Why the label matters

What a garment is made of affects what it sheds, how it smells, and what is left when it's gone. Here is what the research supports, and where it doesn't.

What synthetics shed

Polyester, acrylic and nylon are plastics spun into thread. When they are washed, they shed microscopic fibers. One lab study estimated about 496,000 fibers from a 6 kg load of polyester and about 729,000 from acrylic; a polyester-cotton blend shed noticeably less¹. A single polyester garment has been measured releasing more than 1,900 fibers in one wash².

Shedding is not only a laundry problem. One lab study found that simply wearing polyester garments released fibers to the air in the same order of magnitude as washing them³, and synthetic fibers have been collected in urban air fallout⁴.

The International Union for Conservation of Nature estimates that laundering synthetic textiles is the largest single source of primary microplastics reaching the ocean, about 35% in its central scenario. That is a modelled estimate with a wide range, and it covers primary microplastics, not all ocean plastic⁵.

Natural fibers shed too. In a lab study funded by Cotton Incorporated, cotton and rayon fabrics released more microfibers in the wash than polyester⁶. The difference is what those fibers are: cotton and wool are not plastic.

Where the fibers go

Polyester fibers that look like clothing fibers have been found across the Arctic Ocean. In samples from 71 stations, 73% of the synthetic fibers were polyester, and they were found as deep as 1,015 meters. The authors point to laundry as the likely source, though that is not proven⁷.

The full picture is more mixed than the headline. In a global survey of about 2,000 fibers from ocean surface water, only about 8% were synthetic; most were cellulose (largely cotton, grouped with plant-based fibers such as viscose) or wool⁸. So the honest claim is not that natural fibers stay out of the sea. It is that they are not plastic, which matters for what happens next.

Breaking down, or not

In lab tests, cotton, wool and viscose fibers biodegrade in water, soil or compost, while polyester, nylon and polypropylene barely break down. Cotton fibers degraded in aquatic tests where polyester persisted, in the Cotton Incorporated-funded study above⁶. Cotton fabric lost substantial weight over three months in compost and soil while polyester stayed largely intact, in a study with a Cotton Incorporated co-author⁹. Over 90 days in seawater, wool and viscose biodegraded readily and the synthetics showed virtually none, in a study funded by Australian Wool Innovation¹⁰.

The results agree with one another, but the direct comparisons were paid for by the cotton and wool industries, and real-world breakdown is slower than in a lab, especially for dyed or finished fabric⁸.

End of life matters because so little clothing is reused as fiber. Less than 1% of the material used to make clothing is recycled into new clothing, and most of it ends up in landfill or incineration¹¹.

Odor and everyday wear

Polyester tends to hold body odor more than cotton, and wool tends to hold the least. After a spinning class, polyester shirts smelled stronger and less pleasant than cotton ones¹², and independent lab and review work ranks the fibers the same way, while noting that fabric structure matters too^13,14.

That may change how often things get washed. In wardrobe survey data, wool sweaters were worn about twice as long between washes as cotton ones, which saves water and energy. This review was co-funded by Australian Wool Innovation¹⁵.

Natural fibers also hold far more moisture: wool about 13.6% of its weight and cotton 8.5%, against 0.4% for polyester¹⁵. That is a trade-off rather than a win. It is also why polyester dries faster.

Comfort: smaller differences than you'd think

Studies of exercise in heat and in cold find that fabric type makes little difference to body temperature, heart rate or how people feel^16,17,18. Fit, weight and construction matter more than whether the fiber is natural. We don't claim natural fibers keep you cooler or warmer.

Heat and flame

Polyester and nylon melt when they burn and can stick to skin. US Marine commanders in Iraq banned synthetic athletic wear outside bases for this reason, in a combat setting with fires and blasts rather than everyday risk¹⁹. Wool is hard to ignite and does not melt; the wool industry's trade body gives its ignition temperature as 570 to 600 °C, against 255 °C for cotton²⁰. Cotton does not melt, but it does catch fire easily.

Finishes matter as much as fiber

What is applied to a fabric can matter as much as the fiber itself. BPA has been found in polyester infant socks²¹ and, in one advocacy group's own testing, which is not peer-reviewed, in polyester-spandex activewear²². It has also been found at high levels in cotton-rich socks²³. PFAS from stain-repellent finishes turned up in every stain-resistant school uniform tested, and at higher levels in 100% cotton uniforms than in blends²⁴.

