Ronge Lap were observed at Utirik tor the 90Sr and 137Cs nuclides. curve on Fiyure L6 reflects the dose equivalent, The lower dose equivalent rate and body burden which would have occurred had radioactive decay alone accounted for the removal of 675 from the Utirik environment. Since additional mechanisms could be measured for other nuclides at Utirik and for the 652 nuclide on a nearby atoll, the upper cur ‘e was chosen as the most likely body burden history for adults post return tv 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, 6500 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 604 and 6570 played major roles during the first 3 years, a time incerval 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 6570 and 600, was such that even if the least conservative dietary rate constant (K_=0) was used for Zn, the dose equivalent rate for the average E adult was in excess of Federal Radiation Council Guidelines for the First 2 years following the return to Utirik. 18