Microplastics can disrupt brain processes associated with Parkinson’s disease, and some research suggests pollution may be contributing to the rise in cases.
Cases of Parkinson’s disease have doubled in the past 25 years, and researchers said rising levels of plastic pollution in the environment may be partially to blame.
The review drew on more than 100 previous studies, including animal studies, laboratory experiments, and computational models, and uncovered what the authors described as evidence linking small plastic particles to neurodegenerative conditions.
Although it is not yet clear whether microplastics are directly responsible, researchers from China’s Gannan Medical University and Guangzhou Medical University investigated how microplastics, defined as debris smaller than 5 millimeters, and nanoplastics smaller than 1 micrometer, enter the body through contact with food, drink, air, and skin.
Once inside the body, debris can cross the blood-brain barrier (a protective layer that prevents harmful substances from reaching the brain) or enter the nerve cells lining the nasal passages.
The review points to evidence that these particles can promote the accumulation of toxic clumps of alpha-synuclein, a protein closely associated with Parkinson’s disease.
Researchers also found that plastic debris can cause neuroinflammation, meaning harmful inflammation in the brain, disrupt communication between the brain and gut, and transport harmful metals into the brain through ferroptosis, a type of cell death caused by iron buildup.
All of these forms of damage have previously been associated with Parkinson’s disease.
However, the authors said current research is “significantly limited” and the chronic effects of human exposure and toxicity “are still not fully understood.”
Most of the studies included in the review are based on animal studies or experiments on cells in the laboratory, rather than on human subjects.
“With the escalation of global plastic pollution, the potential threat posed by micro- and nanoplastics to human health has become a major concern,” the researchers wrote.
The researchers called for further efforts to reduce plastic pollution, improve waste management and develop biodegradable alternatives to plastics used in everyday life.
The brain isn’t the only area where microplastics and nanoplastics can pose a threat.
Other studies have linked contaminants to fertility problems, antimicrobial resistance, cardiovascular problems and more, but some scientists warn that contamination and false positives are still too common in the field.
The researchers said, “Future studies should systematically compare how properties of micro- and nanoplastics, such as size, shape, surface charge, polymer type, and degradation state, influence Parkinson’s disease-related pathways.”
