Table 9. Risks of thyroid nodularity from radiation in children.* Risk Group Type (years follow-up) Rongelap (27) Ailingnae (27) Utirik (27) rad (rads) Benign 18, Y 710-1150 26.7 " " All of above Rochester (25) Ann Arbor (17) " x-ray (162) x-ray (162) Dolphin (20) UNSCEAR (17) x-ray (182) x-ray (97) Beach & ABCC (20) Dose Y,n (172) 280-450 60-95 312 (Cav) 119 (Cav) 20 (av) 1.6 29.4 0 24.4 1.9 3.0 2.2 16.7 3.8 24.0 L.7 0.5-1.5 20-1000 ABCC (20) Modan et al. Y,n (172) x-ray (163) <20 6-6.5 Maxon (21.5) x-ray (164) 270 (av) Albert et al. Carcinoma. 1.3 (all ages) 0.2 (all ages) 4.2 12.3 1.5 No. of cases x 1076 *Risk is calculated . from the equation dose x years at risk’ Appendix IV.) (See Table 4, 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 may be too low.* Considerable variation in individual thyroid doses probably resulted from differences in food and water consumption at the time of the fallout. The greatest uncertainty was in doses to the children. Undoubtedly, 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 13ly exposure alone. -~ 78 -