Sector-specific Long-term Associations Between Transportation, Industrial, and Residential Combustion Air Pollutant Mixtures (PM2.5, SO2, NO2, O3) and Neurological Disease-related Mortality in Canada.

BACKGROUND

Improving air quality requires addressing sector-specific air pollution (SSAP). This study examined the relationship between long-term SSAP and Alzheimer's disease and dementia mortality in Canada, and whether associations were modified by neighborhood greenness, educational attainment, and material deprivation.

METHODS

We used data from the 2006 Canadian Census Health and Environment Cohort with mortality follow-up through 2019, linked to the Canadian Vital Statistics-Death database. Annual exposures to ambient air pollutants (i.e., PM2.5, SO2, NO2, and O3) from multiple sectors were estimated using the Global Environmental Multiscale-Modelling Air Quality and Chemistry model (10 km resolution) with sector-specific contributions anchored to 2015 emissions profiles. Quantile g-computation models were used to estimate hazard ratios (HRs) for Alzheimer's disease and dementia per quartile increase in SSAP.

RESULTS

Alzheimer's disease mortality was most strongly associated with SSAP from residential fuel combustion (RES: HR = 1.29; 95% CI: 1.16, 1.43), and was also positively associated with emissions from on-road transportation (HR = 1.22; 95% CI: 1.12, 1.32), ore and mineral industries (ORE: HR = 1.17, 95% CI: 1.10, 1.24), air-marine-rail transportation (HR = 1.12; 95% CI: 1.06, 1.18), and manufacturing (MAN: HR = 1.06; 95% CI: 1.01, 1.11), while inverse associations were observed for the oil and gas sector (HR = 0.85; 95% CI: 0.81, 0.88). Dementia mortality was positively associated with oil and gas (HR = 1.06; 95% CI: 1.03, 1.09), and inversely associated with air-marine-rail transportation (HR = 0.88; 95% CI: 0.85, 0.92) and ORE (HR = 0.89; 95% CI: 0.85, 0.92). Associations were generally stronger in lower greenness areas and among individuals with lower educational attainment, although heterogeneity by sector was observed.

CONCLUSION

SSAP mixtures were associated with Alzheimer's disease and dementia mortality in Canada. The direction and magnitude of associations varied by sector and by environmental and sociodemographic context, supporting the value of targeted, sector-specific mitigation strategies to reduce neurodegenerative mortality risk.