Impact of lowering fine particulate matter from major emission sources on mortality in Canada: A nationwide causal analysis.

Emissions of fine particulate matter (PM 2.5 ) from human activities have been linked to substantial disease burdens, but evidence regarding how reducing PM 2.5 at its sources would improve public health is sparse. We followed a population-based cohort of 2.7 million adults across Canada from 2007 through 2016. For each participant, we estimated annual mean concentrations of PM 2.5 and the fractional contributions to PM 2.5 from the five leading anthropogenic sources at their residential address using satellite observations in combination with a global atmospheric chemistry transport model. For each source, we estimated the causal effects of six hypothetical interventions on 10-y nonaccidental mortality risk using the parametric g-formula, a structural causal model. We conducted stratified analyses by age, sex, and income. This cohort would have experienced tangible health gains had contributions to PM 2.5 from any of the five sources been reduced. Compared with no intervention, a 10% annual reduction in PM 2.5 contributions from transportation and power generation, Canada's largest and fifth-largest anthropogenic sources, would have prevented approximately 175 (95%CI: 123-226) and 90 (95%CI: 63-117) deaths per million by 2016, respectively. A more intensive 50% reduction per year in PM 2.5 contributions from the two sources would have averted 360 and 185 deaths per million, respectively, by 2016. The potential health benefits were greater among men, older adults, and low-income earners. In Canada, where PM 2.5 levels are among the lowest worldwide, reducing PM 2.5 contributions from anthropogenic sources by as little as 10% annually would yield meaningful health gains.