Pakistan was ranked the world’s most polluted country in 2025, with concentrations of hazardous small particles known as PM2.5 currently 13 times higher than the World Health Organisation’s recommended level, according to a report. The five most polluted countries were Pakistan (67.3 μg/m³), Bangladesh (66.1μg/m³), Tajikistan (57.3 μg/m³), Chad (53.6 μg/m³), and the Democratic Republic of the Congo (50.2 μg/m³).
The world’s top 25 most polluted cities were all recorded to be in India, Pakistan, and China. India’s Loni was the world’s most polluted city in 2025, with an average PM2.5 level of 112.5 micrograms. This was followed by Hotan in the northwestern Chinese region of Xinjiang at 109.6 micrograms.
Swiss air quality monitoring firm IQAir said in its annual report that 13 countries and territories kept average PM2.5 levels at the WHO standard of less than 5 micrograms per cubic meter last year, which is up from seven in 2024. According to the report, a total of 130 out of the 143 monitored countries and territories have failed to meet the WHO guideline.
U.S. Shut Down Global Monitoring Programme
Statistically, the most polluted country of 2024 was reported to be Chad. Now ranked fourth, however, the decline in PM2.5 levels likely could be chalked up to data gaps.
Last March, the United States shut down a global monitoring programme that compiled pollution data collected from its embassy and consulate buildings, citing budget constraints.
“The loss of the data in March made it appear there was a significant drop in PM2.5 levels (in Chad), but the fact of the matter is that we don’t know,” said Christi Chester Schroeder, lead author of the IQAir report.
The U.S. decision eliminated a primary data source for many smog-prone countries. Burundi, Turkmenistan, and Togo were also excluded from the 2025 report because of information gaps.
Only 14% Of Cities Meet WHO Criteria
Only 14% of the world’s cities have managed to meet the WHO standard in 2025, down from 17% in 2024, with Canadian wildfires driving up the PM2.5 across the U.S. to as far as Europe.
The countries that met the standard in 2025 included Australia, Iceland, Estonia, and Panama. Meanwhile, Laos, Cambodia, and Indonesia have all reported significant reductions compared to the previous years, mainly due to wetter and windier La Niña weather. Mongolia also saw average concentrations dropping 31% to 17.8 micrograms per cubic meter.
Overall, 75 countries reported lower PM2.5 levels in 2025 compared to a year earlier, with 54 recording higher average concentrations, according to IQAir.
(With inputs from Reuters)
