275 rad 69 rad nodules in spite of a higher dose to the children’s glands. During the past ten vears, a disturbing findiag has been the further development of thyroid hypofunction, even in some Rongelaup people without other detectable abnormalities. Table 3 showsthe present status of thyroid hypofunction. The positive category represents individuals who have exhibited two TSH (thyroid-stimulating hormone) levels of 6 14 rad ire was not s began to .ed dose of J rad in the loses were qe children The largest wUrml or greater. The suggestive category represents individuals who have two TSH levels of 4 to 6. The association of radiation exposure with the developmentof thyroid abnormalities in the Rongelap population seems apparent though ‘the Utink findings are less clear-cut. The development of thyroid tumors following radiation exposure is well documented in the Japanese exposed to the atomic bomb and in patients, particularly children. following radiation therapy. On a risk per rad basis, the induction of thyroid nodules and cancer in the Marshallese appears to be about equal to that following X-ray exposure. Since '!} is believed to be only about one-tenth as effective as culariy‘°], of growth later corre‘gsed func- X irradiation in producing thyroid abnormalities, it seems likely that ir the Marshallese the exposure to the short-lived isotopes of iodine 7], 83], and 'I, which have more energetic betas and deliver a faster dose rate than ''], might account for the high incidence. The findings in the Marshallese emphasize the importance of thyroid was about larly in the 110 appear 967, in the » have had exposure to radioiodines that may result from warfare or accidents in which radioiodines are released. Exposure to penetrating gammas or v increased neutrons is a more serious hazard not only because of their acute effects. but also because of the fatal nature of malignancies such as leukemia which may develop. Deaths due to thyroid abnormalities including cancer tirik group unexposed Table 3. Cancer? 4.7% (4/86) 1.9% (3/158) ‘aSES are Sf eet rarer Group Positive Rongelap + Ailingnae (135-1150 rads) 15% (13/86) Utirik 0.8% (1/158) (6/158) Unex posed 0.6% (1/155) (30-95 rads) eet Ps ra? Se tp be 0.9% (4/437) Thyroid Hypofunction in Marshallese Populations Suggestive Total? 9.3% (8/86) 24.4% (21/86) 3.8% 4.4% 1.5% (1/67) 3.0% (2/67) (7/158) “Some of these subjects appear also in the nodule table, ie., they have both hypofunction and nodularity. ena.eaea a a AY 1 ane “ThalRR SI i we Estimated gamma dose people. In the Rongelap-Ailingnae group, 65% of those exposed as children had nodules compared with 27% of those exposed as adults. Paradoxically. in the Utink population a greater percentage of adults had