Every wash cycle with synthetic fabric sheds fibers too small to see. The question researchers have actually measured isn’t whether this happens — it clearly does — but how much, which fabrics are worst, and what actually reduces it. Here’s what the studies say.

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The numbers, roughly

Published studies on domestic laundry give a wide range, largely because fabric type, wash conditions, and measurement methods differ between experiments. One widely cited estimate puts a single wash load at over 700,000 fibers released. Measured by weight, microfiber loss has been recorded anywhere from roughly 10 mg to over 1,000 mg per kilogram of washed fabric, depending heavily on what’s actually in the load.

Fabric type matters more than “synthetic vs. natural”

The instinctive assumption is that synthetic fabric sheds and natural fabric doesn’t — the research doesn’t fully support that. One comparison found that mechanically processed polyester, especially fleece and jersey knits, released about six times more microfiber than woven nylon with filament yarns. And in the same body of research, cotton and wool textiles also shed substantial amounts of fiber — in some measurements, comparable to synthetic knits. The real variable isn’t just fiber type; it’s how the fabric is constructed. Loosely knit, mechanically processed fabric sheds more than tightly woven fabric, regardless of what it’s made from.

Does recycled polyester shed differently than virgin polyester?

Not meaningfully. Recycled polyester and virgin polyester are chemically the same material once spun into fiber, so they shed at similar rates in the wash. Choosing recycled polyester over virgin reduces the demand for new petroleum-based material and diverts existing plastic waste from landfill — genuine benefits — but it doesn’t solve the microfiber shedding question on its own. That’s a separate problem tied to fabric construction and washing habits, not to whether the polyester started as a bottle or as crude oil.

What actually reduces shedding

• Wash in a microfiber-catching bag or filter. These trap fibers before they reach the wastewater stream, and they’re the single most direct intervention available to a household.
• Wash cold and on a gentler cycle. Higher agitation and heat increase fiber breakage and release.
• Wash less often. Every cycle sheds fiber, so fewer washes over a garment’s lifetime means less total shedding, plus less wear on the fabric itself.
• Choose tightly woven or denser knit fabric where possible. Construction affects shedding more than the raw fiber type does.
• Buy fewer, longer-lasting pieces. A garment that lasts five years instead of one sheds fiber over a much longer useful life, for the same manufacturing footprint.

Where Njálla fits in

Our leggings, tops, and sports bras are made from roughly 73% recycled polyester and spandex, woven densely rather than as a loose knit, which construction research links to lower shedding than fleece-style synthetics. We can’t claim zero microfiber release — no synthetic fabric can honestly say that — but we’d rather point you toward a wash bag and a cold cycle than pretend the issue doesn’t exist. You can read more about how our recycled fiber is made in our production process guide.

Frequently Asked Questions

Does a washing machine filter actually stop microfiber pollution?

A wash bag or in-line filter traps a meaningful share of fibers before they reach wastewater, though no household filter captures 100%. It’s a genuine reduction, not a complete fix.

Do natural fibers like cotton avoid the microplastic problem?

Cotton and wool don’t shed plastic microfibers, but research shows they still shed substantial amounts of fiber during washing — in some studies, comparable to synthetic knits. The environmental persistence differs (natural fiber biodegrades, plastic fiber doesn’t), but the physical shedding still happens.

Is recycled polyester better than virgin polyester for microfiber shedding?

Not for shedding specifically — the two shed at similar rates once spun into fabric. Recycled polyester’s real advantage is diverting existing plastic waste and reducing demand for new petroleum-based fiber, not reduced shedding in the wash.

Explore the Njálla Collection

Shop our sustainable yoga leggings and yoga tops - recycled fabric, handmade Nordic nature art, ethically made. Not sure where to start? Read our complete buying guide.