Abstract
By use of the nontoxic-particle-challenge system, the integrated alveolar clearance was measured in rats by serially sacrificing them after exposure to TiO2 aerosol and determining the amount of TiO2 retained in the lung. Prior to exposure to TiO2, groups of animals were exposed to 0.1, 1 or 20 ppm of SO2 for 7 hours/day, 5 days/week for total exposure of 70 to 170 hours. The results indicate that SO2 affects the clearance of “inert” particles. The lowest exposures showed slight stimulation or no effect on clearance whereas a depressing of clearance was observed after 170 hours of exposure at 1 ppm. Short-term exposure at higher concentrations appear to be tolerated better than longer exposures at low concentrations.