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Biotoxic effects of microplastics and nanoplastics across biological systems: A systematic review and meta-analysis
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This review pooled results from over 170 studies to confirm that microplastics and nanoplastics cause real biological harm—triggering oxidative stress (cell damage from unstable molecules), stunted growth, and reproductive problems across many organisms tested in labs. The smallest plastic particles and longer exposure times caused the worst effects, and a common plastic type (polystyrene, found in foam packaging and disposable items) was especially harmful. While this research was done in cells and animals rather than humans directly, it strengthens the case that reducing plastic exposure in daily life is a reasonable precaution as scientists work toward clearer
Micro plastics (MPs) and nano plastics (NPs) are new emerging contaminants of concern in the environment and to human health. Although there was growing experimental evidence, there was no quantitative synthesis available regarding their biological toxicity in various experimental systems. The purpose of the current systematic review and meta-analysis was to assess and quantify the toxic effects of MPs and NPs on various biological systems. The review was conducted based on PRISMA 2020 guidelines and a PROSPERO registration was done in advance (CRD420251166074). Literature search was systematically done in PubMed, Scopus, Web of Science, Embase, Google Scholar and Cochrane library till November 2025. Reported experimental in vivo and in vitro quantitative toxicological results from exposure to MP/NP were eligible. A total of 212 studies were included in qualitative synthesis, of which 174 studies were quantitatively analysed. Standardised mean difference (SMD) was pooled using a random effects model. Subgroup analysis and meta-regression were performed to investigate the impact of particle size, polymer type and exposure time. The I² statistic was used to assess the heterogeneity of the studies. The meta-analysis showed that the MP/NP exposure significantly influenced oxidative stress and biological functions (pooled SMD = −0.45; 95% CI: −0.71 to −0.19; p < 0.001). Toxic effects were more severe with smaller sized nanoplastics and greater exposure times. The polystyrene particles had the greatest effect sizes of all the polymer types. There was moderate heterogeneity (I² = 52–68%) which may have been attributed to differences in experimental design, exposure levels, and biological models. Some of the limitations were significant differences in exposure conditions and particle characterization between the studies. In general, MPs and NPs cause oxidative stress, growth defects, and reproductive impairment in a variety of biological systems. These results can contribute to better environmental risk assessment, and indicate the need for standardisation of testing protocols and for studies to be conducted under environmentally relevant exposure conditions in the future.
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This systematic review summarized 133 studies on how micro- and nanoplastics affect human health based on mammalian research. The evidence points to cell damage, inflammation, gut disruption, and reproductive harm, though most studies focused on polystyrene particles and more research is needed on other common plastic types.
Biological Effects of Microplastics: A Review.
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Researchers reviewed how microplastics harm a wide range of living things, finding they cause physical damage, inflammation, oxidative stress, and reproductive problems in aquatic animals, while also carrying toxic chemicals and dangerous bacteria into organisms. Major gaps remain in understanding the effects of long-term low-dose exposure and the risks posed by even tinier nanoplastics.
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This review maps the biological harm caused by micro- and nanoplastics to formal toxicity pathways, finding that oxidative stress is a common starting point for damage at every level from cells to whole organisms. Researchers found that in ecological settings, this oxidative damage cascades into growth inhibition and behavioral changes, while in human health contexts it may trigger inflammatory responses. The study highlights that more mammalian research is needed to fully define the health risks of plastic particle exposure.
Exploring toxicological pathways of microplastics and nanoplastics: Insights from animal and cellular models
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This review examines what animal and cell studies have revealed about how microplastics and nanoplastics cause harm at the molecular level, including promoting inflammation, oxidative stress, and cell death. Most research has focused on reproductive toxicity and polystyrene particles, while effects on the gut, brain, and heart remain understudied. The authors note that many experiments use unrealistic concentrations and synthetic particles, making it difficult to apply the results to real-world human exposure.
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Researchers exposed single-celled marine organisms called foraminifera to three types of engineered nanoparticles — including polystyrene nanoplastics — and found that all three accumulated inside the cells and triggered oxidative stress (a form of cellular damage). This study shows that even microscopic seafloor organisms are vulnerable to nanoplastic pollution, expanding the known range of species harmed by plastic contamination.
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