badge data from a nearby military outpost (S055). Our external dose value at Sifo Island, 1.1. gray (110 rad) was greater than the 0.69 gray (69 rad) originally estimated by Sondhaus from post~-evacuation surveys of exposure rate. The difference was due to the presence of very short-lived activation and transuranic nuclides which, according to the nuclide composition, must have been present during exposure at Sifo Island. Medical observations concerning thyroid abnormalities have been tabulated along with the new thyroid dose estimated for each person. From these results, the mean cancer risk rate in the exposed population of 251 people was 150 thyroid cancers per million person-gray~years at risk (1.5 + 2.5 thyroid cancers per million person-rad-years at risk). The mean time at risk for thyroid cancer was 19 years. The uncertainity derived for the estimate of risk was based on the standard deviation in adult mean urine activity concentration, the standard deviation in thyroid absorbed dose per unit intake, and the standard deviation in the spontaneous frequency of thyroid lesions in the unexposed comparison group. In order to avoid unwarrented external and internal dose from the deposited radioactivity, the inhabitants of these atolls were relocated out of the affected area. They returned to Utirik in June 1954 and to Rongelap in June 1957. Environmental and personnel radiological monitoring programs were initiated in the mid 1950's by Brookhaven National Laboratory. The objective was to maintain a comprehensive radiological safety program. Post-return body-burden histories and activity~ingestion rate patterns were determined as were estimates of internal committed effective dose equivalent. External exposure rate and living pattern data were also collected. Relationships ' between body burden or urine activity concentration and a declining continuous intake scenario were developed in order to model retrospective and prospective dose equivalent. The dosimetric conclusions for the protracted exposure are summarized in Table 1 (Le84). Table 1. Dosimetric conclusions for the protracted exposure of Rongelap and Utirik Adults from day of return to 50 years. Rongelap Nuclide : Fe-55 4.8x107* + 2.5x1074 zn-65 $r-90 Cs-137 External 1.9x107> 5.31079 2.2x1072 1.7x1072 Co-60 Uctirik Committed Effective Committed Effective Dose Equivalent, Sv+S.E. Dose Equivalent, SvaS.E. 3.4x107% + 1.3x1074 + + + + 1.0x1072 8.0x107¢ 1elxl072 3.4x107° 3.6x1074 + 2.0x107¢ 4.4x107* + 3.3x107¢ 3.0x1072 1.0x107* 1.3x1072 4.lxl072 + + + + 4.4x107 5.0x107> 1.0x1072 8.2x107> A decline in the daily activity ingestion rate greater than §bat due solely togpadioactive decay was ggtimated to be 9% per yeagfor Cs, 8% per year for ~“Sr, 80% per year for Zn and 60% per year for value of 3% per year for Pu was estimated from sparse data. are aimed at determining the dosimetric impact of Pu. ~~Co. A tentative Current studies These values for the % per year decline in activity ingestion rate were observed at both atolls and do not account for the additional decline due to radioactive decay.