The Dirty Secret in My Gym Bag (And Probably Yours)

What if I told you that your yoga pants contain enough oil to run a car engine for 15 minutes?!

My husband loves saying “but it’s an endocrine disruptor“ in a high-pitched voice, mainly to make fun of me, because I’m so obsessed with the subject. But what can you do when you’re 54 and going through menopause, when even small hormonal shifts can have huge repercussions? I will not let anything mess with my hormones!

For years, I’ve adjusted my lifestyle and home environment to be as low-tox as possible, navigating around phthalates, BPA, Teflon, and all the other chemicals that threatened my inner balance. I invested in Le Creuset cookware, switched to glass containers, replaced my personal care products with organic alternatives, and converted to eco-friendly cleaners and laundry detergents. It’s been a lot of trial and error, because “natural” is not always functional, but I was happy with my clean choices and my supposedly uninterrupted hormonal equilibrium.

Then I stumbled upon Hannah Teschler’s Instagram post about clean activewear swaps for ex-Lulu girls, and I fell deep into the rabbit hole of toxic clothing. At the time, I wasn’t an ex-Lulu girl. I was a very current one, who worshipped the brand and had heavily invested in their gym clothes, which I assumed were safe to wear. Turns out, Lululemon and most other activewear brands are selling clothes that are endocrine disruptors par excellence.

What exactly are endocrine disruptors?

In simple terms, they’re chemicals that mimic the shape of our hormones and slot perfectly into oestrogen (and other hormone) receptors. Once there, they block the real hormone from doing its job, and that interference cascades through everything from your metabolism and mood to your reproductive health and even your weight. For those of us in perimenopause or menopause, whose hormonal systems are already in flux, this is not a minor inconvenience. It’s a real problem.

Hannah’s posts were a treasure trove, but I did my own research too. Here’s what I found:

The uncomfortable truth about activewear

Most activewear is, quite literally, plastic. It’s made from polyester, nylon, spandex, and elastane – all petroleum derivatives. The more “functional” the fabric (moisture-wicking, anti-odour, four-way stretch), the worse it tends to be, because those performance finishes add another layer of synthetic chemistry directly against your skin.

Recycled fabrics sound virtuous, and they are better for the planet, but they’re not better for your body – they still expose you to microplastics and toxins. And those microplastics shed continuously, for the entire life of your yoga pants: every wash, every wear, every workout. Worst of all, when you sweat, your skin becomes more permeable, absorbing those particles and chemical residues like a sponge.

And don’t be fooled by brands advertising organic cotton. If they’re using conventional synthetic and often toxic dyes, those dyes can nullify the benefit entirely.

Synthetic textiles as a whole are responsible for 35% of the microplastics currently in our oceans.

Why does this matter so much?

Microplastics might be invisible to you, but certainly not to your body. These microscopic particles carry toxic chemicals that accumulate in your tissue, with some confirmed but many still unknown long-term consequences for your health. What we do know is alarming enough.

They have been found everywhere inside us. Microplastics have now been detected in human blood, the colon, the testes, the endometrium, semen, breast milk, and faeces. They’ve also been found in the liver, kidneys, placenta, and saliva. There is essentially no corner of the human body that researchers have checked and found clean.

And we’re absorbing them constantly, not just through our clothes. It’s estimated that we ingest about 5 grams of plastic particles every week – the equivalent weight of a credit card – through food, drinking water, and air.

The full picture isn’t yet complete. We’re still in the early stages of understanding exactly what microplastics do to us. But what researchers are finding so far is not reassuring.

A landmark study published in the New England Journal of Medicine in 2024 examined patients undergoing surgery to remove arterial plaque. Those who had microplastics in their plaque had a significantly higher risk of heart attack, stroke, and death than those who didn’t. A 2025 study on mice showed microplastics physically moving through the brain and blocking blood vessels, with researchers concluding that the potential long-term effects on neurological disorders such as depression are concerning.

What I find most worrying is that when microplastics and the chemical additives they carry disrupt our hormones, they can not only cause weight gain and hot flushes, they can also increase cancer risk.

It is estimated that we inhale 68,000 microplastic particles every day, with some researchers describing what’s coming as a “plastic health crisis.” And yet most of us are still doing Pilates in polyester leggings.

What now?

I know it’s a lot to take in, but it’s not all doom and gloom. More and more responsible retailers are emerging, and brands are held responsible. If you’re following the news, you might have seen that the Texas Attorney General is investigating whether Lululemon has misled consumers about the safety, quality, and health risks of its products. Lawsuits for Fabletics, Nike, and Gymshark are coming, and laws are being changed.

California banned the manufacture and sale of new athletic wear containing intentionally added PFAS, while brands in Europe are legally required to meet some of the world’s strictest standards. It’s not surprising that change is slow. It’s a big machine that needs to be turned around, and most consumers are oblivious to the danger.

Here’s my clean clothing checklist

Fabrics to avoid 🚫

• Polyester, nylon, acrylic – all petroleum-derived plastics
• Spandex, elastane, Lycra – same family, just stretchier
• Rayon and viscose – chemically processed wood pulp, not the innocent “natural” fabric it sounds like
• Bamboo fabric – almost always viscose by another name
• Anything labelled “recycled” synthetic – still plastic, still sheds microplastics

Finishes and treatments to avoid 🚫

• Water-resistant, moisture-wicking, wrinkle-free, stain-repellent, anti-odour – these are the giveaway words for chemical performance finishes, often PFAS
• “Silverescent” or antimicrobial treatments
• Anything that sounds like a superpower your fabric shouldn’t naturally have

Labels and certifications that actually mean something ✅

• GOTS (Global Organic Textile Standard) – the gold standard. Covers the entire journey from seed to finished garment: organic fibres, safe dyes, clean production, fair labour. If you only look for one label, make it this one.
• OEKO-TEX Standard 100 – tests the finished product for over 3,000 harmful substances, including every button, zip, and coating. Important caveat: a polyester garment can carry this label. It means the product won’t harm you directly, not that it was made cleanly.
• Bluesign – focuses on what happens inside the factory: dye safety, chemical inputs, and water waste. Best used alongside other certifications rather than alone.
• Nordic Swan Ecolabel – Scandinavia’s government-backed certification, covering the entire production chain and one of the few that explicitly restricts PFAS.

Note: none of these certifications are perfect, and a label is not a substitute for checking the fabric composition tag.

Better fabrics ✅

• Organic cotton (GOTS certified)
• Linen and hemp, ideally mechanically processed
• Silk – naturally protein-based and chemical-free; opt for peace silk if animal welfare matters to you
• Tencel Lyocell – plant-based, naturally moisture-wicking and breathable, which makes it one of the more promising options for activewear
• Wool, ideally non-superwashed and undyed or naturally dyed

The golden rules

• If it stretches like plastic, it probably is plastic
• “Recycled” is not the same as “safe”
• “Natural” on a label means nothing without a certification to back it up
• When in doubt, check the fabric composition tag – marketing is not your friend

I’m learning as you’re learning, so if you have any input or comments, please let me know. I already found some great European brands and will report back once I’ve tested them.

I’m determined to detox my life. Follow along as I uncover what’s actually worth spending money on and what’s just greenwashing in a prettier font.

Sources: ScienceDirect, Harvard Medicine Magazine, Stanford Medicine, World Economic Forum, MDPI, Frontiers