According to the American Lung Associations State of the Air report for 2023, the city with the worst air quality in the United States is Los Angeles-Long Beach, California. The report ranks cities based on annual particle pollution, annual ozone pollution, and short-term particle pollution. Other cities in Californias Central Valley, such as Bakersfield, Fresno-Madera-Hanford, and Visalia, also rank high on the list. However, according to the World Air Quality Index (AQI) Ranking by IQAir, Houston, Texas is ranked as the 72nd most polluted major city in the world as of September 2023. It is important to note that different reports may use different criteria and measurements to determine air quality rankings.