Uranium behaviour in the baboon after the deposition of a ceramic form of uranium dioxide and uranium octoxide in the lungs : implications for human exposure

U0 2 and U 3 08 were inhaled by baboons in amounts such that the mass concentrations in the lungs were between about 3 and 20, and 1 and 7.4 times respectively those calculated in human lungs after exposure to 1 ALI of the compounds. The results show that 1 year later : 1) the initial lung deposits of uranium retained in the chest are greater for U0 2 than for U 3 08 ; 2) the ratios of the amounts of uranium retained in the lymph nodes vs those in the lungs, expressed both in terms of concentration and mass, are greater for U0 2 than for U 3 08 ; 3) for both U0 2 and U 3 0 8, the amounts of uranium retained in the lymph nodes, expressed as a percentage of that in the chest, do not appear to be affected to a great extent by the initial lung deposits ; 4) after inhalation of U0 2 and U 3 08 in different amounts, the trend in the mass concentrations of uranium in the various tissues assayed were lymph nodes > lungs » skull > femora- clavicles > lumbar vertebra - thoracic cage > sternum > kidneys > liver ; 5) the measurement of urine concentrations of some enzymes may be a useful index for assessing substantial overexposures to U0 2 and U 3 0 8, however, so far, external chest monitoring and urinary assays of uranium should remain the procedures of choice.