Micro- and nanoplastics have quietly become one of the most pervasive exposures of modern life. A comprehensive review published in the Journal of Advanced Research synthesizes the fast-moving evidence on how these particles enter the human body, what they do once they arrive, and, crucially, what science still cannot say about their health consequences. The review defines microplastics as solid polymer-containing particles between 1 micrometer and 5 millimeters, and nanoplastics as particles from 1 nanometer to less than 1 micrometer, and it arrives at a sobering but carefully calibrated conclusion: the particles are everywhere in human tissues, plausible mechanisms of harm exist, but proof that they cause disease in people remains elusive.
The exposure cycle begins with human activity itself. Agricultural plastic mulch films degrade under ultraviolet radiation, mechanical abrasion, and temperature swings, fragmenting progressively into ever smaller particles. Food-contact materials shed plastics during manufacture, washing, heating, and storage. Textile production and laundering release synthetic microfibers, while industrial cutting and abrasion add further emissions. Once released, the particles disperse across terrestrial, aquatic, and atmospheric compartments, and inadequate waste management and inefficient wastewater treatment compound their accumulation. From there, they re-enter the body through contaminated drinking water and food, and through inhaled airborne particles, perpetuating a continuous exposure loop.
What makes these particles so difficult to assess is their staggering heterogeneity. A microplastic particle is not a single substance but a composite: a polymer matrix such as polyethylene, polypropylene, polyethylene terephthalate, or polystyrene; chemical additives including phthalate plasticizers like DEHP and DBP, brominated and organophosphorus flame retardants, stabilizers, and pigments; and a cargo of adsorbed substances ranging from persistent organic pollutants and heavy metals to microorganisms. Polymer identity alone does not determine toxicity, because particles of the same polymer can differ enormously in size, shape, surface chemistry, and aging state. Weathering matters too: ultraviolet-driven photo-oxidation fragments polymers and introduces oxygen-containing surface groups that alter hydrophilicity, charge, and contaminant sorption. In marine environments, particles even act as artificial substrates, hosting microbial communities of Pseudomonas and Vibrio that differ from surrounding seawater and can drift across long distances.
Humans encounter these particles through ingestion, inhalation, dermal contact, maternal-fetal transfer, and even medical procedures. Ingestion is considered a dominant route: seafood, particularly filter-feeding bivalves and small fish, accumulates particles from polluted waters, and drinking water can be contaminated during treatment, bottling, or storage. Livestock may ingest particles from their environment, creating secondary contamination of milk and eggs. Inhalation is significant indoors and in occupational settings, where airborne concentrations vary with ventilation and source profile; disposable surgical masks have even been shown to release microplastic fibers during repeated handling. Dermal exposure is plausible but poorly characterized, since the intact stratum corneum restricts penetration of most particles, with entry more likely through hair follicles, sweat ducts, or damaged skin. Perhaps most striking is the iatrogenic route: studies of infusion bags, tubing, and injectable solutions have detected particles released during intravenous administration, introducing them directly into the circulation without crossing epithelial barriers at all.
The mechanistic picture is organized around three overlapping categories. Particle-associated effects include direct physical interactions: experiments by Fleury and Baulin showed that microplastics contacting lipid bilayers increase membrane tension and shorten membrane lifetime, and particle exposure in erythrocyte and fibroblast models has been linked to hemolysis and lactate dehydrogenase release. Chemical-associated effects arise from additive release and contaminant sorption or desorption, which depend on polymer type, aging, and the surrounding matrix; aged particles carrying heavy metals exacerbated intestinal injury in one experimental model. Biologically mediated responses then follow downstream: oxidative stress, organelle dysfunction, inflammatory signaling, apoptosis, immune dysregulation, and endocrine interference. In immune cells, the effects are particularly detailed. Macrophages take up particles and suffer impaired lysosomal activity and phagocytic function, while activation of the NF-kappa-B pathway drives excessive release of tumor necrosis factor-alpha and interleukin-6. Neutrophils internalize particles and form neutrophil extracellular traps through ROS-dependent signaling involving peptidyl arginine deiminase 4 and the NLRP3 inflammasome, amplifying inflammation and tissue damage.
The catalogue of human tissues where particles have now been detected reads like an anatomy lesson: blood, stool, lung, placenta, breast milk, endometrium, cerebrospinal fluid, postmortem brain, olfactory bulb, coronary and carotid arteries, and even bone, cartilage, and intervertebral disc tissue. Blood from 22 healthy adults contained a mean summed quantifiable polymer concentration of 1.6 micrograms per milliliter, dominated by PET, polyethylene, styrene polymers, and PMMA. Microplastics appeared in 11 of 13 surgical lung samples and in 26 of 34 breast milk samples. In cerebrospinal fluid, polymer composition differed according to blood-brain-barrier status, and postmortem studies found higher brain particle burdens in dementia cases than in controls, with refractile inclusions visible in immune-cell-rich regions and vascular walls. Yet the review is emphatic: detection demonstrates exposure, not causation. Tumors, with their leaky vasculature and impaired clearance, may accumulate particles after malignancy develops, a classic reverse-causation trap.
