Polyester itself, the plastic fiber, isn’t known to interfere with hormones. The concern is the chemicals that can ride along in the fabric, and some of them, such as BPA, are recognized hormone disruptors that turn up in many everyday garments. Finding a chemical in a shirt is different from showing that wearing the shirt harms your hormones, and that second step is where the evidence is still thin. Simple precautions make sense; alarm doesn’t.
Why the Fabric and Its Chemicals Are Two Different Questions
An endocrine disruptor is a chemical that can mimic, block, or change the body’s hormones, such as estrogen or thyroid hormone. Polyester is a plastic made of long chain molecules too large to slip into cells the way hormones do. In lab tests, tiny polyester particles showed no hormone activity when tested on their own.1PubMed Central. Surface-driven endocrine activity of nanoplastics: polymer- and size-dependent estrogen and androgen receptors modulation without steroidogenesis perturbation So the hormone question is really about what else is in or on the fabric.
Plastics are really two things, the backbone polymer and the small molecules mixed in or left over. Hormone-active chemicals such as BPA and phthalates belong to the second group.
Several kinds of substances can come along with the fiber. Polyester is usually made using antimony as a catalyst, so traces stay in the fibers.2PubMed. Antimony release from polyester textiles by artificial sweat solutions: A call for a standardized procedure Clothing can also contain BPA, phthalates, and dyes added or picked up during manufacturing.3PubMed. Phthalate esters in clothing: A review4PubMed. Widespread Occurrence of Bisphenol A in Daily Clothes and Its High Exposure Risk in Humans Antimony isn’t mainly a hormone concern, and the amount that moves into artificial sweat is only about 0.05% to 2% of what’s in the fabric.5PubMed. Antimony release from polyester textiles by artificial sweat solutions: A call for a standardized procedure
Dyeing, printing, and finishing add dyes, softeners, and coatings, and some of these affect hormones. Recycled polyester can bring in chemicals from the other plastics it was made from, because the source material wasn’t always pure polyester.
BPA Is the Main Hormone Disruptor Found in Polyester Clothes
BPA (bisphenol A) is a chemical that can act like estrogen in the body. It was found in every used garment tested in one survey, at a typical level of about 34 nanograms per gram of fabric.6PubMed. Widespread Occurrence of Bisphenol A in Daily Clothes and Its High Exposure Risk in Humans A related chemical, BPS, turned up in about 3 in 10 of those garments.7PubMed. Widespread Occurrence of Bisphenol A in Daily Clothes and Its High Exposure Risk in Humans In clothes for pregnant women and babies, BPA traces appeared in every sample, highest in polyester.8PubMed. Dermal exposure to bisphenols in pregnant women’s and baby clothes: Risk characterization
A T-shirt weighs roughly 150 grams, which means the whole shirt holds only a few millionths of a gram of BPA at that typical level. Only part of that moves onto skin, and only part of that is absorbed, so the amount reaching your bloodstream is smaller still.
Levels vary widely. Most garments carry small amounts, but a few new garments reached over 1,800 nanograms per gram.9PubMed. Widespread Occurrence of Bisphenol A in Daily Clothes and Its High Exposure Risk in Humans The typical level in used clothes was higher than in new clothes, about 34 versus 18 nanograms per gram.10PubMed. Widespread Occurrence of Bisphenol A in Daily Clothes and Its High Exposure Risk in Humans
Sweat and skin contact are how it reaches you. Chemicals in fabric can move onto skin, especially when the fabric is damp with sweat.11Environmental Science & Technology Letters. Characterization of Chemical Additives in Daily Clothing Regarding Human Exposure and Environmental Emissions For one clothing additive, sweaty clothes accounted for about 39% of a person’s total exposure.12Environmental Science & Technology Letters. Characterization of Chemical Additives in Daily Clothing Regarding Human Exposure and Environmental Emissions
Food and drink packaging, such as can linings and some plastic containers, is generally considered the bigger daily source of BPA for most people. Clothing adds to that background rather than replacing it. Researchers are still working out how large the clothing share is, and because skin absorbs BPA differently from swallowed food, the numbers can’t simply be compared side by side.
