The Commission for Air Quality Management (CAQM) released a report on January 21, 2026, identifying the main causes of winter pollution in Delhi. The biggest contributor is secondary particulate matter at 27%, followed by transport at 23%, biomass burning including crop and waste burning at 20%, dust at 15%, and industry at 9%. This report was compiled from existing studies after the Supreme Court asked CAQM for clarity on worsening air quality. The CAQM said, "While conducting the meta-analysis, the primary focus has been to bring a uniform and unanimous opinion on air pollution sources to help bridge the gap between existing data and actionable policies." No new pollution sources were found, but the report noted studies used different methods. New detailed emissions and source studies will be done in 2026 by research groups including IIT Delhi and the Indian Institute of Tropical Meteorology Pune. These studies will support the Air Quality Early Warning System and Decision Support System, which CAQM paused in 2024 due to forecasting errors. Secondary particulate matter forms in the air when harmful gases like nitrogen oxides and sulphur dioxide react with ammonia from fertilizers and livestock. A 2024 study showed that 80% of ammonia in India comes from these two sources. The CAQM report explains how this ammonia reacts with other chemicals to form fine particles that make up 25% to 60% of PM2.5 pollution. These particles can deeply harm human health, causing diseases like asthma, lung cancer, and respiratory infections. Understanding these causes helps design better pollution control policies for Delhi.