We all saw the scary headlines: our brains are full of plastic! Well, microplastics. Ok, well, what are microplastics? And are they anything to worry about?
To answer the first question, microplastics are tiny fragments of plastic less than five mm long. Five millimetres, though, isn’t exactly micro; however, most are micro: invisible to the naked eye and as small as 1.6 micrometres. (Smaller than that are classed as ‘nanoplastics.’)
Approximately 35 per cent of microplastics originate in polyester, acrylic or nylon-based clothing. As the clothes are eroded, often during washing, tiny fragments break off. Others originate in cosmetics, such as facial scrubs, or toothpaste, where they are used as abrasive agents. Particulate pollution from car tyres is another common source. Microplastics commonly enter the body by oral ingestion: from drinking water, bottled water, seafood, salt, sugar, tea bags, milk, etc.
So, how do they impact human health? The short answer is: we just don’t know, though we suspect.
“We start thinking that maybe these plastics obstruct blood flow in capillaries,” [study co-author Matthew Campen, a toxicologist at the University of New Mexico] said in a statement. “There’s the potential that these nanomaterials interfere with the connections between axons [wires] in the brain. They could also be a seed for aggregation of proteins involved in dementia.”
However, for now, “we just don’t know,” Campen said […]
Studies into how microplastics affect human health are still scant and inconclusive, according to the World Health Organization. So far, some types of plastic are thought to be harmless, whereas others, such as polystyrene, have been shown to kill human cells in lab dishes, as well as cause bowel inflammation and reduce fertility in mice.
What did the new study find?
To investigate the prevalence of plastic in our neural tissue, the researchers behind the new study analyzed samples of brain, liver and kidney tissue from 28 people who had died in 2016 and compared them to the brains of 24 people who died in 2024. To extend the analysis, they also compared this brain tissue with older samples gathered between 1997 and 2013, showing a rising trend in microplastics across the years.
The results seemed to suggest that human brains are swimming in plastic shards, with concentrations about seven to 30 times higher than those found in kidney and liver tissue. The plastics primarily existed at a nanoscale, and in healthy brains their numbers were not influenced by the age of the person at death, their cause of death, sex or ethnicity, the researchers found.
The study also found significantly higher concentrations – six times higher – in the brains of an even smaller subsample: eight people who died of dementia. Whether that’s a cause or an effect is not clear:
The researchers note that brain changes associated with dementia would be expected to make it easier for the plastics to accumulate. Thus, at this point, it’s unclear if dementia drove the plastic buildup or if the plastic somehow contributed to the disease itself.
Other scientists, though, are warning to treat the study’s findings with caution. Most notably, they point out that the study didn’t measure the plastics themselves, but secondary compounds. Yet, the very method they used could have caused the brains to spontaneously produce those compounds themselves.
Yet the main analytical method the researchers used (called pyrolysis-gas chromatography-mass spectrometry) causes the abundant fats within the brain to release the same compounds as polyethylene. As this method actually measures these compounds and not the polyethylene directly, this effect could potentially lead to false-positive results.
“I think we need to take the study’s findings with a big pinch of salt,” Oliver Jones, a professor of chemistry at RMIT University in Melbourne who was not involved in the study, told Live Science. “They are reporting higher concentrations of microplastics in the brain than we see in wastewater? That does not seem likely.”
He added, “When you get a result like that, you have to ask yourself questions like, ‘Are you sure you did the analysis right? And are these results biologically plausible?’ I don’t think the answer to either question is yes, myself.”
The researchers counter that other polymers, unaffected by the test method, were also found to be increasing.
However, other statements by Campen – “If our planet is on the second ring of perdition or the seventh, it is clear that we have made some bad decisions” – suggest a clear bias in the research, and might suggest that, rather then ‘pure’ science, the research is assuming a problem – and going looking for confirmation.
Still, that doesn’t mean that, especially with better and more robust techniques, we shouldn’t try to determine if these substances are lodging in our brains. More importantly, what, if anything, they’re doing if they’re there.
