Effects of ambient ozone exposure on mail carriers' peak expiratory flow rates

The extent to which occupational exposure to ozone in ambient air can affect lung function remains unclear. We conducted a panel study in 43 mail carriers by measuring their peak expiratory flow rates (PEFRs) twice daily for 6 weeks in 2001. The daily exposure of each mail carrier to O-3, particulate matter < 10 mu m in aerodynamic diameter (PM10), and nitrogen dioxide was estimated by one air monitoring station in the center of the mail carrier's delivery area. Hourly concentrations of air pollutants during their exposure periods were 6-96 ppb for O-3, 11-249 mu g/m(3) for PM10, and 14-92 ppb for NO2. Linear mixed-effects models were used to estimate the association between air pollution exposures and PFFR after adjusting for subject's sex, age, and disease status and for temperature and humidity. We found that night PFFR and the deviation in night PEFR were significantly decreased in association with 8-hr O-3 exposures with a lag 0-2 days and by daily maximum O-3 exposures with a lag of 0-1 day in our multipollutant models. By contrast, neither PM10 nor NO2 was associated with a PEFR reduction. Daily 8-hr mean concentrations of O-3 had greater reduction effects on PFFR than did daily maximum concentrations. For a 10-ppb increase in the 8-hr average O-3 concentration, the night PEFR was decreased by 0.54% for a 0-day lag, 0.69% for a 1-day lag, and 0.52% for a 2-day lag. We found that an acute lung function reduction occurs in mail carriers exposed to O-3 concentrations below current ambient air quality standards and occupational exposure limits.