Microplastics have been found in human blood, organs, and even breast milk. But recent studies have revealed something even more alarming, these tiny plastic particles are now inside our bones. Scientists are racing to understand what this means for our long-term health, and whether our everyday habits are quietly causing damage we can’t yet see.

A field that tells a global story

In a quiet part of Hertfordshire, just an hour north of London, sits a wheat field that has been part of a scientific experiment since 1843. Started by John Bennett Lawes, a Victorian landowner and one of the early pioneers of fertilisers, the field became home to one of the world’s longest-running agricultural studies. Lawes carefully gathered soil, straw and wheat grain each year, drying and bottling them for storage, a tradition that has continued for over 180 years.

Today, these samples are kept at Rothamsted Research in Harpenden. Their custodian, Andy Macdonald, affectionately nicknamed the “Keeper of the Bottles” has studied how changes in the environment have left their mark in these jars of soil and grain. Among the most unsettling discoveries was the appearance of microplastics in samples collected from the mid-20th century onwards, showing the moment plastic pollution began to embed itself into the Earth’s layers.

Macdonald explains that plastics began to enter widespread use in the 1920s, but it was in the 1960s that their presence in the soil sharply increased. Microplastics likely entered the field from the air, or from sources like tyre wear from farm machinery. Today, these plastics are not just in our soil, they are inside our bodies.

Plastic in everything we eat, drink and breathe

An often-quoted study once estimated that we might be consuming as many as 52,000 microplastic particles each year. Though that figure has been questioned, what scientists do agree on is this: plastic is getting into our bodies through the air we breathe, the food we eat, and the water we drink. It’s everywhere from bottled water to salt, vegetables, fish, and even the air inside our homes.Plastic particles have been found in our saliva, blood, lungs, and breast milk, as well as organs such as the liver, spleen, kidneys and brain. A recent discovery added bones to the list. In short, no part of the body appears to be safe from microplastic contamination. And the real concern is just beginning to emerge.

What is all this plastic doing inside us?

A study published in 2024 revealed that the average amount of plastic humans consume has increased sixfold since 1990. The problem is especially intense in places like the United States, China, parts of the Middle East, North Africa and Scandinavia. While scientists are clear that plastic is entering the body, understanding what happens next is far more complex.

The world’s first plastic challenge trial on humans

In an effort to better understand what microplastics are doing inside the human body, a team of researchers in London conducted what’s known as a “human challenge trial”. These trials are usually used for studying diseases – volunteers are exposed to something harmful under careful medical supervision. In this case, it wasn’t a virus, but microplastics.

In early 2025, eight volunteers drank liquids that had been deliberately contaminated with microplastics, mimicking what might happen in a typical household. For example, they simulated drinking hot tea brewed in plastic-sealed teabags or microwaving food in plastic containers. These everyday actions can cause plastic particles to shed into the drink or meal.

Stephanie Wright, a researcher at Imperial College London, led the trial. Speaking to the BBC, she explained that heat and hot water dramatically increase the amount of plastic that is released from common kitchen items. The goal was to track how many of those plastic particles made it from the gut into the bloodstream.

Blood samples were taken from the volunteers over ten hours. The results, expected to be published later this year, will be the first to show how much plastic remains in circulation after an ordinary plastic-exposed meal, and what sizes the particles are. Wright suspects the smallest particles are most likely to reach the bloodstream.

What happens when plastic enters the bloodstream?

Wright says one of the key concerns is whether these plastic particles can build up inside our organs, particularly if the body cannot break them down. Scientists are looking into whether this accumulation might trigger long-term health problems like chronic inflammation, scarring, or reduced organ function.

Already, there are worrying signs. In late 2024, a team of Chinese researchers found microplastics in bones and skeletal muscles of patients who had undergone joint replacement surgeries. They suggested that this could affect physical strength, flexibility, and even someone’s ability to exercise.That same year, an Italian team reported finding microplastics in plaques inside the carotid arteries, the main blood vessels delivering blood to the brain. Over the next three years, those who had microplastics in their arteries were found to be 4.5 times more likely to suffer from heart attacks, strokes or sudden death.

