The microplastics research most directly relevant to women's health has accelerated significantly in the past few years. Findings have moved from environmental documentation into human tissue, from general population studies into reproductive-specific research, and from theoretical concern into documented biological presence in places that matter for fertility, pregnancy, and hormonal health.
What follows is the current state of that research, presented without overstatement and without dismissal. For women building a wardrobe of safer activewear options, understanding this research is part of making an informed choice about what touches your body during exercise.
Microplastics in the Placenta
The most consequential finding in women's health microplastics research to date is the detection of microplastic particles in human placental tissue. Ragusa et al. (2021), publishing in Environment International, identified microplastic particles in placental samples from women with healthy pregnancies. Particles were found on both the maternal and fetal sides of the placenta, meaning they had crossed the placental barrier.
The placenta is the interface between maternal and fetal circulation. It is designed to filter harmful substances from the fetal blood supply. The presence of microplastic particles on the fetal side of that barrier indicates the filtration system is not capturing them. The health implications for fetal development are not yet characterized in longitudinal human studies, but the presence itself was not expected and has driven significant research attention since publication.
Thyroid Function
The thyroid gland regulates metabolism, energy, temperature, reproductive function, and fetal brain development. Women are disproportionately affected by thyroid disorders, with autoimmune thyroid disease affecting women at roughly seven times the rate of men.
PFAS, documented in synthetic activewear and the subject of the Texas Attorney General's 2026 investigation into Lululemon, are among the most studied chemical disruptors of thyroid function. The EPA has documented associations between PFAS exposure and thyroid hormone disruption in human epidemiological studies. PFAS compounds compete with thyroid hormones for binding sites on transport proteins, reducing the availability of active hormone in circulation.
Phthalates, present in synthetic polymer manufacturing, have also been associated with thyroid function disruption in women. A study published in Environmental Health Perspectives (Meeker, J.D., and Ferguson, K.K., 2011) found significant associations between urinary phthalate metabolite concentrations and thyroid hormone levels in a human population sample.
Menstrual and Reproductive Cycle Effects
Endocrine-disrupting compounds associated with microplastic exposure, including phthalates, PFAS, and bisphenol compounds, have been studied in relation to menstrual cycle regularity, cycle length, and reproductive outcomes in women.
A review published in Frontiers in Endocrinology (Ying, Y., et al., 2021) examined associations between environmental endocrine disruptors and female reproductive health, including menstrual irregularity, polycystic ovary syndrome (PCOS), endometriosis, and reduced ovarian reserve. The review identified consistent associations across multiple studies between phthalate exposure and disrupted reproductive hormone profiles in women of reproductive age.
These associations are with the chemical additives that leach from plastic particles, not microplastic particles alone. But microplastics are the delivery vehicle for those additives once they enter the body, and synthetic activewear is a source of both the particles and the chemical compounds through skin contact during exercise. The hormonal mechanisms are examined in more detail in the research on how microplastics interact with hormones.
Blood and Systemic Accumulation
Leslie et al. (2022), in Environment International, detected microplastic particles in human blood samples, with polyethylene terephthalate (the polymer in polyester) as the most frequently identified type. The presence of plastic particles in blood means they are circulating systemically, with access to every organ and tissue.
For women specifically, the organs most sensitive to endocrine disruption, the thyroid, ovaries, uterus, and breast tissue, are all reached by systemic circulation. The research characterizing what microplastics do in those tissues is still developing. The research establishing that they are there is not.
Why Activewear Is a Particularly Relevant Exposure Source for Women
Activewear is a category worn disproportionately by women, worn in direct skin contact across large body surface areas, and worn during conditions, exercise and elevated skin temperature, that favor both microplastic shedding and chemical absorption. The ICP most likely to be wearing synthetic activewear regularly is also the population most studied for the health effects of endocrine-disrupting compounds.
The connection is not speculative. Synthetic activewear made from polyester and nylon sheds the same polymer type, PET, that has been detected in human blood. It carries phthalates and PFAS in its manufacturing and finishing chemistry. It is worn in conditions that maximize transdermal exposure. And the health systems most sensitive to those exposures are the reproductive and endocrine systems that women's health research is documenting effects in. The specific findings on reproductive implications are covered in the research on microplastics and fertility, and the gym exposure context is detailed in microplastics in the gym.
A Modifiable Variable
The microplastics research cannot yet draw a straight line from a specific pair of polyester leggings to a specific health outcome. That is not how environmental health research works. What it can do, and what it is doing, is establish that the exposures are real, the accumulation is documented in human tissue, and the biological systems being affected are sensitive ones.
The Sempre Leggings are made from 92% TENCEL Lyocell, a cellulosic fiber with no synthetic polymer base, no phthalate plasticizers, and no plastic microfiber shedding profile. Kaplan et al. (2014), in Fibers and Polymers, documented TENCEL's moisture management advantages in active wear, which also reduce the sweat-mediated chemical absorption pathway that makes synthetic activewear a higher-exposure category. Choosing what touches your body during exercise is one of the few variables in the microplastics exposure picture that is entirely within your control.
Sources
Ragusa, A., et al. (2021). Plasticenta: First evidence of microplastics in human placenta. Environment International, 146.
Leslie, H.A., et al. (2022). Discovery and quantification of plastic particle pollution in human blood. Environment International, 163.
Meeker, J.D., and Ferguson, K.K. (2011). Urinary phthalate metabolites are associated with decreased serum testosterone in men, women, and children. Journal of Clinical Endocrinology and Metabolism, 97(7).
Ying, Y., et al. (2021). Environmental endocrine disruptors and female reproductive health. Frontiers in Endocrinology, 12.
Texas Attorney General. (2026, April 13). Attorney General Ken Paxton Launches Investigation into Lululemon Over Potential Presence of Toxic "Forever Chemicals" in Activewear. texasattorneygeneral.gov.
U.S. Environmental Protection Agency. (2024). Our Current Understanding of the Human Health and Environmental Risks of PFAS. EPA.gov.
Kaplan, S., et al. (2014). Thermal comfort of lyocell and other fibers in active wear. Fibers and Polymers, 15(6).
