bate Moore, EPA, referenced in your letter contains results of this effort along with the additional radiation measurements made during cleanup. An additional independent estimate of exposure due to external radiation was made by Smith and-Moore for a child born on Bikini Atoll in 1970. The 5, 30, and 70 year values may be compared with Gustafson's estimates for the same times for "External" exposure. Part of the difference between the two sets of values, for instance 3.33 rads in 30 years by Gustafson versus 5.3 rads for Smith and Moore (5,275 mrads is 5.3 rads), comes from a correction made for external radiation contribution from cosmic ray exposures in the reported data used by Gustafson, Note that the reported radiation levels in the Smith and Moore report include natural sources. report. See footnote on page three of that The cosmic ray measurements at Bikini made by the AEC Health and Safety Laboratory (HASL) indicated a dose rate of about 3.4 wR/hr (microroentgens per hour). The 30 year exposure from this source would be 3.4 uR/hr x 24 hr/day x 365 day/yr x 30. This would be about 0.9 R/30 years. A proper comparison of the two values, including natural background for each, would be about 4,2 versus 5.3 rads. It should be noted that these estimates do not include any credit for reduction of exposure that may come from use of coral gravel in the village area or from the shielding provided by housing. Conversely, the Smith and Moore estimates do not include any contribution from internal radioactivity. Since internal radioactivity comes through the food chain the contribution to the total dose from that source will change with time as locally produced foods become available. We plan to continue to make periodic surveys and to update dose estimates as new information is obtained. —_— Such estimates will, 5009583 of course, include internal