What underwear has no microplastics?

Where the fibres actually come from

A washing machine is an abrasion machine. Garments tumble against each other and against the drum for thirty minutes to an hour, and the mechanical action breaks loose fibre ends off the surface of the fabric. That is what lint is. It happens to every textile ever made.

What changes between fabrics is the material of the fragment. Polyester, nylon, acrylic, polypropylene, and elastane are all extruded plastics. Polyester is polyethylene terephthalate, the same polymer family as a drink bottle, drawn into a filament instead of blown into a shape. When abrasion breaks a fibre end off a polyester knit, the fragment is a piece of plastic a few micrometres across. That is a microplastic fibre, and it leaves your machine in the wastewater.

Cotton, wool, hemp, and linen are not plastics. Cotton is close to pure cellulose. Wool is a protein. The fragments they shed are the same, and they biodegrade on the timescale that plant and animal matter biodegrades on.

What the laundry studies measured

The figure most often quoted comes from washing-machine trials that captured and counted the fibres in the effluent from a single domestic wash. In the most cited of these, a 6 kg load was washed and the released fibres counted by fabric type.

Two things in that table are worth reading carefully rather than skimming.

The first is the size of the numbers. Hundreds of thousands of fibres from one load is not a rounding error, and a drawer of synthetic underwear goes through the machine every week for years.

The second is the blend row, which is lower than either pure synthetic. The authors of that work noted it and did not overclaim about why. A plausible reading is that the cotton in the yarn changes the surface structure and holds the polyester filaments differently. It is a real result and it cuts against a simple story, so it belongs on the page. It does not make a blend plastic-free. The blend still released more than a hundred thousand plastic fragments per wash, and the cotton fraction is doing nothing about them.

The rule this gives you

Shedding of plastic scales with the amount of plastic in the fabric. There is no threshold below which a synthetic percentage stops shedding, and there is no finish that seals fibre ends in permanently. So the only composition that sheds no synthetic fibre is one with no synthetic fibre in it.

That turns a vague shopping question into a label-reading exercise. On the composition line, these are plastics:

• Polyester, including recycled polyester and rPET. Recycled polyester is still polyester. The recycling changes where the polymer came from, not what it is.
• Nylon, and polyamide, which is the same thing under its other name.
• Elastane, spandex, and Lycra. Three names for a polyurethane-based elastomer.
• Acrylic, modacrylic, polypropylene, olefin.

These are not plastics, and they are frequently confused for them:

• Cotton, organic cotton, wool, merino, hemp, linen, silk. Natural fibres.
• Modal, viscose, rayon, lyocell, Tencel, and most fabric sold as bamboo. These are manufactured but they are regenerated cellulose, not polymer. They shed cellulose. There are real environmental questions about the solvents and pulp used to make them; microplastic shedding is not one of them.

Limits of this page

What we do not know, what the numbers do not cover, and what a garment change does not fix.

• We have not tested our own garment for shedding. The claim on this page is a materials claim: the panels contain no synthetic fibre, so there is no synthetic fibre to shed. It is not a fibre count from a lab that washed a Goshen brief and counted the effluent. Those are different claims and only one of them is ours.
• Underwear is one exposure route out of many. Most measured human microplastic exposure is attributed to dust, water, food packaging, and the air indoors. Changing one garment category changes one input. Anyone telling you a pair of underwear meaningfully lowers your total plastic exposure is selling you something.
• We make no health claim. Research on microplastics in human tissue is active and early. There is no established causal finding that wearing synthetic underwear produces a specific health, hormonal, or fertility outcome, and we do not claim one. What we claim is what the fabric is.
• Cotton sheds too. Natural microfibres are found in the environment in large quantities and their effects are still being studied. Cellulose is not plastic, which is the distinction this page rests on, but it is not the same as shedding nothing.
• A laundry filter is the cheaper intervention. If your goal is less plastic leaving your house, a filter or a fibre-catching wash bag acts on every synthetic garment you already own, for far less than replacing a drawer. Do that first. It works whether or not you ever buy from us.