Does Polyester Affect Hormones?

Polyester fabric carries trace chemicals that can mimic or interfere with hormones, though the fiber itself is largely inert once formed. The concern is not the polymer chain of polyethylene terephthalate (PET) sitting against your skin. It is the residual manufacturing chemicals, absorbed pollutants, and shed microplastic particles that come along for the ride. Research has detected bisphenol A, phthalates, antimony, and other endocrine-active compounds in polyester garments, and newer studies suggest sweat dramatically increases how much of those chemicals your skin absorbs.

What Is Actually in Polyester Clothing

When researchers test polyester garments fresh off the rack, they consistently find a cocktail of chemicals left over from manufacturing or absorbed during storage and transport. Bisphenol A (BPA) is one of the most studied. A Spanish analysis of 120 new garments for pregnant women and infants found traces of BPA in every single sample, with a median concentration of about 7.4 nanograms per gram of fabric. The highest levels showed up in polyester textiles specifically.¹ A separate study testing both conventional and recycled fabrics found BPA and its substitute BPS widespread in T-shirts and socks regardless of whether the polyester was virgin or recycled, with the highest BPA concentration (625 nanograms per gram) appearing in a pair of recycled polyester socks.²

BPA is the headline chemical because of its well-documented ability to mimic estrogen, but it is not the only one. Phthalates, used as plasticizers in textile printing inks and coatings, accumulate on both cotton and polyester fabrics. A study that left fabrics exposed for 30 days measured roughly 1,950 nanograms per square decimeter of five common phthalates on polyester, and even more on cotton.³ A review examining over 120 published articles on phthalates in clothing highlighted that the chemicals raise concerns about endocrine disruption, reproductive toxicity, and potential carcinogenicity.⁴

Then there is antimony, a metalloid catalyst used to produce PET itself. Polyester fibers typically contain between about 125 and 470 micrograms of antimony per gram of fabric. Standard artificial-sweat tests showed that between roughly 0.05 and 2 percent of that antimony leached out.⁵ Antimony is not classified as an endocrine disruptor in the same way BPA is, but chronic low-level exposure is a broader health concern that researchers are still working to quantify.

Other chemicals found in polyester and synthetic textiles include benzothiazoles, commonly used as vulcanization accelerators and biocides. One study detected the benzothiazole BTH in 86 percent of textile samples tested, with concentrations ranging from about 6 to 1,120 nanograms per gram. The highest concentration of a related compound, benzotriazole, was found in a printed graphic on an infant bodysuit at 14,000 nanograms per gram.⁶ Some of these compounds are suspected endocrine disruptors, though the evidence base is thinner than for BPA or phthalates.

Sweat Changes the Equation

Dry fabric sitting on dry skin is one thing. Sweaty fabric is something else entirely. A 2025 study on children’s textiles modeled dermal exposure under sweating conditions and found that perspiration amplified chemical absorption by staggering margins: up to about 3,250-fold for per- and polyfluoroalkyl substances (PFAS) and roughly 835-fold for organophosphate esters compared to dry contact.⁷ Sweat acts as a solvent, pulling chemicals out of the fabric and into a liquid film that the skin absorbs far more readily than it absorbs anything from a dry surface. This is a detail that standard safety testing often misses, because many test protocols use standardized artificial-sweat solutions that may not replicate real-world sweating conditions well.

The implication is straightforward: activewear, which is overwhelmingly polyester, sits against sweating skin for extended periods. If the garment contains residual BPA, phthalates, or organophosphate esters, the sweat-amplified exposure could be orders of magnitude higher than dry-contact estimates suggest. This does not automatically mean dangerous levels are being reached, but it does mean that risk assessments based on dry-contact testing probably underestimate real exposure.

The Polyester Underwear Experiments

Some of the most striking research on polyester and reproduction predates the modern endocrine-disruptor conversation. In the early 1990s, an Egyptian urologist named Ahmed Shafik conducted a series of experiments that have since become minor legends in reproductive biology. In one study, dogs fitted with polyester-lined pants for 24 months experienced significant declines in sperm count and sperm motility, along with an increase in abnormal sperm forms and degenerative changes visible in testicular biopsies. When the polyester pants were removed, sperm quality gradually returned to normal in 10 of the 12 dogs. Cotton pants and no pants at all produced no such effects.⁸

Shafik followed this with a human trial. Men wore polyester sling-style suspensories (think of a fabric pouch around the scrotum), and all became azoospermic, meaning their ejaculate contained zero sperm, after an average of about 140 days. No pregnancies occurred during the suspensory-wearing period. When the suspensories were removed, sperm counts eventually recovered.⁹

Here is the twist that makes these studies particularly interesting for the hormone question: in both studies, serum reproductive hormones showed no significant change. Testosterone, FSH, and LH levels stayed statistically stable throughout. The damage to sperm production appeared to bypass the hormonal system entirely. Shafik proposed that the mechanism was electrostatic. Polyester generates static charges when it rubs against skin, and he measured electrostatic potentials averaging about 366 volts per square centimeter during the day in the human study.⁹ The hypothesis was that these electrical fields directly disrupted the cells producing sperm without triggering a hormonal cascade.

