Pakistan was named the world’s most polluted country in 2025, with hazardous fine particulate matter (PM2.5) reaching levels as high as 13 times the World Health Organization’s recommended maximum, according to Swiss air‑quality monitor IQAir’s annual report. PM2.5 refers to microscopic particles that penetrate deep into lungs and are linked to serious health problems.
IQAir found that only 13 countries and territories met the WHO guideline of under 5 micrograms per cubic metre in 2025, up from seven in 2024, but the global picture remains bleak: 130 of 143 monitored countries and territories failed to meet the WHO standard.
Key findings from the report:
– Bangladesh and Tajikistan ranked second and third after Pakistan on the list of most polluted countries.
– Chad, which statisticians had flagged as the worst-polluted country in 2024, fell to fourth place in 2025; IQAir warns that the apparent improvement may reflect missing data rather than real gains. “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 report.
– The United States ended a global monitoring programme last March that compiled pollution readings from US embassy and consulate buildings, citing budget constraints. The closure removed a primary data source for many smog-prone countries and led to the exclusion of Burundi, Turkmenistan and Togo from the 2025 analysis because of information gaps.
At a city level, India’s Loni was identified as the most polluted city in 2025, averaging 112.5 micrograms per cubic metre of PM2.5, followed by Hotan in China’s Xinjiang region at 109.6 micrograms per cubic metre. The 25 most polluted cities were all located in India, Pakistan and China.
Only 14% of monitored cities met the WHO standard in 2025, down from 17% the previous year. Canadian wildfires contributed to elevated PM2.5 that affected air quality across the United States and as far as Europe. Countries that did meet the WHO guideline in 2025 included Australia, Iceland, Estonia and Panama.
Some nations reported improvements: Laos, Cambodia and Indonesia showed notable PM2.5 reductions largely attributed to a wetter, windier La Niña season, and Mongolia’s average fell 31% to 17.8 micrograms per cubic metre. Overall, 75 countries recorded lower PM2.5 levels than the year before, while 54 saw increases, IQAir reported.
