The Most Polluted Cities in America (And Their Emission Sources)

A Concise Overview

• The three types of air pollution that make it dangerous to breathe are ozone, year-long particle, and short-term particle pollution
• For the most part, cities in West Coast states are the worst offenders, with California frequently ranking in the top 10
• Although levels dropped during the COVID-19 pandemic, air pollution is increasing again

The Clean Air Act of 1970 significantly reduced the amount of air pollution in America, but many areas still struggle. Worldwide pollution dropped during the COVID-19 pandemic, but levels are rising again at a worrying rate.

While vehicle emissions are a top source of dirty air, U.S. wildfires have increased particle pollution on the entire West Coast. Wildfires are so damaging to air quality that most cities with the worst pollution are in the West.

The EPA looks at three types of pollution for air quality — ozone, year-round particle, and short-term particle pollution. Most cities with high levels of one pollution type present elevated levels of other pollution types, though that’s not always true.

Car emissions are rising again despite inflation’s impact on gas. Mixed with more frequent wildfires, the most polluted cities in America are getting worse. Read on to learn which American cities have the dirtiest air, then explore ways to keep yourself safe from pollution. To read more about how inflation impacts gas and car insurance, consider our article here. 

To find affordable car insurance in your area, just enter in your ZIP code into our free online quote tool above.

Top 10 Cities for Ozone Pollution

You’ve probably heard of the ozone layer in Earth’s atmosphere, but ozone pollution is different. 

This pollution type results from hydrocarbons and nitrogen oxide emissions from cars and other sources. These emissions mixed with sunlight can cause coughing, chest tightness, and wheezing. Children, older adults, and people with lung issues are most sensitive to ozone pollution.

Ozone pollution is a massive problem in congested cities, especially in countries like India and China. Although they don’t compare with global pollution offenders, here are the most polluted American cities by ozone level:

• Number 10: Salt Lake City, Utah
• Number 9: Sacramento, California
• Number 8: Houston, Texas
• Number 7: Denver, Colorado
• Number 6: San Diego, California
• Number 5: Phoenix, Arizona
• Number 4: Fresno, California
• Number 3: Visalia, California
• Number 2: Bakersfield, California
• Number 1: Los Angeles, California

You might notice that every city with an ozone pollution problem also has a hotter climate. Ozone requires three things to form: nitrogen oxides or volatile organic compounds, heat, and sunlight. In cities with heavy traffic, sunny climates, and warm temperatures, ozone pollution is inescapable.

Top 10 Cities for Year-Round Particle Pollution

Particle pollution is a broad term describing liquid or solid particles in the air. Particle pollution includes materials like acids, inorganic and organic compounds, metals, soil, dust, soot, and pollen.

All air contains at least low levels of particle pollution. Some particles are large enough to see with the naked eye, while others are so small they can only be detected by a microscope. The cities below have the worst overall year-round particle pollution:

• Number 10: El Centro, California
• Number 9: Chico, California
• Number 8: Phoenix, Arizona
• Number 7: Fairbanks, Alaska
• Number 6: Medford, Oregon
• Number 5: Los Angeles, California
• Number 4: San Francisco, California
• Number 2 (Tied): Visalia, California
• Number 2 (Tied): Fresno, California
• Number 1: Bakersfield, California

As with ozone pollution, many of the worst offenders are in California. California’s colossal population, significant port industry, and mountainous terrain — despite efforts to lower air pollution — make it difficult to keep the air clean.

Top 10 Cities for Short-Term Particle Pollution

When a city sees a sudden spike in particle pollution, it can trigger asthma attacks, halt healthy lung development in children, and even turn fatal. Heavy traffic, industrial pollutants, and wildfires can trigger short-term particle pollution.

Here are the cities experiencing the most spikes in particle pollution, all but one of which are in the West:

• Number 9 (Tied): Visalia, California
• Number 9 (Tied): Yakima, Washington
• Number 8: Los Angeles, California
• Number 7: Sacramento, California
• Number 6: Chico, California
• Number 5: Redding, California
• Number 4: San Francisco, California
• Number 3: Fairbanks, Alaska
• Number 2: Bakersfield, California
• Number 1: Fresno, California

Besides Fairbanks, the cities with the most short-term pollution spikes are due to wildfires. Hotter temperatures and longer droughts have led to bigger wildfires, and experts cited by National Public Radio expect it will only worsen.  

