- Full (HTML) - Full (PDF) - Related EHP Articles - PubMed:Related Articles - PubMed:Citation - Cited in PMC - Purchase This Issue

Onchee Yu,¹ Lianne Sheppard,^1,2 Thomas Lumley,¹ Jane Q. Koenig,² and Gail G. Shapiro³

¹Department of Biostatistics, ²Department of Environmental Health, and ³Department of Pediatrics, University of Washington, Seattle, Washington, USA

Abstract

We observed a panel of 133 children (5-13 years of age) with asthma residing in the greater Seattle, Washington, area for an average of 58 days (range 28-112 days) during screening for enrollment in the Childhood Asthma Management Program (CAMP) study. Daily self-reports of asthma symptoms were obtained from study diaries and compared with ambient air pollution levels in marginal repeated measures logistic regression models. We defined days with asthma symptoms as any day a child reported at least one mild asthma episode. All analyses were controlled for subject-specific variables [age, race, sex, baseline height, and FEV₁ PC₂₀ concentration (methacholine provocative concentration required to produce a 20% decrease in forced expiratory volume in 1 sec) ] and potential time-dependent confounders (day of week, season, and temperature) . Because of variable observation periods for participants, we estimated both between- and within-subject air pollutant effects. Our primary interest was in the within-subject effects: the effect of air pollutant excursions from typical levels in each child's observation period on the odds of asthma symptoms. In single-pollutant models, the population average estimates indicated a 30% [95% confidence interval (CI) , 11-52%] increase for a 1-ppm increment in carbon monoxide lagged 1 day, an 18% (95% CI, 5-33%) increase for a 10-µg/m³ increment in same-day particulate matter < 1.0 µm (PM_1.0) , and an 11% (95% CI, 3-20%) increase for a 10-µg/m³ increment in particulate matter < 10 µm (PM₁₀) lagged 1 day. Conditional on the previous day's asthma symptoms, we estimated 25% (95% CI, 10-42%) , 14% (95% CI, 4-26%) , and 10% (95% CI, 3-16%) increases in the odds of asthma symptoms associated with increases in CO, PM_1.0, and PM₁₀, respectively. We did not find any association between sulfur dioxide (SO₂) and the odds of asthma symptoms. In multipollutant models, the separate pollutant effects were smaller. The overall effect of an increase in both CO and PM_1.0 was a 31% (95% CI, 11-55%) increase in the odds of symptoms of asthma. We conclude that there is an association between change in short-term air pollution levels, as indexed by PM and CO, and the occurrence of asthma symptoms among children in Seattle. Although PM effects on asthma have been found in other studies, it is likely that CO is a marker for vehicle exhaust and other combustion by-products that aggravate asthma. Key words: ambient air pollution, asthma, carbon monoxide, children, panel study, particulate matter, sulfur dioxide, symptoms, within-subject effects. Environ Health Perspect 108:1209-1214 (2000) . [Online 20 November 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p1209-1214yu/ abstract.html

Address correspondence to L. Sheppard, Department of Biostatistics, Box 357232, University of Washington, Seattle, WA 98195-7232 USA. Telephone: (206) 616-2722. Fax: (206) 616-2724. E-mail: sheppard@biostat.washington.edu

This research was affiliated with the Childhood Asthma Management Program, funded by the National Heart, Lung, and Blood Institute (N01 HR 16050) . It was supported in part by the U.S. Environmental Protections Agency Northwest Center for Particulate Matter and Health at the University of Washington.

Received 16 March 2000 ; accepted 24 July 2000.