Repeated ozone exposures enhance bronchial allergen responses in subjects with rhinitis or asthma

Background Single exposures to > 200 p.p.b. of ozone are capable of enhancing the early-phase lung function response to allergen. Objective The aim of the present study was to compare the effect of single vs. repeated exposures to ozone on early and late-phase allergen responses. Methods Eleven subjects with allergic asthma and 22 subjects with allergic rhinitis underwent single exposures to filtered air, 125 p.p.b. and 250 p.p.b. ozone, as well as repeated exposures to 125 p.p.b. ozone on four consecutive days. Twenty hours after the (final) exposure, subjects inhaled a single dose of allergen and a sputum induction was performed 6-7 h later. Results In the subjects with rhinitis, the mean early-phase response of FEV1 and the number of greater than or equal to 20% reductions were significantly greater after exposure to 250 or 4 x 125 p.p.b. ozone compared with filtered air. In addition, most of the greater than or equal to 15% late-phase responses in FEV1 occurred after exposure to 4 x 125 p.p.b., as well as the strongest effects on sputum parameters. The rise in the number of eosinophils was statistically significant in both groups. Regarding the number of lymphocytes and the concentrations of mast cell tryptase, histamine or LDH, significance was, however, only reached in the asthma group. Conclusion Our data suggest that repeated exposure to ozone, at a peak ambient air level, can enhance both functional and inflammatory responses to inhaled allergen in subjects with pre-existing allergic airway diseases, and that these effects might reach a clinically relevant magnitude.