pfas in activewear

A family of synthetic chemicals prized for repelling water, oil, and stains — and for not breaking down.

That persistence is the problem: PFAS don’t degrade in the environment or clear quickly from the body, which is why they’re called forever chemicals. In clothing they show up in durable water-repellent (DWR) finishes and stain treatments, and as residues from manufacturing.

Anything sold on being “water-repellent,” “sweat-wicking performance,” or “stain-resistant” is a candidate. Testing by environmental groups has repeatedly found PFAS in activewear and sports apparel — and policy has started to catch up: New York and California both moved to ban intentionally-added PFAS in apparel in 2025. The catch for shoppers is that you can’t read PFAS off a label.

Running is the condition under which textile PFAS are most likely to reach you.

A 2025 study in Science of the Total Environment modelled dermal exposure to PFAS from textiles and found sweat increased absorption by up to 3,252× compared with dry contact — with the highest concentrations in sportswear and water-repellent clothing. Heat opens pores, sweat acts as a solvent, and friction keeps fabric pressed to skin: a run hits all three at once.

PFAS exposure is associated in peer-reviewed research with endocrine disruption and reproductive effects — including a roughly two-fold higher risk of PCOS in some studies. We’re careful not to overstate causation from any single source; the case for avoiding an everyday, sweat-exposed source stands on the weight of evidence, which we lay out — limits included — on our research page.

Skip “water-repellent” and DWR-treated synthetics. Choose untreated natural fibres, and look for OEKO-TEX Standard 100, which tests the finished cloth for PFAS and other harmful substances — the one reliable signal you can actually verify. Our merino yarn is OEKO-TEX tested and PFAS-free. For the wider picture on synthetic gear, see non-toxic running shorts and microplastics in activewear.