Microplastics may disrupt brain processes linked to Parkinson’s, with a review suggesting pollution could play a part in rising cases.
Cases of Parkinson’s have doubled over the past 25 years, and researchers said rising levels of plastic pollution in the environment may be partly responsible.
The review drew on more than 100 earlier studies, including animal research, laboratory experiments and computational models, and set out what the authors described as evidence linking tiny plastic particles to the neurodegenerative condition.
While it is not yet clear that microplastics are directly responsible, researchers from Gannan Medical University and Guangzhou Medical University in China looked at how microplastics, defined as fragments smaller than 5 millimetres, and nanoplastics, which are smaller than a micrometre, enter the body through food, drink, air and skin contact.
Once inside the body, the fragments can cross the blood-brain barrier, a protective layer that helps stop harmful substances reaching the brain, or enter through nerve cells lining the nasal cavity.
The review points to evidence that these particles may encourage the build-up of toxic clumps of alpha-synuclein, a protein closely linked to Parkinson’s.
Researchers also found that plastic fragments could trigger neuroinflammation, meaning harmful inflammation in the brain, disrupt communication between the brain and the gut, and carry damaging metals into the brain through ferroptosis, a type of cell death caused by iron build-up.
All of these forms of damage have previously been linked to Parkinson’s disease.
However, the authors said current research is “significantly limited” and that the chronic effects of human exposure and toxicity “remain incompletely characterised.”
Most of the studies in the review were based on animal testing or experiments on cells in a laboratory, rather than human subjects.
“With the intensification of global plastic pollution, the potential threats posed by micro- and nanoplastics to human health have become a major concern,” the researchers wrote.
The researchers called for greater efforts to reduce plastic pollution, improve waste management and develop biodegradable alternatives to plastics used in everyday life.
It is not only the brain where microplastics and nanoplastics may pose a threat.
Other research has linked the pollutants to fertility problems, antimicrobial resistance, cardiovascular issues and more, although some scientists have cautioned that contamination and false positives remain too common in this field.
The researchers said: “Future research must systematically compare how micro- and nanoplastic properties, including size, shape, surface charge, polymer type, and degradation state, influence Parkinson’s disease-related pathways.”
