Mapping oxidative potential of winter air pollution in Toronto using passive samplers

Air pollution is a major public health concern affecting millions of people worldwide. In Canada, major sources of urban air pollution include vehicle emissions, industrial activities, and residential fuel combustion, and nearly 10 million Canadians live in areas with high exposure to traffic-related air pollutants. When inhaled, these pollutants interact with the lung’s natural defences, including the antioxidant system, leading to the formation of reactive oxygen species (ROS). These species can cause oxidative stress, inflammation, and cellular damage, contributing to long-term health effects.
Oxidative potential (OP) is used increasingly as an air quality health metric, reflecting the ability of pollutants to generate ROS. OP is commonly measured using chemical assays such as the ascorbate (Asc), hydroxyl radical (OH), and dithiothreitol (DTT) assays, each capturing different oxidative pathways. Previous studies have shown that OP varies spatially and is influenced by both transition metals and organic compounds. Despite these advances, important gaps remain. Winter air pollution in Toronto is relatively understudied, as most previous work has focused on the summer season. In addition, there is limited understanding of how OP varies within a city, particularly when considering both particulate and gaseous pollutants.
Here, we investigate the spatial distribution of OP (Asc, OH, and DTT), trace metals, and polycyclic aromatic compounds (PACs) across Toronto during winter. Utilizing passive air samplers to capture both particulate and gaseous pollutants, we observed distinct spatial variability. High-traffic areas, specifically Pearson Airport and Highway 401, exhibited elevated OP levels, whereas urban background sites such as North York and Downsview showed lower values, correlating with concentrations of trace metals and PACs. This work identifies winter pollution hotspots and advances our understanding of spatial variability in urban air toxicity, providing evidence to support policies aimed at mitigating air pollution and its associated health risks.