Source: Children’s Health Defense

By Michael Schulson

Growing up in Teaneck, New Jersey, with a brother who had severe intellectual disabilities, Linda Birnbaum developed an interest in the human brain.

She was a formidable child: In 1961, as a teenager, Birnbaum obtained 40 laboratory rats and some synthetic thyroid hormones, and ran a controlled study in her family’s basement, tracking how different chemical combinations affected the rodents’ development.

It was the beginning of a lifelong fascination with chemicals and the body. In her 20s, as a newly minted biology Ph.D. with two young children, Birnbaum began researching how rats metabolized different chemicals, including known toxins.

She joined the federal government in 1979 and rose quickly, eventually overseeing high-profile research at the U.S. Environmental Protection Agency (EPA), including early studies of so-called forever chemicals, or per- and polyfluoroalkyl substances (PFAS), in the 1980s.

In 2009, Birnbaum took the helm of the National Institute of Environmental Health Sciences (NIEHS), one of the world’s premier organizations for the study of toxic chemicals. The role made her one of the most influential toxins experts in the country.

Toxins research is not for the faint of heart. Agencies like NIEHS sometimes fund or conduct research suggesting that a specific chemical is associated with a specific health problem.

Such findings can upset people, and in her nearly 11 years leading NIEHS, Birnbaum developed a reputation as a fighter. She oversaw projects that declared formaldehyde to be a human carcinogen and that warned about harms from the chemical bisphenol A, or BPA, which is used in water bottles and food packaging.

In 2018, two Republican members of Congress wrote a letter to one of Birnbaum’s superiors, complaining that she was inappropriately advocating for changes to federal policy.

At the end of her tenure, she told Undark, “I was basically very constrained into what I could say or write.” But since her retirement from NIEHS, in 2019, Birnbaum has been set loose.

Today, she is a prominent voice among a group of scientists who believe that chemical exposures are having a profound effect on Americans’ health, and that regulators — and often their fellow scientists — have neglected to respond.

Some of those scientists, including Birnbaum, argue that environmental causes have contributed to a rise in autism, and that fluoride and cellphone radiation have potential risks to human health — positions that put them at odds with portions of the medical establishment.

In January, Birnbaum and 24 other experts, some of them academic heavyweights, published an article in the New England Journal of Medicine laying out their case for reform.

Over the past 50 years, they wrote, rates of pediatric asthma have tripled, childhood cancers have risen by more than one-third and “neurodevelopmental disorders now affect 1 in 6 children.”

The evidence was growing that chemicals have driven those trends, they wrote, and it was time for “a fundamental revamping of current law” and industry practice.

That sentiment is having a wider cultural moment.

Environmental health has found renewed champions in the coalition of vaccine skeptics, natural food enthusiasts, concerned parents and environmental activists that form the Make America Healthy Again, or MAHA, movement.

Robert F. Kennedy Jr., President Donald Trump’s current secretary of the U.S. Department of Health and Human Services (HHS), and the nominal leader of the movement, has advocated for years about the dangers of environmental toxins, and a MAHA report published earlier this year devotes an entire section to the alleged harms of environmental chemical exposures.

The report was ridiculed in some quarters for its surfeit of citation errors, but that hasn’t stopped state lawmakers from both parties from taking up novel legislative measures on environmental toxins. And the media, too, is now full of new articles about artificial food additives and the health risks of plastics.

The result is an unexpected, sometimes-strained alignment between the subset of the Trump coalition that frets about pesticides, and environmental health experts who, like Birnbaum, have come to see chemical exposures as a true public health emergency, one that requires far more action from scientific institutions, physicians and policymakers.

Those two groups differ sharply on key issues, and Birnbaum has described feeling uneasy with that alignment. But, she told Undark, “I think we’re foolish not to take advantage of an opportunity if it happens.”

How that vision will weather the coming years, though, remains unclear. The political landscape is complicated: Even as the Trump administration pays more attention to toxins, it has also proposed slashing the budget of NIEHS and authorized massive cuts and reorganizations at the EPA, which regulates pesticides and many other chemicals.

And some of the exposures that Kennedy worries about — specifically, an unproven, highly speculative link between vaccine additives and autism — have little to no scientific evidence behind them, straining any alignment between public health experts and the MAHA world.

