Health effects of indoor air pollution: Synergistic effects of nitrogen dioxide and a respirable aerosol

Comparative studies of the effects of various air pollutants on lung collagen biosynthesis have been performed. A hitherto unexpected synergism between the oxidant air pollutants ozone or nitrogen dioxide and a respirable-sized aerosol of ammonium sulfate was observed during controlled exposures of rats to these substances. In an assay system, measuring collagen biosynthesis by lung minces prepared from rats exposed for 1 week to either filtered air or to these pollutants gases, dose-response curves to either O₃ or NO₂ are altered in the presence of 5 mg/m³ of (NH₄)₂SO₄ aerosol. These observations may have broad implications for the appropriate evaluation of laboratory data in the setting of ambient air quality standards and/or the setting of threshold limit values for maintenance of occupational health and safety.