These experiments have not been widely replicated, and the electrostatic explanation remains debated. But they illustrate an important nuance: polyester can affect reproductive outcomes through mechanisms that do not show up on a standard hormone blood panel. Hormones are the body’s messaging system, but damage can also happen downstream, at the tissue level, without the messages themselves changing.

Microplastics and the Endocrine System

Polyester is the single largest source of microplastic fibers shed into the environment and into human bodies. Every wash cycle releases thousands of tiny fibers, and wearing polyester sheds fibers that can be inhaled or settle on skin. A growing body of animal research suggests that these micro- and nanoplastic particles can disrupt endocrine function. In animal models, exposure to micro- and nanoplastics has been shown to alter reproductive hormones, increase inflammatory markers, and trigger oxidative stress in reproductive organs including the gonads and thyroid glands.¹⁰

The leap from animal studies to human health claims is always uncertain. Doses used in laboratory experiments often exceed what people encounter in daily life, and the body’s ability to clear or tolerate low-level exposures may buffer against the effects seen in rodent studies. Still, the sheer volume of microplastic exposure from polyester clothing, estimated at millions of fibers per garment per year of use, means that even small per-fiber effects could accumulate. Researchers have found polyester microfibers in human blood, lung tissue, and placental tissue, so the exposure is not hypothetical.

PET and Estrogenic Activity in Lab Tests

Separate from what is embedded in finished garments, PET plastic itself appears capable of leaching compounds with estrogenic activity. A study using a yeast-based estrogen screen found that water bottled in PET containers showed significantly more estrogenic activity than water stored in glass. To confirm the plastic was the source, researchers filled empty PET and glass bottles with culture medium and incubated freshwater snails for 56 days. Snails in the PET bottles produced significantly more embryos than those in glass, across all brands tested.¹¹

PET water bottles and PET clothing fibers are made from the same base polymer, so the finding is relevant even though the experiment focused on beverage containers. The identity of the specific estrogenic compound or compounds leaching from PET has not been conclusively pinned down. Some researchers suspect it is related to antimony or to oligomers (short polymer chains) that break free during manufacturing or degradation. Whatever the source, the biological signal is real enough that it shows up in two completely different bioassays.

What This Means for Women’s Reproductive Health

Most of the chemicals found in polyester textiles, particularly BPA, phthalates, and certain organophosphate esters, are classified as endocrine-disrupting chemicals. Epidemiological evidence links exposure to these compounds with reduced fertility in women through several pathways. Reviews of the literature report that BPA exposure is associated with lower estradiol levels and reduced oocyte quality, phthalate exposure is linked to lower antral follicle counts and reduced implantation and live birth rates, and parabens (another class of EDCs sometimes found in textile finishes) are associated with reduced clinical pregnancy rates.¹² These effects have been documented in both animal models and in women undergoing assisted reproduction, where chemical exposures can be measured alongside detailed fertility outcomes.¹³

A critical caveat: clothing is only one of many exposure routes for these chemicals. You encounter BPA from receipt paper, canned food linings, and dozens of other products. Phthalates are in personal care products, food packaging, and household dust. Teasing out how much of someone’s total EDC burden comes from their wardrobe versus their diet or cosmetics is extremely difficult. Still, for someone who wears tight-fitting polyester activewear while sweating for hours daily, the dermal contribution is plausible enough to warrant attention.

Workers in the Textile Industry

Occupational studies offer a window into what higher-dose textile chemical exposure looks like. A study of female textile dye workers in Nigeria found measurable hormonal differences compared to unexposed women. In the follicular phase, exposed workers in their thirties had higher estradiol levels than unexposed women. In the luteal phase, both progesterone and estradiol were elevated in exposed workers in that same age group. Prolactin, meanwhile, showed a significant inverse relationship with duration of exposure, meaning the longer women worked in the industry, the lower their prolactin levels tended to be.¹⁴

These workers handled dyes and chemical finishes directly, so their exposure was far heavier than what a consumer gets from wearing a finished garment. But the study demonstrates that textile chemicals can alter hormonal profiles in real-world conditions, not just in lab dishes. It also shows that different hormones respond in different directions, which complicates the narrative that EDCs simply “raise” or “lower” hormones. The disruption is more like noise injected into a finely tuned system.

Babies and Pregnant Women Face Higher Risk

Infants present a worst-case scenario for dermal chemical exposure from textiles. Their skin is thinner and more permeable than adult skin, their body surface area is large relative to their weight, and they spend long hours in close contact with clothing and bedding. The finding that BPA was detected in every one of 120 garments tested for pregnant women and infants, with polyester items carrying the highest concentrations, is concerning precisely because of this vulnerability.¹ Pregnant women are another vulnerable group, since endocrine-disrupting chemicals can cross the placenta and affect fetal development during windows when the hormonal environment is critical for organ formation.