Meanwhile, some experts within the medical research community argue that, in some cases, toxin researchers have gone too far, making dire warnings based on thin evidence.

All of which begs the question: Is the vision that Birnbaum and other scientists have laid out really ready for, or even worthy of, a rare moment of traction — or will it founder under the weight of disputed evidence, cross-cutting interests and hostile politics?

Around 350,000 human-made chemicals exist on global registries, according to one 2020 estimate. What are those chemicals doing to human health? The question is not new, nor is it always simple to answer.

But at certain moments in American history, it has seized public attention. In 1962, when Rachel Carson published “Silent Spring,” the landmark book about chemical effects on the natural world, it sparked a public outcry about pesticide use.

In 1970, a Republican president, Richard Nixon, asked Congress to approve a proposal to establish the EPA. At the time, a young pediatrician named Herb Needleman was already documenting the effects of lead exposure on his patients in Philadelphia.

Swimming against fierce opposition from industry, Needleman and others demonstrated that lead was affecting children’s health and trimming points from their IQs, and the researchers eventually won major regulatory battles, including moves to phase out lead in gasoline, a transition that was completed in the 1990s.

Another landmark came in 1993, when the National Research Council released a report calling for tighter scrutiny of pesticides’ effects on children.

“The laws and policies that were then enforced in the United States were not doing a very good job of protecting kids against chemicals,” said Philip Landrigan, now a pediatrician at Boston College, who led the team that produced the report.

Synthetic chemicals were tested — when they were tested at all — to determine if average levels of exposure were safe for the general population, rather than children specifically. But children’s smaller, developing bodies, the report concluded, can be uniquely vulnerable to their effects.

The report spurred new federal pesticide regulations, and it also helped bring a flood of new funding into the field of environmental health research.

The attention reflected a broader disquiet about the state of children’s health, according to James Tabery, a scholar at the University of Utah who has written about the history of toxins research.

“It always used to be the case that when the new generation came along, we could reliably count on them living longer and being healthier than the generation before them,” Tabery told Undark.

“And it looked like, starting around the ’80s or ’90s, that was shifting.”

Rates of obesity, asthma, allergies and diabetes were all rising in children.

“There was this kind of awareness of, ‘Hey, something is wrong here. We’re not getting it right,’” Tabery said.

Researchers responded with new studies on a range of environmental exposures. They also began to develop new tools to evaluate data — in particular, systematic reviews, which comb through multiple, sometimes hundreds, of studies in order to draw big-picture conclusions about the direction of evidence on a particular question.

Not all those research efforts flourished. As senior contributor Charles Schmidt has chronicled for Undark, a multiyear federal project called the National Children’s Study fizzled in 2014.

In his 2023 book “Tyranny of the Gene: Personalized Medicine and Its Threat to Public Health,” Tabery describes a broader underinvestment in research on the environmental causes of chronic disease.

Policymakers and companies, he argues, focused their resources on flashy genetics studies and cures for diseases. They paid far less attention to preventing diseases by identifying and eliminating the toxins that caused them in the first place — perhaps because such science was unprofitable, unsexy and unpopular among pharmaceutical industry leaders and some policymakers.

Still, by the 2010s, some scientists like Landrigan believed the evidence was clear enough that food additives, pesticides and other manufactured chemicals were a significant cause of chronic disease — in both children and adults — to warrant a dramatic overhaul of U.S. regulations.

That perspective found allies outside the scientific mainstream, some of whom would soon reach positions of massive political influence.

Zen Honeycutt, a prominent MAHA activist, said she started thinking about toxin exposures after one of her three sons developed life-threatening allergies.

“It’s the four As: It’s the allergies, the autoimmune issues, the asthma, and the autism,” she told Undark.

Reported global rates of all those conditions are significantly higher than they once were, and although the reason is a matter of debate, Honeycutt and others think chemicals are to blame. Firsthand experience with these conditions can, for some people, prompt a kind of political awakening.

“Once a child gets sick, or a person gets sick, they start looking at why that could be the case,” Honeycutt said.

Some of them turn to toxins: People in the MAHA world — like many scientists — believe that the regulatory system does too little to vet the safety of chemicals widely used in foods, packaging, plastics and more.

“Most of us,” said Honeycutt, “feel deeply betrayed by the government that is supposed to be protecting us.”

