38 posed people of Rongelap and Likiep (a nearby atoll not exposed to fallout), the incidence appears ~ to be about 5%, mostly present in older age groups (see Figure 29 and Table 25). We have seen a few cases of hyperthyroidism and myxedema at the Majuro Hospital, but no statistics are available. Two cases of thyroid cancer are reported from hospital admissions for a 10-year period (19521962) for the Marshall Islands, the population varying between 15,000 and 20,000 during that period. This has been estimated by Trust Territory medical personnel to be about half the actual number of cases (therefore 8 cases per 20,000 people per 20 years was used forstatistical com- parisons). Data on iodine intake and excretion in the Marshallese (tabulated below and presented in detail in Appendix 9) indicate that iodine-deficiency goiter would not be expected in this population. Sample 28 Urines 19 Urines 7 Diets (1965) (1974)* (1974)* Iodine, av. ug/day (range) 103 (19-279) 127 (25-266) 70 (48-152) The urinary iodine excretion is somewhat lower than the U.S. mean of 190 pg/day (18-483) in 1941.94 On the basis of the few diets analyzed, the daily iodine intake seems to be within the recommended range of 50 to 75 wg.9 These iodinelevels are somewhat lower than would be expected in an oceanic population but are much higher than seen in areas of endemic goiter.96 The Marshallese diet contains no knowgoitrogens, and diffuse goiters (typical of endemic goiter) have not been observed. The high incidence of both benign and malignant thyroid nodules in the exposed Rongelap people appears to be clearly related to radiation exposure with a large component dueto radioiodine in the fallout. Numerous studies on animals have shownthat thyroid neoplasia follows exposure both to x-irradiation and to radioiodines.97-99 Such tumors may be benign or malignant and appear to be dose-dependent to some degree. The incidence of thyroid tumors is increased tn Japanese atom bomb survivors!09-103 (Figure 43). There is a considerable amount of data showing that children who were given radiation to the head and neck region for treatment of thymic hyper*The iodine analyses were done by M.T. Kinsley and D.F. Leahy at BNL. Prevalence / 1OG0 not veryreliable. From our survevs of the unex- 30 + C3 Hiroshima Nagasaki Notincity O49 10-9 T65 dose 100 + rad Figure 43. Prevalence of diseases of the thyroid, fifth ex- amination cycle, by radiation dose and city for females age 0 to £9 at time of bomb.(From Belsky et al.104) trophy, acne, and fungus of the scalp have an increased incidence of both benign and malignant thyroid lesions in later years.!95-!12 Reports of tumorigenic effects of radioiodine in man are more limited. Sheline et al.,!15 in their follow-up study of 250 patients treated for hyperthyroidism, reported 8 having nodular goiter, of whom 6 had been irradiated at age <20 and 4 at age <10. More recently a numberof cancersof the thyroid have been reported in patients previously treated with radioiodine for hyperthyroidism.!14-116 The numberof such cases reported is, however, lower than might be expected on the basis of the widespread use of 131], perhaps becausethecells are morelikely to undergo lethal damage.!!7-122 In the more heavily exposed Rongelap group the adult thyroids received a dose (335 rads) about twice that to the whole body and those of small children (700 to 1400 rads) about 8 times that to the whole body. On thebasis of the incidence of benign nodules in the unexposed Marshall Islands populations examined, about3 to 4 cases would be expected during the 20 years in the Rongelap exposed group, whereas 24 occurred. In the Utirik group about 6 would be expected, and 6 occurred. Regarding cancer of the thyroid, on the basis of Marshall Islands statistics, about 0.033 cases would be expected in the Rongelap group over the 20year period, whereas 3 occurred. In the Uturik population about 0.06 cases would be expected, and 1 occurred; in view of the low dose of radia- tion it is unlikely that this case is radiation induced. Tables 33 and 34 showthe incidence and the risk per rad in the Marshallese compared with that in other populations for both benign and malignant thyroid neoplasms. Data on benign thyroid nodularity are scarce, but the incidence in ope Fat