A 2025 review of the evidence spanning 2019 to 2025 concluded that chronic exposure to chemical mixtures in textiles remains poorly understood, with current safety assessments often neglecting the combined effects of multiple chemicals acting together. The review called for stronger enforcement of textile certifications and greater public awareness of the risks.¹⁵ This gap matters because real garments do not contain just one chemical. A single polyester baby onesie might carry traces of BPA, antimony, benzothiazoles, and phthalates simultaneously, and the safety limits for each chemical were set individually, without accounting for what happens when they act together.

Practical Steps That Actually Help

Washing new clothes before wearing them is the simplest and most effective step you can take. Many of the surface chemicals on textiles are water-soluble or loosely bound, and a single wash cycle removes a meaningful fraction of them. The phthalate study mentioned earlier found that laundering released substantial amounts of accumulated chemicals into wash water, confirming that the chemicals do come off the fabric.³ This does not eliminate everything, particularly antimony embedded in the fiber itself, but it reduces surface contamination.

Beyond washing, a few other strategies are worth considering:

Choose certified textiles: Labels like OEKO-TEX Standard 100 and GOTS (Global Organic Textile Standard) test finished products for restricted chemicals, including BPA and certain phthalates. They are not perfect, but they provide a baseline that unregulated garments do not.
Favor natural fibers for prolonged skin contact: Cotton, linen, wool, and silk do not contain antimony catalysts and tend to carry lower levels of BPA. For sleepwear, underwear, and infant clothing, natural fibers reduce dermal exposure.
Be skeptical of “recycled polyester” as safer: The study of recycled fabrics found BPA and BPS at levels comparable to or higher than conventional polyester. Recycling processes can introduce additional chemical contamination rather than removing it.

None of this means you need to throw out every polyester garment you own. The dose from a single shirt worn for a few hours is unlikely to cause measurable hormonal effects. The concern is cumulative, especially for people who wear polyester against skin for most of the day, who exercise heavily in synthetic activewear, or who dress infants primarily in synthetic fabrics. Small changes in fabric choices for the garments with the most skin contact and the longest wear times are where the practical benefit lives.

Why Regulation Has Not Caught Up

Textile chemical regulation varies wildly by country. The European Union’s REACH framework restricts certain chemicals in consumer products, and the EU has set specific migration limits for some substances from food-contact plastics. But clothing is not food-contact plastic, and many of the same chemicals that are tightly regulated in food packaging go largely unmonitored in garments. The United States has even fewer textile-specific chemical restrictions. The Consumer Product Safety Commission regulates flammability and a handful of banned substances like certain azo dyes, but there is no systematic screening of garments for BPA, phthalates, or antimony before they reach store shelves.

Researchers have pointed out that current safety assessments treat each chemical in isolation, while real-world exposure involves mixtures of multiple compounds acting on the same hormonal pathways simultaneously.¹⁵ A BPA level below the individual safety threshold and a phthalate level below its threshold might combine to push total estrogenic load above a biologically meaningful level. Mixture toxicology is notoriously difficult to regulate because the number of possible chemical combinations is essentially infinite, but the gap between how we test textiles and how people actually wear them is one of the more significant blind spots in consumer product safety.

1
PubMed. Dermal exposure to bisphenols in pregnant women’s and baby clothes: Risk characterization
2
PubMed Central. Bisphenols in daily clothes from conventional and recycled material: evaluation of dermal exposure to potentially toxic substances
3
PubMed. From Clothing to Laundry Water: Investigating the Fate of Phthalates, Brominated Flame Retardants, and Organophosphate Esters
4
Science of The Total Environment. Phthalate esters in clothing: A review
5
Regulatory Toxicology and Pharmacology. Antimony release from polyester textiles by artificial sweat solutions: A call for a standardized procedure
6
PubMed. Occurrence of and exposure to benzothiazoles and benzotriazoles from textiles and infant clothing
7
Science of The Total Environment. Sweat-amplified dermal transfer and combined toxicity of per- and polyfluoroalkyl substances and organophosphate esters mixtures in children’s textiles
8
PubMed. Effect of different types of textile fabric on spermatogenesis: an experimental study
9
Contraception. Contraceptive efficacy of polyester-induced azoospermia in normal men
10
Toxicology Mechanisms and Methods. Nano and microplastics: unveiling their profound impact on endocrine health
11
Environmental Health Perspectives. Polyethylene Terephthalate May Yield Endocrine Disruptors
12
PubMed. Exposure to modern, widespread environmental endocrine disrupting chemicals and their effect on the reproductive potential of women: an overview of current epidemiological evidence
13
PubMed Central. Implications of environmental toxicants on ovarian follicles: how it can adversely affect the female fertility?
14
PubMed Central. Effect of occupational exposure to vat-textile dyes on follicular and luteal hormones in female dye workers in Abeokuta, Nigeria
15
PubMed. Human health risks from textile chemicals: a critical review of recent evidence (2019-2025)