Spandex

Spandex is a synthetic polyurethane-based elastic fiber spun from segmented polymer chains, built using reactive diisocyanates like TDI and MDI. The finished fiber is a stable polymer, but those diisocyanates are genuine skin and respiratory sensitizers in their unreacted state, and trace processing residues, dye chemicals, and softeners can remain in the yarn.

You almost never wear spandex alone; it is blended into leggings, sports bras, and shapewear that sit against your most absorbent skin while you sweat. That matters because spandex blends are where independent testing has repeatedly flagged bisphenol A (BPA), a known endocrine disruptor, with one watchdog study finding BPA in polyester-spandex athletic wear at up to 40 times California's safe limit. The same stretch garments are also where durable water-repellent PFAS finishes and residual manufacturing surfactants like nonylphenol ethoxylates show up, and the tight, occlusive fit traps heat and moisture against the skin, which increases both irritation and chemical migration. Spandex is not the worst offender on its own, but it is the fiber that keeps high-hazard chemistry pressed to your body.

Choose OEKO-TEX STANDARD 100 certified stretch wear, which bans intentional PFAS and limits BPA and phthalates, and keep spandex to the smallest practical percentage by favoring natural-fiber pieces with only a few percent stretch rather than full synthetic blends.

Spandex is fossil-fuel derived, does not biodegrade, and makes blended garments nearly impossible to recycle.