The 10 US cities with the worst air pollution in 2023 got a big boost from wildfires, according to a new study, recording pollution levels well above maximum safe levels.
But big cities like New York, Los Angeles and Chicago, places that many people associate with poor air quality, were nowhere near the top 10 in the world, let alone the country.
In its annual survey of the world’s worst cities for air pollution, Swiss air technology company IQAir found that more than 1,000 cities in the US experienced air pollution levels several times higher than the international standard for poor air quality.
This threshold is the World Health Organization (WHO) guidelines for the type of air pollution identified as most dangerous to human health: particles smaller than 2.5 microns.
Here is the list of the 10 most air polluted cities in the US by 2023, according to IQAir measurements at 7,800 monitoring locations around the world:
- 1. Coraopolis, Pennsylvania
- Forest Park, Georgia, USA
- Cave Junction, Oregon, USA
- Happy Camp, California, USA
- Adrian, Michigan
- Claymont, Delaware, USA
- Robesonia, Pennsylvania, USA
- Attleboro, Massachusetts, USA
- Elwood, Illinois, USA
- Huntington, Indiana, USA
These cities had the highest average levels of 2.5-micron particles or aerosols, also known as PM2.5.
This type of air pollution comes from cars, coal-fired power plants, and waste burning—common activities around the world, no matter where you live.
According to the WHO, a “safe” amount of PM2.5 is an average exposure of 0 to 5 micrograms per cubic meter of air per year.
But the 10 most polluted US cities in 2023 accumulated between 15 and 20 micrograms per cubic meter.
What makes these cities so dirty?
In addition to cars and coal, PM2.5 can also come from burning wood, and according to IQAir, the massive increase in air pollution in the US in 2023 was due to the wildfires that ravaged Canada for months.
The resulting smoke that spread across the United States exposed the average person to 66 percent more fine particle pollution than the previous record year in 2021.
Coraopalis, Pennsylvania, was found to be the most polluted city in the US in 2023. But the Canadian wildfires are mainly to blame, as their
Cave Junction, Oregon, the third most polluted city in the US, also had an unexpected year: it went from 9.7 micrograms of PM2.5 per cubic meter in 2022 to 17.1 in 2023.
For the most part, there’s nothing especially dirty about any of these cities.
Coraopolis, Pennsylvania, for example, measured 19.3 micrograms per cubic meter of PM2.5 on average in 2023, according to IQAir measurements.
But these pollution levels do not reflect typical Coraopalis air, which measured just 7.2 in 2022.
Much of this came in September, when levels hit 42.1, and October, when they hit a sweltering 54.2.
And the same goes for the other cities on this list: pollution levels skyrocketed in 2023, especially in summer and fall, corresponding to the Canadian wildfires.
Cave Junction, Oregon, the third most polluted city in the US, also had an unexpected year: it went from 9.7 micrograms of PM2.5 per cubic meter in 2022 to 17.1 in 2023.
Claymont, Delaware, was the sixth most polluted city in the US in 2023, according to IQAir. Despite a spike in summer corresponding to wildfires, the year 2023 was no fluke.
Forest Park, Georgia, the second most air-polluted city in the US in 2023, earned similarly poor ratings in 2022 and 2021. As part of greater Atlanta, it is home to a crisscrossing tapestry of congested roads.
In other cases, 2023 was not an isolated year.
Claymont, Delaware, for example, was the sixth most polluted city in the US in 2023, according to IQAir. Despite a spike in summer corresponding to wildfires, the year 2023 was no fluke.
In 2023, its average PM2.5 concentration was 16.5, only a slight increase from 16.4 in 2022 and even a decrease from 16.7 in 2021.
For Claymont, the culprit has already been identified: the roads.
Interstates I-495 and I-95 pass through it, spewing so much air pollution that barely a single spike was recorded.
Regardless of their source, PM2.5 clouds are just the right size to linger in the lungs and infiltrate the bloodstream, making them particularly concerning from a public health perspective.
Adrian, Michigan, the fifth most polluted city in the US in 2023, was only slightly worse that year than the previous.
According to the WHO, outdoor air pollution is estimated to cause more than 4 million premature deaths around the world annually.
Being exposed to high levels of particles, even for relatively short periods of 24 hours, can be harmfulaccording to the California Air Resources Board.
These aerosols can contribute to respiratory diseases such as asthma and bronchitis, and increase a person’s chances of having to go to the hospital for heart or lung causes.
Exposure to these nanoparticles has even been linked to dementia and cognitive decline.
The United States ranked favorably on one measure of air quality: Out of 134 countries, it ranked 102nd dirtiest in the world.
But that’s just a national average, and someone in Delaware can’t breathe Montana air.
So for anyone looking for the least polluted air, here are the rankings from IQAir data:
- Makawao, Hawaii
- Telluride (Colorado)
- Tulalip, Washington
- Homer, Alaska
- Waimea, Hawaii
- Koloa, Hawaii
- Kihei, Hawaii
- Bayfield (Colorado)
Attentive readers will see a pattern.