Abstract
Most studies on the effects of ambient ozone on asthmatics have been based on ozone concentration measurements taken by air monitors in downtown areas. Using a passive ozone sampler, we investigated the effects of on-site ozone concentrations on the pulmonary function and symptoms of asthmatics. Twenty moderate to severe asthmatics who had been managed for at least 2 months without changes of their medication were enrolled from 3 June to 18 July 2005. Respiratory, nasal and ocular symptoms, peak expiratory flow (PEF), which was measured twice a day, and medication use were recorded on a daily basis during the study period. Data for 17 subjects were analyzed. The average ozone exposure level was 28.2+/-23.6 ppb (3.4-315.3 ppb). There was no significant correlation between PEF and ozone concentration (p>0.05) on the same day or 1-, 2-, or 3-day lags. Interestingly, the degree of asthma symptoms was influenced by the ozone concentration (rho=0.303, p<0.001), even at concentrations less than 80 ppb (p=0.298, p<0.001), but the correlation between ozone exposure and the frequency of reliever medication use was not statistically significant (p=0.99). Our results suggest that exposure to relatively low concentrations of ozone influences the symptoms of moderate to severe asthmatics regardless of changes in pulmonary function or medication use.