| Pulmonary Effects of Indoor- and Outdoor-Generated Particles in Children with Asthma Jane Q. Koenig,1 Therese F. Mar,1 Ryan W. Allen,1 Karen Jansen,1 Thomas Lumley,2 Jeffrey H. Sullivan,1 Carol A. Trenga,1 Timothy V. Larson,3 and L.-Jane S. Liu1 1Department of Environmental Health and Occupational Sciences, 2Department of Biostatistics, and 3Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA Abstract
Most particulate matter (PM) health effects studies use outdoor (ambient) PM as a surrogate for personal exposure. However, people spend most of their time indoors exposed to a combination of indoor-generated particles and ambient particles that have infiltrated. Thus, it is important to investigate the differential health effects of indoor- and ambient-generated particles. We combined our recently adapted recursive model and a predictive model for estimating infiltration efficiency to separate personal exposure (E) to PM2.5 (PM with aerodynamic diameter ≤ 2.5 µm) into its indoor-generated (Eig) and ambient-generated (Eag) components for 19 children with asthma. We then compared Eig and Eag to changes in exhaled nitric oxide (eNO) , a marker of airway inflammation. Based on the recursive model with a sample size of eight children, Eag was marginally associated with increases in eNO [5.6 ppb per 10-µg/m3 increase in PM2.5 ; 95% confidence interval (CI) , -0.6 to 11.9 ; p = 0.08]. Eig was not associated with eNO (-0.19 ppb change per 10 µg/m3) . Our predictive model allowed us to estimate Eag and Eig for all 19 children. For those combined estimates, only Eag was significantly associated with an increase in eNO (Eag: 5.0 ppb per 10-µg/m3 increase in PM2.5 ; 95% CI, 0.3 to 9.7 ; p = 0.04 ; Eig: 3.3 ppb per 10-µg/m3 increase in PM2.5 ; 95% CI, -1.1 to 7.7 ; p = 0.15) . Effects were seen only in children who were not using corticosteroid therapy. We conclude that the ambient-generated component of PM2.5 exposure is consistently associated with increases in eNO and the indoor-generated component is less strongly associated with eNO. Key words: ambient air pollution, asthma, exhaled nitric oxide, infiltration, PM2.5. Environ Health Perspect 113:499-503 (2005) . doi:10.1289/ehp.7511 available via http://dx.doi.org/ [Online 10 January 2005]
Address correspondence to J.Q. Koenig, Department of Environmental Health, Box 357234, Room F561A, 1705 NE Pacific, University of Washington, Seattle, WA 98195 USA. Telephone: (206) 543-2026. Fax: (206) 685-3990. E-mail: Jkoenig@u.washington.edu We thank L. Tuttle, T. Gould, M. Drudge, and the field/lab technicians who worked on this project. We owe a great deal to our study subjects. This work was funded by the U.S. Environmental Protection Agency (EPA ; CR82717701) , the Northwest Research Center for Particulate Air Pollution and Health (U.S. EPA grant CR827355) , and National Institute of Environmental Health Sciences grant P30 ES07033. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use. The authors declare they have no competing financial interests. Received 18 August 2004 ; accepted 10 January 2005.
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