Delhi remains worst polluted city

Delhi has once again emerged as India’s most polluted region, topping a new satellite-based assessment of air quality across 33 states and Union territories. 

According to the analysis by the Centre for Research on Energy and Clean Air (CREA), the National Capital Territory recorded an annual mean PM2.5 concentration of 101 micrograms per cubic metre (µg/m³) between March 2024 and February 2025 — 2.5 times India’s own national standard and 20 times higher than the World Health Organisation’s recommended limit.

Chandigarh logged the second-highest PM2.5 level at 70 micrograms per cubic metre between March 2024 and February 2025, followed by Haryana (63) and Tripura (62). The pollution crisis extends across northern India, with average PM2.5 concentrations (fine particulate matter with a diametre of less than 2.5 micrometres in the air) in all States in the region — including Delhi, Chandigarh, Haryana, Punjab, Uttar Pradesh, Himachal Pradesh, Uttarakhand, and Jammu & Kashmir — exceeding the NAAQS, according to the analysis. Several other States, including Assam (60), Bihar (59), West Bengal (57), Punjab (56), Meghalaya (53) and Nagaland (52), also surpassed the National Ambient Air Quality Standard (NAAQS) of 40 micrograms per cubic metre.

According to the analysis, about 60 per cent of districts (447 out of 749) exceed India’s National Ambient Air Quality Standards (NAAQS).  Pollution was highly concentrated in specific regions, with Delhi and Assam each contributing 11 of the 50 most polluted districts. Bihar and Haryana followed, with seven each. Other States in the top tier included Uttar Pradesh (4), Tripura (3), Rajasthan (2) and West Bengal (2).

PM2.5 refers to particulate matter with a diametre of 2.5 micrometres or smaller — about 30 times thinner than a human hair.

Delhi, Tripura, Punjab, Haryana, Himachal Pradesh, Meghalaya, and Chandigarh maintained 100 per cent district-level exceedance in all seasons except the monsoon. Exceedance of the PM2.5 NAAQS is highest in winter with 616 of 749 districts (82 per cent); remains significant in summer with 405 districts (54 per cent); drops sharply during the monsoon to 74 districts (10 per cent); and surges again post-monsoon to 566 districts (75 per cent).

In several regions, every monitored district exceeded national norms, including Delhi, Assam, Punjab, Haryana, Chandigarh, Himachal Pradesh, Meghalaya, Tripura, and Jammu & Kashmir. Ladakh, Andaman & Nicobar Islands, and Lakshadweep were excluded due to insufficient monitoring data.