Table 2. Population breakdown by age and geographical living patterns. Infants and small children Children and adoiescents Men Women -4 $-19 20+ 20+ 16 41 22 21 inside nome 50 30 30 20 Witnin 10 m of home 15 10 5 10 Elsewhere in village 5 10 5 10 Beach 5 S 5 5 Interior of island S 1S 20 15 Lagoon 0 10 10 5 20 20 25 25 ‘ce bracket ‘vears) -taction of population (%) Fraction of time spent in respective areas (%): Other islands shown as area 3 in Fig. 4. od 6 are identical. As far as the external dose assessment is concerned, cases 5 Since the exnected living natterns are most likely to differ between the various age groups, it is necessary to utilize the age distribution data presented in Table 2. These data were obtained from the 1974 census taken on Kili Island of the 784 persons who claim land rights on Bikini Atoll.4 The geographical living patterns, aiso shown in Table 2, were assumed to be similar to those expected for the returning Enewetak people. Even though the gamma-ray exposure rates vary widely, it was necessary, for the purpose of the external dose calculations, to derive the most reasonable values of the mean exposure rates for each specific geographical area under consideration. ‘cf in Table 3, The vean exposure These are cates for specific areas on Bikini Isiane «ere obtained by weighting the mean exposure rates within each contour interval with the area within the contour. Since the exposure rates on Eneu Island are relatively uniform, the mean exposure rates were chosen by inspection of Fig. 3. the other islands of the atoll, Since this survey did not include it was necessary to rely on data from previous surveys to estimate the contribution the radioactivities on these islands make to the total population dose. Gamma exposure rate data reported by Bennett and Beck,“ Held,” Lynch et al.,° Gustafson, ’ Smith and Moore,° and Robison et al.? were used for this purpose. Their results in conjunction with a simplified area weighting scheme yielded the values presented in Table 3. It should be pointed out that these are rough estimates since the data are scarce and were collected over a span of almost ten years. The exposure rate over the lagoon was estimated to be 3.3 uR/hr due to the cosmic ray contribution and an additional