India’s Loni earned the dubious distinction of being the world’s most polluted city with alarming levels of PM2.5, according to an IQAir report published on March 24. According to the recommendations of the World Health Organization (WHO), last year the concentration of this dangerous air pollutant was below 5 micrograms per cubic meter. This means that the PM2.5 level last year is almost 22 times the prescribed limit.
A total of five Indian cities were among the 10 most polluted cities in the world, including Loni in Uttar Pradesh and Byrnihat in Meghalaya, followed by Delhi, Ghaziabad and Ula in West Bengal (Birnagar). Second on the list is China’s Hotan. Four cities in Pakistan also appear in the list of “world’s most polluted cities”.
The IQAir World Air 2025 Air Quality Report reports “PM2.5 air quality data from 9,446 cities in 143 countries, regions and territories. The information comes from more than 40,000 regulatory monitoring stations and low-cost sensors maintained by a wide range of contributors.”
Air quality information comes from government agencies, universities, nonprofit organizations, private businesses, and engaged citizen scientists from around the world.
The most polluted country in the world
Pakistan is the world’s most polluted country in 2025 with PM2.5 concentrations up to 13 times higher than the WHO recommended level.
