Plastic is everywhere. It is in our oceans, our food, our clothes, and now, it seems, in our brains. Recent research suggests that the average human brain may contain around seven grams of plastic. That is roughly the weight of two bottle caps. But it is not just the quantity that concerns scientists. It is what these plastic fragments might be doing once they are inside the brain.
Microplastics, which are particles smaller than five millimetres, and even smaller nanoplastics, can now be found in virtually every environment on Earth. They are also present in our food and drinking water, and we inhale them daily. Scientists have now shown that these particles can cross the blood brain barrier and accumulate in brain tissue.
What happens when plastics reach the brain?
Animal studies provide some of the clearest clues. Mice that ingest microplastics become more forgetful and less sociable. Fish exposed to the particles appear anxious and disoriented. Hermit crabs, when given a choice between a better and a worse shell, often choose poorly after ingesting microplastics. Bees that consume plastic-contaminated nectar forget which flowers provide food.
Mechanistically, several processes seem to be involved. One is neuroinflammation. When plastic particles enter the brain, microglia, the brain’s resident immune cells, attempt to remove them. But this triggers swelling and inflammatory responses that can damage surrounding neurons. In some cases, microglia even obstruct local blood flow. These effects mimic patterns seen in early neurodegenerative diseases.
Another concern is interference with neurotransmission. In rodents, microplastics have been shown to reduce levels of acetylcholine, which is critical for memory and learning, and oxytocin, which plays a role in social behaviour and bonding.
Indirect routes: the gut brain axis
Microplastics may also affect the brain without ever entering it. Evidence suggests they disrupt the gut microbiome and the signalling between the gut and brain. In animals, this is associated with reduced short term memory, lower sociability, and increased anxiety-like behaviours. The disruption of the microbiota may also increase gut permeability, allowing more plastic fragments or associated chemicals into the bloodstream.
What about humans?
Direct evidence in humans is still limited. However, a 2024 study analysing post mortem human brain tissue found widespread microplastic contamination, with levels higher in people who died in 2024 compared to those from 2016. Another study found that older adults in China who frequently used plastic tableware had a higher risk of mild cognitive impairment. People diagnosed with dementia also had more plastic fragments in their brains than controls.
It is too early to draw firm conclusions, but the parallels with animal studies are striking.
Can anything be done?
While more research is needed, there are plausible ways to reduce exposure and potential harm:
Avoid heating food in plastic containers Use glass, ceramic, or stainless steel for storage and drinking Reduce consumption of processed and packaged foods Support gut health through a diverse diet rich in fibre and polyphenols Preliminary animal studies suggest probiotics and vitamin E may reduce some of the harm
Final thoughts
Plastic pollution is not just an environmental issue. It is increasingly a biological one. Although the effects in humans are not yet fully understood, the early signals from animal research are difficult to ignore. We are still learning what it means to live in a world saturated with plastic, but if the brain is being affected, then the stakes are considerably higher than previously assumed.
My Wellness Doctor
My Wellness Doctor 
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