The amount of microplastics in the human brain appears to have increased significantly over the past decade, with concentrations rising by roughly 50% between 2016 and 2024, according to a new study published in Nature Medicine.

Researchers found that brain tissue contained substantially higher levels of microplastics and nanoplastics than liver and kidney tissue. The study also found higher concentrations in the brains of deceased people diagnosed with dementia, although it does not establish that microplastics cause dementia.

Microplastics and nanoplastics are tiny plastic particles produced as larger plastic products such as packaging, containers, clothing and tyres break down. They have been detected in several parts of the human body, including the blood, lungs and placenta.

For the study, researchers examined brain, liver and kidney tissue from people who died in 2016 and 2024. They also analysed brain tissue from people who died between 1997 and 2013.

The researchers found that the brain samples collected in 2024 contained much higher levels of microplastics than those collected in 2016. The increase remained consistent regardless of the participants’ age, sex, race, ethnicity or cause of death.

The findings suggest that microplastic concentrations in the brain have increased by around 50% in eight years, which researchers say could reflect the growing amount of plastic pollution and human exposure to these particles.

“We think [the increase] is simply mirroring the environmental buildup and exposure,” study co-author Matthew Campen, a toxicologist at the University of New Mexico, told National Geographic.

The study found that microplastic levels in the examined brain tissue were seven to 30 times higher than those found in liver and kidney samples.

Researchers also found three to five times more microplastics in the brains of people diagnosed with dementia than in cognitively normal brains. However, they stressed that the finding represents an association, not evidence of cause and effect.

It remains unclear whether microplastics contribute to dementia or whether changes caused by dementia make it easier for the particles to accumulate in the brain.

The researchers also found that the particles were predominantly thin, sharp fragments rather than the smooth, bead-like particles they had expected.

Scientists are still trying to determine how microplastics and nanoplastics enter the brain. One possibility is that the particles may travel through the body alongside fats, which are readily transported to the brain. Researchers also believe some particles may cross the blood-brain barrier.

The potential health effects of microplastics remain poorly understood. However, previous research has linked higher concentrations of microplastics in arteries with increased risks of heart attacks, stroke and death.

The new findings raise further questions about the long-term effects of plastic exposure, particularly as microplastics have now been detected deep within the human brain.

Researchers say future studies will need to determine how the particles reach the brain and whether their presence has any measurable effects on brain health. In the meantime, scientists have called for measures to reduce exposure to microplastics.

“We don’t know that much about the health effects, but the fact is that [microplastics] are [in the brain] and they shouldn’t be there, and maybe that’s worrying enough,” Emma Kasteel, a neurotoxicologist at Utrecht University who was not involved in the study, told National Geographic.