The U.S. Environmental Protection Agency moved to downgrade the northern Front Range from a “serious” to “severe” violator of federal ozone standards Tuesday, potentially triggering new rules meant to improve local air quality in the region.

The action was widely anticipated after a string of smoggy summers in metro Denver. The new classification affects an area extending into nine counties from Fort Collins to Castle Rock, which has repeatedly missed deadlines to bring levels below the EPA’s 2008 ozone standard of 75 parts per billion. Four other metro regions would also be reclassified as “severe” nonattainment areas under the proposal, including Chicago, Dallas-Fort Worth, Houston and the greater New York City area.

If the proposed downgrade is approved after a public comment period, many more Colorado companies will be forced to obtain and comply with tougher state air pollution permits. Gas stations will also likely be required to sell cleaner-burning fuel during the summer ozone season in 2024, potentially increasing prices, according to local air regulators.

“Ground-level ozone remains one of the most challenging public health concerns we face, affecting large numbers of Coloradans and their families,” said EPA Regional Administrator K.C. Becker. “EPA’s proposed Clean Air Act reclassification for Denver and the northern Front Range will make sure we are leveraging all available measures and resources as we move forward to reduce ozone pollution with the Colorado Department of Public Health and Environment and all our partners.”

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