Non-Toxic Activewear: Why Recycled Polyester Still Sheds Microplastics

If you’re shopping for non-toxic, plastic-free activewear, you’ve probably noticed how many leggings and gym shirts are now labeled “recycled ocean plastic” or “made from plastic bottles.” Recycled polyester sounds like the responsible choice, and it does keep some bottles out of landfills for longer. It’s still polyester, though, and a December 2025 lab study found it sheds more microplastic fibers in the wash than new polyester does.

A good place to start is the next pair of gym shorts you were going to buy anyway. Several brands now make them from natural fibers like organic cotton and merino wool.

Does recycled polyester shed more microplastics than new polyester?

Yes, according to that study. The Microplastic Research Group at Çukurova University in Turkey washed T-shirts, tops, dresses and shorts from Adidas, H&M, Nike, Shein and Zara for the Changing Markets Foundation. Recycled polyester released about 55% more microfibers per gram of fabric than virgin polyester (12,430 against 8,028 on average), and its fibers were about 20% shorter.

Changing Markets is an advocacy group that campaigns against synthetic fashion, and the full report hasn’t been published in a peer-reviewed journal. The fiber-count comparison rests on 23 garments, 14 recycled and 9 virgin, and the report argues that’s enough because each garment stands in for a whole production run of the same fabric. Until a peer-reviewed study repeats it, we treat the 55% figure as an early result.

The report says recycling breaks down polyester’s polymer chains and leaves the fiber more brittle, which would fit the shorter fibers it found. The lab counted and measured the shed fibers, so that explanation is the report’s interpretation.

How does downcycling plastic bottles into clothing work?

A PET bottle can be recycled into a new bottle, and in principle that loop can repeat. Once the bottle is spun into polyester yarn, it usually leaves that loop for good. Activewear often blends the polyester with elastane (spandex) for stretch, and mixed-fiber fabric is very hard to separate and recycle at scale. In its 2017 report A New Textiles Economy, the Ellen MacArthur Foundation estimated that less than 1% of the material used to make clothing is recycled into new clothing.

So a pair of recycled-bottle leggings delays the bottle’s trip to a landfill by the life of the garment, and it sheds fibers the whole time you wear and wash it. Fashion brands now use the same pitch for recycled-bottle vegan leather, which is still a synthetic polymer.

Where do workout clothes release microplastics?

Much of the research on clothing fibers looks at washing machines. In a 2016 Plymouth University study, researchers estimated that an average 6 kg wash of acrylic fabric could release over 700,000 fibers, and polyester shed significantly more than a polyester-cotton blend. Our guide to washing synthetic clothes with less shedding covers the settings and filters that bring that number down.

Wastewater treatment plants catch most of those fibers. A 2020 review of 21 studies found that plants with secondary treatment removed about 88% of microplastics on average, and plants with tertiary treatment about 94%. The fibers they catch mostly end up in sewage sludge, which in many places is spread on farmland, and the rest flow out with the treated water.

In a 2020 study of electric dryers, Kapp and Miller dried polyester fleece blankets at two homes and found the blanket fibers on the snow up to 30 feet from the vents, with most landing within 5 feet. It was a small study, with two dryers and one fabric, but it shows dryer vents release fibers outside the house.

Wearing the clothes releases fibers too. A 2020 study by the University of Plymouth and Italy’s National Research Council measured polyester garments during everyday movement and estimated that the fibers a person sheds into the air each year are of a similar order of magnitude to what their laundry sends to wastewater.

Are natural fibers better for workout clothes?

Microfibers aren’t the only concern with synthetic gym clothes. In 2022 and 2023 the Center for Environmental Health, a California nonprofit, tested sports bras, leggings, shorts and athletic shirts and found some could expose wearers to up to 40 times California’s safe limit for BPA. CEH told ABC7 it had found BPA only in polyester-based clothing that contains spandex.

This was testing by an advocacy group rather than a peer-reviewed study. Most research on BPA exposure has looked at what we eat and drink, and skin absorption has mostly been studied with receipt paper, so how much passes through skin from clothing isn’t well measured. In the meantime, CEH recommends changing out of activewear after a workout to limit the time you spend in it.

Polyester also holds onto body odor. In a 2014 Ghent University study, 26 people wore cotton or synthetic shirts to an hour-long spinning class, and a trained odor panel rated the polyester shirts as smelling stronger and less pleasant. Odor-linked Micrococcus bacteria turned up almost only on the synthetic shirts.

An earlier 2007 study from New Zealand’s University of Otago found the same pattern across nine knit fabrics. Polyester rated high in odor intensity after wear, while cotton and wool rated mid to low. The difference didn’t track bacteria counts, so the fiber itself seems to hold the smell.

Cotton absorbs sweat and dries slowly, and the lined shorts below put merino wool against the skin instead. Neither fiber stretches as much as spandex, and they cost more than most synthetic gym shorts.

Which brands make plastic-free activewear?

Some activewear sold as “natural” still has elastane in the waistband or a polyester liner. We read each brand’s own product pages for fiber content, and these three list only natural fibers for the shell and liner of their training shorts (checked October 2026). Wayve and Ryker don’t say what the elastic and thread are made of, so ask them if that matters to you.

Wayve Wear

Wayve Wear makes the Quad Short with a heavyweight brushed-terry organic cotton shell and a merino wool compression liner, which Wayve says provides the stretch. Its cotton is GOTS-certified and its dyes are OEKO-TEX 100 certified. Wayve’s tee is plain organic cotton, and its product page says it uses no polyester, nylon or synthetic blends.

Ryker

Ryker has the widest range of the three, with tees, tanks, joggers and several shorts. The Apex Short pairs an organic cotton outer short with a merino wool liner, the Apollo is 100% merino, and the Ares is 100% organic cotton knit for some stretch without elastane. Ryker says its fabrics are third-party tested free of BPA, PFAS and phthalates, and its product pages link to the lab report.

Nero

Nero makes the Active Merino Liner Short with an organic cotton shell and a built-in merino wool liner, plus an unlined cotton version, and describes the lined short as 100% free from plastics. Nero’s base-layer pages say its merino comes from RWS-certified farms in New Zealand and Australia, and its homepage explains why it doesn’t use polyester.

Frequently Asked Questions About Plastic Free Activewear

What is plastic free activewear? Athletic clothing made only from natural fibers such as organic cotton, merino wool, hemp or linen, with no polyester, nylon, acrylic or spandex. Check the liner and waistband as well as the main fabric, since a cotton short can still have a synthetic liner.

Does spandex shed microplastics? Spandex, also sold as elastane or Lycra, is a polyurethane-based synthetic fiber, so the fibers it sheds are plastic. Most washing studies focus on polyester and acrylic, so there’s less data on spandex by itself.

How should I wash cotton and merino gym clothes? Cold water and air drying help cotton keep its shape and stop it shrinking. Wash merino on a gentle cycle with a wool-safe detergent unless the label says it’s machine washable, and keep it out of a hot dryer.