Four years into the U.S. Food and Drug Administration’s review of Zyn nicotine pouches, and not long before the agency approved them for sale, an FDA toxicologist ran some informal tests in her kitchen that led her to question whether the agency truly understood the addictive product it was about to green-light.
Christy Leppanen worked for the FDA’s Center for Tobacco Products, where she led a project examining the potential for microplastics exposure. A scientist who had worked on an environmental assessment of Zyn had repeatedly told her that the nicotine pouches melt in the mouth. But during a public health conference in late 2024, Leppanen said, she talked to an academic who reinforced her understanding that they don’t.
The FDA allowed stores to sell Zyn while it evaluated the product. On the way home from the conference, Leppanen said, she went to the Mall of America, bought a can of menthol-flavored Zyn, and took it home. She put the pouches in her mouth. She soaked them in a cup with saliva. She heated them in the microwave, crushed them, and sucked them. They did not dissolve.
Over the course of the next several weeks, Leppanen said, she pushed her colleagues to consider possible health and environmental risks from the pouch material. She was repeatedly rebuffed.
Now she has accused the FDA of authorizing one of the fastest-growing nicotine products in America without knowing what the pouch itself is made of.
In interviews, emails to federal officials, and recordings reviewed by The Examination, Leppanen has alleged that the FDA lacked critical facts about the material of Zyn pouches, decided not to seek additional information from the manufacturer, Philip Morris International, and nevertheless concluded the material was unlikely to harm consumers.
“Fundamentally, we did not do a proper assessment,” Leppanen said. “People believe the FDA is doing more than it is.”
To top it off, when the FDA announced its approval of Zyn, it published a document saying Leppanen had signed off on the environmental review — a mistake that the agency quickly acknowledged but didn’t publicly correct for months.
Leppanen and several scientists told The Examination that the pouches could shed tiny particles during use, which could be absorbed by users. Research on microplastics indicates they accumulate in human organs, and evidence is emerging that this could be harmful.
“With the increasing body of information about microplastics exposure and how they cross into the bloodstream from the gut, we just needed to know what those materials are,” Leppanen said.
The tobacco industry is championing pouches and e-cigarettes, which contain nicotine and flavorings, because they deliver a buzz without inhaling harmful cigarette smoke. The U.S. market for nicotine pouches is estimated to increase by 37% this year to $6.8 billion, according to the market research firm TobaccoIntelligence.
New nicotine products such as pouches and vapes must be authorized for sale by the FDA, which examines whether they are “appropriate for the protection of public health.” The agency weighs the potential harm to public health, such as young nonsmokers using these addictive products, against the potential benefit: helping adult smokers move away from cigarettes.
Two former senior FDA officials told The Examination that this review should address the pouch material. They and another former official questioned whether the FDA met its legal and regulatory obligations before authorizing Zyn for sale.
The law requires every component of the product to be evaluated, said former FDA policy director and lawyer Eric Lindblom. It would be “careless at best and negligent at worst” if the FDA did not scrutinize whether the pouch material itself could be harmful, he said.
An FDA spokesperson told The Examination that it authorized Zyn pouches after its review “did not identify new or additional concerns about the ingredients/materials of these products specifically.”
The Examination asked the FDA three times to say what Zyn pouches are made of, but the agency didn’t respond.
Nor did Philip Morris International. Its website says the pouches are cellulose, or plant fiber, but doesn’t elaborate.
Danish researchers have concluded nicotine pouches are made of a material similar to cigarette filters, which take years to decompose; a major United Kingdom retailer says pouches are “not fully biodegradable.”
Two weeks ago, the FDA gave Zyn another endorsement when it ruled that Philip Morris International could state in its marketing that using Zyn instead of cigarettes lowers the risk of certain smoking-related diseases. That likely will help the company convince other countries to open up their markets to Zyn.
The company praised the FDA for “its detailed scientific review,” in contrast to countries that have chosen to ban the product.
Pouch questions arose amid pressure to complete review
Leppanen, who lives in St. Paul, Minn., has been a toxicologist for almost 30 years and has published a number of academic papers on environmental toxicology. She joined the Center for Tobacco Products in 2021 for what would be a four-year stint.
