Acute and chromic mtakesof fallout radionuclides @ SL Simow er av would be, at most, 5 mGy to the colon walls of persons 181 A comparison of the doses from routme mgestion of who would exclusively consume goatfish flesh from the Enewetak lagoon and to doses of less than 1 mGy to the other organs and tissue of consumersofreeffish Po and *"Pb with doses from mgestion of fallout doses are vastly overestimated because the residents of Bikim and Enewetak were evacuated m 1946 and 1947, respectively (Table 3 im Simon al 2010) and from “Pb and “Po, and electrons and photons for from Bikim lagoon It 1s clear, however, that these because the “’B1 concentrations m fish from lagoons other than Bikim and Enewetakare likely to have been much lower Comparison of internal doses to external doses Table 19 compares the estimated acute and chromic doses to an adult for four organs at the four representative atolls with the external doses as reported m Bouville et al (2010) for those same atolls Except for doses to the thyroid gland, the external doses were comparable or much greater than the internal doses As discussed previously, the chrome doses for thyroid were small compared to the acute doses, but the chromic doses to stomach and RBM were comparable orgreater than the acute doses (except for the Rongelap commumty) How- ever, the calculated chrome doses were mainly due to ingestion of Zn (Table 15) and are very uncertam simce, as discussed previously, they are very dependent on assumptions regardmg the mtake of *Zn atatolls other than Rongelap Comparison of internal doses from fallout to internal doses from natural background radioactivity It 1s useful to compare the estrmated acute and chromic doses to Marshallese from ingestion of fallout radioactivity with estimates of dose from mgestion of natural radioactivity m the diet Coral-based soi] 1s low m natural radioactivity, resultmg 1mhttle natural radioactivity m locally grown foods, hence, seafood provides the largest amount ofnatural radioactivity to the Marshallese diet (Noshkin et al 1994) Though the diet of the Marshallese m years past has been difficult to reconstruct precisely (NAP 1994), reasonable estimates of annual itake are possible Dependmg on assumptions made about the proportion of the diet from local foods compared to imported foods, the annual mtake by adult Marshallese was estimated by Noshkin et al (1994) to range from 800 Bq (mixtureof local and imported food) to 3,000 Bq (local food only) for *"Po, and from 130 Bq to 240 Bq for “°Pb While Noshkim et al (1994) used these mtakes to estimate effective doses, we used their estimates of intaketo calculate organ equivalent doses so that a more direct comparison can be made with our estimated organ absorbed doses resultmg from exposure to fallout radioactivity 1s complex for several reasons (1) The types of radiations that give mse to the doses are different predommantly alpha particles for the doses fallout radionuclides from nuclear weapons tests Consequently, a radiation-weighting factor equal to 20 1s necessary to determme the equivalent doses from “Pb and *"Po, while the factor 1s equal to 1 O for the doses from fallout In this comparison, the doses are expressed m terms of equivalent dose (mSv), as that quantity 1s generally proportional to the radiation risk, (2) The equivalent doses that result from mtakes of the radionuchdes considered vary according to age, m this comparison, only the equivalent doses to adults are estrmated, (3) The annual equivalent doses from naturally-occurring radionuchdes are considered to be constant over time unlike the doses from fallout that were highest m 1954 and generally decreased unt] 1970 In this analysis, the fallout equivalent doses accumulated from 1948 through 1970 are compared with doses from natural radioactivity im foods for the same number of years Therefore, the estimated annual equivalent doses from natural radioactivity were summed over 23 y, (4) The equivalent doses from fallout varied substantially among groupsofatolls, whereas the doses from naturally-occurrmg radionuchdes were considered to be the same atall atolls of the Marshall Islands The results of the comparison are presented in Table 20 for representative adults of the four commumties discussed throughout this paper Two general findmgs emerged, regardless of the atoll (1) the equivalent dose to RBM ofadults from mgestion of fallout was estrmated to be substantially less than the equivalent dose from ingestion of naturally-occurrmg *"°Po and *"°Pb over an equal number of years of mtake, and (2) the equivalent dose to the thyroid of adults from ingestion offallout was greater than the equivalent doses from naturally- occurrmg **Po and “Pb At southern and mid-latitudeatolls, best represented by Mayuro and Kwayalem, respectively (Fig 2, Simon et al 2010), the equivalent doses to the stomach wall and colon from exposureto fallout were smaller than the equivalent doses from mgesting naturally-occurrmg *"°Po and “Pb Of the two diets, the local-food-only diet would give a larger dose from naturalradioactivity The thyroid equivalent dose for membersof these commumities was only shghtly greater from fallout than from imtakes of naturally-occurrmg “Pb and *°Po (20% to 33 times larger) These relationships would apply to about 96% of the population alive durmg the testmg years (73% who ved m the southem atolls and 23%. wholived m the mid-latitudeatolls)