Exposure to Ambient Ultrafine Particles and Nitrogen Dioxide and Incident Acute Myocardial Infarction and Congestive Heart Failure: A Population-Based Cohort Study

Abstract

Background. Although long-term exposure to traffic-related air pollutants such as nitrogen dioxide (NO2) has been linked to cardiovascular mortality and morbidity, little is known about the effect of ultrafine particles (≤0.1um in diameter; UFPs) on the incidence of major cardiovascular events. We conducted a population-based cohort study to assess the associations of chronic exposure to UFPs and NO2 with the incidence of acute myocardial infarction (AMI) and congestive heart failure (CHF). Methods. We used the Ontario Population Health and Environment Cohort (ONPHEC) to assemble our study cohorts which comprised all long-term Ontario residents who were aged 30 to 100 years and free of respective study outcomes, and lived in the City of Toronto, Canada on January 1st, 1996. Subjects were followed until December 31st, 2012. Outcomes were ascertained using validated province-wide databases. We estimated annual concentrations of UFPs and NO2 using land-use regression models and assigned these estimates to participants’ annual postal-code addresses during the follow-up period. Using random-effects Cox proportional hazards models, we calculated hazard ratios (HRs) and 95% confidence intervals (CIs) for UFPs and NO2, adjusted for individual- and neighborhood-level covariates. We considered both single- and multi-pollutant models. Results. Between 1996 and 2012, we identified 106,644 and 43,745 incident cases of AMI and CHF, respectively. Each interquartile change in exposure to UFPs (~10,000 count/cm3) was associated with increased risk of incident AMI (HR=1.05; 1.02-1.07) and CHF (HR=1.03; 1.02-1.05) after adjusting for all covariates. These results remained unaltered with further control for fine particulate matter (PM2.5) and NO2. Exposure to NO2 was also independently associated with higher incidence of CHF.Conclusion. Exposure to traffic-related air pollution including UFPs and NO2 may increase the risk of incident cardiovascular events.