In a world flush with hazardous air pollutants, there is one that causes far more cancer than any other, one that is so widespread that nobody in the United States is safe from it.

It is a chemical so pervasive that a new analysis by ProPublica found it exposes everyone to elevated risks of developing cancer no matter where they live. And perhaps most worrisome, it often poses the greatest risk in the one place people feel safest: inside their homes.

As the backbone of American commerce, formaldehyde is a workhorse in major sectors of the economy, preserving bodies in funeral homes, binding particleboards in furniture and serving as a building block in plastic. The risk isn’t just to the workers using it; formaldehyde threatens everyone as it pollutes the air we all breathe and leaks from products long after they enter our homes. It is virtually everywhere.

Federal regulators have known for more than four decades that formaldehyde is toxic, but their attempts to limit the chemical have been repeatedly thwarted by the many companies that rely on it.

This year, the Biden administration finally appeared to make some progress. The Environmental Protection Agency is expected to take a step later this month toward creating new rules that could restrict formaldehyde.

But the agency responsible for protecting the public from the harms of chemicals has significantly underestimated the dangers posed by formaldehyde, a ProPublica investigation has found.

The EPA is moving ahead after setting aside some of its own scientists’ conclusions about how likely the chemical is to cause myeloid leukemia, a potentially fatal blood cancer that strikes an estimated 29,000 people in the U.S. each year. The result is that even the EPA’s alarming estimates of cancer risk vastly underestimate — by as much as fourfold — the chances of formaldehyde causing cancer.

The agency said it made the decision because its estimate for myeloid leukemia was “too uncertain” to include. The EPA noted that the National Academies of Sciences, Engineering and Medicine, which the agency paid to review its report, agreed with its decision not to include myeloid leukemia in its cancer risk. But four former government scientists with experience doing statistical analyses of health harms told ProPublica that the myeloid leukemia risk calculation was sound. One said the risk was even greater than the agency’s estimate.

Jennifer Jinot, one of the EPA scientists who spent years calculating the leukemia risk, said there is always uncertainty around estimates of the health effects of chemicals. The real problem, she said, was cowardice.

“In the end, they chickened out,” said Jinot, who retired in 2017 after 26 years working at the EPA. “It was kind of heartbreaking.”

The EPA has also retreated from some of its own findings on the other health effects of formaldehyde, which include asthma in both children and adults; other respiratory ailments, including reduced lung function; and reproductive harms, such as miscarriages and fertility problems. In a draft report expected to be finalized this month, the agency identified many instances in which formaldehyde posed a health threat to the public but questioned whether most of those rose to a level the agency needed to address. In response to questions from ProPublica, the EPA wrote in an email that the report was not final and that the agency was in the process of updating it.

Still, if the past is any guide, even the limited efforts of President Joe Biden’s administration are all but guaranteed to hit a dead end after Donald Trump is inaugurated. And one of the longest-running attempts to restrict a dangerous chemical in American history would be set back yet again.

ProPublica reporters have spent months investigating formaldehyde, its sweeping dangers and the government’s long, frustrating battle to curb how much of it we breathe.

They have analyzed federal air pollution data from each of the nation’s 5.8 million populated census blocks and done their own testing in homes, cars and neighborhood businesses. They have interviewed more than 50 experts and pored through thousands of pages of scientific studies and EPA records. They’ve also reviewed the actions of the previous Trump administration and what’s been disclosed about the next.

The conclusion: The public health risks from formaldehyde are greater and more prevalent than widely understood — and any hope of fully addressing them may well be doomed, at least for the foreseeable future.

Since its inception, the EPA has been outgunned by the profitable chemical industry, whose experts create relatively rosy narratives about their products. That battle intensified over the last four years as the EPA tried to evaluate the scope of the public health threat posed by formaldehyde.

Regulatory rules put the onus on the government to prove a chemical is harmful rather than on industry to prove its products are safe. Regardless of who is in the White House, the EPA has staff members with deep ties to chemical companies. During some administrations, it is run by industry insiders, who often cycle between jobs in the private sector and the government.

