CHEMISTRY
What PFAS is, and how it is made
PFAS is shorthand for per- and polyfluoroalkyl substances: a family of more than 10,000 compounds, all built around a chain of carbon atoms saturated with fluorine. The carbon-fluorine bond is one of the strongest in organic chemistry, roughly 480 kilojoules per mole. Very little in nature has the energy to break it. That single fact explains both why PFAS performs and why it is permanent.
The fluorinated chains are manufactured in two main ways. The older route is electrochemical fluorination (the Simons process), which runs an electric current through a hydrocarbon in hydrogen fluoride and swaps hydrogen atoms for fluorine. The other is telomerisation, which builds fluorinated chains up from tetrafluoroethylene building blocks. Both produce the same functional result: a molecule with a water-and-oil-hating fluorinated tail that lowers a surface's energy so far that liquids cannot wet it.
The legacy long-chain versions, PFOA and PFOS (so-called C8 chemistry), were phased out after biomonitoring found them in the blood of essentially the entire tested population. Industry moved to shorter-chain C6 replacements marketed as safer. Shorter chains clear the body faster, but they are just as persistent in the environment, which is why regulators are now moving to restrict the whole class rather than chase one compound at a time.
Where PFAS shows up in clothing
Two main use cases matter for activewear.
Durable water-repellent (DWR) finishes on outdoor gear. Rain shells, hiking jackets, ski pants. The classic DWR is a side-chain fluoropolymer: a comb-like molecule with fluorinated teeth that stand up off the fabric surface and repel rain. This is the single most PFAS-heavy application in the wardrobe. Some brands have switched to PFAS-free DWR. Many have not, because the fluorine-free versions repel oil less well and wear off faster.
Stain and moisture finishes on synthetic athletic fabric. Some polyester and nylon activewear carries a fluorinated finish to resist body oils and stains, or as part of a moisture treatment. It is less universal than the outdoor-gear case, but it is present, and it is invisible on the label.
In both cases the finish is not on the composition tag. Composition tags list fibre percentages, cotton, polyester, elastane, by law in most markets. Surface finishes and coatings are not required to be disclosed. That is the core problem: the thing you would want to avoid is precisely the thing you cannot read.
What the science says about exposure through clothing
Two routes matter: skin contact and laundering.
Sweat behaves as a solvent and can mobilise loosely bound chemistry off a fabric onto skin. A workout amplifies this, because heat opens the skin barrier, blood flow to the skin rises, and tight fabric stays in continuous contact. The 2023 University of Birmingham work, published in Environmental Science and Technology, is one of the clearer demonstrations of the mechanism: it showed that synthetic sweat, and cosmetics such as antiperspirant, increased the amount of hazardous additive chemistry that leached out of microplastic particles and became available for skin uptake. That study looked at flame retardants specifically, but the sweat-as-solvent principle generalises to other loosely bound fabric chemistry.
Washing sends PFAS the other way, into wastewater. Household treatment does not remove it, which is why PFAS contamination now shows up in drinking water near textile and industrial regions.
The documented health concerns, drawn mostly from higher-exposure populations such as factory workers and communities with contaminated water, include endocrine and thyroid disruption, reduced vaccine response, certain cancers, and reduced fertility. The honest caveat: the dose you receive from a single garment is far lower than those exposures, and the science on chronic low-level exposure from consumer products is still building. The case against PFAS in clothing is less "this garment will harm you" and more "this is a permanent chemical with no safe environmental exit, added for convenience, in a category worn against sweaty skin".
How regulation is changing
The EU is moving fastest. A universal PFAS restriction under REACH was jointly proposed in January 2023 by Denmark, Germany, the Netherlands, Norway, and Sweden, covering more than 10,000 substances across hundreds of use sectors including textiles. As of 2026 it has cleared the key scientific hurdle: ECHA's Risk Assessment Committee adopted its opinion in March 2026, the Socio-Economic Analysis Committee ran its consultation into mid-2026, and the final scientific opinion is expected by the end of 2026, after which the Commission drafts the actual restriction. Technical textiles are among the sectors flagged for possible time-limited derogations.
Individual jurisdictions have already moved. France has restricted PFAS in many textiles, and several US states (California, Maine, New York) have PFAS-in-apparel laws phasing in across 2025 to 2027.