Phthalates and Dyes in Some Garments
Phthalates are chemicals used to make plastics soft and flexible, including in some clothing.13PubMed. Phthalate esters in clothing: A review They’re linked to hormone disruption and reproductive harm.14PubMed. Phthalate esters in clothing: A review They’re more likely in plastic-style prints, logos, and coated fabrics than in plain fibers. In an EU check of clothing, footwear, and textiles, about 1 in 5 items could be a significant source of phthalates or similar chemicals because they broke EU limits.15PubMed. Unveiling the Chemical Safety of Clothing Articles, Textiles and Footwear With Regard to the Presence of Carcinogenic, Mutagenic, or Reprotoxic Substances, Endocrine Disruptors and Skin Sensitizers Under EU Regulatory Restrictions The EU limits certain phthalates and dyes in clothing, while rules and enforcement differ in other countries and with cheap online imports.
A few habits help you spot likelier culprits. Thick, rubbery, or raised screen prints and logos are the most likely spots, because plasticizers keep that kind of plastic ink soft and stretchy. Shiny, coated, or vinyl-like fabrics, such as some raincoats and faux-leather trims, are soft plastic and may contain phthalates. This is a tendency, not a test: you can’t confirm what is in a print by looking at it. Plain fabric in a light color or undyed form generally has fewer dyes, prints, and finishes, so there are fewer places for additives to come from.
Some dyes carry their own risks. Some azo dyes used on textiles can damage DNA and have disrupted sperm production in lab studies.16SpringerLink (Environ Sci Pollut Res Int). Hues of risk: investigating genotoxicity and environmental impacts of azo textile dyes Many azo dyes are restricted in the EU, though, and they aren’t used on all polyester.
Does Polyester Underwear Affect Sperm
Older studies raised this concern. In dogs that wore polyester pants for 24 months, sperm count and movement dropped, while cotton showed no change.17PubMed. Effect of different types of textile fabric on spermatogenesis: an experimental study Hormone levels in those dogs did not change, and sperm improved after the pants came off in most dogs.18PubMed. Effect of different types of textile fabric on spermatogenesis: an experimental study In a small study of men wearing a polyester scrotal sling for 24 weeks, sperm counts fell below normal.19Medical Journal of Indonesia. Polyester sling scrotal cover induces oligozoospermia in normal Indonesian men
Both studies used polyester worn against the body for a long time in a way ordinary underwear doesn’t, and they are old, small, and unconfirmed. Because the dogs’ sperm dropped without any change in hormone levels, if there’s an effect, it doesn’t look like hormone disruption. A more likely explanation is that synthetic fabric holds in heat, though these studies don’t prove that either.
For men trying to conceive, switching to loose cotton underwear costs little and has no downside, so it’s a reasonable precaution even with weak evidence. Sperm take about three months to renew, so any change in habits needs that long to show up in a test.
Babies, Pregnancy, and Higher Exposure
Some baby items carry high BPA. Socks had the highest BPA of textiles tested, with one 97% polyester infant sock reaching 13,300 nanograms per gram.20ACS Publications (Environmental Science & Technology). Bisphenols, Benzophenones, and Bisphenol A Diglycidyl Ethers in Textiles and Infant Clothing
Babies get more from the same clothing for several reasons. A smaller body means the same amount of chemical on the skin is a larger dose for their weight. They spend long hours in the same bodysuits and sleepwear, with thinner skin in constant contact. They also mouth and chew on fabric, which adds a swallowing route adults don’t have with their clothes. Infants also take in more indoor microplastic dust per body weight than adults, by breathing and swallowing.21PubMed. International quantification of microplastics in indoor dust: prevalence, exposure and risk assessment And because hormones guide growth and development, disruption matters more during pregnancy and infancy than in adulthood.
For baby clothes, pick cotton or certified fabrics for items worn against skin all day, and wash new pieces before first use. Be careful with socks and anything a baby chews. You don’t need to throw out everything polyester.
