Assessing the impacts of traffic-related and woodsmoke particulate matter on subclinical measures of cardiovascular health : a HEPA filter intervention study

Fine particulate matter (PM2.5) plays an important role in the link between air pollution and a range of health effects including respiratory and cardiovascular morbidity and mortality. The specific sources of PM2.5 responsible for these effects have not been definitively identified. With traffic-related air pollution (TRAP) and woodsmoke (WS) as two of the major contributors to ambient PM2.5 concentrations, this study was the first to investigate the difference in health outcomes between these two sources. The purpose of this study was to compare cardiovascular exposure-response relationships for TRAP and WS and to evaluate the impact of HEPA filtration on indoor TRAP and WS PM₂.₅ levels. In this single-blind randomized crossover study, 83 healthy adults (54 living in high TRAP and 29 living in high WS areas) between the ages of 19 and 72 living in Metro Vancouver were recruited. Areas with high TRAP or high WS were identified using previously developed spatial models and subjects were recruited by letters sent to households in these areas. Sampling was conducted over two consecutive one-week periods, one with filtration and one with no filtration. Two filtration devices were used, one in the main living room and one in main bedroom. Endothelial function was measured at the end of each week and blood was drawn at baseline and at the end of each week. Mixed effect models were used to investigate the relationship between exposure and outcome variables. Overall, HEPA filtration was associated with a 40% decrease in indoor PM₂.₅ concentrations. There was inconclusive evidence on the potential relationship between TRAP or WS PM₂.₅ exposure and endothelial function. However, there was some suggestion of an association between PM₂.₅ exposure and CRP specifically among male participants in high-TRAP locations (20.6% increase in CRP levels per unit median increase in PM₂.₅, 95% CI, 2.62% – 41.7%). There was no association between any exposure indicators and IL-6 or BCC. In summary, the results support the hypothesis that HEPA filtration can be effective in reducing indoor PM₂.₅ concentrations with some support for the a priori hypothesis of a greater impact on markers of inflammation in areas of high TRAP.Medicine, Faculty ofPopulation and Public Health (SPPH), School ofGraduat