The label on your leggings tells you the fiber composition. It does not tell you what was applied to those fibers between the factory and your body. For most conventional activewear, that gap in information is where the relevant concerns live.
If you are looking for non toxic activewear collection options that meet a verifiable standard, understanding how to evaluate your current wardrobe is the starting point. Here is how to assess whether your activewear is toxic, using the information that is available and knowing where the limits of that information are.
Start with the fiber composition label
The Textile Fiber Products Identification Act requires all garments sold in the United States to list fiber composition by percentage. This is the most reliable starting point for any assessment.
Predominantly synthetic compositions, primarily nylon, polyester, and spandex above 20%, are a signal to look further. Synthetic fibers derived from petroleum are not inherently toxic in finished form, but they are more likely to carry chemical finishing treatments applied during manufacturing, and they shed microplastic fibers during washing. Research by Browne et al. published in Environmental Science and Technology (2011) documented microplastic fiber accumulation from synthetic garments in marine environments globally.
Natural and naturally derived fibers, TENCEL Lyocell, organic cotton, merino wool, are generally lower-risk at the fiber level, though chemical treatments applied during manufacturing can still be a concern regardless of the base fiber.
Check for certifications on the hangtag or product page
OEKO-TEX Standard 100 certification is the most practically useful signal for assessing whether a finished garment has cleared a non-toxic threshold. A garment carrying this certification has been tested by an accredited independent laboratory for more than 100 harmful substances including formaldehyde, heavy metals, certain azo dyes, pesticide residues, and PFAS compounds. For a complete breakdown of what OEKO-TEX actually tests for, what the different certification levels mean, and how to verify a certification is genuine, the page on OEKO-TEX and activewear covers it directly.
If a garment does not carry OEKO-TEX Standard 100 or an equivalent independent certification, you have less information about what chemical treatments it may contain. The absence of certification is not proof of toxicity, but it is an absence of independent verification.
Warning signs in marketing language
Certain marketing phrases are signals worth scrutinising rather than accepting at face value.
Performance that sounds too good: moisture-wicking fabric that also claims to be 100% natural and chemical-free is worth examining. Many performance properties in synthetic fabrics are achieved through chemical finishing treatments. A fabric that claims all the benefits of synthetic performance without any synthetic inputs should be able to explain the mechanism.
Antimicrobial claims without specifics: a garment marketed as antimicrobial or odor-resistant without naming the mechanism is likely using a chemical antimicrobial treatment. Ask what compound provides the antimicrobial property. Silver-based treatments and certain triclosan derivatives are common and carry documented concerns. A fabric that achieves odor resistance through moisture management rather than chemical treatment, as TENCEL Lyocell does, can answer this question with a fiber mechanism rather than a chemical compound name.
Sustainability claims without certifications: a brand that describes its products as sustainable, clean, or non-toxic without independent certification is making an unverified claim. Certification bodies like OEKO-TEX, GOTS, and Bluesign exist specifically to provide third-party verification of these claims.
The chemical treatments most worth asking about
PFAS compounds are the highest-priority concern for activewear specifically. Used for water repellency and stain resistance, they have been documented in activewear products from multiple major brands by the nonprofit MADE SAFE (2022). The US EPA classifies certain PFAS as probable human carcinogens. The full picture on PFAS in activewear, including how they enter garments, the health research, and how to find genuinely PFAS-free options, is covered in the dedicated guide to PFAS in activewear. A brand that can explicitly confirm it does not use PFAS treatments, with supporting documentation, is providing meaningful information.
Formaldehyde-based wrinkle resistance has been documented in some textile products. The International Agency for Research on Cancer classifies formaldehyde as a Group 1 carcinogen in occupational contexts. OEKO-TEX Standard 100 testing covers formaldehyde limits, making that certification a useful signal.
Antimicrobial chemical finishes applied to synthetic activewear can include compounds with endocrine-disrupting potential. The US FDA banned triclosan from consumer antiseptic wash products in 2016, though its use in textiles remains less regulated. For the full list of toxic chemicals found in workout clothes, that post covers each compound in detail. For a broader look at which fabrics to avoid entirely, that is covered separately.
What non-toxic actually looks like in practice
A non-toxic activewear garment has a fiber composition that is primarily natural or naturally derived, carries independent certification covering the finished fabric for harmful substances, and can answer specific questions about chemical treatments with documented responses rather than general sustainability claims.
Bellissima's Sempre Leggings and bras use 92% TENCEL Lyocell and 8% spandex. The TENCEL Lyocell is produced by Lenzing AG through a closed-loop process that recovers more than 99% of its production solvent, according to Lenzing's published data. Moisture management and breathability come from fiber structure rather than chemical treatment. There are no PFAS treatments, antimicrobial chemical finishes, or formaldehyde-based treatments in the fabric. Those are specific answers to specific questions.
The practical approach
Check the fiber label first. Look for independent certification on the product. Ask the brand directly about PFAS, antimicrobial treatments, and formaldehyde-based finishes. Evaluate the answers against whether they are specific and documented or general and unverified. For a structured version of this process, reading activewear fabric labels correctly is where to start, and the non-toxic activewear buying guide covers the full evaluation framework in depth.
Most activewear will not clear all three steps with satisfying answers. That is useful information about the market, and it is why the question is worth asking.
Sources
Browne, M.A., et al. (2011). Accumulation of microplastic on shorelines worldwide: Sources and sinks. Environmental Science and Technology, 45(21).
MADE SAFE. (2022). PFAS in activewear: Brand scorecard. MADE SAFE Report.
US Environmental Protection Agency. (2023). PFAS explained. EPA Technical Overview.
International Agency for Research on Cancer. (2006). Formaldehyde, 2-butoxyethanol and 1-tert-butoxypropan-2-ol. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 88.
US Food and Drug Administration. (2016). Safety and effectiveness of consumer antiseptics. FDA Final Rule.
OEKO-TEX Association. (2023). OEKO-TEX Standard 100 testing criteria. OEKO-TEX Technical Bulletin.
Lenzing AG. (2023). TENCEL Lyocell fiber sustainability and production data. Lenzing Sustainability Report.
