A study published in Nature Communications highlights that local incomplete combustion emissions, particularly from biomass and fossil fuels, are the main drivers of PM2.5 oxidative potential (OP) in Northern India. The research analyzed PM2.5 samples from five sites in Northern India, including two within Delhi, two in the north-west and south-east of Delhi, and a site 500 km downwind of Delhi. The findings show that local emission sources, such as traffic exhaust, residential heating, and oxidation of unsaturated vapors from fossil fuels, dominate PM pollution in Delhi. Outside Delhi, secondary OA from biomass burning vapors is a major contributor. However, PM-OP is overwhelmingly driven by OA from incomplete combustion of biomass and fossil fuels, including traffic. The study emphasizes the need to address local inefficient combustion processes to reduce PM health exposure in northern India. Air pollution is a major cause of mortality, with high PM2.5 levels in New Delhi being 30 times higher than WHO guidelines. The study also compares PM2.5 mass and OP across sites in Asia-Pacific and Europe, revealing that Indian OP levels are among the highest globally. The research underscores the importance of identifying and quantifying PM2.5 sources, their local vs. regional contributions, and their toxicities to assess health impacts. The study provides insights into the chemical composition and sources of PM2.5, highlighting the role of organic aerosols (OA) in determining OP. The findings suggest that limiting local incomplete combustion of fossil and biofuels will be effective in reducing both PM pollution and oxidative potential. The study also discusses the implications for policymaking, emphasizing the need for targeted local and regional control strategies to achieve the National Clean Air Program (NCAP) goals. The research uses advanced analytical techniques to determine the chemical composition and sources of PM2.5, providing a comprehensive understanding of its composition and sources in Northern India. The study highlights the importance of addressing local emission sources to reduce PM-related health impacts in the region.A study published in Nature Communications highlights that local incomplete combustion emissions, particularly from biomass and fossil fuels, are the main drivers of PM2.5 oxidative potential (OP) in Northern India. The research analyzed PM2.5 samples from five sites in Northern India, including two within Delhi, two in the north-west and south-east of Delhi, and a site 500 km downwind of Delhi. The findings show that local emission sources, such as traffic exhaust, residential heating, and oxidation of unsaturated vapors from fossil fuels, dominate PM pollution in Delhi. Outside Delhi, secondary OA from biomass burning vapors is a major contributor. However, PM-OP is overwhelmingly driven by OA from incomplete combustion of biomass and fossil fuels, including traffic. The study emphasizes the need to address local inefficient combustion processes to reduce PM health exposure in northern India. Air pollution is a major cause of mortality, with high PM2.5 levels in New Delhi being 30 times higher than WHO guidelines. The study also compares PM2.5 mass and OP across sites in Asia-Pacific and Europe, revealing that Indian OP levels are among the highest globally. The research underscores the importance of identifying and quantifying PM2.5 sources, their local vs. regional contributions, and their toxicities to assess health impacts. The study provides insights into the chemical composition and sources of PM2.5, highlighting the role of organic aerosols (OA) in determining OP. The findings suggest that limiting local incomplete combustion of fossil and biofuels will be effective in reducing both PM pollution and oxidative potential. The study also discusses the implications for policymaking, emphasizing the need for targeted local and regional control strategies to achieve the National Clean Air Program (NCAP) goals. The research uses advanced analytical techniques to determine the chemical composition and sources of PM2.5, providing a comprehensive understanding of its composition and sources in Northern India. The study highlights the importance of addressing local emission sources to reduce PM-related health impacts in the region.