186 Health Physics Table 19. Comparison of estimates of acute and chronic internal doses (mGy) with external dose (mGy) for representative adults of four population groups. Population groups Organ/Mode of exposure Majuro residents Kwajalein residents Utrik community Rongelap Island community Thyroid Acute Chronic RBM Acute Chronic Stomach wall Acute Chronic Colon Acute Chronic Whole body (external dose) 22 0.76 66 1.3 740 25 7,600 14 0.11 0.98 0.25 1.7 2.3 33 0.32 0.75 1.1 1.3 16 24 530 14 180 2,800 4.4 0.99 9.8 12 1.7 22 32 130 25 17 17 1,600 August 2010, Volume 99, Number 2 Uncertainties in D/Q. The uncertainties in the thyroid dose per unit '*'I intake, D/Q, are relatively well documented (for example, Dunning and Schwarz 1981; Zvonova 1989; NCI 1997; Apostoaei and Miller 2004). They depend essentially on the uncertainties on the fractional thyroidal uptake and on the thyroid mass, as well as on the degree of correlation between the two parameters. Considering that the quantity of interest 1s the average thyroid dose per unit intake for adults of the Rongelap Island community, a direct approach was taken: the six possible sets of parameter values for the thyroid biokinetic model that are presented in Table Al were used to quantify the variations of the value of D/Q for '*'l. The obtained range of values is from 4.3 to 6.1 X 10°’ Gy Bq|, resulting in a GSD of1.2. Using values of 1.0, 1.6, and 1.2 for the GSDs of C, O/C, and D/O,respectively, the GSD for D('*'I, Bravo, adults) is estimated to be 1.7. There are additional uncertainties involved in the estimation of the overall uncertainty in the annual doses received by representative persons of the Rongelap Island community. They include: where K =the correction factor corresponding to the radioactive decay of '*'I between time of sampling and time of counting; ® uncertainties in the contributions of ‘I (20.8 h) and I (6.6 h) to the thyroid dose to adults from the Bravo test, which are estimated to be 4,200 and 1,300 mGy,respectively, and, V=the 24-h urine volume (mL) averaged therefore, of the same order of magnitude as the thyroid dose EF(t) = the urinary excretion fraction for '*'I on day © uncertainties in the estimation of the thyroid dose to over the sample population; and of sampling, t being the time elapsed between intake and sampling. Because of the relatively long half-life of '*'T (8 d), the uncertainty for K is very small. Uncertainties on V are discussed in the Appendix and in Harris et al. (2010): the mean 24-h urine volumes averaged over the sample population are 427 and 448 mL for the samplings on March 16 and 17, respectively (Table 7); the distributions of the mean are assumed normal with standard errors of the mean of 42 and 37 mLfor the two days of sampling. For this analysis, the mean and the standard error of the mean were taken to be 440 and 40 mL,respectively. The uncertainties in EF(f) are related to those in the parameter values of the biokinetic model. In Appendix A, six possible sets of parameter values for the thyroid biokinetic model were used to quantify the variations of the value of EF(t). Results, presented in Table Al, suggest for the Rongelap Island community a range of values from 0.92 to 2.3 X 10 * around an arithmetic mean value from '*'I (1,700 mGy); children; and © uncertainties related to small components of the thy- roid dose due to acute intakes of '*’Te and '*"I from the Bravotest, thyroid doses due to chronic intakes from Bravo, and to acute and chronic intakes from other tests of the Castle series. The contributions of "I (20.8 h) and '*I (6.6 h) account for about 75% of the thyroid dose from the Bravotest to adults of the Rongelap Island community. As all other radionuclides collectively contribute no more than 25% of the thyroid dose from Bravo, a good approximation of the thyroid doseis: D(total) = D?"'1D + DUD) + DUD 133 O(!**1) = D(3!]) x f + om of 1.7 X 10 4, leading to a GSD of1.6, assumingthat the range of values correspond to one GSD. Using the numerical estimates of the GSDs for V and for EF(t) indicated above, the GSD for Q/C for adults of the Rongelap Island community exposed to acute intakes of 'S'T from the Bravo test is found to be 1.6. 135 =D(""'1) x r + a + aT D(3'T) ox O(!?'T) aT D(3'D/OC3D) | DC3'1veC3!1 14) . Becausethe values of Q('*"1) and Q(’"I) are correlated to Q('**1), and the values of [DC*D/OC*D] and