MIT’s Undark magazine describes itself as a publication that “will explore science … as a frequently wondrous, sometimes contentious, and occasionally troubling byproduct of human culture.” Its name refers to a “radium-based industrial and consumer product … that was both awe-inspiring and, as scientists would only later prove, toxic and deadly.” In a recent article for the magazine, Michael Schulson offers a tendentious account of what is known about exposure to toxic substances in the environment, and then places his review in the context of the Trump administration’s Make America Healthy Again (MAHA) agenda.

Last July, Schulson contacted me and asked for my perspective on “the growing public attention to some parts of the environmental epidemiology and toxicology research fields—visible in the claims of the MAHA movement, as well as efforts like a new children’s health initiative led by Philip Landrigan, Linda Birnbaum, and others.” In a series of emails, I provided some thoughts on important issues to consider when reading about this topic. I mentioned “endocrine disruption” as a good example of the challenges associated with assessing low-level environmental exposures. And I pointed him to a chapter in my book Getting Risk Right: Understanding the Science of Elusive Health Risks that gives a detailed treatment of this question. I also offered to suggest further articles that might address the issues that interested him.

Here is an excerpt from an email I sent Schulson on 15 July 2025:

There are good examples of exposures that looked important/scary initially but that, as larger and better studies were done, turned out to be nothing. This happened with DDT and breast cancer, with BPA and estrogenic effects, and with glyphosate (Roundup) and non-Hodgkin’s lymphoma, and with other pesticides (atrazine, I believe). A more recent topic of interest is PFAS, and I’m not up on this. But this too appears difficult to get a handle on.

However, when I read the published article, I found that Schulson gives an unsatisfactory account of a complicated story. The article opens by focussing on Linda Birnbaum—head of the National Institute of Environmental Health Sciences (NIEHS) from 2009 to 2019—and then goes on to quote statements from roughly a dozen researchers and others. Unfortunately, the use of personalities to represent different points-of-view is no substitute for a careful exploration of the underlying questions. In addition, Schulson’s apparent bias towards certain informants appears to undermine his objectivity.

Birnbaum is clearly an important figure, but Schulson treats her as a hero and his account verges on hagiography. During her tenure at NIEHS, Birnbaum was instrumental in funding a large number of studies of the chemical bisphenol-A (BPA). BPA was introduced in the 1960s to line food containers to prevent spoilage, and it has since been used in a wide array of consumer products. In the early 2000s, BPA became the focus of health concerns, particularly about its potential to leach out of food containers and baby bottles. Some early studies appeared to show that the compound could have adverse effects, ranging from effects on sexual and neurobehavioural development to cancer. However, in 2010, the US Food and Drug Administration issued a report restating its position that BPA was safe and “posed ‘negligible’ or ‘minimal’ concern for most adults and ‘is not proven to harm children or adults.’”

To cut a long story short, the NIEHS under Birnbaum got caught up in an “availability cascade”—a self-reinforcing process of collective belief-formation in which a claim triggers a chain reaction of repetition that makes the claim seem increasing plausible as its prevalence in public discourse grows. This is known, more colloquially, as a “bandwagon effect.” Whichever term one uses, it describes the view of many academic scientists studying BPA. They came to believe that anomalous findings—often obtained from small studies and tests with ambiguous results—provided serious evidence of adverse effects, even at low doses. These researchers were influenced by the “endocrine disruption hypothesis” pioneered by the toxicologist Theo Colborn in the 1990s and popularised in her bestselling book, Our Stolen Future. Since then, the whole basis of the endocrine disruption hypothesis has been robustly challenged by other researchers.

The steady stream of alarming results prominently reported in the media led to campaigns to eliminate BPA in baby bottles and other consumer products. There were even calls to ban it entirely. At the same time, due to the availability cascade, each new disturbing finding generated increased public concern and calls for further studies, creating a self-perpetuating cycle. Through repetition and the massive publicity that each new finding received, the belief that BPA was causing harm became a conviction in many minds. In response to this apparent crisis, the National Institutes of Health spent US$172.7M on BPA between 2010 and 2014, approximately seventy percent of which was awarded by the NIEHS in Birnbaum’s early years at the institute.

However, another group of highly qualified government scientists following “good laboratory practices” based on regulatory guidelines received less attention. In a series of studies, Daniel Doerge (an analytical chemist), Justin Teeguarden (a toxicologist), and colleagues found that, contrary to the concerns raised by the academic studies, levels of BPA in the human diet are very low, little BPA is absorbed from food, and what is absorbed is efficiently metabolised and almost totally excreted in the urine. BPA was virtually undetectable in the blood.

