Clearing the Air

Power plants and industrial facilities fueled by natural gas significantly contribute to several types of air pollution that damage our environment, exacerbate climate change, and pose a serious risk to people’s health. But major pollutants from gas-fired combustion turbines—engines that burn fuel to produce electricity or mechanical power at power plants and industrial facilities—are not yet subject to comprehensive protective federal clean air safeguards. These turbines emit harmful nitrogen oxides (NOx), greenhouse gases (GHGs), and hazardous air pollutants. Recently, the Environmental Protection Agency (EPA) unveiled a proposal to strengthen pollution limits for one of these three categories, NOx from new gas-fired combustion turbines. By law, the EPA must finalize these standards by November 2025 and consider comments from the public when shaping the final standards. This process provides the public with the opportunity to engage in the development of these protections and advocate for healthy, clean air for all.

The Clean Air Act requires the EPA to set air quality standards that limit the level of emissions coming from specific sources to protect public health and the environment, including emissions from gas-fired combustion turbines. While EPA has an obligation to limit this pollution at the federal level, states can also impose even stronger standards to further protect the health of their residents.

Currently, there is a need to strengthen each major category of pollution emitted by gas-fired turbines, especially:

• Strengthened Nitrogen Oxides (NOx) Standards: Strengthened standards are needed to protect the public from NOx pollution emitted by the new power sector and industrial sources. EPA has not updated the NOx standards for new gas-fired turbines since 2006. Today, some gas-fired turbines are achieving much lower rates than EPA's 2006 standards through the use of common pollution controls and demonstrating that far greater protections are achievable.
• New Greenhouse Gas (GHG) Standards: Comprehensive GHG standards are needed to protect people from the climate and public health effects of greenhouse gas pollution emitted by existing gas-fired combustion turbines in the power sector. While EPA has set GHG standards for new gas-fired combustion turbines, there are currently no GHG standards for such existing plants.
• Strengthened Hazardous Air Pollutant Standards: Strengthened standards are needed to protect people from toxic air pollution emitted by gas-fired combustion turbines in the power and industrial sectors. EPA’s list of 188 toxic air pollutants includes cancer-causing formaldehyde, benzene, mercury. EPA has not updated these standards for gas-fired turbines since 2004. Currently, the standards do not require that turbines install protective hazardous pollution controls, leaving threats to public health wide open. Moreover, emissions estimates for hazardous air pollutants are likely only a fraction (PDF) of the actual pollution from these facilities. We need greater data to better understand the extent of hazardous combustion turbine pollution, and we need more stringent pollution standards to reduce these toxic emissions and keep us all safe.

So, what exactly is a gas-fired combustion turbine?

A gas-fired combustion turbine is a type of engine that burns gas to create mechanical power. There are two common types of combustion turbine configurations: combined-cycle units and simple-cycle units. Combined-cycle units combine a stationary combustion turbine with a heat-recovery steam generator that captures and uses exhaust waste heat from the first cycle to generate additional power. These are typically larger, more fuel-efficient units that run more often.

Simple-cycle units are typically smaller, less fuel-efficient units that run less often. This fuel-inefficiency means simple-cycle units produce more pollution per unit of electricity generated than combined-cycle units.

Both types of combustion turbines are used in the power sector to generate electricity, as well in the industrial sector to drive manufacturing operations used to produce many materials, including glass, plastics, steel, and chemicals.

Check out our glossary of terms for more information on the technical aspects of combustion turbine operations.

Nitrogen oxides (NOx) harms

Exposure to NOx emissions from combustion turbines contributes to a range of serious health problems – such as heart disease, permanent lung damage, stroke, and aggravation of asthma – as well as premature death.

One of the primary pollutants resulting from natural gas combustion is a class of pollutants known as NOx. Exposure to NOx can cause numerous health issues. NOx is a particularly dangerous pollutant because it is a precursor pollutant, meaning that NOx chemically reacts with other substances to produce additional pollutants. NOx is a precursor for both harmful smog (ozone) and soot (particulate matter) pollution. Ground-level ozone and particulate matter are linked to cardiovascular illnesses, respiratory problems, and premature death, both in the short term and over a longer exposure period.

Exposure to ozone and particulate matter is particularly harmful for vulnerable groups, like children (4.6 million of whom have asthma in the US), who take more breaths per minute than adults and inhale proportionately higher doses of pollution. Expert studies assessing over 32 million births show that exposure to soot and smog is associated with increased risk of preterm birth and low birth weight. Highly vulnerable groups also include people with respiratory diseases or asthma, older adults, and outdoor workers A study of air pollution’s impacts to the Medicare population shows a significant association between ozone exposure and mortality, with the strongest effects in communities of color and lower socioeconomic areas.

