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Smog from forest fires in northern Alberta obscures areas of downtown Denver May 22, 2023. The Canadian smoke added to Denver's existing ozone problems and created high pollution warning days for the Front Range. (Olivia Sun, The Colorado Sun via Report for America)

Colorado’s Front Range has already recorded violations of federal ozone caps for 2023 that put the state into the “serious”pollution infraction category, and regulators should voluntarily call for EPA sanctions in order to speed up health-protecting fixes, environmental watchdogs said. 

Readings at public ozone monitors show that the nine-county Front Range nonattainment area, already under EPA jurisdiction for past violations, has blown past the numbers that will trigger the EPA to move Colorado from the “moderate” to “severe” category for breaching 2015 standards. Admitting it now would speed up EPA-mandated corrections such as tighter controls on oil and gas drilling and other pollution permits, clean air advocates said. 

Other major U.S. cities that were in similar ozone violations have since come into compliance and been declared in attainment of the tighter 2015 standard, said Robert Ukeiley, a Denver air pollution attorney with the Center for Biological Diversity. 

“It’s pretty sad when Denver is more polluted than places like Detroit, Pittsburgh, Cincinnati and Atlanta, all to protect the short-term profits of the big oil companies which make up a very small percentage of Colorado’s economy,” Ukeiley said. 

Colorado air pollution regulators responded they are “evaluating” the idea of asking the EPA for a voluntary reclassification before the federal agency’s rules require a reevaluation of nonattainment in 2024. 

Meanwhile, said Air Pollution Control Division spokesperson Leah Schleifer, “we aren’t waiting for a potential U.S. EPA reclassification as we move forward with actions to reduce ground-level ozone pollution. Colorado is taking bold and meaningful steps right now.” 

Those steps, the division said, include acting on Gov. Jared Polis’ recent directive to reduce nitrogen oxide releases from oil and gas production, and implementing new clean truck and car rules to speed replacement of fossil fuels with lower emissions electric motors. 

Those assurances are not meaningful, Ukeiley responded, after years of the division and the Air Quality Control Commission moving slowly on new pollution rules and delaying EPA enforcement. The EPA has repeatedly downgraded the northern Front Range ozone problem under both 2008 caps of 75 parts per billion and the tighter 2015 cap of 70 parts per billion. 

“As a general rule, reasonable people don’t believe a six-time loser when they say they are trying really hard not to fail a seventh time,” Ukeiley said. “If they were actually working hard to protect air quality for all Coloradans, they would have already submitted their voluntary downgrade request to EPA.” 

The EPA uses three-year averaging in evaluating whether a pollution-troubled area is getting better or worse in attainment of the agency’s ambient air standards. Ground-level ozone is a threat to lung and heart health, and some scientists are recommending a further tightening of the standards below the 2015 cap of 70 ppb. 

Ozone is caused by a combination of nitrogen oxides, volatile organic compounds, intense summer sunshine, wildfire smoke and other factors, including natural background sources and industrial pollution drifting from out of state.

Regulators disregard the highest readings and set their sights on benchmarks such as the fourth-highest readings of the year in order to throw out anomalies. To avoid a downgrade in the current three-year cycle of 2021-23, Colorado monitors would have had to stay below the upper 40s in parts per billion in 2023. Readings at key monitors spiked to 89 ppb in 2021, and 78 ppb in 2022.

The relevant readings at a monitor near Chatfield Reservoir reached 70 by late May of this year, and 67 at the National Renewable Energy Lab in Golden. Those put the three-year averages at 79 at Chatfield, for example, and 77 at NREL, the Center for Biological Diversity said. 

State regulators do not dispute those calculations. The health department “takes ground-level ozone pollution seriously,” Schleifer said, in a written statement. 

One of the primary impacts of a downgrade in the attainment classification is a broadening of pollution sources that must go through the state permitting process. Regulators can demand changes in process or equipment that could reduce pollution before issuing a permit, and permits can ratchet down allowed pollution over time. 

In 2022, the EPA downgraded the nine-county area under the looser 2008 ozone standard from “serious” to “severe.” The federal agency said at the time that under “severe,” requirements include the use of reformulated gasoline in summer months and a reduction of the threshold requiring control measures on emissions sources from 50 tons per year to 25 tons per year. 

Each reclassification puts another strain on state regulation as well. Colorado officials said at the time of the “severe” reclassification it would require for 473 more sources of pollution that contribute to ozone, as the threshold dropped to include all those emitting 25 tons or more. 

Recent legal actions by environmental groups forced the addition of pollution sources in northern Weld County, home to much of the oil and gas drilling and production activity in Colorado, to the Front Range nonattainment area. Previously, only the southern portion of Weld County was included in the stricter permitting regime. 

Taking action now would put far more northern Weld County operations under the “serious” 2015 standards. After asking the EPA for another downgrade, Colorado could take other actions such as demanding a “pause” to oil and gas operations on bad air days, much as the state asks individuals to limit driving, get car emissions tests, or avoid outdoor activity, Ukeiley said. The state could also limit the use of the natural gas-fired Cherokee Generating Station north of downtown Denver on high pollution days. 

Colorado officials often argue against swift air pollution action by saying it can take corporations a long time to acquire and install new equipment. Admitting to another ozone downgrade now rather than waiting would give those officials and companies longer lead time to make changes, Ukeiley said. 

“We know it’s all inevitable that we’re going to get downgraded,” he said. “The state might as well admit that and move forward with the process. And use the process to come up with the most protective effective measures to reduce our pollution.” 

Michael Booth is The Sun’s environment writer, and co-author of The Sun’s weekly climate and health newsletter The Temperature. He and John Ingold host the weekly Sun-Up podcast on The Temperature topics every Thursday. He is co-author with...