What that means in practice: PFAS-free is becoming the compliant default for the EU market, but it is not there yet. Today you cannot assume a synthetic performance garment is PFAS-free unless the brand says so and can back it.
How to spot PFAS-free activewear
The composition tag will not tell you. What works:
An explicit "PFAS-free" claim tied to a certification. OEKO-TEX Standard 100 sets residue limits on the finished product. GOTS prohibits fluorinated chemistry in processing. Bluesign controls chemical inputs at the factory. A "PFAS-free" claim with no named standard behind it is marketing, not verification.
Natural-fibre dominance. Organic cotton, linen, hemp, wool, and lyocell are not made with PFAS in the standard supply chain. Cotton absorbs sweat into the fibre by its own structure, so it never needed a fluorinated moisture finish. A predominantly natural-fibre garment is far less likely to carry PFAS, though it is not impossible, since stain finishes can be added to anything.
Treat unexplained "water-repellent" or "stain-resistant" performance as a flag. Those are exactly the properties fluorinated finishes deliver. If the brand cannot name a PFAS-free DWR, assume fluorine.
Ask the brand. A clear answer is information. So is a vague one.
Where LAINE HILL fits
LAINE HILL is 92% organic cotton with 8% elastane, and we apply no fluorinated finish to it.
Here is the honest version, because we are not GOTS-certified and will not imply an audit we do not hold. PFAS enters clothing as a deliberately added finish. The two reasons a brand adds it, water repellency and a stain or wicking treatment, do not apply to us: cotton pulls sweat into the fibre by its natural structure, and we are not selling rain shells. So we do not specify a PFAS finish anywhere in the garment. What a GOTS certificate would add on top of that is an independent audit confirming no PFAS entered through any auxiliary chemical along the whole chain. We cannot show you that certificate yet. We can tell you plainly that we add no fluorinated chemistry and that our fibre never called for it.
We are not the answer for cold, wet, outdoor cardio, where a treated shell genuinely outperforms cotton. We are the answer for studio, gym, walking, and daily wear, where a polyester-free cotton fabric with no fluorinated finish is the lower-exposure choice on the chemistry that actually touches your skin.
If you have been training in synthetic moisture-wicking gear and want to step back from this category of chemistry, the most direct test is the one we keep suggesting: wear a polyester-free cotton piece for two weeks and notice the difference against your skin.
Common questions
What does PFAS stand for?
PFAS stands for per- and polyfluoroalkyl substances, a family of more than 10,000 synthetic chemicals (some inventories put it above 14,000) first developed in the 1940s. They are called "forever chemicals" because the carbon-fluorine bond is one of the strongest in organic chemistry. PFAS do not break down meaningfully in the environment, in water, or in the human body.
Is PFAS used in regular activewear?
Yes, in two main ways. As a durable water-repellent (DWR) finish on technical outdoor gear, and as part of some moisture and stain finishes on synthetic athletic fabric. A January 2022 Mamavation and Environmental Health News investigation screened 32 pairs of workout leggings and yoga pants for organic fluorine (a marker used to flag likely PFAS treatment) and found detectable organic fluorine in about a quarter of the samples, in the 10 to 284 ppm range. Organic fluorine is an indicator, not a direct count of a specific PFAS, but it is enough to say you cannot assume a synthetic garment is PFAS-free without evidence.
How can I tell if my leggings have PFAS?
You usually cannot tell from the label alone. PFAS is an applied finish, not a fibre, so it does not appear on the composition tag. Look for explicit "PFAS free" claims backed by OEKO-TEX Standard 100, GOTS, or Bluesign. Be sceptical of garments sold on "water-repellent" or "stain-resistant" performance without a chemical disclosure. When in doubt, contact the brand.
Why do brands use PFAS in clothing?
Because nothing else repels both water and oil as cheaply and reliably. The carbon-fluorine chain lowers surface energy so far that liquids bead and roll off. The industry standardised on it decades ago, before the health and environmental data caught up. PFAS-free DWR alternatives exist now (silicone and paraffin-based), but they resist oil less well and need reproofing more often, which is why plenty of performance brands still use fluorinated chemistry.
