Elastane

Elastane is a cured elastomer worn against skin, and there is no established leaching or dermal-toxicity issue attributed to the fibre itself. Where stretch garments cause skin trouble the usual suspects are dyes, residual processing chemistry and antimicrobial finishes rather than the polyurethane. We count it as plastic for what it does to a garment's material identity, lifespan and end of life, not because of a contact-path risk. Like every synthetic it sheds microfibres in the wash, but at 2-5% of a fabric the bulk fibre - polyester or nylon - dominates that release.

Elastane is the most heat-sensitive component of any fabric it is blended into, more so than the polyester or nylon around it. In practice the hot wash, the tumble dryer and the iron are what destroy stretch, and they destroy it well before they damage the rest of the garment. Wash cool and line dry if you want the fit to survive.

Read the fibre-content percentages: elastane, spandex or Lycra listed at anything from 1% to 20%. The tell in a garment claiming to be all-natural is behaviour - fabric that stretches in every direction and snaps back sharply almost always contains elastane, where a mechanical-stretch knit stretches but recovers slowly and stays baggy. Waistbands, cuffs and lace trim are the usual hiding places, and trims are not always broken out on the content label. Ask a brand two questions: is the waistband elastic covered natural rubber or elastane, and does any trim contain elastane that the main fibre-content line does not cover.

Elastane is the component that dies first. In a chlorinated-pool ageing test on swimwear blends, breaking force fell 12.4% after 200 hours of exposure and 65.7% after 300 hours - the garment goes slack and sheer long before it wears through. Chlorine, sunscreen, body oils, heat and hard stretching while wet all accelerate it. Rinse swimwear in cold fresh water straight after use, never wring or tumble dry it, and expect a couple of seasons rather than years.

Elastane does not biodegrade, and its larger effect is on everything it is blended with: even a few percent prevents fibre-to-fibre recycling, fouling mechanical shredding and contaminating chemical recycling streams. Solvent routes that dissolve elastane back out of a blend exist in the laboratory and are not commercially available. A cotton garment with 5% elastane ends up in the same bin as a polyester one. The mainstream plastic-free option for stretch is covered natural rubber elastic, or a garment cut to fit without a stretch fibre at all.