Radiation doses and cancer nisks mm the Marshall Islands @S L Simon er au was developed by the Off-Site Radiation Exposure Review Project (ORERP) for estimatmg external whole-body dose from fallout origmatmg at the Nevada Test Site (Hicks 1982) The annual and cumulative exposures derived from the estimate of E12 were estimated by Bouville et al (2010) usmg the variation with time of the exposure rate calculated by Hicks (1981, 1984), but modified to take fractionation mto account, where necessary, as well as the “weathering effect” which reflects the gradual decrease of the exposurerate caused by the migration ofthe deposited activity into deeper layers of soil The conversion factors from free-im-air (outdoor) exposure to tissue absorbed dose depend on the energy distribution of the gamma rays that are mcident on the body and on the organ for which the dose 1s bemg estimated However, for most of the fission and activa- tion products that are created during a nuclear explosion, the gamma-ray energies resulting in external exposure are a few hundred keV or more and the variation m photon energy results m at most a few percent difference im dose per umt mcident fluence for the various organs considered m this study (Jacob et al 1990) Thus, energy and organ dependence m dose conversion factors were not taken mto consideration, a smgle conversion factor, 66 X 10mGy per mR, was used for adults for all organs However, the conversion factor does depend on the ageof the person, or, more precisely, her or his body size and shape Thus, based on calculations usmg anthropomorphic phantomsthat represented different ages (Jacob et al 1990), our calculated doses to adults from external irradiation were mcreased by 30% for children less than 3 y of age and by 20% for children 3 y of age through 14 y While age and body size were important for the estrmation of external dose to the organs considered, sex was not Building shielding was estmated not to be rmportant smce housesat that time, made primarily out of palm fronds, did not provide any substantial reduction of gamma ray mtensity Annual absorbed doses from external irradiation from all 1mportant tests were estimated for the time period from 1948 through 1970, that 1s, until the annual doses had decreased to very low levels m comparison to the peak values observed m 1954 These annual doses were estimated for the relocated populations and for the populations continuously resident on all mhabited atolls of the Marshall Islands im three age categories (mfants, children, and adults) The doses reported for the relocated populations mclude, where appropriate, contributions from exposures received before evacuation, during the period ofresettlement, and following return to the atoll of 11S origin (Table 3) Annual doses to adults from external irradiation are presented m Bouville et al (2010) along with estrmated uncertamties, the doses were highest during the years of atmospheric testing m the Marshall Islands, after which they decreasedto values that were, in 1970, less than 01% of the peak values observed in 1954 Our best estrmates of the total external doses (mGy) from all tests and of the 90% uncertamty ranges are presented m Table 5 for representative adultsofall 26 population groups The geographic pattern oftotal external doses received 1s the same as for the deposition of "Cg illustrated m Fig 2 and, as described, 1s much higher m the northern atolls than m the central and southern atolls Internal doses from acute intakes of radionuclides. The mternal radiation doses resulting from acute imtakes, defied as those that occurred during or soon after fallout deposition, were assumed to be primarily a consequence of mgesting radionuclides im, or on, debris particles that contammated food surfaces, plates and eating utensils, the hands and face, and, to a lesser degree, drmkmg water (Lessard et al 1985, Simon etal 2010) Internal doses from other pathways of exposure, im particular, mhalation, were much lower than those due to mgestion and have not been exphiitly estimated mthis assessment Fallout particles at northern atolls were typically large (tens to more than one hundred micrometers m diameter) resultmg in generally low mtakes by mhalaton Fallout deposited at southern atolls, even though generally composed of smaller sized particles, was often deposited with ramfall which sigmficantly reduced the availability of the particles to be mhaled Annualrainfall rates are three to four mes greater im the southern atolls compared to the northern atolls (Amow 1954) The methods used 1mthis study for estimatmg acute intakes of fallout radionuchdes and resultmg doses are based on (1) the estimates of test-, atoll-, and radionuchide-specific deposition densities discussed m Beck et al (2010), (2) istorical measurements of "I in pooled samples of urine collected from adults about two weeks after the Bravo test (Harris 1954, Harris et al 2010), and (3) assessment of appropriate values of gastromtestinal uptake for the radionuclides present in fallout particles (Ibrahim et al 2010) The assessment of iternal doses was composed ofthe followmg six steps (1) estimation of the mtake of ‘I by populations on Rongelap, Ailmginae, and Rongertk, following the Bravo test usmg historical bioassay data, (2) estimation of the imtakeof 'Csat the samethreeatolls based on the ratios of Cs to “I calculated by Hicks (1981, 1984) but