Our brains are accruing as much as a credit card’s worth of plastic, according to a worrying new study.
Researchers at the University of New Mexico examined brain samples from people who died between 2016 and 2024 and measured their plastic content. Other research had already shown, in humans and animals, that microplastics can cross the blood-brain barrier, which is the brain’s only protection against harmful substances and organisms.
The researchers discovered concentrations of plastic that were about 12 times higher than in liver or kidney samples.
They found that levels of plastic in the brain samples increased by 50% in just eight years, and the median weight of plastic in a brain sample from 2024 was 4,917 micrograms per gram, roughly five grams per kilogram. Given that the average brain weighs nearly 1.5 kilograms, that means many brains might contain as much as 7.5g of plastic—the weight of a credit card or more.
Older brain samples, from the period 1997 to 2013, were obtained for comparison, and showed a steady increase in concentrations of plastic that mirrored the global increase in plastic production. Polyethylene, the most commonly produced plastic, accounted for around 75% of all detected plastic, suggesting that exposure derives overwhelmingly from ordinary forms of plastic goods.
The researchers also found clear evidence of a link between dementia and microplastic exposure. The brains of people with dementia contained as much to ten times more microplastic particles than the brains of those without the condition.
More than nine billion tons of plastic are estimated to have been produced between 1950 and 2017, with over half of that total having been produced since 2004. The vast majority of plastic ends up in the environment in one form or another, where it breaks down, through weathering, exposure to UV light and organisms of all kinds, into smaller and smaller pieces—microplastics and then nanoplastics.
Within our homes, microplastics are mainly produced when synthetic fibres from clothes, furnishings and carpets are shed. They accumulate in large quantities in dust and float around in the air, which we then inhale.
If you’re interested in learning more about microplastics, and how you can protect yourself and your loved ones from them, read our detailed primer, “The Microplastic Menace,” here.