The effects of inhaled sulfuric acid on pulmonary function in adolescent asthmatics

Ten adolescent subjects with extrinsic asthma and exercise-induced bronchospasm were studied. The subjects were exposed for 30 min at rest followed by 10 min during moderate exercise on a treadmill to either 100 micrograms/m3 sodium chloride (NaCl) or 100 micrograms/m3 sulfuric acid (H2SO4) droplet aerosols. All exposures were at approximately 75% relative humidity and 22 degrees C. Pulmonary functional measurements were recorded before, during, and after exposure while the subject was seated in a body plethysmograph. Exposure to the NaCl aerosol during exercise produced a small (12%) but significant drop in maximal expiratory flow (Vmax75) (p less than 0.05). However, exposure to the H2SO4 aerosol produced larger reductions in Vmax75 (29%; p less than 0.01) and also significant changes in 3 other parameters of pulmonary function: Vmax50, FEV1, and total respiratory resistance (RT). The changes were similar to those reported for exposure to 0.5 ppm of sulfur dioxide in a similar group of adolescents with extrinsic asthma. Our results are the first report of reversible pulmonary functional changes after H2SO4 exposure in a group of adolescent asthmatic subjects.