The study, which has yet to be independently verified by other scientists, has been described in the media as scary, shocking and alarming.
Plastic is in our clothes, cars, mobile phones, water bottles and
food containers. But recent research adds to growing concerns about the impact
of tiny plastic fragments on our health.
A study from the United States has, for
the first time, found microplastics in human brains. The study, which has yet
to be independently verified by other scientists, has been described in the
media as scary, shocking and alarming.
But what exactly are microplastics?
What do they mean for our health? Should we be concerned?
What
are microplastics? Can you see them?
We often consider plastic items to be indestructible. But plastic
breaks down into smaller particles. Definitions vary but generally
microplastics are smaller than five millimetres.
This makes some too small to be seen with
the naked eye. So, many of the images the media uses to illustrate articles
about microplastics are misleading, as some show much larger, clearly visible
pieces.
Microplastics have been reported in many
sources of drinking water and everyday food items. This means we are constantly
exposed to them in our diet.
Such widespread, chronic (long-term)
exposure makes this a serious concern for human health. While research
investigating the potential risk microplastics pose to our health is limited,
it is growing.
How
about this latest study?
The study looked at concentrations of
microplastics in 51 samples from men and women set aside from routine autopsies
in Albuquerque, New Mexico. Samples were from the liver, kidney and brain.
These tiny particles are difficult to
study due to their size, even with a high-powered microscope. So rather than
trying to see them, researchers are beginning to use complex instruments that
identify the chemical composition of microplastics in a sample. This is the
technique used in this study.
The researchers were surprised to find up
to 30 times more microplastics in brain samples than in the liver and kidney.
They hypothesised this could be due to
high blood flow to the brain (carrying plastic particles with it).
Alternatively, the liver and kidneys might be better suited to dealing with
external toxins and particles. We also know the brain does not undergo the same
amount of cellular renewal as other organs in the body, which could make the
plastics linger here.
The researchers also found the amount of
plastics in brain samples increased by about 50 per cent between 2016 and 2024.
This may reflect the rise in environmental plastic pollution and increased
human exposure.
The microplastics found in this study were
mostly composed of polyethylene. This is the most commonly produced plastic in
the world and is used for many everyday products, such as bottle caps and
plastic bags.
This is the first time microplastics have
been found in human brains, which is important. However, this study is a
“pre-print”, so other independent microplastics researchers haven't yet
reviewed or validated the study.
How
do microplastics end up in the brain?
Microplastics typically enter the body
through contaminated food and water. This can disrupt the gut microbiome (the
community of microbes in your gut) and cause inflammation. This leads to
effects in the whole body via the immune system and the complex, two-way
communication system between the gut and the brain. This so-called gut-brain
axis is implicated in many aspects of health and disease.
We can also breathe in airborne
microplastics. Once these particles are in the gut or lungs, they can move into
the bloodstream and then travel around the body into various organs.
Studies have found microplastics in human
faeces, joints, livers, reproductive organs, blood, vessels and hearts.
Microplastics also migrate to the brains
of wild fish. In mouse studies, ingested microplastics are absorbed from the
gut into the blood and can enter the brain, becoming lodged in other organs
along the way.
To get into brain tissue, microplastics
must cross the blood-brain-barrier, an intricate layer of cells that is
supposed to keep things in the blood from entering the brain.
Although concerning, this is not
surprising, as microplastics must cross similar cell barriers to enter the
urine, testes and placenta, where they have already been found in humans.
Is
this a health concern?
We don't yet know the effects of
microplastics in the human brain. Some laboratory experiments suggest
microplastics increase brain inflammation and cell damage, alter gene
expression and change brain structure.
Aside from the effects of the microplastic
particles themselves, microplastics might also pose risks if they carry
environmental toxins or bacteria into and around the body.
Various plastic chemicals could also leach
out of the microplastics into the body. These include the famous
hormone-disrupting chemicals known as BPAs.
But microplastics and their effects are
difficult to study. In addition to their small size, there are so many
different types of plastics in the environment. More than 13,000 different
chemicals have been identified in plastic products, with more being developed
every year.
Microplastics are also weathered by the
environment and digestive processes, and this is hard to reproduce in the lab.
A goal of our research is to understand
how these factors change the way microplastics behave in the body. We plan to
investigate if improving the integrity of the gut barrier through diet or
probiotics can prevent the uptake of microplastics from the gut into the
bloodstream. This may effectively stop the particles from circulating around
the body and lodging into organs.
How
do I minimise my exposure?
Microplastics are widespread in the
environment, and it's difficult to avoid exposure. We are just beginning to
understand how microplastics can affect our health.
Until we have more scientific evidence, the best thing we can do
is reduce our exposure to plastics where we can and produce less plastic waste,
so less ends up in the environment.
An easy place to start is to avoid foods
and drinks packaged in single-use plastic or reheated in plastic containers. We
can also minimise exposure to synthetic fibres in our home and clothing.
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