Fertility research has historically focused on genetics, anatomy, and lifestyle factors. In the past several years, a new category of investigation has emerged: environmental chemical exposure and its relationship to reproductive outcomes. Microplastics and the compounds associated with them are increasingly central to that conversation.
The findings are preliminary in some areas and more established in others. None of them are comfortable. For those actively evaluating their exposure from daily garments, shop non toxic activewear built from cellulosic fibers rather than synthetic polymers.
Microplastics in Reproductive Tissue
The most direct evidence connecting microplastics to fertility is their documented presence in reproductive tissue. A study published in Science of the Total Environment (Rotchell, J.M., et al., 2023) detected microplastic particles in human testicular tissue samples. A parallel body of research has documented microplastic presence in ovarian follicular fluid, the environment in which eggs develop before ovulation.
Ragusa et al. (2021), in Environment International, found microplastic particles in human placental tissue on both the maternal and fetal sides, establishing that these particles cross the placental barrier and are present in the environment surrounding a developing fetus. Taken together, these findings document that microplastics reach the specific tissues and fluids most directly involved in human reproduction.
Their presence in those locations does not prove causation of fertility impairment. It does establish that the biological proximity to reproductive function exists, which makes the mechanistic question worth examining seriously.
Phthalates and Reproductive Hormone Disruption
The chemical leachates from plastic particles are where the fertility research is more developed than the particle-level evidence. Phthalates, plasticizers used in synthetic polymer manufacturing and present in polyester and nylon activewear, are among the most studied reproductive toxicants in environmental health research.
The National Toxicology Program has concluded that several phthalates are reproductive and developmental toxicants based on animal studies. In humans, the evidence is associational but consistent. A review published in Frontiers in Endocrinology (Ying, Y., et al., 2021) documented associations between phthalate exposure and reduced ovarian reserve, menstrual irregularity, and altered reproductive hormone profiles in women. In men, studies have associated phthalate metabolite concentrations with reduced sperm motility, morphology, and count.
Phthalates do not need to be present at high concentrations to produce endocrine effects. The endocrine system is sensitive to hormonal signals at very low concentrations, and phthalates operate by mimicking and blocking those signals. Chronic low-level exposure from daily sources, including synthetic clothing worn during exercise, contributes to cumulative body burden. The broader hormonal picture is covered in the research on how microplastics interact with hormones.
PFAS and Fertility Outcomes
PFAS, per- and polyfluoroalkyl substances used in durable water repellent treatments on synthetic activewear, have a growing body of human research linking them to fertility outcomes. The EPA has documented associations between PFAS exposure and reduced fertility in women, longer time to pregnancy, and pregnancy-induced hypertension based on human epidemiological studies.
The Texas Attorney General's 2026 investigation into Lululemon explicitly cited emerging research connecting synthetic materials in activewear to infertility as part of the public health rationale for examining whether consumers had been misled. That framing, from a state enforcement action rather than an advocacy group, reflects how far this research has moved into mainstream regulatory concern.
PFAS accumulate in the body over time and do not readily break down. Repeated exposure from activewear worn during exercise, when skin permeability is elevated, contributes to the body burden that human fertility studies are measuring as an exposure variable.
Male Fertility: An Underreported Dimension
Most activewear-related health conversations focus on women. The fertility research on microplastics and synthetic chemical exposure is substantially bilateral. The testicular tissue findings and sperm quality associations with phthalate and PFAS exposure apply to male wearers of synthetic activewear equally. Sperm counts have declined globally by approximately 50% over the past 50 years according to a meta-analysis published in Human Reproduction Update (Levine, H., et al., 2017), with environmental chemical exposure identified as a probable contributing factor alongside lifestyle variables.
Men who train regularly in synthetic activewear are subject to the same exposure pathways during exercise: elevated skin temperature, open pores, direct fabric contact, and sweat-mediated chemical migration from synthetic fabric surfaces. For additional context on indoor gym exposure specifically, the research on microplastics in the gym covers that environment in detail.
Reducing Exposure from Activewear
Fertility is affected by many variables, most of which are not within easy control. The fabric in your workout clothes is one that is. TENCEL Lyocell is not a synthetic polymer. It contains no phthalate plasticizers, carries no PFAS finishing history when properly certified, and does not shed plastic microfibers. The exposure pathways that connect synthetic activewear to the reproductive tissue findings above do not apply in the same way to a cellulosic fiber.
The Sempre Leggings are 92% TENCEL Lyocell, certified to OEKO-TEX Standard 100, which independently tests for phthalates, PFAS, formaldehyde, and heavy metals. Kaplan et al. (2014), in Fibers and Polymers, documented TENCEL's structural moisture management in active wear, which reduces the sweat-mediated absorption conditions that make synthetic activewear a higher chemical exposure category during exercise. For women specifically, the research on microplastics and women's health covers the reproductive and systemic dimensions most relevant to female wearers.
The State of the Evidence
The straight line from synthetic activewear to a specific fertility outcome has not been drawn in a single controlled human study. That is not how environmental health research on chronic low-level exposures works, and it is not a reasonable standard to require before taking the evidence seriously.
What exists is: microplastics in reproductive tissue, chemical leachates from those plastics with documented reproductive toxicity, exposure pathways that are most active during the conditions of exercise, and a growing body of associational research linking PFAS and phthalate body burden to measurable fertility outcomes. That is a coherent picture, even if it is not yet a complete one.
Sources
Ragusa, A., et al. (2021). Plasticenta: First evidence of microplastics in human placenta. Environment International, 146.
Ying, Y., et al. (2021). Environmental endocrine disruptors and female reproductive health. Frontiers in Endocrinology, 12.
National Toxicology Program. (2012). NTP Monograph: Phthalates. US Department of Health and Human Services.
Levine, H., et al. (2017). Temporal trends in sperm count: a systematic review and meta-regression analysis. Human Reproduction Update, 23(6).
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).
