Formaldehyde, the chemical of choice for undertakers and embalmers, is also used in products like furniture and clothes. But it can also cause cancer and severe respiratory problems. So, in 2021, the Environmental Protection Agency began a new effort to regulate it.

The chemicals industry fought back with an intensity that astonished even seasoned agency officials. Its campaign was led by Lynn Dekleva, then a lobbyist at the American Chemistry Council, an industry group that spends millions of dollars on government lobbying.

Dr. Dekleva is now at the E.P.A. in a crucial job: She runs an office that has the authority to approve new chemicals for use. Earlier she spent 32 years at Dupont, the chemical maker, before joining the E.P.A. in the first Trump administration.

Her most recent employer, the chemicals lobbying group, has made reversing the Environmental Protection Agency’s course on formaldehyde a priority and is pushing to abolish a program under which the agency assess the risks of chemicals to human health. In recent weeks it has urged the agency to discard its work on formaldehyde entirely and start from scratch in assessing the risks.

The American Chemistry Council is also seeking to change the agency’s approval process for new chemicals and speed up E.P.A.’s safety reviews. That review process is a key part of Dr. Dekelva’s purview at the agency.

Another former chemistry council lobbyist, Nancy Beck, is back alongside Dr. Dekleva at the E.P.A. in a role regulating existing chemicals. The council’s president, Chris Jahn, told a Senate hearing shortly after the Trump inauguration that his group intended to tackle the “unnecessary regulation” of chemicals in the United States. “A healthy nation, a secure nation, an economically vibrant nation relies on chemistry,” he said.

It is not unusual or unlawful for industry groups to seek to influence public policy in the interest of their member companies. The A.C.C. estimates that products using formaldehyde support more than 1.5 million jobs in the United States.

What has been extraordinary, health and legal experts said, is the extent of the industry’s effort to block the E.P.A.’s scientific work on a chemical long acknowledged as a carcinogen, and how the architect of the effort was back at the agency as a regulator of chemicals. At the same time, the Trump administration has moved to sharply reduce the federal scientific work force.

“They already have a track record of ignoring the science,” said Tracey Woodruff, director of the Program on Reproductive Health and the Environment at the University of California, San Francisco. “Now, they’re in charge of government agencies that decide the rules.”

While leading the chemistry council’s fight to limit formaldehyde regulation, Dr. Dekleva called for investigations of federal officials for potential bias. The industry group used freedom of information laws to obtain emails of federal employees and criticized them in public statements for what they had written. It submitted dozens of industry-funded research papers to agencies that minimized the risks of formaldehyde.

The A.C.C. also sued both the E.P.A. and the National Academies, which advises the nation on scientific questions, accusing researchers of a lack of scientific integrity.

Allison Edwards, a chemistry council spokeswoman, said officials from the group had regularly met with E.P.A. staff members “to share critical science and to try and ensure an assessment of any chemistry is objective, employs rigorous scientific standards, and is reflective of real-world human exposure.” She said, “We’re asking to be one of many stakeholders at the table.”

Molly Vaseliou, a spokeswoman for the E.P.A., said the agency would continue to make sure it “ensures chemicals do not pose an unreasonable risk to human health or the environment.” At the same time, the agency would also work to approve “chemicals that are needed to power American innovation and competitiveness,” she said.

Formaldehyde’s cancer risk

Formaldehyde’s fumes can cause wheezing and a burning sensation in the eyes, especially when they accumulate indoors. That danger was apparent when formaldehyde in plywood used to build temporary trailer homes for victims of Hurricane Katrina sickened dozens of people.

And there are longer-term dangers, namely several types of cancers. The World Health Organization’s International Agency for Research on Cancer concluded in 2004 that the chemical is a human carcinogen, and the U.S. Department of Health listed it as a human carcinogen in 2011.

The chemical is restricted in the workplace, in certain composite wood products, and in pesticides. Yet efforts to strengthen overall regulations in the United States have stalled in the face of industry opposition.

President Biden, whose “cancer moonshot” program had made reducing cancer deaths a priority, revived in 2021 an E.P.A. assessment of the health effects of the chemical, and published a draft the following year. That effort, under the agency’s Integrated Risk Information System, was the first step toward regulating formaldehyde.

The chemistry council led a coalition of industry groups, including the Composite Panel Association and Kitchen Cabinet Manufacturers, arguing that formaldehyde had already been rigorously studied and that strict industry controls were in place.

In a half-dozen letters to the E.P.A., Dr. Dekleva, on behalf of a formaldehyde panel at the industry group, raised a list of complaints about the way the agency was carrying out its assessment.

She questioned research linking formaldehyde to leukemia, or cancer of the blood, and accused the agency of not relying on the best available science. There was a dose, she said, at which formaldehyde did not cause risk. There was also research, she said, that showed inhaled formaldehyde did not easily travel beyond the nose to cause harm to the body.

In light of these issues, Dr. Dekleva wrote, agency’s draft assessment was “flawed and unreliable without significant revision.”

