The average human brain is so filled with microplastics and nanoplastics (MNPs) that scientists believe the accumulation could be affecting its operation, including increasing the chances of dementia. The same research found that the levels of microplastics and nanoplastics were significantly higher in the brain than in other organs, totaling as much as a plastic spoon.
Although the microplastics and nanoplastics found inside the brain can come from several sources, the researchers say the average person could reduce their exposure to microplastics by as much as 90% by simply eliminating their use of bottled water.
Microplastics and Nanoplastics Are Accumulating at an Alarming Rate
In the 1967 classic The Graduate, Walter Brook’s Mr. McGuire pulls Dustin Hoffman’s character aside to give him one word of advice about the future: plastics! Ranked by the American Film Institute as the 42nd greatest movie quote of all time, nearly six decades later, the words have proven to be more of a warning than the glowing opportunity projected by McGuire.
Since that movie’s release, society has been catching up to the ramifications of engineered materials that can last thousands of years. Recently, accumulated plastic waste in the deepest parts of the Earth’s oceans, including the Mariana Trench, has been discovered, affecting the region’s entire ecosystem.
At the same time, science is increasingly concerned about the health and wellness ramifications of the MNPs. For example, University of Queensland scientists are investigating plastic-eating super worms that can digest Styrofoam and other plastic-based materials and remove them from the environment. University of Waterloo scientists have gone even smaller by engineering bacteria that can break down microplastics.
A team of engineers searching for a non-biological solution created swarms of micro-robots that can hunt down plastics and bacteria contaminating water. University of California, Berkley scientists have developed a new plastic bag that can break down into smaller biodegradable pieces within two weeks.
This latest study adds even more urgency to the battle against MNPs by suggesting that microplastics and nanoplastics may be tiny enough to cross the blood-brain barrier. The researchers say the evidence is compelling, including the potential association between elevated plastic levels in the brain and dementia.
Dramatic Increase in Brain MNP Concentrations
In a peer-reviewed Commentary on the increased levels of MNPs found inside the human brain, lead author Dr. Nicholas Fabiano from the University of Ottawa’s Department of Psychiatry explains that plastic particles smaller than 200 nanometers, predominantly made of polyethylene, are the primary concern. The author also notes that the increase of MNPs in the brain has risen significantly in the last eight years alone.
“The dramatic increase in brain microplastic concentrations over just eight years, from 2016 to 2024, is particularly alarming,” Fabiano writes. “This rise mirrors the exponential increase we’re seeing in environmental microplastic levels.”
According to a statement from the commentary authors, previous research evaluating the concentrations of microplastic particles small enough to potentially influence the functions of the human brain found “notable deposition in cerebrovascular walls and immune cells.” As noted, one study found the levels of MNPs in human brains were roughly the total of a plastic spoon. The same study found that these “alarming” levels were 3-5 times higher in people with documented dementia diagnoses. Perhaps more surprisingly, human brain tissues showed 7-30 times higher concentrations of MNPs than organs known for their filtration roles, such as the liver or kidney.
What to Do? Stop Drinking Bottled Water
After documenting the studies showing elevated levels of MNPs in the human brain, the commentary authors offered several practical suggestions for individuals looking to reduce their plastic exposure. Perhaps the most significant step highlighted by the authors is eliminating drinking water from plastic bottles. This simple step could mitigate microplastic intake from 90,000 to 4,000 particles per year.
“Bottled water alone can expose people to nearly as many microplastic particles annually as all ingested and inhaled sources combined,” says Dr. Brandon Luu, an Internal Medicine Resident at the University of Toronto quoted in the statement. “Switching to tap water could reduce this exposure by almost 90%, making it one of the simplest ways to cut down on microplastic intake.”
The authors also highlighted several other strategies for reducing MNP intake. For example, tea bags that contain plastics can release millions of particles in one brewing session. Another suggestion involved the best methods for storing and reheating leftovers.
“Heating food in plastic containers—especially in the microwave—can release substantial amounts of microplastics and nanoplastics,” Luu explains. “Avoiding plastic food storage and using glass or stainless-steel alternatives is a small but meaningful step in limiting exposure.”
Still, Luu cautions that the results of these measures have not been tested, and “we still need research to confirm whether lowering intake leads to reduced accumulation in human tissues.”
More Study Needed to Confirm Dose-Response Relationships
Moving forward, the authors recommend “urgent research priorities,” including establishing “clear exposure limits” similar to those regulating other toxic substances. They also note that “large-scale human studies” will ultimately be needed to establish “dose-response relationships between microplastic exposure and chronic health outcomes.”
“We need more research to wrap our heads around microplastics—rather than wrapping our brains in them—since this could be one of the biggest environmental storms most people never saw coming,” said Dr. David Puder, host of the Psychiatry & Psychotherapy Podcast.
The peer-reviewed Commentary article, “Human microplastic removal: what does the evidence tell us?” appears online on 4 March 2025 in Brain Medicine.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.