Disperse dyes, used mainly on polyester, nylon and acetate, are among the most common causes of clothing-related skin allergy, though they affect a minority of people²⁵. None of this makes synthetic clothing toxic or natural clothing chemical-free. It is why a composition label tells only part of the story.

The costs of natural fibers

Conventional cotton is thirsty. Global cotton consumption was estimated to need about 256 billion cubic meters of water a year, with heavy impacts in water-stressed regions such as the Aral Sea basin, based on data from 1997 to 2001²⁶. Cotton covers about 2.4% of cultivated land but used about 4.7% of the world's pesticides and 10% of its insecticides in 2019²⁷.

Wool has a high climate footprint per kilogram. Australian merino came to about 20 kg of CO₂e per kg of greasy wool at the farm gate, mostly from sheep methane. The figure moved up to threefold depending on how emissions were split between wool and meat, and the study was funded by Australian Wool Innovation²⁸.

“Natural-sounding” is not the same as natural. Viscose, modal and lyocell are made by dissolving plant cellulose, usually wood pulp, and spinning it into new fiber. They are often marketed as natural or as “bamboo”; the US Federal Trade Commission fined Kohl's and Walmart a combined $5.5 million for selling rayon as bamboo with false environmental claims²⁹. FabricTruth counts these regenerated fibers as non-natural in every score, as the scoring page explains.

Labels can also be gamed. The Global Organic Textile Standard found faked transaction certificates covering about 20,000 metric tons of supposedly organic cotton from India³⁰.

And synthetics have real strengths. They are stronger, dry faster and suit swimwear, rain shells and technical layers. In one wardrobe survey, synthetic garments were reported to last longer than 100% cotton ones¹⁵. We don't claim natural fibers last longer.

Why we don't use footprint scores

Fiber choice is only part of a garment's footprint. Across the apparel industry, dyeing and finishing and yarn preparation account for more climate impact than growing or making the fiber³¹.

Popular fiber scorecards such as the Higg Materials Sustainability Index measure production only, from cradle to gate, using global averages. Norway's consumer authority found marketing based on Higg MSI misleading, saying such data cannot support claims about individual products and the index is not meant to compare different fiber types³². The coalition behind the index then paused its consumer-facing program and commissioned an independent review³³. These tools also leave out wear, washing, lifespan and microfibers¹⁵.

So FabricTruth scores one thing we can read and cite: the fiber composition on the label. It is not a footprint score, and not a medical or environmental certification.

Sources

Industry funding is noted where a study was paid for or co-authored by a fiber industry body. Links checked October 2026.

