That crisp, mountain air might not be all it's cracked up to be.

According to The Coloradoanthe U.S. Environmental Protection Agency (EPA) downgraded the air quality of Fort Collins and Denver to 'serious' in a ruling on Monday (December 16).

The cities' ozone statuses were previously labeled as 'moderate'.

This change will bring tough regulations to businesses, and require the state of Colorado to reduce pollution even more.

Governor Jared Polis welcomed the downgrade, stating that he would not sugarcoat Colorado's air problems. Colorado was previously exempt from the downgrade due to claims that pollution was coming in from other states.

Despite this exemption, Denver and other Northern Colorado areas have always had difficulty meeting the EPA's air quality standards.

However, the change does not necessarily means that air quality in Fort Collins is declining. The city's quality has improved over the last decade, save for a rough 2018.

The air quality of West Fort Collins even exceeded government standards this year, while Colorado State University's air quality stayed the same.

Yet, the system for defining air quality is complicated. Based on the three year average of the highest values in an area, it can be hard to understand without prior scientific knowledge.

This complexity is why both Denver and Fort Collins will be receiving 'serious' ratings, despite the seemingly good air quality of Fort Collins.

Now that its status is serious, Colorado will have to come up with a better plan to fight ozone-forming emissions, which can cause smog. Smog, often coming from cars or industrial buildings, can upset those with asthma or other respiratory diseases.

The EPA will give Colorado multiple chances to instigate a new plan as long as the state is visibly working toward improvement.

If the state continues to fail without showing any attempts at improvement, federal highway funding could be affected as a consequence.