Airborne Nanoparticle Concentrations Are Associated with Increased Mortality Risk in Canada’s Two Largest Cities
Marshall Lloyd, Toyib Olaniyan, Arman Ganji, Junshi Xu, Alessya Venuta, Leora Simon, Mingqian Zhang, Milad Saeedi, Shoma Yamanouchi, An Wang, Alexandra M. Schmidt, Hong Chen, Paul J. Villeneuve, Joshua S. Apte, Éric Lavigne, Richard T. Burnett, Michael Tjepkema, Marianne Hatzopoulou, Scott Weichenthal
Abstract
Abstract Rationale Outdoor fine particulate air pollution (particulate matter with an aerodynamic diameter ⩽2.5 μm; PM2.5) contributes to millions of deaths around the world each year, but much less is known about the long-term health impacts of other particulate air pollutants, including ultrafine particles (a.k.a. nanoparticles), which are in the nanometer-size range (<100 nm), widespread in urban environments, and not currently regulated. Objectives We sought to estimate the associations between long-term exposure to outdoor ultrafine particles and mortality. Methods Outdoor air pollution levels were linked to the residential addresses of a large, population-based cohort from 2001 to 2016. Associations between long-term exposure to outdoor ultrafine particles and nonaccidental and cause-specific mortality were estimated using Cox proportional hazards models. Measurements and Main Results An increase in long-term exposure to outdoor ultrafine particles was associated with an increased risk of nonaccidental mortality (hazard ratio = 1.073; 95% confidence interval = 1.061–1.085) and cause-specific mortality, the strongest of which was respiratory mortality (hazard ratio = 1.174; 95% confidence interval = 1.130–1.220). We estimated the mortality burden for outdoor ultrafine particles in Montreal and Toronto, Canada, to be approximately 1,100 additional nonaccidental deaths every year. Furthermore, we observed possible confounding by particle size, which suggests that previous studies may have underestimated or missed important health risks associated with ultrafine particles. Conclusions As outdoor ultrafine particles are not currently regulated, there is great potential for future regulatory interventions to improve population health by targeting these common outdoor air pollutants.