Effect of Nitrogen Dioxide on Pulmonary Bacterial Defense Mechanisms

Abstract

Effect of nitrogen dioxide on antibacterial activity in vivo was investigated by simultaneously determining physical removal and bactericidal activity rates of murine lung. Mice were exposed to various concentrations of nitrogen dioxide for 17 hours prior to or 4 hours after infection with aerosols of Staphylococcus aureus labeled with radioactive phosphorus (³²P). Animals infected and then exposed to levels of nitrogen dioxide above 7.0 ppm showed a progressive decrease in percent pulmonary bactericidal activity which could not be accounted for by physical removal of bacteria. Exposure to levels of nitrogen dioxide of 2.3 ppm or greater for 17 hours prior to staphylococcal infection caused decreases in bactericidal activity. The finding that murine resistance to infection is diminished at exposure levels only slightly above ambient (2.3 ppm) suggests that human populations may incur a similar risk.