Microplastics Are Infiltrating Your Brain. What Are The Effects?

Tiny fragments of plastic known as microplastics are being found accumulating in human brains, but specialists say there is still insufficient evidence to determine whether this poses a health risk.

Microplastics - and the even smaller nanoplastics - are now so widespread they have been detected from mountain summits to the deepest oceans, as well as in the air people breathe and the food they eat. Researchers have also identified them throughout the human body, including in lungs, hearts and placentas, and even in particles capable of crossing the blood-brain barrier.

This growing ubiquity has become a central concern as countries attempt to finalise the world’s first plastic pollution treaty, with the latest round of UN negotiations due to take place in Geneva next week.

Microplastics in human brains: what the leading study reported

The health impacts of microplastics and nanoplastics are still not fully understood, but scientists are trying to clarify the risks in what remains a relatively new area of research.

The most high-profile study examining microplastics in human brains appeared in Nature Medicine in February.

In that research, scientists analysed brain tissue from 28 people who died in 2016 and 24 people who died last year in the US state of New Mexico. They reported that the amount of microplastics found in the samples rose over time.

The findings attracted global attention after the lead author, US toxicologist Matthew Campen, told reporters they had found the equivalent of a plastic spoon’s worth of microplastics in the brain.

Campen also told Nature that he estimated the team could isolate around 10 grams of plastic from a donated human brain - comparing that quantity to an unused crayon.

Speculation 'far beyond the evidence'

Following publication, other researchers have advised against drawing strong conclusions from what was a small study.

"While this is an interesting finding, it should be interpreted cautiously pending independent verification," toxicologist Theodore Henry of Scotland’s Heriot-Watt University told AFP.

"Currently, the speculation about the potential effects of plastic particles on health go far beyond the evidence," he added.

Oliver Jones, a chemistry professor at Australia’s RMIT University, told AFP there was "not enough data to make firm conclusions on the occurrence of microplastics in New Mexico, let alone globally".

Jones also said it was "rather unlikely" that brains could contain more microplastics than have been measured in raw sewage - as the researchers had estimated.

He further noted that the people whose tissue was analysed were healthy prior to death, and that the authors themselves said there was not enough information to demonstrate that microplastics were causing harm.

"If (and it is a big if in my view) there are microplastics in our brains, there is as yet no evidence of harm," Jones added.

The neuroscience news site The Transmitter has also reported that the study included duplicated images, although experts said this did not change its principal findings.

'Cannot wait for complete data'

Much of what is currently known about potential health effects comes from observational research, which cannot prove cause and effect.

One example, published in the New England Journal of Medicine last year, reported that microplastics accumulating in blood vessels were associated with a higher risk of heart attack, stroke and death among patients with an artery-clogging disease.

Researchers have also run experiments in mice, including a study published in Science Advances in January that detected microplastics in their brains.

The Chinese team said microplastics can trigger rare blood clots in mice brains by blocking cells - while stressing that small mammals differ greatly from humans.

A World Health Organization review in 2022 concluded that the "evidence is insufficient to determine risks to human health" from microplastics.

Even so, many health specialists have pointed to the precautionary principle, arguing that the potential threat from microplastics warrants action now.

A report released this week by the Barcelona Institute for Global Health, published ahead of the treaty talks, said that "policy decisions cannot wait for complete data".

"By acting now to limit exposure, improve risk assessment methodologies, and prioritise vulnerable populations, we can address this pressing issue before it escalates into a broader public health crisis," it added.

Global plastic production has doubled since 2000 - and is projected to triple from today’s levels by 2060.

© Agence France-Presse