Honeycutt, who lives in the mountains of western North Carolina, has directed much of her activism toward the herbicide glyphosate, which is considered a probable carcinogen by some scientists, and she often cites environmental health research linking the chemical to a range of ill health effects.

In 2013, she launched Moms Across America, an organization that has advocated for bans on many pesticides and on genetically modified crops, which are often associated with high glyphosate use. (The organization also sells pricey detox supplements and other natural health products, which are not evaluated by the U.S. Food and Drug Administration (FDA); Honeycutt says the proceeds go back into the nonprofit.)

Honeycutt met Kennedy some 10 years ago, she recalled. For years, Moms Across America listed him as an adviser to the group, and she has become a prominent speaker and advocate within the MAHA movement.

Last year, Kennedy dropped an independent presidential campaign and endorsed Trump. Days after Trump’s election victory, the president-elect nominated Kennedy to be secretary of HHS, which would put him in charge of the FDA and the National Institutes of Health (NIH), including Birnbaum’s old agency, NIEHS.

Since arriving in office, Kennedy has continued to promote some of the causes that Birnbaum and others had raised alarms on: He has made moves to limit fluoride in water, eliminate certain artificial food dyes, and increase federal scrutiny of childhood chemical exposures.

The alliance between MAHA and Trump’s Make America Great Again movement has sometimes been strained. Kennedy does not oversee the EPA, and activists, including Honeycutt, have objected to the appointment of industry-friendly officials to the agency, which plays a key role in regulating pesticides and many other chemicals.

Over the summer, a proposal that would weaken pesticide labeling and oversight led to an emergency meeting among MAHA activists. Some publicly questioned whether the coalition could hold.

Failing to act on pesticides, Honeycutt told Undark in late October, could have political consequences for some Republican lawmakers in next year’s midterms, and she described herself as “furious” about a decision to omit some pesticides from a major MAHA report.

But she remains supportive of Kennedy: “I do understand that he is facing some extreme opposition, and I think that better progress will be made further down the road,” she said. “I just may have to be a little bit more patient than I would like to be.”

The Trump administration has also proposed cutting scientific research budgets in ways that could affect toxins research. The administration has taken steps to restructure the EPA, dismantling a key research division and reassigning or laying off many staffers.

And Kennedy has overseen layoffs — and may soon implement budget cuts — across the NIH, including at NIEHS.

The changes have put environmental health researchers in tricky positions.

Bruce Lanphear, a Canadian-American researcher at Simon Fraser University who has spent years studying lead exposures, shares some basic goals with Kennedy and his allies. He wants NIH to spend far more of its budget on research to prevent chronic disease.

He thinks toxins are driving a rise in chronic illnesses, including autism.

And he described being caught in the middle of polarized camps — MAHA world figures who endorse ideas (such as those about vaccines) that he does not think are grounded in sound science, and other public health officials who, he thinks, “fall into this tribalism” and dismiss real research on toxins, out of what he describes as a reflexive opposition to MAHA.

Even as some researchers hope Kennedy’s platform will bring changes to chemical oversight, they also despair at what many describe as a dismantling of scientific infrastructure.

In a March interview with Undark, as layoffs and funding freezes jolted NIH, Birnbaum described a sense of chaos. It was as if someone had taken a chainsaw to her former agency, she said. “The damage that is done to morale is huge and takes years to repair.”

How do MAHA activists square research cuts with their goals? Honeycutt questioned whether more research, at this point, was even necessary to advance the broader cause of limiting chemical exposures.

While there’s still some scientific debate over whether the herbicide glyphosate, for example, can cause chronic health effects at typical levels of exposure, Honeycutt thinks the research is definitive enough.

“I don’t need any more scientific studies actually showing that glyphosate is harmful,” she said.

Such work, she argued, could even play into industry goals: “That’s all just a delaying tactic which is going to allow farmers to spray more of these toxins on our food supply.”

At the same time, not all scientists agree with how Birnbaum and some other prominent environmental health scientists interpret the data.

Some of the debate revolves around how to understand the rise of certain chronic conditions. Researchers are divided over how much of the rise in behavioral diagnoses like autism reflects actual material changes in children’s brains, versus changes in how doctors issue diagnoses.

Even when scientists may agree that there’s some environmental cause, they may disagree over to what extent it comes from a toxins exposure specifically, in addition to other causes like dietary changes or stress.

