Response of young asthmatic patients to inhaled sulfuric acid.

The intent of this study was to explore the effects of inhalation of [H+] defined here as acid airborne particles at near ambient concentrations on the pulmonary function of adolescent asthmatic subjects. During rest and exercise, 22 adolescent asthmatic subjects inhaled atmospheres containing either clean air or sulfuric acid particles (H2SO4) through a mouthpiece. The concentration of hydrogen ion at the mouthpiece ([H+]) ranged from 1.18 to 3.59 mumol/m3 (51 to 176 micrograms/m3 of H2SO4). The lower range of [H+] is near the peak values measured during the summer months in the eastern United States and Canada. Pulmonary function and oral ammonia levels were measured before and after exposure in all subjects. Significant group responses to [H+] were seen in FEV1 (p = 0.016) and FVC (p = 0.039) measured 2 to 3 min post-exposure. Also, the slopes of the change in pulmonary function versus [H+] were computed for each subject. The slopes of changes in FEV1 and Vmax50 and Vmax75 versus [H+] were related to the subject's response to a standard exercise treadmill test, specifically to the subject's percentage decrease in FEV1 after exercise challenge. Pulmonary function changes 20 min postexposure did not show a significant group response to [H+] exposure; however, the relationship between percentage FEV1 decrease after exercise and the individual slopes of Vmax50 and Vmax75 persisted for at least 20 min after exposure.