150 Health Physics effect into account when the only measurement available August 2010, Volume 99, Number 2 is of '’Cs activity in soil sampled decadesafter thetest. listed in Simonetal. (2010a, Table 1). At every atoll in the Marshall Islands, the Castle series was the predomi- atoll or island, whether it was inhabited or not. For most northern atolls, it was not the case for the mid-latitude The estimated outdoor exposures, from TOA to infinity, are presented in Table 3 for each test and each of the tests, exposures of less than 1 R were estimated at all atolls and islands. Much higher exposures, ranging from 5 to 500 R, were assessed for several atolls in the northern part of Marshall Islands and for several tests of the 1954 Castle series (Bravo, Romeo, Yankee, Koon, and Union). When exposures are summed overall atolls and islands, those five tests account for 99% of the total exposure, with Bravo alone contributing 84%. Estimated tissue and organ doses Annual doses from external irradiation have been estimated for representative persons of the 26 population groups classified into three different age categories (infants, children, and adults). The annual doses are reported for the time period from 1948 to 1970. By 1970, the doses had decreased to very low levels in comparison to the peak observed in 1954. Since the doses are estimated for representative persons who were assumed to have remained on eachatoll with movements between atolls limited to the relocated and evacuated populations (Simon et al. 2010a, Table 3), the doses from external irradiation are proportional to the exposures calculated using eqn (3), which are based on the environmental radiation data (measurements or estimated values) avail- able for each atoll and test. The doses reported for the relocated populations include, where appropriate, contributions from exposures received before evacuation, during the period of resettlement, and following return to the atoll of origin. Estimated annual doses for adults, shown in Fig. 5, were highest in 1954 and then decreased to values that were, in 1970, less than one thousandth of the peak values observed in 1954. The annual doses shownin Fig. 5 are for representative adults of four population groups (Majuroresidents, Kwajalein residents, Utrik community members, and Rongelap Island community members)* that represent a range of deposition densities, as well as a range of exposures in four distinct areas. In Table 4, the doses through 1970 resulting from the Bravo test are compared, for each of the 26 population groups, to the corresponding doses from all the tests of the Castle series conducted in 1954 and from alltests * Note to reader: As indicated in Simonet al. (2010a), we make the distinction in this paper between “residents” of either Majuro and Kwajalein and “community members” of Rongelap or Utrik. In the former case, we are referring to anyone living on those atolls at the time of fallout. In the latter case, we are referring to the entire group of persons exposed on either Rongelap or Utrik and who were members of the group relocated from thoseatolls. nant contributor to the total external dose. While Bravo was responsible for most of the external dose for the and southern atolls. For example, the proportions of the external dose contributed by Bravo for the Rongelap Island community, the Utrik community, Kwajalein residents, and Majuro residents were >99%, 84%, 4.6%, and 23%, respectively. In contrast, among the midlatitude atolls (Kwajalein and others), Yankee was the most important test. The contributions from Yankee to the external dose for the Rongelap Island community, the Utrik community, Kwajalein residents, and Majuro residents were <1%, 4.5%, 39%, and 1.9%, respectively. Among the southern atolls, the Romeo and Koontests were the most important contributors to external dose. The contributions to the external dose from the combination of Romeo and Koon fallout for the Rongelap Island community, the Utrik community, Kwajalein residents, and Majuro residents were 0.5%, 6.5%, 25%, and 61%, respectively. The external doses we estimated for the adult populations of the Rongelap Island and Utrik communities from Bravo are very similar to those estimated previously by Lessard et al. (1985), but our estimated dose for the 18 persons from Rongelap Island who were exposed to Bravo fallout on Ailinginae is about onehalf the dose estimated by Lessard et al. The reason for the differing estimates for exposures on Ailinginae appears to be due to different estimates of TOA,3 h for Lessard et al. (1985) compared to 4 h assumedin this study. As shown in Table 2, the integral dose over the first few days is very sensitive to TOA, particularly within the first day. The exact TOA for Bravo fallout at Ailinginae was not measured directly but was inferred from measurements at other atolls and, thus, is uncertain. Estimates of external doses to representative adults from all tests are summarized in Table 5 according to region of residence. For reference, the populations of each atoll are given in Simon et al. 2010a (Table 2). As shown, the estimated total external doses from 1948 through 1970 to the adult populations of the southern atolls were all on the order of 5-22 mGy, and in the mid-latitude region, 22-59 mGy. The dosesto the populations of Rongelap Island community, Ailinginae, and Utrik community were muchhigher, reflecting the heavy fallout from Bravo, even though the populations were relocated within a few days after the test (Simonetal. 2010a, Table 3). The dose shown for Rongerik in Table 4 (940 mGy)is the estimated dose from Bravo fallout