EPA’s recent proposal presents the opportunity to revise federal NOx pollution standards and ensure that the standards sufficiently protect people's health. Today, some gas-fired power plants are achieving much lower rates than EPA's 2006 standard through use of a widely available control technology known as selective-catalytic reduction or "SCR."

Greenhouse gas harms

Fossil fuel-fired power plants, including those using gas turbines, are responsible for about one-quarter of our nation’s total greenhouse gas pollution.

Power plants are responsible for 1.4 billion tons of greenhouse gas emissions a year, one of the largest sources in the world. Greenhouse gases are a group of pollutants, including carbon dioxide, that trap heat in the atmosphere and contribute to climate change. Emissions of carbon dioxide from gas-fired power plants in the United States have almost doubled between 2005 and 2021.

Greenhouse gas pollution threatens public health and safety and the environment. As the climate changes due to greenhouse gas pollution, more people are exposed to dangerous and potentially deadly extreme weather events. Climate disasters have been increasing in frequency and intensity: since 1980, there have been 376 weather and climate disasters in the U.S. costing more than $1 billion each, with more than one-quarter of these events occurring in just the past five years.

Climate change is particularly detrimental to public health. Excessive heat caused by climate change increases the risk of heat stroke, dehydration-related illness, hospitalization, vector-borne disease (e.g. lyme’s disease), preterm birth, and low birth weight, among other harms. In 2023, there were 2,300 recorded heat-related deaths across the United States— triple the annual average between 2004-2018—a figure experts believe is likely only a fraction of the actual number. Several U.S. regions experienced a record high (PDF) of heat-related emergency room visits in 2023, totaling 119,000 visits.

In addition, climate change intensifies the health harms caused by other air pollutants, including soot and smog. Increased temperatures caused by climate pollutants create favorable conditions for smog formation, which occurs when NOx reacts with volatile organic compounds in the presence of sunlight. Climate pollutants also increase instances and severity of drought and wildfire, which release soot (dust and smoke) into the air. The U.S. Climate Vulnerability Index, a separate mapping project by EDF and its partners, shows the unique climate vulnerabilities of each census tract in the United States.

Although the EPA issued greenhouse gas standards for new gas power plants in 2024, existing gas power plants are not currently subject to any federal greenhouse gas standards. The Clean Air Act requires that EPA promulgate technology-based emissions standards for harmful climate pollution from existing gas-fired power plants. These standards would allow power companies to achieve the required pollution reductions through an array of available low- and zero-emitting solutions. Clean, renewable energy options are emissions-free, more affordable than ever, reliable, and are the leading source of new electricity generation being deployed across the country.

In addition to federal standards, states can mandate strong pollution limits and clean energy solutions. For example, eleven Northeastern states are part of the Regional Greenhouse Gas Initiative, where each state has established individual carbon pollution budgets as part of a regional cap and trade program. In addition, 24 states and the District of Columbia have enacted 100% clean energy goals.

Hazardous air pollutant harms

Gas turbines emit other highly toxic pollutants that can cause cancer and developmental harms.

Gas turbines also emit hazardous air pollutants, which are a harmful class of 188 pollutants known to cause cancer, neurological damage, kidney damage, and reproductive harms, among other negative impacts. Hazardous air pollutants are particularly harmful to babies and children, which are at risk of brain and developmental harms from exposure to hazardous air pollution.

Hazardous air pollutants emitted by gas turbines include formaldehyde, polycyclic aromatic hydrocarbons (PAH), benzene, toluene, xylenes, and others. EPA’s toxicology review of one of those pollutants, formaldehyde, notes that inhaling it can cause cancer in humans (PDF) and that exposure can lead to effects ranging from wheezing and bronchitis to reproductive and developmental toxicity and worse. The agency’s National Air Toxics Assessment notes that about half of the nationwide average cancer risk (PDF) from breathing air toxics comes from formaldehyde. The Chemical Exposure Action Map, a separate mapping project by EDF, shows how communities across the United States are cumulatively exposed to hazardous pollutants from multiple sources.

EPA has not updated the Hazardous Air Pollution standards for gas-fired combustion turbines since 2004. Currently, the standards do not require that turbines install protective controls. In addition, the emissions factors – values used to estimate hazardous air pollution based on associated activity – allow industry and EPA to underestimate emissions (PDF). EPA should update its emissions factors to ensure that emissions are more accurately calculated. EPA should also issue protective standards based on the use of oxidation catalysts and dual-oxidation catalysts – controls that limit hazardous air pollution – and require continuous emissions monitoring, or CEMS, to monitor emissions and ensure the proper operation of controls.

States can also provide important protections by imposing more stringent standards at the state-level. For example, Massachusetts has more stringent standards for certain hazardous pollutants.

