High levels of microplastics found in human brains
The paper, published in the journal Nature
Medicine, found nanoplastics in each of the brain samples studied, and
found a potential link between the presence of the plastics and several types
of dementia.
“There’s much more plastic in our brains than I ever would
have imagined or been comfortable with,” said Matthew Campen, a doctor and researcher at
the University of New Mexico who is the lead author of the study.
The median concentration in brain samples collected from
people who died in 2024 was nearly 5 micrograms of plastic per gram of brain
tissue, tallying almost 0.5% by weight.
This total was 50% higher than it was just eight year prior,
from brain samples acquired in 2016 (for various reasons, most brain samples
become available these two years). This suggests the concentration of
microplastics found in human brains is going up as plastic waste and
microplastic pollution increases.
“You can draw a line — it’s increasing over time. It’s
consistent with what you’re seeing in the environment,” Campen said.
The paper also looked at 12 brains from patients who died with different types of dementia; half of them had been diagnosed with Alzheimer’s disease. These brains all contained more plastic by weight than healthy samples — roughly three to five times more, on average.
“That’s a little bit alarming,” Campen said, but he
emphasized that a causal relationship cannot be established yet, in part
because the brain’s normal clearance mechanisms are often impaired in dementia.
That being said, this potential link between microplastics and dementia needs
to be further explored.
Most of the organs came from the Office of the Medical
Investigator in Albuquerque, New Mexico, which investigates untimely or violent
deaths. A total of 28 brain tissue samples were collected in 2016, and 24 in
2024. From these bodies, liver and kidney samples were also analyzed. They
contained a median plastic concentration about 10 times lower than the brain.
The 12 brains from dementia patients came from the same
source, and date to between 2019 and 2024. The team also examined 27 brain
samples from people without dementia from other locations on the East Coast
dating to between 1997 and 2013. These contained significant less plastic on
average than the later samples, further supporting the idea that levels of
plastics are rising in this organ.
“The evidence here is concerning,” said Bethanie Carney Almroth,
an ecotoxicologist at the University of Gothenburg in Sweden who studies
microplastics but wasn’t involved in the paper.
When it comes to these insidious particles, “the blood-brain
barrier is not as protective as we’d like to think,” Almroth said, referring to
the series of membranes that keep many chemicals and pathogens from reaching
the central nervous system.
Some of the particles appeared to be too big to make it into
the brain, or even the blood. “Yet there they are.”
Nanoplastics are a subset of microplastics with a diameter
smaller than one micron. Larger microplastics are too large to make their way
into the brain. Most of the nanoplastic particles found in the brain are made
up of polyethylene, the study found.
This is the most commonly-made plastic and is used in
plastic bags, films, and many types of bottles used to store liquids and food.
The researchers used a technique called pyrolysis gas
chromatography–mass spectrometry to measure plastic in samples of the
prefrontal cortex from various brains. This technique heats up materials and
then identifies its chemical makeup.
The study also involved a variety of imaging techniques to
find and characterize the tiny bits of plastics, which primarily consisted of
nanoplastic shards.
This study received a lot of press attention in September
after The New Lede reported on
a pre-print that hadn’t yet been peer-reviewed. The now published paper is very
similar to that version previously reported on.
The Food and Drug Administration states on its
website that “current scientific evidence does not demonstrate that levels of
microplastics or nanoplastics detected in foods pose a risk to human health.”
The American Chemistry Council, which represents plastic and
chemical manufacturers, said in a statement that “the global plastics industry
is dedicated to advancing the scientific understanding of microplastics.”
The study also examined a number of brain samples collected
before 2016 at various locations on the East Coast; these all contained
plastics as well, though in slightly smaller concentrations.
Previous research will need to look at other parts of the
brain besides the white matter of the prefrontal cortex, Campen said.
Preliminary work on this has already found, however, that tiny plastic shards
are “fairly ubiquitous” throughout the brain, he said.
