In people aged around 45 to 50, Matthew Campen and his team at the University of New Mexico found an average of 4,900 micrograms of plastic particles per gram of brain tissue—equivalent to roughly 0.5 percent of the tissue’s mass. Extrapolated to the entire brain, that concentration corresponds approximately to the mass of a standard plastic spoon.

The finding is included in a 2026 report by the ALLATRA Global Research Center titled "Nanoplastics. A Systematic Risk Analysis for Human Health, Ecosystems, and the Environment." Seven scientists, including Dr. John Ahn, Dr. Karolína Hronová, and Dr. Anastasiya Pashigreva, systematically reviewed international research literature for the report.

Their analysis found that concentrations of micro- and nanoplastics in the brain were 7 to 30 times higher than in the liver or kidneys. Levels also appear to be rising: brain samples collected in 2024 contained 50 percent more plastic than comparable samples from 2016.

Why the Brain May Accumulate More Plastic Than Other Organs

What many people may not realize is that the brain is composed of roughly 60 percent lipids, or fat-like molecules. These lipids are key components of cell membranes and of the protective sheaths surrounding many nerve fibers. According to the report, this characteristic may make the brain particularly susceptible to the accumulation of nanoplastics.

The explanation lies in the chemistry of the particles. Nanoplastics are hydrophobic, meaning they repel water. Hydrophobic substances tend to associate with lipid-rich environments rather than water. In the body, this means that tiny particles with these properties may preferentially accumulate in tissues with a high lipid content. The brain may therefore provide conditions that favor the accumulation of nanoplastic particles.

According to the report, this process is cumulative. Particle uptake is relatively high, while elimination is extremely limited. Particles that reach the brain may therefore remain there for long periods, allowing concentrations to increase over a lifetime. The authors also cite a mathematical model suggesting that this pattern of accumulation occurs across different biological species, which they argue increases the reliability of projections for humans.

How Nanoplastics Can Damage the Brain’s Protective Barrier

The brain is protected by a biological barrier known as the blood-brain barrier. It can be thought of as a tightly sealed layer of specialized cells lining the blood vessels in the brain. These cells are packed so closely together that very little can pass between them. Substances the brain needs are selectively transported across the barrier, while potentially harmful substances are largely kept out. In this way, the blood-brain barrier helps protect the brain from pathogens, toxins, and other unwanted substances.

According to the report, experimental studies show that polystyrene nanoparticles can damage this protective layer. They affect the proteins that form tight junctions between cells, including ZO-1, occludin, and claudin-5. When these proteins are damaged, the spaces between cells can widen, making the barrier more permeable.

This may set off a chain reaction. Nanoparticles can inhibit autophagy, the cellular recycling process through which damaged components are broken down and removed. If this process is disrupted, iron can accumulate in the cells lining blood vessels. Excess iron can damage cells through oxidative stress, in which reactive oxygen species attack cellular structures. In severe cases, this could contribute to ferroptosis, a form of regulated cell death associated with iron overload and disrupted lipid metabolism.

A second mechanism involves red blood cells. Nanoparticles can damage these cells as they circulate through the bloodstream. Cells in the walls of cerebral blood vessels may then engulf the damaged red blood cells in a process known as erythrophagocytosis. This introduces additional iron into the vascular cells and may further increase cellular damage.

Nanoplastics may therefore affect the blood-brain barrier through two mechanisms: by directly damaging the cells that form the barrier and indirectly by altering red blood cells circulating past them.

How Plastic Particles Could Bypass the Blood-Brain Barrier Altogether

There may also be another route into the brain—one that would not require particles to cross the blood-brain barrier at all.

Researchers examining the olfactory bulbs of 15 deceased individuals detected microplastic particles in 8 of them. The olfactory bulb is a part of the brain located just above the nasal cavity that processes information related to smell. It is connected to the nasal cavity by nerve fibers that pass through the cribriform plate, a thin, perforated section of bone at the base of the skull.

Inhaled plastic particles could potentially use this pathway to travel directly from the nose to the brain without crossing the blood-brain barrier. According to the authors, further research is needed to determine whether—and to what extent—this occurs in living humans. However, the presence of microplastics in the olfactory bulbs suggests that such a route is anatomically possible.

