Ambient nitrogen dioxide concentrations increase bronchial responsiveness in subjects with mild asthma

Abstract

Twenty subjects with mild asthma were exposed at rest in a body plethysmography, to NO2 at 0, 260, 510 and 1,000 μg·m3, for 30 min on four separate days. Bronchial responsiveness (histamine inhalation test) was measured after each exposure session. Airway resistance (Raw), thoracic gas volume (TGV) and specific airway resistance (sRaw) were measured before, during and after exposure, and the breathing pattern was monitored during the whole session. Bronchial responsiveness increased significantly after 30 min exposure to 510 μg·m3 NO2 (p < 0.01). There were also tendencies to an increased bronchial responsiveness after exposure to 260 and 1,000 μm·m3 NO2, but these changes were not statistically significant. Effects on airway resistance and breathing pattern were not demonstrated by exposure to 0-1,000 μg·m3 NO2. We conclude that short-term NO2 exposure at about 500 μgμ3 slightly affects human bronchial responsiveness in subjects with mild asthma.