New Delhi, March 24 Pakistan is the most polluted country in the world, followed by Bangladesh and Tajikistan, while India is in sixth place, according to the 8th World Air Quality Report.
The 2025 edition of the report, published by IQAir, a Swiss air quality technology company, is based on analysis of data from monitoring stations across 9,446 cities in 143 countries, regions, and territories.
The data has been sourced from more than 40,000 regulatory monitoring stations and low-cost sensors managed by a wide array of contributors, including government agencies, universities, non-profit organizations, private enterprises, and engaged citizen scientists around the world.
While China is in 20th place among the most polluted countries in the world, the USA is in 120th place, and the UK is in 110th place.
According to the report, only 13 countries or territories – French Polynesia, Puerto Rico, US Virgin Islands, Barbados, New Caledonia, Iceland, Bermuda, Réunion, Andorra, Australia, Grenada, Panama, and Estonia – met the World Health Organization's (WHO) annual average PM2.5 guideline.
The report states, "130 out of 143 countries or territories (91 per cent) exceeded the WHO annual average PM2.5 guideline value. The five most polluted countries were Pakistan, Bangladesh, Tajikistan, Chad, and the Democratic Republic of the Congo. The world's 25 most polluted cities were all located in India, Pakistan, and China, with India hosting three of the four most polluted."
Nieuwoudtville, South Africa, was the world's cleanest city, with an annual average PM2.5 concentration of 1.0 µg/m³.
Among cities, Loni in Uttar Pradesh is the most polluted, followed by Hotan in China, and Byrnihat in Meghalaya, India. Delhi is in fourth place, followed by Faisalabad in Pakistan.
"In 2025, wildfire activity severely impacted regions that have historically experienced relatively low PM2.5 levels. As a result, only 14 per cent of the global cities met the WHO annual PM2.5 guideline in 2025, compared to 17 per cent in 2024."
"This downward trend serves as a stark reminder that maintaining clean air requires active stewardship and a proactive strategy – regardless of historical performance," the report said.
Maintaining clean air is a long-term commitment to incremental improvement rather than a single policy goal achieved or annual target concentration reached, it said.
"For children, however, the impact of air pollution exposure can last a lifetime; the respiratory damage sustained during developmental years is often irreversible. As the demographic with the least agency in these environmental shifts, children are left to bear the permanent health costs of air quality they did not choose," the report said.