If you have not heard of BPA showing up in women's underwear, you are not alone. The story has been quiet, considering what it found.

In late 2024, lab testing of common women's underwear brands sold in Europe found that up to 30 per cent of samples contained BPA, bisphenol A, a known endocrine disruptor. Around 10 per cent of the underwear tested contained BPA at levels above what regulators consider safe. The story was reported by Euronews and a handful of other European outlets, and was largely shrugged off by the underwear industry.

Thanks to the recent Netflix Documentary, podcasts from Culture Apothecary and law suits from the state of Texas against Lulu Lemon, its being shrugged off less.

What BPA does in the body

BPA is a chemical used in the production of certain plastics and synthetic materials. It mimics oestrogen in the body, which is why it is classified as an endocrine disruptor. Long-term exposure has been linked to hormonal imbalances, fertility issues and metabolic effects, particularly during pregnancy and adolescence.

Most people associate BPA with plastic water bottles or food containers. The link to clothing is newer in public awareness. BPA can be present in synthetic fabric blends, in elastic compounds, and in certain dye and finish chemistries used during manufacturing. Underwear is in continuous contact with some of the most absorbent skin on the body. The vulvar tissue is more permeable than skin elsewhere, which means residues from underwear can be absorbed at higher rates than residues from a t-shirt or a pair of jeans.

How BPA gets into underwear

The presence of BPA in underwear is not deliberate. No brand sets out to put endocrine disruptors in their knickers. The contamination comes from three places.

Synthetic fibre production. Polyester, nylon and elastane all involve petrochemical processing where BPA-related compounds are used at various stages. Trace amounts can remain in the finished fibre.

Elastic compounds. The elastic at the waistband and leg openings is often where the highest BPA concentrations are found. Synthetic elastic uses chemistry that can include BPA-related stabilisers. This was the single most contaminated component in the Euronews testing.

Fabric finishes and dyes. The chemistries used to make fabrics colour-fast, wrinkle-resistant and softer can introduce BPA-related compounds. These are often invisible on the label, because they describe the process rather than the materials. There are 'acceptable' levels of formaldehyde for example, that don't need to be mentioned at all in labelling. 

The common thread, literally and figuratively, is synthetic fibre. The brands that tested cleanest in the Euronews study were the ones using natural fibre throughout, including elastic and thread.

Why this is more alarming than it sounds

For most women, exposure through underwear is low and probably manageable. For pregnant women, women undergoing fertility treatment, women with hormonal conditions like endometriosis or PCOS, and adolescent girls whose bodies are most sensitive to endocrine disruption, even low-level exposure is worth avoiding.

Microplastics from synthetic clothing have now been detected in human blood, breast milk and placentas. BPA in underwear sits at the same end of that conversation. Synthetic fibres against permeable skin, every day, for decades. The cumulative load is non-trivial, and the regulatory framework is not yet built to address it.

What to look for on a label

Most underwear labels list only the main fabric composition. The elastic, lining and trim are often invisible on the label but make up a significant proportion of what touches the skin. When you are checking for BPA-related risk, look for these specifics:

• Main fabric percentage. 100% organic cotton or 100% TENCEL is the cleanest option.
• Spandex / elastane content. Anything above 0% means synthetic in the main fabric.
• Disclosed elastic type. If the brand discloses natural rubber, that is a good sign. If they do not disclose, assume synthetic.
• Sewing thread. Almost always polyester unless the brand specifically calls out cellulose thread.
• Lining at the gusset. The crotch lining is is usually cotton even in synthetic briefs, but does if offer full coverage? This is the most permeable contact point and the most worth checking.
• Certifications. GOTS or OEKO-TEX certifications cover the fabric processing chemistry, but neither covers elastic in the same depth. Read the small print.

What we did differently

Our compostable underwear is built from 100% natural fibre throughout: organic cotton or TENCEL in the main fabric, natural rubber elastic knitted into organic cotton at the waistband and legs, and 100% cellulose thread holding the seams. There is no synthetic anywhere, which means there is no carrier for BPA-related compounds either.

This took us years to engineer, because the supply chain for natural rubber elastic and cellulose thread is small and most factories prefer the synthetic alternatives. The result is underwear that is so clean it can be eaten by worms at end of life and that we can wear without worrying about what is leaching into the most absorbent skin on the body. Our regular briefs are the simplest version of the range.

What to do with the underwear you already own

You do not need to throw out your drawer. BPA exposure through clothing is cumulative rather than acute, and minor exposure for short periods is unlikely to cause harm.

If you want to reduce exposure, start with the underwear you wear most often, everyday briefs and your most-worn bra, and replace those with natural fibre alternatives first. Wash new garments before wearing them, which reduces residual chemistry from manufacturing. Avoid fabric softener, which can coat the fibres in additional residue.

Over time, as you replace pieces, the synthetic underwear in your drawer rotates out. There is no urgency to replace everything at once. The underwear you wear during pregnancy, breastfeeding, fertility treatment or any hormonal-cycle-sensitive period is the underwear most worth replacing first. Everything else can wait until the synthetic pieces wear out on their own.