"Those who have a more Western-style diet, including foods like burgers and sodas, may have a greater chance of progressing to fatty liver disease if they are also exposed to polyethylene," Joshi said.

Why is this surprising?

Scientists have traditionally regarded polyethylene as biologically inert — meaning it was considered unlikely to interact with living systems compared with more chemically reactive plastics. Researchers had focused their attention on other types of microplastics instead.

The new results overturn that assumption. Polyethylene influenced liver function both on its own and alongside dietary risk factors, pointing to previously overlooked effects on the body's metabolism and protective mechanisms.

How did the team track the damage?

The researchers used a technique called spatial transcriptomics. In plain terms, this method measures which genes are active in a tissue while also preserving information about where each cell sits within that tissue. Standard gene-activity tools discard that location data; spatial transcriptomics keeps it, letting scientists pinpoint exactly where biological changes occur.

With this approach, the team mapped areas of liver damage associated with polyethylene exposure and identified two molecular players:

• PPAR-alpha, a protein that regulates fat metabolism in the liver. Polyethylene activated it, suggesting it plays a significant role in how the liver responds to microplastics.
• ANXA2, a gene associated with tissue repair, which may also contribute to the disease process.

Together, these findings sketch a more detailed picture of how polyethylene may interfere with the liver's normal functions, including the machinery that protects and repairs damaged tissue. Joshi believes understanding these pathways could eventually help researchers identify treatments that reduce the harm from microplastic exposure.

Could the damage be even more serious?

Several questions remain open. The team plans to investigate whether polyethylene exposure contributes to more advanced liver disease, including fibrosis — a condition in which repeated liver damage causes scar tissue to accumulate, impairing the organ's ability to function.

The researchers also want to examine other molecular processes involved in the liver's response, with particular focus on whether targeting the PPAR-alpha pathway could protect the liver against microplastic-related damage.

"This is the pioneering study showing that polyethylene can contribute to fatty liver disease and the use of spatial transcriptomics has determined exactly where the damage has happened within the liver," Joshi said. "The other microplastics might also be harmful to the liver, and we definitely need to look into other classes of microplastics."

How much should you worry?

Some caution is warranted. The findings come from experimental observations, and further research is needed to establish how they translate to everyday human exposure — the doses, durations, and routes involved in real life may differ from laboratory conditions.

Still, the study adds to growing concern about the health consequences of microplastics. For Joshi, the discovery is a reminder that chronic diseases may have contributors beyond familiar risk factors like diet. Understanding how common environmental pollutants interact with the body, he argues, could reveal previously unrecognized drivers of long-term health problems.