Trump has already vowed to roll back regulations he views as anti-business — an approach that promises to upend the work of government far beyond formaldehyde protections. Still, this one chemical makes clear the potential human toll of crafting rules to serve commerce rather than public health. And Trump’s last term as president shows how quickly and completely the efforts now underway might be stopped.

At the EPA, he appointed a key figure from the chemical industry who had previously defended formaldehyde. The agency then quietly shelved a report on the chemical’s toxicity. It refused to enforce limits on formaldehyde released from wood products until a judge forced its hand. And it was under Trump that the agency first decided not to include its estimate of the risk of developing myeloid leukemia in formaldehyde’s overall cancer risk calculation, weakening the agency’s ability to protect people from the disease.

The latest efforts to address formaldehyde pollution are likely to meet a similar fate, according to William Boyd, a professor at UCLA School of Law who specializes in environmental governance. Boyd has described formaldehyde as a sort of poster child for the EPA’s inability to regulate chemicals. Because formaldehyde is key to so many lucrative industrial processes, companies that make and use it have spent lavishly on questioning and delaying government efforts to rein it in.

“The Biden administration was finally bringing some closure to that process,” said Boyd. “But we have every reason to suspect that those efforts will now be revised. And it will likely take years for the EPA to do anything on this.”

Invisible Threat

Perhaps best known for preserving dead frogs in high school biology labs, formaldehyde is as ubiquitous in industry as salt is in cooking. Between 1 billion and 5 billion pounds are manufactured in the U.S. each year, according to EPA data from 2019.

Outdoor air is often suffused with formaldehyde gas from cars, smoke, factories, and oil and gas extraction, sometimes at worrying levels that are predicted to worsen with climate change. Much of the formaldehyde outdoors is also spontaneously formed from other pollutants.

Invisible to the eye, the gas increases the chances of getting cancer — severely in some parts of the country.

This year, the EPA released its most sophisticated estimate of the chance of developing cancer as a result of exposure to chemicals in outdoor air in every populated census block across the United States. The agency’s sprawling assessment shows that, among scores of individual air pollutants, formaldehyde poses the greatest cancer risk — by far.

But ProPublica’s analysis of that same data showed something far more concerning: It isn’t just that formaldehyde poses the greatest risk. It’s that its risk far exceeds the agency’s own goals, sometimes by significant amounts.

ProPublica found that, in every census block, the risk of getting cancer from exposure to formaldehyde in outdoor air over a lifetime is higher than the limit of one incidence of cancer in a million people, the agency’s goal for air pollutants. That risk level means that if a million people in an area are continuously exposed to formaldehyde over 70 years, the chemical would cause at most one case of cancer, on top of those from other risks people already face.

According to ProPublica’s analysis of the EPA’s 2020 AirToxScreen data, some 320 million people live in areas of the U.S. where the lifetime cancer risk from outdoor exposure to formaldehyde is 10 times higher than the agency’s ideal.

(ProPublica is releasing a lookup tool that allows anyone in the country to understand their outdoor risk from formaldehyde.)

In the Los Angeles/San Bernardino, California, area alone, some 7.2 million people are exposed to formaldehyde at a cancer risk level more than 20 times higher than the EPA’s goal. In an industrial area east of downtown Los Angeles that is home to several warehouses, the lifetime cancer risk from air pollution is 80 times higher, most of it stemming from formaldehyde.

Even those alarming figures underestimate the true danger. As the EPA admits, its cancer risk calculation fails to reflect the chances of developing myeloid leukemia. If it had used its own scientists’ calculation — “the best estimate currently available,” according to the agency’s August report — the threat of the chemical would be shown to be far more severe. Instead of causing 20 cancer cases for every million people in the U.S., formaldehyde would be shown to cause approximately 77.

Using the higher figure to set regulations of the chemical could eventually help prevent thousands of cases of myeloid leukemia, according to ProPublica’s analysis.

As Mary Faltas knows, the diagnosis can upend a life.

Faltas, 60, is still sorting through the aftermath of having myeloid leukemia, which she developed in 2019. “It’s like having a storm come through,” she said recently. “It’s gone, but now you’re left with everything else to deal with.”

