Colorado Air Pollution and Wildfires Threaten Access to the Outdoors : Colorado has some of the worst ozone pollution of anywhere in the US. In 2019, the Environmental Protection Agency reclassified the Denver area as a "serious" violator of federal air quality standards. The agency gave the state until July of this year to get the ozone pollution under control, but that deadline came and went. Ozone is a naturally occurring and man-made gas found in Earth's atmosphere. High-altitude ozone, like that found in the ozone layer, protects the planet by absorbing UV rays from the sun. Ground-level ozone, on the other hand, is emitted by things like cars, chemical plants, and oil and gas refineries, and enters the air we breathe. Flocke said ozone pollution is "mainly a product of our own doing," calling transportation of people and goods and the oil and gas industry the "elephants in the room" when it comes to cutting ozone emissions. A 2019 study co-aut...