Polyester itself is not inherently a xenoestrogen, but it can be associated with chemicals that act as xenoestrogens during its production and finishing processes.625 For example, terephthalic acid (TPA), a major chemical precursor of polyethylene terephthalate (PET) containers, has been shown to have estrogenic effects on non-malignant human breast epithelial cells, increasing the estrogen receptor alpha (ERα) to estrogen receptor beta (ERβ) ratio.52 Additionally, polyester products may contain additives such as phthalates, which are well-documented endocrine disruptors.
Several studies suggest that polyester clothing may affect fertility, particularly in men. Research indicates that wearing polyester underwear can lead to a decrease in sperm count and quality, potentially causing infertility. For instance, a study published in Contraception found that 14 men who wore polyester scrotal slings for 12 months became azoospermic (had no sperm in their semen) after a mean of 139.6 days.58
In another study involving dogs, dogs wearing polyester underpants showed a significant decrease in sperm count and motility, with an increase in abnormal sperm forms.9 The polyester group also exhibited degenerative changes in testicular biopsies, while the cotton and control groups showed no significant changes.9
The mechanism behind this effect is not fully understood, but it may involve electrostatic potentials generated by the polyester fabric and disordered thermoregulation.589 However, these effects are reversible; once the polyester clothing is removed, sperm concentration levels typically return to pre-test levels within 140-170 days.
Based on this understanding, I do not trust using polyester, whatever the reason being.