Leppanen was assigned to examine the potential for human and environmental exposure to microplastics. It was in that context that she weighed in on environmental and health questions around Zyn pouches.
In an April 2023 meeting, Leppanen said she was concerned about what happens to the pouch material when a user tucks it between their gum and lip. “There’s heat, there’s enzymes … and those factors influence breakdown of these polymers into microplastics that are then consumed,” she said, according to a recording reviewed by The Examination. Studies had raised questions about the harms of consuming microplastics orally, she said.
In 2024, Leppanen was assigned to an environmental science team handling the Zyn authorization, which by then had been pending for four years. In order to authorize Zyn without further scrutiny, federal law required the FDA to issue a “finding of no significant impact” for environmental issues.
Leppanen and her colleague, Dilip Venugopal, were charged with updating the environmental assessment. They were to determine whether Zyn was likely to have an environmental impact, for instance from manufacturing or package disposal.
In three meetings, Venugopal, who had led the initial environmental review, said the pouches dissolved in the mouth, according to recordings Leppanen shared with The Examination. (Leppanen, who believed she had faced retaliation after questioning the data used for a cigarette authorization, had started to record work calls.)
It was only by testing the products herself that Leppanen demonstrated what is obvious to anyone with a passing knowledge of nicotine pouches: Users discard the pouches after use, resulting in a litter problem in some places.
That night, Leppanen emailed Venugopal to say the environmental assessment would not support a “finding of no significant impact” and asked him to inform their bosses.
That started a series of meetings and emails about what the environmental assessment would say about the pouch material.
In a meeting with Venugopal three days later, Leppanen asked, “Why are we pretending like it is dissolving?” according to a recording reviewed by The Examination. Venugopal said he mistakenly believed they did and agreed that it was fair to ask Philip Morris International further questions.
But a week later, Venugopal told Leppanen that FDA leadership wanted to wrap up the review rather than seek additional information from the company, according to a recording of the conversation.
Leppanen pressed him on what the pouches were made of, and he replied that he didn’t know. Nor, he said, did their supervisor, Sharon Edelson-Mammel, or environmental science branch head Susan Addo Ntim. (Neither they nor Venugopal responded to requests for comment.)
In an email the next day, Venugopal provided Leppanen with the brief description of the pouch material that was included in the company’s application. But Leppanen told The Examination that revealed nothing meaningful about the material.
Venugopal wrote in that email that waste from the pouches themselves would represent a “miniscule fraction” of the total plastic waste generated in the U.S. “My conclusion based on these factors do not indicate the potential for significant environmental effects from the disposal of the pouch materials,” he wrote.
Emails between Leppanen and her managers in the following weeks hint at growing tension. At one point, Leppanen wrote that she had a “half dozen pointed issues to address,” to which Edelson-Mammel responded, “To be clear, your work product will be sent to Susan for review by Wednesday, November 20, at 4PM.”
In a lengthy response, Leppanen addressed why she needed more time for the environmental assessment. “Please note that I came on new to this assignment in cycle 2 and the previous draft EA did not include information or considerations of the pouch material,” she wrote.
Four hours later, Edelson-Mammel replied to say she saw nothing that would prevent Leppanen from submitting a draft by the following afternoon.
A surprise while on vacation
On Jan. 16, 2025, the FDA authorized Zyn for sale. An accompanying document stated that a “finding of no significant impact” determination had been signed by Leppanen on Jan. 2.
In an email Leppanen later sent to health secretary Robert F. Kennedy Jr., she wrote that she didn’t sign that document and wouldn’t have if she had been asked. She was on leave, without access to a work computer, during that time, Leppanen wrote. When she left for her vacation, she told The Examination, the assessment was still in draft form.
The authorization and the supporting documents say little about the pouches, just that a toxicology review concluded “that the pouch material itself is unlikely to produce any adverse health effects in consumers.”
When Leppanen returned to work, she sent a lengthy email to Center for Tobacco Products director Brian King to document her objections to the environmental assessment.