What Nanoplastics Could Do in the Brain

According to the report, once plastic particles enter brain tissue, they can accumulate in both neurons and glial cells. Glial cells are support cells within the nervous system. Among other functions, they provide neurons with nutrients, help establish connections between nerve cells, and regulate inflammatory responses. Glial cells are more numerous than neurons, outnumbering them by an estimated factor of 1.5 to 10. Damage to glial cells can therefore also directly affect neuronal function.

Plastic particles can trigger oxidative stress in both types of cells. This damage may in turn activate microglia, a specialized type of glial cell that serves as part of the brain’s immune defense. Under normal conditions, microglia monitor brain tissue, remove cellular debris, and respond to potential threats. When they detect damage, they become activated.

If the trigger disappears, microglia can return to their resting state. Nanoplastics, however, may persist in the tissue, while continued exposure could introduce additional particles. As a result, microglia could remain activated for prolonged periods.

Over time, an initially protective response could develop into chronic neuroinflammation—a persistent inflammatory state in nervous tissue. This inflammation can damage surrounding neurons, increasing oxidative stress and potentially triggering further microglial activation. According to the report, this could create a self-reinforcing cycle that contributes to the progressive deterioration of nervous tissue.

Diseases Being Studied in This Context

The combination of inflammation, oxidative stress, and progressive cellular damage is also familiar from research into neurodegenerative diseases—conditions in which nerve cells gradually lose function or die.

The report specifically discusses Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). In ALS, the motor neurons that control muscles are progressively lost, eventually affecting movement as well as speech, swallowing, and breathing. In Alzheimer’s disease, cognitive abilities gradually decline, particularly memory and the ability to manage everyday life independently. Many of these conditions progress over long periods, and effective cures are still unavailable in many cases.

According to the report, nanoplastics can trigger several biological processes that are also associated with neurological disease, including oxidative stress, mitochondrial dysfunction, and neuroinflammation. This makes them a potential risk factor, but not a proven cause of disease.

The report also discusses epilepsy and stroke. In epilepsy, damage to neurons can disrupt the brain’s electrical activity. In stroke research, scientists are investigating whether plastic particles could contribute to blockages in the bloodstream and thereby interfere with blood flow to the brain.

What a U.S. Population Study of 218 Coastal Counties Found

A study led by Dr. Sarju Ganatra and presented at the American Academy of Neurology examined whether mechanisms observed in laboratory and animal studies might also be reflected at the population level.

The researchers analyzed health data from the U.S. Centers for Disease Control and Prevention (CDC) across 218 coastal counties and compared the results with regional levels of microplastic pollution.

Residents of areas with high levels of plastic pollution showed higher rates of neurological impairment. Memory and cognitive problems were 9 percent more common, while movement disorders were 6 percent more common.

Difficulties with self-care were reported 16 percent more frequently, and difficulties living independently were 8 percent more common than in areas with lower levels of pollution.

Cardiovascular disease, stroke, and metabolic disorders were also more prevalent in the same areas. The report’s authors emphasize that these findings show a correlation, not a direct cause-and-effect relationship. Other factors may also contribute to the observed differences. Nevertheless, they argue that the statistically significant associations warrant further investigation.

What the Numbers Mean—and What Remains Unknown

Neurological disorders are already the leading cause of physical and cognitive disability worldwide. According to the report, an estimated 3.4 billion people are affected. Their prevalence has increased substantially over the past three decades, and projections cited in the report suggest that the number of people affected could double over the next 20 years.

At the same time as global plastic pollution has increased, the brain samples examined in the research show a marked rise in plastic concentrations: samples from 2024 contained 50 percent more plastic than those from 2016.

Whether—and to what extent—these two trends are connected remains unresolved, according to the authors. Research to date indicates that nanoplastics can reach the brain, accumulate in brain tissue, and trigger cellular processes known to play a role in neurodegeneration.

What has not yet been established is a causal chain linking plastic particles directly to neurological disease in humans. Further research will be needed to determine whether such a relationship exists and, if so, how significant it may be.

Source: DOI: https://doi.org/10.65849/agrc.report.mnp.2026.04001. License: CC BY 4.0.