We investigated the relations between ozone (O3), nitrogen dioxide (NO2), and respirable particles less than 10 μm in diameter (PM10) and school absenteeism in a cohort of 4th-grade school children who resided in 12 southern California communities. An active surveillance system ascertained the numbers and types of absences during the first 6 months of 1996. Pollutants were 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 distributed lag effects of exposure adjusted for long-term pollutant levels. Short-term change in O3, but not NO2 or PM10, was associated with a substantial increase in school absences from both upper and lower respiratory illness. An increase of 20 ppb of O3 was associated with an increase of 62.9% [95% confidence 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 O3 on illness-related absenteeism were larger in communities with lower long-term average PM10 [223.5% (95% CI = 90.4–449.7)] compared with communities with high average levels [38.1% (95% CI = 8.5–75.8)]. Increased school absenteeism from O3 exposure in children is an important adverse effect of ambient air pollution worthy of public policy consideration.
From the 1 Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA; 2National Institute of Environmental Health Sciences, Research Triangle Park, NC; and 3California Air Resources Board, Sacramento, CA.
Submitted March 31, 2000; final version accepted August 1, 2000.
Address correspondence to: Frank Gilliland, Department of Preventive Medicine, USC Keck School of Medicine, 1540 Alcazar Street, CHP 236, Los Angeles, CA 90033.
This study was supported by the California Air Resources Board (Contract A033-186); the National Institute of Environmental Health Sciences (Grants 5ES09581-01 and 5 P30 ES07048-02); the U.S. Environmental Protection Agency (Grant R826708-01-0); the National Heart, Lung, and Blood Institute (Grant 1 R01 HL61768); and the Hastings Foundation.
The statements and conclusions in this report are those of the investigators and not necessarily those of the California Air Resources Board, the Environmental Protection Agency, or the National Institute of Environmental Health Sciences. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products.