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Traffic in downtown Denver on Oct. 30, 2018. (Eric Lubbers, The Colorado Sun)

Air quality in Denver and the northern Front Range worsened over the summer and the region missed an extended deadline to meet federal health standards, according to monitoring results by the state’s Air Pollution Control Division.

That’s bad news for Coloradans suffering from asthma and lung diseases, or young children whose lungs are still developing. The U.S. Environmental Protection Agency is expected to downgrade the Front Range region’s ozone to “serious,” which means stricter regulations will be imposed.

The nine-county region spanning from south of Denver nearly to the Wyoming border is not giving up on meeting the decade-old ozone standard, said Mike Silverstein, executive director of the Regional Air Quality Council, the air-quality planning agency for the Denver metro area.

“We thought we were getting close because during 2017, all our monitors were in compliance. But this summer, 2018, we blew it,” Silverstein said. “It was really the meteorology. It was much warmer this summer. We can’t control the weather. We can’t control where we live. But we have to meet these standards because it’s a human health issue.”

There are many reasons why emissions continue to rise even as the state tries to curb them. The ozone standard has become more difficult to meet along the Front Range because of the growing population and the cars that came with the newcomers.

The mountains also can trap greenhouse gases along the Front Range. And there’s pollution coming from outside the state, from more polluted areas like California and China.

Forest fires contribute particulates to the haze that makes us literally see pollution, but that’s a different air quality standard.

The harsh reality for many outdoors-loving Front Range residents is that Colorado not only flunked the EPA standard set in 2015, but the state never met the older, less-strict standard from 2008. Everywhere else in the state, by the way, is doing just fine and in compliance, according to EPA records.

Left: Downtown Denver on July 10, 2018 at 1 p.m., a day when the Front Range was under an Ozone Action Day alert and the mountains were difficult to see. Those with health conditions were advised to stay indoors. Right: Downtown Denver on Oct. 17, 2018 at 1 p.m., a day with no air pollution advisories and good air quality. (Provided by Colorado Department of Public Health and Environment)

All those trapped gases take a toll on people’s health, especially if they have lung diseases, such as asthma. The EPA says if it is met, the latest National Ambient Air Quality Standard will cut down on asthma attacks, premature deaths and missed work or school days. The EPA estimates the public health benefits will save between $2.9 billion to $5.9 billion a year by 2025.

Of course, there’s good ozone and bad ozone. The good one is the natural stratospheric layer of gases that protect Earth from the sun’s harmful ultraviolet rays. But closer to the ground, gaseous emissions from cars, chemical plants and other sources release volatile organic compounds and oxides of nitrogen that mix with sunlight to create O3, a gas with three atoms of oxygen. O3 is unhealthy for humans to breathe.

What does it mean to be out of compliance? The newest EPA standard limits ozone pollution to no more than 70 parts per billion.

Some “nonattainment” days along the Front Range during the summer were in the mid- to high-80s ppb. The EPA allows areas to exclude the most extreme days when they calculate attainment. Even so, some Front Range locations had ozone pollution averages in the high-70s, including monitors at Rocky Flats, Chatfield State Park, west Fort Collins and the National Renewable Energy Laboratory near Golden. Only the station in Welby hit the attainable 69 when no days were excluded.

Healthwise, smoggy days can make your eyes burn and make it harder to breathe. Lung function can be reduced 10 to 15 percent, said Jonathan M. Samet, dean of the Colorado School of Public Health at the University of Colorado, Denver.

“I came here after nine years in L.A., where smog was invented,” Samet said. “There are so many days there where your eyes burn or your throat burns. It’s not like it used to be, but it’s the same in Denver, where there were some days this summer you could see it and smell it.”

Samet, who served as chair of the EPA’s Clean Air Scientific Advisory Committee during the Obama administration, said the EPA regularly examines new studies to set public health standards. He added that the agency is supposed to consider only public health impact and not financial cost to implement a new standard.

“If nature works so that when you got below 80 and there were no adverse health effects, that would be great. You (then) set a standard at 75. But at 75, some people are still affected. So what would happen at 70,” said Samet, explaining the thinking behind new EPA air quality standards. “Everybody deserves the protection required under the Clean Air Act. … We’ve made a lot of progress in the nation, Colorado and Los Angeles. But we’re never going to get to zero risk for air pollution. But certainly, we are doing a lot better than we were.”

MORE: Check out an interactive map of air quality monitors in the U.S.

