MORPHOLOGICAL EFFECTS OF PROLONGED EXPOSURE TO OZONE AND SULFURIC-ACID AEROSOL ON THE RAT LUNG

Pulmonary effects of a combination of O3 (0.5 ppm) and H2SO4 aerosol (1 mg/m3) and interactive effects were determined. Groups of Sprague-Dawley rats were continuously exposed to the environmental pollutants, individually or combined, for 3, 50, 90 or 180 days. After 180 days of exposure, additional groups breathed clean air for a further 62 days. Morphological evaluation included light microscopy, autoradiography, scanning electron microscopy (SEM) and transmission electron microscopy. Quantification of pulmonary centriacinar inflammatory cell response was performed by SEM. Exposure to 0.5 ppm O3 was performed by SEM. Exposure to 0.5 ppm O3 for 180 days resulted in a persistent inflammatory response in the pulmonary centriacinar region together with a structual modification of the terminal bronchiole.sbd.proximal alveolar duct junction. H2SO4 aerosol did not induce pulmonary morphological changes or potentiaion of lesions produced by simultaneous O3 exposure. After termination of the 62-day postexposure period. O3 and O3 plus H2SO4 postexposure rats demonstrated a diminution in the intensity of pulmonary centriacinar inflammatory response and a partial restoration of normal centriacinar structure.