PRIVACY ACT MATERIAL REMOVED food and water(see Appendix 9C). Other internally Table 3 absorbed isotopes (see Table 3) were not thought Estimated Body Burden (uCi) of Rongelap People? Activity atday | 89Sr 40Ba Rare earth group 131] (in thyroid gland) 103Ru Ca Fissile material 16 - 2.2 0.34- 2.7 0 - 1.2 6.4 -11.2 0 - 0.013 0 - 0.019 0 9 - 0.016 (ue) ‘Activity at day82 0.19 0.021 0.03 0.0 0.0 0.0 cal analyses of urine samples, beginning 15 days post exposure,for 89Sr, 149Ba, 131], the rare earth group, and fissile material. As expected, the Rongelap people had the highest body burdens. By 6 months, beta activity in the urine samples was barely detectable. Table 3 shows the main isotopes found at day 1 (extrapolated values) and at day 82. The agreement between thefindings at the two laboratories is close considering the tech- niques available at that time. Levels in the Ailingnae group were about one-half and in the Americans about one-quarterthelevels in the Rongelap group. Only isotopes of iodine, strontium, barium, and a few rare earth elements were absorbed to anysignificant degree. In the Rongelap group, at day 1, §9Sr and 131] were near the maximum per- missible levels, and the estimated total amountof radioactive material in the gastrointestinal tract was about 3 mCi; whetherthis had anyrelation to the early gastrointestinal symptoms is not known.” Radiological monitoring of personne! and environment at Rongelap and otheratolls in subsequent years is discussed in Section VI. 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-bodyradiation dose. During the early period after the fallout, radioiodine was recognized as possibly its most hazardous constituent, but the estimated dose to the gland of 100 to 150 rads was not considered sufficient to cause later development of thyroid ab- normalities. No acute effects were noted in anyof the people that could be related to the internal absorption of radioiodines or other radioisotopes. Contamination ofthe skin resulting in extensive beta burns in the neck region in 70% of the people (see Figure 2) probably did not contribute to the thyroid dose because of the low energyof the beta radiation. Possibly slight absorption of radioiodines throughthe skin occurred. When the people returned to Rongelap to live in 1957, no radioactive isotopes of iodine remained (except possibly very slight amountsof 191), and the principal remaining isotopes (!37Cs, 99Sr), which were absorbedto low levels in the people, probably did not contribute to any significant degree to the thyroid dose.® Whenthyroid lesions began developing in the Rongelapchildren in 1963, the dose to the thvroid of the Rongelap people was reevaluated bv James.?6 His estimates of the gammadose agreed approximately with the previous estimate of 175 5. Thyroid Dosimetry The fallout produced several possible sources of radiation exposure to the thyroid gland. The gamma radiation resulted in thyroid doses of 175 rads in the Rongelap people, 69 rads in the Ailingnae people, and 14 radsin the Utirik group. Iodine isotopes are producedin relatively high yields by the fission process. Some are too short-lived to be of consequence, but 131], 132], 133], and 135] are sufficiently long-lived to cause a considerable dose to the thyroid following internal absorption and concentration in that gland, and these were ab- sorbed both via inhalation and via ingestion in Figure 2. Beta burns (March 29, 1954).