re the number of radioactive atoms in compartment i relative to the number in all compartments on the day of return (some persons returned with body burdens), U = twenty-four hour or one liter urine activity concentration at any time post 1] : : . ~1 subject urine excretion rate, 2d, 1 fraction of element transferred from GI tract uw mm hh a return, Bq got fraction of element reaching extracellular fluid that is excreted through to blood, the urine pathway, k 2 instantaneous fraction of atoms removed from the atom ingestion rate per unit time, at, due to factors other than radioactive decay, q = body burden at any time post return, Bq, q = body burden on the day of return, Bq. Using adult average data, two consecutive urine or body-burden measure- ments were used to estimate the unknown value of k, a rate constant describing removal of radioactivity in diet items. This yielded n-l estimates of k where mwas the number of measured adult average data points for body burden or urine activity concentration during the residence interval. An average value of k was assigned for the entire residence interval during which activity was measured. After the average k was obtained, an estimate of the atom ingestion rate on day of return was calculated based on a value for adult average body burden or urine activity concentration and the time since day of return. This generated n values of the atom ingestion rate on day of return where n was again the number of adult average data points for body burden or urine activity concentration.