Denver area again misses deadline to meet EPA air-quality standards

Nine-county region fails to achieve health limits for ozone pollution set in 2008

By: - July 21, 2021 5:00 am

A view of downtown Denver looking southwest in the late afternoon of July 20, 2021. (Colorado Department of Public Health and Environment)

Spurred by the federal Clean Air Act, Colorado regulators are weighing a range of new pollution-fighting measures to reduce the Denver metro area’s long-running ozone problem — but for the second summer in a row, things are getting worse, not better.

“The smoke alarm in Colorado is going off, and we need to put out the fire,” said Danny Katz, executive director of the Colorado Public Interest Research Group. “Ozone pollution is a public health hazard, and it can damage our lungs (and) contribute to asthma, among many other ailments.”


Air quality in and around Denver reached unhealthy levels yet again on Tuesday, as the latest in a long line of federally-imposed deadlines came and went without the region “attaining” the health-based ozone limits set by the Environmental Protection Agency more than a decade ago.

A nine-county area known as the Denver Metro/North Front Range Nonattainment Area has repeatedly failed to achieve the EPA’s 2008 National Ambient Air Quality Standards for ozone, which set the limit at an 8-hour average of 75 parts per billion. The chronic noncompliance has led to a series of downgrades under the Clean Air Act, the latest of which came in December 2019, classifying the region as a “serious” violator of clean-air laws and giving it until July 20, 2021, to shape up.

Though it will be a while before the findings are official, preliminary data show that Colorado is set to fall well short of the EPA’s ozone standard. Nearly everyone, including state officials, expects the agency to soon downgrade the region again, this time to “severe” nonattainment, triggering a range of new pollution control measures that will have to be enacted by the Colorado Department of Public Health and Environment.

In the meantime, Coloradans will continue to suffer health impacts from ozone pollution that appears — amid a summer of historic heat waves and devastating wildfires across the West — to be trending in the wrong direction.

Preliminary data released through the EPA’s AirNow service show that many monitoring stations across the Denver area have recorded more high ozone days in 2021 than in 2020. Tuesday marked the 16th consecutive day on which CDPHE issued an air quality alert for the region, warning that “people with heart or lung disease, older adults, and children, should avoid prolonged or heavy outdoor exertion.”

“We’ll have a clearer sense of what the data says about our current ozone season soon,” Andrew Bare, a spokesperson for CDPHE’s Air Pollution Control Division, said in a statement. “Long-term trends show a decline in ozone values, and it’s too early to tell whether the high readings seen last year and during the beginning of this summer reflect a change in that trend or are just part of the variability that we see from year to year.”

Ozone-forming pollutants come from a variety of sources, with tailpipe emissions from cars and trucks and industrial emissions, particularly from Colorado’s large oil and gas sector, known to be two of the major local pollution sources in the Denver metro area.

“We have some ambitious rulemakings scheduled for the near future, including a proposal to reduce emissions of all sorts from the oil and gas sector and revisions to the State Implementation Plan,” Bare said. “We’re monitoring the data closely and not delaying on taking steps to reduce ozone.”

On Tuesday afternoon, however, CDPHE announced that it was suspending a proposal to require large businesses in the nonattainment area to incentivize employees to reduce car travel, as part of an effort to reduce emissions of both ozone-forming pollutants and heat-trapping greenhouse gases. The state’s Air Quality Control Commission will instead move forward with a dramatically revised rule that would only direct employers to collect data through employee surveys.

Katz said he was “extremely disappointed” by the decision, and he called on state officials to continue moving forward with other regulatory efforts, including the AQCC’s oil and gas rulemaking and an effort by the Colorado Department of Transportation to incorporate pollution standards into long-term transportation planning.

Denver’s overall level of air pollution has declined since the notorious days of the city’s “brown cloud” in the 1980s, and ozone levels have declined slightly over the last two decades. But the nonattainment area remains well above the 2008 ozone standard, and even farther above the revised standard of 70 ppb that the EPA set in 2015. Other countries have set health limits that are even lower, with the World Health Organization recommending a standard of roughly 50 ppb, and scientists say that no level of air pollution is known to be safe.

“We’ve learned, just over the past decade, that the impacts of ozone are actually much broader than we realized,” said Dr. James Crooks, an environmental health researcher with National Jewish Health. “The more that scientists have studied ozone’s health effects, the worse they look, and the broader they look.”

“It’s unfortunate that we have missed this deadline yet again,” said Katz. “But I think we have the tools, we have the means, and we just need to get out there and do it. I’m hoping to see that happen in the next six months.”


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Chase Woodruff
Chase Woodruff

Chase Woodruff is a senior reporter for Colorado Newsline. His beats include the environment, money in politics, and the economy.