Mixtures of multiple air pollutants from specific industrial or residential sources and mortality from ischemic heart disease, cardiovascular disease, and non-accidental causes: A large general population Canadian cohort study

BackgroundPrevious studies on ambient air pollution and mortality typically focus on individual pollutants rather than their mixtures, and overall pollution rather than air pollution from specific sources. We aimed to assess the associations between ambient mixtures of fine particulate matter (PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3) from various industrial and residential sources, and deaths from ischemic heart disease (IHD), cardiovascular disease (CVD) and non-accidental causes. MethodsWe linked the 2006 Canadian Census Health and Environment Cohort (CanCHEC) with the Canadian Vital Statistics Database, identifying 56190, 98185, and 381050 deaths between 2006 and 2019 from IHD, CVD, and non-accidental causes, respectively. Annual average concentrations of PM2.5, SO2, NO2, and O3 from upstream petroleum, downstream petroleum, non-ferrous smelting, chemical industry and residential fuel combustion were estimated using the Global Environmental Multiscale-Modelling Air Quality and Chemistry (GEM-MACH) model. These concentrations were assigned to CanCHEC participants based on their annual residential postal codes. Quantile g-computation models were used to calculate hazard ratios (HRs) for deaths from IHD, CVD, and non-accidental causes per quartile increase in all four air pollutants from each specific sector. ResultsWe observed significant associations between the mixture of air pollutants and deaths from IHD, CVD, and non-accidental causes for emissions from upstream petroleum [HR: 1.18 (95% CI: 1.12-1.24), 1.12 (1.08-1.16), and 1.05 (1.04-1.05)], downstream petroleum [1.06 (1.05-, 1.04 (1.03-1.05), and 1.03 (1.02-1.03)], the chemical industry [1.10 (1.08-1.13), 1.07 (1.06-1.09), and 1.10 (1.08-1.13)], and residential fuel combustion [1.18 (1.12-1.23), 1.12 (1.08-1.16), and 1.07 (1.05-1.09)]. PM2.5 and SO2 contributed more to the increased risk of death than NO2 and O3. Mortality from CVD or non-accidental causes was not associated with the mixtures of air pollutants from non-ferrous smelting. ConclusionsAmbient PM2.5 and SO2 from certain sectors, but not all, greatly contribute to the increased risk of non-accidental, IHD, and CVD deaths.