Table 1. Estimated Radiation Doses in Exposed Populations il No. Affected* Estimated Whole- Body Gamma Dose (rem) Estimated Thyroid Dose (rem) by Age at Exposure <10 yr 10-18 yr >18 yr Rongelap 67 175 810-—1,800 334-810 335 Ailingnae 19 69 275-450 190 135 164 14 60-95 30-60 Utirik 30 *Includes in utero exposures (three on Rongelap, one on Ailingnae, and six on Utirik). Table 2. Summary of Thyroid Nodularity in the Marshallese, 1981 DUp Age at Exposure No.* Rongelap <10 Ailingnae <10 7 >10 12 Utirik Unexposed >10 <10 >10 <16 >10 22 45 64 100 229 371 Estimated Total Nodules 810—1,800 17 (77.3) Dose 335-810 No. (%) Carcinamat No. (%] 1 (4.5) 6 (13.3) 3 (6.7) 275—450 2 (28.6) 0 135-190 4 (33.3) 0 60-95 30-60 5 (4.7) 12 (12.0) 6 (2.6) 29 (7.8) 1 (1.6) 2 (2.0) 2 (0.9) 3 (0.8) “Includes in utero exposures (three on Rongelap, one on Ailingnae, and six on Utirik). ~ Carcinoma estimates may be low becauseall unoperated nodules were considered benign for these calculations. effects of the internal absorption of radioiodines or other nuclides were noted. Indeed, nearly a decade passed before the effects of thyroid exposure could be documented. Late Effects Until about nine years after exposure—thetime thyroid ab2ormalities were detected—the health status of the exposed people did not appearto be significantly different from thatof unexposed people, with a few possible exceptions.’ Examinations of the newborn did not reveal any detectable abnormalities in the children of exposed parents which might have been related to radiation exposure. In 1972, a Rongelap man who had been exposedat 1 year of age died of acute myelogenous leukemia.’ Relation to radiation exposure seemed probable. Thyroid Abnormalities The most widespread late effect in the Marshallese has been the development of thyroid abnormalities attributed to thyroid injury from exposure to radioiodines and gammaradiation at the time of the fallout. The effects of thyroid injury on growth and development of Rongelap children are presented below. The development of thyroid nodularities, benign and malignant, and of hypofunction are only briefly ammiarized here. Details can be found elsewhere.’*” At nine years postexposure, when it was becoming apparent that growth retardation was occurring in some of the ex- posed Rongelap children, nodules began appearing in the thyroid glands of people who had been exposed in Rongelap, particularly the children. Varying degrees of thyroid hypo- function developed in some of the children, particularly in two boys, exposed at 1 year of age, who exhibited the most stunting of growth. They showedclinical evidence of myxedema with atrophy of the thyroid gland, puffy faces, dry skin, sluggish reflexes, and bony dysgenesis of the head of the humerus and femur. Thyroid nodules developed somewhat later in the groups exposed to lower doses of radiation on Ailingnae and Utirik. The greatest incidence of thyroid nodularity has been noted in the high-dose Rongelap group, particularly in the children exposed at less than 10 years of age. Lower incidence was noted in the Ailingnae group, andthe least incidence in the lower-dose Utirik group. Noteworthy has been the recent development of thyroid nodules in two of three children exposed in utero on Rongelap (Table 2). Almost all the patients, including those who were not exposed, have had thyroid surgery in US hospitals. A wide spectrum of lesions has been found. Amongthe exposed patients, the ratio of benign lesions to carcinoma appears to be greater in children than in adults. The data are too few for definite conclusions, but they lead one to speculate that the higher thyroid doses in the children (due to the smaller sizes of their thyroid glands) could have produced an “overkill” effect. As noted, a number of children who developed thyroid nodules showed evidence of hypofunction of the thyroid prior to surgery, primarily on the basis of elevation of serum thyroid stimulating hormone (TSH). More recently, six exposed adults without clinical evidence of thyroid lesions also have shown biochemical evidence of hypofunction.’° Preventive treatment with thyroid hormone wasinstituted in the exposed Rongelap people in 1965 and in the Ailingnae people in 1969. THE CANCER BULLETIN, VOL 34, NO 3, 1962 91