Tiny plastic particles that have quietly become part of daily life may pose a greater threat to liver health than previously thought, especially for people consuming high-fat diets, according to new research from the University of Oklahoma published in the journal Science Advances.

The study found that mice exposed to microplastics while eating a high-fat, high-cholesterol diet had more than twice the levels of blood markers related to liver damage compared to mice that were exposed to the same plastic particles while eating a regular diet. The findings raise fresh questions about how environmental pollution and modern dietary habits may be working together to affect human health.

Microplastics are tiny pieces of plastic formed when larger plastic items break down over time. They have been detected in drinking water, food, air, human blood, lungs, placentas and other tissues. Scientists around the world are increasingly investigating whether these particles could contribute to inflammation, organ damage and chronic disease.

“Exposure to microplastics is inevitable. We inhale them and ingest them, and they are on our skin,” said Tae Gyu Oh, Ph.D., who led the study and is an assistant professor of oncology science in the OU College of Medicine. “Numerous studies have shown the presence of microplastics in our bodies, but we wanted to investigate the effects of microplastics in the setting of a high-fat, high-cholesterol diet, which has also been demonstrated to harm the liver. We expected to see a synergistic effect between the diet and microplastics, and we did.”

The researchers focused on polyethylene, the world's most widely used plastic. It is commonly found in products, such as plastic bags, food packaging, and milk containers. Over eight weeks, mice received equal amounts of microplastics while being fed either a normal diet or one designed to mimic metabolic dysfunction-associated steatohepatitis, or MASH, a severe form of fatty liver disease that can lead to liver scarring and failure.

Inside the laboratory, the team examined liver tissue using increasingly detailed technologies. The closer they looked, the more damage they found. Their most powerful tool was spatial transcriptomics, a technique that allows scientists to identify exactly where changes occur inside tissues rather than averaging signals across millions of cells.

“This high-resolution view helped us identify specific ‘hot spots’ of liver damage at the single-cell level that would have been impossible to detect using traditional approaches,” Oh said.

The study also highlighted the role of PPAR-alpha, a protein that helps the body break down fats for energy. Researchers found that microplastic exposure appeared to influence another gene, Anxa2, which is involved in tissue repair.

“These findings suggest that microplastics may affect some of the liver’s natural defences and repair mechanisms,” Oh said. “Understanding this relationship may point us toward new ways to protect liver health.”

The findings add to a growing body of evidence linking microplastics to health concerns. Researchers from institutions across Europe, Asia, and North America have previously reported microplastic particles in human organs and linked them with inflammation, oxidative stress, and metabolic disturbances. However, experts caution that the Oklahoma study was conducted in mice, meaning further research is needed before firm conclusions can be drawn about risks in humans.

Still, the study offers an important glimpse into a future challenge. As plastic pollution continues to accumulate and fatty liver disease rises globally, scientists are increasingly asking whether two defining features of modern life may be interacting inside the body in ways that have largely gone unnoticed.

“Microplastics are now part of our everyday environment, but we are still learning how they affect the body,” Oh said. “By gaining such a detailed look at the liver, we were able to see specific regions where microplastic exposure triggered inflammation and altered important biological pathways. These findings provide new clues about how environmental exposures may contribute to liver disease and point to areas for future investigation.”