Why Delhi tops list of six polluted spots across Indo-Gangetic Plain

A report submitted by a joint committee appointed by National Green Tribunal this January considered seasonal variations in PM2.5 levels for 2019 at Delhi (ITO), Amritsar, Murthal, Lucknow, Patna and Kolkata.

Across these six spots, the highest PM2.5 concentration was found to be in Patna (208 µg/m3) in winter, from December to February, followed by Delhi (176 µg/m3). In two other seasons — summer and post monsoon, which cover the periods from March to May and September to November respectively — Delhi has topped the list of six spots.

In summer, the PM2.5 level in Delhi was 87 µg/m3, followed by Lucknow with 83 µg/m3. Similarly, in post monsoon season, Delhi had a significantly higher PM2.5 level of 125 µg/m3 while Haryana’s Murthal had a level of 58 µg/m3 during the same period.

In the monsoon, from June to August, Delhi had a PM2.5 concentration of 51 µg/m3, a close second after Murthal which had a concentration of 59 µg/m3.

The analysis used data from the Central Pollution Control Board (CPCB) and the report was submitted on orders of the NGT.

In terms of annual average PM2.5 levels, Delhi had the highest concentration of 109 µg/m3, followed by Patna at 106 µg/m3, and Kolkata at 85 µg/m3.

An expert, who was part of the committee that prepared the report and did not want to be named, said that in Delhi the sources of pollutants are in higher concentration. “There is a high population in the area and congestion, resulting in concentration of sources of emissions. If you look at emissions per square kilometre area, this region has higher emissions. There are polluting sources in Punjab and Haryana, and Delhi is in proximity, which means there is impact of these emissions as well,” the expert said.

The NGT had heard the matter recently and considered the report issuing an order that directed that the Ministry of Environment, Forest and Climate Change and CPCB to enforce measures like use of cleaner fuel, “switching over to efficient air pollution control technologies”, enforce the Graded Response Action Plan and “vigilance measures to control other pollution sources like dust control, vehicular pollution and the like under the National Clean Air Program”, besides city and district specific action plans within six months.

The NGT’s principal bench was hearing a case on the operation of hot mix plants in Noida beyond its carrying capacity. The joint committee was constituted in 2021 and included experts from IIT Delhi and Kanpur and representatives of the MoEFCC and CPCB.