THE EFFECT OF OZONE EXPOSURE ON ALLERGEN RESPONSIVENESS IN SUBJECTS WITH ASTHMA OR RHINITIS

The aim of th is study was to determine whether ozone enhances bronchi al responsiveness to allergens in subjects with allergic asthma, or fa cilitates a bronchial response in subjects with allergic rhinitis. Twe nty-four subjects with mild stable allergic asthma, 12 subjects with a llergic rhinitis without asthma, and 10 healthy subjects participated in the study. Subjects breathed 250 ppb ozone or filtered air (FA) for 3 h of intermittent exercise. Airway responsiveness to methacholine w as determined 1 h before and after exposures, and allergen responsiven ess 3 h after exposures. We determined the concentration of methacholi ne (PC(20)FEV(1)) and the dose of allergen (PD(20)FEV(1)) producing a 20% fall in FEV(1). In the subjects with asthma, FEV(1) decreased by 1 2.5 +/- 2.2% (mean +/- SEM; p = 0.0001), PC(20)FEV(1) of methacholine by 0.91 +/- 0.19 doubling concentrations (p = 0.0001) and PD(20)FEV(1) of allergen by 1.74 +/- 0.25 doubling doses (p < 0.0001) after ozone compared with FA. The changes in lung function, methacholine, and alle rgen responsiveness did not correlate with each other. In the subjects with rhinitis, mean FEV(1) decreased by 7.8% and 1.3% when ozone or F A, respectively, were followed by allergen inhalation (p = 0.035). The refore, our data suggest that short-term exposure to ozone can increas e bronchial allergen responsiveness in subjects with mild allergic ast hma or rhinitis.