Leppanen recounted that a colleague told her that the pouches dissolved even though the information that disproved this was available online. Although her environmental assessment was neither “outlandish” nor “activist,” she wrote, language about the pouch material was removed. She contended that research on concerns about microplastic exposure should have been included even if it was inconclusive.
“Some of my colleagues believe we are working with the tobacco industry,” Leppanen wrote. “I have no evidence of that. I believe that we are doing these sorts of things to hide our mistakes and avoid litigation. When we do that, we risk the public health that we are obligated to protect.”
Leppanen said King never responded. The next week, Leppanen took advantage of a DOGE deferred resignation offer.
King, who is no longer director of the Center for Tobacco Products, did not respond to The Examination’s request for comment.
Leppanen’s account raised alarm bells with former FDA officials. If she tried to seek additional information on the pouch material but was shut down by FDA superiors, “this is a pretty serious charge,” said Mitch Zeller, former head of the Center for Tobacco Products.
David Ashley, who was director of science at the Center for Tobacco Products until 2017, told The Examination that, based on his understanding of the rules for approving tobacco products, a company must provide information on the pouch material. If it doesn’t, it should be issued a deficiency letter or denied the authorization, Ashley said.
Leppanen’s allegations could open the FDA up to litigation accusing it of failing to satisfy its obligations under the Tobacco Control Act, according to Esther Agbaje, the lead lawyer on federal regulation at the Public Health Law Center. The Minnesota-based organization studies litigation on tobacco and other issues.
There “could be a cause of action if it’s obvious they skipped a step” in the authorization, Agbaje said.
Researchers say pouches could expose users to microplastics
There is very little publicly available information about what nicotine pouches themselves are made of. The only study The Examination could find was done by Denmark’s Environmental Protection Agency.
Researchers carried out testing to determine the chemical fingerprint of 11 brands of nicotine pouches, including Zyn. They concluded the pouch material is a semi-synthetic cellulose that closely resembles cellulose acetate. That’s what cigarette filters are made of.
Researchers have studied microplastics produced by cigarette filters, but nothing has been published on microplastics from nicotine pouches or whether the pouches themselves could harm people.
Richard Thompson, a marine biologist at the United Kingdom’s University of Plymouth who is credited with coining the term “microplastics,” said he sees the potential for nicotine pouches to shed microplastics in the mouth if they are made from cellulose acetate. Microplastics below a certain size can pass from the gut to the circulatory system, which could cause disease elsewhere in the body such as in the heart and liver, he said.
The Examination asked three academics who have studied microplastics from cigarettes — environmental health researcher Abbas Shahsavani, environmental engineer John Atkinson of the University at Buffalo, and marine pollution expert Sedat Gündoğdu at Çukurova University in Turkey — whether a nicotine pouch could break down into microplastics. All of them said that if the pouch is made from cellulose acetate, it could.
Shahsavani, a professor at Shahid Beheshti University of Medical Sciences in Iran, said his research shows that microplastics from the cellulose acetate in cigarette filters “have the potential to contribute to disease” because they are toxic to human immune cells.
Leppanen said the FDA could have included a statement noting the potential risk of microplastics while acknowledging that more research is needed.
Shortly before Leppanen resigned in January 2025, an FDA official emailed her to say that the “finding of no significant impact” would be corrected to say she hadn’t signed it.
She waited months, but the correction didn’t appear. In the meantime, she sought legal advice and was told to write a book about her experience and go to the media. She did both.
On March 1, Leppanen used a public comment portal for another Zyn matter before the FDA to press the matter. “It is professionally damaging to be listed as the decision maker in determinations that I did not make or agree with,” she wrote.
Soon after, two things happened. On March 10, the FDA published a report that concluded the environmental impacts of nicotine pouches and other oral products were “minimal.” But, it acknowledged, the assessment “does not address the potential effects of plastics and microplastics from the pouch materials.”
A few weeks later, the FDA updated its Zyn authorization to say that Leppanen did not sign the “finding of no significant impact.” It’s dated Jan. 27, 2025.
Do you have something to share about the FDA’s regulation of tobacco products? Email The Examination’s Matthew Chapman at [email protected].