Most polluted US cities REVEALED in new study - and Los Angeles and New York don't even make the top 10

The 10 cities in the US with the worst air pollution in 2023 got a major boost from wildfires, according to a new study, clocking levels of pollution that are far above the maximum safe levels.

But big cities like New York City, Los Angeles, and Chicago, places that many people associate with low air quality, weren't anywhere near the top 10 in the world, let alone in the country.  

In its annual survey of the world's worst cities for air pollution, Swiss air technology company IQAir found that over 1,000 cities in the US experienced air pollution levels multiple times higher than the international standard for poor air quality.

This threshold is the World Health Organization's (WHO's) guidelines for the type of air pollution identified as most hazardous to human health: particulate matter smaller than 2.5 microns.

Here is the list of the 10 most air polluted cities in the US for 2023, according to IQAir's measurements at a reported 7,800 monitoring locations worldwide: 

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Gas stoves produce up to 10 times more aerosols per cubic nanometer than what's measured at busy roadsides.

1. 1. Coraopolis, PA
2. Forest Park, GA
3. Cave Junction, OR
4. Happy Camp, CA
5. Adrian, MI
6. Claymont, DE
7. Robesonia, PA
8. Attleboro, MA
9. Elwood, IL
10. Huntington, IN 

These cities had the highest average air levels of 2.5-micron particulates or aerosols, known also as PM2.5.

This type of air pollution comes from cars, coal powerplants, and burning waste - common activities all around the world, no matter where you live.

According to the WHO, a 'safe' amount of PM2.5 is an average exposure of 0-5 micrograms per cubic meter of air per year.

But the top 10 most air polluted cities in the US in 2023 all racked up 15-20 micrograms per cubic meter.

What makes these cities so dirty? 

Besides cars and coal, PM2.5 can also come from burning wood, and according to IQAir, the massive spike in air pollution across the US in 2023 came from the wildfires that raged in Canada for months.

The resulting smoke which swept across the United States saw the average person exposed 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 it mostly has the Canadian wildfires to blame, as its 

Cave Junction, Oregon, the third most polluted city in the US, also had a fluke year, spiking from 9.7 micrograms of PM2.5 per cubic meter in 2022 to 17.1 in 2023.

In most cases, there is 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's measurements. 

But these pollution levels don't reflect the typical air in Coraopalis, which measured just 7.2 in 2022.

Much of this came from September when levels reached 42.1 and October when they hit a suffocating 54.2. 

And it's the same story for the other cities on this list: Pollution levels spiked in 2023, especially in summer and fall,  corresponding with the Canadian wildfires. 

Cave Junction, Oregon, the third most polluted city in the US, also had a fluke year, spiking from 9.7 micrograms of PM2.5 per cubic meter in 2022 to 17.1 in 2023. 

Claymont, Delaware was the 6th most polluted city in the US in 2023, according to IQAir. Despite a summer spike corresponding with the wildfires, its 2023 was not a fluke.

Forest Park, Georgia, the second most air-polluted city in the US in 2023, had similarly bad ratings in 2022 and 2021. Part of greater Atlanta, it is home to a crisscrossing tapestry of congested highways.

In other cases, 2023 was not a one-off.

Claymont, Delaware, for example, was the sixth most polluted city in the US in 2023, according to IQAir. Despite a summer spike corresponding with the wildfires, its 2023 was not a fluke. 

In 2023 its average PM2.5 concentration was 16.5, only a mild jump from 16.4 in 2022 and even a decrease from 16.7 in 2021. 

For Claymont, the culprit has already been identified: highways.

Interstates I-495 and I-95 run through it, spewing so much air pollution that a one-time spike barely registered. 

Regardless of their source, clouds of PM2.5 are just the right size to stick in your lungs and infiltrate the bloodstream, making them particularly worrisome from a public health perspective.

Adrian, Michigan, fifth most polluted city in the US in 2023, was only a little worse off that year than the one before.

According to the WHO, outdoor air pollution is estimated to cause over 4 million premature deaths worldwide annually.

Being exposed to high levels of particulate matter, even over relatively short periods of 24 hours, can be harmful, according to the California Air Resources Board.

These aerosols can contribute to respiratory diseases like 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 US ranked favorably in a 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 the air in Montana.

So for anyone looking for the least-polluted air, here are the rankings from IQAir's data:

1. Makawao, Hawaii
2. Telluride, Colorado
3. Tulalip, Washington
4. Homer, Alaska
5. Waimea, Hawaii
6. Koloa, Hawaii
7. Kihei, Hawaii
8. Bayfield, Colorado

Sharp readers will see a pattern.