The top five most polluted countries in 2023 were Bangladesh, Pakistan, India, Tajikistan and Burkina Faso.
A total of 124 (92.5%) out of 134 countries and regions exceeded the WHO annual PM2.5 guideline value of 5 µg/m3.
Africa remains the most underrepresented continent, with a third of the population still lacking access to air quality data.
Climate conditions and transboundary haze were major factors in Southeast Asia, where PM2.5 concentrations rose in nearly every country.
The region of Central & South Asia was home to the top ten most polluted cities in the world.
Begusarai, India was the most polluted metropolitan area of 2023. India was home to the four most polluted cities in the world.
The most polluted major U.S. city was Columbus, Ohio. Beloit, Wisconsin was the most polluted city in the U.S.
Las Vegas, Nevada was the cleanest major city in the U.S.
For the first time in the history of this report, Canada was the most polluted country in Northern America, with the region's 13 most polluted cities located within its borders, mainly due to the massive wildfires last year.
“A clean, healthy, and sustainable environment is a universal human right. In many parts of the world the lack of air quality data delays decisive action and perpetuates unnecessary human suffering. Air quality data saves lives. Where air quality is reported, action is taken, and air quality improves,” states Frank Hammes, Global CEO, IQAir.