Metabolism of uranium in the rat after inhalation of two industrial forms of ore concentrate: the implications for occupational exposure

Aerosols produced from two commercially available ore concentrates in which the uranium was present essentially in the one as ammonium diuranate (ADU) and in the other as uranium octoxide (U3O8) were administered to rats. Uranium in the ADU bearing material was cleared rapidly from the lungs, the retention kinetics being similar to a class D (highly transportable) compound. Uranium in the U3O8 bearing material was removed from the lungs principally by mechanical processes, the retention kinetics being similar to a class Y (poorly transportable) compound. For both materials the distribution of uranium amongst body tissues and the fraction of the systemic content excreted in urine were similar to those obtained after the injection of soluble hexavalent compounds. For workers potentially exposed to both these materials, urine monitoring and lung radioactivity counting measurements should be used in addition to air sampling procedures for assessing the intake of uranium. Intakes of the ADU bearing material should be restricted to those permitted for short-term exposures on the basis of chemical toxicity, whereas those for the U3O8 bearing material should be governed by radiation dose. (author)