Unequal Air Pollution Removal Benefits from City-Owned Street Trees Across Socioeconomically Marginalized Neighbourhoods

Rapid urbanization worldwide has intensified environmental degradation, with fine particulate matter (PM 2 . 5 ) emerging as a major public health threat. The burden of these health risks is unequally distributed, with marginalized communities often facing greater exposure to air pollutants, thereby exacerbating environmental and health inequalities. Urban trees provide ecosystem services, including PM 2.5 mitigation through dry deposition. Dry deposition contributes only modestly to total PM 2.5 removal at the airshed scale. However, the distribution of this removal across diverse neighbourhoods remains an important environmental justice consideration, particularly in near-road environments. While previous research has documented the uneven distribution of urban tree canopy, tree size, and tree density, little is known about how these factors translate into inequities in PM 2.5 removal benefits. This gap limits communities' ability to utilize trees for equitable mitigation of air pollution. Here, we quantified fine-scale spatial heterogeneity in PM 2.5 removal at the individual tree level in Mississauga, Canada. Using high-resolution geospatial analysis and socioeconomic marginalization data from the Ontario Marginalization Index, we estimated street trees removed 27.8 tons of PM 2.5 during the in-leaf season. We also identified marginalized neighbourhoods with low tree benefits, thereby providing targets for intervention. Trees exceeding 50 cm diameter at breast height accounted for 83% of deposition, while planting density explained only 4% of the spatial variance in removal outcomes, indicating that tree size and species selection are more important than density alone. Our approaches offer a replicable framework for urban greening initiatives aimed at enhancing air quality benefits from city-owned street trees worldwide. • Modelled 27.8 tons of PM 2.5 removal by 200,560 city-owned street trees • Shifted from canopy proxies to ecosystem service-based equity in tree benefits • Revealed inequities in PM 2.5 mitigation benefits in marginalized neighbourhoods • Identified priority planting map from tree benefits and marginalization • Conceptualized a replicable framework for equitable global urban forestry design