Associations of Long-Term Exposure to Ultrafine Particles and Nitrogen Dioxide with Increased Incidence of Congestive Heart Failure and Acute Myocardial Infarction

Abstract

Although long-term exposure to traffic-related air pollutants such as nitrogen dioxide (NO₂) has been linked to cardiovascular mortality, little is known about the association of ultrafine particles (UFPs) with incidence of major cardiovascular events. We conducted a population-based cohort study to assess the associations of chronic exposure to UFPs and NO₂ with incident congestive heart failure (CHF) and acute myocardial infarction. Our study population comprised all long-term Canadian residents aged 30-100 years who lived in Toronto, Canada, 1996-2012. We estimated annual concentrations of UFPs and NO₂ using land-use regression models and assigned these estimates to participants' postal-code addresses in each year during the follow-up period. We estimated hazard ratios (HRs) for UFPs and NO₂ using random-effects Cox proportional hazards models. We controlled for smoking and obesity using an indirect adjustment method. Our cohorts comprised ~1.1 million individuals at baseline. In single-pollutant models, each interquartile increase in UFPs exposure was associated with increased incidence for CHF (HR_iqr: 1.03; 95%CI: 1.02, 1.05) and acute myocardial infarction (HR_iqr: 1.05; 95%CI: 1.02, 1.07), respectively. Adjustment for fine particles and NO₂ did not materially change these estimated associations. Exposure to NO₂ was also independently associated with higher CHF incidence (HR_iqr: 1.04; 95%CI: 1.03, 1.06).