Microplastics that accumulate in the body can interfere with the immune system by preventing immune cells from devouring microbes and emptying dead cells, a new study in mice and laboratory dishes shows. Although it is still unclear how this might play out in the human body, experts say the study has potential implications for human health.
Microplastics are tiny particles that break down from plastic products, such as water bottles, food storage containers and freezer bags. Although these indigestible particles accumulates in the bodyscientists are still unsure how they contribute to disease. The new study revealed that these tiny particles can clog and disrupt the function of macrophages, cells that engulf and destroy potentially harmful viruses, bacteria or fungi, as well as dead cells.
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The build-up of microplastics in the body has been correlated with atherosclerosiswhere plaque builds up in the inner walls of the arteries, causing them to become narrow and stiff; neurodegeneration; and cancerso Justin Perryan immunologist at Memorial Sloan Kettering Cancer Center and senior author of the study, which was published March 10 in the journal Immunity.
Nevertheless, scientists have not proven that microplastics directly cause disease. “I think it really sparked myself and other colleagues in the field to try to understand this,” Perry told LiveScience. For the new study, he and his colleagues focused on polystyrenea common plastic used in food containers that breaks down into microplastic particles that can be as small as a virus or as large as a grain of sand.
The team focused on macrophageswhich engulfs material, such as dead cells and infectious microbes, from the environment and breaks them down into sugars, amino acids and fats that the cells can recycle. Scientists have shown it in mice and humans macrophages actively take up microplastics, but cannot break them down.
“It’s kind of scary, because it means we really haven’t developed an answer to them,” Perry said, so it’s possible that cells accumulate increasing volumes of microplastics throughout a person’s lifetime, he added.
At this time, there is no clear public health evidence directly linking microplastic exposure to increased infections in humans.
Eliseo Castillo, microplastics researcher at the University of Mexico
Perry and his colleagues administered this non-biodegradable plastic to human macrophages grown in laboratory plates. They also inserted the microplastic particles into the airways of mice, euthanized them and pulled out their lungs to image them under a microscope. Cells that took up the particles struggled to engulf and destroy dead cell material or infectious microbes such as bacteria or fungi, the team discovered.
To determine whether microplastics could prevent macrophages from fighting infections, the team administered the fungus Aspergillus fumigatuswhich causes respiratory tract infections in immunosuppressed humans, to the lungs of mice. They found that the mice given microplastics struggled to clear the infection and experienced worse disease.
“Whether this leads to higher infection rates in humans remains unknown,” Castillo said. “At this time, there is no clear public health evidence directly linking microplastic exposure to increased infections in humans.”
Microplastics also stopped macrophages from engulfing and destroying dead cell material, which could potentially cause debris to build up in tissue. Perry said people lose 2% of their body mass per day due to cell death, and it’s up to macrophages to clear away the dead junk. “That’s about 3 million (dying) cells per second. If you really do the math, that’s quite a load (for macrophages),” Perry added
A pile of dead cell material that DNA can alarm the immune system because it signals that a threat such as an infection may cause tissue damage. This can trigger inflammation, potentially triggering autoimmune disorders, Castillo said.
Microplastics can also reduce fertility when taken up by macrophages in the testicles. Perry and his colleagues exposed male mice to regular doses of microplastics and found that sperm count decreased over 18 weeks. He speculated on that microplastics can partly account for drop in sperm count set globally in the human population. The study did not examine the potential effect of these particles on female fertility.
Although the researchers demonstrated that human macrophages engulf microplastics when grown in laboratory dishes, the researchers still do not know how readily the cells would do so in the body.
Perry plans to study samples taken from humans — specifically how microplastics may contribute to atherosclerotic plaques that clog blood vessels. It is already known that macrophages are loaded with undigested material accumulates in these blood flow-stopping plaquesso he and his colleagues hypothesize that microplastics may be exacerbating the problem, he said.
This article is for informational purposes only and is not intended to provide medical advice.
Codo, AC, Romero-Pichardo, JE, Wang, Z., Aufiero, MA, Lazarov, T., Saitz Rojas, W., Walker, NS, Nair, A., Cole, RF, Adkins, S., Dong, E., Fadojutimi, K., Martínez de la Torre, C., Hohl, F. KR, Lucas, CD and Perry, JSA (2026). Polystyrene microplastic-induced pathophysiology is driven by disruption of efferocytosis. Immunity, 59(3). https://doi.org/10.1016/j.immuni.2026.01.009
