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23 Most Polluted US Cities

Who has the most polluted air?

Every year the American Lung Association releases its list of the cities with the cleanest air...and the list of the cities with the most polluted air. We've got the list, and we share a few things you can do if your city is not the most pristine.

  • #10: Cleveland-Akron-Canton, OH
  • #9: Pittsburgh-New Castle-Weirton, PA-OH-WV
  • #8: Cincinnati-Wilmington-Maysville, OH-KY-IN
  • #7: San Jose-San Francisco-Oakland, CA
  • #6: El Centro, CA
  • #5: Los Angeles-Long Beach, CA
  • #3: Visalia-Porterville-Hanford, CA
  • #2: Bakersfield, CA
  • #1: Fresno-Madera, CA

Mountains with clean air

What the top cities have in common

The ALA's listis based on two different types of air pollution measurements: Ozone Pollution and Particle Pollution.

Ozone Pollution

Ozone, while incredibly important when high up in the atmosphere, is toxic when breathed in large amounts. Unfortunately, it can be the by-product of a lot of our daily activities, including driving cars with gasoline engines. "High ozone days" occur when the atmospheric conditions are such that ozone is accumulating in your area, causing a health hazard. Factors for high ozone can include the wind patterns and geography of an area, with some cities having air that will "pool" until high winds flush it out of the area. The ALA looked at measures of how many high ozone days a city had, and those with the lowest number scored the best, while those with more scored at the top of this list.

Particle Pollution

Particle pollution is the mixture of very tiny (actually, a wide range from tiny to really, really tiny) particles in the air. These particles can be from liquids or solids and range from coarse at 10 microns to 2.5 microns (often called PM 10 or PM 2.5) all the way down to ultra-fine particles at .1 microns.

The ALA looked at both the number of days that a city had high particle counts as well as a broader view of the particle counts over a year. The year-long average is used in their list of cities with high pollution and is the list we are choosing to highlight. The cities with the worst year-long particle pollution also ranked high the list for most ozone days.

Polluted Air

So, how bad can it be?

You might be wondering just how bad the ozone or particle pollution can be for you. The truth is, they are both extremely hazardous to health, whether in the short or long term.

In the short term, ozone and particle pollution spikes can cause severe symptoms including death, especially among the elderly, the young and those with cardiovascular health issues. While asthma and coughing are obvious connections, not as obvious are the thousands of stroke and heart attack deaths that can be directly attributed to spikes in particle levels, whether the day of a spike or up to two months later.

The long term picture is not much rosier. Long-term exposure to particle or ozone pollution has been demonstrated to cause cancer or death. This has lead to the EPA's declaration that particle pollution poses "serious health effects.”

Panic Button

Uh-oh. We're on the list!

Stay calm. You don't necessarily need to move to experience better air. Here're some simple things you can do.


Being aware is half the battle. is a great resource for you to keep on top of what the air conditions are in your own city. Staying indoors, particularly if you are filtering your air, is a great way to reduce your risks, especially on days when the pollution levels are highest.

Take care of those who can’t take care of themselves

Watch out for those who are at most risk to air pollution, who are the young and the elderly. Monitor the ozone/particle pollution on the days your children go out to play. Keep an eye out for the elderly.

Conserve energy

Attack the problem at its source; start by conserving energy. Climate change and air pollution go hand and hand. Do your part to follow the three R’s: reuse, reduce and recycle. Save energy by turning off lights not in use, investing in energy saving lightbulbs, implementing green energy resources in your home and conserving water.

Take public transportation

Did you know? A single bus carries passengers which are likely to drive 40 cars, according to Conserve Energy Future. Cars and trucks are one of the major sources of air pollution. CEF also reports that during a heavy traffic jam, pollutants outside can seep into your car, making the air inside your car 10 times more polluted than typical city air. You can even find a carpool buddy, walk or bike to work if you don’t enjoy public transportation.

Filter the air

Indoor air can be filtered in a number of different ways. We (of course!) recommend a great air purifier that targets your specific concerns, but you should also pay attention to your furnace and HVAC filters since they are your first line of defense. A few rules of thumb:

  1. Run your air purifier 24/7
  2. Choose a filter that targets your needs
  3. Change the filter regularly

Want to know more? Learn how to Alen is designed around your style.

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