To bolster its case, the industry group enlisted experts at consulting firms to submit opinions and studies to the E.P.A. minimizing formaldehyde’s risks. The firms included those previously commissioned by tobacco companies to help defend cigarettes.

The A.C.C. also submitted 41 peer-reviewed studies that it said refuted a link between formaldehyde and leukemia. A New York Times review found that the majority of the studies were funded by industry groups, including at least 11 from the Research Foundation for Health and Environmental Effects, an organization established by the American Chemistry Council.

David Michaels, an epidemiologist and professor at George Washington University School of Public Health and assistant secretary of labor under President Barack Obama, said the industry strategy was to create the appearance of disagreement among scientists.

While it’s true, he said, that inconsistencies can always exist in studies on humans, “there’s little disagreement among independent scientists that formaldehyde causes cancer.”

Scientists targeted

For more than 150 years, the National Academies has advised the U.S. government on science. In 2021, it was asked to weigh in on the E.P.A.’s work on formaldehyde.

It became a target of the American Chemistry Council.

The industry group used freedom of information laws to obtain internal emails of members and support staff of a panel assessing the E.P.A.’s formaldehyde review, and it accused one staff of showing “bias in favor of disputed research claiming formaldehyde causes leukemia.”

The staff member, a former Environmental Protection Agency scientist, had for example described as “wonderful” the news that Congress might try to replicate an influential Chinese study that had shown formaldehyde could cause leukemia.

Wendy E. Wagner, professor at the University of Texas School of Law and an expert on the use of science by environmental policymakers, said she did not see how the comment reflected bias. “After all, they don’t know what the results will be, do they?” she said. “I would expect all scientists to be enthusiastic about potential future research.”

Dr. Dekleva called for investigations at both the E.P.A. and the National Academies, and for the removal of potentially biased panel members and staff. That included scientists who had previously accepted federal research grants.

In July 2023, the industry group sued the E.P.A., as well as the National Academies, accusing researchers of a lack of scientific integrity. The chemistry council said that lack of integrity made the use of the National Academies research in regulating formaldehyde “arbitrary, capricious, and unlawful.”

“It was relentless, and beyond the pale,” said Maria Doa, a scientist at the E.P.A. for 30 years who is now senior director of chemicals policy at the Environmental Defense Fund. “They really ratcheted up their attacks on federal employees.”

The National Academies stood its ground, issuing a report the following month affirming the E.P.A.’s Integrated Risk Information System findings that formaldehyde is carcinogenic and increases leukemia risk.

Those conclusions are shared by other global health authorities.

Mary Schubauer-Berigan, the evidence-synthesis head at the World Health Organization’s Agency for Research on Cancer, said there was “sufficient evidence in humans” that formaldehyde causes leukemia as and nasopharynx cancer. Mikko Vaananen, a spokesman for the European Chemicals Agency, said that while some questions around specific links to leukemia remained unanswered, evidence was sufficient to classify formaldehyde as a carcinogen. Formaldehyde “cannot in principle be placed on the E.U. market,” he said.

In March 2024, a federal judge dismissed the chemistry council’s lawsuit. And early this year, near the end of the Biden administration, the E.P.A. issued a final risk determination, under the Toxic Substances Control Act: Formaldehyde “presents an unreasonable risk of injury to human health.”

Mary A. Fox, an expert in chemical risk assessment at the Johns Hopkins University Bloomberg School of Public Health and a member of a committee that reviewed the E.P.A.’s research on formaldehyde, said agency scientists had accurately reflected the uncertainties around the links between formaldehyde and leukemia. But they had documented many other streams of evidence that indicated that link, Dr. Fox said.

“It’s an inevitable progress of science, that as we learn more over time, we generally learn that health effects appear at lower concentrations than we had thought,” she said.

Following Mr. Trump’s re-election, the American Chemistry Council signed onto a letter from a range of industry groups calling for broad changes to policy, specifically citing formaldehyde. “We urge your administration to pause and reconsider” the E.P.A. findings on formaldehyde, the Dec. 5 letter said.

The E.P.A. “should go back to the scientific drawing board,” chemistry council said in January. The group was particularly concerned about the workplace limits the agency was suggesting, which it said ignored steps companies were already taking to protect workers, like the use of personal protective equipment.

The A.C.C. is also supporting a bill from Republican members of Congress that would end the Integrated Risk Information System.

Soon after, Trump transition officials said Dr. Dekleva would be returning to the E.P.A. to run a program assessing chemicals for approval. The chemistry council, which has long complained of a backlog, is pushing the agency to speed up approvals.

During the first Trump administration, agency whistle-blowers described in an inspector general’s investigation how they had faced “intense” pressure to eliminate the backlog, sometimes at the expense of safety. Shortly after the inauguration, the Trump administration fired the inspector-general who carried out the investigation.

On Jan. 20, the A.C.C. welcomed President Trump. “Americans want a stronger, more affordable country,” said Mr. Jahn, the group’s president. “America’s chemical manufacturers can help.”