Pathobiochemical effects in rat lung related to episodic ozone exposure

Abstract Correlation of ozone aerometrics with data from health effect studies on ozone suggests that the present ozone standard is inadequate to protect public health. To develop ozone exposure-effect relationships, the present study was performed to determine the effects of ozone in rats following prolonged, episodic exposure. Acute pulmonary injury and inflammation, as assessed by lung lavage protein increase and neutrophil influx, following 3 consecutive, 12 h nocturnal exposures to 0.4 ppm appeared to be primarily induced by the first exposure and showed full reversibility in spite of continuance of exposure. Biochemical indices for cell proliferation and lung tissue repair, however, showed continual increases during consecutive exposures. Assessment of characteristic cell functions in isolated Clara cells and in alveolar macrophages and type II cells following continuous ozone exposure to 0.8 ppm (7 days) or 0.75 ppm (4 days), respectively, revealed that lung cell proliferation coincides with cellular biochemical changes which might be looked upon as potentially adverse. Collectively, these data call upon health risk evaluations of episodic ozone effects and reinforce the need for extension of the data base in this respect.