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10 U.S. Cities with the Worst Air Quality

Las Vegas has the worst air quality in the U.S.

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By Susan Meyer Info icon
Updated July 23, 2024
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Susan Meyer

Senior Editorial Manager

Susan is a licensed insurance agent and has worked as a writer and editor for over 10 years across a number of industries. She has worked at The Zebr…

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  • Licensed Insurance Agent — Property and Casualty
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Ross Martin

Insurance Writer

Ross joined The Zebra as a writer and researcher in 2019. He specializes in writing insurance content to help shoppers make informed decisions.

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  • 5+ years in the Insurance Industry
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  1. Cities 1 - 3
  2. Cities 4 - 6
  3. Cities 7 - 10
  4. Methodology

The importance of clean air

From pollutants to natural allergens, the quality of the air we breathe has a major impact on health. Air pollution exposure has been linked to a number of diseases, while seasonal allergies can impact breathing, energy levels, and more.[1]

According to the American Lung Association, more than 131 million Americans live in cities that received an F rating for ozone or particle pollution.[2] And more than one quarter of all adults and children in the country suffer from some type of allergy.[3]

But not all areas in the country are subject to the same air quality — which means your quality of life can be impacted by where you live. 

The Zebra set out to find the worst cities for air quality by analyzing the 50 most populous MSAs in the U.S. using three data points:

  • Number of ozone days: When current weather conditions paired with pollution creates harmful levels of ozone.
  • Allergy capital ranking: The Asthma and Allergy Foundation of America's ranking of places where seasonal allergies are challenging. 
  • Number of good air quality days:  A low number of good air quality days means there are more days with an EPA Air Quality Index value between 50 and 200. 

Here are the 10 cities with the worst air quality in the U.S.

#1: Las Vegas, Nevada

With an average of 208 ozone days each year, Las Vegas ranks the second highest out of the cities we analyzed. It also has a fairly low number of good air quality days at just 79 annually. That's 7th on our list of 50. The desert climate in Las Vegas, with high temperatures and minimal precipitation, added to its fast-growing population set the backdrop to the city's unhealthy air quality. Those who suffer from seasonal allergies, however, may find a bit of relief since Las Vegas only ranks 35th on the allergy capital list.

Las Vegas by the numbers

  • Number of ozone days: 208
  • Allergy capital ranking: 35
  • Number of good air days: 79

#2: Riverside, California

Riverside is another area with a large number of ozone days. At 183, that means nearly half of the year is marked by a harmful combination of weather and pollution. A main contributing factor to Riverside's air pollution is high particulate matter air pollution, primarily from diesel truck operations.[4] It's not surprising, then, that the city only averages 67 good air days. On the bright side, seasonal allergies are not very problematic in Riverside.

Riverside by the numbers

  • Number of ozone days: 183
  • Allergy capital ranking: 65
  • Number of good air days: 67

#3: Oklahoma City, Oklahoma

Oklahoma City has slightly better air quality based on pollution and weather. Ozone days reach 129 and there are about 126 good air days annually. Much of Oklahoma City's pollution comes from vehicle emissions and industrial particle pollution.[5] However, those who suffer from seasonal allergies may not enjoy breathing in the air. Oklahoma City ranks 5th as an allergy capital.

Oklahoma City by the numbers

  • Number of ozone days: 129
  • Allergy capital ranking: 5
  • Number of good air days: 126

#4: Orlando, Florida

Orlando has a similar balance between pollution and seasonal allergies. Ozone days are fairly on par with the number of good air quality index days. But the city is ranked 16th for worst allergies. Whether you live in Orlando full time or are headed to Disney, you may need some allergy medicine.

Orlando by the numbers

  • Number of ozone days: 141
  • Allergy capital ranking: 16
  • Number of good air days: 140

#5: Houston, Texas (tied)

You don't have to worry too much about high ozone days in Houston, which only account for about 16% of the year. However, seasonal allergies can be problematic and the number of actual good air days only reaches 46 — likely due to particulate matter.

Houston by the numbers

  • Number of ozone days: 59
  • Allergy capital ranking: 14
  • Number of good air days: 46

#5: San Antonio, Texas (tied)

San Antonio ties its Texas neighbor for fifth place on our list of cities with the worst overall air quality. Its ozone days are nearly twice as high as Houston's. But on the flip side, San Antonio has more than double the number of good air days. In terms of allergies, San Antonio is somewhere in the middle, ranking 24th. 

San Antonio by the numbers

  • Number of ozone days: 108
  • Allergy capital ranking: 24
  • Number of good air days: 108

#7: Memphis, Tennessee

Memphis has a similar balance between good and bad air quality days. Ozone days reach 122 each year, while good air quality days reach 119. The combination of hot weather and the fossil fuel industry leads to particulate pollution.[6] Out of the cities we surveyed, Memphis ranks just slightly below San Antonio in our list of allergy capitals.

Memphis by the numbers

  • Number of ozone days: 122
  • Allergy capital ranking: 26
  • Number of good air days: 119

#8: Phoenix, Arizona

Phoenix has some of the higher levels of low air quality days, but the dry desert air is a boon to people with seasonal allergies. Ozone days account for 57% of the year, while good air days only account for 18%. But Phoenix does have one of the lowest allergy capital rankings on our list.

Phoenix by the numbers

  • Number of ozone days: 208
  • Allergy capital ranking: 95
  • Number of good air days: 66

#9: Dallas, Texas

Dallas appears on our list largely because it has one of the worst allergy capital rankings compared to other areas we reviewed. Good air quality index days are fairly low, only totaling 106 per year. But ozone days only amount to 81.

Dallas by the numbers

  • Number of ozone days: 81
  • Allergy capital ranking: 4
  • Number of good air days: 106

#10: Denver, Colorado

Denver has some of the highest ozone days in the country, coming in at 157 annually. It does, however, have a comparatively high number of good air quality days, which total 119 each year. On top of that, seasonal allergies aren't a major issue at such a high elevation.

Denver by the numbers

  • Number of ozone days: 157
  • Allergy capital ranking: 59
  • Number of good air days: 119

Methodology

The Zebra pulled three data points to analyze the top 50 MSAs (by population) in the U.S. related to air quality. 

  • Number of ozone days (EPA)[6]
  • Allergy capital ranking (Asthma and Allergy Foundation of America)[7]
  • Number of good air quality days (EPA)[8]

MSA data was used where applicable, and we sometimes substituted county data as necessary.

Sources

  1. Air quality, energy and health. [World Health Organization]

  2. Air quality facts. [American Lung Association]

  3. More Than a Quarter of U.S. Adults and Children Have at Least One Allergy. [CDC]

  4. Community Air Quality Project. [UC Riverside]

  5. Air quality in Oklahoma. [Air Quality IQ]

  6. Air data - Ozone exceedances. [EPA]

  7. Allergy capitals. [Asthma and Allergy Foundation of America]

  8. Air data basic information. [EPA]