As scientists work to understand high ozone levels on Colorado's Front Range, some may experience breathing difficulties

Colorado's Front Range is looking at several days of high ozone ratings that will aggravate breathing difficulties and lead to warnings and changes in plans. It comes while experts are still working to figure out why Colorado seems unable to make expected progress on reducing dangerously high ozone above the level that the EPA has set as a risk.

"They're making progress, it's just not fast enough and it's really not evident yet," said Laurie Anderson, who serves as a field organizer for the organization Moms Clean Air Force as well as Broomfield's City Council. "We live right close to the Front Range and the mountains and the pollution is everywhere, you can't escape it."

She got more involved after her daughter, a runner, suffered from breathing difficulties.

"Over the course of a couple years of running she developed asthma," said Anderson.

The progress has been a reduction in some of the precursor components of ozone. Emissions rules have drastically cut tailpipe emissions. That has helped. But ozone levels still remain in the danger zone too often for about 60% of Colorado's population living along the northern Front Range.

"We don't fully understand it and that's one of the reasons that we continue research in that area," said Dr. Steve Brown, a research scientist and program lead at the NOAA Chemical Sciences Laboratory in Boulder.

Ozone is created at ground level when chemical reactions between volatile organic compounds (VOCs) in sunlight react with oxides of nitrogen (NOx) that are most often human produced. It is not visible, so the haze residents in the Denver metro area and other parts of the Front Range is not ozone, but wildfire smoke and the pollutants that combine with sunlight to make it.

 Colorado's rough ozone week comes amid word Monday that Colorado will get $328 million to fight climate pollution through programs that include reducing methane emissions.

But making progress on ozone has been more difficult than expected.

"To some extent the sources are well understood, but what's creating ozone today in 2024 is really different from what it was in the past, so we've got a lot to do to really understand why Colorado in particular continues not to meet the ozone standards," said Brown.

Improvements in the levels of pollutants have been made, but Colorado's Front Range still wrestles frustratingly with ozone.

"Because cars are so clean now, we have to worry about these other somewhat smaller sources of air pollutants that now are one of the major contributors to ozone," said Brown. "Things like paints, or inks or coatings, even the deodorant or shampoo you might put on in this morning are things that can release pollutants into the air that ultimately combine other with other components of urban air pollution and cause ozone."

VOCs are volatile organic compounds and so that is a factor as well.

"The major source of VOCs where we're standing is actually the grasses and the trees around us," said Brown as we spoke outside the headquarters of the National Center for Atmospheric Research in Boulder. "There's lots of natural sources that contribute to ozone pollution."

But those VOCs cannot create ozone without the nitrogen oxides that in sunlight help create ozone.

Earlier this month, NOAA used a small aircraft equipped with sensors to attempt to detect the outputs of VOCs and the areas where ozone is pooling. But results and conclusions are still incomplete. Simple explanations like a growing population don't seem to complete the understanding of the imbalance.

"It's probably more than that. Certainly we've seen growth in this area. But other places have seen growth to," said Brown.

Studies will hopefully reveal how different compounds react more to produce ozone and others less.

"We understand in detail how much of it comes from each specific source. That's the part we really don't understand right now. And we especially understand it because things have been changing," said Brown.

For people who live in Colorado for the outdoors, it is a disappointment at least and a threat at most. For Anderson and her family, they simply back off exercise in the mid-days of summer. It just isn't worth the risk.

"It's costing outdoor recreation and it's costing our health," said Anderson.