Polyester is a synthetic polymer, specifically Polyethylene Terephthalate (PET), that forms the basis of many modern fabrics. Its widespread use in clothing, particularly activewear worn close to the skin, has led to public concern about potential chemical exposure. These concerns focus on whether manufactured fibers can release chemicals that migrate onto the skin or into the body. This article examines the reality of chemical leaching from polyester, differentiating between the base material’s composition and the finishing treatments applied during textile production.
Chemical Structure of Polyester Fiber
Polyester is derived from petrochemical raw materials, primarily ethylene glycol and terephthalic acid, which undergo polymerization to form PET. The long chains of PET molecules create a stable polymer structure, giving the fiber durability and resistance to most chemicals. The polymer itself is biologically inert, meaning it does not readily react with the body or environment under normal conditions.
Chemical concern stems primarily from residual components left over from manufacturing, not the polymer chains themselves. Most global PET production relies on antimony trioxide as the polymerization catalyst. This heavy metal, antimony, remains embedded in the final polymer structure, though alternatives like titanium-based catalysts are sometimes used. Residual monomers or acetaldehyde, a volatile organic compound, can also be present in the finished fiber.
Chemicals Added During Processing
The base PET polymer is stable, but the most significant leaching risk comes from chemical additives applied after the fiber is spun into fabric. Textile finishing processes utilize a wide array of chemicals to impart properties such as color, stain resistance, and wrinkle resistance. These surface treatments are not chemically bound to the polyester fibers, making them prone to migration.
Dyes and Colorants
Disperse dyes are used to color polyester and are a primary source of potential skin irritants. Certain azo dyes have been banned in many regions because they can break down and release carcinogenic aromatic amines upon contact with the skin or sweat.
Performance Finishes
Per- and Polyfluoroalkyl Substances (PFAS) are often applied to create water-repellent or stain-resistant finishes. These persistent chemicals have been linked to various health risks, including hormone disruption. Formaldehyde is also used to enhance wrinkle resistance and can cause skin and respiratory irritation.
Plasticizers and Antimicrobials
Phthalates may be used as plasticizers in printed logos or elastic components and are known endocrine disruptors. Antimicrobial treatments are frequently applied to activewear to prevent odor buildup, introducing chemicals such as triclosan that can leach out during wear and washing.
How Chemicals Migrate from Fabric
Chemical migration, or leaching, from polyester fabrics occurs through several mechanisms during normal use. The primary pathway is the interaction between the fabric and human sweat, as many textile additives are water-soluble or become soluble in the presence of moisture. Sweat acts as a solvent, dissolving chemicals like residual dyes and finishes from the fiber surface, which are then carried onto the skin.
Friction and abrasion are also factors, especially in tight-fitting clothing like sportswear, causing surface chemicals to mechanically rub off and transfer to the skin. Heat plays a significant role in increasing the rate of chemical release, as elevated temperatures enhance both volatility and diffusion. Intense exercise or exposure to hot environments can increase the rate at which volatile organic compounds, like acetaldehyde, are emitted.
The hydrophobic nature of polyester means it does not absorb moisture into the fiber structure like cotton. Instead, moisture is carried along the fiber surface, which facilitates the quick dissolution and transport of surface-level chemical finishes. Chemicals can also be released into the environment during washing cycles, contributing to water pollution and the release of microplastic fibers.
Steps to Minimize Chemical Contact
Consumers can take proactive steps to reduce their exposure to potentially harmful textile chemicals, starting with proper preparation of new garments. Pre-washing new polyester clothing multiple times helps remove excess surface finishes, unfixed dyes, and manufacturing residues that are prone to leaching. Using cold water and a mild, fragrance-free detergent is recommended to minimize the chemical reaction and mechanical stress that can break down finishes.
Choosing textiles certified by third-party standards offers a high degree of assurance regarding chemical safety. The OEKO-TEX Standard 100 is a globally recognized certification that tests every component of a textile for over 1,000 harmful substances, including heavy metals, formaldehyde, and certain dyes. The stricter requirements of this standard apply to textiles that have more intensive skin contact, such as baby clothes.
Avoiding high-heat exposure during the care and use of polyester items is another way to limit chemical volatility. Air-drying clothes instead of using a high-heat dryer can prevent the thermal release of volatile compounds and prolong the life of any remaining finishes. Finally, opting for natural fiber alternatives, such as organic cotton or linen, particularly for base layers worn directly against the skin, can eliminate exposure to many of the synthetic finishing chemicals associated with polyester.