THE EFFECTS OF INHALED SULFURIC-ACID ON PULMONARY-FUNCTION IN ADOLESCENT ASTHMATICS

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Abstract
Ten adolescent [human] 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 100 .mu.g/m3 NaCl or 100 .mu.g/m3 H2SO4 [a transformation product of the environmental pollutant SO2] droplet aerosols. All exposures were at .apprx. 75% relative humidity and 22.degree. 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 at (.ovrhdot.Vmax75 [75% vital capacity]) (P < 0.05). Exposure to the H2SO4 aerosol produced larger reductions in .ovrhdot.Vmax75 (29%; P < 0.01) and also significant changes in 3 other parameters of pulmonary function: .ovrhdot.Vmax50, FEV1 [1-s forced expiratory volume] and total respiratory resistance (RT). Changes were similar to those reported for exposure to 0.5 ppm of SO2 in a similar group of adolescents with extrinsic asthma. This is the 1st report of reversible pulmonary functional changes after H2SO4 exposure in a group of adolescent asthmatic subjects.