Bioaccumulation of microplastics in decedent human brains, 2025, Nihart et al

Bioaccumulation of microplastics in decedent human brains

Alexander J. Nihart, Marcus A. Garcia, Eliane El Hayek, Rui Liu, Marian Olewine, Josiah D. Kingston, Eliseo F. Castillo, Rama R. Gullapalli, Tamara Howard, Barry Bleske, Justin Scott, Jorge Gonzalez-Estrella, Jessica M. Gross, Michael Spilde, Natalie L. Adolphi, Daniel F. Gallego, Heather S. Jarrell, Gabrielle Dvorscak, Maria E. Zuluaga-Ruiz, Andrew B. West, Matthew J. Campen

(Line breaks added)

Abstract
Rising global concentrations of environmental microplastics and nanoplastics (MNPs) drive concerns for human exposure and health outcomes.

Complementary methods for the robust detection of tissue MNPs, including pyrolysis gas chromatography–mass spectrometry, attenuated total reflectance–Fourier transform infrared spectroscopy and electron microscopy with energy-dispersive spectroscopy, confirm the presence of MNPs in human kidney, liver and brain.

MNPs in these organs primarily consist of polyethylene, with lesser but significant concentrations of other polymers. Brain tissues harbor higher proportions of polyethylene compared to the composition of the plastics in liver or kidney, and electron microscopy verified the nature of the isolated brain MNPs, which present largely as nanoscale shard-like fragments.

Plastic concentrations in these decedent tissues were not influenced by age, sex, race/ethnicity or cause of death; the time of death (2016 versus 2024) was a significant factor, with increasing MNP concentrations over time in both liver and brain samples (P = 0.01). Finally, even greater accumulation of MNPs was observed in a cohort of decedent brains with documented dementia diagnosis, with notable deposition in cerebrovascular walls and immune cells.

These results highlight a critical need to better understand the routes of exposure, uptake and clearance pathways and potential health consequences of plastics in human tissues, particularly in the brain.

Link | PDF (Nature Medicine) [Open Access]

 

Decedent means deceased, in case anyone else didn't know.

Concentration of total plastic (top) and only polyethylene (bottom) in 2016 and 2024 organs. Higher in 2024 in brain and liver, but not kidney. I wonder why the spread of the values for the brain seems too get much more condensed in 2024.


Age, sex, race/ethnicity and cause of death having no association with plastic concentration in the brain is interesting.

Regarding brains from people with dementia having higher plastic concentration, they say that's expected for several reasons that are not plastic being causal for dementia:

 

It might be that there’s an upper limit for how much MNP that can accumulate in the brain, and that most people nowadays are exposed to enough MNP to comfortably reach the upper limit?

 

I wonder how robust the storage is where they can compare brains from eight years ago to recently deceased people's brains. Is it not possible that the mass of the brain possibly increases in 8 years from absorbing the formaldehyde or something, which would show up as lower plastic concentration? I don't know anything about tissue storage, so maybe this has all been figured out.

 

How would that affect the measurements?
If you take the weight or volume of the piece you check and divide it by the total mass or volume of the brain, the proportions are constant regardless of expansion.

If they store the pieces over a long period of time, I assume they measure and log the original proportions when they divide it in the first place?

 

Maybe I'm not understanding, but the concentration is in micrograms of plastic per gram of tissue. I don't see them say they use historical tissue measurements. So if the brain absorbed some formalin over time and increased its mass, then the concentration of plastic would go down.

 

I do know, but that doesn't stop me reading decadent. Every time.

 

You’re right - I missed that.

 

On PR there was mention of a paper which found that the microplastics were found in the myelin sheaths. I didn't check the validity of the findings. The paper in this thread seemed unclear as to where the particles were found: they were assuming that they weren't all in the vascular space.

 

Where do they assume that? And what would be the significance if that was the case?

 

I don't feel like calling up the paper again, but I did see somewhere in it that they were assuming that the particles were not only in the vascular space. When I first read an article about finding microplastics in the brain, my first thought was "Did they check whether the particles were just in the plumbing?" I could imagine finding stuff in the vascular space without getting past the BBB.

If the particles are getting lodged in the myelin sheaths, that could affect signal transmission. As I understand it, the sheaths are frequently stripped off and replaced (in new configurations) as the neural pathway changes function (a memory strengthens, a pain signal gets reduced, etc). However, since that process is adaptive, maybe it would adapt to microplastics altering sheath properties.

 

If this was the case, wouldn't plastic levels be similar in all three organs? Instead, it's about ten times higher in the brain than in the liver or kidneys in this paper.

Edit: Oh, that's what they said too:

 

expert reaction to a study investigating the accumulation of microplastics in human organs

Some snippets:

Prof Oliver Jones, Professor of Chemistry, RMIT University

Prof Theodore B. Henry, Professor of Environmental Toxicology from the School of Energy, Geoscience, Infrastructure and Society at Heriot-Watt University

 

haha I clicked on the thread to find out what a 'decadent' brain was... I had a cartoon of a brain on a chaise longue sipping champagne & eating posh chocolates, in my mind