The Front Range’s summer ozone pollution season begins Sunday and with it comes the annual warnings about being careful when working or playing outdoors on high-pollution days.
A new analysis of where ozone pollution is most intense shows that even escaping to the mountains may not prevent people from breathing dirty air.
In recent years, high ozone levels have been detected at Chatfield State Park, South Table Mountain in Golden, Boulder Reservoir and Rocky Mountain National Park, according to online maps created by the Colorado Public Interest Research Group.
“It makes it clear there’s too much ozone pollution not only where we live and work but where we go to get away,” said Kirsten Schatz, a CoPIRG advocate.
Already this year, the Colorado Department of Public Health and Environment’s Air Pollution Control Division has released two air quality alerts, signifying the potential for heavily polluted air, and exceedances were recorded by Front Range air monitors both days, according to the Regional Air Quality Council’s 8-Hour Ozone Summary.
“The high concentrations of ground-level ozone were enhanced by unseasonably warm and dry weather with afternoon temperatures between 15 and 20 degrees above normal,” said Zachary Aedo, a spokesman for the state health department. “Ozone Action Day Alerts in May are not uncommon for Colorado, with our state averaging between one to two alerts during that month each year.”
On Friday, those air monitors were showing probable impacts from wildfire smoke drifting from Canada. That smoke reached Colorado on Friday morning but was still high enough overhead to minimize any potential health harms, according to the Colorado Smoke Blog. The smoke forecast calls for hazy skies in Colorado through Saturday.
Denver and the northern Front Range are in severe violation of federal air quality standards, and that violation leads to more expensive gasoline in the summer and more regulations for industries. The state has taken steps to try to get the pollution under control, but its progress has been slow.
Last summer, the Front Range recorded more high ozone days than in 2023, putting it behind schedule to meet a critical benchmark in 2027.
Ozone pollution forms on hot, sunny days when nitrogen oxides and volatile organic compounds — created by the burning of fossil fuels — combine and heat up. The mixture forms a brown smog that hovers on the horizon.
Ozone pollution makes people sick, causing asthma attacks, exacerbating chronic obstructive pulmonary disease and contributing to cardiovascular disease. The Denver-Aurora-Greeley area was ranked the sixth-worst region in the country for ozone pollution in the American Lung Association’s 2025 State of the Air report.
“Ozone pollution is bad for us, but it also has cumulative impacts with other pollutants in the air at the same time,” said Dr. Beth Gillespie, a Denver Health physician and chairwoman of Physicians for Social Responsibility Colorado.
Gillespie encouraged people to exercise and participate in outdoor activities in the morning before the sun heats the atmosphere so they can avoid inhaling dangerous chemicals. Children with asthma and adults with chronic lung diseases need to be particularly careful when being outside during the hottest parts of the day.
To help reduce ozone pollution, people are encouraged to walk, ride bicycles or ride public transportation to reduce the emissions that come from cars and trucks. Schatz also asked people to use electric lawn and garden equipment as much as possible and for those with gas-powered equipment to postpone yardwork on the hottest, sunniest days.
“Mowing the lawn just isn’t worth all the pollution in the air on a day when ozone levels already are high,” she said.
To learn what people can do to reduce emissions, visit simplestepsbetterair.org.
To sign up for the state’s daily air quality alerts, visit colorado.gov/airquality/request_alerts.aspx.
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