and for the people living at Utirik Atoll, external dose estimates were made, and the results are presented in Table 15. These dose estimates were made based upon the following assumptions or observations: 1) The exposure rate was relatively uniform throughout the atoll. 2) The average exposure rate represents the average for all islands within the atoll. 3) Wotje and Ailuk Atolls are representative of the natural background in the Northern Marshall Islands. It is difficult to estimate an external dose for the inhabitants of Rongelap Atoll apart from typical residents who spend most of their time on Rongelap Island. The reason lies in the nonuniform distribution of radioactive material from island to island within the atoll. While the southern islands of Rongelap were determined to have uniform exposure rates on a per island basis, there were significant differences in the exposure rates between islands and substantial heterogeneity in exposure rates on any given island in the northern sector. In UCRL 51879 Rev. 1 (3,4), this problem was approached by estimating the fraction of the time that an individual spends on various activities. mate is reprinted here as Table 16. This esti- Using this as a basic assumption, we have constructed external exposure rate estimates for the various living activities based upon our measurements reported in Tables 1-13. The value for the lagoon exposure rate was assumed to be the same as that for uncontaminated atolls in the region (~3.7 uR/hr). The value for “other islands" was obtained by assuming that the Marshallese would spend an equal amount of time on each of the other islands which we surveyed. All other estimates are made by taking the average of all measurements made within the area of interest,