Dublin-based scientists examined how mitochondria are affected by plastic
Minuscule pieces of waste plastic, thousands of times smaller than a human hair, can damage our brains and may be contributing to the increasing global levels of Alzheimer's and Parkinson's disease.
That's according to a new Trinity College Dublin (TCD) study, led by Associate Professor of Biochemistry Gavin Davey, conceived of by student Devin Seward and published in the Journal of Hazardous Materials: Plastics.
The numbers worldwide with Alzheimer's and other dementias increased by about 148 per cent from 1990 to 2019. Much of this rise has been attributed to ageing global populations and genes, but there is growing evidence that environmental pollution is a factor.
"Plastic has only been around for 60 or 70 years, but we've seen a dramatic increase in neurological diseases that can't be explained by genetics or population growth alone," said Prof Davey.
He decided to look into links between "nano" plastics and Alzheimer's after being approached with a research proposal by Mr Seward, then a TCD undergraduate neuroscience student.
Mr Seward suggested looking at why mitochondria (the essential organelles inside each cell that generate its power) are disrupted by tiny "nanoplastics" shed by plastic cutlery and food packaging.
"Our bodies have about 7kg of mitochondria, and they're crucial for making the energy our brains need," said Prof Davey. "When mitochondria malfunction, it's linked to diseases like Parkinson's, Alzheimer's, epilepsy and schizophrenia."
Using rat brain tissue in the laboratory, the TCD team found that exposure to nanoplastics significantly inhibited the mitochondria's ability to use oxygen and produce energy.
"We were surprised at how potent the effect was," said Prof Davey. "The nanoplastics seemed to target the electron transport chain, a key part of the mitochondria's energy production process."
"This newly discovered mitochondrial mechanism of nanoplastic-induced neurotoxicity may, therefore help to explain why rates of neurodegenerative diseases have risen in recent decades."
Nanoplastics are everywhere: in rivers, seawater and air. People can be exposed to them while cycling in the city, eating food with plastic packaging or even when drinking plastic-bottled water.
People can also be exposed when consuming many types of convenient microwaveable food products. "Heating food in plastic containers is something I'd really advise against," said Prof Davey.
The European Union is introducing directives to reduce the use of plastic in food packaging, but Prof Davey believes more must be done.
"It's difficulty to remove all plastics, but reducing unnecessary packaging is a logical step," Prof Davey said.
Follow-up research will investigate how well different types of nanoplastics cross the blood-brain barrier, he said.
"We want to find out which are the most potent and how we might protect the brain." For now, he said, "restricting exposure is key".