Effects of Ambient Ozone on Respiratory Function in Healthy Adults Exercising Outdoors

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Abstract
The effect of exposure to ozone (O3) in ambient air on respiratory function was studied in 30 healthy nonsmokers engaged in a regular daily program of outdoor exercise in Tuxedo. NY [USA] during the summer of 1985. Each subject did the same exercise each day, but exercise intensity and duration varied widely between subjects, with minute ventilation ranging from 20 to 153 L and duration ranging from 15 to 55 min. Spirometry was performed immediately before and after each exercise period. O3 concentrations during exercise ranged from 21 to 124 parts per billion (ppb). All measured functional indexes showed significant (p < 0.001). O3-associated mean decrements with FVC at -2.1 ml/ppb, FEV1 at -1.4 ml/ppb, PEFR at -9.2 ml/s/ppb, FEF25-75 at -6.0 ml/s/ppb, and FEV1/FVC at -0.038%/ppb. Mean decrements were smaller for 10 subjects with minute ventilations > 100 L than for 10 other subjects with minute ventilations between 60 and 100 L or for the 10 subjects with minute ventilations below 60 L. Overall, the functional decrements were similar in magnitude to those we have seen in children engaged in supervised recreational programs in summer cramps. For 10 subjects with minute ventilations comparable to those used in controlled 1- and 2-h exposures to O3 in purified air in chambers (50 to 80 L), the effects were about twice as large as those reported for the chamber studies. We conclude that ambient cofactors can potentiate the responses to O2 and the results of the studies in chambers may substantially underestimate the O3-associated responses that can occur among populations engaged in normal outdoor recreational activity.