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A new study shows that microplastics have crossed the blood-brain barrier — and that their numbers are rising.
The scientists also examined the brains of 12 deceased patients diagnosed with dementia, and found that they had three to five times more microplastics than normal brains.
“Every time we scratch the surface, it uncovers a whole host of, ‘Oh, is this worse than we thought?’” one of the paper’s lead authors, University of New Mexico toxicology professor Matthew Campen, said in an interview about an earlier version of the paper.
Microplastics are tiny pieces of plastic — less than 5 millimeters in size, or smaller than a pencil eraser — that are either manufactured or slough off of plastic objects. Nanoplastics are even smaller, and can be a fraction of the width of a human hair.
In recent years, scientists have realized that many plastic items (plastic bags, water bottles, tires, polyester or synthetic clothing) can shed small fragments or fibers that make their way into air, food and water. Many of those particles are burrowing deep into the human body. Microplastics have been identified in the liver, placenta, blood, testicles, even certain arteries that lead to the heart.
For the new study, scientists analyzed 52 brain specimens, 28 that were autopsied in 2016 and 24 that were autopsied in 2024. They found microplastics in every sample, but there were significantly higher numbers of microplastics in those from 2024.
Researchers then obtained additional brain samples going back to 1997 and found that they followed the same trend: more recent samples had much higher numbers of microplastics. They found no correlation with how old the person was when they died.
Campen says that, with just a single study, there is reason to be cautious when interpreting the results. But, he added, the amount of plastics produced globally doubles every 10 to 15 years, which suggests that humans’ level of exposure has skyrocketed. “To see it go up 50 percent in eight years in human organs … I think that’s perfectly in line with what we’re seeing in the environment…”