Biomass Burning as a Source of Ambient Fine Particulate Air Pollution and Acute Myocardial Infarction

BACKGROUND: Biomass burning is an important source of ambient fine particulate air pollution (PM(2.5)) in many regions of the world. METHODS: We conducted a time-stratified case-crossover study of ambient PM(2.5) and hospital admissions for myocardial infarction (MI) in three regions of British Columbia, Canada. Daily hospital admission data were collected between 2008 and 2015 and PM(2.5) data were collected from fixed site monitors. We used conditional logistic regression models to estimate odds ratios (ORs) describing the association between PM(2.5) and the risk of hospital admission for MI. We used stratified analyses to evaluate effect modification by biomass burning as a source of ambient PM(2.5) using the ratio of levoglucosan/PM(2.5) mass concentrations. RESULTS: Each 5 µg/m(3) increase in 3-day mean PM(2.5) was associated with an increased risk of MI among elderly subjects (≥65 years; OR = 1.06, 95% CI: 1.03, 1.08); risk was not increased among younger subjects. Among the elderly, the strongest association occurred during colder periods (<6.44°C); when we stratified analyses by tertiles of monthly mean biomass contributions to PM(2.5) during cold periods, ORs of 1.19 (95% CI: 1.04, 1.36), 1.08 (95% CI: 1.06, 1.09), and 1.04 (95% CI: 1.03, 1.06) were observed in the upper, middle, and lower tertiles (P(trend) = 0.003), respectively. CONCLUSION: Short-term changes in ambient PM(2.5) were associated with an increased risk of MI among elderly subjects. During cold periods, increased biomass burning contributions to PM(2.5) may modify its association with MI.