What Microplastics Are Doing Inside Your Body
They're not just in the ocean anymore. They're in you.
For years, the conversation about microplastics was framed as an environmental issue. Oceans. Wildlife. Ecosystems. The kind of problem that felt distant and abstract.
That framing no longer holds.
In February 2025, a study published in Nature Medicine confirmed what researchers had long suspected: microplastics and nanoplastics are accumulating in human brain tissue, at higher concentrations than in any other organ examined, and the levels are increasing over time in direct proportion to global plastic production.¹
This isn't a distant concern. It's already happening inside every person reading this.
Where They've Been Found
The brain:
Brain tissues harbor higher proportions of polyethylene compared to the composition of plastics in the liver or kidney, and electron microscopy verified the nature of the isolated brain microplastics, which present largely as nanoscale shard-like fragments. The total mass of plastics found in brain samples increased by around 50% between 2016 and 2024.¹
The blood:
Microplastics have been detected in human blood across multiple independent studies, confirming that once ingested or inhaled, particles enter the circulatory system and are transported throughout the body.
The lungs:
Synthetic fibres from clothing, gym gear, and airborne particles have been found in lung tissue, with a 2025 estimate suggesting people may inhale tens of thousands of microplastic particles each day.²
The heart and arteries:
A 2024 multicentre study found polypropylene in the carotid artery plaques of 58% of participants examined. Those with detectable microplastics in their arterial plaques showed a significantly higher risk of cardiovascular events than those without.³
The testicles:
Scientists reported in 2024 that microplastics were found in every human testicular sample examined, raising questions about potential implications for male reproductive health that researchers are continuing to investigate.
Why Athletes Specifically Should Pay Attention
Higher fluid intake means higher exposure:
Athletes drink significantly more water per day than the average sedentary adult. More fluid intake from plastic vessels means more cumulative microplastic ingestion per day, every day, over years of training.
Higher breathing rate means more inhalation:
During exercise, breathing rate increases substantially. Synthetic gym environments, polyester clothing, and rubber flooring all contribute to the airborne microplastic load. More breaths per minute means more particles inhaled per session.
Skin absorption under sweat:
A 2024 University of Birmingham study found that microplastics can act as carriers of harmful chemicals that enter the bloodstream through skin, with absorption increasing when skin is warm and moist, exactly the conditions during and after exercise.²
What the Research Doesn't Say (Yet)
It's worth being direct here: the research on what microplastics are actually doing to human health is still developing. The studies above confirm presence and accumulation. They do not yet confirm specific causal health outcomes in humans with the same certainty.
What they do confirm is that accumulation is real, it's increasing over time, and it correlates directly with how much plastic we interact with.
That's enough to make the question of daily plastic exposure worth taking seriously, particularly for people who are putting a lot of effort into every other variable that affects their health and performance.
The Highest Frequency Daily Contact Points
The research on how microplastics enter the body points consistently to ingestion and inhalation as the primary routes. For gym-goers, the highest frequency ingestion contact point is almost always the same: the shaker bottle, used multiple times a day, every day.
Removing that single variable doesn't solve the broader problem of microplastic exposure. But it is the most practical, immediate step available to anyone who trains regularly and wants to be deliberate about what goes into their body.
Sources
- Nihart, A.J. et al. "Bioaccumulation of microplastics in decedent human brains." Nature Medicine, February 2025. Found microplastics and nanoplastics in human brain, liver and kidney tissue, with brain tissue accumulating higher concentrations than other organs, and a 50% increase in brain microplastic levels between 2016 and 2024. URL: https://www.nature.com/articles/s41591-024-03453-1
- Tripulse, July 2025. Citing a 2024 University of Birmingham study finding that microplastics act as carriers of harmful chemicals into the skin, with absorption increasing during warm, moist conditions (i.e. exercise), and a 2025 estimate that people may inhale tens of thousands of microplastic particles per day. URL: https://tripulse.co/blogs/news/how-to-avoid-microplastics-in-clothing-a-step-by-step-guide
- The Lancet Planetary Health, December 2025. A 2024 multicentre study of 257 individuals found polypropylene in the carotid artery plaques of 58.4% of participants, with those carrying detectable microplastics showing significantly higher risk of cardiovascular events. URL: https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(25)00268-2/fulltext
