Comparative Respiratory Effects of Ozone and Ambient Oxidant Pollution Exposure During Heavy Exercise

Fifty volunteer bicyclists were exposed to purified air containing ozone (O/sub 3/) at controlled concentrations of 0, 0.08, 0.16, 0.24, and 0.32 ppm, and to oxidant polluted ambient air (mean O/sub 3/ concentration 0.15 ppm, mean total particulate concentration 295 ..mu..g/m/sup 3/) in suburban Los Angeles. Exposures (in random order, 14 days apart) involved one hour of heavy continuous exercise (mean minute volume 57 L) plus brief warm up and cool down periods. Significant forced expiratory function decrements and symptom increases occurred in ambient air exposures. In controlled O/sub 3/ exposures, responses were significant at 0.16 ppm and higher; their severity increased with increasing O/sub 3/ concentration. Effects were only partially reversed after one hour's rest in purified air. Ambient exposures produced about the same response as O/sub 3/ alone at the same concentration. Thus coexisting pollutants do not appear to enhance the irritancy of O/sub 3/ in typical moderate ambient oxidant pollution episodes. However, O/sub 3/ itself can produce respiratory irritation at concentrations slightly above the health based federal ambient air quality standard of 0.12 ppm O/sub 3/, at high ventilation rates required during heavy exercise.