Within-City Spatial Variations in Multiple Measures of PM_2.5 Oxidative Potential in Toronto, Canada

Area of Science:

• Environmental Health
• Atmospheric Chemistry
• Air Pollution Epidemiology

Background:

• Few studies have investigated spatial variations in the oxidative potential of fine particulate matter (PM2.5) within urban areas.
• Oxidative potential is a key toxicological measure of PM2.5, reflecting its capacity to induce oxidative stress.
• Understanding spatial heterogeneity is crucial for targeted public health interventions.

Purpose of the Study:

• To characterize within-city spatial variations in multiple measures of PM2.5 oxidative potential in Toronto, Canada.
• To identify associations between PM2.5 oxidative potential and land use/traffic-related factors.
• To evaluate the performance of multivariable models in predicting PM2.5 oxidative potential.

Main Methods:

• Collected integrated 2-week PM2.5 samples from 67 sites in summer and 42 sites in winter (2016-2017).
• Measured three oxidative potential metrics: glutathione/ascorbate-related (OPAA), glutathione-related (OPGSH), and dithiothreitol depletion (OPDTT).
• Developed multivariable linear models using land use/traffic data, PM2.5 metals, and black carbon.

Main Results:

• All three oxidative potential measures showed substantial spatial variation across Toronto.
• OPAA and OPDTT were strongly associated with traffic indicators (Fe, Cu, black carbon), while OPGSH was less so.
• Model performance for predicting oxidative potential varied by metric and season, with OPDTT performing best in winter (R-squared=0.55) and OPAA in summer (R-squared=0.48).

Conclusions:

• Significant within-city gradients exist for PM2.5 oxidative potential, influenced by local sources.
• Traffic-related PM2.5 components are key drivers for OPAA and OPDTT.
• Improved source apportionment data is needed to enhance predictive models for urban air pollution oxidative potential.