Synergistic interaction of ozone and respirable aerosols on rat lungs: II. Synergy between ammonium sulfate aerosol and various concentrations of ozone

Abstract

Pulmonary responses after continuous exposure of rats to concentrations of ozone (O 3) ranging from 0.12 to 0.64 ppm were quantified by measuring tissue collagen synthesis rate, tissue protein and DNA content, and various constituents of bronchoalveolar lavage fluid. After 7 days of exposure to 0.64 ppm of O 3, lung collagen synthesis rate and tissue content of protein and DNA were elevated. After shorter durations of exposure to 0.64 ppm of O 3, significant elevations were observed in the protein content and the activities of lactate dehydrogenase, acid phosphatase, and N-acetyl-β- d-glucosaminidase from lavage fluid. After exposure of rats to 0.20 ppm of O 3 for 7 days, changes could be detected in both lung collagen synthesis rate and tissue protein content. Total lavagable protein content, a sensitive indicator for O 3-induced effects upon the lung, was significantly elevated in lungs of rats exposed to 0.12 or 0.20 ppm of O 3. To examine whether a synergistic interaction occurred between 0.20 or 0.64 ppm of O 3 and acid aerosols, rats were continuously exposed to O 3 with and without concurrent exposure to 5 mg/m 3 of ammonium sulfate. A synergistic interaction between 0.20 ppm of O 3 and ammonium sulfate aerosol was observed by measurement of total lavagable protein and of lung collagen synthesis rate. These results demonstrate that ammonium sulfate aerosol interacts synergistically with O 3 at concentrations of O 3 that approach ambient levels.