A new Trump administration plan to rescind 2024 regulations for toxic ethylene oxide (EtO) pollution more broadly aims to limit the Environmental Protection Agency’s authority to strengthen public health protections around hazardous emissions and could result in more of the toxin being released into the air.

Recent research has found EtO is about 60 times more carcinogenic than thought when the last regulations were developed in 2006. In 2024, the Biden EPA passed a rule that strengthened the regulations to reflect the updated science, and required the nation’s EtO emitters to collectively cut their emissions by about 90%.

A new Harvard analysis details the administration’s case, which would limit the EPA’s ability to strengthen regulations when it determines hazardous air pollutants are more dangerous than previously thought.

If the Trump EPA is successful in the legal fight, the 2024 regulations would be rescinded, resulting in nearly 8 tons of the carcinogenic gas continuing to be released in largely low-income neighborhoods. It would also permanently make it more difficult for the EPA to later protect people from toxic air pollutants.

The move is part of the industry’s and the administration’s “broader strategy to roll back a wide array of controls on toxic chemicals and, particularly, carcinogens”, said Erik Olson, senior adviser with the Natural Resources Defense Council (NRDC).

“This sends up a signal flare to everyone that we’ve got a real threat, and that the administration plans to gut cancer protections,” Olson said. The NRDC is among the plaintiffs in a lawsuit on a separate issue around the chemical.

The outcome of its plan is especially important, public health advocates say, because of how regulations around chemicals are structured. Chemicals are generally approved with little review of industry claims that their substances are safe, and it can take independent science decades to learn the true risk, as has happened with EtO.

It would also probably undo regulations, or proposed rules, around two other chemicals.

EtO is a flammable, colorless gas used to sterilize about 20bn medical devices annually, including pacemakers and syringes, as well as some foods. The chemical is also a potent carcinogen when inhaled, and linked to leukemia, among other health issues. Rescinding the new rule would leave about 2.3 million people exposed to the toxic gas.

The 2024 Biden EPA rule would have reduced emissions at 89 facilities, had they gone into effect. The rule would have achieved that by, among other measures, requiring companies to use continuous monitoring and rein in fugitive emissions. Fugitive emission is air pollution that escapes from piping or places within a factory from which they are not intended to escape.

The Trump administration’s proposed rescission would save companies $50m annually, the Harvard report notes. The agency did not calculate the costs associated with cancer increases, so the societal burden is unclear.

The Clean Air Act explicitly requires the EPA to do a “residual risk review” of toxic chemicals within eight years after they are designated as hazardous pollutants. The agency first set emission standards for EtO in 1994, and completed its residual review in 2006, said Giancarlo Vargas, the paper’s co-author and attorney with the Harvard Environmental and Energy Law Program.

More recent research shows the chemical is estimated to be 60 times more carcinogenic than levels used in the 2006 reassessment, Vargas said, so the EPA under Biden did a “discretionary” review aimed at strengthening limits and protecting public health.

The Clean Air Act, however, “doesn’t really discuss whether you can do additional discretionary reviews” beyond the first that checks for a pollutant’s health impact, Vargas said. Under Biden, the EPA essentially interpreted the law as not prohibiting additional reviews, but the Trump administration is “now saying actually the silence means we don’t have the authority to go do this again”, Vargas said.

It was a “big change” that would “rein in the EPA’s ability to consider public health risks when updating hazardous air pollutant standards”, Vargas added.

He said he could not speak to why the EPA would want to do this, and the paper dissects the legal strategy, but does not take a position about whether the Trump EPA’s actions were sound or ethical.

The agency is required by the Clean Air Act to do a technical review every eight years that assesses whether the best available technology around a chemical is being used, but that does not directly include public health questions.

The administration’s action around EtO is “part of a broader pattern of authority limiting interpretations by the EPA”, said Erika Kranz, a supervisor at the Harvard Environmental and Energy Law Program.

“We’ve seen EPA in other contexts during this administration also adopt these new statutory interpretations that limit the agency’s authority,” she said, noting the administration’s recent, controversial endangerment finding.

The stakes in the legal battle are especially high because “this is locked in in the future – the EPA can’t take a new interpretation of that statute,” Kranz added.

Meanwhile, the NRDC is suing to stop the Trump administration from exempting EtO and other chemicals from regulations under the hazardous air pollutant rule. The president is wielding a never-before-used provision in the law that allows for exemptions for national security purposes, or if technology to implement the rule is “not available”.

The move exempted about half of all commercial medical sterilizers from EtO standards, but the administration has not provided any evidence to support the decision, the NRDC alleges.

“President Trump’s exemptions of chemical plants from regulations of hazardous air pollutants not only sacrifice the health of communities, but they are also illegal and undemocratic,” Jen Sass, NRDC’s senior scientist, said in a statement.