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

Exposure to PM2.5 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 PM2.5 toxicity is also reduced. Using the dithiothreitol (DTT) assay to measure the potential for PM2.5 chemical components to induce oxidative stress through antioxidant depletion and/or oxidant generation, we characterized the mass- and volume-normalized DTT activity of PM2.5 emitted from a traditional three-stone fire cookstove and three improved cookstoves burning wood or charcoal fuels. Although improved cookstoves typically yield lower PM2.5 mass concentrations compared to traditional three-stone cookstove, exposure to DTT active PM2.5 is not always reduced due to increases in mass-normalized DTT activity. A notable decrease in DTT active PM2.5 exposure (by 67%) was only observed for a forced-draft improved cookstove burning wood, where low PM2.5 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 PM2.5, owing to both lower PM2.5 mass concentration and mass-normalized DTT activity. This further supports a proposed strategy whereby biomass fuel treatment can potentially reduce household exposure to toxic PM2.5. Collectively, our findings emphasized the need to consider not only the mass concentration but also the toxic properties of PM2.5 when evaluating the health impacts of cookstoves and fuels. Reduced PM2.5 emissions from improved cookstoves do not necessarily equate to reduced exposure to toxic PM2.5, due to changes in PM2.5 chemical composition and toxic potency.