Ronge lap were observed at Utirik for the 90Sr and 137Cs nuclides. curve on Fiyure 16 reflects the dose equivalent, The lower dose equivalent rate and body burden which would have occurred had radioactive decay alone accounted for the removal ot! 0°25 from the Utirik environment. be measured for othe: Since additional mechanisms could nuclides at Utirik and for the 6505 nuclide on a nearby atoll, th: upper cur ‘e was chosen as the most likely body burden history for adults post return tu Utirik Atoll. Figure 17 indi: ates the Utirik adult mean total body dose equivalent rate for each nuclide. Au obvious difference relative to the Rongelap history exists, 6520 not 137 was the major nuclide contributing to the dose equivalent rate. This was due to the Utirik population returning 4 months after the ini- tial contaminating event, and the Rongelap population returning after 3 years. The age of the fallout had a dramatic influence on the importance of each nuclide contributing to the internal dose equivalent. In fact 606, and 6525 played major roles during the first 3 years, a time interval that corresponded to the period during which field whole body counting facilities were being developed at Brookhaven National Laboratory and when medical examinations for people on Utirik Atoll were not done. Additionally, pooled and/or individual radiochemical analysis of urine was not performed during this period. The impact of 6520 and 60, was such that even if the least conservative dietary rate constant (K,,=0) was used for Zn, the dose equivalent rate for the average adult was in excess of Federal Radiation Council Guidelines for the first 2 years following the return to Utirik. 18