The effects of ambient air pollution on school absenteeism due to respiratory illnesses

We investigated the relations between ozone (O-3), nitrogen dioxide (NO2), and respirable particles less than 10 mum in diameter (PM10) and school abs enteeism in a cohort of 4th-grade school children who resided in 12 souther n California communities. An active surveillance system ascertained the num bers and types of absences during the first 6 months of 1996. Pollutants we re measured hourly at central-site monitors in each of the 12 communities. To examine acute effects of air pollution on absence rates, we fitted a two -stage time series model to the absence count data that included distribute d lag effects of exposure adjusted for long-term pollutant levels. Short-te rm change in O-3, but not NO2 or PM10, was associated with a substantial in crease in school absences from both upper and lower respiratory illness. An increase of 20 ppb of O-3 was associated with an increase of 62.9% [95% co nfidence interval (95% CI) = 18.4-124.1%] for illness-related absence rates , 82.9% (95% CI = 3.9-222.0%) for respiratory illnesses, 45.1% (95% CI = 21 .3-73.7%) for upper respiratory illnesses, and 173.9% (95% CI = 91.3-292.3% ) for lower respiratory illnesses with wet cough. The short-term effects of a 20-ppb change of O-3 on illness-related absenteeism were larger in commu nities with lower long-term average PM10 [223.5% (95% CI = 90.4-449.7)] com pared with communities with high average levels [38.1% (95% CI = 8.5-75.8)] . Increased school absenteeism from O-3 exposure in children is an importan t adverse effect of ambient air pollution worthy of public policy considera tion.