining normal metabolism in the exposed people, particularly those who have had part or all of their thyroids removed, and (2) in enhancing growth Unfortunately, the and development in children who had shown growth retardation. role of the hormone treatment in preventing the development of tumors of the thyroid is questionable since, as pointed out, a few tumors continue to appear in the exposed people. rO12121