Marga Yuzon
It’s great fun to exercise and hang out in outdoor settings like parks and hiking trails, but being in a natural environment presents many factors beyond our control. Have you ever wondered if you’re breathing fresh air or if there are tiny pollutants you don’t see?
IQAir, a leading air quality monitoring group, reports the most polluted U.S. cities based on annual average PM2.5 concentration (μg/m³). PM2.5 are microscopic particles that can penetrate deep into the lungs and negatively impact health. On the other hand, the Air Quality Index (AQI) is a system developed by government agencies to forecast air pollution levels to the public. The AQI rates air quality from “good” to “hazardous” on a scale of 0 to 500.
According to these analyses, several cities in the U.S. face concerning levels of air pollution. Here are the most polluted cities in America that you should avoid.
1. Coraopolis, Pennsylvania
Coraopolis, Pennsylvania, was reported as the most polluted U.S. city. Its annual average PM2.5 concentration was 19.3 µg/m³, which is 3.9 times higher than the WHO’s recommended limit of 5 µg/m³.
The Air Quality Index (AQI) in Coraopolis currently stands at 57, which is classified as moderate. This means the air quality is generally acceptable but can pose health concerns for individuals with respiratory diseases like asthma.
2. Forest Park, Illinois
Forest Park, Illinois, had the second-worst air quality. Its annual average PM2.5 concentration was 17.6 µg/m³, 3.5 times higher than the WHO’s recommended 5 µg/m³ limit.
Currently, the Air Quality Index (AQI) in Forest Park is 34, classified as good. This means the air quality is generally satisfactory and poses little or no health risk to the general population. However, individuals with respiratory conditions should still be cautious during prolonged outdoor activities.
3. Cave Junction, Oregon
In the IQAir report, Cave Junction in Oregon was in third place for air pollution in the U.S. Its annual average PM2.5 concentration was 17.1 µg/m³, surpassing the WHO’s recommended limit by 3.4 times.
Although Cave Junction’s AQI is 15 (which is considered “good”), there are still high amounts of tiny particles that can irritate your respiratory system. So, if you have sensitive lungs or breathing problems, take it easy on physical activities like running or outdoor climbing.
4. Happy Camp, California
Happy Camp, California, had the fourth-highest air pollution in America. Its annual average PM2.5 concentration was 16.8 µg/m³—over three times the WHO’s safe limit.
The AQI in Happy Camp is a comfortable 23, which means the air quality is good for most people. For folks who wheeze easily, there’s still a bit of a concern. Avoid hiking for long periods as the high PM2.5 levels can mess with your breathing.
5. Adrian, Michigan
Adrian, Michigan, is fifth on the list of U.S. cities with the worst air quality. Its annual average PM2.5 concentration was 16.6 µg/m³, exceeding the WHO’s recommended limit by 3.3 times.
Adrian’s Air Quality Index (AQI) sits at a good score of 22, but there’s a hitch for those with breathing concerns. Even though the air is clean, there are still high levels of PM2.5 floating around. Be mindful not to exert too much if you plan to spend time outdoors in Adrian.
6. Claymont, Delaware
Claymont, Delaware, is #6 on the list of most polluted U.S. cities, with an average PM2.5 concentration of 16.5 µg/m³. That’s more than three times higher than the WHO recommends (they say 5 µg/m³ is the healthy limit).
Claymont’s Air Quality Index (AQI) stands at 51, which falls in the “moderate” zone. This means most people will be fine, but individuals with existing health issues might feel some irritation.
7. Robesonia, Pennsylvania
The seventh most polluted U.S. city is Robesonia, Pennsylvania. On average, for the whole year, its PM2.5 concentration was 16.3 µg/m³, way above the WHO recommendation.
Robesonia’s AQI of 38 may be classified as “good,” but microscopic particles in the air can still harm your airways.
8. Attleboro, Massachusetts
According to the IQAir report, Attleboro, Massachusetts, ranked eighth among the most polluted U.S. cities. Its average PM2.5 concentration was 15.8 µg/m³.
Attleboro’s AQI is a good 42, but people with asthma or similar conditions should still exercise or spend time outside with caution.
9. Elwood, Illinois
Elwood, Illinois, has an average PM2.5 concentration of 15.6 µg/m³ and is ninth on the most polluted U.S. cities list.
