Lung function and inflammation in healthy young adults after 6.6 hours of 0.07 ppm ozone exposure

Controlled human exposure studies have provided strong evidence of decremental effects of ozone exposure in healthy adults. However, there have been few controlled exposure studies conducted at the level of the National Ambient Air Quality Standard (NAAQS). In this study, 38 healthy adults (19-34 yr) were exposed to clean air (CA) and 0.07 ppm ozone for 6.6 h with intermittent moderate exercise. Exposures were randomized and double-blind. Pulmonary function was measured immediately before and after exposure to CA and 0.07 ppm ozone. The percent polymorphonuclear neutrophils (%PMNs) in sputum were quantified in 14 participants approximately 16-18 h post-exposure. Respiratory and non-respiratory symptoms were assessed before and after each exposure, and at each 10-min break during exposure sessions. We report mean (±SEM) decrements in FEV₁ immediately after exposure to 0.07 ppm ozone relative to CA (-1.24 ± 0.92% vs. 0.83 ± 0.50%; p = 0.017). Additionally, the mean decrement in FVC was greater after ozone relative to CA (-1.22 ± 0.29% vs. -0.44 ± 0.40%; p = 0.148). The mean (±SEM) %PMNs in sputum was greater after ozone relative to CA (33.4 ± 6.9% vs.18.6 ± 5.6%; p = 0.013) and respiratory symptoms were significantly elevated during hours 5.6 and 6.6 of the ozone exposure, relative to CA. In summary, this study demonstrates a loss of pulmonary function and an inflammatory response among healthy subjects exposed to ozone at the current NAAQS level of 0.07 ppm.