Table 9. Group Risks of thyroid nodularity from radiation in children.* (years follow-up) Rongelap (27) Ailingnae (27) Utirik (27) All of above Rochester (25) Ann Arbor (17) Beach & Type Risk Dose rad (rads) Benign 18, y 710-1150 26.7 " 312 (av) 24.4 " " 280-450 60-95 x-ray (162) 119 (av) x-ray (162) 20 (av) Dolphin (20) UNSCEAR (17) ABCC (20) ABCC (20) Modan et al. x-ray (182) x-ray (97) Yon (172) Y,n (172) x-ray (163) 20-1000 <20 6-6.5 Maxon (21.5) x-ray (164) 270 (av) Albert et al. *Risk is calculated from the equation No. 29.4 16.7 Carcinoma 1.6 0 3.8 1.9 3.0 24.0 2.2 12.3 1.7 0.5-1.5 1.3 (all ages) 0.2 (all ages) 4.2 1.5 of cases x 1076 (See Table 4, dose x years at risk’ Appendix IV.) Unoperated cases in the Marshallese groups were not included in the estimates. The incidence in the matched comparison Marshallese population has been subtracted from that in the exposed groups in determining the risk. If the actual number of years at risk were used, i.e., subtraction of latent period, the risk values would be higher in the Marshallese. studies under way indicate that they in individual thyroid doses probably water consumption at the time of the doses to the children. Undoubtedly, may be too low.* Considerable variation resulted from differences in food and fallout. The greatest uncertainty was in the two boys exposed at one year of age who developed thyroid atrophy and myxedema received doses well above those calculated, as explained in Appendix II. From the Marshallese experience it appears that there is a greater propensity to develop thyroid nodularities after radioiodine exposure in the children than in the adults. This is related not only to the smaller size of their glands (resulting in larger doses) but possibly also to the rapid growth of the gland (from 1-2 grams at birth to about 18 at maturity) and increased *Even if the Marshallese thyroid doses were twice as high, the risk estimates would still be higher than would be accounted for on the basis of 131; exposure alone. ~ 78 -