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Forever chemicals are everywhere, including in period and incontinence products—even in some that companies claim are free of such substances.
That’s the conclusion from independent lab testing we solicited that looked for signs of per- and polyfluoroalkyl substances (PFAS) in 44 products—including period underwear, tampons, menstrual cups, and more—and found plenty.
Often called “forever chemicals” because they can take years or even centuries to degrade, PFAS are associated with numerous personal and environmental health risks. They’re virtually inescapable in everyday life, having been added to or detected in everything from food wrappers and cookware to cosmetics and drinking water. Manufacturers often use them to make some fabrics waterproof, leakproof, or stain-resistant, as well.
Considering the lab-test results, we’ve concluded that shoppers should be skeptical of claims that period underwear and similar products are PFAS-free. People who want to lower their potential exposure to PFAS when managing their period may consider using medical-grade silicone insertables, such as menstrual cups or discs, instead. (Our guide has detailed advice on where to start.)
In early 2023, we bought and mailed 44 different products to Graham Peaslee, whose University of Notre Dame lab studies PFAS in the environment and has performed tens of thousands of tests looking for signs of contamination with these substances in consumer products.
Peaslee’s lab did the testing that found PFAS in a pair of Thinx underwear sent in by a contributor to Sierra Club magazine in 2019. Thinx later agreed to pay up to $5 million as part of a settlement for a class-action lawsuit in which the plaintiffs alleged that the company’s marketing—claiming that its menstrual underwear was “free of harmful chemicals”—was misleading. The plaintiffs cited findings of PFAS, among other substances, in Thinx underwear.
At the time of the settlement, Thinx denied that PFAS were intentionally included in its underwear. And this week the company told Wirecutter in an email: “PFAS are not part of our product design, and we take rigorous steps to ensure suppliers don’t add PFAS to our products.”
Wirecutter has long recommended a pair of period underwear from Thinx, namely the brand’s Hi-Waist style, which is both effective and stylish. So we wondered whether previous findings of PFAS in pairs of Thinx would replicate—and whether other underwear, including pairs marketed as “PFAS-free,” would hold up to scrutiny by experts in a non-commercial lab.
We also wondered whether period underwear was more or less likely to contain PFAS in comparison with menstrual pads, tampons, menstrual cups, and pads or underwear meant to help manage urinary incontinence.
With the help of graduate students including Alyssa Wicks, who performed all of the tests on the products we sent, Peaslee’s lab tests thousands of product samples annually for levels of fluorine, which is a reliable marker for suspected PFAS contamination. (Neither Peaslee nor Wicks is affiliated with the personal-care product industry.)
Wicks performed more than 200 quantitative fluorine tests on the 44 products we sent, as multiple samples were taken from each product. For example, when testing a tampon, Wicks tested the cotton wad, the string, the applicator, and the wrapper. For period underwear, Wicks tested the lining in addition to other portions of the garment. She tested both sides of disposable and reusable pads, plus any associated adhesives or wrappers.
Every one of the products we sent for testing indicated at least trace amounts of at least one of the thousands of known (and many more unknown) PFAS.
The researchers found that nearly half of the 44 period and incontinence products we sent for testing showed fluorine levels suggesting unintentional PFAS contamination (meaning these substances could have slipped in during production, packaging, shipping, or beyond). And eight products showed high enough levels of fluorine to suggest that PFAS-treated material had been added to them.
Peaslee’s lab considers unintentional contamination to occur at an amount of over 50 parts per million, with intentional contamination starting at anything over 300 parts per million fluorine.
The pair of Thinx underwear we sent for testing showed some the lowest levels of PFAS of the 10 pairs of period underwear we had tested, with no fluorine test registering above 26 parts per million. A different pair of period underwear we sent, made by another brand, showed the highest amount of fluorine in a single sample: 23,864 parts per million. We had purchased that pair from a company that had told us its underwear was free of PFOA and PFOS, two major types of PFAS.
Still another pair of period underwear from yet another brand showed suspected PFAS contamination with fluorine levels of 3,326 parts per million and 8,635 parts per million in two of the five total samples taken; we had purchased that pair from a company that markets its products as being “PFAS-free.”
It’s nearly impossible for any textile to register zero PFAS. “Even if a brand might intentionally try to keep PFAS out of their products,” said attorney Thomas Sokolowski of Taft Law, “PFAS are so pervasive now in the world, they can unintentionally contaminate a product.”
Individual lab-test results from any one pair of menstrual underwear or single incontinence pad are not meaningful enough for anyone to rate products on potential toxicity. And these results are far from definitive.
We didn’t handle the products we purchased and then shipped to Peaslee’s lab with any special care, so we cannot be sure that we didn’t introduce some level of PFAS contamination ourselves. Per Peaslee’s suggestion, we repackaged the products we bought from retailers in resealable plastic bags, labeled the outside with a permanent marker, and mailed them off in a standard shipping box. Also, because we sent a single sample of each product, we could not control for production differences across product lots.
It’s unclear how any of these products may have become contaminated. Given the near-ubiquity of PFAS, the source or sources of contamination can be especially tricky to determine. Contamination can occur at any point during the product life cycle—from design and production to packaging, shipping, receiving, and beyond.
“This is why federal regulations are so important,” said Carla Ng, an associate professor of civil and environmental engineering at the University of Pittsburgh, who has been studying forever chemicals for more than a decade and has advocated for bans on nonessential use of PFAS in manufacturing. “If companies aren’t allowed to use PFAS in consumer goods, then it doesn’t matter where it comes from because the PFAS tap is turned off and the fix comes from the source.”
Managing menstruation or incontinence can be complicated enough without having to also wonder whether the products you use are possibly tainted with potentially toxic substances. “There are so many exposures to worry about, and every person has different mental and financial capacities,” said Dr. Marya Zlatnik, an OB/GYN at the University of California San Francisco.
That said, if you’re trying to limit PFAS exposure while managing your period, you may want to try using a medical-grade silicone menstrual cup or disc, as these products appear less likely to be contaminated with forever chemicals in comparison with disposable products and reusable garments specifically designed to contain leaks, according to this preliminary investigation.
If you prefer using reusable absorbent or leak-containing liners, pads, or underwear, consider washing the pieces before you first use them. Research has shown that washing treated garments in advance may reduce the risk of direct bodily exposure to PFAS, by sending the substances into the environment instead via wastewater.
When shopping for herself or others, Zlatnik said, she’d do “the best that I could to not buy something that had PFAS in it.”
“However,” she continued, “I personally have Thinx that I have not thrown out and I figure that, of the things I’m exposed to intermittently, that’s not the most important one for me.”
This article was edited by Tracy Vence and Kalee Thompson.
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Diaper Wirecutter is the product recommendation service from The New York Times. Our journalists combine independent research with (occasionally) over-the-top testing so you can make quick and confident buying decisions. Whether it’s finding great products or discovering helpful advice, we’ll help you get it right (the first time).