Polyester, a petroleum-based plastic fiber, is one of the world’s most widely used synthetic fabrics, accounting for over half of all global fiber production. It is pervasive in clothing, bedding, and home furnishings. Consumers are increasingly concerned about whether polyester functions as an endocrine disruptor (EDC). This concern focuses on chemical compounds that may migrate from the fabric and interfere with the body’s delicate hormonal regulatory systems. Understanding this risk requires distinguishing between the base polymer and the processing chemicals added during manufacturing.
What Defines an Endocrine Disruptor
Endocrine-disrupting chemicals (EDCs) are exogenous substances that interfere with the synthesis, action, or elimination of natural hormones. Hormones are the body’s chemical messengers, regulating nearly every physiological process, including metabolism, growth, and reproduction. EDCs derail these functions primarily through molecular mimicry, where the EDC binds to a hormone receptor, either activating it or blocking the natural hormone. Other EDCs may alter the rate at which natural hormones are metabolized or eliminated, causing chemical signaling imbalance. Exposure occurs through ingestion, inhalation, and dermal absorption, which is particularly relevant for textiles. The timing of exposure is relevant, as life stages like fetal development are periods of heightened sensitivity.
Is the Polyester Fiber Itself the Problem
Polyester is primarily composed of polyethylene terephthalate (PET), the same polymer used to make plastic bottles. In its finished textile form, the PET polymer is generally considered biologically inert due to its high molecular weight and stable structure. This stability prevents the large polymer chains from easily breaking down into smaller, biologically active components at body temperature or through normal wear. The core PET fiber resists leaching through direct contact because it is tightly bound and chemically unreactive with skin or sweat. Therefore, the finished polyester fiber is not typically classified as an EDC on its own; the concern lies with the chemical residues and additives embedded during processing.
Chemical Additives Used in Textile Manufacturing
The true source of endocrine disruption risk in synthetic fabrics like polyester is the array of chemicals used to dye, finish, and enhance the textile’s performance. These additives are incorporated to achieve properties like color, softness, wrinkle-resistance, and moisture-wicking capability. Many of these processing chemicals are known or suspected EDCs, and they are not chemically bonded to the fiber, allowing them to migrate out of the fabric.
Common EDC Additives
Phthalates are common culprits, used as plasticizers to make synthetic materials softer and more flexible, particularly in prints and coatings. They are well-documented EDCs linked to reproductive issues and metabolic disorders. Bisphenol A (BPA), an estrogen-mimicking chemical, is sometimes found in recycled polyester, where it can leach out, especially when the fabric is warm or damp from sweat. Per- and Polyfluoroalkyl Substances (PFAS) are often applied to activewear for water and stain resistance. These “forever chemicals” are EDCs associated with thyroid dysfunction and immune system problems. Formaldehyde is frequently used for wrinkle-resistant finishes and is a known irritant and potential EDC absorbed through the skin. Azo dyes can break down upon contact with skin and sweat to release aromatic amines, some of which are carcinogenic and suspected EDCs. Antimony trioxide, a heavy metal compound used as a catalyst during PET synthesis, can also remain as a residue and leach from the finished garment. These residual chemicals are most easily absorbed through the skin when the fabric is worn tightly or during physical activity that generates heat and sweat.
Reducing Exposure and Safer Fabric Choices
Consumers can take practical steps to reduce potential exposure to EDCs in polyester finishes. Since many problematic chemicals are residual, washing new garments before wearing them can help remove some surface residues. However, repeat washing may not remove all embedded chemicals like PFAS. Avoid clothing advertised with “performance” or “easy-care” features, as these labels often indicate chemical finishes. Stain-resistant, water-repellent, anti-microbial, and wrinkle-free fabrics are more likely to contain EDCs like PFAS and formaldehyde. Choosing textiles certified by third-party standards, such as OEKO-TEX Standard 100, provides assurance that the product has been tested for hundreds of harmful substances. For high-contact garments, selecting alternative materials can mitigate risk. Safer alternatives include natural fibers like organic cotton, linen, hemp, and newer cellulosic fibers such as Tencel or Lyocell. These materials require fewer chemical treatments during processing, but ensure they are not treated with wrinkle-free or stain-resistant finishes.