Invisible Invaders: The Story of Microplastics Inside Us

As told in a recent article by David Cox on BBC, on a quiet stretch of farmland in Hertfordshire, England, bottles of soil have been sitting on shelves for nearly two centuries. The samples were first collected in 1843 by John Bennet Lawes, a Victorian landowner with a passion for agricultural experiments. He couldn’t have imagined that, decades later, his meticulously preserved soil samples would become a time capsule, not just of farming history, but of a startling new chapter in our planet’s story.

Sometime around the mid-20th century, the soil samples began to change. Mixed in with the grains of dirt were new, synthetic fragments, tiny, colorful specks that had no place in nature. These were microplastics, traces of humanity’s rapidly growing love affair with plastic. As the decades passed, their presence in the soil grew, mirroring the rise of plastic use worldwide.
Today, microplastics are everywhere. They float in the oceans, cling to mountaintops, and drift through the air we breathe. They are buried in Antarctic ice and swallowed by the smallest plankton in the deepest trenches of the sea. And increasingly, even though we cannot see them, they are inside us.

From the Outside World to Our Inner World

Microplastics enter our bodies in ways so ordinary that it’s impossible to avoid them. We drink them in bottled water, sometimes at levels approaching a quarter of a million nanoplastic fragments per liter. We eat them in seafood, salt, fruits, and vegetables, thanks to polluted farmland and ocean waters. We consume them together with our healthiest foods, e.g. fruits and vegetables which are nicely packaged in plastic boxes, and we inhale them from household dust, synthetic clothing fibers, and urban air. I still remember being proud of my t-shirts being made with 20% recycled plastic, not realizing the hidden danger within these textiles.

What is most disturbing is the fact that scientists have found these particles not just in the environment, but in nearly every part of the human body they’ve studied: the blood, lungs, liver, kidneys, testicles, spleen, intestines, breast milk, and even bone tissue.

In 2024, Italian researchers discovered microplastics lodged in plaques inside the carotid arteries, the blood vessels that feed the brain, raising concerns that they could worsen cardiovascular disease. Another team found them in human brain tissue, with dementia patients having up to ten times more plastic in their brains than those without.

The First Human “Plastic Challenge”

Despite these shocking discoveries, no one knows exactly what microplastics do to us. To start answering the question about a causal role of microbes in human health, researchers at Imperial College London recruited eight volunteers for an unusual experiment: they would drink liquids intentionally laced with microplastics, released from commonly used plastic tea bags and microwaved food containers, and have their blood tested over 10 hours. The goal is to see how much plastic makes it into the bloodstream, how quickly, and in what form. The study is still ongoing, and results have not been published.

It has been proposed that microplastics, especially the smallest particles, so called ‘nanoplastics’, may cross from the gut into the blood and then lodge in organs where the body can’t break them down. Over time, this could cause chronic inflammation, scarring, or subtle damage that wears down our health. Even before absorptions, they may be broking down by some of our gut microbes into fragments which can interact with our gut-associated immune system and stimulate an immune response.

Plastic’s Potential Toll

Despite the dramatic increased exposure to microplastics and nanoplastics, no specific disease or health issue has been causally related to their presence in our bodies. The risks scientists are investigating are wide-ranging, including chronic low-grade inflammation increasing the risk for many of our chronic diseases.

Here are a few examples:

In the heart, lodged particles may compromise our microcirculation, increasing stroke and heart attack risk.

In the brain, microplastics and the body’s inflammatory response to them might interfere with nerve cell function and increase the risk for neurodegenerative diseases like dementia or Parkinson’s disease.

It has even been speculated that microplastics in testicles may be one of the reasons contributing to slow sperm count and that the exposure of the fetal brain may increase the risk autism in the offspring.

Despite the ominous findings, scientists are careful not to jump to conclusions. Unlike a toxin with a clear dose–response curve, microplastics are enormously varied in size, shape, and chemistry. One person’s “plastic load” may behave very differently from another’s.

Some scientists are also considering how microplastics might affect the gut microbiome. Particles could physically disrupt the intestinal lining or act as carriers for harmful chemicals that change the microbial ecosystem. Animal studies suggest links to metabolic changes, immune activation, and even “plasticosis”, a scarring disease first described in seabirds.

Not Just a Human Problem

The microplastics inside us start their journey far beyond our kitchens. Sewage sludge used as fertilizer can deposit trillions of plastic particles onto farmland each year. Ubiquitous plastic packaging, synthetic clothing, tire dust, and industrial waste all contribute. Even “biodegradable” plastics can persist for years, breaking into smaller pieces rather than disappearing.

Searching for Solutions

Around the world, researchers are testing creative ways to fight microplastic pollution.

One of the most promising solutions may be plastic-eating microbes and fungi. Certain bacteria can break down plastics into smaller molecules and bioengineered microbes living in our gut are being explored to enhance bacterial capabilities in breaking down plastic. This involves modifying bacteria to produce enzymes that can efficiently degrade complex plastic molecules or polymers, potentially offering a sustainable solution for plastic waste management. Researchers are specifically investigating which enzymes are most effective at degrading different types of plastics and then attempting to introduce these enzymes into bacteria that can thrive in various environmental conditions.

For vulnerable people, like those with asthma, neurodegenerative brain disorders, heart disease, or compromised immune systems, reducing exposure could be particularly important. Studies are underway to test whether microplastic exposure worsens asthma attacks or other chronic conditions, with the hope of eventually guiding product design and public health recommendations.

Experts emphasize that microplastics are not like asbestos or cyanide, they’re unlikely to cause immediate harm. Instead, the concern is about a slow accumulation of damage: low-level inflammation, immune and metabolic stress, or vascular changes that, over decades, might make us more vulnerable to heart disease, neurodegeneration, or other illnesses.

The Take Home Message

We are living in a “plastic age”. From the moment we are born, we’re exposed to tiny synthetic fragments that weave themselves into the fabric of our environment and, increasingly, into our cells, organs and bodies. The science is still catching up and the warning lights have not started flashing, like with climate change or ultraprocessed foods, but the evidence so far suggests that microplastics are not inert passengers, they interact with our tissues, immune systems, and possibly even our brains, and will ultimately take their toll.

The choices we make, about what we consume, how we package our goods, and how we manage waste, will determine not just the health of our planet, but the health of the generations who live on it.