Thinx, the period-underwear brand that built its whole identity around being the clean alternative to disposable pads, paid up to $5 million in 2023 to settle claims that its underwear contained PFAS "forever chemicals." That same year, an EPA-certified lab found detectable organic fluorine, a chemical marker for PFAS, in name-brand tampons, organic cotton tampons, and roughly two-thirds of the period underwear it tested.
If you menstruate, this is one of the more uncomfortable PFAS stories, because the vaginal and vulvar tissue these products touch is some of the most absorbent skin on the body. You can check what is flowing out of your own tap with a free ZIP code water lookup, but period products are a different kind of exposure, and most of the data comes from a small number of independent investigations rather than government testing.
In 2023, the environmental wellness community Mamavation partnered with the news outlet EHN.org to send 23 tampon products to a U.S. EPA-certified laboratory. The lab tested for organic fluorine, which is the practical stand-in for PFAS because testing for individual PFAS compounds directly is slow and expensive, while organic fluorine reliably shows up when fluorinated chemicals are present.
Five of the 23 products came back with detectable organic fluorine, between 19 and 28 parts per million (ppm):
The detail that surprised a lot of readers: two of the five were marketed as organic cotton. "Organic" refers to how the cotton was grown, not to whether the finished product picked up fluorinated chemicals somewhere in manufacturing. The levels in the tampon study were low enough that the testers described them as "not intentionally added," meaning the most likely explanation is contamination somewhere in the supply chain rather than a deliberate PFAS ingredient.
That is an important nuance and a reason not to panic. A reading of 19 to 28 ppm of organic fluorine is far below what later turned up in some other products (contact lenses hit five figures), and the study could not say how much, if any, of those chemicals migrate from a tampon into the body. What it does say is that "even organic" is not a guarantee of zero, and that the absorbent-tissue exposure route deserves real research that does not yet exist.
Period underwear is where the strongest signal showed up. Mamavation tested 17 period-underwear products and found that about 65 percent had detectable fluorine, the marker for PFAS, at the lab's detection limit of around 10 ppm.
The legal fallout centered on Thinx. A class-action lawsuit accused the brand of marketing its underwear as a safe, sustainable, organic-cotton, non-toxic product while, the plaintiffs argued, it contained PFAS. In 2023 Thinx agreed to a settlement of at least $4 million, with a ceiling reported around $5 million, covering people who bought certain Thinx products between November 12, 2016 and November 28, 2022. Buyers could claim a cash payment or a voucher even without proof of purchase.
Thinx admitted no wrongdoing and said it never intentionally added PFAS to its products. As part of the settlement it agreed to take steps to make sure PFAS would not be intentionally added going forward. That distinction, intentionally added versus present, runs through almost every PFAS-in-products story: a brand can truthfully say it never put the chemicals in while a lab still detects them, because PFAS can ride in on coatings, machinery, or raw materials.
Why would period underwear contain PFAS at all? The leading theory is moisture management. PFAS are champions at repelling water and oil, which is exactly the property you would want in a layered, leak-resistant garment. The same chemistry that makes a rain jacket bead water can make underwear feel reliably dry, and that is the trade some manufacturers appear to have made, whether deliberately or through supplier choices.
Mamavation also looked at sanitary pads and incontinence pads. As with tampons, some products showed detectable organic fluorine and some did not, reinforcing the pattern that contamination is uneven across the category rather than universal. The takeaway is not "every period product is full of forever chemicals." It is that you currently cannot tell from the box which products are clean, because no law requires this testing or its disclosure.
PFAS exposure adds up across the dozens of products you touch in a day. Period products are one input; so are your cookware, food packaging, and personal care products, and so is your drinking water. No single source is usually the whole story, which is why people who want to lower their total load tend to work on the biggest, most controllable exposures first rather than chasing every last ppm.
A few practical moves, in rough order of how much they are worth:
You can see how PFAS shows up across both drinking water and everyday products and decide where your effort is best spent. And if you have not checked your tap yet, the ZIP code lookup on the homepage is free and takes a few seconds.
### Do all tampons contain PFAS? No. In the Mamavation and EHN testing of 23 tampon products, only 5 showed detectable organic fluorine, the marker for PFAS, at 19 to 28 ppm. The majority did not have detectable levels. The problem is that you cannot tell from the packaging which is which, because brands are not required to test or disclose.
### Are organic cotton tampons safer from PFAS? Not automatically. Two of the five tampons that tested positive for organic fluorine were marketed as organic cotton. "Organic" describes how the cotton was grown, not whether the finished product picked up fluorinated chemicals during manufacturing.
### How much was the Thinx PFAS settlement? Thinx agreed to a settlement of at least $4 million, reported as high as $5 million, in 2023. It covered U.S. customers who bought certain Thinx period underwear between November 12, 2016 and November 28, 2022. Thinx admitted no wrongdoing and said it never intentionally added PFAS.
### Can PFAS in period products actually get into my body? That is the open question. The vaginal and vulvar tissue these products touch is highly absorbent, which is why researchers are concerned, but the existing studies measured chemicals in the products, not how much migrates into the body. There is not yet good data quantifying that transfer, which is itself a reason the testing matters.
### What does "organic fluorine" mean and why do labs test for it instead of PFAS? Organic fluorine is fluorine bound to carbon, the chemical fingerprint of PFAS compounds. Labs test for it because measuring every individual PFAS compound directly is slow and costly, while total organic fluorine is a faster, reliable indicator that fluorinated chemicals are present.
### Which period products are PFAS-free? There is no official certified list. Your best signal is a brand that publishes recent third-party organic-fluorine or PFAS test results showing non-detect, rather than relying on marketing words like "clean," "non-toxic," or "organic," none of which guarantee the absence of PFAS.
Next step: pick the one period product you use most, search the brand name plus "PFAS testing," and see whether the company publishes an actual lab result. If it only offers marketing language, treat that as a reason to look for a brand that shows its work.