The effects of on-site measured ozone concentration on pulmonary function and symptoms of asthmatics

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.