It is reasonable to assume for the very low levels of specific activity dealt with at Bikini Atoll that plant uptake will be directly proportional to soil concentration, and therefore, in turn, so will dietary rect and internal dose. This is substantiated by concentration ratios (pCi/g in plant/pCi/g in soil) developed by measuring the Cs concentration in the soil in the root zone of the sampled tree. The same concentration ratio was observed on both Bikini and Eneu is lands where soil radionuclide concentrations differ by a factor of 10 In planning for decontamination by removing top soil, the assumption is made that plant specific activity will be directly proportional to soil specific activity regardless of soil radionuclide concentration and soil condition. Although, there may be little reason to doubt this assumption when applied to one island, this report is recommending that the assumption be tested in the course of pilot excavation trials at Bikini during the next two years. 6. Body Burden The best way to determine the internal dose is by calculation from a direct measurement of the body burden. When Bikini Atoll is resettled, body burden measurements will provide the most. convincing and accurate estimates for public health control. Cesium-137 body burden measurements were made on Bikini settlers in 1974, 1977, 1978, 1979 and 1980. Unfortunately, practically no dietary information accompanied them. The average body burden of cesium-137 rose quickly in 1977-78’ to about 2.4 uCi in April of 1978 when coconut production became significant, and fell quickly to less than 10% of that value by May 1979(9) after the settlers left the atoll in August of 1978. The maximum permissible burden is 3 uCi, and some settlers had already exceeded it. , _ Theoretically, it is possible to calculate the body burden at anytime from an exact knowledge of the daily intake of cesium-137. Conversely, knowing the body burden, one can calculate the daily intake if a cesium steady-state in the body is assumed. With constant intake of !3/cs, other than for reduction due to natural radiocactive decay, a steady state is reached in about 1.5 years. If people were actually consuming less local food than assumed in the predictive model, then the predicted body burden at any time would be greater than that which is measured. This appears to be the case at Bikini Atoll in 1978 where the average adult body burden predicted BY the model was 5.5 uli and the average measured body burden was 2.4 uli This is actually a reasonable agreement because the full diet was used in the predictive model and we know the people were not on a full Tocal diet; only coconuts were available in limited supply but other terrestrial foods such as breadfruit and Pandanus were unavailable. At Rongelap and Utirik, where resettlement has been continuous since 1957 and 1954 respectively, where steady-state conditions are more likely, and where all local food products are available if the people choose £9 use them, the comparison between the model predictions and measurements of body burden are very good indeed. At Rong¢lap, using the MLSC adult diet developed by LLNL, the model predictions for !3/cs body burden were 0.19 uCi assuming S000116 D-5