A big story this week is Thinx settling a class action lawsuit about the advertising of their period underwear. This lawsuit wasn’t about the safety of the underwear, rather the fact that Thinx claimed their menstrual underwear was “organic, sustainable and nontoxic,” but independent analysis showed it contained PFAS. As PFAS are toxic, the lawsuit claimed Thinx misled customers.

This has created some awful headlines and quite a few terrible takes on social media. I’ve also received a lot of DMs about it, so let’s break it down.

What Are PFAS?

PFAS stands for per- and polyfluoroalkyl substances (PFAS) and there are over 9,000 of them. According to the National Academies of Science and Engineering there is no consensus definition, but the Organisation for Economic Co-operation and Development (OECD) uses this definition, “fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), that is, with a few noted exceptions, any chemical with at least a perfluorinated methyl group (–CF3) or a perfluorinated methylene group (–CF2–) is a PFAS”. For the non chemists, a really simplified version of this definition is they are chemicals with extra fluorine.

PFAS are used in the manufacturing of many products as they have useful properties, such as making things waterproof or greaseproof, they can be fire retardant, and they reduce friction. It’s hard to find an industry untouched by PFAS. Paint, guitar strings, carpet, ski wax, cosmetics, food wrapping, dental floss, shampoo, sunscreen, firefighting foam, and water resistant clothing is but a partial list.

As PFAS don’t degrade, or it takes almost forever for them to degrade, they are often known as “forever chemicals.” They enter our world, but don’t really leave, and so they accumulate. According to the Environmental Protection Agency (EPA), “PFAS can be present in our water, soil, air, and food as well as in materials found in our homes or workplaces.” They are found around the world in the air, water, and soil, even in the Arctic and Antarctic.

The environment gets contaminated with PFAS in different ways. Manufacturing sites are the biggest source, releasing PFAS into the air that can settle in the soil or come back down with rain and contaminate the soil and water. PFAS released from manufacturing plants into the water supply contaminates the water. Discarded materials decompose in landfills, releasing PFAS into the soil and water and if garbage with PFAS is incinerated, the chemicals can be released into the air. And the food we eat can be contaminated with PFAS. Products that contain PFAS, for example, greaseproof wrapping and takeout containers, can also contaminate food as well as the people who touch the wrapping.

It’s easy to see how these “forever” chemicals have become “everywhere” chemicals.

The most concerning of the PFAS chemicals are PFOS and PFOA as these two are especially hard for the body to get rid of and so they accumulate. They are no longer used in products in the United States, but we are still exposed to PFAS from imported products or because of contamination of the water, and soil from decades of use. There are newer PFAS that apparently leave the body faster, and are supposed to be safer, but they still don’t break down in the environment, so we can get re-exposed over and over and we don’t have long-term safety data about these newer chemicals.

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What are the Health Concerns with PFAS?

There are thousands of PFAS and we don’t know the health ramifications of all of them. However, there is a high degree of certainty that some are associated with a range of health conditions, such as thyroid disease, increased levels of cholesterol, kidney cancer, suppression of the immune system, and low birth weight among fetuses exposed during pregnancy. There is also weaker evidence linking them to other conditions, such as breast cancer, early onset puberty, and certain pregnancy complications, such as high blood pressure.

One interesting menstrual-related PFAS fact is that those who menstruate tend to have lower levels, likely because PFAS are bound in the blood, so you lose some each month.

Most experts agree the biggest risk is from exposure during the manufacturing of PFAS, or exposure from pollution from a manufacturing site (this was the basis of the Mark Ruffalo movie Dark Waters), where the water you drink, the showers you take, and the local food that you buy all have higher than average levels of PFAS. Another big risk is for people in industries that use or depend on products with PFAS, such as firefighters, carpet installers, and the food industry.

What to make of the lawsuit against Thinx and PFAS

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What About Thinx?

A few years ago a reporter sent her Thinx to a lab to be evaluated and fluorine, which is considered evidence of PFAS, was identified. The plaintiff in a lawsuit filed in New York tested her Thinx and that revealed short-chain PFAS (the ones not banned in the US) at levels that suggested they weren’t there by accident. Eventually there were several lawsuits that became one class action lawsuit.

