Hey there! If this is interesting to you, then you’ll want to pre-order my book To Dye For: How Toxic Fashion Is Making Us Sick. It’s coming out in June 2023, and it dives deeper into all the chemicals that show up in all sorts of clothing…and what you can do to protect yourself. Pre-order it here.
A few years ago, a friend forwarded an Instagram story to me from a wellness influencer who was warning her followers against wearing clothing made from recycled bottles. Her theory was that, as a recycled plastic, rPET fabric contains harmful endocrine-disrupting substances like BPA or phthalates that will interfere with your thyroid function and hormones.
This theory is not so farfetched. It’s been well-reported that many types of plastics, including water bottles, have chemicals in them that can leach out, especially when water bottles are heated, like if you leave one in your car in the summer. Scientists have found high levels of antimony, a heavy metal and potential carcinogen, though not confirmed as an endocrine disruptor, in water sold in disposable PET bottles, the kind that are recycled into polyester. Most American-made PET plastic bottles do not contain the endocrine disruptor BPA, which has been linked to breast cancer and infertility — it’s more likely to be found in polycarbonate bottles like reusable squeezy sports bottles and food can linings. But that’s not a hard-and-fast rule. BPA has been found in Chinese water bottles, and since most polyester is manufactured in Asia (but not all) it’s possible that your recycled polyester leggings are made from this same type of PET.
In fact, experts recommend that you never reuse a disposable water bottle, because of these chemicals that leach out. But… can you recycle it andwear itand be OK?
Is polyester made from recycled water bottles especially toxic to wear?
To answer this question, I turned to Dr. Martin Mulvihill, a trained chemist, researcher, and senior advisor and board member at the Berkeley Center for Green Chemistry, which he helped create and where he served as the founding initial Executive Director from 2010 to 2015. He’s now the co-founder and partner at Safer Made, a mission-driven venture capital fund that invests in companies and technologies that reduce human exposure to harmful chemicals. In other words, he’s an expert.
PET stands for polyethylene terephthalate. If you’re familiar with the world of toxic chemicals, you might have spied “phthalate” in there, which is part of a group of chemicals that are either known or suspected endocrine disruptors. Why should you care? Because endocrine disruptors essentially mimic hormones in a harmful way, leading to thyroid issues, and potentially breast cancer and fertility and developmental issues in children. But, “It is important to recognize that terephthalates are not suspected to be endocrine disruptors in the same way that ortho-phthalates are,” Mulvihill said. They’re not one of the phthalates banned in the European Union, for example. And he’s seen no evidence that any phthalates leach into the water inside PET water bottles, much less leach out of PET polyester clothing wearing it.
He next cites the research I talked about above showing that antimony, which is used to manufacture PET, has leached into the water inside water bottles. It’s a heavy metal and suspected carcinogen, though not an endocrine disruptor. Manufacturers could use titanium instead of antimony to manufacture PET for bottles, but it’s more expensive and doesn’t work as well, so they rarely do.
“But I am not overly concerned about it impacting human health,” he says. That’s because the research shows that it takes 38 days of a water bottle being heated to 150 degrees Fahrenheit for antimony to reach unsafe levels, and that is for water that you ingest, not fabric against your skin.
The study on Chinese water bottles indicated that BPA release at four weeks in 158-degree heat was below EPA standards. Let’s be honest: if you’re in 150-degree heat while wearing your workout clothing, you have bigger problems than your hormones. However, there’s been a lot of research on how even the lowest doses of BPA can affect not only your hormones, but the development of your future children (you’ve already got the eggs for your future children in your body, and they can be affected by BPA in your system). Hormones regulate so many different vital processes in our bodies; just a tiny amount can throw things out of wack. “Because BPA has completely different effects at low levels than it does at high levels, there’s no such thing as a ‘safe level,'” Rick Smith and Bruce Lourie wrote in their 2009 book, “Slow Death by Rubber Duck“.This debate, that no dose of BPA and other endocrine-disrupting chemicals can ever be safe, has continued to play out since then.
Finally, ever thorough in his answer (I love scientists), Mulvihill said that recycled PET could be contaminated with other plastics that do have endocrine disruptors. “That said, contamination severely impacts the quality of fiber, so a lot of time and effort goes to removing any non-PET contamination. The amount of contamination probably isn’t zero, but I haven’t seen any data to indicate it is a serious concern…I think that this could be an example of how the public messaging around plastic = bad when it comes to food is having an unintended consequence,” Mulvihill concluded in his 2019 email.
Wait, I’ve got one more consideration here. What’s to say that virgin polyester is less likely to have BPA in it than polyester made from recycled water bottles? “There’s almost no very pure PET on the market,” says Helene Wiesinger, a researcher at ETH Zurich, who published a risk assessment of plastic additives. “There’s always something that you add in to make it more resistant to UV or more resistant to heat or more resistant to a lot of different things.”
Recently, the Center for Environmental Health in California found BPA in socks from 88 different brands. CEH specified that the common denominator was polyester content—cotton socks were fine. It said nothing about the recycled content. According to Oeko-Tex, “BPA can be added in the manufacturing of polyester as an intermediary step to improve the natural properties and lifespan of a fabric. In the production of polyester fabric, BPA can be used to create hygroscopic and antistatic fabric with colorfastness to washing. …And it may also be used in spandex production for antistatic properties.”
Maybe, the problem isn’t that the polyester is recycled. Maybe, the problem is the polyester itself. But you might have bigger things to worry about than even the polyester…
Why you should care less about the material and more about the finish.
The type of material does matter hugely when it comes to the environment. When it comes to emissions and waste, there is currently some debate about whether recycling water bottles into fabric instead of into water bottles is actually the better choice. That’s another whole article, but in terms of your health, what really matters is the substances that were put on the material. How was it washed and dyed? Are there any toxic finishes on it?
“BPA and other bisphenols may be used as dye-fixing agents for polyester and polyamide textiles. Furthermore, BPA can be used in the production of flame retardants, fungicides, antioxidants and in PVC production,” Oeko-Tex says.
If my biggest concern was toxicity, and you presented me with a white, 100% polyester blouse certified by Oeko-Tex, and an neon-colored, organic cotton blouse that was treated with formaldehyde to prevent wrinkles, I would absolutely choose the polyester blouse. After all, if the chemical is in polyester, it has to leach out before it can be absorbed into your skin. Whereas finishes are always off-gassing, sloughing off, or mixing with your sweat.
“In the end, many of us care about both human and environmental health, but I think it is worthwhile to make the distinction,” Mulvihill told me in 2019. “From an environmental perspective, the rPET is a good thing, but we need to make sure it isn’t coated with harmful chemicals or antimicrobials before we declare it a good option for human health.”
So if you’re reading this because you’re pregnant, or you’re having thyroid, fertility, or reproductive health issues, then my advice to you is to look for companies that care about how their clothing is treated.
Look for Oeko-Tex, GOTS, and bluesign labels. For big brands, check to see if they’re a member of ZDHC, an industry group that prohibits manufacturers from using certain toxic substances, or Afirm, which helps brands test their products before they get onto shelves. Nike has had a robust chemical management system in place for longer than almost anyone. Also avoid anti-microbial, anti-odor, anti-wrinkle, and (with a few exceptions) anti-stain finishes.
If, after reading this, you prefer natural fibers, there are a few options we rounded up for you. If you prefer nylon and polyester, make sure to check out our roundup of sustainable athletic brands, many of which are completely non-toxic.