More than 125 million metric tons of hazardous and heat-trapping gases pollute Colorado’s air every year, hurting public health and accelerating warming of the planet at a time when world leaders are trying to clean up the atmosphere and fight climate change.

While that’s relatively little compared with larger states such as Texas or California, or total global emissions, Colorado officials under Gov. Jared Polis told The Denver Post this level of air pollution — the equivalent of about 4 tons per second — must not continue.

A Post review of federal and state data found Colorado has been one of 15 states where, due in part to the oil and gas boom, pollution increased after 2005 before leveling off around 2016, reversing previous progress.

“We know we need to reduce emissions to protect public health and the environment,” said Jill Hunsaker Ryan, director of the Colorado Department of Public Health and the Environment.

This air pollution that people in Colorado inhale each day comes from myriad sources: factories, cars, buildings and homes, fossil fuel facilities, cattle feedlots. The Post reviewed data and interviewed officials to find the major polluters and reveal relative contributions as state leaders aim again with a new sense of urgency to clean the air.

Some utilities, including Xcel Energy and the Tri-State Generation and Transmission Association, have committed to closing coal-burning power-plant units in Colorado sooner than once planned.

“We continue to add more solar and wind generation to our system,” Xcel spokeswoman Michelle Aguayo said. Two of three units at the coal-fired Comanche power plant east of Pueblo, Colorado’s single biggest industrial polluter, will be shut down by 2025, she said.

“These are all positive steps. And we know there’s more to be done.”

Greenhouse gases that force climate change — carbon dioxide, nitrous oxide, methane, chlorofluorcarbons, hydrofluorocarbons — make up the bulk of Colorado’s 125 million tons of air pollution each year.

Federal records show that 46 million tons, or 36% of the total, comes from 119 large industrial polluters, including 35 power plants. More than half the electricity in Colorado still comes from burning coal despite a decade of state efforts to spur a shift to clean energy.

There’s no current state limit on greenhouse gas pollution. Companies emitting more than 25,000 tons a year are required, under federal law, to measure and report what they release into the atmosphere.

The U.S. Supreme Court in 2007 ruled that the Environmental Protection Agency has the power to regulate greenhouse pollution that hurts human health, but agency officials haven’t used that power to set limits. However, Colorado health officials recently began taking action after lawmakers in 2019 set targets, ordering greenhouse pollution reductions to cut the 125 million tons down to 62 million tons by 2030 and 13 million tons by 2050.

Colorado’s big polluters

The top 20 greenhouse gas polluters in Colorado include Xcel Energy’s Comanche, Craig, Pawnee, Hayden, Cherokee and Fort St. Vrain power plants, along with a mix of other industrial sources such as the Swiss-owned Holcim cement factory near Florence and the Canadian-owned Suncor Energy oil refinery north of Denver, EPA records show.

Colorado polluters also emit hazardous chemicals including air toxics that cause cancer and serious health problems, including thousands of tons of sulfur dioxide, benzene, hydrogen cyanide, nitric oxide, perchloroethylene and others. They emit tens of thousands of tons of particulates, which cause heart and lung problems.

And records show Colorado polluters emit more than 200,000 tons of nitrogen oxides and volatile organic compounds, or VOCs. These VOCs and nitrogen oxides bake in sunlight and form the ground-level ozone for which Colorado now ranks among the nation’s worst violators of federal air quality health standards.

For companies that emit hazardous chemicals, state health officials issue permits allowing this pollution up to a certain level. Inspectors say they use the permits as a basis for enforcement. The state pollution permits allow 130,670 tons a year of VOCs and 63,145 tons of nitrogen oxides in an eight-county Front Range area where air quality violates federal health standards, the Post found. (Data wasn’t available to determine total permitted emissions statewide.)

The top 20 VOCs polluters emit 5,376 tons a year and the top 20 nitrogen oxides polluters emit 12,145 tons, state records show. This pollution causes respiratory problems, headaches and nausea, and irritates the eyes and throat. VOCs also damage the liver, kidneys and central nervous system.

