New Delhi is the most air-polluted city in the country, with air pollution levels 2.5 times higher than Indian standards and 20 times higher than the World Health Organisation (WHO) guidelines.

Delhi is not an exception; 60% of districts (447 out of 749) exceed India’s National Ambient Air Quality Standards (NAAQS). Assam (11 districts) and Delhi (11 districts) together account for nearly half of the top 50 most polluted districts, followed by Haryana and Bihar with seven each.

The pollution crisis extends across northern India, with average PM2.5 concentrations (fine particulate matter with a diameter of less than 2.5 micrometers 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, says the Centre for Research on Energy and Clean Air (CREA), an independent research organisation focused on air pollution trends and health impacts in India.

Delhi recorded the highest pollution levels with an annual mean PM2.5 concentration of 101 µg/m³, 2.5 times the Indian standard and 20 times the WHO guideline. Delhi, Tripura, Punjab, Haryana, Himachal Pradesh, Meghalaya, and Chandigarh maintained 100% 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%); remains significant in summer with 405 districts (54%); drops sharply during the monsoon to 74 districts (10%); and surges again post-monsoon to 566 districts (75%).

“India’s clean air challenge can no longer be viewed through the narrow lens of city pollution or winter smog. The latest data clearly show that poor air quality persists through most of the year, affecting nearly every region of the country,” said Manoj Kumar, analyst with CREA, who led the study.

Of the 33 states and union territories assessed, 28 had at least one district exceeding the annual NAAQS, and none met the annual WHO guideline. Delhi consistently ranks as the most polluted state, recording an annual population-weighted mean concentration of 101 µg/m³, 2.5 times the NAAQS and 20 times the WHO guideline. Southern states with annual PM2.5 levels below the NAAQS have a clear policy opportunity to move toward WHO interim targets by adopting stricter measures.

Several states are in universal non-compliance, where all monitored districts exceed the NAAQS. These include Delhi, Assam, Punjab, Haryana, Chandigarh, Himachal Pradesh, Meghalaya, Tripura, and Jammu & Kashmir. Several other states show a large majority of districts breaching the norm, such as Bihar (37 of 38), West Bengal (22 of 23), Gujarat (32 of 33), Nagaland (11 of 12), Rajasthan (30 of 33), and Jharkhand (21 of 24), along with Uttar Pradesh (49 of 75), Odisha (22 of 30), Madhya Pradesh (27 of 52), and Maharashtra (14 of 36). In the Northeast, Arunachal Pradesh (12 exceed, 13 comply) and Manipur (five exceed, 11 comply) fall into the transitional category.

At the other end of the spectrum, several states have the majority of their districts below the NAAQS, such as Andhra Pradesh, Telangana, Kerala, Sikkim, Goa, Karnataka, and Tamil Nadu, according to the CREA study.