Comparative measurements of the shortterm lung clearance and translocation of PuO2 and mixed Na2O + PuO2 aerosols in mice.

Mice were exposed to aerosols of either plutonium dioxide alone, or mixed oxides of plutonium and sodium with atomic ratios (Na/Pu) in the range 1.5 to 16. In the case of the mixed oxides, the lung clearance of the plutonium was represented by the sum of two exponentials, of which the short-term component accounted for 27 +/- 8% of the initial lung content with a clearance half-time of 6.0 +/- 2.7 h. These measurements were made over a period of up to 35 days after exposure, and similar measurements for a plutonium dioxide fume indicated that any early clearance phase was obscured by data variability, but was small and probably accounted for less than 10% of the initial lung deposit. The translocation of plutonium to the liver and skeleton by 1 day after exposure represented about 0.05% of the initial lung content in the case of the plutonium dioxide fume, and 7% of the initial lung content for the mixed oxide particulate where the atomic ratio was 16. The results of the animal exposures are discussed briefly with respect to the physical characterization of the particulate by electron microscopy, and in vitro filtration methods.