Elwood may have a good AQI of 31, but fine particles in the air called PM2.5 can still cause inflammation in your airways. If you have a respiratory concern, try to wear a mask when outdoors or choose indoor activities instead.
10. Huntington, West Virginia
IQAir reports that Huntington, West Virginia, has an average annual PM2.5 concentration of 15.5 µg/m³, which ranks it tenth on the list of the most polluted cities in America.
Its AQI of 16 falls under the “good” category. However, the PM2.5 floating around can still irritate your lungs, especially for those with asthma or similar health problems.
11. Gordonville, Pennsylvania
Gordonville, Pennsylvania, held the eleventh-highest spot on IQAir’s list due to its 15.4 µg/m³ average PM2.5 concentration.
While the high amount of tiny particles in the air might worry you, the city’s overall air quality tells a different story. With a low AQI of 14, ground-level ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide risks are minimal. However, you should still be mindful of the pollution in Gordonville to avoid inhaling PM2.5.
12. Baldwin Park, California
With an average PM2.5 concentration of 15.3 µg/m³, Baldwin Park, California, earned the twelfth spot on the list of the most polluted U.S. cities.
Additionally, Baldwin Park’s AQI of 16 is classified as “moderate,” so you must take caution if you have sensitive lungs and plan to spend a lot of time outdoors.
13. Ridgewood, New Jersey
Ridgewood, New Jersey, was thirteenth in the annual report of America’s most polluted cities. Its annual average PM2.5 concentration was 15.3 µg/m³.
The AQI in Ridgewood is 18, so it falls in the “good” category. But even though the overall air quality may seem fine, it’s important to mask up in public to avoid letting small particles called PM2.5 harm your lungs.
14. McCook, Nebraska
McCook, Nebraska, ranked 14th on the most polluted U.S. cities list. On average, its PM2.5 concentration was 15.2 µg/m³ that year.
The high amount of microscopic particles in the air contrasts its AQI of 31 (a good score). However, if you’re in McCook or plan to visit the city, air pollution remains a concern, as those particles can affect your breathing. It’s a good idea to stay indoors or limit physical activities like hiking, swimming, or running.
15. Peotone, Illinois
Peotone, Illinois, is positioned at #15 on the list of American cities with the highest levels of air pollution. According to the IQAir report, Peotone’s average PM2.5 concentration is 15.1 µg/m³.
The Air Quality Index (AQI) in this city currently stands at 17, classified as good. The air in Peotone is generally clean, but individuals with health concerns such as asthma must exercise caution when outdoors.
16. Woodstock, Illinois
In the report, Woodstock, Illinois, holds the sixteenth-highest spot among cities with high pollution levels. It has an annual average PM2.5 concentration of 15.1 µg/m³, which far exceeds the WHO’s recommended limit of 5 µg/m³
Although Woodstock’s AQI of 14 is considered “good,” fine particles in the can still cause inflammation in your respiratory system. If you have trouble breathing outdoors, be cautious and avoid pushing yourself too hard physically.
17. Cutler, Oregon
IQAir reports that Cutler, Oregon, experiences an average PM2.5 concentration of 14.9 µg/m³, which earns it the seventeenth position on the list of the most polluted cities in America.
With a moderate AQI of 56, people sensitive to air pollution may face health risks. Residents, particularly those prone to respiratory issues, should take it easy on strenuous activities as the air quality can lead to wheezing or other symptoms.
18. Salton City, California
Salton City in California ranked eighteenth among the most polluted U.S. cities, with an average PM2.5 concentration of 14.9 µg/m³. This level is 2.9 times over WHO’s recommended limit.
The AQI in Salton City is 23, so it falls in the “good” zone. However, excessive tiny particles in the air can cause irritation or even chest tightness for those with existing health conditions.
19. Homer, Alaska
Homer, Alaska, has an average PM2.5 concentration of 14.9 µg/m³, exceeding the WHO limit by nearly three times. This places Homer at nineteenth on IQAir’s report.
Despite the city’s “good” AQI of 8, some of the population with respiratory conditions may be prone to coughing fits due to the elevated PM2.5 levels outdoors.
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Marga is a freelance content writer. She creates informative and engaging blog articles about entertainment, travel, and simple living.
Aside from writing, Marga’s background in psychology fuels her work in education and training, where she nurtures her love for lifelong learning.
Find all her published work on Muck Rack.