SINGAPORE – Pakistan was ranked the world’s smoggiest country in 2025, with concentrations of hazardous small particles known as PM2.5 up to 13 times higher than the recommended World Health Organization (WHO) level, research showed on March 24.

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 m in 2025, up from seven in 2024.

In total, 130 out of 143 monitored countries and territories failed to meet the WHO guideline. Bangladesh and Tajikistan were second and third on the most polluted list.

Chad, statistically the smoggiest country of 2024, ranked fourth in 2025, but the decline in PM2.5 concentrations in 2025 is likely to be the result of data gaps.

In March 2025, the US 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 Dr Christi Chester Schroeder, lead author of the IQAir report.

The US decision eliminated a primary data source for many smog-prone countries, and Burundi, Turkmenistan and Togo were excluded from the 2025 report because of information gaps.