Fossil fuel power plants are staying online longer
That means dirtier air
The data center boom is keeping some old, dirty power plants that were set to retire online for years longer than planned. The resulting air pollution threatens our health.
The rapid expansion of data centers powering artificial intelligence and other forms of computing poses an immediate threat to our air: Data center expansion is helping to keep some of the nation’s oldest and dirtiest fossil fuel power plants online. As long as these plants are kept online, continued emissions of harmful air pollution will threaten human health.
In October, we identified at least 33 fossil fuel generating units across 15 power plants whose planned retirements were postponed due to reliability concerns associated with energy demand from data centers. Then in April 2026, four units at two more highly polluting power plants in Pennsylvania, Keystone and Conemaugh, also delayed their retirements by four years to help “cover projected increased electrical demand driven by build-out of data centers.”
Some of these power plants were already expected to be retired by now: In total, 8.1 GW of coal capacity that was scheduled to be retired by the end of 2025 is still being kept online.
Together, these 17 “zombie power plants” with 37 fossil fuel units being kept online released more global warming emissions than the entire state of Massachusetts emitted on net in 2022. But fossil fuel power plants don’t just contribute to climate change; they also create local air pollution that is harmful to the health of nearby communities and the environment.
Keeping polluting power plants online harms public health
Fossil fuel power plants emit pollutants such as sulfur dioxide (SO2) and nitrogen oxides (NOx). Both SO2 and NOx contribute to the formation of fine particle pollution (PM2.5) and NOx contributes to ground-level ozone – two forms of air pollution that threaten human health.
Fine particle pollution aggravates asthma, decreases lung function, and increases respiratory symptoms such as coughing or difficulty breathing. Ground-level ozone aggravates lung diseases including asthma, emphysema and chronic bronchitis. These pollutants are especially harmful to people with pre-existing respiratory conditions, kids and older adults.
In addition, coal plants also emit mercury, an extremely harmful neurotoxin. When released into the environment, elemental mercury from coal-fired power plants is converted into methylmercury, which is consumed by aquatic organisms and accumulates as it moves up the food chain until it is eaten by humans. The children of mothers who ingest methylmercury during pregnancy can experience damage to their cognitive skills and memory as they grow.
In 2023, according to the U.S. Environmental Protection Agency, these 37 fossil generators released massive amounts of harmful air pollution, including:
- 32,926 tons of SO2
- 29,558 tons of NOx
- 272 pounds of mercury
Emissions from these plants accounted for roughly 3.1% of NOx and 4.4% of the SO2 and pollution from power plants nationwide. However, the plants generated only 1.2% of the nation’s power, as reported to the EPA.
Of the 17 zombie power plants, J. H. Campbell in Michigan emitted the most mercury, and Plant Bowen in Georgia emitted the most SO2 and NOx.
Emissions from zombie fossil fuel plants, 2023 (includes only units with delayed retirement)*
Keeping old, dirty fossil fuel plants is harming our health
The pace and scope of the data center boom in the U.S. is uncertain. We simply don’t know how many data centers will be needed to do what we want AI for. But this much is clear: Growing electricity demand from data centers is increasing reliance on fossil fuels and delaying the retirement of aging power plants. As a result, more harmful air pollutants are being released into the atmosphere – endangering both public health and the environment.
* Unit-level emissions data from U.S. Environmental Protection Agency, eGRID with 2023 data, downloaded from https://www.epa.gov/egrid/detailed-data, April 14, 2026. Note that data exclude oil-fired Unit A at E.C. Gaston, whose retirement has been delayed but reported no emissions to eGRID in 2023. A previous version of this article did not include emissions data for Keystone and Conemaugh in Pennsylvania.
Kylie Hanson provided research assistance for this article.
Tell state lawmakers: Don’t subsidize energy-hungry data centers
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Authors
Quentin Good
Policy Analyst, Frontier Group
Quentin Good is a policy analyst with Frontier Group. He has a B.A in Economics from Metropolitan State University of Denver and an M.A in International Finance, Trade, and Economic Integration from the University of Denver. He served with the U.S. Peace Corps for three years in Senegal, West Africa, as a community economic development volunteer and sector leader. Quentin lives and works in Denver.
Johanna Neumann
Senior Director, Campaign for 100% Renewable Energy, Environment America Research & Policy Center
Johanna directs strategy and staff for Environment America's energy campaigns at the local, state and national level. In her prior positions, she led the campaign to ban smoking in all Maryland workplaces, helped stop the construction of a new nuclear reactor on the shores of the Chesapeake Bay and helped build the support necessary to pass the EmPOWER Maryland Act, which set a goal of reducing the state’s per capita electricity use by 15 percent. She also currently serves on the board of Community Action Works. Johanna lives in Amherst, Massachusetts, with her family, where she enjoys growing dahlias, biking and the occasional game of goaltimate.
Abe Scarr
Energy and Utilities Program Director, U.S. PIRG Education Fund
Abe Scarr is the director of Illinois PIRG and is the PIRG Energy and Utilities Program Director. He is a lead advocate in the Illinois Capitol and in the media for stronger consumer protections, utility accountability, and good government. In 2017, Abe led a coalition to pass legislation to implement automatic voter registration in Illinois, winning unanimous support in the Illinois General Assembly for the bill. He has co-authored multiple in-depth reports on Illinois utility policy and leads coalition campaigns to reform the Peoples Gas pipe replacement program. As PIRG's Energy and Utilities Program Director, Abe supports PIRG energy and utility campaigns across the country. He also serves as a board member for the Consumer Federation of America. Abe lives in Chicago, where he enjoys biking, cooking and tending his garden.
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