174 Health Physics of “7Cs, its contmuous movement mto coconuts and other fruits via root uptake, as a result of low ““K August 2010, Volume 99, Number 2 concentrations m the soil (Simon et al 2002), leads to longest half-hfe bemg 51 days for “Sr Therefore, most of the mternal dose resultmg from acute mtakes was delivered during the year ofthetest Absorbed doses radionuchides with half-hves of about 1 y or longer When the biological half-trme of residence in the body was longer than I y, the dose from acute mtake was much larger mtakes over the successive years after fallout Annual absorbed doses to RBM, thyroid, stomach Among the radionuclides considered, there were six delivered over several years This 1s, for example, the wall, and colon were estimated for the 26 population groups for the trme period from 1948 to 1970 Cumulative doses over that time period were estrmated as well Four population groups have been selected to illustrate the magmtude and the range of dose over the entire terntory of the Marshall Islands Doses from acute and chronic mtakes will be discussed m turn case for Sr, with a physical half-hfe of 29 y and a biological half-time of residence m the body of about 20 y Tables 12 and 13 present the absorbed dose coefficients to age 70 y for a 1-y-old child and for an adult for the six radionuchdes with long radioactive Doses from acute intakes. Estimation of doses from the acute intakes used dosecoefficients as described that were derived from accepted mternational biokmetic models and adjusted for f, values specific for radionuchdes mgested in fallout particles (see Ibrahim et al both ages, about 100% of the dose 1s delivered to the 2010) Annual doses from acute intakes at each atoll varied primarily according to the amount of deposition from the tests conducted m a given year Fig 3a to 3d illustrates the armual organ dose (mGy) to two tissues (RBM and thyroid) for three different birth years (1930 or before, 1953, and 1957) at Mayuro, Kwayalem, and for half-lives as derived for the Bravo test (1 March 1954) The tables also present the percentage of the dose delivered m each ofthe first five years after mtake For colon wall and to the stomach wall m the first year For the systemic organs, RBM and thyroid,a large fraction of the dose 1s delivered imthe first year, but a significant fraction of the dose 1s also received in subsequent years dueto the biological retention of the radionuchde m the body Doses from chronic intakes. Annual doses to RBM, thyroid, stomach wall, and colon were calculated the Utnk and Rongelap Island community members (after accounting for their relocations) Similarly, Table 10 presents cumulative doses (mGy) to each of four tissues for all birth years from 1931 (or before) through 1958 Since it 1s the mtent of this work to estimate doses for representative persons, BCAD 1s reported for the years m which tests occurred The cumulative doses to mdividual organs are a sum not only overall tests but a sum overall 63 radionuchdes Table 11 presents a summaryof the radionuchdes which were estimated to be the ten largest contributors to total iternal dose from acute imtakes for each of the four tissues and for each of the four population groups for chromic intakes of long-hved radionuchdes for the 26 population groups over the years 1948 to 1970 Fig 4 compares annual doses to thyroid from chronic intakes during the years 1948 through 1958 for three different mity, and Rongelap Island commumty) For the dose to from acute mtakes However, because of the absence of (Majuro residents, Kwajalein residents, Utrk commu- RBM,stomach wall, and colon wall, “Np wasoneofthe five most important nuchdes regardless of the atoll Other mportant nuclides for RBM were ‘Te, Ba and °°Mfo For the stomach wall, the short-lived radioiodmes and rachotellunums ‘I, “I, and *°Te were rmportantat Mayuro and Kwajalem while “Y and °Y were most important at Rongelap For the thyroid gland, the radiotodines and radiotelluriumseasily gave the largest doses though ‘I was the largest contributor at Rongelap and Utrik compared to "I at Kwayalem and Mayuro All of the radionuchdes hsted in Table 11 are short-hved, the birth years 1930 (and earher), 1953, and 1957 Cumulative doses were obtamed as sums of annual doses Cumulative doses were a function of birth year with the largest cumulative doses estimated for persons bor m the years 1950 through 1956 The cumulative dose estrmates for Majuro residents, Kwayalem residents, the Utmk commumty, and the Rongelap Island commumity are presented m Table 14 The doses from chromc mtakes show the same geographical and temporal pattern as the doses resulting short-lived 1odime 1sotopes m the radionuclides that are important to the thyroid doses from acute mtakes, the thyroid doses from protracted intakes are not much greater than the doses to other organs and tissues Similar to the situation for acute mtakes, a few radionuclides contributed most of the organ absorbed dose from chrome mtakes Table 15 presents a rankimg of thosefive radionuchdes (*Fe, “Co, “Zn, “Sr, and '°7Cs) Forall organs and forall four of the atoll and population groups discussed, ‘Cs was either the first or second most important contributor to dose For the Rongelap