The distribution and clearance of inhaled UO2 particles on the first bifurcation and trachea of rats.

The distribution of inhaled UO2 particles is described in the upper respiratory tract of rats up to 14 d after inhalation. Delayed neutron analysis was used to determine accurately nanogram quantities of UO2 present in excised tissues. The mass of UO2 in the extrapulmonary bronchi and first bifurcation decreased more slowly over 0--8 d after inhalation than the corresponding mass on the trachea. Between 8 and 14 d neither amount altered significantly. Small but significant quantities of UO2 deposited on the trachea during inhalation, remained until at least 14 d after inhalation.