Highlights Oxidative potential (OP) of PM 2.5 from Canadian cities was studied using a new acellular chemical assay. Redox potential of simulated lung fluid was highly associated with all physiological OP indicators. Traffic emissions had the highest OP, followed by industrial emissions and crustal matter. OP was strongly associated with black carbon and transition metals, especially Cu, Fe, Mn, and Ti. Organic ligand complexation and aerosol pH were associated with metal solubility and OP.

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