Source and condition specific toxicity of combustion-derived PM: Linking physicochemical properties with acellular and cellular assays.

This study investigates particulate matter (PM) generated from wood, coal, and bunker fuel combustion under controlled conditions, examining its physicochemical properties, oxidative potential, and cytotoxicity. Hydroxyl radical (•OH) formation was assessed using the TAOH assay, while cellular toxicity was evaluated via MTT and LDH assays in bronchial epithelial cells. Low-temperature wood and coal combustion produced PM rich in redox-active metals (Fe, Cu, Mn), generating high initial •OH through Fenton-like reactions, but with minimal cytotoxicity-likely due to limited cellular uptake or buffering mechanisms. In contrast, bunker fuel PM under running conditions caused strong cytotoxic responses (reduced viability, membrane damage) despite low •OH levels, attributed to elevated Zn and hydrophobic organics (e.g., alkylcyclohexanes, hopanes). High-temperature combustion produced moderate but sustained •OH levels, likely from slowly cycling organics (e.g., PAHs), with limited acute cytotoxicity. These results highlight the complex and source-specific nature of PM toxicity. They underscore the limitations of relying on oxidative potential alone and the need for integrated chemical and cellular assays to better assess health risks and guide targeted emission control strategies.