Exposures of human volunteers to a controlled atmospheric mixture of ozone, sulfur dioxide and sulfuric acid

Abstract

Nineteen human volunteers with normal pulmonary function and no history of asthma were exposed on two separate days to clean air and to an atmospheric mixture containing ozone (0₃), 0.37 ppm, sulfur dioxide (SO₂), 0.37 ppm, and sulfuric acid aerosol (H₂SO₄), 100 jug/m³. Subjects were exposed under carefully controlled conditions for two hours. During this period, the subjects alternately exercised for 15 minutes, at a level calculated to double minute ventilation, and rested for 15 minutes. The experimental goal was to determine whether the presence of the copollutants, H₂SO₄ and SO₂, would significantly enhance the irritant potential of ozone, or cause decrements in pulmonary function on the order of 10–20 percent. Statistical analysis of the group averaged data suggest that the mixture may have been slightly more irritating to the subjects than was O₃ alone. A large percentage of the subjects exhibited small decrements in pulmonary function. The group averaged FEV_1.0 (forced expiratory volume in one second) on the exposure day was depressed 3.7 percent from the control value. One might expect O₃ alone to depress FEV_1.0 by about 2.8 percent under similar exposure conditions.