In summary, hypothyroidism and subclinical thyroid hypofunction, benign thyroid nodule formation, thyroid surgery with its attendant risks and complications, an excessive preva- to be significantly diminished thyroid reserve in many exposed persons, and, although this diminution is not apparent from routine TSH testing, it frequently may be made clinically significant by thyroid surgery. The extent of the problem cannot be accurately assessed with the data at hand becauseof the variability in compliance with the taking of the prescribed thyroxin suppression, and because no clinical benefit would accrue to the exposed population from discontinuing thyroxin for the purpose of proving the point. Nevertheless, a 61% prevalence of postsurgical thyroid hypofunction is reason for great concern in view of the high frequency of benign thyroid nodules in the exposed population. D. Postsurgical hypoparathyroidism: In two thyroid surgery patients transient postsurgical hypocalcemia was observed. However, two other Rongelap women developed chronic hypoparathyroidism requiring replacement therapy since undergoing thyroid surgery. In one the deficiency was diagnosed postoperatively and has not resolved. In the other the diagnosis was first made.twenty years following surgery. Both surgeries were performed on Guam during the early yearsof the medical program. Postsurgical hypoparathyroidism is not an unusual complication of extensive thyroid surgery, occurring in up to 20% of patients. However, in experienced hands the frequency of postsurgical hypoparathyroidism is much lower. lence of thyroid hypofunction after thyroid surgery, and possibly pituitary tumors can be considered adverse delayed consequences of radiation injury in the exposed Marshallese. The tally comes to 85 morbid events in 253 persons. In contrast, the only evidence for a “stochastic” effect of radiation exposure has been an increase in thyroid cancers in the Rongelap population, none of whom yet have evidence of residual disease. While several nonthyroidal cancers known to be inducible in humans by external ionizing radiation have been documented in the exposed population, similar cancers have occurred in the unexposed Comparison population of Marshallese. Therefore, one may conclude that in the Marshallese experience the delayed expression of nonmalignant morbidity due to irradiation has indeed been great and far exceeds that of malignant disease. REVIEW OF CANCERIN THE COMPARISON POPULATION In earlier BNL publications neoplasms of the exposed population were comparedto those of an unexposed “Comparison” population with a similar age and sex distribution. However, since the last report, which brought the period of medical coverage up to December 31st, 1984, concerns have been voiced about present-day safety of habitation on Rongelap island. An analysis of the current radiation risk of Rongelap habitation is not a function of the Marshall Islands Medical Program, which is a clinical program devoted to aspects of health care for persons acutely exposed to radioactive fallout in 1954. Nevertheless, medical information collected over many years concerning the unexposed Rongelap people has been requested by different groups who are involved in assessing that risk. To assist them and others who may wish to review the medical experience of the Comparison population, a summary of diagnoses of neoplastic disease is presented here. It is essential to realize that whatever radiation risk exists today on Rongelap is quite distinct from that incurred by 86 Rongelap inhabitants and 167 Utirik inhabitants during the two-day exposure to Bravo fallout in 1954. The reasons for this statement are given below. E. Laryngeal nerve injury: One Rongelap man has a mild but definite impairment in speech resulting from recurrent laryngeal nerve injury, a well-known complication of thyroid surgery. This is not a common complication, occurring in perhaps 1% of patients. As with postsurgical hypoparathyroidism, its frequency dependsgreatly on the experience of the surgeon and the extent of the surgery. F. Pituitary tumor formation: Two women exposed as young children, one from Rongelap and one from Utirik, have developed pituitary tumors. These tumors are usually benign, causing disease, in part, because of their expansion inside a rigid structure. Thereis no knowndirect association between radiation exposure and development of pituitary tumor, but there are reasons to suspectthat pituitary tumor formation may be a consequence of thyroid injury (Adamsetal., 1984). 17