On clear days, Patricia Schuba says she can see clouds forming from the stacks at the Labadie Energy Center from her home three miles away.

“They’re dirty clouds,“ Schuba said. ”They don’t look like normal clouds.”

The clouds are emissions from Missouri’s largest coal-fired power plant, located about 45 miles west of St. Louis. Ameren, the investor-owned utility that provides electricity to most of eastern Missouri, owns the Labadie plant.

Every year, it emits more sulfur dioxide and carbon dioxide from burning coal than any other plant in the region. And in 2020, the facility was the second-largest coal-burning producer of those pollutants in the country.

Schuba worries that pollution coming from the Labadie plant affects the air quality in the region. It’s the reason she joined and now leads the Labadie Environmental Organization, which advocates for more pollution controls at the power plant.

“When I look up in the air and see those clouds, I know what that is and other citizens might not know what’s in those clouds,” Schuba said. “That stuff can get into your lungs, it can go into your bloodstream, it can affect your brain and your organs.”

The Labadie plant and several other coal-burning power plants in the Midwest were among the highest polluters of sulfur dioxide, nitrogen oxides and carbon dioxide in 2020. That’s according to EPA data on annual emissions from power generators across the country.

The data tracks how much sulfur dioxide, carbon dioxide and nitrogen oxides are emitted by each power generating facility in the country throughout the year.

None of the plants violate EPA standards, the agency told the Midwest Newsroom.

“We do have facilities that have very high emissions, but that has no bearing on if they are violating or doing anything. That could just mean they’re large facilities," said Jason Heitman, the Emissions Inventory Lead for the EPA’s Region 7, which includes Iowa, Kansas, Missouri and Nebraska.

The Labadie plant was built in 1970 and generates more than 2,300 of Ameren’s 10,500-megawatt capacity. The plant became a focal point of litigation more than a decade ago over how much pollution Ameren’s coal-burning facilities generate yearly. 

In the lawsuit, the EPA alleged the power provider skirted Clean Air Act laws at its Rush Island facility and ordered that Ameren install pollution control at the Labadie Energy Center to counteract the extra pollution produced at Rush Island.

Labadie isn’t alone. The Midwest is home to power plants that are some of the country’s highest emitters of pollutants.

According to EPA data, four of the top 10 coal-burning power plants with the highest sulfur dioxide emissions in the country are located in the four-state region.

What’s more, the data shows two of the power generators that contribute the largest amount of nitrogen oxide emissions in the country are located in Missouri.

Andy Knott is the interim central region director for the Sierra Club’s Beyond Coal Campaign. The group advocates for the replacement of coal-burning power plants with clean energy generation.

“There are more coal plants in the central part of the country than any other region,” Knott said, noting that the four states together make up more than a quarter of the country’s coal-burning generation. “These four states are a major part of the problem.”

Missouri alone produced the second-largest amount of sulfur dioxide of all states, emitting more than 91,000 tons of the gas into the air in 2020. Nebraska was the fourth-highest producer in the country, emitting about 40,000 tons of sulfur dioxide that year.

Sulfur dioxide is a byproduct produced by burning coal. According to the EPA, short-term sulfur dioxide exposures can be linked to respiratory problems like difficulty breathing and increased asthma symptoms.

Short-term exposures have also been linked to increased emergency department visits and hospital admissions for respiratory illnesses. The EPA notes that’s particularly true for at-risk populations like children, older adults and people with asthma.

As a state, Missouri was also the second-highest emitter of nitrogen oxide in the U.S., producing about 51,000 tons of the gas in 2020.

Breathing air with high concentrations of nitrogen oxide can irritate the lungs and heavy exposures over short periods of time can aggravate respiratory diseases, particularly asthma.

Sulfur dioxide, as well as nitrogen oxide, also contribute to acid rain and can form particulate matter, a type of inhaled pollution that can harm the lungs and other parts of the body.

Knott called Missouri a “hotbed” for coal pollution because of the rate that power plants burn coal and the lack of pollution control on many of the region's biggest power plants.

Labadie was the largest producer of sulfur dioxide and carbon dioxide in the region in 2020 and produced the second-highest amount in the country of the pollutant the same year.

The plant produced nearly 40,000 tons of sulfur dioxide in 2020, the second-highest amount of the pollutant produced by any power plant in the country.

The highest producer of sulfur dioxide in the U.S. was the Texas-based Martin Lake Power Plant, which produced about 44,000 tons of sulfur dioxide in 2020.

The Labadie plant also emitted the second highest amount of carbon dioxide in 2020, producing more than 17 million short tons of carbon dioxide. (Short tons are a unit used to measure carbon dioxide emissions).

Alabama’s James H. Miller Jr. Power Plant, generated the highest amount of CO2 in the country in 2020, producing nearly 19 million short tons of the pollutant.

While carbon dioxide emissions have some effects on health, the EPA says its main effect is environmental. Carbon emissions contribute to the formation of greenhouse gases that warm the atmosphere.

Ameren declined a request for an interview about the Labadie Power Plant and its two other power plants that were among the top 10 producers of the three pollutants tracked by the EPA in its report.

Craig Giesmann, Ameren’s senior manager of environmental services, said in a statement that EPA-approved air monitoring data shows the air around Labadie Energy Center meets EPA standards, is clean and is improving there and across the St. Louis area.

