A study by the Centre for Research on Energy and Clean Air (CREA) indicates that 65% of Delhi's air pollution in 2025 originated from outside the city, primarily from NCR districts, with local sources contributing 35%. Vehicular emissions were the largest local contributor, accounting for nearly half of PM2.5 pollution within the city. The study also noted a significant reduction in stubble burning's contribution to Delhi's PM2.5 levels during the 2025 winter season compared to 2024.