Dementia already affects more than 57 million people worldwide, and the number of individuals diagnosed with Alzheimer’s and Parkinson’s disease is expected to climb significantly in the coming years. Scientists say the possibility that microplastics could worsen or speed up these disorders raises serious public health concerns.

Pharmaceutical scientist Associate Professor Kamal Dua of the University of Technology Sydney estimates that adults consume about 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 chopping boards, drinks in plastic bottles and food grown in contaminated soil, as well as plastic fibers from carpets, dust and synthetic clothing.”

“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.”

Study Identifies Five Pathways of Brain Damage

The findings come from a systematic review published in the journal Molecular and Cellular Biochemistry. The research was carried out through an international collaboration led by scientists from the University of Technology Sydney and Auburn University in the United States.

Researchers identified five key biological pathways that may allow microplastics to harm the brain. These include activating immune cells, increasing oxidative stress, disrupting the blood-brain barrier, interfering with mitochondria, and damaging neurons.

“Microplastics actually weaken the blood-brain barrier, making it leaky. Once that happens, immune cells and inflammatory molecules are activated, which then causes even more damage to the barrier’s cells,” said Associate Professor Dua.

“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,” he said.

Oxidative Stress and Cellular Energy Disruption

According to the researchers, microplastics can drive oxidative stress in two primary ways. They increase levels of “reactive oxygen species,” unstable molecules that can damage cells, while also weakening the body’s antioxidant defenses that normally keep these molecules under control.

“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,” said Associate Professor Dua.

“All these pathways interact with each other to increase damage in the brain.”

The review also describes how microplastics might contribute to specific neurodegenerative diseases. In Alzheimer’s disease, they may promote the buildup of beta-amyloid and tau proteins. In Parkinson’s disease, they could encourage aggregation of α-Synuclein and harm dopaminergic neurons.

Ongoing Research Into Microplastics and Brain Cells

First author UTS Master of Pharmacy student Alexander Chi Wang Siu is a currently working in the lab of Professor Murali Dhanasekaran at Auburn University. He is collaborating with co-authors Associate Professor Dua, Dr. Keshav Raj Paudel, and Distinguished Professor Brian Oliver from UTS to better understand how microplastics affect brain cell function.

Earlier research from UTS has examined how microplastics are inhaled and where they settle in the lungs. Dr. Paudel, a visiting scholar in the UTS Faculty of Engineering, is also studying how inhaled microplastics may affect lung health.

Reducing Microplastic Exposure

Although current evidence suggests microplastics could worsen conditions such as Alzheimer’s and Parkinson’s, the authors emphasize that additional studies are needed to confirm a direct causal link. Even so, they recommend practical steps to reduce everyday exposure.

“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 fibers instead of synthetic ones and eat less processed and packaged foods,” said Dr. Paudel.

The researchers hope their findings will help guide environmental policies aimed at reducing plastic production, improving waste management practices, and lowering the long-term health risks associated with this widespread pollutant.