the children than in adults. No acute effects of the internal expo- sure to the radionuclides were noted in the people and the full significance of this exposure was not appreciated at that time. Until the development of thyroid abnormalities six years ago, only a few possible late effects of exposure were observed in the Rongelap peo- ple. These have been described in detail in other reports'* and are only briefly summarized here. During this period the general health of the exposed population remained about as good as that of the unexposed population living on the same ‘island with no illnesses that could be attributed to radiation exposure. A slightly higher death rate was noted in the exposed group but this may have been due to the larger number of older people in that group. Of possible significance has been the continuing slight depression of the mean peripheral blood levels in the exposed population compared with those that were unexposed. About twice the incidence of miscarriages andstillbirths were - noted in the exposed women during the first five-year period but general fertility in the exposed people appears to have been about the same as that in the unexposed based on the numberof live births. No malignant lesions of the skin and no cases of leukemia have developed. Two cases of cancer of the female genital tract in exposed women compared to none in the unexposed group have occurred. Attempts to quantify aging changes did not indicate any premature aging effects in this exposed population. Studies of chromosomes and peripheral blood cultures of the Rongelap people ten years after exposure indicated that small numbers of chromosome aberrations of the type usually associated with radiation exposure werestill present. One of the more important find- JAMA, Oct 12, 1970 © Vol 214, No 2 o’ IO Zou | ings noted within a few years after radiation exposure was slight retardation of growth in some of the exposed children as evidenced by extensive anthropometric measurements and skeletal maturation studies. The retardation of growth was most notable in boys who had been exposed when less than five years of age, particularly in two boys exposed between 15 and 18 months of age.* Thyroid Lesions Estimations of Radiation Dose to the Thyroid Gland.—Unfortunately the calculations of dose to the thyroid from the absorption of radionuclides in the fallout had to be based on radiochemicalurine analyses that were obtained several weeks after the accident. It was known that there were several isotopes of iodine in abundance in the fallout (?°"I, 193] 193] 1357). These io- dine isotopes gained entry into the body from inhalation and from consumption of contaminated food and water during the two days before the people could be evacuated from the island. It was calculated that the thyroid gland on the average accumulated roughly 11.2 micro- curies of '*'I on thefirst day of ex- posure. The extrapolated dose to the adult thyroid of the people on Rongelap was 160 rad from all the radioactive iodines plus 175 rad from gamma radiation. Due however, to the smaller size of the thyroid gland in children and to other factors it was estimated that the thyroid of a 3- to 4-year-old child received 700 to 1,400 rad from radioactive iodines in addition to 175 rad of gamma radiation. In view of thyroid atrophy that developed in two boys it must be conceded that the doses to the thyroid in these two patients must have been considerably higher. Early Thyroid Studies Even before the development of thyroid nodules was noted the evaluation of thyroid status of the exposed individuals received con‘siderable attention since it was recognized that the slight growth retardation noted in some of the children might be related to radiation effects on that gland. However, based on physical examinations and serum protein-bound iodine (PBI) and cholestrol determinations each individual examined was believed to be euthyroid. Later, studies of serum iodines indicated that the Marshallese normally possess higher levels of iodoproteins than is usually found in other populations. Thus, the higher-thanexpected PBI values in some patients may have obscured incipient thyroid deficiency at the time of early observations.* Development of Thyroid Lesions Nine years after the accident an asymptomatic thyroid nodule was detected during routine annual physical examination in a 12-year-old girl and the following year, two 13year-old girls who had been exposed were also found to have nodules of the gland. Since then, increasing numbers of thyroid abnormalities have appeared in the exposed Rongelap people. In 19 people nodularity of the gland has been the prominent finding while in two additional boys atrophy of the gland has developed. The nodules were usually multiple, nontender, and varied in consistency. In some instances enlargement of one or both lobes was noted. Surgical exploration, to be described, has been carried out in 18 of the 19 nodular thyroid glands. Benign adenomatous lesions were found in all with the presence of malignant lesions also present in three of these patients. One adult with somewhatless significant nodularity of the thyroid is still under observation. In view of the seriousness of these developments in the thyroid a panel of exThyroid Neoplasia—Conard et al 317