Researchers in Brazil have found microplastics in human brain tissue, a new study published on Monday in the American Medical Association’s journal JAMA reveals. Microplastics pollution has emerged in recent years as a growing environmental and health concern.
Tiny pieces of plastic measuring between 0.0055 and 0.025 millimeters (0.00021 to 0.00098 of an inch) in size were previously detected in various human tissues and in the bloodstream. Their presence in the brain, however, up until now has remained undocumented, the paper explains.
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A team at Sao Paulo University medical school examined the brains of 15 deceased individuals aged 33 to 100 who had lived in Sao Paulo, the country’s biggest city. Their research ran from February 2023 through to May 2024.
The scientists focused on tissues of the olfactory bulb, a small part of the brain that processes smell. Microplastics were detected in the samples taken from eight of the 15 individuals tested.
A total of 16 synthetic polymer particles and fibers were identified, with polypropylene detected as the most common polymer (43.8%).
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The location in the brain led the researchers to speculate that humans are breathing in the ubiquitous pollutants through their nose.
“Propylene is everywhere, in furniture, rugs, clothes,” lead study author Dr Thais Mauad told NBC News. “We know the place we are most exposed to particles is indoors, because all of our homes are full of plastic.”
Polypropylene is also widely used in food packaging such as bottles, jars, yogurt containers, and hot beverage cups. The breakdown of single-use bottles and packaging creates microplastic particles that consequently find their way into the human body via the digestive tract or by inhaling.
The presence of microplastics in the olfactory bulb means it could be a “potential pathway” for the particles to reach other parts of the brain, researchers also found.
Given “the widespread environmental contamination with plastics,” the findings “should raise concern,” the researchers state, that microplastics could be contributing to the “increasing prevalence of neurodegenerative diseases.”
The first study to estimate human ingestion of plastics, published in 2019, suggested that the average human ingested 50,000 microplastic particles every year.
Another study found that people on average could be ingesting approximately five grams (0.18 oz) of plastic every week, the equivalent in weight of a credit card.