Ozone-induced airway inflammatory changes differ between individuals and are reproducible

To study whether the individual inflammatory response to ozone was reproduc ible, dose-dependent, and time-dependent, we performed two exposures to 250 ppb ozone, one to 125 ppb and one to filtered air, each for 3 h of intermi ttent exercise and separated by at least 1 wk Twenty-one healthy and 15 ast hmatic subjects participated in the study. One hour after the two exposures to 250 ppb ozone we observed a mean increase in sputum neutrophils of 17.9 and 17.9% in healthy and of 20.3 and 15.2% in asthmatic subjects (p < 0.05 each), Twenty-four hours after exposure, the respective values were 11.9 a nd 14.8%, and 9.1 and 16.1% (p < 0.05 each). In the whole group of subjects . Individual changes in the percentage of neutrophils. were significantly c orrelated between the two exposure days 1 h (r = 0.87, p < 0.001; intraclas s correlation coefficient [Ri] = 0.86) as well as 24 h (r = 0.79, p < 0.001 ; Ri = 0.71) after exposure. The percentages of lymphocytes were increased 24 h after exposures tall subjects combined: p ( 0.05). The decrease in FEV 1 in both groups (p < 0.01), was also reproducible (r = 0.77, p < 0.001), b ut there were no correlations between changes In sputum parameters and lung function. Exposure to 125 ppb ozone caused a small increase (p < 0.05) in the percentage of neutrophils in asthmatic subjects and in the concentratio ns of interleukin-8 in both groups combined. Our data demonstrate that infl ammatory and long function responses to ozone differ between individuals an d are reproducible but not related to each other. Therefore, these response s appear to represent two independent factors underlying the airway respons e to ozone.