When a CBS News medical correspondent claimed last week that humans are accumulating a plastic spoon’s worth of plastic in their brains, her colleagues looked horrified, and for good reason. Surely, that much plastic would gunk up our cognitive machinery.
You probably do not have quite that much of the stuff in your brain, but the idea of any plastic piling up there is still unnerving.
The correspondent was referring to a new study of the amount of plastic our bodies absorb. Researchers from the University of New Mexico and other institutions examined organs collected from autopsies of 91 people who died over the past quarter century. The scientists tested small samples from different organs, including the brain, liver and kidneys, to measure the amount of plastic present.
Illustration: Yusha
The results, published in the journal Nature Medicine earlier this month, concluded that plastic is lodged primarily in our brains.
It is well known that we eat, drink and breathe billions of invisibly small particles of plastic every day. Still, until now, scientists have not known whether these micro and nanoplastics move through our bodies or build up and where they might collect over time.
In the most extreme case, the researchers estimated the brain was 0.48 percent plastic, meaning the particles added up to a couple of grams — the weight of a typical plastic spoon. The average brain studied showed about a tenth of that amount, and some samples carried nearly undetectable quantities.
Adding to the fear factor was the observation that the most contaminated brains belonged to people who had died from Alzheimer’s disease. While plastic particles might play a role in causing dementia, it is also possible that they are a symptom and that the brains of people with Alzheimer’s lose the ability to block foreign matter or expel it once it is there.
One of the study’s authors, neurologist Andrew West of Duke University, said that it is not necessarily a one-way street: These tiny particles can get out of the brain and in, but in some cases, the particles enter faster than the brain can clear them. (Scientists recently discovered how the brain uses cerebrospinal fluid to flush away waste, mostly during sleep.) Once scientists understand the most prevalent routes of nanoplastic exposure, we might be able to avoid more buildup or even speed up the clearing process.
Invisibly small bits of plastic can enter our bodies through plastic bottles and food wrappings, as well as the things we eat and drink — meat, seafood, beer, salt, tap water — and the air we breathe.
In 2016, humans had already discarded enough plastic to wrap the entire Earth in cling wrap, and in the intervening years, that number has increased by about 50 percent. People used to worry about the plastic trash they could see, but we have now found that plastic breaks down into particles as small as bacteria and viruses.
This latest study found plastic particles in all the organs examined, but the highest concentrations were in the subjects’ brains. West said that these nanoplastic particles are likely lipophilic, clinging to the fats that comprise about 60 percent of our brains.
The highest concentrations were found in the brains of the most recent deceased, which probably reflects the increased amount of plastic in the environment. Those who died at the oldest ages carried less, which is why West and others say this is probably not a one-way accumulation over time.
There was also something surprising about the kinds of plastic that turned up in the study, said Mark Jones, a retired chemist who has been studying nanoplastics, but was not part of this research.
Scientists found lots of polyethylene, which comes from items like plastic milk jugs, freezer bags and food wrappings, but there was almost no polyethylene terephthalate (PET) — the plastic used to make soda and water bottles. Previous studies showed that soda and water containers can shed hundreds of thousands of nanoparticles. PET particles appear in human blood, so it is surprising they were missing in this study.
Jones said that these curious results warrant more study. That is the way science works. This paper was the first of its kind — not the last word, and there is much more uncertainty than was reflected in the alarming headlines.
He also took issue with the misleading images in the media showing multi-colored particles far larger than the microscopic ones found in the organs studied.
Still, discovering a reservoir for plastic in the brain is an important finding, even if the study did not show how it might impact health, he said.
Reacting to the CBS News story, Jones said the report offered reasonable advice to those wanting to avoid at least some of the plastic particles people are exposed to. That includes not microwaving food in plastic containers and using glass or stainless-steel reusable water bottles rather than disposable plastic ones.
More studies are needed to determine the particles’ health effects and confirm the extent of accumulation found in this study. Previous evidence has shown that ingested plastic also collects in our cardiovascular system.
A study published last year in the New England Journal of Medicine used samples from 300 people having plaques removed from their carotid arteries. About half the plaques contained plastic particles. Researchers found those patients were more likely to experience strokes and heart attacks.
At the same time, heart disease rates have been declining since the 1960s, even as people are exposed to more plastic.
Some studies have linked chronic brain inflammation to Alzheimer’s disease. While some researchers are looking at viral infections as a trigger for brain inflammation, there has not been much study of the effects of plastic particles.
This is just the kind of environmental health risk that the “make America healthy again” campaign proposed by US Health and Human Services Secretary Robert F Kennedy Jr promises to fight.
However, it might be impossible to conduct the necessary research given the recent gutting of US federal resources for science.
If funding can be found, West said there is no shortage of students eager to work on this problem since they inherit an increasingly contaminated world.
F.D. Flam is a Bloomberg Opinion columnist covering science. She is host of the Follow the Science podcast. This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
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