Among disease categories, cardiovascular research currently offers the most clinically consequential human associations. In a prospective observational cohort of 257 patients undergoing carotid endarterectomy, detection of micro- and nanoplastics in atherosclerotic plaque was associated with a higher composite risk of myocardial infarction, stroke, or death, with a hazard ratio of 4.53 and a 95 percent confidence interval of 2.00 to 10.27. A separate study of patients with myocardial infarction found that PVC concentrations in coronary blood were higher in those who experienced major adverse cardiac events and correlated positively with inflammatory cytokines including IL-1beta, IL-6, IL-18, and TNF-alpha. Experimental work supports biological plausibility: polystyrene nanoplastics induced hemolysis, platelet aggregation, endothelial senescence, and impaired vasorelaxation in cell and tissue models, and low-dose particles increased hypertrophy markers in human stem-cell-derived cardiac organoids. Still, the authors caution that residual confounding, selected clinical populations, and analytical limitations mean these observational associations do not establish causality.
Elsewhere in the body, the evidence is largely mechanistic. In neurological research, nanoplastics aggravated dopaminergic neuronal degeneration and alpha-synuclein aggregation in a Caenorhabditis elegans Parkinson’s model, aged particles caused more severe neurobehavioral deficits than virgin ones, and human cortical spheroids showed disrupted neural development after prolonged exposure. Reproductive studies report placental and endometrial detection, altered trophoblast signaling, and testicular and ovarian effects in rodents, including polycystic ovary syndrome-like changes under co-exposure to polystyrene particles and DEHP. Digestive research links particles to gut microbiome disruption, intestinal inflammation, and hepatic effects through the gut-liver axis, while respiratory models show oxidative stress, ferroptosis, and epithelial senescence. Infectious-disease work suggests particles can carry microbial communities, antibiotic resistance genes, and even viruses, and polyethylene particles promoted Helicobacter pylori colonization in mice, but documented transmission of human infection remains absent.
The review’s most valuable contribution may be its unflinching account of the field’s methodological weaknesses. Most mechanistic studies rely on pristine, monodisperse, spherical polystyrene beads, whereas real-world exposure involves heterogeneous, weathered fragments and fibers; a review of 715 laboratory studies found manufactured polystyrene spheres of 1 to 50 micrometers predominating, often with incomplete particle characterization. Commercial bead suspensions may contain surfactants or residual monomers that confound results. Analytical platforms each have blind spots: FTIR and Raman spectroscopy identify polymer type but struggle below certain size limits, while pyrolysis gas chromatography-mass spectrometry quantifies polymer mass without reporting particle number or morphology. Inconsistent dose metrics, whether mass, particle number, or surface area, make cross-study comparison treacherous, and apparent differences between tissues or populations may partly reflect method rather than biology. Harmonized reference materials, rigorous procedural blanks, and transparent reporting of detection limits are urgently needed.
The path forward, the authors argue, requires prospective human cohorts with repeated exposure measurements, validated clinical outcomes, and contamination controls stringent enough to survive scrutiny. Experimental work should shift toward environmentally representative particles, chronic low-dose and multi-route exposure, and justified dose metrics. Risk mitigation should emphasize source reduction, safer material design, and life-cycle assessment of biodegradable alternatives, whose degradation products may themselves be biologically active. Until exposure-response relationships are established, the honest public-health message is one of calibrated concern: the particles are undeniably inside us, the mechanisms of potential harm are biologically coherent, and the magnitude of the risk, for now, remains an open and urgent question.
Subject of Research: Human exposure to micro- and nanoplastics and their potential effects on human health
Article Title: Micro- and nanoplastic exposure and human health
Article References: Wu, W., Wang, Y., Shi, J., Feng, H., Ren, H., Huang, H., Lv, W., Xiao, Z., & Zhou, Y. (2026). Micro- and nanoplastic exposure and human health. Journal of Advanced Research. https://doi.org/10.1016/j.jare.2026.10.009
Image Credits: AI Generated
DOI: 10.1016/j.jare.2026.10.009
Keywords: microplastics, nanoplastics, human health, exposure routes, toxicology, cardiovascular disease, inflammation, oxidative stress, placenta, blood-brain barrier, analytical methods, risk assessment
