Ronge lap were observed at Utirik jor the 90Sr and 137Cs nuclides. The lower curve on Figure 16 reflects the dose equivalent, dose equivalent rate and body burden which would have occurred had radioactive decay alone accounted for the removal o! 65 . . Zn from the Utirik environment. be measured for othe: . a . Since additional mechanisms nuclides at Utirik and for the could 65 Zn nuclide on a nearby atoll, th: 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, boon 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 fallouc had a dramatic influence on the importance of each nu- clide contributing to the internal dose equivalent. In fact Co 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 ee and 60,4 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