Pulmonary Function Responses of Young and Older Adults to Mixtures of O 3,NO 2 and Pan

The pulmonary function of 32 nonsmokers (eight men and eight women, 18–26 years of age; eight men and eight women, 51–76 years of age) was measured before and after two-hour exposures to (1) filtered air (FA), (2) 0.45 ppm ozone (O₃), (3) 0.13 ppm peroxyacetyl nitrate + 0.45 ppm O₃ (PAN/O₃), (4) 0.60 ppm nitrogen dioxide + 0.45 ppm Os (NO₂/O₃), and (5) 0.13 ppm PAN + 0.60 ppm NO₂ + 0.45 ppm O₃ (PAN/NO₂/O₃). Subjects alternated 20-minute periods of rest and exercise (ventilation = 25 L/min). Forced vital capacity (FVC) was measured pre-exposure and five-minutes after each exercise period. Forced expiratory volume in one sec (FEV_1.0) and forced expiratory flow between 25 and 75 percent of FVC (FEF25–75%) were calculated from the FVC tests. Data were analyzed by 4-factor analysis of variance (sex, age, time period, exposure). The responses of men and women were similar. FA exposure induced no effects. The young subjects' decrements in FVC, FEV₁₀ and FEF25–75% became significant (P < 0.01) after the second exercise period of the O₃, NO₂/O₃ and PAN/NO₂/O₃ exposures, while the PAN/O₃ decrements were significant (P < 0.01) after the first exercise period. Although PAN/O₃ induced significant decrements earlier than the other conditions including O₃, the mean pre- to post-exposure decrements for the four conditions including O₃ were similar. In contrast, the older subjects had smaller and fewer significant decrements in pulmonary functions. They had significant mean decrements in FVC following the third exercise period of the NO₂/O₃ and PAN/NO₂/O₃ exposures, in FEV_1.0 after the third exercise period of the PAN/O₃ and NO₂/O₃ exposures, and in FEF25–75% beginning after the second exercise period of the NO₂/O₃ exposure. The results suggest that older men and women are less responsive to O₃ and mixtures of O₃, NO₂ and PAN than young men and women, and that O₃ is responsible for the decrements observed in pulmonary function.