Relation of peak expiratory flow rates and symptoms to ambient ozone.

The temporal association between peak expiratory flow rates (PEFRs) and ambient ozone (O3) was studied in a group of 287 children and 523 nonsmoking adults in Tucson. In children, noon PEFRs were decreased on days when there was a higher O3 concentration; children with physician-confirmed asthma experienced the greatest decrease in noon PEFR. Evening PEFR levels were also significantly related to O3 in children, especially asthmatics. Among adults, evening PEFRs were decreased in asthmatics who spent more time outdoors on days when O3 levels were higher. After we adjusted for covariates, significant effects of interactions of 8-h O3 levels with particulate matter (PM10) and temperature on daily PEFR were found. There was some overnight effect of 8-h O3 on morning PEFRs. In general, the respiratory response to low-level ambient O3 is acute, occurs more in asthmatics, and increases as temperature and PM10 increase.