Microplastics may play a role in worsening neurodegenerative diseases such as Alzheimer's and Parkinson's, according to new research that outlines five mechanisms by which these particles can harm the brain.
The study, published in Molecular and Cellular Biochemistry, was led by researchers from the University of Technology Sydney (UTS) and Auburn University. It reviews evidence showing how microplastics trigger inflammation and damage in the brain.
Associate Professor Kamal Dua, a pharmaceutical scientist at UTS, stated that adults are estimated to consume about 250 grams of microplastics each year. "We ingest microplastics from a wide range of sources including contaminated seafood, salt, processed foods, tea bags, plastic chopping boards, drinks in plastic bottles and food grown in contaminated soil, as well as plastic fibres from carpets, dust and synthetic clothing," said Dua.
"Common plastics include polyethylene, polypropylene, polystyrene and polyethylene terephthalate or PET. The majority of these microplastics are cleared from our bodies, however studies show they do accumulate in our organs, including our brains."
The review identifies five main pathways through which microplastics can cause harm: triggering immune cell activity; generating oxidative stress; disrupting the blood–brain barrier; impairing mitochondria; and damaging neurons.
"The body treats microplastics as foreign intruders, which prompts the brain's immune cells to attack them. When the brain is stressed by factors like toxins or environmental pollutants this also causes oxidative stress," Dua explained.
Microplastics contribute to oxidative stress by increasing reactive oxygen species—unstable molecules that can damage cells—and weakening antioxidant systems that usually control those molecules.
"Microplastics also interfere with the way mitochondria produce energy, reducing the supply of ATP, or adenosine triphosphate, which is the fuel cells need to function. This energy shortfall weakens neuron activity and can ultimately damage brain cells," Dua added.
"All these pathways interact with each other to increase damage in the brain."
The paper further discusses specific ways microplastics could be involved in Alzheimer's disease—such as promoting buildup of beta-amyloid and tau proteins—and Parkinson's disease by contributing to aggregation of α-Synuclein and injury to dopaminergic neurons.
First author Alexander Chi Wang Siu is currently working at Auburn University under Professor Murali Dhanasekaran. The research team includes Associate Professor Dua; Dr Keshav Raj Paudel; and Distinguished Professor Brian Oliver from UTS. Their ongoing work aims to clarify how microplastics affect brain cell function.
Earlier UTS research investigated how inhaled microplastics deposit in lungs. Dr Paudel is now studying their effects on lung health as well.
Although current evidence points toward possible links between microplastic exposure and worsening neurological diseases like Alzheimer's and Parkinson's, researchers say more studies are needed for direct proof. In the meantime, they advise people to reduce their exposure where possible.
"We need to change our habits and use less plastic. Steer clear of plastic containers and plastic cutting boards, don't use the dryer, choose natural fibres instead of synthetic ones and eat less processed and packaged foods," said Dr Paudel.
The authors hope their findings will inform policies aimed at reducing plastic production and improving waste management to lower public health risks associated with environmental pollution from plastics.
