Tiny plastics in brain, tissues a threat to health

For the first time in January 2025, researchers used real-time imaging to track the movement of tiny plastic particles from the bloodstream into the brains of mice. These particles, absorbed by immune cells, accumulated in brain capillaries, leading to neurological abnormalities. Similar plastic particles have already been found in human kidneys, livers and, most alarmingly, brains, though their full impact on human health remains unclear. Toxicologist Matthew Campen from the University of New Mexico, Albuquerque, estimates that up to 10 grams of plastic could be extracted from a donated human brain.

Classified as microplastics (<5 mm) and nanoplastics (<100 nm), these plastic specks pose a serious threat to human health, potentially disrupting physiological processes across multiple organ systems. Nanoscale plastics can even cross the blood-brain barrier, raising concerns about their neurotoxic effects.

Despite limited research, emerging evidence links these particles to neurological disorders, cardiovascular conditions and mental health issues. Raising awareness and accelerating research into mitigation strategies is more urgent than ever.

Plastic production, which began less than a century ago, continues to soar, surpassing 400 million tonnes annually, with only 9 per cent being recycled. These materials, originating from industrial plastic pellets and the breakdown of larger plastic products, take centuries to degrade, shedding trillions of microplastics and nanoplastics in the process. They are now everywhere —detected in remote islands, deep ocean waters, Antarctic ice, food, drinking water, and even the air we breathe.

Microplastics and nanoplastics in the environment pose toxic threats to living organisms and human exposure to these particles has become inevitable. They have been found in human faeces and vital tissues, including the liver, kidneys, placenta and bloodstream. Their accumulation has been linked to chronic conditions, such as respiratory disorders, immune dysfunction, hormonal imbalances and metabolic diseases.

Plastics enter the human body through multiple pathways: via seafood and packaged foods, through inhalation into the respiratory system and even directly into the bloodstream through plastic-based medical devices. Once inside, microplastics travel through the bloodstream and accumulate in vital organs, posing serious health risks.

Detecting microplastics and understanding their health effects is challenging due to their varied sizes, shapes and compositions. Many are coated with chemical additives designed to enhance flexibility, flame resistance or degradation.

The severity of their impact depends on the dose and route of exposure. Inhaled plastics can trigger inflammatory reactions in the lungs, potentially leading to long-term respiratory issues. The smallest particles are of particular concern as they can infiltrate cells with no known mechanisms for removal.

Laboratory studies show that exposure to microplastics in human tissue samples can lead to cell death, immune responses and tissue damage. Emerging evidence also suggests links to heart disease, kidney disease, cancer, Alzheimer's and fertility issues.

While direct human evidence is still developing, research increasingly connects microplastics to cardiovascular diseases. Individuals with plastic particles in their arteries may face a higher risk of heart attacks, strokes and premature death.

A 2024 study found that nearly 60 per cent of 250 heart surgery patients had microplastics or nanoplastics in their main arteries. These individuals were 4.5 times more likely to suffer heart attacks, strokes or death within three years of a surgery compared to those without detectable plastic particles in their arteries.

Recent research has tracked how plastic particles travel through the bodies of mice after they had consumed water containing fluorescent polystyrene particles, widely used in food packaging, disposable cutlery and toys. Within three hours, these particles were absorbed by immune cells and some of these migrated to the brain cortex, where they remained lodged for up to four weeks. When introduced directly into the bloodstream, plastic particles infiltrated the brain within minutes.

Accumulated plastic particles in brain capillaries can impair blood flow, reducing oxygen supply to neurons, potentially contributing to cognitive dysfunction and neurological damage. Nano-sized plastics are particularly concerning because they are small enough to cross the blood-brain barrier, one of the body's most protective shields. Researchers suspect they may contribute to neurodegenerative diseases like Parkinson's and Alzheimer's by triggering oxidative stress, inflammation and protein misfolding in brain cells.

Investigation into the neurological effects of microplastics suggests that they break down into nanoplastics inside the body, increasing the likelihood of their accumulation in the brain and interfering with neural activity. Microplastics may also indirectly impair brain function by inducing chronic inflammation in peripheral tissues.

A 2024 study found that brain samples contained 50 per cent more microplastics than those analysed in 2016, with plastic concentrations in the brain up to 30 times higher than in the liver and kidneys. This suggests that despite its protective barriers, the brain may be particularly vulnerable to plastic accumulation.

Growing information also links chronic plastic exposure to behavioural changes in animals. If similar effects occur in humans, long-term exposure could have profound consequences for mental health and cognitive longevity.

With plastic particles detected in human brains at alarming levels, their potential impact on cognitive health warrants intensive study. Efforts to tackle this crisis suffered a setback as world leaders failed to reach a consensus on a plastic treaty at the December 2024 Busan summit.

Meanwhile, plastic production is expected to double by 2040, further escalating environmental contamination and human exposure.

Thus, urgent action is required, including stricter regulations to limit plastic production and waste; greater public awareness of plastic-related health risks; a drastic reduction in single-use plastics; investment in sustainable, biodegradable alternatives; and intensive research on microplastics' long-term effects and mitigation strategies.

The presence of plastic in the human brain is no longer a distant concern. We must confront this crisis with top priority to safeguard human health and our planet.