The amount of ozone pollution allowed has steadily declined. In the 1980s, the EPA allowed 120 parts per billion and then dropped it to 80 ppb in 1997. The 2008 standard lowered the amount to 75 ppb. Today, the rule from 2015 limits ozone pollution to 70 ppb.

But as with any health issue, some people are more sensitive to ozone pollution than others.

“The answer may be that if you’re one of the people susceptible, you may notice,” Samet said.

The state has worked to curb greenhouse gas emissions in the oil and gas industry by mandating increased oil-field inspections, which cut the number of methane leaks by 52 percent in two years ending in 2017.

Colorado also has one of the largest incentives — $5,000 — for people to buy an electric vehicle. It’s also using a large chunk of its VW emissions-cheating settlement to invest in charging stations. A move to join California’s vehicle emissions standard is also in the process after the one Colorado follows is expected to be frozen by the Trump administration.

The EPA is also working with the state to further reduce ozone emissions, said Rich Mylott, an EPA spokesman in Colorado. Potential areas include looking deeper at the oil and gas industries for areas currently unregulated, like venting and well cleanouts; encouraging voluntary changes in the composting and marijuana industries; and exploring emissions from consumer products and architectural coatings.

“EPA is working with the Colorado Department of Public Health and Environment as they continue to take action to reduce ozone along the Front Range. Our focus is on supporting the State as they implement existing air quality programs and identify additional opportunities to reduce emissions,” Mylott said in an email.

There are emissions outside of the state’s control. Conifers give off organic gases that react poorly with human pollution. Pollution from Asia or California or other polluted places outside state borders also contributes a small but measurable amount of greenhouse gases — from 1 to 5 ppbs, Silverstein estimated. The Regional Air Quality Council could ask the EPA to exempt these “international emissions” since it is out of Colorado’s regulatory control.

However, that just helps the region get to the 2008 standard, he said. The bad air is still there. The council is focusing on getting air quality to meet the newest standard instead, or getting ozone pollution below 70 ppb. Plus, there are other urban areas, like Colorado Springs, that meet the new standard.

“We have to make plans to meet both standards. Forget about the administrative requirements. We need to reduce emissions to improve public health, and we are not meeting emission standards,” Silverstein said. “We have less emissions today than five years ago. We need this downward trend to continue. More people moving in, more vehicles travel on our roads, more gasoline is being consumed and more oil and gas wells are going up.

“Getting to 70 by 2020 is very, very remote,” he said. “It’s a recognition of the fact, not a throw up our hands and give up. This motivates us to get to work.”

Consumer tips

  • Aim for fewer car trips. According to the EPA, burning one less gallon of gasoline per week in your vehicle saves 19.6 pounds of carbon dioxide emissions. More:
  • Get alerts when air quality is subpar by signing up for ozone action days email from the Colorado Dept. of Public Health and Environment at
  • Check your travel impact on Colorado’s ozone by using the OzoMeter to see the difference between car, rail, bike or walking. A 20-mile, round-trip commute by rail, for example, reduced greenhouse gases by 6,200 grams, according to the OzoMeter on Oct. 29, 2018. More:

Trade-in programs

Mow Down Pollution — The Denver-based lawn mower exchange program swapped out 453 old gasoline mowers for 521 new electric ones during the summer of 2018. Created by the Regional Air Quality Council, the agency also offers grants to  public agencies and private contractors. More:

Clear The Air Foundation — Donate your old gas-guzzling and fuel inefficient clunker, and the foundation will plant a tree. Formed in 2007 by the Colorado Automobile Dealers Association, the aim is to take “gross emitters” off the road because one old clunker can have as much emissions as 100 newer cars. The foundation has crushed 3,515 cars to date and recycles where it can. More:

PaintCare/GreenSheen — The fumes from paint come from the volatile organic compounds, or VOCs, that help solidify paint but are released into the air as a wall is painted. More manufacturers offer low VOC or no-VOC paints (the latter which can have no more than five grams of VOCs). Partner organizations like PaintCare and GreenSheen help consumers with leftover paint by either reusing it or safely disposing of it. More: or


  • Colorado ozone values report from the Regional Air Quality Council// Link
  • Historical Ozone National Ambient Air Quality Standards (NAAQS), starting with 1971// Link
  • Overview of EPA’s 2015 National Ambient Air Quality Standard// Link
  • History of ozone in Colorado// Link


    Tamara writes about businesses, technology and the local economy for The Colorado Sun. She also writes the "What's Working" column, available as a free newsletter at Contact her at, or or on LinkedIn at in/gadgetress/