Measured Intake and Excretion Patterns of Naturally Occurring${}^{234}{\rm U},{}^{238}{\rm U}$, and Calcium in Humans

The normal dietary and fluid intake and urinary and fecal excretion of²³⁴ U and${}^{238}{\rm U}$ were determined in humans under strictly controlled conditions in the Metabolic Research Ward at Hines Hospital. These values formed the basis of the metabolic balances of these uranium isotopes. The major pathway of²³⁴ U and of${}^{238}{\rm U}$ excretion was via the intestine while the urinary²³⁴ U and${}^{238}{\rm U}$ were very low, averaging 2% of the total excretion. The uranium balances were roughly in equilibrium. These data were used in combination with measurements of tissue concentrations of uranium from nonoccupationally exposed humans to calculate steady-state uptake factors for environmental exposure to uranium isotopes during baseline conditions of a normal dietary intake.