Local incomplete combustion emissions define the PM2.5 oxidative potential in Northern India

The oxidative potential (OP) of particulate matter (PM) is a major driver of PM-associated health effects. In India, the emission sources defining PM-OP, and their local/regional nature, have yet to be established. To address this gap, we determined the geographical origin, sources of PM, and its OP at five Indo-Gangetic Plain (IGP) sites inside and outside Delhi. Our findings reveal that although uniformly high PM concentrations were recorded across the entire region, local emission sources and formation processes dominate PM pollution. PM-OP is overwhelmingly driven by OA from incomplete combustion of biomass and fossil fuels, including traffic. These findings suggest that addressing local inefficient combustion processes can effectively mitigate PM health exposure in Northern India.