Delhi is having the worst December air since 2018 and stubble burning is not the cause, finds an analysis carried out by environmental think tank Centre for Science and Environment (CSE) published on Wednesday afternoon.
According to official data accessed by The Plurals, Delhi recorded an average Air Quality Index (AQI) of 349 this December, highest since 2018 when the Indian capital had an average AQI of 360. An AQI in excess 300 in India is categorized as “Very Poor”, and implies a high risk of serious health impacts for the entire population.
This analysis is based on the real time data available from the functional air quality monitoring stations in Delhi-NCR while the estimate of contribution of farm stubble fire smoke to Delhi’s air quality is sourced from Ministry of Earth Science’s System of Air Quality and Weather Forecasting and Research (SAFAR).
December air poorer than earlier months
The study compares the “early winter” months of October and November— a period heavily influenced by farm fires — with the “post-farm fire” period of December, when the impact of stubble burning becomes negligible, “less than one per cent”, according to a CSE researcher.
“This post-stubble phase has experienced intense, widespread smog across NCR — more severe than the stubble burning period. The persistence of pollution beyond farm fires is strongly evident in this analysis,” says the report.
“These findings reveal a concerning reality. Delhi’s winter pollution does not dissipate once stubble burning ends; instead, it intensifies. Despite the farm-fire contribution to PM2.5 levels dropping sharply in December the average PM2.5 levels have actually increased,” pointed out Anumita Roychowdhury, executive director-research and advocacy at CSE and the report lead.
Local sources responsible
“The stark contrast between declining fire influence and rising pollution levels indicates dominance of local and regional sources — vehicles, industry, waste burning, solid fuels for domestic cooking and heating,” she added.
The expert pointed out to The Plurals after publication of the report that while managing stubble burning is important, air quality goals cannot be met without aggressive, year-round action against urban and regional emission sources. “The smog is sustained by a combination of local emissions, regional inflows, and secondary aerosol formation, requiring coordinated airshed-level action alongside aggressive control of local sources,” Roychowdhury said.
The build-up of pollution was felt across various urban centers in the NCR. While some towns saw marginal declines, most cities recorded a sharp rise in PM2.5 levels. Noida saw 38 per cent increase; Ballabhgarh 32 per cent increase; Baghpat 31 per cent increase and Delhi 29 per cent increase, the report says.
“This regional spike is driven by local emission sources and exacerbated by stagnant winter meteorology, which prevents the dispersion of pollutants,” said Sharanjeet Kaur, deputy programme manager, Urban Lab, CSE.
Wider NCR responsible
The data shows that the contribution from neighbouring districts is dominant.
“Data from the Decision Support System (DSS) for December 1-15 highlights the complexity of the problem. During this period, local sources within Delhi accounted for only about 35 per cent of total PM2.5. The remaining 65 per cent originated from neighbouring NCR districts and regions further away,” says the report.
“Within Delhi’s local contribution, vehicles are the dominant primary source, accounting for nearly half of all local emissions,” said Shambhavi Shukla, programme manager, Clean Air programme at CSE.