The biggest VOCs polluters include the crude oil pipeline company Plains Marketing (696 tons), with a base in Denver, and the Suncor oil refinery (590 tons), records show.

The biggest nitrogen oxides polluters include power plants, topped by the Tri-State facility in Craig (6,677 tons) and Colorado Springs’ Martin Drake plant (1,293 tons), along with multiple oil and gas industry polluters and others, including Vail Resorts’ Keystone ski area.

Effects of fossil fuels

Fossil fuels producers in Colorado — the expanding oil and gas industry that runs more than 53,000 wells around the state along with processing facilities, storage and pipelines — have emerged collectively as a major polluter, emitting about 15.6 million tons a year, state records show.

Oil and gas companies release 45% of total VOCs emissions, 22% of nitrogen oxides emissions and 12% of greenhouse gas emissions, the records show. (Industry lobbyists tout site-by-site clean-ups, but state officials say improvements were offset by the industry’s expansion so that only VOCs decreased slightly and nitrogen oxides slightly increased.)

Colorado Oil and Gas Association spokesman Scott Prestige didn’t dispute those volumes and shares, but emphasized industry improvements. “Oil and gas industry emissions have been going down, and they will continue to turn downward,” he said.

After the 46 million tons generated by industry, the second-largest portion of Colorado air pollution, exceeding 31 million tons a year, comes from people driving vehicles that burn fossil fuels. Government policy that favored gas-powered transport has allowed this pollution, which in recent years increased as Colorado’s population growth and a development boom brought more vehicles traveling more miles on more roads.

Burning fuel to heat homes and buildings, along with agriculture emissions from livestock and machinery, add much of the rest of Colorado’s air pollution, according to state data and breakdowns. Colorado joined 14 other states — North Dakota, Montana, Iowa, Nebraska, Missouri, South Dakota, Wyoming, Arkansas, Texas, Minnesota, Mississippi, Utah, Idaho and Oklahoma — where EPA data show increased overall emissions from 2005 through 2014.

Colorado officials’ latest inventory shows overall air pollution peaking around 132 million tons before closures of coal-fired power generators led to a leveling and slight decline of overall pollution after 2017 to about 125.7 million tons a year at present.

Health impacts and a warming planet

Medical researchers are discovering wider impacts of air pollution and possible links to dementia.

Bad air hurts more people than previously believed, beyond the “sensitive” groups such as children, the elderly and asthma sufferers, National Jewish Health researchers in Denver have concluded.

“Environmental pollution is affecting all of us. The more we research it, the more we see ill health effects — negative consequences from exposure to toxic chemicals,” said Dr. Lisa Cicutto, a National Jewish medical professor who conducts air quality studies in communities.

Colorado air pollution at current levels “is priming us so that we are more susceptible to infections,” Cicutto said. These include sinus and bronchial inflammations.

But the Colorado contribution to global warming remains proportional. The United Nations-backed Intergovernmental Panel on Climate Change estimates nations worldwide emit tens of billions of tons a year of greenhouse gas pollution, which is driving the potentially catastrophic buildup of heat-trapping gases in the atmosphere that governments worldwide — minus the United States — collectively are racing to contain.

The global average atmospheric concentration of carbon dioxide, responsible for 80% of global warming, has hit 407 parts per million, higher than at any point in at least the past 800,000 years, according to federal scientists at the National Oceanic and Atmospheric Administration. The rate of increase over the past 60 years has been 100 times faster than previous natural increases such as those that occurred at the end of the last ice age 11,000 to 17,000 years ago. Oceans have absorbed enough carbon dioxide to increase acidity by 30%.

Inside the United States, total annual greenhouse gas emissions exceed 6.6 billion tons, federal data show. Colorado’s 125 million tons amounts to less than 2% of that total. Larger states with more people and heavy industry, including Texas, California, Pennsylvania, Illinois, Ohio and Florida, put out the most air pollution.

