The whole body retention at any time t-t of the fraction of initial radioactivity inputed at time t is E.x.eca tki Cet) vi Thus, the instantaneous activity at time t-T that remains following input during hy dt is AEP o e -(Kgta)t Bixee Et dt. It follows that the instantaneous activity at time t-T that remains following input during T is J T ° Af Pee -(Kpth )t L.x.e “i -O+Kz) (t—1) dt. The solution of the integral yields a general expression that depends on the user defining t. For example, if t is the fixed uptake interval, T, plus an additional fixed post uptake interval, @, then the body burden at T + @ is given by AP°£) Lixy Ce ~(\+Kg)T -e “4KDT) o OAtKi) g . K,~ K. As previously stated, Eq. (2) applied at Rongelap and Utirik, it was for the situation that variable time t was the uptake interval. Additionally, persons who returned to the atolls in June 1954 and June 1957 did so with an ini-~ tial body burden, q°. The behavior of this contribution to body burden, q, was embodied in the q° term of Eq. (2). A similar model was used to relate