In an attempt to resolve the disagreement between the two camps, the NIEHS and the FDA agreed to conduct a study in 2012 titled CLARITY-BPA. The centrepiece of that paper was a two-year “chronic exposure” study conducted by scientists at the FDA’s Center for Toxicological Research, in which 3,500 rats were exposed to a wide range of BPA doses. This was the largest study ever conducted on BPA, and FDA researchers performed extensive pathological evaluation to detect effects on organ structure and function, sexual development, and evidence of cancer.

In addition, thirteen projects from academic grantees were added on to the core study to test specific hypotheses. The major strengths of this approach were:

1. Both components of the study involved identical BPA exposure conditions, which were overseen at the same facility in the FDA’s National Center for Toxicological Research.
2. Grantees received blinded core study samples, which means they did not know whether samples had been dosed with BPA or by how much, in order to minimise the potential for bias.

The core study was conducted from 2012 to 2013, and grantees received their tissue samples in 2013 and 2014, so most of the academic studies have now been completed and published.

One might think that this unusual effort would have gone some way towards narrowing the stark division between the two camps. However, this is not the case. On 23 February 2018, FDA commissioner Scott Gottlieb and deputy commissioner Stephen Ostroff issued a statement on the not-yet-peer-reviewed results of the core study. The FDA, they wrote, “continues to conclude that BPA is safe for its currently authorized uses.” Academic researchers, including some CLARITY grantees, criticised the FDA’s press release as premature and incomplete, charging that the agency was ignoring substantial evidence from animal studies documenting adverse effects of BPA exposure.

At a meeting in 2018, interested parties had the opportunity to comment on the 200-page draft report summarising the results of the core study. A number of academic grantees criticised certain technical aspects of the study, including the route of administration and the use of “historical” control animals in certain analyses. Such criticisms, five years after the completion of the study, did not bode well for the prospects of reaching a meeting of the minds. However, a panel of independent scientists convened by the National Toxicology Program reviewed the draft report and generally endorsed the study’s design and execution, as well as FDA’s interpretation of the results. Their recommendations to improve the report were incorporated into the final report.

The results of the core study were released on 28 September 2018 by the US National Toxicology Program. In a webinar, the study’s principal investigator, Barry Duclos, discussed the results in detail and concluded that “BPA did not elicit clear, biologically plausible, adverse effects” at levels even remotely close to typical consumer exposure levels. Plans for the two groups of researchers to issue a joint report never materialised, however, and their uneasy collaboration points up the vast gulf between regulatory scientists and academic scientists. The former rely on widely accepted guidelines for conducting and reporting toxicological testing that are endorsed by the Organisation for Economic Cooperation and Development (OECD). The latter believe that cutting-edge methods like gene expression can detect subtle effects missed by the older approach.

In the wake of the CLARITY-BPA study, new findings continue to be published showing harmful effects of exposure to BPA on reproductive health, cancer, and other outcomes. To make the situation even more complicated, BPA has been replaced in certain products (e.g., baby bottles) by compounds about which less is known, and which may carry their own risk. The problem is that results of exploratory academic research are often difficult to interpret and their relevance to human exposure is unclear. Many results have not been replicated. One critic of this body of research on BPA characterised it to me as, “a land of one-sided comparisons, confirmation bias, post-hoc reasoning, ‘any finding at any dose’ effects untethered from matters of precursor lesions, internal dosimetry, and mechanism.”   

We know that many published research findings are wrong, and this is particularly true of studies examining the effects of low-level physical/chemical environmental exposures. However, published findings suggesting that a trace exposure may pose a risk to the general population can be counted on to receive inordinate attention from the media and the public and to feed demands for stricter regulation, regardless of the studies’ quality. When we assess the validity of studies, we should acknowledge an asymmetry between results that report an association with a risk factor and those that fail to find an association. First, findings of an association receive more attention than findings of no association, even when the latter come from higher-quality studies. Second, one can never prove that some exposure is entirely safe. Third, even scientists are susceptible to these biases. 

