Microplastics have been found to penetrate deep into the human body including in the lungs, liver, kidney, spleen, brain and bones. Now, a study suggests they can alter the human gut microbiome and may even increase risk of certain diseases.
Plastic particles smaller than 5mm are commonly found in the environment and can be found in food and water. For the study, researchers grew gut microbiome cultures from stool samples provided by five healthy volunteers. The cultures were then exposed to five common types of microplastics at concentrations humans are thought to be exposed to, as well as higher doses.
The cultures exposed to microplastics showed a significant increase in acidity, indicating altered microbial metabolic activity.
Analysis revealed that certain bacterial groups increased or decreased depending on the microplastic type. These shifts were accompanied by changes in the chemicals produced by the bacteria.
Study leader Christian Pacher-Deutsch, of the research institution CBmed in Austria, said: “At this stage, the exact pathways remain unclear, but several plausible explanations are emerging.
“Microplastics may change microbial composition by creating physical or chemical environments that favour certain bacteria. For instance, biofilms can form on microplastic surfaces, providing new niches that some microbes colonise more rapidly.
“Microplastics may also carry chemical substances that directly influence bacterial metabolism. This can lead to changes in acid production, which may serve as a bacterial stress response, unintentionally altering the gut’s pH.
“These shifts could then trigger feedback loops that further affect the balance of the microbiome.”
Some of the changes observed reflected patterns previously linked to diseases such as bowel cancer and depression, the researchers said.
Mr Pacher-Deutsch added: “These findings are significant given how pervasive microplastic exposure is in everyday life. Microplastics have been found in fish, salt, bottled water, and even tap water, meaning that most people are exposed daily through ingestion, inhalation and skin contact.
“The key takeaway is that microplastics do have an impact on our microbiome. While it’s too early to make definitive health claims, the microbiome plays a central role in many aspects of well-being, from digestion to mental health.
“Reducing microplastic exposure where possible is therefore a wise and important precaution.”
The dinging were presented at United European Gastroenterology’s annual congress, UEG Week 2025.