fission process. Some are too short-lived to be of consequence, but 131,, 321, I, and I are sufficiently long-lived co cause a considerable dose to the thyroid following internal absorption and concentration in that gland, and these were absorbed both via inhalation and via ingestion in food and water (see App. 2 of ref. 12). Other internally absorbed isotopes (see Table 2) were not thought to be significantly absorbed by the thyroid and probably contributed little to the dose to that gland. Conversely, the radioiodines contributed only slightly to the whole-body radiacion dose. During the early period after the fallout, radioiodine was recognized as possibly the most hazardous constituent, but the estimated dose to the gland of 100 » 150 rads was not considered sufficient to cause later development of thyroia abnormalities. No acute effects were noted in any of the peonle that could be related to the internal absorption of radioiodines or other radionuclides. Contamination of the skin resulting in extensive beta burns in the neck region in 70% of the people probably did not contribute to the thyroid dose because of the low energy of the beta radiation. tion of radioiodines through the skin occurred. Possibly slight absorp— When the people returned to Rongelap and Utirik to live, no ra isotopes of iodine remained (except Fee. 803 ne slight amounts of 12 9), the principal remaining nuclides (3 Oco, 55Fe), which vere absorbed to low levels in the people, wrobabiy contributed only low doses to the thyroid. (See Section B, below.) When thyroid lesions began developing in the Rongelap children in 1963, the dose to the thyroid of the Rongelap people was reevaluated by James (19). His estimates of the gamma dose agreed approximately with the previous estimate of 175 rads. Calculation of the dosage from radioiodines unfortunately had to be based on a single, pooled urine sample from Rongelap people collected 15 days post exposure. Harris at Los Alamos had reported a low level of 131] in this sample and had calculated a one-day thyroid content of 11.2 uCi based on the assumption of 0.12 urinary excretion of the maximum thyroid burden on the 15th day (235). James (19) calculated doses for absorption from both inhalation and in~ gestion. He noted that the shorter-Lived isotopes of iodine delivered 2 to 3 times the estimated dose delivered by 131 alone. The importance of these shorter-lived isotopes in producing thyroid effects in the Marshallese is referred to in Section IX of the text. The dose to the thyroid of a Rongelap adult (including gamma) was calculated as about 335 rads (220 to 450 rads) and to that of a 3-yr-old Rongelap child as 700 to 1400 rads. (The spread is due to uncertainties in estimating dose from absorption of radioiodines by inhala- tion versus ingestion.) It.should be noted that the thyroid glands of l-yrold children are only about two-thirds the size of those of 3-yr-olds and therefore might have received 2000 rads or more. With the assumption that the ratio of whole-body gamma doses to thyroid doses was about the same for people exposed on Ailingnae and Utirik as for the Rongelap people, James' calculations were used to estimate thyroid doses in the Ailingnae and Utirik groups; the results were 135 rads for the Ailingnae adults and 31 rads for the Utirik adults. The children's thyroid doses were based on the weight of the gland at various ages (247). By using a linear relationship between the thyroid size and the dose calculated by James, the doses to individual children were taken from regression lines drawn for the three exposed populations; these are given in Table 3. In retrospect, the - 113 -