It wasn’t always clear she’d survive. There are two types of myeloid leukemia. Faltas had the more deadly acute form and spent a year and a half undergoing chemotherapy, fighting life-threatening infections and receiving a bone marrow transplant. Too sick to work, she lost her job as a dental assistant. She and her husband were forced to sell their house in Apopka, Florida, and downsize to a small condo — a move that took place when she was too weak to pack a box.

It’s almost always impossible to pinpoint a single cause for someone’s cancer. But Faltas has spent her entire life in places where the EPA’s data shows there is a cancer risk 30 times the level the agency says it strives to meet. And in that way, she’s typical. Nationwide, that’s the average lifetime cancer risk from air pollution; formaldehyde accounts for most of it. Factor in the EPA’s myeloid leukemia calculation, and Faltas has lived in places where cancer risk from formaldehyde alone is 50 to 70 times the agency’s goal.

Layered on top of the outdoor risk we all face is the much more considerable threat indoors — posed by formaldehyde in furniture, flooring, printer ink and dozens of other products. The typical home has a formaldehyde level more than three times higher than the one the EPA says would protect people against respiratory symptoms. The agency said it came up with its recommended level to protect sensitive subgroups and that the potential for health effects just above it are “unknown.”

The EPA’s own calculations show that formaldehyde exposure in those homes would cause as many as 255 cancer cases in every million people exposed over their lifetimes — and that doesn’t reflect the risk of myeloid leukemia. The agency also said “there may not be a feasible way currently to reduce the average indoor level of formaldehyde to a point where there is no or almost no potential risk.”

ProPublica will delve more into indoor risks, and how to guard against them, in the coming days.

The Long Road to Nowhere

The fruitless attempts to limit public exposure to formaldehyde stretch back to the early ’80s, soon after the chemical was shown to cause cancer in rats.

The EPA planned to take swift action to reduce the risks from formaldehyde, but an appointee of President Ronald Reagan named John Todhunter stopped the effort. He argued that formaldehyde didn’t pose a significant risk to people. A House investigation later revealed he had met with chemical industry representatives, including a lobbyist from the Formaldehyde Institute, just before making his decision. Todhunter denied being influenced but resigned under pressure.

In 1991, under President George H.W. Bush, the EPA finally deemed formaldehyde a probable human carcinogen and calculated the likelihood of it causing an extremely rare cancer that affects a part of the throat called the nasopharynx. But it quickly became clear that more protection was needed.

A 2003 study showed that factory workers exposed to high levels of formaldehyde were 3 1/2 times more likely to develop myeloid leukemia than workers exposed to low levels of the chemical. “Having human data showing an effect like that … it’s a rare thing,” said Jinot, the former EPA statistician and toxicologist. “You want to seize that opportunity.”

She and colleagues at the agency crunched numbers, immersed themselves in the medical literature and consulted with other scientists to conclude that formaldehyde was a known carcinogen and caused myeloid leukemia, among other cancers.

But in 2004, their work hit a roadblock. Sen. James Inhofe, R-Okla., persuaded the EPA to delay the update of its formaldehyde report until the National Cancer Institute released the results of a study that was underway.

The harms, meanwhile, continued to mount. In 2006, people who lost their homes in Hurricane Katrina and were housed in government trailers began to report feeling sick. The symptoms, which included breathing difficulties, eye irritation and nosebleeds, were traced to high levels of formaldehyde.

In 2009, under the Obama administration, the EPA was once again poised to release its report on the toxicity of formaldehyde. By then, the National Cancer Institute’s study had been published, making the link between formaldehyde and myeloid leukemia even clearer.

This time, another U.S. senator intervened. David Vitter, R-La., who had received donations from chemical companies and a formaldehyde lobbyist, held up the confirmation of an EPA nominee. He agreed to approve the nomination in exchange for an additional review of the formaldehyde report by a panel of the National Academies of Sciences, Engineering and Medicine.

The outside review found “problems with clarity and transparency of the methods” used in the EPA report and recommended that, in its next version, the EPA employ “vigorous editing” and explain its arguments more clearly.

But the EPA would not issue that next version for more than a decade. After the outside review, the chemical industry seized on its findings as evidence of fundamental problems at the agency. For years afterward, the EPA’s release of chemical assessments — and its work on the formaldehyde assessment — slowed. “They became completely cowardly,” Jinot said. “They were shell-shocked and retreated.”