1. 1Napper, Thompson (University of Plymouth). Release of synthetic microplastic plastic fibres from domestic washing machines. Marine Pollution Bulletin, 2016.
2. 2Browne, Crump, Niven, Teuten, Tonkin, Galloway, Thompson. Accumulation of microplastic on shorelines worldwide: sources and sinks. Environmental Science & Technology, 2011.
3. 3De Falco, Cocca, Avella, Thompson. Microfiber release to water, via laundering, and to air, via everyday use. Environmental Science & Technology, 2020.
4. 4Dris, Gasperi, Saad, Mirande, Tassin. Synthetic fibers in atmospheric fallout: a source of microplastics in the environment?. Marine Pollution Bulletin, 2016.
5. 5Boucher, Friot. Primary Microplastics in the Oceans: a Global Evaluation of Sources. IUCN, 2017.
6. 6Zambrano et al. (NC State, Cotton Incorporated). Microfibers generated from the laundering of cotton, rayon and polyester based fabrics and their aquatic biodegradation. Marine Pollution Bulletin, 2019. Funded by Cotton Incorporated; two co-authors from Cotton Incorporated.
7. 7Ross et al. (Ocean Wise, Fisheries and Oceans Canada). Pervasive distribution of polyester fibres in the Arctic Ocean is driven by Atlantic inputs. Nature Communications, 2021.
8. 8Suaria et al.. Microfibers in oceanic surface waters: a global characterization. Science Advances, 2020.
9. 9Li, Frey (Cornell), Browning (Cotton Incorporated). Biodegradability study on cotton and polyester fabrics. Journal of Engineered Fibers and Fabrics, 2010. Cotton Incorporated co-author.
10. 10Collie, Brorens, Hassan, Fowler (AgResearch). Marine biodegradation behavior of wool and other textile fibers. Water, Air, & Soil Pollution, 2024. Funded by Australian Wool Innovation; fabrics supplied by Woolmark.
11. 11Ellen MacArthur Foundation. A New Textiles Economy: Redesigning fashion’s future. Report, 2017.
12. 12Callewaert et al. (Ghent University). Microbial odor profile of polyester and cotton clothes after a fitness session. Applied and Environmental Microbiology, 2014.
13. 13McQueen, Laing, Brooks, Niven (University of Otago). Odor intensity in apparel fabrics and the link with bacterial populations. Textile Research Journal, 2007.
14. 14Laing (University of Otago). Natural fibres in next-to-skin textiles: current perspectives on human body odour. SN Applied Sciences, 2019.
15. 15Laitala, Klepp (SIFO, OsloMet), Henry (QUT). Does use matter? Comparison of environmental impacts of clothing based on fiber type. Sustainability, 2018. Co-funded by Australian Wool Innovation and the Research Council of Norway; lifespan data from an AWI-commissioned survey.
16. 16Gavin et al.. Clothing fabric does not affect thermoregulation during exercise in moderate heat. Medicine & Science in Sports & Exercise, 2001.
17. 17Gavin. Clothing and thermoregulation during exercise. Sports Medicine, 2003.
18. 18Cernych et al. (Lithuanian Sports University). Physiological and psychological responses during exercise and recovery in a cold environment is gender-related rather than fabric-related. Frontiers in Psychology, 2017.
19. 19US Marine Corps, 1st Marine Logistics Group. Popular clothing off-limits to Marines in Iraq. DVIDS, 2006.
20. 20International Wool Textile Organisation. Wool & Fire (fact sheet). Wool trade body, c. 2020. Published by the wool industry’s trade body.
21. 21Xue, Liu, Kannan (New York State Department of Health). Bisphenols, benzophenones, and bisphenol A diglycidyl ethers in textiles and infant clothing. Environmental Science & Technology, 2017.
22. 22Center for Environmental Health. New testing shows high levels of BPA in sports bras and athletic shirts. Press release (advocacy group; not peer-reviewed), 2022.
23. 23Freire et al. (University of Granada). Concentrations of bisphenol A and parabens in socks for infants and young children in Spain. Environment International, 2019.
24. 24Xia et al. (Indiana University, University of Toronto, Notre Dame and others). Per- and polyfluoroalkyl substances in North American school uniforms. Environmental Science & Technology, 2022.
25. 25Malinauskiene et al. (Lund University). Contact allergy from disperse dyes in textiles: a review. Contact Dermatitis, 2013.
26. 26Chapagain, Hoekstra, Savenije, Gautam (University of Twente, UNESCO-IHE). The water footprint of cotton consumption. Ecological Economics, 2006.
27. 27Pesticide Action Network UK. Pesticide concerns in cotton. NGO web page, citing ICAC data, current.
28. 28Wiedemann, Yan, Henry, Murphy. Resource use and greenhouse gas emissions from three wool production regions in Australia. Journal of Cleaner Production, 2016. Funded by Australian Wool Innovation.
29. 29US Federal Trade Commission. FTC seeks largest-ever civil penalty for bogus bamboo marketing from Kohl’s and Walmart. Press release, 2022.
30. 30Global Organic Textile Standard. GOTS detects evidence of organic cotton fraud in India. Press release, 2020.
31. 31Quantis, for ClimateWorks Foundation. Measuring Fashion: Environmental impact of the global apparel and footwear industries. Report (UNCCD-hosted copy), 2018.
32. 32Norwegian Consumer Authority, with the Netherlands ACM. Consumer authorities issue guidance on environmental claims to the textile industry. Regulator guidance, 2022.
33. 33Sustainable Apparel Coalition (now Cascale). Statement from the SAC regarding the Norwegian Consumer Authority and environmental claims. Industry statement, 2022.