Pregnant women can follow the same simple steps as everyone. Clothing is one of several sources, not the main one, so it’s worth talking with a doctor about bigger sources like food packaging.
Is Recycled Polyester Worse
Recycled polyester often comes from mixed plastic bottles and waste, and the other plastics in that stream can bring their own additives. Recycling doesn’t always remove those chemicals completely, so some can end up in the finished fiber. One analysis found BPA about twice as high in recycled fabrics, 13.5 versus 7.7 nanograms per gram.22Orbasics. Is Recycled Polyester Harmful to Human Health? Safety Facts & Myths23PubMed Central. Bisphenols in daily clothes from conventional and recycled material: evaluation of dermal exposure to potentially toxic substances Both values are low compared with the highest garments tested, so recycled fabric isn’t automatically the risky choice.
Its environmental benefit is real, since it keeps plastic waste out of landfill and reduces the need for new material. A certification label tells you more about chemical content than whether the fabric is recycled or new, because certified items are tested for listed harmful substances. For skin-tight items or baby clothes, a certified label is the safer bet. For a recycled fleece jacket worn over other layers, the difference matters little.
Microplastic Fibers and What Is Still Unknown
Clothes and furnishings shed fibers during wear, washing, and drying, and these settle into household dust. Indoor dust contains many polyester fibers, especially in wealthier countries.24PubMed. International quantification of microplastics in indoor dust: prevalence, exposure and risk assessment People take in microplastics by breathing, swallowing dust, and skin contact.25Journal of Advanced Research in Micro and Nano Engineering. Systematic Review on Indoor Microplastics: Unveiling Sources, Exposure Pathways, and Human Health Implications Skin is a smaller route, but harder to measure than air and dust. Plastic particles have been found in the blood of most people in one small test,26Plastic Pollution Coalition. The Plastic We Wear: Hidden Fibers, Chemical Dyes, and the Future of Clean Textiles and fibers have been found in human blood, stool, and urine.27Sustainability. Microfiber Fragment Pollution: Sources, Toxicity, Strategies, and Technologies for Remediation That shows they can enter the body and pass through it, but not that they cause harm.
Polyester fibers can soak up cancer-causing chemicals from their surroundings in the lab,28Applied Water Science. Evaluation of the adsorption efficiency of carcinogenic PAHs on microplastic (polyester) fibers—preliminary results but that doesn’t prove they deliver those chemicals inside a person. Metals leaching from polyester fibers were far below safe daily limits,29PubMed. Leaching of heavy metals from polyester microplastic fibers and the potential risks in simulated real-world scenarios so the evidence points in different directions. Newborns with more of certain plastics in the placenta had lower thyroid hormone levels, though not linked to polyester specifically.30Elsevier / Ecotoxicology and Environmental Safety. Placental microplastics contamination and its impact on thyroid function in newborns
To cut fiber exposure at home, vacuum with a filter and dust with a damp cloth. Air out rooms and dry clothes in ventilated spaces. Washing fleece less often and on cooler cycles reduces lint.
Simple Ways to Lower Your Exposure
Avoid rewearing sweaty clothes, since sweat helps chemicals move onto skin.31Environmental Science & Technology Letters. Characterization of Chemical Additives in Daily Clothing Regarding Human Exposure and Environmental Emissions Wash new clothes before wearing, which can remove some surface chemicals. Choose cotton or natural fibers for underwear, socks, and baby clothes, though natural fibers can also carry dyes and finishes. Look for OEKO-TEX or GOTS labels, certifications that test for harmful substances.32PubMed. Human health risks from textile chemicals: a critical review of recent evidence (2019-2025)
The OEKO-TEX label tests finished textiles for a list of harmful chemicals, so it speaks to what is in the garment you buy. GOTS covers organic natural fibers and restricts the chemicals used in processing, so it applies to cotton, wool, and similar materials, not to polyester. Neither label means zero chemicals; they mean limits were set and checked. Vague “eco” or “natural” wording isn’t certification, so look for the named label.
Activewear and polyester outerwear are fine for most people. Focus your effort on items worn tight, for long hours, or by babies.