Microplastics have even been found inside our bones – but what impact are they having on our health? Here's everything we know about what they're doing to our bodies.

A field in a sleepy corner of Hertfordshire, barely an hour's drive north of London, houses the world's longest running agricultural experiments.

Initiated by Victorian aristocrat and landowner John Bennett Lawes, who later became a successful pioneer of modern fertilisers, the aim was to test out various ideas for boosting wheat production. But without the help of modern technology, the only means of storing data was to meticulously collect samples of dried wheat grain, straw and soil from the field and bottle them away.

When it started in 1843, Lawes had little idea that this tradition would endure for another 182 years, creating a remarkable archive of samples. Now housed at the research facility Rothamsted Research, in Harpenden, the collection reflects many of the changes that human activity has inflicted on the planet in the past two centuries.

Andy Macdonald, the current custodian of the archive at Rothamsted Research, affectionately known by colleagues as "Keeper of the Bottles", says that samples collected during the 1940s and '50s contain radioactive traces – reflecting the fallout from the era's nuclear weapons testing. But there's another unwelcome record which can be found in these bottles of ancient soil – the first emergence of microplastics.

According to one famous estimate, we might consume up to 52,000 microplastics per year, and while that precise figure has been subsequently challenged, it's clear that they are entering the human body in significant quantities. Whether ingested through our food, the liquids we drink, or absorbed from the air we breathe, microplastics have become ubiquitous. They have been found in bodily fluids from saliva and blood to sputum and breast milk, along with an array of organs including the liver, kidneys, spleen, brain and even the insides of our bones. This steady convergence of evidence has all pointed to one question – what exactly is all this plastic doing to our health?

In the samples housed at Rothamsted Research, Macdonald says that there's a clear dividing line before and after the plastic era began. "The use of plastics in society first came into being on a large scale in about the 1920s, and we see a big increase from the 1960s onwards," he says. "Some would have inevitably ended up in the soil through atmospheric deposition, and you can also imagine microplastics being shed from tractor tyres."

Today it's thought that around the world, humans are ingesting and inhaling more microplastics than at any time in recorded history. In a study published in 2024, scientists found that consumption of the particles has increased sixfold since 1990, particularly in various global hotspots including the US, China, parts of the Middle East, North Africa and Scandinavia.

But finding out how they are affecting our health has proved tricky. One way to find out is what's known within medical circles as a "human challenge trial". Usually carried out in the realm of infectious diseases, it involves participants agreeing to be deliberately infected with a pathogen in order to help scientists better understand its effects on the human body.

And so, in early 2025, eight brave volunteers entered a lab in central London, and willingly gulped down a solution of microplastics in return for a small fee. This particular study, funded by the Minderoo Foundation, represented the first time that such a challenge trial had been carried out with plastic – though the results haven't been published yet.

The concept, according to Stephanie Wright, a researcher at Imperial College London who led the trial, is that many of us are unwittingly carrying out this exact experiment on our own bodies on a daily basis. The team copied some of the common ways through which many of us ingest microplastics, for example dipping plastic sealed tea bags in hot water or microwaving fluids in a plastic container, before asking the volunteers to drink the liquids and then attempting to follow what happens next.

"We know that heating and hot water are the worst-case scenarios for plastic ingestion, and that can really facilitate the release of microplastics from commonly used plastic items," says Wright. "So we want to take some of these scenarios and try to see how many of these microplastics are actually absorbed across our gut and back into the blood."

To assess this, Wright measured the volunteers' blood at repeated time points over the course of 10 hours. The data, when published later this year, will provide the first concrete information on the typical concentrations of microplastics which end up circulating around our bodies in the wake of a cup of tea or a microwaved ready meal, and their size.

In the eyes of Wright, such information will represent another step on the path to better understanding the potential health risks for the average person.........

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