Delhi experienced its most polluted December since 2018, with average daily PM2.5 levels exceeding India's safe limit on over 31 days. The monthly average PM2.5 was 211 micrograms per cubic meter, significantly higher than the WHO's recommended 15 μg m3 and India's 60 μg m3 standard. Experts suggest persistent year-round emissions from industry, transport, and power plants, rather than just seasonal factors like stubble burning, are driving the pollution, necessitating long-term emission reduction strategies.