Epidemiologic studies have demonstrated that exposure to road traffic is associated with adverse cardiovascular outcomes. To support evidence-based policy-making and cost-effective air pollution intervention, this study aimed to identify the specific traffic-related air pollutants that are associated with the risk of coronary events.
This population-based cohort study included a 5-year exposure period (January 1994–December 1998) and a 4-year follow-up period (January 1999–December 2002). Metropolitan Vancouver residents aged 45–85 years without known coronary heart disease (CHD) at baseline (January 1999) were included in this study (N = 418 826). Individual exposures to traffic-related air pollutants including black carbon, fine particles (aerodynamic diameter, ≤2.5 μm; PM2.5), NO2, and NO were estimated at subjects' residences using land use regression models and integrating changes in residences during the 5-year exposure period. CHD hospitalizations and deaths during the 4-year follow-up period were retrieved from provincial hospitalization and death registration records.
An interquartile range increase in the 5-year average concentrations of black carbon was associated with a 4% increase in CHD hospitalizations (95% CI: 1.02–1.06) and a 6% increase in CHD mortality (95% CI: 1.02–1.09) after adjustment for age, sex, pre-existing comorbidities, neighborhood socioeconomic status, and co-pollutants (PM2.5, NO2, and NO). There were clear exposure-response relationships between black carbon and coronary events but no robust associations were found with PM2.5, NO2, or NO.
Long-term exposure to particulate black carbon was associated with increased risks of coronary morbidity and mortality, which may partly explain the observed associations between exposure to road traffic and adverse cardiovascular outcomes.