BEST AVAILABLE COPY Paay June 23, 1966 THE NEW ENGLAND JOURNAL OF MEDICINE ronment highly contaminated with radioactive material. The radioisotopes of strontium, barium and iodine, along with some of the rare earths, were ab- sorbed in greatest amount. Probably, only isotopes of iodine exceeded the accepted permissible levels. No acute effects of exposure from the internally absorbed redionuclides were observed. Since their return to Rongelap in 1957 the people have been exposed to low levels of certain residual radionuclides — namely, Csi" Zn(this is an induced radtoelement) and Sr’. Body burdens appear to have reached equilibrium with the environmental levels of these elements, and are well below the accepted permissible rane, LATER FINDINGS Evaluation of the general health status, illnesses, mortality, fertility and aging over the eleven years since exposure has revealed no significant differences between the exposed and the unexposed populations that could be attributed directly to raclia- tion. The slight lag in recovery of peripheral blood elements has not affected their resistance to disease and immunologic competence. Although the birth rate has been about the same in the exposed and unexposed vroups there was an apparent increase in miscarriages and stillbirths in the exposed women as compared with the uexposed women over the four vears after exposure (41 per cent, or 13 of 32 pregnancies in the exposed, as compared with 16 per cent, or & of 49 pregnancies in the unexposed women over a comparable peniod). A few congenital abnormalities have been observed in babtes born to exposed women, but no correlation with radiation seems possible at present. Slit-lamp observations have failed to reveal radiation-induced opacities of the lens. Stucdies of growth and development? comparing 42 caposed with 75 unexposed children have revealed a shieht retardation of growth in the bays exposed at one to five vears of awe, most marked in those exposed at twelve and cighteen months of age. The possibility: that radiation was a causative factor will be discussed heter. CONSIDERATION OF THE RADIATION DOSE TO THE THYROID GLAND radioiodines have been made: 150 rads (from direct measurements of urinary I); 100 rads (by indirect measurements using animals — pigs removed from Rongelap ~— and Marshallese urinary-excretion data)’; and 160 rads (based) on recent recalculations of early data).® The last reealculations® were based on analysis of pooled urine samples mainly from adadt Rongelap people taken fifteen days after deto. nation; an estimate of the one-day thyroid content of I) was bL2 microcuries (5.6 to 22.4 microcurics) assuming that 0.1 per cent (0.05 to 0.2 per cent of the maximum thyroid burden was excreted in the urine on the fifteenth day. The dose of 160 rads te the adult thyroid) gland was caleulated from oral intake and inhalation of the various todine isotopes, considering their fission vield, the average energy deposited ino the thyroid wland= per disintegration wid the time of absorption. The dose to the thyroid the exp lation. | not den proced has app twenty-! micro“ Tn 18 year-old have al ditional exposed March, were mK ave ane woman. was Cill with no source of fodine ingestion, and since water was being found. in the rads. In thyroid nodular: rationed at the time of the fallont, it was assumed that not vlands of children three to four vears old) was then calculated by means of these factors with considera tion of pulmonary function and the thyroid s.ze7 of a child that age. Water was regarded as the main the children drank the sume amount of water as adults and therefore had the same thyroid burden of radioiodines, Because of the small size of the gland the beta dose of radiation to the gland was substantially larger. The total estimated dose from the varieus iodine isotopes to the child's gland was about LOOO rads, ws''ea ine nature « CASES W inciden: exposed finiction PTOryps nunimiun of about FOO rads and a maximums of | 00 rads. The ghinds received an additional 175) rads front external gamma radiation. Details of these calculations have been given bs James and Gofiman.§ Though the skin overlving the thyroid ghand was recat ¢ that the deposits of radioactive materials in this area added significantly to the thyroid dose since mast of the beta irradiattons were of gisuffictent energies to have penetrated to the depth of the gland. cidence frequently the site of “beta burns” it is not believed ths roid pothyre at less t The an males (. fernale. Pyriust ABNORMALITIES OF THE THYROID GLAND Phivsical examinations have always included care- ful inspection of the thyroid region in both exposed and unexposed comparison groups. In addition, the gland and the relative proportion of the several determinations of the level of protein-bonnd iodine and cholesterol in serum have been carried ont al various intervals since 1959 in some persons. Until 1963 no thyroid abnormality was detected in cite! in fallout is well known. In addition to ['#. the ment seen in an unexposed woman. The average level of serum protein-bound iodine was found to Calculation of the dose to the thyroid ehind from ridioactive iodine requires knowledge of its uptake by the gland, its half-life in the gland, the size of Yo 27 radioisotopes of iodine. Unfortunately, in the present situation few data of a direct nature are available. The relative distribution of radiciodines the exposed or the comparison population, except isotopes of B33) 23 and to a lesser extent Icontributed significantly to the thyroid dose. The only data available are radiochemical analyses of pooled urine samples taken fifteen davs and longer after the fallout. Three separate estimates of the dose to the thyroid) glands of adult Rongelap people from be elevated in both the exposed and comparison populations. It is believed that this is a racial char acteristic, and that the increase is partly due to an increased level of the iodoprotein fraction of serum. No significant differences were noted between the mean protetebound iodine and cholesterol level: im for 1 case of asymptomatic diffuse thyroid enlarge- A, LB Ft A.B A ALT + I th, tH] > "tat uch pre wasead