Mortality Attributable to Ambient Fine Particulate Matter Exposure in a Changing Canadian Population, 2001 to 2021

We aim to understand how changes in ambient fine particulate matter (PM2.5) over the last two decades have influenced PM2.5-attributable mortality in a Canadian population experiencing both growth and changing baseline health status. We conducted a health impact analysis using dynamic estimates of population, baseline mortality rates, and satellite-based PM2.5 concentrations to estimate mortality attributable to long-term PM2.5 exposure every five years between 2001 and 2021, applying risk estimates from the 2006 Canadian Census Health and Environment Cohort (CanCHEC) to the population aged 25 and older. We conducted a decomposition analysis to examine the influences of population exposure, size, and health status on trends in PM2.5-attributable mortality. Between 2001 and 2021, population-weighted exposure to PM2.5 declined by 18% in Canada, with improvements occurring in most urban areas. In recent years, these changes have led to 4,400 (95% CI: 3,700–5,000) to 4,700 (95% CI: 4,100–5,400) fewer PM2.5-attributable deaths annually based on log–linear and log–log shapes of concentration–response. However, a growing population alongside higher baseline mortality risks in several regions, likely due to aging, has led to a small net increase in total PM2.5-attributable deaths between 2001 and 2021. These findings suggest that the Canadian population has benefitted broadly from air quality management strategies implemented in North America over recent decades.