A recent report issued by IQAir, titled “2024 World Air Quality Report” provides data collection information from around the world, drawing upon more than 30,000 air quality monitoring stations across 8,954 locations in 138 countries, territories and regions.
The report makes for sobering reading. Only 17 percent of global cities meet World Health Organisation (WHO) air pollution guidelines. Worse still, just seven countries met the WHO annual average PM2.5 guideline of 5 μg/m3: Australia, Bahamas, Barbados, Estonia, Grenada, Iceland, and New Zealand.
PM2.5 refers to fine particulate matter in the air, with particles 2.5 micrometers or smaller in diameter. These particles can be inhaled and cause serious health problems, particularly for people with respiratory conditions.
Most polluted
In contrast, a total of 126 (91.3%) out of 138 countries and regions exceeded the WHO annual PM2.5 guideline value of 5 μg/m3. Of these, India comes out on top with Byrnihat, being cited as the most polluted metropolitan area of 2024, with an annual average PM2.5 concentration of 128.2 μg/m3.
The five most polluted countries in 2024 were:
- Chad (91.8 μg/m3) more than 18 times higher than the WHO PM2.5 annual guideline
- Bangladesh (78.0 μg/m3) more than 15 times higher than the WHO PM2.5 annual guideline
- Pakistan (73.7 μg/m3) more than 14 times higher than the WHO PM2.5 annual guideline
- Democratic Republic of the Congo (58.2 μg/m3) more than 11 times higher than the WHO PM2.5 annual guideline
- India (50.6 μg/m3) more than 10 times higher than the WHO PM2.5 annual guideline
These countries are among some of the most impoverished in the world, suggesting particles, pollution, and poverty correlate.
Least polluted
Oceania is the world’s cleanest region, with 57 percent of regional cities meeting the WHO PM2.5 annual guideline value of 5 μg/m3.
Asia and the U.S.
Overall, the region of Central & South Asia was home to the top seven most polluted cities in the world. India was home to six of the nine most polluted global cities. PM2.5 concentrations decreased in every country in Southeast Asia, though transboundary haze and lingering El Niño conditions remain major factors.
In terms of high-income countries, the most polluted major U.S. city was Los Angeles, California. Ontario, California was the most polluted city in the United States. As an outlier, Seattle, Washington was the cleanest major city in the U.S. and Mayaguez, Puerto Rico was the cleanest metropolitan area of 2024, with an annual average PM2.5 concentration of 1.1 μg/m3.
Data limitation: Africa
In Africa, the scarcity of real-time, publicly accessible air quality monitoring data is so severe that there is only one monitoring station for every 3.7 million people.
Wildfires
Wildfires in the Amazon rainforest impacted vast areas of Latin America in 2024, with PM2.5 levels in some cities across Brazil’s Rondônia and Acre states quadrupling in September.
