Tiny pieces of plastic, known as microplastics, may contribute to neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. A new study outlines five biological mechanisms by which these particles can cause inflammation and damage in the brain.
Dementia already affects more than 57 million people worldwide, and the number of people diagnosed with Alzheimer’s and Parkinson’s diseases is expected to increase significantly in the coming years. Scientists say microplastics can worsen or accelerate these diseases, raising serious public health concerns.
Associate Professor Kamal Dua, a pharmaceutical scientist at the University of Technology Sydney, estimates that adults consume around 250 grams of microplastics each year, roughly the amount needed to cover a dinner plate.
“We ingest microplastics from a wide range of sources, including contaminated seafood, salt, processed foods, tea bags, plastic cutting boards, bottled drinks, food grown in contaminated soil, and even plastic fibers from carpets, dust, and synthetic fabrics.”
“Common plastics include polyethylene, polypropylene, polystyrene, and polyethylene terephthalate (PET). Although the majority of these microplastics are removed from our bodies, studies have shown that they accumulate in our organs, including the brain.”
Research identifies five pathways of brain injury
The findings come from a systematic review published in the journal Molecular and cellular biochemistry. The research was carried out in an international collaboration led by scientists from the University of Technology Sydney and Auburn University in the US.
Researchers have identified five important biological pathways by which microplastics can harm the brain. These include immune cell activation, increased oxidative stress, disruption of the blood-brain barrier, mitochondrial interference, and neuronal damage.
“Microplastics actually weaken the blood-brain barrier, making it more leaky, which then activates immune cells and inflammatory molecules, causing even more damage to the cells in the barrier,” Dua said.
“The body treats microplastics as foreign invaders, prompting the brain’s immune cells to attack them. When the brain is stressed by factors such as toxins and environmental pollutants, this also causes oxidative stress,” he said.
Oxidative stress and destruction of cellular energy
According to the researchers, microplastics can cause oxidative stress in two main ways. These increase levels of “reactive oxygen species”, unstable molecules that can damage cells, while weakening the body’s antioxidant defenses, which normally keep these molecules under control.
“Microplastics also interfere with the way mitochondria produce energy, reducing the supply of ATP, or adenosine triphosphate, the fuel cells need to function. This lack of energy can weaken neuron activity and ultimately damage brain cells,” Associate Professor Dua said.
“All these pathways interact to increase brain damage.”
This review also discusses how microplastics may contribute to certain neurodegenerative diseases. In Alzheimer’s disease, they can promote the accumulation of beta-amyloid and tau proteins. In Parkinson’s disease, it promotes the aggregation of alpha-synuclein and can damage dopaminergic neurons.
Ongoing research on microplastics and brain cells
First author Alexander Chi Wang Siu, a UTS Master of Pharmacy student, currently works in the lab of Professor Murali Dhanasekaran at Auburn University. He is working with co-authors UTS Associate Professor Dua, Dr Keshav Raj Paudel and Distinguished Professor Brian Oliver to better understand how microplastics affect the function of brain cells.
Previous research by UTS has investigated how microplastics are inhaled and where they settle in the lungs. Dr Paudel, a visiting researcher at UTS’ School of Engineering, is also researching how inhaled microplastics affect lung health.
Reduce exposure to microplastics
Current evidence suggests that microplastics may worsen conditions such as Alzheimer’s and Parkinson’s disease, but the authors stress that additional research is needed to confirm a direct causal relationship. Still, they recommend practical steps to reduce daily exposure.
“We need to change our habits and reduce our use of plastic. Avoid plastic containers and plastic cutting boards, avoid using dryers, choose natural fibers over synthetics, and reduce our intake of processed and packaged foods,” Dr. Paudel said.
Researchers hope their findings will help guide environmental policies aimed at reducing plastic production, improving waste management practices, and reducing long-term health risks associated with this widespread pollutant.
