Polyethylene terephthalate, commonly known as polyester or PET, is the most widely used synthetic fiber in the world, dominating both the textile and packaging industries. Its low cost, durability, and versatility have made it a ubiquitous material in clothing, carpets, and plastic bottles. Despite its widespread use, growing public awareness about the chemicals involved in its production has led to questions about whether polyester is truly non-toxic. Determining its safety requires separating the inherent properties of the polymer from the substances added during manufacturing and the physical risks associated with its degradation.
The Chemical Composition of Polyester
Polyester is a type of plastic derived from petroleum, created through a reaction between ethylene glycol and terephthalic acid. The resulting substance is a linear, long-chain polymer known as polyethylene terephthalate (PET), which forms a semi-crystalline structure. In its final, solid form, the base PET polymer is considered chemically stable and generally inert, meaning it does not readily react with other substances or break down under normal conditions. This inherent stability makes PET a preferred material for food-grade packaging, such as water and soda bottles.
The polymer chains provide the finished fiber with characteristics like high strength, resistance to wrinkling, and low water absorption. However, the safety profile of polyester is complex because the finished material is not just the inert polymer. The manufacturing process and the additives needed to create a usable fiber introduce other substances that present the primary chemical concerns for human exposure.
Health Concerns from Manufacturing Additives
The initial safety of the inert PET polymer is complicated by chemicals intentionally introduced during the polymerization and finishing stages. One significant substance is antimony, typically used as a catalyst to speed up the production of the PET resin. Antimony is a toxic heavy metal. While most of it remains trapped within the polymer matrix, small amounts can leach out, especially when exposed to heat or acidic liquids, such as sweat or certain beverages. This leaching increases with prolonged storage time and higher temperatures, raising concerns for items worn close to the skin.
Beyond the catalyst, numerous finishing treatments are applied to polyester textiles to achieve desired consumer properties. These treatments include water repellents, flame retardants, and anti-wrinkle agents, many of which contain compounds known as endocrine disruptors. Per- and polyfluoroalkyl substances (PFAS) are often used for water resistance, while Bisphenol-A (BPA) may be incorporated to improve a fabric’s lifespan or add anti-static properties. These chemicals can migrate from the fabric onto the skin and may be absorbed through sweat-moistened skin, interfering with the body’s hormonal systems.
Colorants, known as disperse dyes, are another source of chemical exposure, as they require high temperatures to bond with the synthetic fiber. Residual dye components remaining on the fabric can cause contact dermatitis or irritation in sensitive individuals. Newly manufactured polyester items may also release Volatile Organic Compounds (VOCs) into the air through off-gassing. These airborne chemicals contribute to indoor air pollution and have the potential to cause respiratory irritation or exacerbate conditions like asthma.
The Issue of Microplastic Fiber Exposure
Separate from the chemical additives, the physical degradation of polyester fabric creates the issue of microplastic exposure. Polyester clothing, like all synthetic textiles, sheds microscopic plastic fibers—microfibers—during washing, drying, and daily wear. A single load of laundry can release hundreds of thousands of these tiny particles, which are too small for most wastewater treatment plants to filter out.
These microplastic fibers become a source of human exposure through inhalation and ingestion. Airborne microfibers shed from clothing, bedding, and carpets accumulate in household dust, posing an inhalation risk when they settle deep within the lungs. Scientists have detected microplastics in human blood, lung tissue, and the placenta, indicating systemic exposure that is still being fully researched.
The health concern stems from two sources: the physical presence of the fibers and the chemicals they carry. The plastic particles themselves may cause low-level inflammation or lung issues. Moreover, microplastics can act as carriers, adsorbing chemicals from the environment, including persistent organic pollutants, and then transferring them into the body upon ingestion.
Strategies for Reducing Exposure
Given the risks associated with both chemical additives and microfiber shedding, consumers can adopt specific practices to minimize their exposure. One direct method to reduce chemical contact is to wash new polyester items before wearing them, which helps rinse away residual surface chemicals like manufacturing finishes and excess dyes. Prioritizing natural fibers like organic cotton, wool, or linen for clothing that has prolonged contact with the skin can also reduce exposure to the chemical additives frequently found in synthetics.
To address the microplastic shedding issue, adopting careful laundry habits can significantly mitigate the environmental and indoor air release of microfibers.
- Washing synthetic garments less frequently, using cold water, and opting for shorter, gentler wash cycles reduces the friction that causes fiber breakage.
- Specialized microfiber-catching laundry bags or installing a dedicated microplastic filter on a washing machine can trap a substantial percentage of the fibers before they enter the wastewater system.
- Air-drying clothes instead of using a tumble dryer is a simple step to lower household microplastic dispersion, as dryers can also release microfibers into the air.