He added that Ameren is committed to transitioning its generation fleet to cleaner, more diverse sources.

“Ameren is executing a plan that accelerates the transition toward cleaner energy and targets net-zero carbon emissions by 2050, while meeting our customers' expectations for safe, reliable and affordable energy,” the statement read. “We care a great deal about the environment and embrace our responsibility to be good environmental stewards for our customers and the communities we serve.”

According to Ameren’s annual sustainability report, its sulfur dioxide emission for all of the power supplies is 76% below Missouri’s standard and its nitrogen oxide emissions are 78% below the EPA’s national standard. However, those figures account for the provider’s full fleet of power stations, not individual facilities.

The report also notes Ameren’s sulfur dioxide emissions have decreased 68% since 2005, while nitrogen oxide emissions and carbon dioxide emissions have been reduced by 54% and 31% since 2005, respectively.

Since 2009, the Labadie Environmental Organization has advocated for more pollution control and monitoring at the Labadie facility. In 2019, the group lauded a federal judge’s order for Ameren to install coal scrubbers at the plant, a pollution control mechanism that reduces the amount of sulfur dioxide that is emitted into the air.

The EPA originally filed its lawsuit in 2011, accusing Ameren of violating the Clean Air Act in 2007 and 2010 when it replaced two coal-fired boiler units at its Rush Island plant without seeking a permit. The Sierra Club joined the case as a plaintiff in 2016.

A federal judge ruled in 2019 that Ameren had three years to install coal scrubbers at Rush Island and the Labadie Energy Center, in an effort to “reduce pollution from Labadie in an amount equal to the excess emissions from Rush Island.”

However, in 2021, that order was rescinded by a federal appeals court.

Knott said the lack of pollution controls at the Labadie plant and several other facilities across the region is one of the leading reasons sulfur dioxide emissions are so high in the four-state area.

Knott noted that adding pollution controls to power plants isn’t cheap. In 2010, Ameren spent roughly $600 million installing scrubbers at its Sioux Energy Center in West Alton. He said the cost of installing the scrubbers is a deterrent for utility providers.

Ameren plans to close several of its coal-fired power plants in the next several decades, turning instead to more environmentally friendly power generators. The power provider has said it plans to close the Labadie Power Plant by 2042, after closing the Meramec Energy Center this year and the Rush Island plant in 2024.

For Schuba, of the Labadie Environmental Organization, another 20 years of the nearby plant emitting pollution would be “appalling.”

Missouri is also home to the power plant that emits the highest amount of nitrogen oxides into the air in the country, according to EPA data.

Nitrogen oxide emissions are how the EPA defines the sum total of nitric oxides, nitrogen dioxide and other oxides of nitrogen that are emitted into the air. These gases can contribute to regional haze caused by pollutants and lead to acid rain.

According to the EPA, breathing air with a high concentration of nitrogen dioxide can irritate respiratory systems, particularly high exposures over short periods of time. Longer exposures can contribute to asthma and a potential increase in susceptibility to respiratory infections.

The New Madrid Power Plant in New Madrid County, Missouri emitted the most nitrogen oxides from a power plant in the region and the country in 2020. The plant emitted more than 18,000 tons of nitrogen oxide into the atmosphere, up from about 14,000 tons in 2019.

Thomas Hill Energy Center in central Missouri emitted the second-highest amount of the gas in 2020, producing nearly 13,000 tons of nitrogen dioxide

Associated Electric Cooperative Inc. owns the New Madrid and Thomas Hill Energy power plants. In an emailed statement, the power provider said the two plants are in compliance with EPA air quality standards and provide reliable energy in rural areas.

The statement added that the amount of nitrogen oxides emitted by the plants varies year to year due to the ebb and flow of power plant operations and strategic decisions. The cooperative expects lower nitrogen oxide emissions from the plant in 2021 due to this.

While the Midwest is home to some of the country’s power plants with the highest level of pollutant emissions, many are well below the EPA’s emission standards, including Labadie Power Station and the New Madrid Power Plant.

Heitman, of the EPA, said high amounts of the three pollutants at power facilities throughout the region can be expected due to the number of customers they serve.

“We do have some of the higher emitters nationwide,” said Heitman. A large part of his job is tracking the number of emissions that are produced at power generators throughout the four states.

He said the power plants that produce high amounts of pollutants don’t necessarily violate EPA rules.

Under the Clean Air Act, the EPA sets limits on certain air pollutants through National Ambient Air Quality Standards and dictates how much of each pollutant can be present in the air across the areas of the U.S.

Those standards say how much of any given pollutant can be emitted over an hourly, daily and annual basis, depending on the pollutant.

For instance, sulfur dioxide is primarily limited to emitting large amounts of the pollutant every hour, according to the EPA’s website.

However, Knott argues that the EPA’s air standards aren’t stringent enough to protect people’s health and that power plant owners often skirt the rules. He said that’s partially due to the rules being relaxed by former President Donald Trump’s administration.

The EPA revisits its National Ambient Air Quality Standards every five years.

“Sometimes they get it right and they improve the standard so it protects more people and sometimes they get it wrong,” Knott said. “In many instances, our air quality standards aren’t strong enough to protect people.”

The Midwest Newsroom is an investigative journalism collaboration including KCUR, St. Louis Public Radio, Iowa Public Radio, Nebraska Public Media and NPR.