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U.S. Cities with Worst and Best Air Quality

U.S. Cities with Worst and Best Air Quality

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By David Heacock

While lockdowns during the COVID-19 pandemic have brought about a host of issues, there have been several positive outcomes. In addition to limiting the spread of the virus, the lockdowns have resulted in better air quality due to decreased commercial activity and automobile traffic. However, the lifting of lockdowns and a recent surge of wildfires in Western and Mountain states may quickly reverse this trend, once again exposing millions of Americans to poor air quality.

According to data from the Environmental Protection Agency (EPA), prior to COVID-19, nearly one in four Americans resided in counties with poor air quality. While ozone-related pollutants are the most common cause of poor air quality, many Americans are also exposed to a variety of other common pollutants such as particle pollutants, sulfur dioxide, and lead.

While many Americans are still living in places with unhealthy levels of air pollution, conditions have been improving in recent decades. Through EPA efforts and the passage of the Clean Air Act, the U.S. has seen gradual improvement in air quality and a decline in the emissions of common pollutants since 1970. CO2 emissions have also shown small declines since 2010. Such improvements have occurred even with steady increases in the gross domestic product, travel, total population, and energy consumption.

Still, air quality in many areas, especially in the Western U.S., does not meet national standards. In addition to causing environmental issues, poor air quality can have negative consequences for individual health, which can be particularly detrimental to those already suffering from certain health problems such as asthma and cardiovascular disease. Additionally, new research indicates that economically disadvantaged communities are more likely to face higher levels of pollution. Furthermore, while the US has improved as a whole, the most polluted areas from 1980 are still among the most polluted today.

To identify metropolitan areas with the worst (and best) air quality, researchers from Filterbuy analyzed median Air Quality Index (AQI) values for 2019. These values, published annually by the EPA, are a measure of an area’s air pollution. Higher AQI values indicate that an area experiences higher pollution levels and lower air quality.

For the purpose of this report, only metropolitan areas with at least 500,000 residents were included. Here are the metropolitan areas with the worst (and best) air quality in the nation.

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Metros with the Worst Air Quality

U.S. Cities with Worst and Best Air Quality - Infographics of a Palm Springs at night, featuring city lights and surrounding mountains, reflecting a city that benefits from relatively clear skies but still faces occasional air quality concerns.

Photo Credit: Alamy Stock Photo

1. Riverside-San Bernardino-Ontario, CA

U.S. Cities with Worst and Best Air Quality - Infographics of a the city's growth in a desert environment, where air quality is impacted by both urban development and climatic factors.

Photo Credit: Alamy Stock Photo

2. Phoenix-Mesa-Scottsdale, AZ

U.S. Cities with Worst and Best Air Quality - Infographics of a towering skyscrapers and surrounding hills, a place where poor air quality has historically been a significant challenge

Photo Credit: Alamy Stock Photo

3. Los Angeles-Long Beach-Anaheim, CA

U.S. Cities with Worst and Best Air Quality - Infographics of Fresno’s downtown area bathed in warm golden hour light, a city where agriculture and industrial activities.

Photo Credit: Alamy Stock Photo

4. Bakersfield, CA

U.S. Cities with Worst and Best Air Quality - Infographics of San Diego’s skyline from a residential street, and city’s coastal influence and relatively favorable air quality.

Photo Credit: Alamy Stock Photo

5. San Diego-Carlsbad, CA

U.S. Cities with Worst and Best Air Quality - Infographics of Fresno's downtown area bathed in warm golden hour light, a city where agriculture and industrial activities can sometimes influence air quality

Photo Credit: Alamy Stock Photo

6. Fresno, CA

U.S. Cities with Worst and Best Air Quality - Infographics of clear view of Denver’s downtown, nestled beneath vast skies, reflecting the city’s air quality challenges due to its elevation and urban growth.

Photo Credit: Alamy Stock Photo

7. Denver-Aurora-Lakewood, CO

Pittsburgh’s illuminated skyline at night, seen from a distance, with bridges over the river, suggesting a city where industrial history may impact air quality

Photo Credit: Alamy Stock Photo

8. Pittsburgh, PA

Detroit's downtown with its historic buildings and sunset lighting, representing urban revitalization efforts in a city that often faces challenges with air quality.

Photo Credit: Alamy Stock Photo

9. Detroit-Warren-Dearborn, MI

Chicago's cityscape illuminated at dusk, showcasing tall skyscrapers reflecting in the river, indicating a bustling urban environment with potential air quality concerns.

Photo Credit: Alamy Stock Photo

10. Chicago-Naperville-Elgin, IL-IN-WI

Metros with the Best Air Quality

Methodology & Detailed Findings

The data used in this analysis is from the EPA’s 2019 Air Quality Index Report. The Air Quality Index (AQI) is EPA’s method for reporting daily air quality by location based on National Ambient Air Quality Standards. Higher AQI values correspond to higher levels of pollution and worse air quality. AQI values below 50 are considered good; AQI values between 51 and 100 are considered moderate; and AQI values that exceed 100 are considered unhealthy (at first for sensitive groups and then for everyone as values increase).

To determine the locations with the worst air quality, metropolitan areas were ranked by their respective median AQI values, with high AQI values corresponding to worse air quality. In the event of a tie, the location with the higher maximum AQI value was considered to have worse air quality.

Population data is from the U.S. Census Bureau’s 2018 American Community Survey 1-Year Estimates. Only metropolitan areas with at least 500,000 residents were included in the report.