DENVER (KDVR) — Ozone levels are now considered “severe” on Colorado’s Front Range, an area with some of the most ozone-polluted cities in the country.

The area is known as the Denver Metro and Northern Front Range Nonattainment Area and includes nine counties: Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, Jefferson, Larimer and Weld.

The nonattainment area is among five in the country that failed to meet 2008 ozone standards set by the U.S. Environmental Protection Agency. That means more businesses will need to get pollution permits to meet stricter ozone standards. It could also mean more expensive gas for the public.

The American Lung Association ranks pollution around the country each year, including at the county level. Its most recent analysis found that in Colorado, Jefferson County saw 80 high-ozone days from 2018-20, the highest number among Colorado counties that reported data. Other counties in the nonattainment area also saw dozens of days with high ozone levels over the three-year period.

The numbers include days when ozone levels are at orange levels, which means they’re unhealthy for sensitive groups, and red levels, which means they’re unhealthy for everyone. Purple ozone days mean the air quality is very unhealthy, but none were logged during the time period analyzed in the report.

Here’s how the Colorado counties that reported ozone data ranked in the analysis:

  1. Jefferson County: 80
  2. Douglas County: 48
  3. Larimer County: 42
  4. Boulder County: 41
  5. Clear Creek County: 33
  6. Arapahoe County: 32
  7. Garfield County: 18
  8. Denver County: 18
  9. El Paso County: 14
  10. Weld County: 13
  11. Adams County: 11
  12. Gunnison County: 7
  13. Mesa County: 7
  14. La Plata County: 6
  15. Montezuma County: 6
  16. Rio Blanco County: 4
  17. Archuleta County: 0
  18. Delta County: 0

Nationwide, the Denver-Aurora metro ranked seventh among the 25 U.S. cities most polluted by ozone. Fort Collins ranked 18th. Most of the cities on the list are in the Southwest, with nearly a dozen of them in California.

Other metros that the EPA downgraded to “severe” violator status last week are the Dallas-Fort Worth and Houston metros in Texas, the New York City metro area and the Morongo Reservation about 90 miles east of Los Angeles.