on October 31, 2026
From the environment to the human body
Plastic has become a permanent component of the modern environment. It is present in packaging, everyday objects, textiles, building materials, food containers, and numerous consumer products.
Over time, the wear and degradation of plastic materials produce particles of increasingly smaller sizes: microplastics and nanoplastics.
The health issue is not just about environmental pollution. Research in recent years has shown that plastic particles can be detected in various human biological samples and tissues.
Micro- and nanoplastics have been identified in blood, feces, lungs, placenta, and other tissues. More recent studies have also documented the presence of these particles in the human brain and atherosclerotic plaques.
However, the most important scientific question is not just "where are they found?", but above all: what do they do once they enter the body?
This is a fundamental distinction, because the presence of a particle in a tissue does not automatically prove that the particle caused a disease.
Microplastics and nanoplastics: they are not all the same
The term microplastics encompasses a very broad family of particles.
Their biological characteristics depend on the polymer, size, shape, surface, degree of degradation, and presence of chemical additives.
Nanoplastics represent an even smaller fraction and, precisely because of their size, may have different interaction characteristics with cell membranes and biological barriers compared to larger particles.
This heterogeneity is one of the main difficulties of research.
In fact, there is no single "microplastic": polyethylene, polypropylene, polystyrene, PVC, PET, and other polymers may behave differently in the body.
Furthermore, particles present in the environment can carry or adsorb other chemicals and interact with microorganisms and biological components. The result is a complex exposure, in which it becomes difficult to attribute a specific effect to a single component.
How they enter the body
The main exposure routes considered by research are ingestion and inhalation.
Particles may be present in food, water, and indoor and outdoor environments. Inhalation, on the other hand, can occur through dust and particles suspended in the air.
Skin contact represents another possible route, although its relevance compared to ingestion and inhalation generally appears more difficult to quantify.
Once inside the body, particles can interact with epithelial barriers, immune cells, and the intestinal microbiota.
Their distribution depends on size, shape, composition, and surface characteristics.
Experimental studies indicate that some particles can cross biological barriers and reach systemic circulation. Research in humans is trying to establish how frequently this process occurs and what the long-term consequences are.
The brain: one of the most surprising discoveries
The presence of micro- and nanoplastics in the human brain represents one of the most recent and discussed developments in research.
A study published in 2025 in Nature Medicine analyzed autopsy samples of brain, liver, and kidneys using complementary analytical techniques, including pyrolysis-gas chromatography-mass spectrometry, infrared spectroscopy, and electron microscopy.
Particles were detected in all three organs, with a higher concentration in brain tissue compared to the liver and kidneys. Polyethylene was found to be the predominant polymer.
In brain samples collected in 2024, higher concentrations were detected compared to the 2016 samples, while in samples from people diagnosed with dementia, an even greater presence was observed.
This last result is particularly interesting, but must be interpreted with extreme caution.
In fact, the same study emphasizes that it is not possible to establish a causal relationship between microplastics and dementia. A greater presence of particles could also be influenced by alterations of the blood-brain barrier or elimination mechanisms associated with the disease.
The discovery is therefore important above all because it opens a new question: what are the mechanisms through which particles reach and persist in the brain, and what consequences, if any, do they produce in the long term?
Neuroinflammation and oxidative stress
Once in contact with cells, micro- and nanoplastics can interact with cell membranes, organelles, and signaling systems.
Experimental studies have indicated several possible mechanisms: increased oxidative stress, alteration of mitochondrial function, production of inflammatory mediators, cell membrane alterations, and activation of immune responses.
In the nervous system, these interactions could theoretically contribute to neuroinflammation and the alteration of neuronal homeostasis.
But even in this case, it is necessary to distinguish between a biologically plausible mechanism and a clinically demonstrated disease.
The presence of oxidative stress or inflammatory mediators in an experimental model does not mean that environmental exposure to microplastics automatically causes Alzheimer's, Parkinson's, or stroke.
Research is trying to understand whether and to what extent these mechanisms are relevant in humans.
The placenta: exposure can begin before birth
Another observation that has changed the perspective on the problem concerns the placenta.
