US Department of Health and Human Services (HHS) Secretary Robert F. Kennedy Jr.’s testimony before Congress last week offered a revealing glimpse into how ideology has overtaken evidence at the nation’s top health agency. In a single exchange about mercury exposure, Kennedy tried to evade accountability for the Trump administration’s rollback of pollution limits that protect children’s neurologic development while reviving long-debunked fears about vaccine preservatives, exposing both the contradictions at the heart of federal vaccine policy and the uneasy fit between the Make America Healthy Again (MAHA) movement and the administration’s broader environmental agenda.
At the hearing, US Rep. Josh Harder, who represents a Stockton, Calif.-area district, reminded Kennedy, who was an environmental advocate before he became associated with anti-vaccine efforts, of his previous advocacy for limiting mercury emissions from power plants. He recalled that when the first Trump administration tried to roll back mercury runoff limits, Kennedy personally attended the hearing to express his opposition.
Kennedy’s previous activism against mercury emissions was well-founded. Coal-fired power plants are a major, human-caused source of mercury emissions. Released mercury deposits into water and soil, where microbes convert part of it into methylmercury, the form that bioaccumulates in fish and is known to be neurotoxic, especially during fetal development.
What, therefore, Harder asked, did Kennedy make of the Trump administration’s decision to restore older mercury pollution limits that let some coal plants emit substantially more methylmercury-forming pollution—up to about two-thirds more for plants powered by the lowest-grade coal?
A puzzling dodge
Though Kennedy bristled at the question, he didn’t defend the administration’s actions. The representative, he said, needed to ask the Environmental Protection Agency (EPA). His HHS had nothing to do with it.
The problem with Kennedy’s answer is that a major EPA rule affecting mercury emissions does not simply appear without interagency review, which the secretary must have known. Policies with significant public health implications typically move through a formal process that includes consultation across the federal government
For Kennedy to suggest he was unaware is difficult to reconcile with how the federal government typically works.
On December 23, 2025, EPA submitted a draft of the final action to the Office of Management and Budget (OMB) for interagency review under Executive Order 12866.
That matters because the review is handled through OMB’s Office of Information and Regulatory Affairs (OIRA), where major rules are circulated across relevant federal agencies for comment.
For Kennedy to suggest he was unaware is difficult to reconcile with how the federal government typically works, not to mention the fact that the administration’s plan to roll back the mercury emissions standards had been public since last spring.
The more troubling move: Misleading about vaccines and mercury
But the more troubling part of the exchange with Harder was not the dodge. It was Kennedy’s misleading pivot.
The secretary tried to defend his environmentalist bona fides by citing HHS’s withholding of US funding from Gavi, the Vaccine Alliance, because some vaccines it supports still use thimerosal, a preservative containing ethylmercury, which prevents contamination in multidose vials. He framed this as a principled stand against mercury exposure.
In truth, it was a case study in how ideology—not evidence—is driving federal health leadership.
Thimerosal contains ethylmercury, not methylmercury. That distinction matters. Ethylmercury is processed and cleared from the body much faster and does not accumulate the same way. The Centers for Disease Control and Prevention has long explained this difference clearly, and the scientific evidence has been consistent for decades: Thimerosal is not linked to autism or other neurodevelopmental disorders.
Kennedy has a history of conflating the two mercury-containing compounds.
In 2005, he wrote “Deadly Immunity,” an article published in Rolling Stone and on Salon that argued thimerosal was linked to autism. Both publications later distanced themselves from the piece, because the data were inaccurate, selectively presented, or taken out of context. In 2014, he published a book advancing similar claims, which drew similarly sharp criticism from scientists and physicians for misstating evidence and exaggerating risk.
Kennedy has a history of conflating the two mercury-containing compounds.
The Institute of Medicine—now the National Academy of Medicine—reviewed more than 200 studies and found that the evidence favored rejection of a causal relationship between thimerosal-containing vaccines and autism. Large epidemiologic studies in the United States and internationally reached the same conclusion. When thimerosal was removed from nearly all routine childhood vaccines in the United States more than two decades ago—a precautionary step taken to maintain public confidence, not because of demonstrated harm—autism rates continued to rise, further undercutting claims of causation.
And yet Kennedy is now conditioning global vaccine financing on a claim that has already been exhaustively tested and rejected.
This matters because Gavi is one of the world’s most important vaccine delivery systems, helping protect millions of children from diseases like diphtheria, tetanus, and hepatitis B. Suspending support over a disproven fear about thimerosal does not protect children. It puts them at greater risk.
At the same time, downplaying increased industrial mercury exposure while elevating long-debunked claims about vaccine preservatives sends a dangerous message: that public health decisions are no longer being made according to actual risk.
Selective concern disguised as science
Americans can handle hard truths. What they should not have to tolerate is selective concern dressed up as science.
If mercury exposure is the concern, then policy should focus first on the forms of mercury known to cause harm, and on the communities most vulnerable to that harm. If vaccine safety is the concern, then decisions should reflect the overwhelming evidence, not recycled claims that are unsupported by evidence.
Honesty requires saying plainly that methylmercury pollution and ethylmercury vaccine preservatives are not the same thing.
Public health depends on trust. Trust depends on honesty. And honesty requires saying plainly that methylmercury pollution and ethylmercury vaccine preservatives are not the same thing.
When the nation’s top health official pretends otherwise—or claims ignorance when it is politically convenient, so as not to raise the ire of MAHA activists—it is not public health leadership. It is yet another example of politics and ideology trumping evidence.
