Micro- and Nanoplastics: Their Presence and Impact on Human Health

Micro- and nanoplastics (MNPs) have been increasingly identified within various human tissues, raising significant concerns about their potential health implications. Recent studies have detected these small plastic particles in critical areas such as the central nervous system, blood, heart, testis, semen, placenta, and other organs. The exposure to MNPs has been linked to several adverse health outcomes, including Inflammatory Bowel Disease, autism spectrum disorder, and cancer. However, much of the existing research is based on small sample sizes, necessitating further investigation to solidify these associations.

In early 2025, two pivotal studies delved into the presence of MNPs in human brains and their implications for neurological health, while additional research focused on their effects on female reproductive health. Remarkably, even “bioplastics” have been shown to pose health risks when tested in vivo, highlighting the necessity for comprehensive studies in this area.

MNP Accumulation in the Human Brain

A recent study by Alexander J. Nihart and colleagues from the University of New Mexico Health Sciences revealed alarming concentrations of MNPs in the human brain. Their research, published in Nature Medicine, found that MNP levels in brain tissue were 7 to 30 times higher than those in the liver and kidney, with a median concentration of 4,917 µg/g. Notably, samples from individuals diagnosed with dementia exhibited even higher levels, averaging 26,076 µg/g. While these findings are significant, the authors emphasized that the data is associative and does not confirm a causal relationship between MNPs and health outcomes, calling for further research to explore their potential role in neurological disorders.

The researchers employed advanced analytical techniques, including pyrolysis gas chromatography-mass spectrometry, to assess plastic particles down to the nanoscale. This approach allowed for a comprehensive analysis of the mass of particles present in the samples, although it did not enable quantification of individual particle numbers.

Previous studies have already indicated the accumulation of polyethylene microplastics in the brain, with some research suggesting potential links to autism spectrum disorder-like symptoms in mouse models. Additionally, in vitro studies have demonstrated that microplastics can adversely affect the development of human forebrain organoids.

Further investigations led by Haipeng Huang from the Chinese Research Academy of Environmental Sciences explored the mechanisms behind MNP-induced brain dysfunction. Their work, also published in Nature Medicine, revealed that circulating microplastics can be engulfed by blood cells, leading to blockages in cerebral blood vessels. This obstruction is associated with reduced blood flow and subsequent neurobehavioral disorders. However, the long-term consequences of such blockages and the cumulative effects of repeated MNP exposure remain largely unknown.

Impact of MNPs on Female Reproductive Health

The presence of MNPs has been frequently documented in the human placenta and amniotic fluid, prompting research into their effects on female reproductive health. A study by Qiaoling Wang from Tongji University demonstrated the detection of microplastics in the follicular fluid of women undergoing assisted reproductive technology. The findings indicated a correlation between higher microplastic concentrations and lower fertilization rates, particularly with polyethylene particles being the most prevalent.

In a contrasting study, Xiu Cheng and colleagues from Nanchang University examined the multigenerational reproductive toxicity of polystyrene nanoparticles. Their research showed that maternal exposure to these nanoparticles resulted in increased rates of miscarriage, premature birth, and long-term fertility issues in offspring. These findings highlight the potential transgenerational effects of MNP exposure, necessitating a comprehensive understanding of its implications for reproductive health.

A systematic review conducted by Inam Özem further corroborated these findings, indicating that MNP exposure adversely affects ovarian function, fertility, and hormone levels. The review included 15 studies published between 2021 and 2023, emphasizing the need for standardized research methodologies to address the existing gaps in knowledge.

The Toxicity of Bioplastic Particles

While bio-based and biodegradable plastics are often viewed as environmentally friendly alternatives to traditional plastics, recent studies have raised concerns about their chemical toxicity. Research led by Qiancheng Zhao from Peking University highlighted that microplastics derived from polylactic acid (PLA) also exhibit male reproductive toxic effects. In vitro and in vivo experiments revealed that PLA microplastics can compromise the blood-testis barrier and disrupt spermatogenesis, ultimately impairing sperm function.

Since June 2021, the European research cluster CUSP has been actively working to deepen the understanding of MNPs’ health impacts, involving 71 organizations from 21 countries. The results of this collaborative effort are set to be shared during a final scientific conference in February 2025.

Conclusion

The mounting evidence surrounding the presence and effects of micro- and nanoplastics in the human body underscores an urgent need for further research. As the implications of these pollutants on human health become increasingly clear, it is imperative that scientists, health professionals, and policymakers work together to address these challenges and develop strategies to mitigate their impact.

References

Cheng, X., et al. (2025). “Maternal exposure to polystyrene nanoplastics during gestation and lactation caused fertility decline in female mouse offspring.” Ecotoxicology and Environmental Safety.

Huang, H., et al. (2025). “Microplastics in the bloodstream can induce cerebral thrombosis by causing cell obstruction and lead to neurobehavioral abnormalities.” Science Advances.

Inam, Ö., (2025). “Impact of microplastics on female reproductive health: insights from animal and human experimental studies: a systematic review.” Archives of Gynecology and Obstetrics.

Nihart, A. J., et al. (2025). “Bioaccumulation of microplastics in decedent human brains.” Nature Medicine.

Wang, Q., et al. (2024). “Polyethylene microplastic exposure adversely affects oocyte quality in human and mouse.” Environment International.

Zhao, Q. et al. (2025). “Polylactic Acid Micro/Nanoplastic Exposure Induces Male Reproductive Toxicity by Disrupting Spermatogenesis and Mitochondrial Dysfunction in Mice.” ACS Nano.