Then, in February 2025, another study uncovered plastic particles in the brains of people who had died. Those who had suffered from dementia had up to ten times more plastic in their brains compared to those without the condition. The lead researcher, Professor Matthew Campen from the University of New Mexico, called the results “shocking”.

Campen believes that the brain’s high fat content may attract plastic particles, especially as plastics can travel using lipids. The fats the brain uses for energy. People with dementia may be particularly vulnerable because their blood-brain barrier, the brain’s protective shield, is often weakened.

Still, scientists like Campen and his Italian colleagues are not claiming that plastic directly causes diseases like dementia or heart problems. Instead, they believe that plastic acts as a burden, working alongside other risk factors to weaken the body over time.

A problem of endless complexity

Professor Fay Couceiro from the University of Portsmouth says microplastics probably don’t act like poisons such as asbestos, which have a clearly defined link to disease. Instead, their danger lies in creating ongoing stress within the body, which might raise the chances of getting sick.

One reason microplastics are so hard to study is because they come in so many forms. A single bottle of water can contain up to 240,000 particles made of several different types of plastic. Some plastics, like nylon or polystyrene, break down into very fine particles called nanoplastics that are small enough to enter individual cells.

These plastics may:

Carry heavy metals and toxic chemicals,

Affect hormone balance,

Trigger inflammation,or even carry genes that make bacteria resistant to antibiotics.

Couceiro is now working on a project in Antarctica, studying wastewater from cruise ships to examine whether microplastics help spread antimicrobial resistance genes. The remote location provides a clean background, helping her identify which plastics are doing the most harm.

Are microplastics speeding up ageing?

Raffaele Marfella, a professor in Naples, believes plastics could be accelerating ageing in the human body. His team has seen signs that microplastics might damage blood vessels, cause low-level inflammation, and disrupt how cells behave. This might lead to long-term problems like tissue damage or even DNA mutations.

In seabirds, such problems have already been observed. The condition, called “plasticosis”, damages organs through long-term plastic exposure. Marfella thinks the same could be happening, slowly and invisibly, in people.

Another researcher, Professor Verena Pichler from the University of Vienna, suspects that plastic may even contribute to rising cancer rates. Microplastics are now routinely found in stool samples, and she believes this may be linked to the growing number of colorectal cancers. Pichler explains that ongoing inflammation caused by plastic might help tumours grow and spread, although this still needs further study.

How microplastics affect those already ill

For people already facing serious health conditions, microplastics may present additional risks. In cancer patients, for example, they might bind with medicines, weakening their effects. Couceiro is also researching how plastic particles affect people with asthma or long-term lung problems.

Her team is analysing mucus samples from patients and monitoring air quality inside their homes. She hopes to discover whether certain plastics are more likely to be linked to asthma attacks, and if so, how to reduce their presence indoors.

Couceiro also points out that many hospital items – like breathing masks and tubes – are made from plastic. If these release microplastics, especially in environments meant for healing, then manufacturers may need to rethink how these products are made.

Where do we go from here Because there are so many types of plastic, and so many ways they interact with the human body, it’s nearly impossible to run enough studies to link specific plastics to specific diseases. Researchers like Wright say this is a major challenge. Unlike smoking, which clearly causes lung cancer, plastic’s effects are slower, more complex, and harder to trace.

Marfella is trying to identify how much plastic the body can tolerate before it becomes dangerous. His team is using artificial blood vessels grown from human cells, and exposing them to different plastic types in various amounts. So far, results from animal tests suggest that even a tiny dose — around 10 to 100 micrograms per kilogram of body weight per day — can trigger inflammation and metabolic changes.

But translating this to humans is tricky, and Couceiro adds that those with weaker immune systems or chronic illnesses may be more vulnerable. Her research continues, with the aim of eventually giving advice to manufacturers and the public on how to reduce exposure to plastic in everyday life.

We are only just beginning to understand how microplastics might be affecting us. They are now a constant presence in the environment — and in our bodies. While the science isn’t yet settled, there is enough concern among researchers to suggest that the plastics we use daily may be slowly damaging our health. The next step, they say, is to identify safer materials and reduce plastic use wherever possible, especially in vulnerable populations.