Microplastics have been detected in human placenta samples, demonstrating that exposure is not exclusively limited to adulthood.
Pregnancy is, in fact, a particularly sensitive biological phase: fetal development, angiogenesis, neurological maturation, the endocrine system, and the immune system are undergoing profound changes.
However, the presence of plastic particles in the placenta does not automatically mean that they reach the fetus in clinically relevant quantities or that they cause a specific pathology.
Instead, it is an important biological signal that requires further studies.
Experimental research on animal models has shown that micro- and nanoplastics can alter placental function and fetal circulation. This data suggests possible mechanisms of interference with development, but it cannot be directly transferred to human pregnancy.
To understand the real risk, prospective studies will be needed that simultaneously measure exposure, internal dose, particle characteristics, and maternal-fetal outcomes.
The arteries: microplastics inside atherosclerotic plaque
One of the most relevant pieces of clinical evidence comes from the cardiovascular system.
A study published in the New England Journal of Medicine detected micro- and nanoplastics in the atherosclerotic plaques of patients undergoing carotid endarterectomy.
The most important result concerns the subsequent follow-up: people in whose plaques micro- and nanoplastics had been detected had a higher frequency of the composite endpoint consisting of non-fatal myocardial infarction, non-fatal stroke, or death from any cause compared to those without detectable particles in the plaque.
However, the association remains an association.
The study does not prove that microplastics caused the cardiovascular events. The patients already had atherosclerotic disease and belonged to a selected population that underwent surgery.
The data is nevertheless very significant because it directly links for the first time the presence of plastic particles in a cardiovascular lesion to a clinical outcome observed over time.
A possible interaction with vascular inflammation
Atherosclerosis is a complex disease involving lipid metabolism, immunity, oxidative stress, the endothelium, and chronic inflammation.
Micro- and nanoplastics could enter this biological network through several mechanisms.
Experimental studies have suggested that particles can stimulate inflammatory responses, alter endothelial cell function, and modify the activity of macrophages present in the plaque.
In the cardiovascular context, however, it is essential not to lose sight of the already well-established risk factors: blood pressure, smoking, diabetes, dyslipidemia, obesity, physical inactivity, and diet remain fundamental determinants of cardiovascular risk.
The possible influence of microplastics therefore represents a new element of the exposome, not a replacement of traditional risk factors.
Immune system: a response yet to be understood
The immune system represents one of the possible targets of microplastics.
Particles can be recognized by immune cells and interact with systems involved in the inflammatory response.
In experimental models, phenomena of immune activation, production of inflammatory mediators, and alterations of the function of certain cell populations have been described.
The most complex issue concerns the duration of exposure.
A particle occasionally introduced into the body can have a very different meaning compared to repeated exposure for decades to a mixture of particles of different compositions.
This is precisely one of the limitations of current research: real human exposure is chronic, complex, and difficult to standardize.
Microplastics, microbiota, and the intestine
The intestine constitutes one of the main interfaces between the environment and the body and could play a central role in the response to ingested microplastics.
Particles can come into contact with intestinal mucus, epithelial cells, and the microbiota.
Experimental studies have suggested possible alterations of intestinal permeability, microbial composition, and local immune response.
This opens another perspective: the biological effect of microplastics may not depend solely on their physical presence, but also on interactions with the microbiota and the intestinal immune system.
The gut-immunity-metabolism axis could therefore represent one of the most important areas of future research.
At the moment, however, the evidence in humans is not sufficient to state that microplastics cause a specific dysbiosis or a certain metabolic disease.
The exposome: plastic is only part of the problem
Considering microplastics in isolation from the rest of the environment risks producing an incomplete view.
The human body is simultaneously exposed to particles, metals, pesticides, solvents, endocrine disruptors, air pollutants, perfluoroalkyl substances, and numerous other contaminants.
This set of exposures constitutes the exposome.
The scientific difficulty consists in understanding the possible interactions between these factors.
A person is not exposed to "a microplastic" in controlled experimental conditions. Instead, they live in an environment in which different substances can be absorbed through food, breathing, and contact with materials.
