Scientists have discovered that "acute exposure" to microplastics — tiny bits of plastic material that are now pretty much everywhere, from remote Antarctic ice to human lungs, breastmilk, and bloodstreams — causes dementia-like symptoms in mice, among other behavioral shifts.
The study, published this month in the Internal Journal of Molecular Sciences, is troubling. Microplastics are increasingly omnipresent in our world, and continue to be discovered in previously unthinkable places. And while intuitive logic would lend itself to the notion that a buildup of infinitesimal plastic specks probably wouldn't be good for human and animal health, this new study's findings offer a disturbing glimpse into just how bad microplastics might just be for us and our animal friends.
"Current research suggests that these microplastics are transported throughout the environment and can accumulate in human tissues," study leader Jaime Ross, assistant professor of biomedical and pharmaceutical sciences at the University of Rhode Island's Ryan Institute for Neuroscience and the College of Pharmacy, said in a statement. "However, research on the health effects of microplastics, especially in mammals, is still very limited."
"This," Ross added, "has led our group to explore the biological and cognitive consequences of exposure to microplastics."
Over the course of three weeks, Ross and her team exposed a cohort of young mice and older mice to microplastics via drinking water. After that three-week period was complete, behavioral testing began, with the scientists ultimately finding that all the mice studied expressed some type of strange change not dissimilar to dementia symptoms in humans. Ominously, the results were particularly strong in older mice.
"To us, this was striking," Ross said in her statement. "These were not high doses of microplastics, but in only a short period of time, we saw these changes."
"Nobody really understands the life cycle of these microplastics in the body, so part of what we want to address is the question of what happens as you get older," the scientist added. "Are you more susceptible to systemic inflammation from these microplastics as you age? Can your body get rid of them as easily? Do your cells respond differently to these toxins?"
Perhaps most startling, however, was the scope of bioaccumulation. After dissecting the mice, the researchers found that microscopic plastic bits had worked their way into every major mouse organ, including the brain. That's alarming — after all, it's not like the scientists were directly injecting the plastics with a needle. All the mice needed to do was drink plastic-laced water.
"Given that in this study the microplastics were delivered orally via drinking water, detection in tissues such as the gastrointestinal tract, which is a major part of the digestive system, or in the liver and kidneys was always probable," said Ross. "The detection of microplastics in tissues such as the heart and lungs, however, suggests that the microplastics are going beyond the digestive system and likely undergoing systemic circulation."
"The brain-blood barrier is supposed to be very difficult to permeate. It is a protective mechanism against viruses and bacteria, yet these particles were able to get in there," she continued. "It was actually deep in the brain tissue."
It's still unclear how, exactly, microplastics might be causing these concerning behavioral shifts, and as is always important to remember with animal studies: mice are mice, and humans are humans. Even so, the study's results don't paint a pretty picture of animal health in the age of microplastics, and the researchers believe that the link between the plastics and the rodents' dementia-like symptoms is strong enough to warrant further study.
"We want to understand how plastics may change the ability for the brain to maintain its homeostasis," Ross added, "or how exposure may lead to neurological disorders and diseases, such as Alzheimer's disease."
More on microplastics: Scientists Say New Device Can Scrub 99.9 Percent of Microplastics from Water
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