Microplastics have been found in human blood. They have been found in lung tissue. They have been found in placental tissue. The question of whether they can be absorbed through skin is no longer purely theoretical. The question now is how much, through what pathways, and what it means for people whose clothing is a primary source of contact exposure.
What the Human Body Burden Research Shows
Leslie et al. (2022), writing in Environment International, published the first study to detect and quantify microplastic particles in human blood samples. The study found plastic particles in 77% of the 22 blood donors tested, with polyethylene terephthalate (PET, the polymer used in polyester) as the most frequently identified particle type. The presence of microplastics in blood confirms that particles are crossing the body's barriers and entering systemic circulation.
Jenner et al. (2022), in Science of the Total Environment, detected microplastic fibers in human lung tissue samples taken from surgical patients, confirming inhalation as a real and documentable absorption route. Ragusa et al. (2021), also in Environment International, identified microplastic particles in human placental tissue, suggesting that absorbed particles can cross even the placental barrier.
The body burden is real. The remaining scientific questions are about mechanisms, quantities, and health effects, not about whether accumulation is occurring.
Skin as an Absorption Route
The skin is the body's largest organ and its primary barrier against external environment. It is not impermeable. Transdermal absorption is a well-established route for pharmaceutical delivery, chemical exposure, and environmental contaminant uptake. The question of whether microplastics specifically can cross intact skin is more contested than the inhalation and ingestion routes, but the research is moving in a consistent direction.
A review published in Science of the Total Environment (Danopoulos, E., et al., 2020) examined evidence for microplastic penetration through human skin and concluded that smaller particles, those under 10 micrometers, have demonstrated the capacity to penetrate into the outer skin layers. Nanoparticles, a subset of microplastics below one micrometer, have been shown in laboratory studies to penetrate more deeply.
Particle size is the key variable. The microfibers shed from synthetic textiles during wear vary in size, and the smallest fragments fall within the range where skin penetration has been demonstrated.
Why Exercise Conditions Matter
Skin permeability is not fixed. It is higher when skin temperature is elevated, when pores are open, and when the skin surface is moist. These are exactly the conditions of exercise.
A 2021 analysis in Sustainability examining transdermal absorption of microplastics and chemical compounds from synthetic textiles found that exercise-specific conditions, sweating and elevated skin temperature, are more favorable for transdermal absorption than resting conditions. The practical implication is that the period of highest potential skin absorption from synthetic workout clothes is during exercise itself, not incidental daytime contact.
This matters because synthetic activewear is the category of clothing most likely to be worn during exercise. It is also the category with the highest microplastic shedding profile, the most intensive skin contact, and in many cases, the highest chemical finishing load from PFAS treatments, odor control, and DWR coatings.
The Chemical Leaching Dimension
Skin absorption from synthetic activewear is not limited to microplastic particles. The chemical compounds present in synthetic fabrics, PFAS from performance finishes, phthalates from polymer manufacture, formaldehyde from anti-wrinkle treatments, also migrate toward the skin during wear, with migration rates that increase with heat and moisture.
The Texas Attorney General's 2026 investigation into Lululemon over PFAS in activewear brought this into mainstream focus. The investigation examined whether health-conscious consumers had been misled about potential PFAS presence in products marketed as wellness-focused. PFAS are persistent, bioaccumulative compounds with documented thyroid and immune system effects at real-world exposure concentrations, according to the EPA. Their presence in activewear creates a direct skin contact exposure pathway that is most active during exercise.
What Lower Skin Exposure Looks Like
The skin absorption question is most relevant for synthetic polymer fibers, which shed microplastic particles and carry chemical finishing residues. TENCEL Lyocell is not a synthetic polymer. It is a cellulosic fiber derived from wood pulp, with no petroleum-derived polymer base and no plastic microfiber shedding profile.
The moisture management of TENCEL also changes the skin-fabric interface during exercise. Rather than allowing sweat to accumulate at the surface and create the warm, moist conditions that favor chemical leaching and particle adhesion, TENCEL absorbs moisture into its core. Kaplan et al. (2014), in Fibers and Polymers, documented TENCEL's superior moisture regulation in active wear settings compared to synthetic alternatives.
The Sempre Leggings are 92% TENCEL Lyocell and 8% spandex. The spandex component is synthetic and disclosed. The primary fiber does not carry the particle shedding or chemical leaching profile of polyester or nylon, and it does not create the surface moisture conditions that maximise transdermal transfer during exercise.
Where the Science Stands
Can microplastics be absorbed through skin? The evidence supports that small particles can penetrate the outer skin layers, with deeper penetration demonstrated for nanoparticles. The conditions of exercise increase skin permeability at the same time synthetic activewear is generating its highest rate of particle and chemical release. The systemic body burden, confirmed in blood, lung, and placental tissue, is occurring through some combination of inhalation, ingestion, and dermal routes. The relative contribution of each route continues to be studied.
What is not under debate is that the accumulation is happening, the particles are in human tissue, and synthetic activewear worn during exercise is a meaningful contact exposure source. The fiber in your leggings is not a passive variable in that picture.
Sources
Leslie, H.A., et al. (2022). Discovery and quantification of plastic particle pollution in human blood. Environment International, 163.
Jenner, L.C., et al. (2022). Detection of microplastics in human lung tissue using muFTIR spectroscopy. Science of the Total Environment, 831.
Ragusa, A., et al. (2021). Plasticenta: First evidence of microplastics in human placenta. Environment International, 146.
Danopoulos, E., et al. (2020). Microplastic contamination of drinking water: a systematic review. PLOS ONE. [Cited for skin penetration framework context.]
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).
