As much as 65 per cent of Delhi's air pollution in 2025 originated from outside the city, mainly from other NCR districts, while local sources accounted for the remaining 35 per cent, a study said. According to an analysis by the Centre for Research on Energy and Clean Air (CREA), accessed by PTI, winter-period inputs from the Decision Support System indicated that pollution transported into the national capital outweighed emissions generated within the city during 2025. Winter-period source attribution figures showed that vehicular emissions accounted for nearly half of Delhi's local PM2.5 pollution, surpassing contributions from industry, construction and other combustion sources, even as transboundary pollution remained the dominant overall contributor. "Transboundary pollution from NCR districts and neighbouring states plays a major role in Delhi's air pollution. Delhi's geographical location also makes it vulnerable, as northerly and north-westerly winds carry polluted air from