Top 10 Cleanest Cities

The cities with the cleanest air in America tend to have smaller populations and fewer industrial areas. These areas are also less affected by wildfires and weather changes due to climate change. Here are the top 10 cities with the cleanest air:

• Number 10: Sioux Falls, South Dakota
• Number 9: Elmira, New York
• Number 8: Bismarck, North Dakota
• Number 7: Bellingham, Washington
• Number 6: Casper, Wyoming
• Number 5: Bangor, Maine
• Number 4: Lahaina, Hawaii
• Number 3: Honolulu, Hawaii
• Number 2: Wilmington, North Carolina
• Number 1: Cheyenne, Wyoming

Several factors contribute to high air quality, including a smaller population. Fewer people means fewer cars on roads, less energy consumption, and smaller numbers of personal emissions.

Another reason is simple geography. States like Hawaii have plenty of wind and rain to clean the air. Coupled with Hawaii’s small number of industrial centers and population size, it’s no wonder that the Aloha State has such clean air.

You might notice that there’s only one city amongst the cleanest on the West Coast. Wildfires happen everywhere but are mostly a western problem. Although there are exceptions, the further east you go, the better the overall air quality is. To read about how to find cheap car insurance rates in Honolulu, Hawaii, try our article here. 

Tips to Stay Safe in Cities With Low Air Quality

According to National Public Radio, 137 million Americans live in an area with poor air quality. While living in an area with low pollution is best, most people can’t pick up and leave their lives behind to pursue cleaner air.

If you live in a city with heavy air pollution, follow these tips to keep yourself as healthy as possible:

• Check air quality daily. Air pollution reports come with a color code from green for healthy to maroon for hazardous. You’ll know to take extra precautions when the air is less safe.
• Avoid outdoor exercising. Find a way to get your daily exercise indoors on days with high pollution. You should also ensure your kids play inside.
• Get active. Reducing emissions is everyone’s responsibility. From keeping your energy use down to encouraging your children’s school to prohibit school buses from idling, there are plenty of ways for you to get active against air pollution.
• Don’t exercise near traffic. Streets and highways with heavy traffic create high pollution levels up to one-third of a mile away. Always avoid congested areas no matter what the air quality reports say.
• Avoid indoor smoking. Indoor air can be a sanctuary from outside pollution, and you don’t want to ruin it with second-hand smoke.
• Keep your windows and doors closed. Run an air purifier if you have one. Your goal should be to minimize how much dirty air gets into your home.
• Check on sensitive people. People with lung problems, pregnant women, and older adults are more susceptible to air pollution. On particularly bad days, help them stay safe.
• Set your AC to recirculate. Taking precautions against polluted air won’t do much good if your AC unit is sucking it in. Set your unit to recirculate, so it only draws from clean air.
• Stay hydrated. Dirty air can irritate your throat, eyes, skin, and lungs. To help combat the adverse effects, drink plenty of water.

Ultimately, getting away from areas with heavy traffic will help you live a healthier life. There are plenty of other reasons to avoid cities with large populations. Your car insurance rates will be higher, you’re more likely to get in an accident, and vehicle theft rates tend to be higher, as just a few examples. (For more information, read our “15 Cities with the Most Car Theft [Study: Trends & Totals]“).

Keep Yourself Safe From Air Pollution

Low air quality is a problem nearly a third of Americans deal with, whether it’s ozone or particle pollution. While everyone should be careful, people who live in the most polluted cities in the United States should take extra precautions.

Environmental concerns play a massive role in your quality of life. No matter where you live, you should always check local air quality, compare car and home insurance rates to find the best price, and avoid congested roads. If you’re in the market for affordable auto insurance, just enter your ZIP code into our free online quote comparison tool today.