body-burden means for adults on Utirik and the observed dietary rate constant from Rongelap. It was observed on Rongelap that .031% of 6574 was removed from = the diet pathway each day in addition to radioactive decay. Additionally, reduc~ tion in dietary radioactivity on Rongelap had been observed for 13764, 905. and 6000 to be greater than that predicted by radioactive decay alone. Instantane- ous reduction fractions very similar to those at Rongelap were observed at Utirik for the 906, and 1376, nuclides. fhe dose equivalent, dose equivalent rate, The lower curve on Figure 16 reflects and body-burden which would have occurred had radioactive decay alone accounted for the removal of 6574 from the Utirik environment. Since additional mechanisms could be measured for other nu- clides at Utirik and for the 6574 nuclide on a nearby atoll, the upper curve was chosen as the most likely body-burden history for adults post-return to Utirik Atoll. Figure 17 indicates the Utirik adult mean total body dose equivalent rate for each nuclide. An obvious difference relative to the Rongelap history exists; 6520 not 1376. was the major nuclide contributing to the dose equivalent rate. This was due to the Utirik population returning 3 to 4 months after the initial 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 internajedose equivalent. In fact 6064 and >on 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 in- dividual radiochemical analysis of urine was not performed during this period. . : 65 ) —— . . : The impact of Zn and 005 was such that even if the least conservative dietary 34