: 487 Since Dr. Upton has discussed radiation carcinogenesis, I will confine my remarks to a summary of someof our relatively new data in regard to the developmentof thyroid neoplasia in Marshall Islanders exposed to radioactive fallout in 1954 and then review certain other late nonneoplastic changes in irradiated humanbeings which mayberelated to aging andlife shortening. aor: NgRET ~ RUN nA A NTEemg Rare ConaRD Thyroid Neoplasia from Radioiodine Absorption in Marshallese Exposed to Fallout During the 2 days before evacuation of the Marshallese people from their contaminatedisland, they received a sublethal exposureof y-irradiation (175 rads), marked contamination of the skin which later resulted in B-burns, and they absorbed significant amounts of radioisotopes from inhalation and ingestion of contaminated food and water. The acute effects of their expo- ficant quantity. It was calculated from radiochemical urine analyses that thyroids of adults received about 160 rads from radioiodines and in addition 175 rads from y-irradiation. Since the children had much smaller thyroids,they re- ceived considerably higher doses. It was estimated that a 3—4-year-old child received thyroid doses in the range of 700-1,400 rads from radioiodines and 175 rads from y-irradiation. The total dose to the thyroid glands compared with other organs of the body was greater by a factor of 2 in adults and about 7 in the children. Thyroid nodules first appeared in a 12-year-old girl 9 years after exposure (1963), followed by increasing numbersof thyroid nodulesin the following years in other exposed people. At present, 19 exposed Rongelap people among 66 now living (of 82 exposed) have developed nodularity and in addi- tion, 2 young boys who showed marked growth retardation developed severe hypothyroidism with atrophy of the thyroid gland [10]. Partial to complete thyroidectomy has been performed on 18 cases. Benign adenomatous nodules were noted in all but in addition, 3 cases had malignantlesions, 1 ina a ™ 3 ‘a! IU12b Fe a A ed To oe ee 1 Among the Rongelap people 64 were on Rongelap Island and received the heaviest exposure of 175 rads y-radiation, 18 others were on nearby islands and received only about 69 rads. A third group of Marshallese were on Utirik Island farther east and received only an estimated dose of 14 rads. NAaeMT, Set I alNOELO HO aed ee ee woe ee et sure have been well documented [9, 14]. Though noacuteeffects ofthe internally-absorbed fallout were observed, radioisotopes of iodine were absorbed in sufficient quantity to result in late effects on the thyroid. In addition to ™4J, several shorter-lived isotopes of iodine (19?15% 185]) were absorbed in signi- 29