qo we ? Mn ag et . NATIONAL INSTITUTES OF HEALTH CLINICAL’STAFF ae, Before we go into the development of thyroid abnormalities in the Rongelap people, I would like to say a few words about the calculations of the radioiodine dose to the thyroid gland that they sus- tained during the first 2 days on theisland. There was no doubt considerable absorption of radioactive iodines from both inhalation as the radioactive cloud passed over them andalso from contaminated food and drinking water. Their drinking water was caught in cisterns drained from the roof, and contamination of the water was no doubt increased by a slight rainfall on the night of the fallout. There were few direct data available on which to make an evaluation of the dosimetry, so we had to rely on indirect methods—that is, on radio- chemical urinalyses. The first of these were obtained at 15 days after exposure. It was estimated that 0.1% of the isotope would be present at 15 days, back, it was calculated gland contained roughly Rall pointed out that and extrapolating that the thyroid 11.2 ue of 87. Dr. there are several iodine isotopes present in fallout. In addi- tion to 1I, the isotopes 187I, ‘831, and 151 contributed substantially to the dose. In making the calculations, energy dependence per disintegration and the time of absorption of the different isotopes were considered. It was estimated that the adult thyroid gland received approximately 160 rads from radioiodines and of course an additional 175 rads from the gamma radiation. In approximating the dose to 3- to 4-year-old children, the above factors were considered, and, in addition, we considered the difference in pulmonary function and smaller size of the thyroid gland in the child. We know that water rationing was in effect at the time of the fallout, so it is assumed that the children drank as much contaminated water as the adults did, thus absorbing the same amount of radioiodine. It is estimated that the child’s thyroid received roughly between 700 to 1,400 rads from the radidiodines in addition to 175 Sudo aoge ¥ , ww Annals of Internal Medicine rads of gamma radiation. That most of these people had beta burns in the neck region over the thyroid was not believed to contribute ‘significantly to the dose to the thyroid gland because of the low energy of the beta radiation in the fallout material. - Over the years we have carried out care- ful thyroid examinations during the annual surveys. Until 3 years ago the people were considered to have normal thyroid function with no obvious evidence of any thyroid abnormality. Numerous serum protein-bound iodine (PBI) determinations were done, and all appeared in the normal range for these people. The PBI levels in the Marshallese are considerably higher than American levels, which was found to be because there is a large amount of iodoprotein present (12), as we shall discuss later. This may have misled us during these early years. The diet of these people apparently had sufficient iodine but with no overabundance apparent. Urinary excretion studies showed that they averaged about 105 pg in 24 hr in 28 people, which ts in the normal range. Cholesterol studies have not shown anysignificant differences in the exposed and the unexposed people. Thus, there was no reason to suspect that there was any thyroid trouble. Three years ago we detected the first thyroid nodule in a 12-year-old girl. Since that time the prevalence has been increasing, and we now have 18 cases of thyroid ab- normalities, 16 with nodules and 2 with hypothyroidism, the latter showing no nadules. All of these except 1 case occurred in the more heavily exposed Rongelap group that received 175 rads of whole-body radia- tion. Table 3 lists the thyroid abnormalities with age at exposure, sex, and time of detection. It is noteworthy that the 2 cases of hypothyroidism occurred in the 2 dwarfed boys. Table 4 showsthe distribution of thyroid pathology in the different populations examined. The interesting fact emerges that the highest incidence, 78.9%, of these ab- AeA I ny gee CP Sp 1224 Sy :