Lurking in the background of these debates is another, slow-burning question: How reliably can existing tools link a specific chemical to a specific harm, like an increased risk of cancer or an average drop in IQ?

Occasionally, the evidence is stark: The medication thalidomide, for example, when taken during pregnancy, consistently and dramatically leads to congenital disorders.

But if a chemical raises a person’s chances of, say, developing a certain cancer as an adult by 10%, connecting that fetal exposure to cancer cases 40 years later may be extraordinarily difficult.

Environmental health researchers have a few key tools to search for those patterns. They can test the effects of chemicals on cell or tissue cultures in the lab. They also have animal studies, in which animals are exposed to doses of chemicals, then examined for health effects.

These experiments can show a direct biological effect from a chemical, but laboratory animals are markedly different from humans, so the work doesn’t explicitly prove how the chemicals relate to human health.

Another key approach involves observational studies in humans, in which researchers collect vast pools of data and then look for associations between exposure to a certain chemical and certain health outcomes.

If, for example, studies consistently find that people exposed to chemical X have a higher chance of getting cancer, and they can’t find some other variable to explain the connection — called a confounder — then chemical X may be labeled a likely carcinogen.

Such studies helped discover the now-widely-accepted finding that lead exposure harms developing brains, and that smoking causes lung cancer.

It also underlies current concerns about many chemicals — including PFAS, BPA and glyphosate — and it forms a key foundation for the current push to rethink toxins regulation.

Large observational studies can be plagued by bias, and two other fields that rely heavily on them have suffered major crises of evidence in the past two decades. One is the field of nutritional epidemiology, which seeks to connect the consumption of certain foods or nutrients to certain health outcomes.

The field has suffered repeated issues with replicability. Similarly, the field of candidate gene studies, which aimed to find a link between certain genes and certain attributes or outcomes, was hot in the 2000s, but foundered, with some of its headline results failing to replicate.

There are reasons, some experts say, to fear similar issues are lurking in the environmental health literature.

“There’s a growing body of evidence from psychology and economics that suggests that the results of observational studies are highly, highly contingent on the analytic choices that investigators make,” said Dena Zeraatkar, an expert in medical research methodology at McMaster University in Canada.

Zeraatkar’s work focuses on issues with nutrition research, but the same concerns, she said, apply to environmental health, which relies on the same basic tools.

“While there has been some effort made to improve the rigor of observational research, both in nutrition and environmental sciences, not much really has materialized, and it’s still the same approach where people just correlate one exposure with one outcome and selectively report the analyses, the results of which are confounded,” she said.

“And people use that and report on it and use it to inform recommendations, making strong recommendations based on very, very weak evidence.”

Landrigan pushed back against those concerns, which he described as an overgeneralization, and which he said echoed industry propaganda that sought to undermine work on the link between tobacco and lung cancer. (Zeraatkar said she does not receive industry funding.)

“There’s some people in the clinical research world who just don’t understand epidemiology and have tended to dismiss it, which I think is profoundly wrong,” he said.

He also questioned the analogy to nutritional epidemiology, saying that experts in environmental toxins have better tools to measure how much their research subjects have been exposed to a particular chemical. (In the past, Landrigan has served as a paid expert witness in cases related to childhood lead poisoning.)

Similar concerns have also led to fissures within the environmental health field, where some researchers feel that their colleagues sometimes overstate results — often unconsciously, but in response to clear incentives.

“When scientific research focuses on a potential hazard that may affect the population at large, researchers themselves, regulatory agencies, advocacy groups, and journalists reporting on the story tend to emphasize what appear to be positive findings, even when the results are inconsistent, the risks may be small in magnitude and uncertain, and other, more important factors may be ignored,” writes cancer epidemiologist Geoffrey Kabat in a 2016 book, “Getting Risk Right.” (Kabat has accepted funding from the tobacco industry, and his work has, at times, inspired controversy.)

In an email to Undark, Kabat singled out the debate over BPA, which was catalyzed by NIEHS-funded research and reviews during Linda Birnbaum’s tenure at the agency.

The studies linking BPA to outcomes like endocrine system damage, he argues, were overstated by prominent scientists. Kabat’s book quotes an email from a longtime chemist in the FDA’s National Center for Toxicological Research, Daniel Doerge, who described the BPA work as presenting “a distorted version of reality.”

