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Respiratory Symptoms Following Wildfire Smoke Exposure: Airway Size as a Susceptibility Factor

Mirabelli, Maria C.a,b,c; Künzli, Ninoa,b,d; Avol, Edwarde; Gilliland, Frank D.e; Gauderman, W Jamese; McConnell, Robe; Peters, John M.e

doi: 10.1097/EDE.0b013e31819d128d
Air Pollution: Original Article

Background: Associations between exposure to smoke during wildfire events and respiratory symptoms are well documented, but the role of airway size remains unclear. We conducted this analysis to assess whether small airway size modifies these relationships.

Methods: We analyzed data from 465 nonasthmatic 16- to 19-year-old participants in the Children's Health Study. Following an outbreak of wildfires in 2003, each student completed a questionnaire about smoke exposure, dry and wet cough, wheezing, and eye symptoms. We used log-binomial regression to evaluate associations between smoke exposure and fire-related health symptoms, and to assess modification of the associations by airway size. As a marker of airway size, we used the ratio of maximum midexpiratory flow to forced vital capacity.

Results: Forty percent (186 of 465) of this population (including students from 11 of 12 surveyed communities) reported the odor of wildfire smoke at home. We observed increased respiratory and eye symptoms with increasing frequency of wildfire smoke exposure. Associations between smoke exposure and having any of 4 respiratory symptoms were stronger in the lowest quartile of the lung function ratio (eg, fire smoke 6+ days: prevalence ratio: 3.8; 95% confidence interval (CI = 2.0–7.2), compared with the remaining quartiles (fire smoke 6+ days: prevalence ratio = 2.0; 1.2–3.2). Analysis of individual symptoms suggests that this interaction may be strongest for effects on wheezing.

Conclusions: Small airways may serve as a marker of susceptibility to effects of wildfire smoke. Future studies should investigate the role of airway size for more common exposures and should include persons with asthma.

From the aCentre for Research in Environmental Epidemiology, Barcelona, Spain; bMunicipal Institute of Medical Research (IMIM-Hospital del Mar), Barcelona, Spain; cCIBER Epidemiología y Salud Pública, Spain; dInstitució Catalana de Recerca i Estudis Avançats, Barcelona, Spain; and eDepartment of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California.

Submitted 20 April 2008; accepted 13 August 2008; posted 9 March 2009.

Supported by the California Air Resources Board (A033-186), the US National Institutes of Health (NIH) (1P01ES009581, 5P30ES007048, 1R01HL061768), the US Environmental Protection Agency (R826708, R831845) and the Hastings Foundation. Maria Mirabelli received funding from the National Institute of Environmental Health Sciences, NIH (1F32ES014142).

The contents of this manuscript are solely the responsibility of the authors and do not necessarily represent the official views of the funding agencies.

Correspondence: Maria C. Mirabelli, Centre for Research in Environmental Epidemiology, Barcelona Biomedical Research Park, c/Dr. Aiguader, 88, 08003 Barcelona, Spain. E-mail:

© 2009 Lippincott Williams & Wilkins, Inc.