Is polyester actually worse for the planet than cotton?

Short answerSometimes. But the bigger lever isn't which fibre you buy. It's how many times you wear it.

Synthetic fibres do have a cost. Polyester and nylon take energy to make and usually start with fossil-fuel feedstocks. That's true and we're not going to dress it up.

Natural fibres have costs too. Cotton can take substantial land, water, fertiliser and pesticides. Wool carries land use and livestock impacts. Even regenerated fibres like modal involve energy and chemically intensive processing. Then dyeing, finishing, sewing and shipping add impact on top, whatever you started with.

There is no impact-free fabric.

Most fibre comparisons measure the wrong moment

They weigh a kilogram of cotton against a kilogram of polyester at the factory gate. That tells you only part of the story bout the article in your drawer, because it stops before the part that matters most: how long you actually keep wearing it.

When researchers looked at that instead, the picture changed.

None of this makes fibre choice irrelevant. It means the honest version of the question isn't "is polyester worse than cotton." It's worse by which measure, for what use, and over how many wears?

There isn't one universal answer. Anyone giving you one is simplifying.

So should I just buy cotton leggings?

Short answerFor a t-shirt, sure. For leggings, no, and not for the reason you'd expect.

Cotton has no real recovery. Stretch it at the knee and it stays stretched. It soaks up sweat instead of moving it, so it turns heavy, cold and prone to chafing. Under tension it goes sheer.

Then there's the part that never makes the marketing. You sweat in these clothes and you wash them constantly. A cotton legging worn hard and washed hot a few times a week comes undone. It bags, it thins, it loses shape. Before you know it you're needing to replace it.

Which lands you right back at the finding above. If the single biggest thing you can do is wear a garment more times, then a legging that fails in four months is the expensive option, for you and for everything else.

A lower-impact fabric isn't the lower-impact choice if the garment doesn't last.

That's why technical synthetics took over this category in the first place. Not as a shortcut. Because the job genuinely needs them.

What about microplastics? That's the bit that worries me.

Short answerYou're right to worry. This is the one we won't try to explain away.

Synthetic fabrics shed microscopic fibres while they're made, worn and washed. Those fibres reach wastewater, soil and water, and conventional synthetics can persist there for a very long time. That's a real environmental problem.

Not everything sheds equally. Fibre, yarn and knit construction, brushing, garment age, wash conditions and build quality all change how much comes off. A tightly knit performance fabric behaves very differently from a loose polyester fleece. But that doesn't make the problem go away. A conventional fibre that escapes is still a persistent one.

What we did about it

Our performance fabrics use CiCLO. It's built into the polyester and nylon while the fibre is being made, and it creates biodegradable pathways inside the fibre itself. Where there's biological activity, naturally occurring microorganisms can break those fibres down far more readily than conventional ones.

Third-party laboratories have measured substantially greater biodegradation of CiCLO-treated polyester and nylon than conventional equivalents, across several biologically active conditions including wastewater sludge, landfill, soil and marine environments.

Better is not the same as perfect.

And the chemicals? PFAS, BPA, all of that?

Short answerAlso real. But it's mostly not coming from the fibre, and switching to cotton doesn't get you out of it.

Here's the thing almost nobody explains. Making fabric isn't one step, it's a long chain of them. Cloth gets dyed, printed, softened, coated, bonded, washed and finished, using water repellents, stain repellents, wrinkle and odour treatments, processing aids, adhesives and inks.

That's where the substances people worry about come from. PFAS were used for water and stain resistance. Bisphenols like BPA and BPS have been found in clothing. Formaldehyde, phthalates and heavy metals can enter at various stages.

Which is why the natural swap doesn't do what people think. Organic cotton is still dyed, printed and finished. Modal is still dyed and finished. A natural-fibre garment can carry chemistry introduced years after the plant was grown.

Fibre type isn't irrelevant. Some studies have found higher concentrations of certain substances, including bisphenols, in polyester-rich garments than cotton ones. Material choice can matter.

But natural isn't the same as chemical-free, and synthetic isn't automatically toxic.

The useful question isn't only what is this made of? It's what happened to it after that?

Fine. So how do I know you're not just saying all this?

Short answerYou shouldn't take our word for it. Read the report.

We use different fibres for different jobs. Performance products use technical synthetic blends because they deliver stretch, recovery, opacity, moisture management and durability that natural fibres can't match. Where those things matter less, we use fibres like cotton and modal.

We don't have a house fibre. We have a house standard.

That standard starts with chemistry. We use bluesign approved dyes, which means the dyes themselves are screened against a restricted-substance list before they ever reach the fabric. We control what's used through manufacturing. And we test the finished garment, not the fabric roll, because that's the only way to catch anything that arrived at steps five, six and seven.

And we publish the reports, so you can read what was actually tested instead of trusting our summary of it.

Isn't this just greenwashing with extra steps?

Short answerSomeone asked us exactly that recently. Here's the test we'd want you to apply to us.

Greenwashing isn't making an environmental claim. It's making the claim sound broader or more certain than the evidence behind it.

It's "non-toxic" with no definition. It's "microplastic-free" on a garment that still sheds. It's "sustainable" with no mention of the trade-offs involved in making the thing.

So we try to do the opposite

Tell you our performance products contain advanced synthetic fibres instead of hiding behind a proprietary fabric name. Admit synthetics have a footprint. Say plainly that microfibre pollution is real. Explain why we use CiCLO and be just as clear that it doesn't stop shedding.

Test for chemicals of concern, while admitting no test covers every substance. Publish the actual laboratory reports rather than putting a "tested or clean" badge on a page. Say which certifications we rely on, what they cover and what they don't.

And when the science changes, change the claims with it.

OK. So what should I actually do?

Short answerStop shopping by fibre name. Ask six questions instead, of us and of everyone else.

We understand why people want a simple rule. Natural sounds better than synthetic. A plant is easier to feel good about than a polymer. But a single word on a care label is standing in for a system with a dozen steps in it, and that's where the false certainty comes from.

We're not asking you to ignore the trade-offs. We're asking you to look closer.

• 01What is it made from, and does that suit what you'll use it for?
• 02What happened to the fabric after the fibre stage?
• 03Was the finished garment tested, or just the fibre certified?
• 04Can you actually read the report, or only see a badge?
• 05How many times will you realistically wear it before it gives up?
• 06What does the brand claim, and what can it substantiate?

Run those six on us. Run them on the brand you were going to buy instead. That comparison is worth more than any badge either of us could put on a page.

We don't think the future of this category is pretending synthetics have no problems. It's building better ones, managing the chemistry carefully, making clothes that last, improving as the science moves, and showing you the evidence.

Don't take our word for it. Look closer.