Two California cities were ranked among the worst places to live in the U.S. based on air pollution, which probably isn’t surprising to many Golden State residents.

A recent study published by The Guardian shows that the Bakersfield and South Los Angeles areas in California are the top two places with the worst air quality in the U.S.

Bakersfield took the top spot, while the South L.A. area, which includes cities like Compton, Maywood and Paramount, took the second spot.

The report was based on an air quality model researchers at various institutions, such as the University of Washington, developed. Although researchers collected this data from 2011 to 2015, experts say that air pollution patterns usually remain steady and unchanged for years.

Researchers found that the Bakersfield area had the worst air quality in the nation, mainly due to its “unlucky location.”

Air experts told The Guardian that the city is “surrounded by mountains that trap toxic farming chemicals, dust, truck and train fumes and oil-drilling exhaust, as well as pollution blowing south from other parts of the populous state.”

Bakersfield is located in Kern County in Central California, an area that produces the most oil in California and is known for its natural gas production, according to a report.

According to the study, the entire region failed to meet metrics set by the Clean Air Act, a plan to reduce the emission of greenhouse gases, most of the time for the last 25 years.

South L.A. earned its position since the area is riddled with multiple freeway interchanges, railyards and warehouses, The Guardian reported.

The World Health Organization recommends that people shouldn’t be exposed to PM2.5 pollution levels that exceed 5 µg/m3.

PM2.5 particles are invisible to the naked eye but are small enough to travel into someone’s bloodstream and lungs, which could affect their health.

Bakersfield and South Los Angeles exceeded those recommended levels.

California has the worst air pollution in the nation, according to the publication.

These are the top 10 worst cities to live in based on air pollution:

  1. Bakersfield area, California 
  2. South Los Angeles, California 
  3. Chicago’s South and West Sides
  4. Northwest Indiana
  5. Central Indianapolis
  6. Houston, Texas
  7. St. Louis, Missouri
  8. Central Pennsylvania
  9. Central Atlanta, Georgia
  10. Central Birmingham, Alabama