Nitric oxide (NO) in exhaled air after experimental ozone exposure in humans

We hypothesized that ozone, a common air pollutant, potent in producing air way inflammation, would increase the production of exhaled nitric oxide (NO ). If so, measurement of exhaled NO;could potentially be a valuable tool in population studies of air pollution effects. Eleven healthy non-smoking volunteers were exposed to 0.2ppm ozone (O-3) an d filtered air for 2h on two separate occasions. Exhaled NO and nasal NO we re measured before and on five occasions following the exposures. Changes i n exhaled and nasal NO after ozone exposure were adjusted for changes after air exposure. There was a slight decrease in exhaled NO (-0.6; - 3.1-1.2 ppb) (median and 95% confidence interval) and of nasal NO (- 57; - 173-75 ppb) directly aft er the ozone exposure. No significant changes in exhaled or nasal NO were h owever found 6 or 24 h after the exposure. Within the examined group, an O-3 exposure level proven to induce an airway inflammation caused no significant changes in exhaled or nasal NO levels. Hence, the current study did not yield support for exhaled NO as a useful m arker of ozone-induced oxidative stress and airway inflammation after a sin gle exposure. This contrasts with data for workers exposed to repeated high peaks of ozone. The potential for exhaled NO as a marker of oxidative stre ss therefore deserves to be further elucidated.