EPA downgrade of Denver to ‘severe’ air quality violator would trigger new emissions rules

Failure to meet ozone health standards could mean cleaner, more expensive gasoline, stricter pollution permits

By: - April 13, 2022 10:23 am

Smog shrouds Denver’s skyline behind Interstate 25 traffic on Aug. 18, 2021. (Chase Woodruff/Colorado Newsline)

Big changes to air pollution rules in the Denver metro area could be on their way after the federal government once again flunked the region for its unhealthy ozone levels.

The Environmental Protection Agency on Tuesday formally proposed to reclassify a nine-county region in and around Denver as a “severe” violator of federal air quality standards. It’s the second such downgrade for the area under the Clean Air Act in three years, after a designation of “serious” violations in late 2019, and directly follows one of the Front Range’s smoggiest summers in more than a decade.

“Smog pollution is a serious threat to public health, increasing the likelihood of respiratory infections, asthma attacks, and hospital visits,” EPA Administrator Michael Regan said in a statement. “With these proposed determinations, we are fulfilling our duty under the Clean Air Act to monitor air quality and work with states to help reduce pollution and protect the public we serve.”


Colorado’s Front Range has struggled for years with ground-level ozone, which is known as a “secondary” pollutant, since it forms in the air as a result of chemical reactions between sunlight and certain “precursors” like nitrogen oxides and volatile organic compounds. Those precursors can come from a wide variety of places — including out-of-state sources like Western wildfires and even pollution transported in the upper atmosphere from overseas — but research has shown that on the worst ozone days, local sources of production like gas-powered vehicles, oil and gas facilities and lawn equipment are largely to blame.

The move to “severe nonattainment” under the Clean Air Act could bring with it a host of new regulations aimed at reducing emissions of ozone precursors. That would include a prohibition on the sale of “conventional gasoline,” instead requiring the sale of cleaner-burning — and more expensive — “reformulated” gas. State regulators will also be required to apply more scrutiny to smaller sources of industrial pollution, among other updates to Colorado’s “state implementation plan” for ozone.

The federal government enforces two different health standards for ozone, a 75 parts per billion threshold set in 2008 and a stricter 70 ppb limit enacted in 2015. Scientists say no level of air pollution is known to be safe, and the World Health Organization recommends an even lower ozone health limit of roughly 50 ppb.

Colorado’s air pollution levels have improved somewhat since the days of Denver’s notorious “brown cloud” in the 1980s, but the northern Front Range has struggled to meet even the higher of the EPA’s two ozone health limits. Compliance with those limits is evaluated based on a three-year average of the fourth-highest eight-hour ozone reading in the area, which was recorded at 81 ppb in the Denver area from 2018 to 2020.

After a slight downward trend throughout most of the 2010s, ozone levels spiked again in 2020 and 2021, making the reclassification to “severe” violation inevitable.

In a 2021 Newsline investigation into the state’s Air Pollution Control Division, former staffers faulted the agency for a culture of secrecy and deference to polluters, especially amid a decade-long boom in the state’s oil and gas industry. Amid the worsening smog that blanketed the Front Range last summer, one former employee said, “This is the path that we set ourselves on a decade ago.”

Overall, air pollution is estimated to cause between 90,000 and 360,000 premature deaths in the U.S. annually. A 2019 study by the University of Washington’s Institute for Health Metrics and Evaluation estimated that ambient ozone pollution, specifically, causes more than 12,000 deaths each year in the U.S., including 814 in Colorado.

The EPA will hold a virtual public hearing on the reclassification in the coming months, officials said.

In a press release Tuesday, the Colorado Department of Public Health and Environment said it “welcomed” the EPA’s “shared goal to improve air quality,” touting a range of initiatives aimed at reducing emissions. Combined with the funding and staff increases for the APCD contained in Gov. Jared Polis’ 2022 budget request, the department said, the EPA’s decision means it “will finally have the tools and personnel available to hold polluters accountable.”

“I’m deeply committed to reducing pollution throughout Colorado and particularly for communities that are disproportionately impacted. We have made extraordinary gains in our air quality strategies over the past few years, and now we plan to do even more,” said APCD director Michael Ogletree in a statement. “I came to CDPHE this past November to make a difference, and that’s what I intend to do.”


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Chase Woodruff
Chase Woodruff

Reporter Chase Woodruff covers the environment, the economy and other stories for Colorado Newsline.