Katherine Martinko is an expert in sustainable living. She holds a degree in English Literature and History from the University of Toronto.
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Thinx, the period underwear company, has settled a class-action lawsuit alleging that its products contain harmful chemicals. Over the last several years, the brand has grown in popularity precisely because its products were advertised as sustainable and nontoxic. They were seen as a greener, zero-waste option for dealing with a period—and one that seemed safer compared to conventional chemical-laden pads and tampons.
The lawsuit paints a different picture, however. Tests revealed that the absorbent underwear contains per- and polyfluoroalkyl substances, more commonly known as PFAS. These chemicals are linked to decreased fertility, low birth weight, high blood pressure in pregnant women, increased risk of some cancers, a reduction in immune system functioning, and hormone disruption.
PFAS are a group of manmade chemicals best known for their ability to repel water and stains and to create nonstick surfaces (think Teflon). They're referred to as "forever chemicals" because they persist in the natural environment, accumulate in animals, and do not degrade. PFAS are detectable in most human bodies, due to so many sources of exposure.
The Thinx lawsuit focused on the fact that its advertising was misleading, not on the potential health effects of its underwear. But people are nonetheless concerned about the fact that PFAS were found in products worn close to one of the most sensitive and absorbent parts of a woman's body.
In 2020, when journalist Jessian Choy sent three pairs of Thinx underwear to a lab, she discovered that a pair of the "organic" briefs contained 3,264 parts per million (ppm) of PFAS, and the organic BTWN Shorty underwear for teens had 2,053 ppm. "That's high enough to suggest they were intentionally manufactured with PFAS," she wrote for Sierra magazine at the time. Furthermore, all three "had tens to hundreds of ppm of copper on the inside of the crotch, and zinc on both sides."
Additional tests have revealed the presence of Agion, "an antimicrobial odor reducing agent made from silver and copper nanoparticles, even as Thinx claimed its products were 'free from these non-migratory nanoparticles.'" Silver nanoparticles are sometimes added to fabrics as an antimicrobial agent, but its safety is disputed. According to Women's Voices for the Earth, it can have adverse effects on vaginal health and is more of a marketing gimmick with a "poor track record of actually being effective."
The lab scientist who tested Choy's underwear, Dr. Graham Peaslee of the University of Notre Dame, said, "These nanoparticle metals are used as antimicrobials and might be able to penetrate the skin and get into the bloodstream. The microbial toxicity of all these compounds is well known; what isn't as well known are the human lymph node responses to them and other disease outcomes in humans from exposure."
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The question of intentional production is worrisome. It's not a stretch to question Thinx's denial of allegations, since the addition of these chemicals would, in theory, help its underwear to achieve the goal of better absorbency with no odor and less mess. But how easy is it for brands not to know exactly what's in their products?
Treehugger reached out to Kelly Drennan, founding executive director at Fashion Takes Action, to learn more. She acknowledged that it is very difficult for brands to know what's in the materials they use.
Drennan explained that transparency in the industry is connected to traceability, but this is still quite problematic. "It is very difficult for brands to know their supply chain beyond tier 1 or 2 [factory manufacturing and fabric dyeing/processing, respectively], with tier 4 being the raw material stage. There must be a chain of custody in place. Without this, it is difficult to trust suppliers. So [what's needed is] chain of custody, traceability, testing, and transparency."
PFAS is known for its effective water- and weather-proofing properties, and Drennan pointed out that it's only recently that we've begun to understand the potential negative health impacts of PFAS. She said, "I don't really know if there are any safe alternatives at this time, but brands who use PFAS should be hyper focused on this and investing in the material science and innovation to solve for it."
In the meantime, consumers would be wise to do their research. "PFAS in a rain coat is not the same as PFAS in your underwear or any garment that is right next to your skin. But that doesn't mean PFAS is OK, so putting pressure on your favourite outdoor or athletic brand to phase it out is a good step, i.e. send an email or tag on social," Drennan suggested.
While there are some apps that rate and rank cosmetics and skincare products for safety (like SkinDeep), and some that delve into the ethical, environmental, and animal welfare impacts of fashion (Good on You), none looks at chemical usage in textiles. Drennan described this as a gap that needs to be filled—"Hopefully some entrepreneur will figure this out!"—but for now, people just need to read up on the brand, examine labels (even if PFAS don't appear), and engage government in stricter legislation around product transparency and labeling.
"The NY Fashion Act is leaps ahead and is now banning PFAS from clothing by the end of this year," Drennan said. "So hopefully we will start to see similar legislation in other jurisdictions and then brands will be forced to find out if their products contain PFAS!"
This story is an unfortunate yet valuable lesson in thinking critically about the products we buy and analyzing the function they serve. If something seems too good to be true, it might be that it is—at least, in ways that might make us uncomfortable once we know the whole story.
And it's a reminder of the value in continuing to fight for clean, safe products that do not harm our bodies or the environment. It has taken several years for this lawsuit to get settled, but now Thinx has promised to "ensure that PFAS are not intentionally added to its underwear at any stage of production and adjust some of its marketing language, including disclosing the use of antimicrobial treatments."
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