Taking action

Colorado officials say they’re increasingly uncomfortable with their permits and broader policies that allow pollution at current levels.

“We do face an urgent need to address the climate crisis,” state environmental programs director John Putnam told state air quality control commissioners in a recent hearing.

Beyond cleaning Colorado air, state officials say they want to spur cleanups in other states and countries. Federal efforts to help tackle global warming have atrophied, state officials said, as President Donald Trump rolls back environmental defenses and pulls the nation out of the international Paris agreement to reduce air pollution.

State-level action in Colorado, if effective, could become a model for quickly reducing those tens of billions of tons emitted worldwide, Putnam said in an email. “We take seriously our obligation to minimize greenhouse gas emissions, and we are moving aggressively on multiple fronts to achieve these goals,” he said.

“We know that Colorado is just one state in one country, but we intend for Colorado to stand at the forefront of a coordinated national and global response. We’re confident we can and must be a leader for other states and nations as they learn from our innovative solutions to this extraordinary threat. Many other states are looking to Colorado’s leadership for models they can apply.”

This year, Colorado health officials are promising the most active agenda in the state’s history of trying to reduce air pollution.

State air quality control officials are implementing new rules aimed at minimizing harm from the oil and gas industry, the largest source of VOCs pollution, Putnam said. State air commissioners also stepped up efforts to make more zero-emission electric vehicles available to drivers. Automobile makers have embraced the production of electric vehicles and Colorado’s new rule requires them to offer more in the state. Prices remains as high as $60,000 and federal tax incentives for consumers are shrinking under Trump.

Colorado health officials recently established a climate team to focus on reducing air pollution.

Their emerging strategy includes tightening limits in permits issued to industrial polluters who emit methane and other gases. They say they also will negotiate more shut-downs of power plants, such as the Martin Drake facility in Colorado Springs. They’re exploring incentives for residents willing to replace gas-fired furnaces with heat pumps. And health officials plan to work with state transportation and regional planning groups to reduce the use of vehicles by investing in transit systems that include more buses and trains.

“We need to have a full suite of tools. Everything is on the table now,” Putnam said. “What are the things that will move the needle in the most cost-effective way?”

An industry response

Some industrial polluters are starting to respond.

At the Holcim cement factory, state air quality inspectors visit often to assess compliance with permitted limits for non-greenhouse gas pollution, company officials said in a recent interview. But state officials haven’t asked for reductions. This plant produces cement for use around Colorado and neighboring states, emitting more than 900,000 tons a year of greenhouse gases, state and federal records show.

Holcim officials say they’re taking voluntary action to reduce carbon dioxide and other emissions.

“We do have great state of the art technology at the plant for everything we emit into the atmosphere, and we’re exploring alternative fuels as a way to reduce emissions and to use less coal. That would reduce our levels of carbon dioxide,” Holcim’s senior manager for environmental compliance Derrick Dease said.

“We also are exploring producing low-carbon cement. These are things we are looking at doing on our own. The state has not come to us and said, ‘We want you to reduce your greenhouse gas emissions,’ ” Dease said.

Colorado utilities still rely on burning coal for more than half the electricity they provide statewide, federal Energy Information Administration statistics show.

However, Tri-State Generation and Transmission officials announced this month that they’ll close a power plant and coal mine in northwestern Colorado ahead of schedule. And another major utility, Minnesota-based Xcel, has shifted toward greater use of renewable wind and solar power, relying on coal for 39% of the electricity Xcel provides.

Xcel is committed to creating a cleaner system for producing electricity in Colorado, aiming to supply electricity without emitting carbon dioxide by 2050, company spokeswoman Aguayo said in an emailed response to Post queries.

“We will continue to work in partnership with our communities and the state to make sure we reach those goals while continuing to provide reliable, safe and affordable energy to our customers.”