1. ^aSchool of Environmental Health, The University of British Columbia, Vancouver, British Columbia, Canada
2. ^bDepartment of Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA
3. ^cEnvironmental Sciences and Environmental Engineering, University of Northern British Columbia, Prince George, British Columbia, Canada
4. ^dDepartment of Health Care and Epidemiology, The University of British Columbia, Vancouver, British Columbia, Canada
5. ^eBritish Columbia Centre for Disease Control, Vancouver, British Columbia, Canada

Correspondence: Dr. M. Brauer, School of Environmental Health, The University of British Columbia, 3rd Floor, 2206 East Mall, Vancouver, British Columbia, Canada V6T 1Z3. Tel.: +604 822 9585; Fax: +604 822 9588; E-mail: brauer@interchange.ubc.ca

Received 15 June 2007; Accepted 25 October 2007; Published online 5 December 2007.

Abstract

Communities impacted by fine-particle air pollution (particles with an aerodynamic diameter less than 2.5 m; PM_2.5) from forest fires and residential wood burning require effective, evidence-based exposure-reduction strategies. Public health recommendations during smoke episodes typically include advising community members to remain indoors and the use of air cleaners, yet little information is available on the effectiveness of these measures. Our study attempted to address the following objectives: to measure indoor infiltration factor (F_inf) of PM_2.5 from forest fires/wood smoke, to determine the effectiveness of high-efficiency particulate air (HEPA) filter air cleaners in reducing indoor PM_2.5, and to analyze the home determinants of F_inf and air cleaner effectiveness (ACE). We collected indoor/outdoor 1-min PM_2.5 averages and 48-h outdoor PM_2.5 filter samples for 21 winter and 17 summer homes impacted by wood burning and forest fire smoke, respectively, during 2004–2005. A portable HEPA filter air cleaner was operated indoors with the filter removed for one of two sampling days. Particle F_inf and ACE were calculated for each home using a recursive model. We found mean F_infSD was 0.270.18 and 0.610.27 in winter (n=19) and summer (n=13), respectively, for days when HEPA filters were not used. Lower F_infSD values of 0.100.08 and 0.190.20 were found on corresponding days when HEPA filters were in place. MeanSD ACE ([F_inf without filter–F_inf with filter]/F_inf without filter) in winter and summer were 5538% and 6535%, respectively. Number of windows and season predicted F_inf (P<0.001). No significant predictors of ACE were identified. Our findings show that remaining indoors combined with use of air cleaner can effectively reduce PM_2.5 exposure during forest fires and residential wood burning.