[ie 19 Tabie 11 ap Estimated Body Burdens of Radioisotopes in Rongel es Analys l Urine hemica Radioc From | Day on People rT Activity, pCi Isotope 89Sr ‘Ba Rare earth group 131] (in thyroid gland) IOSRu Ca Fissile material 1.6 - 2.2 0.34— 2.7 0 = 1.2 5.6 -22.4 0 0 O - 0.013 | - 0.019 —- 0.016 (ug) those in females until the age of 50, The normal rise in lens flecks with increasing age is similar to that found in the mouse, in whichitis felt to rep- resent the gradual accumulation of defective lens fibers descended from abnormal but viable cells residing in the germinal zone of the lens epithelium. The progressive increase in the nonexposedindividual suggests that somefraction of thesecells has been abnormal from the time of lens formation. In distinction to that in the (female) mouse, the rise of lens flecks in the human appears to have a rapid phase coinciding with adolescencein the female, a period oflife during which theratio of estrogen to androgen maybe elevated. The second finding of interest is the greater radiosensitivity (for the production oflens flecks) in females, particularly those aged 13 to 20 years at the timeof radiation exposure. As noted above, this is a period of rapid rise in lens flecks in the normal, and possibly of relatively high estrogen level. Experimental evidence pertaining to theinfluenceof estrogen on radiolethality in the mouse?! suggests the possibility that gonadal hormones may have been at least partly responsible for the difference in radiosensitivity between the sexes, and also for the difference in incidence between adolescence and maturity in the female. Such a mechanism might imply varying radiosensitivity in the female as a function of stage in the menstrual cycle or pregnancyat the timeofirradiation. Little inonexfor ens ite; ual formation wasavailable as to menstrualstatus at the time offallout exposure. Of three women who had been pregnant whenthey received 175 rads, two havefleck counts higher than would be expected for their age, but the fleck count in the third person was below that expected. These data serve only to suggest the possibility ofa gonadal hormone role in radiosensitivity of the optic lens, and definitive answers must be soughtelsewhere. Finally, itshould be emphasized that this survey has involved the counting of small numbers of discrete opacities of diameters measurable in microns. These rare, minute defects, possibly invalv- -. ing only portionsofsingle lens fibers, are extremely unlikely to be capable of any effect on visual function. The dense subcapsular and diffuse nuclear changes commonly seen in persons of ages beyond the sixth decade are far more impressive and functionally important. THYROID FINDINGS Estimation of Dose of Radiation to the Thyroid Glands The calculations of dose to the thyroid from the absorption of radionuclides in the fallout unfortunately could be made only from radiochemical urine analyses obtained several weeks after the accident. These calculations are summarized briefly here (see BNL 50029?! for details). In addition to 131] the isotopes 133], 135I, and to a lesser extent 132] in the fallout contributed significantly to the thyroid dose. The only direct data available on the Rongelap people are radiochemical analyses of pooled urine samples taken 15 days or longerafter the fallout. At 15 days the urinestill contained smal} amounts of 1311. The dose to the thyroid from 1311 on the first day of the fallout was estimated to be 11.2 pCi (5.6 to 22.4 wCi) assumingthat 0.1% (0.05 to 0.2%) of the maximum thyroid burden (not corrected for physical decay) was excreted in the urine on the 15th day. Table 11 showsestimated body burdens of various isotopes on day 1. The dose of 160 rads to the adult thyroid was calculated from oral intake and inhalation of the combinedvarious iodine isotopes, consideringtheir fission yield, the average energy deposited in the thyroid per disintegration, and the time of absorption. The dose to the thyroid glands of children 2 to 4 years of age wasthen calculaby means of these factors with consideration of pulmonary function and the thyroid size of the child of that age. The main source of iodine ingestion was considered to be water, and since it was being rationed at the time offallout it was assumed that the children drank the same amountas adults and therefore had the same thyroid burden of radioiodines. The small size of the children’s thyroid resulted in a substantially larger dose. The total estimated