TAEA-SM-224/607 103 superficial and healed within several weeks with normal regrowth of hair. Slight scarring remained in some cases but no development of skin malignancy has been noted in subsequent years. Another source of exposurein all the island groups came from internal absorption of radionuclides from inhalation and ingestion of contaminated food and water. Radiochemical urinalyses run during the first few weeks showed the following estimated body burdens(uCi) of the principal radionuclides in the Rongelap population at one day post exposure: 89Sr 1.6—2.2; '°Ba 0.34—2.7; rare earth group 0O—1.2; '3'I (in thyroid gland) 6.4—11.2; !?Ru 0—0.013; Ca 0O—0.019; andfissile material O—0.016 (yg). No acute symptoms were noted from this internal absorption of radionuclides, and by six months urinalyses indicated they were virtually completely eliminated. Nevertheless, the early exposure to radioiodines resulted in serious injury to the thyroid glands with late effects to be described below. The thyroid dose was estimated to be considerably higher in the children because of the smaller size of the thyroid glands. In the Rongelap people the thyroid dose from gamma radiation and radioiodines (principally '3*I, 1°21, '3°I and !*5I) was estimated to be about 335 rads in the adults whereas in small children the doses ranged up to 700—1400 rads. The thyroid doses in the Ailingnae and Utirik groups were extrapolated from the Rongelap estimates assuming the ratio of whole body gammaand iodine doses were the same as in the Rongelap people. Following the initial studies, annual examinations and, more recently, quarterly examinations of the exposed people, as well as an unexposed control Marshallese population, have been carried out, and results of these examinations have been published [1—4}. In the first ten years after the accident few findings were noted that could be related to radiation exposure. An increase in miscarriages andstillbirths in the exposed Rongelap women was thoughtto be possibly related to exposure. During the second decade, however,serious late effects developed related primarily to the thyroid gland. In addition a Rongelap man who had been exposed at one year of age, died of acute myelogenous leukaemia which was likely related to radiation exposure [3]. Before thyroid abnormalities became apparent, it was noted that about five children exposed at less than five years of age showed some degree of growth retardation [4]. In two boys growth retardation was marked and frank myxoedema developed. Thyroid hypofunction related to thyroid injury later became apparent with more sophisticated techniques for determining thyroxine levels. It was not detected early in the children by PBI determinations because of masking of true thyroxine levels by unusually high levels of iodoprotein, later found to be characteristic of the Marshallese people [5]. Nodules of the thyroid gland began to appear in Rongelap children and to a lesser extent in adults beginning about nine years post exposure. These nodules have continued to appear over the subsequent 15 years, and virtually all of these