CAQM: Secondary particulates top Delhi-NCR's winter air pollution list
Delhi-NCR's winter air has the largest contribution from "secondary particulate matter," according to a new CAQM report, a synthesis of existing studies, in a report made public on January 21, 2026.
These make up 27% of the region's PM2.5, while transport (23%), burning waste (20%), dust (15%), and industry (9%) follow close behind.
What are secondary particulates, anyway?
They're not released directly, but form when gasses like sulfur dioxide and nitrogen oxides—primarily from coal combustion, brick kilns and combustion/transport sources—mix in the air with ammonia from fertilizers and livestock that reacts with oxidized SO2/NOx products.
These tiny particles can get deep into your lungs and are linked to asthma and other serious health issues.
Supreme Court steps in
Reacting to the findings, the Supreme Court has told Delhi and NCR authorities to come up with detailed action plans within four weeks.
The focus is on long-term fixes suggested by CAQM, with court oversight expected to continue.