Moisture-Wicking Fabric Sheds Microplastics Onto Your Skin Every Session
The performance feature you bought your gym kit for is also the mechanism delivering microplastics into your skin.
Moisture-wicking works by pulling sweat away from the skin surface through capillary action in the synthetic fibre structure. It's the main selling point of polyester, nylon, and spandex activewear, and it genuinely works for its stated purpose.
What the marketing doesn't mention is what else travels in the same direction.
What the 2024 Research Found
In April 2024, researchers at the University of Birmingham published the first experimental evidence that chemical additives in microplastics can leach into human sweat and then be absorbed through the skin into the bloodstream. The study used 3D human skin equivalent models and found that up to 8% of flame-retardant chemicals present in microplastics were taken up by skin over a 24-hour exposure window.¹
Critically, sweatier skin absorbed significantly more than dry skin. The moment synthetic activewear is most useful is also the moment it becomes most chemically permeable.
Sweat acts as a carrier:
Sweat doesn't just remove heat. It acts as a solvent that dissolves chemical additives present in synthetic fibres and carries them toward the skin surface rather than away from it. Under exercise conditions, that process is amplified by elevated skin temperature, increased blood flow, and sustained friction between fabric and skin.¹
The 2025 Frontiers in Sports and Active Living review confirmed the mechanism:
A 2025 peer-reviewed review specifically on microplastics and exercise confirmed that sportswear can release plastic particles absorbed through the skin via friction and sweat during exercise, noting this as an exposure pathway specific to athletes and fitness enthusiasts that warrants dedicated research.²
Microplastics enter through sweat glands and hair follicles:
Beyond chemical absorption, emerging evidence suggests that very small plastic fibres can enter the body through sweat glands, hair follicles, or compromised skin, particularly under conditions of prolonged friction and heat typical of exercise.¹
The Cumulative Picture
A serious gym-goer training five days a week wears synthetic activewear for roughly 300 to 400 hours per year. Each session involves elevated sweat production, skin temperature, and sustained fabric friction.
That is a significant cumulative dermal exposure window. Combined with the airborne microplastic exposure discussed in Post 12 (gym environments have consistently higher airborne particle concentrations than outdoor spaces), the total microplastic exposure profile of a regular gym-goer is meaningfully higher than the average sedentary adult.
The Controllable Variables
You can't easily change the gym floor or the fibres in other people's clothing. Your own activewear is different. It's a choice you make repeatedly, and it's in contact with your skin under the highest absorption conditions imaginable.
The shaker was the first variable we addressed because it's the highest-frequency food-contact point. The clothing question is the one we're building toward next, for the same reason and to the same standard.
Sources
- University of Birmingham, April 2024. Published in Environment International. First experimental evidence that chemical additives in microplastics, specifically flame retardants, can leach into human sweat and be absorbed through the skin into the bloodstream. Found up to 8% chemical uptake through sweat-moistened skin using 3D human skin equivalent models. Sweatier skin absorbed significantly more than dry skin. URL: https://www.sciencedaily.com/releases/2024/04/240419131901.htm
- Jiao X., Cao Q., Deng Z. "Microplastics and exercise: impacts on performance and physiological health." Frontiers in Sports and Active Living, August 2025. Peer-reviewed review confirming that sportswear can release plastic particles absorbed through the skin via friction and sweat during exercise, and that exercise-specific exposure routes (inhalation, skin contact, ingestion via sports drinks) are distinct from general population exposure. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC12403993
