In its annual ‘State of the Air’ report for 2016, the American Lung Association reports that despite the continued improvement in air quality, there are still over 166 million Americans at risk of averse health effects on account of unhealthy air throughout the country.

There are still nearly 20 million people in the United States that live with unhealthful levels of all three measures of air pollution the report tracks: ozone, short-term and year-round particle pollution

These are the top 10 U.S. cities most polluted by short-term particle pollution:

  1. Bakersfield, California
  2. Fresno-Madera, California
  3. Visalia-Porterville-Hanford, California
  4. Modesto-Merced, California
  5. Fairbanks, Alaska
  6. Salt Lake City-Provo-Orem, Utah
  7. Logan, Utah
  8. San Jose-San Francisco-Oakland, California
  9. Los Angeles-Long Beach, California
  10. Missoula, Montana

Perhaps somewhat surprisingly, none of the most polluted cities in America are anywhere near big cities. Rather, a majority of them fall in California’s Central Valley, which is an agricultural region that, because of its geographical makeup, often traps all of the pollutants that float over the city.

Source: American Lung Association