Explosion at Pittsburgh Coke Plant Raises Concerns About Pollution and Safety

A 2025 blast at U.S. Steel's Clairton Coke Works facility has renewed scrutiny over the plant's history of accidents and environmental violations.

Published on Feb. 12, 2026

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An explosion at the Clairton Coke Works plant outside Pittsburgh in August 2025 killed two workers and injured 11 others, according to the Chemical Safety Board. The blast came amid a string of other accidents at the facility and a history of legal battles between U.S. Steel and local regulators over air pollution violations. Current and former workers say poor management and underinvestment have exacerbated environmental and safety issues at the aging plant, which is the largest of its kind in the Western Hemisphere.

Why it matters

The Clairton Coke Works has long been a major source of air pollution in the Pittsburgh region, with the Allegheny County Health Department regularly clashing with U.S. Steel over alleged violations. The 2025 explosion has heightened community concerns about the plant's environmental and safety record, especially as Nippon Steel's $15 billion acquisition of U.S. Steel raises questions about the facility's future.

The details

The August 2025 explosion happened while workers were closing and opening a gas isolation valve in a basement after pumping water into the valve, according to the Chemical Safety Board. U.S. Steel's written procedures did not mention using water, and a supervisor directed workers to pump the water, leading to the valve cracking and gas filling the area. The agency is still investigating how the gas was released and what ignited it. Before the blast, the plant had a history of accidents, including a 2009 explosion that killed a worker and a 2010 blast that injured 20 people. Current and former workers fault U.S. Steel's management of the aging facility, citing issues like difficulties replacing leaky coke oven doors.

  • The August 11, 2025 explosion killed two workers and injured 11 others.
  • In 2024, U.S. Steel agreed to a consent decree to invest nearly $20 million in facility upgrades at Clairton Coke Works.
  • In 2023, the Allegheny County Health Department fined U.S. Steel more than $2 million for violations at the Clairton plant.
  • A fire at the Clairton plant on Christmas Eve 2018 shut down pollution control equipment and led to repeated air pollution releases.

The players

U.S. Steel

The owner of the Clairton Coke Works facility, which is the largest of its kind in the Western Hemisphere.

Nippon Steel

The Japanese steel company that acquired U.S. Steel in a $15 billion deal in June 2025.

Allegheny County Health Department

The local regulatory agency that has routinely clashed with U.S. Steel over alleged air pollution violations at the Clairton plant.

Chemical Safety Board

The federal agency investigating the August 2025 explosion at the Clairton Coke Works facility.

Kurt Barshick

U.S. Steel's vice president of the Mon Valley Works, who presented information about the 2025 explosion to local residents.

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What they’re saying

“We must strengthen several safety protocols based on our own ongoing investigation, including prohibiting the use of high-pressure water for valve cleaning.”

— U.S. Steel (U.S. Steel statement)

“There was a release of coke oven gas and the gas contacted an ignition source and exploded.”

— Drew Sahli, Chemical Safety Board investigator in charge

“Workers trapped 3,000 PSI water inside of a valve that's rated for 50 PSI. The valve cracked and gas filled the area.”

— Kurt Barshick, U.S. Steel vice president of the Mon Valley Works

What’s next

The Chemical Safety Board is still investigating the cause of the August 2025 explosion at the Clairton Coke Works facility.

The takeaway

The Clairton Coke Works plant's history of accidents, environmental violations, and safety issues raises concerns about the facility's long-term viability and the new owner Nippon Steel's commitment to addressing these problems. The 2025 explosion has heightened calls for greater oversight and investment to improve the plant's operations and reduce its impact on the surrounding community.