For this reason, the future of environmental health research will probably move increasingly from the single substance to the integrated assessment of exposures.
From presence to causality: the most difficult transition
Microplastics research is going through a phase of rapid evolution.
Today we can state with increasing certainty that micro- and nanoplastic particles have been detected in various human biological tissues and fluids.
It is also possible to describe numerous experimental mechanisms through which these particles can interact with cells, the immune system, metabolism, and tissues.
It is much more difficult to establish what dose causes damage in humans, which particles are most dangerous, how long they must remain in the body, and what effects are truly attributable to their presence.
A systematic review from 2026, which analyzed exclusively studies conducted in living human beings, identified 25 relevant studies. Associations emerged between micro- and nanoplastic burden and certain cardiovascular, reproductive, gastrointestinal, and respiratory markers or alterations, but the overall quality of the evidence was limited by the heterogeneity of detection methods, the small size of the samples, possible confounders, and the difficulty of correctly measuring exposure.
It is an important conclusion: the evidence is growing, but causality has not yet been established for most of the hypothesized effects.
A new frontier in environmental medicine
The presence of microplastics in the body introduces a new dimension to the relationship between the environment and health.
For decades, environmental medicine has focused primarily on chemicals, metals, pesticides, and air pollutants. Today, it must also address artificial particulate materials that can persist in the environment, be ingested or inhaled, and reach different parts of the body.
The issue therefore concerns prevention, occupational medicine, maternal and child health, cardiology, neurology, gastroenterology, and reproductive medicine.
But above all, it draws attention to the concept of environmental prevention.
What we can do individually
Reducing individual exposure cannot solve a problem that stems primarily from industrial and environmental processes. Public health strategies, research, regulation, and reductions in plastic production and dispersal are necessary.
However, there are reasonable behaviors that can help reduce some daily exposures.
It may be useful to limit the use of single-use plastic where possible, choose reusable glass or steel containers for food and beverages, avoid heating food directly in plastic containers, and reduce unnecessary wear and tear on plastic materials intended to come into contact with food.
These behaviors should not be presented as absolute protection from microplastics: environmental exposure is much broader and cannot be completely eliminated through individual choices alone.
The most appropriate principle is therefore one of reasonable exposure reduction, without creating alarm.
Health in a changing environment
The discovery of microplastics in the human body changes how we can interpret the relationship between the environment and health.
We do not live apart from the environment: we breathe the air, consume water and food, come into contact with materials and surfaces, and host billions of microorganisms that participate in our physiology.
The body is therefore continuously engaged in interacting with signals and substances from the outside.
Microplastics and nanoplastics represent a relatively new component of this exposure and raise a question that medicine will have to address more and more often: how can we protect health when the environment itself becomes part of our biology?
The answer cannot be entrusted to a single therapy or a single food.
Research, environmental prevention, exposure reduction, a balanced diet, healthy lifestyles, and medicine capable of simultaneously considering the person, the environment, and the exposome will be needed.
Plastic is now a component of the human ecosystem. The scientific challenge of the coming years will be to understand to what extent this presence represents merely a trace of our industrial era and when, instead, it may become a biological determinant of health.
PLEASE NOTE
The information contained on this page is for informational and educational purposes only and does not constitute medical advice nor replace a doctor's assessment, diagnosis, or treatment prescriptions.
The presence of micro- or nanoplastics in human tissues does not, on its own, prove that such particles cause a particular disease. The available evidence is still largely observational, experimental, or based on small samples; larger, more methodologically homogeneous prospective studies are needed to define dose, exposure, causality, and long-term clinical consequences.
Reducing exposure to plastic represents an environmental prevention goal, but it must not become a source of individual alarm. Health remains the result of the interaction of numerous biological, environmental, behavioral, and social factors.
Bibliography
1. Nihart AJ, Garcia MA, El Hayek E, et al. Bioaccumulation of microplastics in decedent human brains. Nature Medicine. 2025;31:1114-1119. doi:10.1038/s41591-024-03453-1. The study detected micro- and nanoplastics in human brains, livers, and kidneys and highlighted a greater presence in the brain; the authors emphasize that the data do not demonstrate causality with dementia.
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