117 Radiation doses and cancerrisks in the Marshall Islands @ S. L. Simon ET AL. contributor to dose for the residents of all other atolls With respect to the total internal dose relative to the (Table 15, Simon et al. 2010). external dose, external doses were muchgreater than the same geographic pattern as for '*’Cs deposition that is the Utrik and Rongelap Island communities). Internal doses to the thyroid were significantly greater than external doses, regardless of the population group. The cumulative thyroid doses (mGy) to representative adults on each atoll from both acute and chronic intakes of radionuclidesin fallout from all tests with 90% uncertainty ranges are presented in Table 5 and have the internal doses to RBM and stomach wall, regardless of the population group, but were comparableto the internal doses to the colon wall (greater by two-fold at the southern and mid-latitude atolls, and about one-half for illustrated in Fig. 2. Comparison of doses by mode of exposure. Table 6 compares estimated cumulative internal doses to representative adults of four population groups as reported Total doses. Total (external plus internal) organ absorbed doses can be presented in various ways to demonstrate the spatial and time-dependence of exposures received across the Marshall Islands and the dependence onageat exposure. Asdiscussed earlier, Fig. 2 illustrates the groups of the atolls within the Marshall Islands with similar degrees of deposition. In parallel, Table 7 presents population-weighted total doses to adults within each of the four geographic areas. We found that our estimated total doses are relatively comparable within each of the four population groups: in Simon et al. (2010) with the external doses for those same population groups as reported in Bouville et al. (2010). As elsewhere in this paper and companion papers, those personsof adult age (>18 y) at the time of the first test with significant deposition (Yoketest, 1 May 1948) are considered as adults in this assessment. In addition, all dose estimates presented are best estimates based on an analysis of all available data. With respect to the components of the internal dose, the dose from chronic intake exceeded the dose from acute intake for RBM and stomach wall, for all populations groups except the Rongelap Island community. For the Rongelap Island community, the acute doses for all organs exceeded the chronic doses. Because of the exposure to residents of southern atolls, residents of mid-latitude atolls, the Utrik community, and the Rongelap Island/ Ailinginae/Rongerik evacuees (Table 5). Here, as elsewhere in this paper and companion papers, both Fig. 2 and Table 7 demonstrate that adults in mid-latitude atolls received cumulative organ doses approximately four times as great as adults in the most southern atolls. Similarly, adults of the Utrik community received cumulative organ doses four to seven times as great as adults radioiodines in fallout, the absorbed dose to the thyroid gland from acute intakes exceeded the chronic dose to the thyroid, regardless of the population group. Acute doses to colon wall were also greater than the corresponding chronic doses for all four population groups. Table 6. Comparison of best estimates of cumulative internal and external dose (mGy) to adults of four representative population groups for four organs. All dose estimates rounded to two significant digits. Population group Organ/Mode of exposure Majuro residents Kwajalein residents Utrik community Rongelap Island community Thyroid Acute internal 22 66 740 7,600 Total internal 23 67 760 7,600 Chronic internal RBM Acute internal Chronic internal Total internal Stomach wall Acute internal Chronic internal Total internal Colon Acute internal Chronic internal Total internal Whole body (external dose) 0.76 1.3 25 14 0.11 0.98 1.1 0.25 1.7 2.0 2.3 33 35 25 17 42 0.32 0.75 1.1 1.1 . 2.4 16 24 40 530 14 540 4.4 12 180 2,800 5.4 9.8 14 22 210 130 2,800 1,600 0.99 1.7 32 17