Table 3. Expected percent of persons with thyroid nodules in comparison populations based on estimated doses. % Nodules (cases/no.) Est. dose Group (rem) Children? Rongelap 2.25 Utirik 8.0 Adult s? Rongelap Utirik 4.5 16.0 Rong. risk (total)! 0.1% (0.2/553) 0.6% (2.7/435) X-ray risk (benign) 2 0.07% (0.4/557) 0.2% (1.1/435) % Carcinoma (cases/no.) Rong. risk (total)! <0.01% (0.04/557) 0.03 (0.15/435) 0.2% (0.01/115) 0.06 (0.07/115) (0.2/38) (0.08/38) 0.5% X-ray risk (benign) 2 0.02 (0.1/557) 0.01 (€0.4/435) 0.2% luUsing risk data for exposed Rongelap and Ailingnae people (25 years), cases per million per rad per year: children (exposed at age <10), total 31, cancer 1.7; adults (exposed at age 710), total 14.6, cancer 5.6. 2Using Maxon's (163) estimates of absolute risk (cases per million per rad per year), 12.3 for benign nodules and 4.2 for cancer, based on combined data of Coleman et al. (233), Hemplemann (162), Modan (166), and Albert (200) on children treated with x-irradiation. Recently Maxon, on the basis of later data, has revised his risk estimate for thyroid cancer downward to 1.5 cases/10 persons/rad/yr (164). Use of this value would lower the expected risk in the populations listed in this table. Also, preliminary results of reassessment of thyroid doses indicate a possible increase in estimated dose which could lower the Rongelap risk factors. 3children: age <10 in 1954; adults: age >10 in 1954. Children were considered to have lived 11 yr on Rongelap or 13 yr on Utirik and to have received half the total dose. Adults were considered to have lived 22 yr on Rongelap and 25 yr on Utirik, and their total estimated doses are listed. C. Comparison of Thyroid Findings in Marshallese Comparison Fopulations With Those in Other Unexposed Populations A number of statistical reports have been published on thyroid neoplasia in populations not exposed to radiation (see Fig. 1). These statistics show considerable variation, and some populations appear to be more prone to devel- opment of thyroid cancer. - 107 -