-3- -2- If we assume a Inear buildup of fallout from H +8 to H + 18, ¢7)-4 decay during this interval, and use the reading of 375 mR/hour at 7 daye, Experience from Sedan indicates that the dose from the cloud itself is approximately equal to {Ouax. nao all the dose from fallout during cloud passage. The total estimated dose ia then 47 +47 +114 = 208 R. Within the error of the measurements and the accuracy of the assumptions, this estimate, which does not contain any correction for the small effect of time indoors, does not differ significantly from the value of 175 R.! We will, therefore, take the average whole-body gamma dose as 175 + 25 R. Res| en ~see_iapeeaieeneetlinamm Rann mn om Unfortunately, no direct measurement was possible on the radioactive which the average thyroid burden of Urine samples were taken from se has been estimated. The Los Alamos Scientific Laboratory collected pooled 24-hour samples 15 days post-detona- tion and estimated” the 1-day thyroid tontent as 11.2 nCi of 271. usNRDL collected samples from each member of the exposed group 43 and 46 days post-detonation and, by an indirect method, estimated the average thyroid AdOou i\Ouax } 4.8 1 4,829 20,1 al 18,011 75.0 >16 Volume The urine samples are typical of adults and the calculated thyroid burdens are presumably also those of adulta. Associated with this yp4} are the shorter-lived isotopes p33 33 and 235. If the iodine entered by wayof inhalation, the time of intake was H+6toH +18. On the other hand, if water (and food) were the principal source, the time of ingestion would be extended from H + 6 to H + 51. iodine isotopes. These are: average energy deposited in the thyroid per disintegration. are presented in Table I for 1333 and 135 distribution in the cloud was assumed. These factors In the case of inhalation, uniform For oral ingestion it was assumed that, on the average, one-third of the intake occurred at H + 10 and two- thirds at H + 30. Table I. Ratio of doses for the two modes of intake. Inhalation The value of 11.2 wCi will be used as a basis for This estimate was based on the assumption of (1) radioactive decay before inhalation or oral ingestion, (2) differences in the fission yields of the chains,® and (3) the obtained by direct counting of y3h in the urine and should be more reliable all following considerations. 1,155 5-16 content as 6.4 pCiT!9! at 1 day.) * The LASL estimate of 11.2 pCi was than the NRDL estimate. 7 <6 Three items contribute to the differences in dose from the various Internal Deposition of Iodine Isotopes iodine content of individuals from Rongelap. % of Total Urine (ml) Oral Ingestion y2337,131 p55),131 133),131 p35, 351 Decay Fission yield® 0.68 0.31 0.487 0.1% of the maximum thyroid burden being excreted in the urine on the 15th day. Energy 2.00 1,50 2.00 1.50 1.85 0,57 Se 0.27 Variation in the biological half-life and other factors indicate that a range of 0.05 to 0.2% should be placed on this number” (see appendix). We, therefore, take 5.6 to 22.4 wCi as the range of adult ps! thyroid burden. The pooled samples represent all age groups. The number of individuala in these age groups and the volume of urine from each age group is approximately as followa: ‘ 4 Net Facior 1.38 1.23 1.38 0.148 1.23 * The dose to the thyroid in rads from all three isotopes fa thus 3.4 times the dose due to ysl alone for inhalation and 2.6 timea the 31 dose for oral ingestion. Delay inreaching the thyroid after inhalation or ingestion would lower these factors somewhat. However, the 333 daughter of the 78-bour Te? has been neglected and would approximately compensate for decay of 133 gna 1335 before reaching the thyroid. We can now prgceed to estimate the dose to the thyroids of 3- to 4year-old girls assuming (1) inhalation as the mode of intake and (2) oral ingestion, Tee ee eee eet eer ees ne eafnet hs the fallout from H + 18 to evacuation at H +51 is 114 R. The dose from Volume of Individuals ee the estimated dose from fallow during cloud passage is 47 R. Number of Age Group