A plan by the Trump administration to rescind strict 2024 rules on ethylene oxide emissions threatens to undo protections for millions of Americans and could permanently weaken the Environmental Protection Agency's power to tighten regulations when science shows a chemical is deadlier than once thought.
Ethylene oxide, or EtO, is a colorless, flammable gas used to sterilize roughly 20 billion medical devices annually, from pacemakers to syringes. It is also a potent carcinogen linked to leukemia and other cancers. Recent research shows the chemical is about 60 times more carcinogenic than scientists believed in 2006, when the EPA last comprehensively reviewed it.
The Biden EPA responded to that updated science by issuing tougher regulations in 2024, requiring EtO emitters across the nation to cut their emissions by approximately 90 percent. The Trump administration now wants to eliminate those rules, a move that would allow nearly 8 tons of the carcinogenic gas to continue pouring into the air, predominantly in low-income neighborhoods.
If the rescission succeeds, about 2.3 million people would remain exposed to the toxic gas. The rollback would also accomplish something broader: it would cripple the EPA's legal ability to strengthen regulations for any hazardous air pollutant if new science later reveals it poses greater danger than previously understood.
A Harvard Environmental and Energy Law Program analysis details the administration's legal strategy. The dispute centers on how the Clean Air Act should be interpreted. The law requires the EPA to conduct a residual risk review of toxic chemicals within eight years of designating them as hazardous pollutants. The EPA set EtO standards in 1994 and completed that mandated review in 2006.
Under the Biden administration, the EPA interpreted the statute as not prohibiting additional voluntary reviews aimed at tightening protections when science improved. The Trump EPA is now arguing the opposite: that silence in the statute means the agency lacks authority to conduct discretionary reviews beyond the initial eight-year review.
"This is a big change that would rein in the EPA's ability to consider public health risks when updating hazardous air pollutant standards," said Giancarlo Vargas, co-author of the Harvard report and an attorney with the law program.
The implications extend far beyond ethylene oxide. Legal experts say the Trump administration's interpretation could also undo regulations or proposed rules around two other chemicals and sets a precedent that permanently locks the EPA out of strengthening protections if future research uncovers greater health threats.
"This sends up a signal flare to everyone that we've got a real threat, and that the administration plans to gut cancer protections," said Erik Olson, senior adviser with the Natural Resources Defense Council action fund.
The 2024 rule would have reduced emissions at 89 facilities by requiring companies to use continuous monitoring and control fugitive emissions, which is air pollution that escapes unintentionally from pipes and factory points. The Trump administration's proposed rescission would save companies $47 million annually, according to the Harvard analysis. The Trump EPA has stopped calculating the human costs of increased cancer cases, leaving the true public health burden unknown.
The administration is also pursuing a separate legal strategy: wielding a never-before-used provision in the Clean Air Act to exempt EtO and other chemicals from regulations if they claim the technology to comply is unavailable or if compliance poses national security risks. That exemption has already excluded about half of all commercial medical sterilizers from EtO standards, though the administration has provided no evidence supporting either claim.
The Natural Resources Defense Council is suing to block both the rescission and the exemptions. "President Trump's exemptions of chemical plants from regulations of hazardous air pollutants not only sacrifices the health of communities, but they are also illegal and undemocratic," said Jen Sass, an NRDC attorney.
The public health stakes are shaped by how chemical regulations work in practice. Chemicals typically receive regulatory approval with minimal scrutiny of industry safety claims. It can take independent scientists decades to understand the true risks. EtO is a textbook example: what was thought safe in 2006 turned out to be vastly more dangerous, a revelation that arrived only through later research.
Author James Rodriguez: "The administration's legal theory is a backdoor way to freeze protection standards in place forever, even when science screams that people are being poisoned."
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