The Central Pollution Control Board (CPCB) has informed the National Green Tribunal (NGT) that the incomplete combustion of biomass and fossil fuels, including emissions from traffic, is the primary contributor to air pollution in Delhi. This statement was made in response to an earlier inquiry by the NGT regarding air pollution from sources such as biomass burning, vehicular pollution from old or poorly maintained vehicles, and the use of coal.

In a report dated 18 September, the CPCB referenced a study that identified the incomplete combustion of biomass and fossil fuels, particularly from traffic, as the dominant contributor to the oxidative potential (OP) of particulate material in Delhi's air. The OP measures the health impacts of exposure to airborne particulate matter (PM), which consists of solids, chemicals, liquids, and aerosols.

According to the CPCB, the study highlighted ammonium chloride and organic aerosols from traffic exhaust, residential heating, and the oxidation of unsaturated vapours from fossil fuels as the main sources of PM in Delhi. The CPCB also noted that steps have been taken to reduce vehicular emissions, such as the introduction of BS-VI compliant engines, which improve fuel combustion and engine efficiency. Additionally, Vapour Recovery Systems (VRS) have been installed at 3,256 petrol stations across the National Capital Region (NCR) to reduce the release of vapours into the environment.

Addressing the issue of biomass burning, including crop stubble, the report mentioned that the Ministry of Agriculture and Farmers Welfare is implementing a scheme to subsidise crop residue management machinery and establish custom hiring centres in states such as Punjab, Haryana, Uttar Pradesh, Madhya Pradesh, and Delhi. Furthermore, the Commission for Air Quality Management (CAQM) in NCR has directed thermal power plants within 300 km of Delhi and captive power plants in NCR industries to co-fire 5-10% biomass with coal. The use of coal in industries within the NCR has been banned, and biomass has been approved as a fuel.

The report also noted that the CAQM has instructed the state governments of Punjab, Haryana, and Uttar Pradesh to enforce revised action plans to effectively control and eliminate stubble burning.