Schulson did not follow up on the readings I offered to recommend. Instead, he reproduces brief quotations from me and Daniel Doerge of the FDA based on email exchanges. He then proceeds to quote Birnbaum’s unflattering characterisation of the two of us: “‘Kabat never saw an environmental chemical that he thought was a problem,’ Birnbaum wrote in an email to Undark.” She also describes “lots of bad blood” between Doerge and some NIEHS staff. Had Birnbaum read Getting Risk Right, she would have seen that I devote whole chapters to environmental risks, including Chinese herbs (Aristolochia) and certain dietary supplements, diethylstilbestrol, and the human papillomavirus. Birnbaum might also have been interested in Box 2.1 in my previous book Hyping Health Risks: Environmental Hazards and the Science of Epidemiology, which lists a number of environmental chemical risks under “a partial list of major achievements of epidemiology.” Apparently, for Birnbaum, it is enough to question whether the evidence supports a touted risk to be branded a traitor to the field.

Schulson lets Birnbaum’s broad-brush dismissal of Doerge—and implicitly of the high-quality work done by the FDA’s National Center for Toxicological Research—pass unchallenged. Note that this is coming from the person who was the head of the NIEHS during the period when CLARITY-BPA was carried out. It is hard to believe that, seven years after the publication of the final report from the core study, Birnbaum still cannot acknowledge the findings from the NCTR or admit that she may have been misled by the academic studies. (She is likely unaware that both Doerge and Teeguarden have received awards for the state-of-the-art analytical chemistry techniques they used to measure BPA levels in test subjects and the estrogenicity and metabolism of BPA.) By accepting Birnbaum’s opinion as the final word, Schulson manages to completely ignore the highly instructive story of the CLARITY-BPA study and its outcome, as well as the whole controversy surrounding endocrine disruption.

I have recapitulated the BPA story at some length because it provides an understanding of the difficulties and professional conflicts that arise when researchers study low-level exposures and their selective results receive undue attention. As Schulson noted in his first email to me, many of the issues that arise regarding BPA are pertinent to “a new Children’s Health Initiative led by Philip Landrigan, Linda Birnbaum and others.” This project, for which he provided a link to only the vaguest supporting information, harks back to the National Children’s Study (NCS). The NCS was an ambitious longitudinal study of the effects of environmental factors on child health and development. It was to track 100,000 American children from before birth until they reached the age of 21 by collecting detailed data and biological and environmental samples. After fourteen years of planning and pilot studies at a cost of US$1.3 billion, the study was cancelled in 2014. This story is a testament to the challenge of conducting studies to get at the causes of conditions like allergies, ADHD, and autism in children.

There is an implicit tension between the views of Birnbaum and Philip Landrigan, on one hand, and those of epidemiologist David Savitz and several other scientists interviewed by Schulson, on the other. The former seem to be confident that valuable new insights are likely to come from studies like the NCS, whereas Savitz and others are much more sceptical. But Schulson simply ignores this tension, which is the key to understanding the question he is skirting. And when he discusses RFK’s Make America Healthy Again (MAHA) agenda, Schulson unwisely devotes space to the opinions of MAHA activist Zen Honeycutt regarding pesticides:

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.

Honeycutt leads Moms Across America, which sells alternative-medicine supplements and products like “Vaccine Detox Herbal Extract” and “LifeWave Frequency Patches” on its website. In fact, there is very little scientific debate about the health effects of glyphosate. Seventeen national and international health agencies—including the US EPA, Health Canada, and the European Food Safety Authority—have examined the health effects of glyphosate and found it to be safe. Only one agency—the International Agency for Research on Cancer (IARC)—has designated glyphosate to be a “probable carcinogen”; however, IARC’s determination has been shown to be based on selectively interpreting the available evidence (see here and here).

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While referring to different points-of-view on environmental pollution and some prominent candidate pollutants, it is telling that Schulson never mentions what has been learned from occupational studies, which often entail relatively heavy exposure. Nor does he mention dose-response relationship, toxicology (“the dose makes the poison”), or the work of Bruce Ames showing that natural pesticides in foods like cabbage account for the bulk (99.99 percent) of our pesticide exposure.

Finally, Undark’s policy regarding conflicts-of-interest is positively bizarre and of a piece with the article’s general lack of attention to detail, coherence, or context. “Kabat,” Schulson informs his readers, “has accepted funding from the tobacco industry, and his work has, at times, inspired controversy.” When he brought up the question of conflicts-of-interest with me in an email, I wrote him a detailed reply describing my career and sources of support, none of which was included in his article. His readers deserve better.