population basis) in the Utirik group were in accord with the estimated lower doses of radiation in these groups. 2. Skin Doses The skin exposure may have been several hundred to a few thousand rads. Symptoms of itching and burning of the skin were widespread in the Rongelap group. The lesser skin symptoms in the Ailingnae and Rongerik groups and their absence in the Utirik group were in conformity with the reduced fallout exposure of these atolls. Also, the reduced number of "beta" burns and epilation in the Ailingnae and Rongerik groups than in the Rongelap group and their absence in the Utirik group was in line with the lesser fallout exposure on these atolls. Though beta burns were numerous, particularly in the Rongelap group, the superficial nature of the lesions with rapid healing and regrowth of hair was in conformity with the low penetrability of the beta radi- ation. The lack of any evidence of chronic radiation dermatitis or development of skin cancer in later years is also indicative of this. 3. Internal Doses to Individual Organs or Tissues The widespread differences in energy spectra of the internally absorbed radionuclides made calculations of absorbed doses to the whole body and bone marrow extremely difficult. However, except for the thyroid, these absorbed doses are believed to have been small compared with the whole-body external exposure. Many uncertainties made the thyroid dose estimates difficult: first pooled samples, at 15 days post exposure, personnel showed I3lyz, and the levels were low; only the in the Rongelap and Rongerik the degree of urinary excre- tion of iodine at 15 days is uncertain; the amounts of potent short-lived iodine isotopes present at the time of the fallout, particularly on the more distant atolls are unknown; the relative importance of absorption of radionuclides via ingestion of contaminated food and water versus inhalation 1s uncertain; and the thyroid dose is different in adults and children because of the size of the thyroid gland, etc.* In spite of these difficulties it does not seem likely that the radiation doses to the thyroids would be too far removed from those calculated by James (19) since there should be a rough proportionality between the gamma dose estimates and the amount of radioiodines in the fallout, taking into account the time of arrival of the fallout; and, as pointed out above, there does not appear to be a great discrepancy between the gamma dose estimates and the clinical findings. However, there could have been considerable variation among thyroid doses in different individuals de- pending on the amount of food and water consumed at the time of the fallout. As pointed out earlier, the two Rongelap boys who developed atrophy of the thyroid with myxedema and other children probably received doses considerably higher than James' estimates for the 3-year-old children because of the smaller size of their glands. Other factors which might have contributed to the higher doses in the small children were (a) that playing in close contact with the contaminated ground increased their ingestion, etc., which is borne *See second footnote at beginning of this Appendix. - 121 -