Metabolism of some industrial uranium tetrafluorides after deposition in the rat lung

Two commercially produced natural uranium tetrafluorides were administered to rats either by inhalation or direct injection into the lungs. The results: show that, for both materials uranium is cleared rapidly from the lungs, much of it to the blood, show that the distribution of uranium amongst body tissues, and the fraction of the systemic content excreted in urine, is similar to that obtained after the administration of U(VI) bicarbonate, show that the transportability of uranium is much greater than in previously reported studies with other preparations of uranium tetrafluoride, suggest that lung radioactivity counting measurements would be of limited value for interpreting human exposures, indicate that for setting exposure limits these tetrafluorides should be considered moderately transportable compounds (ICRP inhalation class W).