The spatial and temporal distribution of inhaled UO2 particles in the respiratory tract of the rat. II. The relative concentration of UO2 between the intrapulmonary airways and the pulmonary tissue.

In this experiment the relative masses of UO2 particles per unit mass of tissue are determined between intrapulmonary airways and pulmonary tissue in rat lungs. A mean value of 0.57 +/- 0.06 (SE) was determined in tissue sections taken at 3-mm or 5-mm intervals throughout the lobes of animals killed from 2 to 35 days after inhalation. The experimental results are compared with data derived from the ICRP Lung Model for man and indicate that in the rate approximately 4% of the lung burden as opposed to about 0.02% derived for man is associated with the intrapulmonary airways. The 4% figure, if also applicable to man, would have extremely important implications in radiological protection, since the basal cells of the bronchial epithelium are thought to be sensitive to the induction of bronchogenic carcinoma.