Pakistan was ranked the world’s most polluted country in 2025, followed by Bangladesh and Tajikistan, latest air quality data showed on Tuesday.

The South Asian nation topped the list with concentrations of hazardous small particles known as PM2.5 up to 13 times higher than the recommended World Health Organisation (WHO) level, Swiss air quality monitoring firm IQAir said in its annual report.

According to the report, the five most polluted countries were Pakistan (67.3 µg/m³), Bangladesh (66.1 µg/m³), Tajikistan (57.3 µg/m³), Chad (53.6 µg/m³) and Democratic Republic of the Congo (50.2 µg/m³).

Most polluted cities

Loni city of India's largest Uttar Pardesh state, was the most polluted city, recording an annual average PM2.5 concentration of 112.5 µg/m³ – a nearly 23% increase from 2024 and more than 22 times the WHO guideline.

The world’s 25 most polluted cities were all located in India, Pakistan and China, with India home to three of the four worst.

El Paso, Texas, was the most polluted major city in the US, while Southeast Los Angeles, California, ranked as the most polluted region. Seattle, Washington, was the cleanest major American city.

Air quality leaders

Nieuwoudtville, South Africa, was the world’s cleanest city, with an annual average PM2.5 concentration of just 1.0 µg/m³.

Thirteen countries and territories maintained PM2.5 levels below the WHO standard of 5 µg/m³ in 2025, up from seven in 2024. These include French Polynesia, Puerto Rico, US Virgin Islands, Barbados, New Caledonia,
Iceland, Bermuda, Reunion, Andorra, Australia, Grenada, Panama, and Estonia.

However, only 14% of global cities met the WHO air quality standard, down from 17% the previous year. Around 91% of countries and territories (130 out of 143) exceeded the safe level.

For this year’s report, IQAir analyzed data from monitoring stations across 9,446 cities in 143 countries, regions, and territories.