On the 23rd, researcher Lee Da-yong and the research team at the Bio-New Drug Translational Research Center of the Korea Research Institute of Bioscience and Biotechnology (KRIBB) said they had, for the first time in the world, identified that polyethylene microplastics ingested by mothers are transferred to infants through breast milk, resulting in a disrupted immune system and increased vulnerability to viral infections.
Plastic products we use in everyday life, such as cups, packaging, and plastic bags, are now being found not only in air, water, and food but also inside our bodies. Microplastics, far smaller than a strand of hair, are emerging not as mere waste but as a new pollutant that threatens human health.
In particular, pregnant women and infants have vulnerable immune systems and react much more sensitively to harmful environmental substances. However, it has not yet been clearly determined how microplastics transmitted from mothers to children affect immune function.
The researchers administered commonly used polyethylene (PE) microplastics to pregnant mice and confirmed that the material moved into the pups' bodies through breast milk and, in particular, accumulated in large amounts in the spleen.
The spleen is an organ that regulates immune cells in the body, and when its balance collapses, infectious diseases occur easily. In pups exposed to microplastics, T cells and NK cells, which are responsible for immunity, decreased, while B cells that cause inflammation increased abnormally, showing a clear immune system imbalance.
After microplastics accumulated in the pups' spleens through breast milk, the researchers also confirmed that an imbalance in immune cell distribution and reduced secretion of antiviral immune substances (interferons and pro-inflammatory cytokines) persisted throughout growth. This indicates that it is not a temporary response to short-term exposure but can disrupt the entire immune development process and weaken resistance to infection.
In addition, when the researchers infected these mice with the H1N1 swine flu virus, body weight dropped sharply after infection compared with the control group, and secretion of antiviral immune substances was markedly lower, showing a greatly weakened ability to suppress the virus. This proves that microplastics are not simply inert foreign substances remaining in the body but harmful factors that disrupt the immune system and increase susceptibility to infectious diseases.
Lead researcher Lee Da-yong said, "This study is the first scientific demonstration that microplastics can disrupt the immune system across generations," and emphasized, "It is urgent to reduce plastic use and make social efforts to minimize microplastic exposure in daily life, such as in food and water."
The results were published on Oct. 15 (local time) in the international journal Journal of Hazardous Materials.
References
Journal of Hazardous Materials (2025), DOI: https://doi.org/10.1016/j.jhazmat.2025.139965