Our Brains Are Now 99.5% Human—And 0.5% Plastic

Researchers at the University of New Mexico have discovered substantial amounts of microplastics – tiny plastic particles less than 5 millimeters in size—in human brain tissue, with concentrations far exceeding levels found in other organs.

The study published in Nature Medicine that analysed the brains from 52 deceased individuals, discovered that the average sample contained approximately 7 grams of microplastics, equivalent to the weight of a plastic spoon.

Co-led by Matthew Campen, Regents’ Professor of Pharmaceutical Sciences at the University of New Mexico in Albuquerque, the study also noted that overall, cadaver brain samples contained seven to 30 times more tiny shards of plastic than kidneys and livers.

‘The concentrations we saw in the brain tissue of normal individuals, who had an average age of around 45 or 50 years old, were 4,800 micrograms per gram, or 0.48 per cent by weight,’ Campen said. ‘Compared to autopsy brain samples from 2016, that’s about 50 per cent higher. That would mean that our brains today are 99.5 per cent brain and the rest is plastic.’

The study also highlighted that individuals diagnosed with dementia had up to ten times more microplastics in their brain tissue compared to those without the condition. However, the research did not establish a direct causal link between microplastic accumulation and dementia.

‘We want to be very cautious in interpreting these results as as the microplastics are very likely elevated because of the disease (dementia), and we do not currently suggest that microplastics could cause the disease,’ Campen told CNN.

Scientists analysed brain tissue samples from 2016 and 2024, identifying and measuring a dozen different polymers. For comparison, researchers also looked at brains from people who died between 1997 and 2013. Polyethylene, commonly used for containers and packaging like cups and bottles, was found to be the most prevalent.

Tiny plastic shards of 200 nanometers or less were discovered in clusters, small enough to potentially breach the blood-brain barrier. ‘That’s roughly the size of two COVID viruses side by side,’ said Campen. However, it remains unclear how these particles were transported into the brain.

Microplastics have been detected in various human organs, including the liver, kidneys, lungs, and even in blood, breast milk, placentas, and bone marrow. The pervasiveness raises concerns about their potential impact on human health. Laboratory studies have indicated that microplastics can cause cell damage, inflammation, and oxidative stress, which are linked to various health issues.

From Meat to Our Brains

While microplastics can be ingested, inhaled, or absorbed through the skin, scientists suspect that food, particularly meat, is the primary source of exposure. Irrigating fields with plastic-contaminated water likely leads to the buildup of plastics in crops, which are then consumed by livestock, allowing microplastics to accumulate in animal tissue.

Once ingested, microplastics can accumulate in the tissues of livestock, leading to their presence in meat products consumed by humans. A recent study found microplastics in 88 per cent of protein-rich food samples, including seafood, pork, beef, chicken, tofu, and even plant-based meat alternatives. The discovery of significant plastic levels in store-bought meat adds weight to the theory that our diet plays a key role in microplastic exposure.

Use less plastic

While completely avoiding plastic in today’s world is nearly impossible, experts emphasise that small, mindful choices can significantly reduce both personal exposure and environmental impact.

Pediatrician and biology professor Dr. Philip Landrigan, director of the Program for Global Public Health and the Common Good and the Global Observatory on Planetary Health at Boston College, stresses the importance of a balanced approach. ‘The science around plastics is still evolving, and no one in 2025 is going to live without plastic,’ he says. ‘It’s not about eliminating plastic entirely – it’s about reducing what you can, especially single-use plastics.’

One simple way to minimise exposure is by removing food from plastic containers before heating or microwaving. Heat accelerates the release of microplastics into food, increasing the potential for ingestion.

Avoiding plastic where possible in daily routines can also make a difference. Instead of accepting plastic garment covers from the dry cleaner, using a zippered fabric bag offers a reusable alternative. Bringing a travel mug for coffee and using non-plastic utensils at work helps reduce dependence on disposable plastics. Choosing glass or stainless steel containers instead of plastic for food storage further limits exposure.

While plastics are deeply embedded in modern life, from electronics to food packaging, being mindful of how and where they enter daily routines can help reduce long-term exposure. Cutting back on plastic waste is not only a personal health decision but also a step toward a more sustainable future.

‘Don’t use plastic bags when you go shopping. Use a cloth bag or a paper bag or a recycle bag. Try to avoid plastic water bottles, if you can possibly do so,’ Landrigan said.

A March 2024 study found 1 liter of bottled water — the equivalent of two standard-size bottled waters typically purchased by consumers — contained an average of 240,000 plastic particles from seven types of plastics. Some 90 per cent of those were nanoplastics meaning the vast majority of plastic contamination in bottled water is at a size invisible to the naked eye.

Campen believes these findings should raise awareness of the worldwide threat posed by microplastics, stating, ‘I have yet to encounter a single human being who says, “There’s a bunch of plastic in my brain and I’m totally cool with that.”‘