As the EPA went about revising its report, it fell behind others around the world in recognizing that formaldehyde causes cancer. The World Health Organization’s arm that researches cancer had already concluded in 2006 that the chemical is a carcinogen. Five years later, scientists with the Department of Health and Human Services found that formaldehyde causes cancer, citing studies linking it to myeloid leukemia.

Between 2011 and 2017, the Foundation for Chemistry Research and Initiatives, which had been created by an industry trade group, funded 20 studies of the chemical. The research presented formaldehyde as relatively innocuous. The industry trade group still disputes the mainstream science, insisting that “the weight of scientific evidence” shows that formaldehyde does not cause myeloid leukemia.

The trade group’s panel on formaldehyde also complained that regulation would be devastating for business. The argument was undercut by one of the few limits the EPA did manage to put in place.

In 2016, the EPA issued a rule limiting the release of formaldehyde from certain wood products sold in the U.S. Under Trump, the agency did not implement the rule until a court ordered it to in 2018.

But once the regulation was in effect, many companies complied with it. Necessity bred invention, and furniture and wood products makers found glues and binders with no added formaldehyde.

Still, under Trump, the EPA refused to move forward with other efforts that had been underway to tighten regulations of formaldehyde. When he assumed office, the agency was yet again preparing to publish the toxicity report that Jinot had been working on.

One of the new Trump appointments to the EPA was David Dunlap, a chemical engineer who, as the director of environmental regulatory affairs for Koch Industries, had tried to persuade the EPA that formaldehyde doesn’t cause leukemia. Koch’s subsidiary, Georgia-Pacific, made formaldehyde and many products that emit it. (Georgia-Pacific has since sold its chemicals business to Bakelite Synthetics.) At the EPA, Dunlap had authority over the division where Jinot and other scientists were working on the toxicity report.

Ethics rules require federal employees not to participate in matters affecting former clients for two years. Dunlap complied with the law, recusing himself in 2018 from work on formaldehyde, but only after taking part in internal agency discussions about its health effects. He signed his recusal paperwork the same day the EPA killed the toxicity report. Dunlap did not respond to requests for comment.

Imperfect Progress, Inevitable Disruption

This August, the Biden EPA finally managed to carry that report across the finish line, getting it reviewed by other agencies and the White House. For the first time, it also set a threshold to protect people from breathing difficulties caused by formaldehyde, such as increased asthma symptoms and reduced lung function.

In a draft of another key report on formaldehyde released this year, the EPA found that levels of the chemical were high enough to potentially trigger health problems in dozens of scenarios, including workers using lawn and garden products and consumers who might inhale the chemical as it wafts from cleaners, foam seating and flooring. But the agency is required to address risks only if they are deemed “unreasonable.” For many of those risks, the EPA said it wasn’t certain they were unreasonable.

The EPA made the decision after employing a variety of unusual scientific strategies. One involved outdoor air. The EPA first estimated the amount of formaldehyde in the air near some of the country’s biggest polluters. To determine whether those amounts posed an unreasonable risk of harm, the agency compared them to a specific benchmark — the highest concentration of formaldehyde measured by government monitors in outdoor air between 2015 and 2020. EPA records show that peak level was recorded in 2018 in Fontana, California, about 50 miles east of Los Angeles. The EPA concluded the levels near polluting factories would not be unreasonable if they were below this record high, even though local scientists had noted that the Fontana reading didn’t meet their quality control standards, according to documents obtained by ProPublica. Local air quality officials said they didn’t know what caused the temporary spike in the level of formaldehyde near the Fontana monitor.

The fact that an air monitor in Fontana once registered a fluke reading that dwarfs the level of formaldehyde in the air near her home is of little comfort to Rocky Rissler.

A retired teacher, Rissler shares her home in Weld County, Colorado, with her husband, Rick, two horses, one dog and 12 highland cows; she calls it the “Ain’t Right Ranch” — a name that feels increasingly fitting as the number of oil and gas facilities near her home has ballooned in recent years.

