METHODS Body~Burden Data and Urine Activity Concentrations Adult average body-burden data and urine activity concentration data were used as input quantities to equations which related them to activity intake rates. These input data were obtained from Conard's medical reports (co56, 58, 59, 60, 62, 63, 67, 70, 75 and Wo59) and from recent surveys performed by men~ bers of the Safety and Environmental Protection Division of Brookhaven National Laboratory. The methods used to obtain the recent body-burden data were Presented by Miltenberger (Mi80). The most recent average data obtained for adult body burden at Rongelap and Utirik are presented here. These data were obtained in April 1978, August 1979 and August 1981. In the cases of 13766, 6004 and 620 direct body-burden measurements were made. In the cases of 905, and 239 py urine activity concentrations were measured and then converted to body-burden estimates. toe : . soe : This was done by relating the activity in urine to the activity in the total bedy. For 90 Sr and 239 Pu this involved use of derived quantities which are developed in the next section. Derived Quantities An equation was developed to relate the activity in the urine or whole body to the activity taken in by ingestion of contaminated food and fluids. In order to select an appropriate model for this relationship, the body-burden his~ tory and the history of activity in vegetation and soil were examined. concentrations of 137), 8, 129 Activity I, and 90. in surface soil on Rongelap and Utirik Atolls were observed to decline with time at a rate greater than radioactive decay from 1954 to the present (Ne77, Ne79, Br82). 137 Cs and 90 Activity concentrations of Sr in vegetation were observed to decline at a rate greater than that predicted by radioactive decay alone (Ne77, Ne79). Body burdens and urine