How do PFAS get into period underwear? They could get in accidentally during manufacturing, I don’t understand the ins and outs of this, but it seems fabric can become contaminated just like everything can or can contain products that aren’t PFAS themselves, but later break down to PFAS. The textiles expert I contacted thought if PFAS were in Thinx they were likely there on purpose as they strengthen the fabric and allow for water repellency, as those are desired qualities in period underwear. It’s possible that Thinx didn’t know PFAS were in the fabric they were using, and so I can’t comment on it being intentional or accidental. What I can say is studies show that many items that are labeled as non toxic or green have PFAS. If you are a long time follower of mine you will know I despise words like green or organic or nontoxic for that very reason as they don’t have a scientific definition. They are marketing, they do not tell you if a product is safe or tested.

Can the PFAS from period underwear get in your body? One expert I spoke with said it was unlikely. If the PFAS were there on purpose he felt it was likely well bound to the fabric. However, there is some data to suggest that with washing some PFAS are removed, but the biggest risk here seems to be entry into the water supply not to the person using the product. Graham Peaslee, the University of Notre Dame professor whose lab initially identified identified PFAS in Thinx, told the New York Times Wirecutter, “Simply put, if you’ve already washed your period underwear a few times, you’ve probably washed the PFAS out, and now they’re poisoning everything downstream instead of you.”

The only thing we actually know about PFAS in clothing is that the risk from wearing clothing that has been manufactured with PFAS is unknown. I know many aspects of menstrual health are unstudied or understudied, but I think it’s important to point out that as far as the use in clothing goes, nobody knows. Some studies suggest if it happens, it’s a minor contribution to the body burden (meaning much less than 5% of what we get from other sources like drinking water and food), but we don’t really know. Basically, this is an active area of research.

We have some data on skin absorption from Denmark, where a large study looking at cosmetics found that while PFAS were present in many, that the amount in “cosmetic products themselves do not pose a risk to consumers.” But they added that if several products were used at once then perhaps that might change, but they also didn’t consider that scenario “particularly realistic.” Another study that looked at dental floss with PFAS did find that a potential source of concern, and that makes sense because it’s going in the mouth, and of course for some people with gum inflammation, flossing can be associated with with trauma and the combination of inflammation and trauma might further increase absorption.

PFAS are in lots of athletic clothing and outdoor gear, and I find the silence about PFAS here interesting. Technical clothing that covers the legs, from running tights to hiking pants, cover a very large surface area. Might PFAS be an issue if they get wet from sweating combined with the increased blood flow from working out, which could increase absorption across the skin? Obvious, we don’t know, but when the only scary headlines are about period products it supports my long standing belief that scaring people about menstrual products is basically an industry. This week it was period underwear, but tampons and menstrual cups have both recently made headlines about supposed risks based on no credible data. While researching this piece I even saw an article from someone who was concerned that silicone menstrual cups might be exposed to dangerous chemicals during manufacturing, so sticking with natural rubber was better. Never mind that we’ve been using silicone products in medicine for decades. It seems that some people won’t be happy until everyone is bleeding onto their clothes.

Also, using a chemical that shouldn’t get on your skin during manufacturing doesn’t mean that there are concerning residues on the product.

So What Should I Do?

According to the National Academy Sciences and Engineering “It is difficult to provide clear advice on how to reduce exposure to per- and polyfluoroalkyl substances (PFAS) because there are many potential exposure sources.”

Based on the limited information we have on the risks of PFAS in fabric, individual exposure is likely not a significant source. Obviously, there are unknowns and asterisks here, but if you have used Thinx, don’t panic. And while the vulva is more absorbent than other areas, most things placed on the vulva don’t absorb 100%. Overall, the biggest issue with PFAS in period underwear is likely the global contribution from manufacturing, washing, and then when it eventually ends up in landfill. That’s not an insignificant issue, but it is less panic inducing. We should all want textiles free of PFAS the way we all want cars that don’t pollute.

