Comparison of the late excretion of 226Ra and 239Pu by man

Excretion rates of 226Ra (12 cases) and 239Pu (2 cases) at roughly 103 and 104 days after intake are reviewed and compared with each other and with the predictions of various models. There are more differences than similarities between the behavior of Ra and that of Pu, but the excretion rates at 103 days are similar when expressed as percent of initial dose, as are the coefficients of elimination at 104 days. At the late times, about 1.5 percent of the body's content of either element is excreted annually. Between individuals there is enormous variability in the late excretion of Ra, which may also be present in Pu cases. The role (if any) of osteoporosis needs to be clarified