India's Loni earned the dubious distinction of being the world's most polluted city with alarming PM2.5 levels, according to an IQAir report released on 24 March. According to the World Health Organization (WHO) recommendations, the concentration of this hazardous air pollutant was below 5 micrograms per cubic metre last year. This implies that Loni's PM2.5 level is almost 22 times the prescribed limit.

A total of five Indian cities were among the top 10 most polluted cities in the world, including Uttar Pradesh's Loni and Meghalaya's Byrnihat, followed by Delhi, Ghaziabad and West Bengal's Ula (Birnagar). In the second spot in the list is China's Hotan. Four cities in Pakistan also appear on the list of the “World's most polluted cities.”

PM2.5 concentrations (µg/m³) in world's most polluted cities Loni – rank 1 - 112.5

Byrnihat – rank 3 – 101.1

Delhi – rank 4 – 99.6

Ghaziabad – rank 5 – 89.2

Ula – rank 10 – 86.8

View full Image View full Image Loni and Delhi were among the Indian cities that made it to the top 10 list of polluted cities with PM2.5 levels critically high, far above WHO standards.

The 2025 IQAir World Air Quality Report presents “PM2.5 air quality data sourced from 9,446 cities spanning 143 countries, regions, and territories. The information is sourced from more than 40,000 regulatory monitoring stations and low-cost sensors, managed by a wide array of contributors.”

The information on air quality is obtained from government agencies, universities, non-profit organizations, private enterprises, and engaged citizen scientists around the world.

World's most polluted country Pakistan is the world's most polluted country in 2025, with PM2.5 concentrations up to 13 times the recommended WHO level.

Key findings from the 2025 World Air Quality Report: In 2024, 17% of global cities met the WHO annual PM2.5 guideline of 5 µg/m³, but this declined to 14% in 2025.

Only 13 countries meet the WHO annual average PM2.5 guideline — French Polynesia, Puerto Rico, U.S. Virgin Islands, Barbados, New Caledonia, Iceland, Bermuda, Réunion, Andorra, Australia, Grenada, Panama and Estonia.