NONSPECIFIC BRONCHIAL RESPONSIVENESS ASSESSED IN-VITRO FOLLOWING ACUTE INHALATION EXPOSURE TO OZONE AND OZONE SULFURIC-ACID MIXTURES

Air pollution may play some role in the recent increase in severity and prevalence of asthma, but the specific chemical components with the ambient pollutant mix that may be responsible have not been delineated. Since ambient exposures involve mixtures, it is essential to examine airway responses to realistic pollutant mixtures. This study examined the ability of single (3-h) inhalation exposures to ozone and to mixtures of ozone plus sulfuric acid to induce nonspecific airway hyperresponsiveness in healthy rabbits. Airway responsiveness was assessed using an in vitro assay involving administration of increasing doses of acetylcholine to bronchial rings obtained from animals exposed to 0.1-0.6 ppm ozone or to mixtures of ozone and 50-125 mu g/m(3) sulfuric acid aerosol; results were compared to those reported previously for sulfuric acid alone. Bronchial hyperresponsiveness to ozone was noted following exposure at all concentrations, but the combination of pollutants results in antagonism. The results support the potential for ozone to induce airway hyperresponsiveness in healthy animals and suggest that interaction with sulfuric acid may reduce the effectiveness of both pollutants.