The rural area is one of hundreds around the country — many of them in Colorado, New Mexico, North Dakota and West Virginia — where the formaldehyde risk is elevated because of oil and gas production. Gusts of nausea-inducing pollution have become so frequent that Rissler now carries a peppermint spray with her at all times to ease the discomfort. She has frequent headaches, and her asthma has worsened to the point where she’s been hospitalized three times in recent years.

Rissler, who is 60 but says she feels “closer to 99,” has also been diagnosed with chronic bronchitis and chronic obstructive pulmonary disease, or COPD — conditions that have been linked to formaldehyde exposure. Just walking up the slight hill from her horse barn to her front door can leave her winded.

“It feels like a gorilla is sitting on my chest,” she said. And while she used to jog in her youth, “these days, I’m only running if there’s a bear chasing me.”

Under Biden, EPA scientists have been sharply divided over how to gauge all the dangers of formaldehyde. Some employees throughout the agency have been working to strengthen the final health assessment expected later this month. But they are fighting against immense outside pressure.

During the past four years, no fewer than 75 trade groups have pushed back against the EPA’s findings. Among them are the Fertilizer Institute, the Golf Course Superintendents Association of America, the Toy Association, the National Chicken Council, the Asphalt Roofing Manufacturers Association, the Independent Lubricant Manufacturers Association, the RV Industry Association, the Halogenated Solvents Industry Alliance and the American Chemistry Council, which represents more than 190 companies and led the charge. Meanwhile, scientists with ties to the industry are pushing the EPA to abandon its own toxicity calculations and use theirs instead — a move that could seriously weaken future limits on the chemical.

“I’ve seen the industry engage on lots of different risk assessments,” said Tracey Woodruff, a professor and director of the Program on Reproductive Health and the Environment at the University of California, San Francisco. “This one feels next level.”

An EPA spokesperson wrote in an email that the agency’s draft risk evaluation of formaldehyde was “based purely on the best available science.”

The industry’s fortunes have now shifted with Trump’s election.

Despite campaign assurances that he wants “really clean water, really clean air,” Trump is expected to eviscerate dozens of environmental protections, including many that limit pollution in water and air. He will have support from a Republican Congress, where some have long wanted to rewrite environmental laws, including the one regulating chemicals.

Trump has already laid out a plan to require federal agencies to cut 10 rules for every one they introduce, a far more aggressive approach than he took during his last time in the White House, when he rolled back more than 100 environmental rules. And his transition team has floated the idea of relocating the EPA headquarters, a move that would surely cause massive reductions in staff.

According to regulatory experts consulted by ProPublica, the incoming administration could directly interfere with the ongoing review of formaldehyde in several ways. The EPA could simply change its reports on the chemical’s health effects.

“They can just say they’re reopening the risk assessment and take another look at it. There may be some legal hurdles to overcome, but they can certainly try,” said Robert Sussman, an attorney who represents environmental groups and served in the EPA under Presidents Bill Clinton and Barack Obama.

Project 2025, the conservative playbook organized by the Heritage Foundation, calls for the EPA’s structure and mission to be “greatly circumscribed.” Its chapter on the agency specifically recommends the elimination of the division that evaluated the toxicity of formaldehyde and hundreds of other chemicals over the past three decades. Project 2025 also aims to take away funding for research on the health effects of toxic chemicals and open the EPA to industry-funded science.

Trump distanced himself from Project 2025, saying, “I don’t know what the hell it is.” But after the election, some of his surrogates have openly embraced the document, and Trump picked an architect of the conservative plan to fill a key cabinet post.

Last month, Trump announced he had chosen former U.S. Rep. Lee Zeldin of New York to head the EPA. Zeldin could not be reached for comment, and the Trump transition team did not respond to questions about formaldehyde. In his announcement, Trump said Zeldin would deliver deregulatory decisions “to unleash the power of American businesses.”

“The election of Trump is a dream for people who want to deregulate all chemicals,” said Woodruff, the University of California, San Francisco, professor. “We are going to continue to see people get sick and die from this chemical.”

ProPublica is a Pulitzer Prize-winning investigative newsroom. Sign up for The Big Story newsletter to receive stories like this one in your inbox.