The recommendations from the National Academies of Science and Engineering for limiting and avoiding PFAS are as follows:

Filter drinking water with an activated carbon (like a Brita) or reverse osmosis filtration system (more expensive) if levels of PFAS are high in your drinking water (you can check online to see if your water supply is tested or not)
Avoid stain resistant fabrics and sprays, that includes carpets and upholstery
Avoid products with PFTE or “fluoro” listed on the label
Choose cookware that is stainless steel, enamel, glass or cast iron
Avoid takeout containers, and if you must use them, transfer food out as soon as you get home and don’t reheat in the container. Time and heat increase the transfer of PFAS.
Avoid microwave popcorn and greasy foods wrapped in paper.
Look for nylon or silk dental floss or floss coated in natural wax

Some websites have sent period underwear out for testing for PFAS, but when those results aren’t published in peer reviewed journals, it’s hard to comment on their accuracy. One site that publishes a lot of this information has some incorrect information on their site (hence I’m not linking). Some period underwear companies are now paying for third party testing to prove their products are PFAS free, for example Aisle, although the testing is just one pair of underwear.

I suspect that proving products are PFAS free will become the standard. What we really in my opinion is federal regulations and more oversight via the FDA.

If you have been using Thinx, I wouldn’t panic. It seems unlikely based on what we know that it’s a major concern for a given individual, but I am always open to what we know changing. Going forward, looking for PFAS free period underwear seems wise, understanding that relying on companies to post testing has its own issues, even if it’s done by a third party. Finally, the most significant source of PFAS exposure for most consumers is water and food. Meaning, if you are only worried about period underwear you’re likely missing what we know to be your biggest source of exposure.

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For More Info

This Consumer Reports article has some practical advice on PFAS https://www.consumerreports.org/toxic-chemicals-substances/how-to-avoid-pfas-a8582109888/

List of PFAS free products (menstrual products not included) https://pfascentral.org/pfas-free-products/

References

National Academies of Science, Medicine and Engineering. Guidance on PFAS Exposure, Testing, and Clinical Follow-Up (2022).

Suzanne E. Fenton, Alan Ducatman, Alan Boobis, et al. Per- and Polyfluoroalkyl Substance Toxicity and Human Health Review: Current State of Knowledge and Strategies for Informing Future Research. Environmental Toxicology and Chemistry—Volume 40, Number 3—pp. 606–630, 2021

Juliane Glüge, Martin Scheringer, Ian T. Cousins et al. An overview of the uses of per- and polyfluoroalkyl substances (PFAS). Environ Sci Process Impacts. 2020 Dec 1; 22(12): 2345–2373.

FDA Per and Polyfluoroalkyl Substances (PFAS) in Cosmetics https://www.fda.gov/cosmetics/cosmetic-ingredients/and-polyfluoroalkyl-substances-pfas-cosmetics

Boronow, K.E., Brody, J.G., Schaider, L.A. et al. Serum concentrations of PFASs and exposure-related behaviors in African American and non-Hispanic white women. J Expo Sci Environ Epidemiol 29, 206–217 (2019).

Van der Veen, I., Schellenberger, S., Hanning, A-C., Stare, A., de Boer, J., Weiss, J. M. and Leonards, P. E. G. (2022) Fate of Per- and Polyfluoroalkyl Substances from Durable Water-Repellent Clothing during Use. Environmental Science & Technology 56(9): 5886–5897

Oddný Ragnarsdottir, Mohamed Abou-Elwafa Abdallah, Stuart Harrad. Dermal uptake: An important pathway of human exposure to perfluoroalkyl substances? Environmental Pollution 307 (2022).

Consumer Reports. Should You Be Concerned About PFAS Chemicals?

These 'forever chemicals' are in our water supply—and in the body of nearly every American. Kevin Loria, April 2019. https://www.consumerreports.org/toxic-chemicals-substances/pfas-chemicals-should-you-be-concerned-a2708998896/

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