Impact of population density and industrial activity on PM2.5-Related adverse health outcomes: A study of the Quebec–Ontario corridor in Canada

Air quality tends to deteriorate in densely populated and industrialized regions, increasing the risk of hospitalization and mortality. The Quebec City-Windsor Corridor (hereafter "Corridor") is a region in Canada characterized by high population density and extensive manufacturing and transportation infrastructure. This study compared PM_2.5-related health outcomes in the Corridor and non-Corridor regions to assess the influence of population density and industrial activity on human health. We analyzed data from 89 census divisions (CDs), representing approximately 80 % of the Canadian population, including 41 CDs within the Corridor (58 % of the population). Daily PM_2.5 concentrations were linked to daily counts of all-cause, circulatory, and respiratory hospitalizations and mortality. A two-stage modeling approach was used: CD-specific risks were estimated using over-dispersed generalized Poisson models, followed by Bayesian hierarchical models to estimate regional (Corridor vs. non-Corridor) and national risks. While all-cause health outcomes showed little regional difference, cause-specific health risks indicated some regional differences varying by cause, season, age, and sex. Compared to the non-Corridor, the Corridor exhibited higher risks (per 10 μg/m³ PM_2.5) for respiratory hospitalization during the cold season for both non-seniors, age 1-65 years, (0.98 %, 95 % CI 0.00-1.90 % versus -0.01 %, -1.36-1.34 %) and seniors, age 66 and over, (0.97 %, 0.08-1.86 % versus -0.60 %, -2.01-0.75 %), and for circulatory mortality during the warm season for seniors (1.86 %, 0.74-2.92 % versus 0.17 %, -1.66-1.92 %) and females (2.74 %, 1.23-4.25 % versus 0.30 %, -2.24-2.78 %). These findings suggest that Corridor residents - especially seniors and females- are subject to greater PM_2.5-related health risks.