Reflection of Sectoral Emissions on Air Quality, Mortality, and Air Pollution Exposure Inequalities in a Metropolitan Context.

Recent case studies have highlighted the inequalities in health impacts associated with air pollution in Canada, emphasizing the need to study the drivers of these inequalities at a sectoral level. The contribution of four air pollution source sectors (off-road, area source, rail, and on-road) to disparities in air emissions was explored using a measure of exposure inequality for the Greater Toronto and Hamilton Area. Additionally, several scenarios were conducted by applying a chemical transport model to understand how changes in sector-specific emissions impact disparities in exposure. Including the contributions of all sources, we observe that the most marginalized individuals constitute the majority of those exposed to the highest level of air pollutants, reflecting inequality in exposure. While mitigation of off-road emissions and elimination of both rail and on-road emissions were associated with the highest reductions in air pollutants and improvements in health benefits, their impacts on exposure inequality differed. The mitigation of off-road emissions decreased exposure disparities, while the mitigation of on-road and rail emissions exacerbated inequalities. This finding emphasizes the importance of identifying emission mitigation scenarios that can achieve high population-level benefits while at the same time reducing disparities in exposure by allocating higher benefits in socially disadvantaged areas.