Nylon is a common synthetic fiber and polyamide widely used in clothing, carpets, and other consumer goods. As public awareness of chemical exposure through textiles grows, questions have arisen about the safety of the substances used to manufacture and finish these materials. This analysis investigates the science behind this question, examining the mechanisms of endocrine disruption, the chemistry of nylon, and the current scientific consensus regarding its potential to act as an endocrine disruptor.
Understanding Endocrine Disruptors and Exposure Pathways
Endocrine-disrupting chemicals (EDCs) are defined as exogenous substances that interfere with the production, release, transport, metabolism, binding, or elimination of natural hormones in the body. These substances can mimic or block the action of hormones like estrogen, androgen, and thyroid hormones, leading to a deviation from normal homeostatic control. EDCs are linked to various health issues, including reproductive disorders, metabolic issues, neurological problems, and certain cancers.
Textiles serve as a common source of exposure to EDCs, especially synthetic fabrics and those treated for specific performance characteristics. Exposure can occur through several pathways when wearing clothing. Dermal absorption is a significant route, where chemicals leach from the fabric into the skin, particularly when sweat and friction are present. Inhalation of microfibers and nanoplastics is another concern, as textiles shed particles that can become airborne. Ingestion of fibers, particularly by young children through hand-to-mouth contact, provides a third potential route for these chemicals to enter the body.
The Chemical Composition of Nylon
Nylon is a synthetic polymer, a long chain of repeating molecular units called polyamides, which is derived from petrochemicals. The polymer structure itself, such as Nylon 6 or Nylon 6,6, is considered chemically stable and inert. The primary chemical concern does not stem from the core polymer chain but rather from residual starting materials and various chemical additives.
Nylon 6, for instance, is manufactured through the ring-opening polymerization of a monomer called caprolactam. While the polymerization process is highly efficient, trace amounts of unreacted caprolactam may remain embedded in the final fiber. Caprolactam itself has been the subject of some regulatory scrutiny, but its classification as an endocrine disruptor in finished textiles is not widely established. The more significant concern comes from non-polymeric chemicals introduced during processing.
Textile finishing processes require auxiliary chemicals to achieve desired properties like color, stain resistance, and durability. These additives include known or suspected EDCs such as phthalates, sometimes used to improve flexibility. Per- and polyfluoroalkyl substances (PFAS) are applied for water and stain resistance, and these are recognized for their persistence and endocrine-disrupting potential, particularly affecting the thyroid. Furthermore, certain dyes, flame retardants, and stabilizers are often used in nylon production. Many of these compounds, like some brominated flame retardants, are confirmed EDCs that can leach out of the material.
Scientific Consensus on Nylon’s Disruptive Potential
The scientific consensus indicates that the risk of endocrine disruption from a finished nylon product depends on the specific chemical treatments applied, rather than the polyamide structure itself. The core nylon polymer is largely inert, but finishing agents are the primary source of concern for hormonal interference. Research suggests that EDCs used in finishing treatments are not covalently bonded, meaning they can leach out over time with wear, washing, and exposure to sweat.
One study focused on the plastic material itself, using microscale and nanoscale particles (MNPs) of nylon, and found that even the particles, independent of traditional plasticizing chemicals, produced endocrine-disrupting effects when inhaled by female laboratory rats. This suggests that the concern is not limited to additives, but that the physical presence and breakdown of the nylon material may also contribute to biological effects, particularly through inhalation of microplastics. However, this study modeled inhalation exposure to fine powder, which may not directly reflect dermal exposure from wearing a garment.
When assessing the risk of consumer products, the variability in manufacturing is a factor, as the use of endocrine-disrupting additives is not uniformly regulated across all textile producers. To minimize potential exposure from finished nylon garments, consumers can take certain steps. Washing new synthetic garments before wearing them can help reduce residual processing chemicals and surface finishes. Choosing undyed or lightly colored materials may also reduce exposure to potentially problematic dyes. Ultimately, while nylon is not inherently an endocrine disruptor, the presence of unregulated additives means that many consumer nylon products carry a risk of exposure to EDCs.