Your favorite moisture-wicking leggings and performance sports bras may be delivering more than just comfort and stretch; they're also delivering a cocktail of synthetic chemicals linked to hormonal disruption, cancer, and thyroid dysfunction. A 2022 investigation by Environmental Health News and Mamavation tested 32 pairs of workout leggings and yoga pants and found polyfluoroalkyl substances (PFAS) markers in 25% of them, including products from major brands like Lululemon, Athleta, and Old Navy . For people who wear activewear regularly, especially those over 50, the cumulative health impact of these chemicals deserves serious attention.

What Chemicals Are Hiding in Your Activewear?

The performance features you pay premium prices for, such as moisture-wicking, stain resistance, quick-dry properties, and anti-odor finishes, are largely delivered not through clever fabric engineering but through chemical treatments applied to petroleum-based synthetic materials . The primary offenders fall into several categories that have been linked to serious health concerns.

• PFAS (Forever Chemicals): Polyfluoroalkyl substances are a family of over 12,000 synthetic compounds built around one of the strongest chemical bonds in nature, carbon and fluorine. This bond makes them extraordinarily useful for industry because nothing sticks to them, water rolls off them, and stains don't penetrate them. However, they don't break down in the environment, in your washing machine, or easily in your body .
• BPA and Phthalates: Typically associated with plastics, both compounds also appear in synthetic textiles. BPA is an endocrine disruptor that mimics estrogen, while phthalates interfere with testosterone signaling. The Center for Environmental Health found certain sports bras and athletic shirts testing 22 times above the safe limit for BPA .
• Formaldehyde and Azo Dyes: Formaldehyde, a known human carcinogen, is used in poly-cotton blends and finishes to prevent wrinkling and add durability. Azo dyes, used to create the bright colors dominating activewear, can break down on skin into aromatic amines, compounds with their own carcinogenic profile .

These chemicals are especially prevalent in activewear because companies have historically prioritized performance over safety, relying on chemical finishes to deliver the quick-drying, odor-resistant, and easy-care garments consumers expect . The problem is compounded by the fact that synthetic fabrics like nylon and spandex, which are derived from petrochemicals and engineered for high-performance movement, are often finished with chemical treatments that can include PFAS .

Why Exercise Makes Chemical Exposure Worse?

Here's the cruel irony: the act of working out, the very thing that makes you healthy, is what maximizes chemical exposure from the clothes you wear to do it. As body temperature rises during exercise, pores dilate and skin permeability increases. Research suggests that the dermal absorption rate of certain chemicals can increase by as much as 50% during exercise compared to rest . Sweat itself acts as a chemical solvent, and its oily composition draws residues out of synthetic fibers and deposits them directly against open pores. Friction and compression from close-fitting garments create micro-abrasions that further compromise the skin barrier .

This multi-vector exposure is particularly concerning because workout clothing sits tight against your largest organ, your skin, with pores wide open as you sweat. During exercise, the heat and friction from movement can amplify chemical absorption, making it easier for PFAS to penetrate the skin barrier . This is especially problematic for people who wear activewear regularly or for long durations, such as athletes, fitness enthusiasts, or healthcare workers .

Why This Matters More as You Age?

For someone in their 30s with robust hormonal function and years of physiological buffer, chronic low-level exposure to endocrine-disrupting chemicals is a slow-burn concern. For people in midlife and beyond, that buffer is thinner, and the stakes are higher . PFAS, phthalates, and BPA all interfere with the hypothalamic-pituitary-gonadal axis, the hormonal signaling network that regulates testosterone and estrogen .

Men in their 50s, 60s, and beyond are already navigating the natural decline in testosterone that begins in the late 30s and accelerates through the 50s and 60s. Women are managing the hormonal shifts of perimenopause and beyond. The last thing either group needs is a daily dose of compounds that work against whatever hormonal equilibrium they've built . Additionally, PFAS bioaccumulate over time, meaning the person who has been wearing performance activewear daily for 20 years carries a higher body burden than someone who started recently. Cumulative exposure matters, and this demographic has more of it .

The health consequences linked to these chemicals are significant. Epidemiological studies reveal associations between PFAS and liver and kidney disease, fertility issues, thyroid disease, and cancer . PFAS have been specifically linked to thyroid dysfunction, liver damage, elevated cholesterol, kidney and testicular cancer, altered immune function, and reproductive toxicity .

How to Reduce Your Exposure to Chemical-Laden Activewear

• Check for Third-Party Certifications: Look for activewear certified by OEKO-TEX Standard 100 or bluesign, which verify that synthetic fabrics have not been impacted by PFAS and other harmful finishes. Many synthetic fabrics available today are free from harmful chemical treatments and certified safe by these standards .
• Prioritize Organic Natural Fibers: Choose activewear made from organic cotton, organic thermal, organic fleece, organic terry, organic stretch, organic knit, or linen rather than petroleum-based synthetics treated with chemical finishes. These materials can deliver breathability and comfort without relying on PFAS for moisture-wicking properties .
• Ask Brands for Transparency: Request that companies disclose their chemical finishes and manufacturing processes. Awareness is key; by checking labels and asking brands for transparency, you can make safer, more informed choices that benefit your health in the long run .
• Understand That Washing Is Harm Reduction, Not a Solution: While washing does remove surface residues and manufacturing contaminants, the performance finishes that are the real concern are chemically bonded to the fiber structure during manufacturing and engineered to survive dozens of industrial-grade washes. A home laundry cycle barely makes a dent on the embedded chemistry .

A 2022 peer-reviewed study published in Environmental Science examined what happens to PFAS-treated polyester and nylon through cycles of aging, washing, and tumble drying. The results were counterintuitive: while some PFAS compounds were reduced by washing, aging combined with washing actually increased the extractable concentration of certain volatile PFAS and introduced compounds that hadn't been detected in the original material .

The good news is that awareness is growing. More mainstream brands, such as H&M, Zara, and Levi Strauss & Co, are now producing affordable and stylish PFAS-free collections . However, the key is to read labels carefully, ask brands directly about their chemical finishes, and prioritize products made with organic materials and certified by third-party standards. Your endocrine system, and your long-term health, will thank you.