Acute and chronic intakes of fallout radionuclides @ S. L. SIMoNn ET AL. 187 Table 20. Comparison of equivalent doses (mSv) to four organs of representative adults of four communities from intakes of fallout radioactivity (acute + chronic) with equivalent doses from consumption of naturally-occurring ”'’Po and *'’Pb for an equal number of years and according to two different diets (mixture of local and imported foods and local-food-only diets). All values rounded to twosignificant digits. Population group Organ/Source of exposure Thyroid Fallout (acute + chronic) Natural radioactivity, mixed food diet Natural radioactivity, local-food-only diet RBM Fallout (acute + chronic) Natural radioactivity, mixed food diet Natural radioactivity, local-food-only diet Stomach wall Fallout (acute + chronic) Natural radioactivity, mixed food diet Natural radioactivity, local-food-only diet Colon Fallout (acute + chronic) Natural radioactivity, mixed food diet Natural radioactivity, local-food-only diet Majuro residents Kwajalein residents Utrik community Rongelap Island community 760 5.4 20 7,600 5.4 20 23 5.4 20 67 3.4 20 1.1 55 190 1.9 55 190 1.1 5.4 20 2.4 3.4 20 41 5.4 20 550 5.4 20 5.4 6.0 22 14 6.0 22 210 6.0 22 2,800 6.0 22 [DC*D/OC*D] are also correlated to [DC*'D/OC™'D), the uncertainties in the total thyroid dose to adults from Bravo appear to be close to those of the contribution to the dose due to intake of '*'I. However, in the absence of measurements of '**I and I in urine, and because of the lack of certainty on the nature of the pathways leading to the acute intakes, the uncertainty in the thyroid dose from the radioiodines was modestly increased to a GSD of1.9. The uncertainties in the estimation of the '*'I thyroid dose to children are admittedly greater than those to adults, as there was no measurementof '*'I in urine from children that could be used to validate them. However, the correction for age dependency seems to be well established for all age groups, with the exception of infants, for whom the contribution to the thyroid dose from breast feeding needs to be added. Also, for infants born in 1954, the dose is averaged overall possible dates of birth, resulting in additional uncertainties related to the estimation of breast feeding and of the doses received in utero ICRP 2001, 2004). Table 21 provides a comparison of doses to persons born in the year of tests under two assumptions: (1) averaged over all dates of birth (the BCAD), and (2) assumedto have been born on | January. In this table, we compare the doses for the same four tissues and atolls as before. Though this study is not concerned with doses to identified persons, this table indicates how much greater a person’s dose might be if they were born in the yearof test, but before it took place. As noted earlier, the BCADis the least biased estimate since the choice of any single DOB cannotberepresentative of all persons. Because infants represent a very small fraction of the population, the simplifying 35 55 190 42 55 190 assumption was madethat the uncertainty assigned to adults is also applicable to infants, and to children of any age as well. In comparison to the contributions to the thyroid dose due to acute intakes of ''I, ’°I, and ‘I from the Bravo test, the other components of the thyroid dose received in 1954 by members of the Rongelap Island community (acute intakes of other radionuclides, chronic intakes of long-lived radionuclides, acute and chronic intakes from tests other than Bravo) are very small, so that their levels of uncertainty havelittle influence on the overall uncertainty. For that reason, we assumed that the uncertainty in the thyroid dose received in 1954 by representative persons of the Rongelap Island community is expressed by a GSD of 2.0, whichis only slightly greater than the value used for the thyroid dose from Bravo (GSD of 1.9). We assumethat the uncertainty in our estimates of dose to other organs (RBM, stomach wall and colon) is comparable to that which weestimate for the thyroid. The intakes of the nuclides that account for these doses are assumedto be given bythe ratio of deposition densities which we assume haverelatively small uncertainty. We also assumethat the uncertainty in dose per unit intake for these nuclides is comparable to that for the radioiodines. Finally, we assume the same uncertainties for years other than 1954 since, even though the uncertainty in deposition varies somewhat from test to test, the major source of uncertainty is in QO/D and it should not have varied significantly. The same uncertainty value was assigned to the other population groups (Ailinginae and Rongerik) exposed in the northern group ofatolls.