Report reveals 2024's most polluted cities, countries: Which US cities made the list?

Yahoo

12-03-2025

The South Asian countries of Pakistan, India and Bangladesh are among the most polluted countries in the world while Australia, New Zealand and Iceland are among the least polluted countries, a new study by IQAir had determined.
IQAir, a Swiss technology company that studies air quality and pollution and specializes in protection against airborne pollutants, released its seventh annual World Air Quality Report Tuesday, which highlighted "alarming trends of the world's most polluted countries, territories, and regions in 2024."
All but one of the world's top 20 most polluted cities last year were in Asia, with the majority of these cities – 13 – in India, the world's most populous country. Neighboring Pakistan followed with four of the most polluted cities, with China and Kazakhstan having one each.
Data from more than 40,000 air quality monitoring stations across 8,954 locations in 138 countries, territories and regions were analyzed by IQAir's air quality scientists for this year's report, IQAir said.
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"Air pollution remains the greatest environmental threat to human health," the report said, adding 99% percent of the global population lives in areas that do not meet recommended air quality guideline levels, according to the World Health Organization (WHO).
Air pollution is also the second leading global risk factor for death, and the second leading risk factor for deaths among children under five, following malnutrition, because of its significant impact on respiratory and developmental health, as per the WHO.
"Air pollution remains a critical threat to both human health and environmental stability, yet vast populations remain unaware of their exposure levels," Global CEO of IQAir Frank Hammes said in a statement. "Air quality data saves lives. It creates much needed awareness, informs policy decisions, guiding public health interventions, and empowers communities to take action to reduce air pollution and protect future generations."
Only 17% of global cities meet WHO air pollution guidelines, with 126 countries and regions out of 138 exceeding the WHO annual PM2.5 guideline value of 5 micrograms/cubic meters. Here's a look at which countries and regions are the most polluted and which are the least, including in the United States.
While Ontario, California was the most polluted city in the U.S. in 2024, the most polluted major U.S. city was Los Angeles, according to the report. In fact, the top five most polluted cities in the U.S. were in California.
Here a list of the 10 most polluted cities in the U.S.:
Ontario, California
Bloomington, California
Huntington Park, California
San Bernardino, California
Fontana, California
Visalia, California
Mission, Texas
Glendora, California
Hanford, California
Conroe, Texas
Map: How is the air quality near me? Track AQI in the U.S.
Seattle, Washington was the cleanest major city in the U.S., though Waimea, Hawaii was the least polluted regional city in the U.S., which overall ranked 116 on the World Air Quality Report 2024.
Here a list of the 10 least polluted cities in the U.S.:
Waimea, Hawaii
Ocean View, Hawaii
Seaside, California
Stanwood, Washington
Mountain View, Hawaii
Lander, Wyoming
Astoria, Oregon
Tillamook, Oregon
Silverdale, Washington
Kihei, Hawaii
The twenty most polluted countries in the world are:
Chad: More than 18 times higher than the WHO PM2.5 annual guideline.
Bangladesh: More than 15 times higher than the WHO PM2.5 annual guideline.
Pakistan: More than 14 times higher than the WHO PM2.5 annual guideline.
Democratic Republic of the Congo: More than 11 times higher than the WHO PM2.5 annual guideline.
India: More than 10 times higher than the WHO PM2.5 annual guideline.
Tajikistan
Nepal
Uganda
Rwanda
Burundi
Nigeria
Egypt
Iraq
Ghana
Indonesia
Gambia
United Arab Emirates
Bahrain
Uzbekistan
Qatar
Byrnihat in eastern India was the most polluted metropolitan area of 2024, with India home to six of the nine most polluted global cities. The region of Central and South Asia, meanwhile, is home to the top seven most polluted cities in the world.
Here's a list of the 10 most polluted cities in the world:
Byrnihat, India
Delhi, India
Karaganda, Kazakhstan
Mullanpur, India
Lahore, Pakistan
Faridabad, India
N'Djamena, Chad
Loni, India
New Delhi, India
Multan, Pakistan
Only seven countries met WHO's annual average PM2.5 guideline. These include:
Australia
Bahamas
Barbados
Estonia
Grenada
Iceland
New Zealand
The cleanest cities in the world in 2024 include:
Mayaguez, Puerto Rico
Nieuwoudtville, South Africa
Dexter, Oregon, U.S.
Haines, Alaska, U.S.
Chu, Kazakhstan
Hawaiian Ocean View, Hawaii, U.S.
Waimea, Hawaii, U.S.
Volcano, Hawaii, U.S.
Emu River, Australia
Kapaau, Hawaii, U.S.
While there has been notable progress in expanding air quality monitoring across various countries, regions, and territories over the past 12 months with low-cost air quality monitors — used by citizen scientists, researchers, community advocates, and local organizations — proven to be effective tools for data collection, "considerable gaps still exist in government-operated regulatory systems in many parts of the world," IQAir said. For example, in Africa, real-time, publicly accessible air quality monitoring data is so scarce that there is only one monitoring station for every 3.7 million people.
"The World Air Quality Report underscores how this urgent, data-driven approach is crucial in driving policy changes and collective efforts to reduce pollution for future generations," IQAir said in its report.
Saman Shafiq is a trending news reporter for USA TODAY. Reach her at [e-mail] and follow her on X and Instagram @saman_shafiq7.
This article originally appeared on USA TODAY: New report reveals 2024's most polluted countries and cities