Rising reliance on single-use packaging and disposable plastics has dramatically increased environmental contamination. Once released, plastics fragment into persistent materials that resist degradation, posing long-term ecological effects. The effects of micro- and nanoplastics (MNPs) on human health have only begun to be systematically studied in the past two decades.
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Between 1960 and 2005, the amount of plastic in municipal solid waste increased tenfold. This trend accelerated during the COVID-19 pandemic due to greater consumption of protective equipment and packaging.
The term ‘microplastics’ was first introduced in 2004 and is now defined as particles smaller than 5 mm. A lower threshold of 1 µm often distinguishes microplastics and nanoplastics, which are smaller and more difficult to detect.1
While microplastics are now routinely detected in environmental samples, identifying nanoplastics remains technically challenging due to methodological limitations. Evidence suggests these particles can trigger oxidative stress, inflammatory response, and tissue-level changes in biological systems, raising concerns about potential long-term health risks.
Exposure Pathways
Human exposure to micro- and nanoplastics (MNPs) occurs primarily via inhalation, ingestion, and dermal contact. Airborne microplastics can originate from dust, synthetic textiles, and tire wear, and are easily inhaled, with indoor environments generally presenting higher exposure risks than outdoor settings.[2]
Ingestion is another important pathway. Contaminated food and water are well-documented sources, especially shellfish such as mussels, which act as vectors and accumulate plastic due to their filter-feeding behavior. Drinking water, particularly bottled water, may also contain MNPs released during production or through mechanical wear from repeated opening and closing of bottles.
Dermal and mucosal exposures arise from personal care products (PCPs) containing MNPs, including cosmetics, toothpaste, and exfoliating agents. Depending on their size, some particles may penetrate the skin or mucosa, while others are ingested during daily routines, such as swallowing toothpaste residues.
Despite recognition of these pathways, standardized methods to quantify exposure remain limited, particularly for nanoplastics, which are difficult to detect in biological samples.
Particle Traits and Toxic Potential
The toxicological impact of MNPs is influenced by several characteristics such as size, shape, surface chemistry, and particle composition. Nanoplastics (<1 µm) can cross physiological barriers and enter cells more easily, whereas larger microplastics primarily interact with gastrointestinal and respiratory epithelia. Fiber-like or irregularly shaped particles may mechanically disrupt tissues, while spherical particles may follow distinct biodistribution patterns in the body.
Surface properties, including hydrophobicity and charge, influence how particles interact with biological membranes and proteins, shaping inflammatory and oxidative responses. Once in biological fluids, plastics can adsorb proteins and alter recognition by immune cells, affecting cellular uptake and systemic distribution.
Beyond their intrinsic properties, MNPs can act as carriers for environmental contaminants, in a mechanism known as the Trojan‑horse effect. Microplastics adsorb heavy metals, persistent organic pollutants, or microbes, and subsequently release them inside biological systems, increasing toxicity.[3]
The combination of particle traits and associated contaminants highlights the need to assess both intrinsic and acquired properties when evaluating health risks.
Mechanisms of Toxicology
MNPs can provoke cellular and tissue responses via oxidative stress, inflammation, and disruption of membrane integrity. Both in vitro and in vivo studies indicate that nanoplastics can stimulate the production of reactive oxygen species (ROS), damage DNA, and alter gene expression.[4]
Organ-specific accumulation has been observed in the liver, kidney, gut, and lungs, with evidence of systemic distribution documented in some animal models. Gastrointestinal exposure may lead to local inflammation and microbiome imbalances, while inhalation can damage respiratory tissues and modulate immune responses.
Translocation from mucosal surfaces to systemic circulation remains an area of active investigation for MNPs, as this process could enable accumulation in secondary organs and contribute to chronic health effects.
Recent Breakthroughs and Methodological Advances
Detection and characterization technologies are improving rapidly. In microplastic research, micro-Fourier transform infrared spectroscopy (µFTIR) and Raman microspectroscopy remain foundational methods for microplastic identification. Recent advances incorporating machine learning have significantly improved spectral classification and throughput, reducing manual interpretation and enhancing sensitivity.[5]
At the biological level, fluorescently labeled nanoplastics are increasingly used to study cellular uptake and intracellular distribution with high-resolution microscopy, enabling more precise insights into particle-cell interactions and biodistribution. These innovations are helping to bridge the gap between environmental detection and mechanistic toxicology.
Knowledge Gaps and Challenges
Despite progress, significant knowledge gaps persist. Quantifying nanoplastics in biological tissues remains difficult, and standardized protocols for sampling and detection are lacking. Furthermore, dose-response relationships, chronic low-level exposures, and interactions with co-contaminants are poorly understood.
Human epidemiological data remain scarce, and extrapolating results from in vitro or animal models to real-world human exposure is limited by differences in particle properties, exposure routes, and biological responses. Addressing these challenges will be essential for accurate risk assessment and regulatory guidance.
Conclusion
Micro- and nanoplastics represent a growing challenge for human health, driven by widespread environmental contamination and diverse exposure pathways. Inhalation, ingestion, and dermal contact each contribute to cumulative exposure, while particle traits such as size, shape, and surface chemistry, and their ability to carry co-contaminants, influence toxic potential.
Mechanistic studies increasingly link MNPS to oxidative stress, inflammation, and cellular and tissue-level disruption. Recent methodological advances have improved detection and exposure modeling, although substantial knowledge gaps remain, particularly regarding nanoplastic quantification, chronic low-dose effects, and human epidemiology.
Closing these gaps through standardized methodologies and interdisciplinary research will be essential for informed risk assessment, regulatory decision-making, and the development of effective strategies to mitigate exposure and protect public health.
References
- Ramsperger, A. F. R. M., et al. (2023). Nano- and microplastics: a comprehensive review on their exposure routes, translocation, and fate in humans. NanoImpact, 29, 100441.https://doi.org/10.1016/j.impact.2022.100441. Available: https://www.sciencedirect.com/science/article/pii/S2452074822000635
- Yee, M. S., Hii, L. W., Looi, C. K., Lim, W. M., Wong, S. F., Kok, Y. Y., Tan, B. K., Wong, C. Y. & Leong, C. O. (2021). Impact of Microplastics and Nanoplastics on Human Health. Nanomaterials (Basel), 11.10.3390/nano11020496.
- Hildebrandt, L., Nack, F. L., Zimmermann, T. & Pröfrock, D. (2021). Microplastics as a Trojan horse for trace metals. Journal of Hazardous Materials Letters, 2, 100035.https://doi.org/10.1016/j.hazl.2021.100035. Available: https://www.sciencedirect.com/science/article/pii/S266691102100023X
- Jahedi, F. & Jaafarzadeh Haghighi Fard, N. (2025). Micro- and nanoplastic toxicity in humans: Exposure pathways, cellular effects, and mitigation strategies. Toxicol Rep, 14, 102043.10.1016/j.toxrep.2025.102043.
- Hufnagl, B., Stibi, M., Martirosyan, H., Wilczek, U., Möller, J. N., Löder, M. G. J., Laforsch, C. & Lohninger, H. (2022). Computer-Assisted Analysis of Microplastics in Environmental Samples Based on μFTIR Imaging in Combination with Machine Learning. Environ Sci Technol Lett, 9, 90-95.10.1021/acs.estlett.1c00851.
Last Updated: Oct 13, 2025