“When such a self-interested group gains access to the levers of a large national funding agency, the chaos can continue for an extended time,” Doerge warned.

“Kabat never saw an environmental chemical that he thought was a problem,” Birnbaum wrote in an email to Undark. (She also described “lots of bad blood” between Doerge and some NIEHS staff.)

And when a range of studies, from a range of places, using a range of methods, consistently show a certain result, she said, it presents a strong signal.

Some of those disagreements are less over the substance of the science and more over how much evidence needs to accumulate before officials should issue a warning or roll out new regulations.

Birnbaum described herself as following a precautionary principle — which holds that one should act upon finding concerning evidence, even when there’s uncertainty.

There are divides among environmental health researchers over how precautionary an approach to take.

Christopher Sellers, an environmental historian at Stony Brook University, said that in the past 20 or 30 years, much of the environmental health field has moved in the direction of researchers like Birnbaum:

“Within the professional environmental public health community, there’s been a sort of a shift toward — there’s been a faction that has become more precautionist in terms of ‘We should make that move.’”

Others have viewed that approach with some trepidation.

David Savitz, a professor emeritus of epidemiology at Brown University and a former president of the Society for Epidemiologic Research, expressed concern about people in the field “being overly enthusiastic about really uncertain findings and really pushing them in an ideological sense.” (Last year, Savitz testified as a paid expert witness for the federal government in a legal case alleging that the EPA was not doing enough to address potential harms from fluoride.)

Savitz has done extensive research on PFAS risks and pesticides, and he wrote in an email to Undark, “I recognize the need to be vigilant” about toxins.

But, he continued, “I don’t believe that such exposures are a major influence on public health overall.”

He divides with many of his colleagues over what to do when it’s unclear what, precisely, may be driving a specific harm. Research about the harms of lead, he suggested — a slam dunk result — is an outlier among research on toxins that affect brain development.

“In many of these cases, there’s a huge array of non-definitive research,” he said.

Some of his colleagues would “say it’s persuasive enough to act. And I would say that I’m not convinced that it’s, you know, really has that level of clarity.”

“Then it gets into what I do think legitimately is ideological or political: How much evidence do you need?” Savitz said.

At stake, he noted, are the economic costs of banning a chemical that’s not causing harm — and deeper questions about the credibility of the field itself if it raises a false alarm.

At a time when millions of Americans suffer from serious chronic health conditions, and when many chemicals go unstudied, those questions can feel academic. Recently, some prominent toxins researchers have taken steps toward a more organized response.

This spring, after Birnbaum and other scientists published their prominent letter in the New England Journal of Medicine, some of the authors helped form a group, the Institute for Preventive Health.

The organization is led by Landrigan, the Boston College pediatrician, with Birnbaum as a senior adviser. One of the co-founders, Anne Robertson, is a relative of the deceased tobacco magnate R.J. Reynolds and an environmental and children’s health advocate; another is Henry Rowlands, who founded an organization that helps people test for toxins in their bodies and food.

So far, the group’s launch has been quiet, with little more than a website and some initial meetings. The long-term goal, said Rowlands, is not to campaign for specific policies, but to provide what he described as an “independent institute of experts that can guide industry and policymakers over time.”

The group will issue white papers, for example, and provide the kind of frank safety analysis that, Rowlands argues, government agencies have sometimes failed to perform.

Whether Kennedy and his team will take meaningful steps to study and reduce environmental chemical exposures remains to be seen.

During a conversation in March, Landrigan sounded concerned about changes at the EPA, but cautiously optimistic that Kennedy could advance policies that would address chemical exposures.

By August, he sounded less hopeful. “He’s talked a good game,” Landrigan said, “but he hasn’t delivered.”

Birnbaum — who has described an alliance with Kennedy as a “dance with the devil” — was similarly unimpressed. But, she said during a conversation in September, it’s often public pressure, rather than regulatory action, that ultimately yields changes.

“I think people are concerned about the health of their children, maybe more so than they were,” she said. “And if that’s true, that is a success of the MAHA agenda to realize that our children aren’t as healthy as they should be.”

Originally published by Undark.

Michael Schulson is a contributing editor for Undark. His work has also been published by Aeon, NPR, Pacific Standard, Scientific American, Slate and Wired, among other publications.