Should you be worried that your brain probably contains enough plastic to fashion a disposable spoon?
Yes, new research suggests: you should.
In a new study published in the journal Environmental Research Communications, researchers found that mice which were regularly exposed to microplastics in their diet developed symptoms of Alzheimer’s disease, the most common form of dementia, in less than a single month.
The mice were genetically modified to have a gene associated with a higher risk of the neurocognitive disorder. But only the ones that were exposed to the microplastics showed symptoms at such a marked rate.
It’s a startling link between the ubiquitous, tiny sized pollutants and deleterious effects in the brain. Though microplastics are believed to be in the bloodstream of nearly every human, and have been found even in locations as hermetic as the inside of our bones — and of course peppering our mushy gray matter — until now, its effects on our health, if any, have been unclear.
“I’m still really surprised by it,” study coauthor Jaime Ross, a professor of neuroscience at the University of Rhode Island, told the Washington Post. “I just can’t believe that you are exposed to these particles and something like this can happen.”
Scientists still don’t know the underlying cause of Alzheimer’s, making it difficult to draw sweeping conclusions about what plastic particles are doing to provoke its symptoms. On top of that, the gene that the researchers modified the mice to have, APOE4, is one of the strongest risk factors for the disease — but “it doesn’t mean you’re going to develop Alzheimer’s,” Ross told WaPo.
That said, the odds might be stacked against you. Having the variant makes you roughly 3.5 more times likely to develop Alzheimer’s compared to people with the most common gene variant of APOE3, per the newspaper. And having two copies of APOE4 makes it 60 percent likely you’ll have dementia by the age of 85, research has found.
In a series of experiments, the researchers gave the gene-edited mice water mixed with polystyrene, which is the plastic used in styrofoam, over the course of just three weeks. Afterwards, when the mice were put in a square pen, their critter programming went haywire. The male mice kept lingering in the center of the enclosure, instead of sticking to the corners for safety as healthy mice do. And compared to their unexposed counterparts, female mice were far worse at recognizing when a new object was placed in their pen — an unmistakable sign of memory trouble.
Strikingly, this mirrors the gender divide of dementia symptoms in humans.
“There were very similar sex differences in mice as what people experience,” Ross told WaPo. Men with Alzheimer’s tend to display apathy, while women tend to suffer memory loss.
Matthew Campen, a toxicology professor at the University of New Mexico who was one of the first to discover microplastics in the human brain but wasn’t involved in the study, noted that the APOE4 gene affects how certain proteins move fat and other molecules around the body.
“What if APOE4 is just shuttling more plastic from the mouth into the brain?” Campen pondered to WaPo. “Nobody’s really looked at this.”
It’s not the only work to suggest that microplastics, which can easily bypass the blood-brain barrier, could be bad for our cerebrums. One study found that the particles could form blood clots in the brain’s vessels, possibly causing a stroke. In a prelude to the cognitive woes evidenced here, another study which focused on ultra-processed, plastic-packaged junk food linked microplastics with rising rates of depression and dementia. It goes to show how raw this area of research is. And that means we’re only just beginning to grapple with the grim toll of human pollution on our bodies.
More on microplastics: There Is a 100 Percent Chance That Your Body Is Deeply Contaminated With Dangerous Substances