Communities near power plants are more likely to have higher populations of people of color, and higher poverty rates

Numerous studies show correlations between power plant locations or emissions and lower-income communities and communities of color. A larger share of people of color and people with low incomes live near power plants, according to an analysis of Regional Greenhouse Gas Initiative data. Specifically, 42.6% of communities with higher levels of people of color and low-income populations in this study had between two and five power plants sited in their community, whereas only 28% of other communities contained the same number of plants.

Differences in people’s health depending on their racial or ethnic group or socioeconomic status can be linked to environmental factors, including increased exposure to environmental hazards. For this reason, areas with particularly high levels of pollution are sometimes called “sacrifice zones,” referring to the low-income and racial and ethnic minority populations whose health gets sacrificed.

Some areas with already-dense concentrations of gas turbines could be at risk of worsening pollution in the coming years. Researchers expect an increase in gas-fired power plant construction to support data centers due to the rise in electricity demand spurred by artificial intelligence. Where these facilities are built is largely determined by state regulatory conditions, and researchers expect that Texas, Oklahoma, and Louisiana are likely host states for additional gas-fired power plants. Analysts forecast that Texas, in particular, could see nearly a quarter of all load growth in the U.S. over the next decade because of its regulatory environment, land availability, and natural gas resources.

Figure 1 below illustrates where existing power sector and industrial turbines are located and shows clusters in regions with historically overburdened communities, including in the Houston-Galveston region in Texas, Long Beach-Bakersfield region in California, New York City, and southern Louisiana.

Which U.S. states and Congressional districts have the highest emissions from gas-fired power plants?

Certain regions across the US have particularly high emissions of carbon dioxide, nitrogen oxides, and formaldehyde from gas-fired power plants.

Where are the highest levels of carbon dioxide pollution?

Texas (91.5 million short tons), Florida (77.9 million short tons), and Pennsylvania (51.2 million short tons) had the highest carbon dioxide emissions nationwide from gas-fired power plants, according to 2022 data.

On the Congressional district level, Florida’s 18th district in south-central Florida recorded the highest carbon dioxide emissions in the country at 17.9 million short tons in 2022. Ohio’s sixth Congressional district, on the state’s eastern border, followed at 11 million short tons. And Florida’s 20th Congressional district in the southeastern part of the state had the third-highest measure of carbon dioxide emissions in the country at 10.6 million short tons.

Where are the highest levels of NOx pollution?

Texas (37.8 million lbs.), Florida (24.5 million lbs.), and Michigan (11.8 million lbs.) had the highest NOx pollution from gas-fired power plants, according to 2022 data.

The highest emissions of nitrogen oxides in a Congressional district were seen in Michigan’s eighth district, which includes the city of Flint, at 6 million lbs. in 2022. Florida’s 18th district followed with 5.1 million lbs., and Florida’s 12th district, on the state’s west coast, had the third-highest NOx emissions in the country at 4.5 million lbs.

Where is the highest potential for uncontrolled formaldehyde pollution?

Calculating formaldehyde emissions is especially challenging because there is a lack of comprehensive data indicating which facilities have pollution controls for formaldehyde installed. Uncontrolled measures refer to situations where emission sources have no pollution controls and represent the worst case scenario of emissions. However, these emissions are estimations calculated through the use of emissions factors and these worst case scenarios are likely an underestimate of actual emissions.

Texas (4.1 million lbs.), Florida (3.3 million lbs.), and California (1.8 million lbs.) had the highest potential for uncontrolled formaldehyde pollution from gas-fired power plants in 2022.

The top three Congressional districts with the highest uncontrolled formaldehyde emissions in 2022 were Florida’s 18th district with 571,388 lbs., Texas’s 36th district with 512,815 lbs., and Arizona’s ninth district with 507,955 lbs.

Take Action

Despite the damaging impact of these pollutants, we are all empowered to take action to limit these emissions for our families and communities. EPA’s recent proposal for strengthened NOx standards for new gas-fired sources presents a unique opportunity for the public to help shape these protections. Pollution from gas-fired power plants and industrial sources harms millions across the country. Take action now by commenting on EPA’s proposal by March 13, 2025 and letting EPA know that we need health-protective standards based on proven pollution control technologies.

Are you curious about the level of turbine emissions near you? Check out our interactive map.

EDF joined forces with Moms Clean Air Force and Ecomadres to create this interactive mapping tool. Moms Clean Air Force is a community of more than 1.5 million moms, dads, and caregivers united to protect children from air pollution and the urgent crisis of our changing climate. With organizers across the country, Moms advocate at the local, state, and national levels for equitable, just, and healthy solutions to pollution. EcoMadres is a Moms Clean Air Force program that empowers and mobilizes Latino communities, which are disproportionately affected by air pollution and climate change, to fight for clean air and environmental justice.