Oxidative potential of fine particulate matter emitted from traditional and improved biomass cookstoves†

Exposure to PM_2.5 emitted from traditional biomass cookstoves is a significant health risk for nearly one-third of the global population. Improved cookstoves aim to reduce pollutant emissions, but there is limited evidence of whether PM_2.5 toxicity is also reduced. Using the dithiothreitol (DTT) assay to measure the potential for PM_2.5 chemical components to induce oxidative stress through antioxidant depletion and/or oxidant generation, we characterized the mass- and volume-normalized DTT activity of PM_2.5 emitted from a traditional three-stone fire cookstove and three improved cookstoves burning wood or charcoal fuels. Although improved cookstoves typically yield lower PM_2.5 mass concentrations compared to traditional three-stone cookstove, exposure to DTT active PM_2.5 is not always reduced due to increases in mass-normalized DTT activity. A notable decrease in DTT active PM_2.5 exposure (by 67%) was only observed for a forced-draft improved cookstove burning wood, where low PM_2.5 mass concentration offsets the increased mass-normalized DTT activity. Additionally, elemental carbon and water-soluble organic matter were identified as key predictors of volume-normalized DTT activity. Compared to wood, the use of charcoal led to a 61–86% reduction in exposure to DTT active PM_2.5, owing to both lower PM_2.5 mass concentration and mass-normalized DTT activity. This further supports a proposed strategy whereby biomass fuel treatment can potentially reduce household exposure to toxic PM_2.5. Collectively, our findings emphasized the need to consider not only the mass concentration but also the toxic properties of PM_2.5 when evaluating the health impacts of cookstoves and fuels.