Microplastics Journey from Gut to Vital Organs

Summary: A new study highlights the alarming infiltration of microplastics into human tissues, including the kidney, liver, and brain. The study investigates how these tiny particles, commonly ingested through water, food, and air, breach the gastrointestinal tract to affect major organs and metabolic pathways.

The findings underscore the potential health risks associated with microplastics, which are ubiquitous in our environment and are ingested at an average rate equivalent to the weight of a credit card each week. This pioneering research sheds light on the systemic impacts of microplastics, suggesting significant implications for public health and policy.

Key Facts:

  1. Microplastics have been found to cross the gastrointestinal barrier and migrate into organs such as the liver, kidneys, and brain, altering metabolic pathways in these tissues.
  2. An average person ingests approximately 5 grams of microplastics weekly, with these particles being pervasive in everyday environments, including oceans, tap water, and the food supply.
  3. The study highlights concerns about the long-term accumulation of microplastics in the body and their potential to exacerbate underlying health conditions, particularly in the context of chronic gastrointestinal diseases.

Source: University of New Mexico

It’s happening every day. From our water, our food and even the air we breathe, tiny plastic particles are finding their way into many parts of our body.

But what happens once those particles are inside? What do they do to our digestive system?

In a recent paper published in the journal Environmental Health Perspectives, University of New Mexico researchers found that those tiny particles – microplastics – are having a significant impact on our digestive pathways, making their way from the gut and into the tissues of the kidney, liver and brain.

This shows a hand covered in plastic beads.
Scientists estimate that people ingest 5 grams of microplastic particles each week on average – equivalent to the weight of a credit card. Credit: Neuroscience News

Eliseo Castillo, PhD, an associate professor in the Division of Gastroenterology & Hepatology in the UNM School of Medicine’s Department of Internal Medicine and an expert in mucosal immunology, is leading the charge at UNM on microplastic research.

“Over the past few decades, microplastics have been found in the ocean, in animals and plants, in tap water and bottled water,” Castillo, says. “They appear to be everywhere.”

Scientists estimate that people ingest 5 grams of microplastic particles each week on average – equivalent to the weight of a credit card.

While other researchers are helping to identify and quantify ingested microplastics, Castillo and his team focus on what the microplastics are doing inside the body, specifically to the gastrointestinal (GI) tract and to the gut immune system.

Over a four-week period, Castillo, postdoctoral fellow Marcus Garcia, PharmD, and other UNM researchers exposed mice to microplastics in their drinking water. The amount was equivalent to the quantity of microplastics humans are believed to ingest each week.

Microplastics had migrated out of the gut into the tissues of the liver, kidney and even the brain, the team found. The study also showed the microplastics changed metabolic pathways in the affected tissues.

“We could detect microplastics in certain tissues after the exposure,” Castillo says. “That tells us it can cross the intestinal barrier and infiltrate into other tissues.”

Castillo says he’s also concerned about the accumulation of the plastic particles in the human body. “These mice were exposed for four weeks,” he says. “Now, think about how that equates to humans, if we’re exposed from birth to old age.”

The healthy laboratory animals used in this study showed changes after brief microplastic exposure, Castillo says. “Now imagine if someone has an underlying condition, and these changes occur, could microplastic exposure exacerbate an underlying condition?”

He has previously found that microplastics are also impacting macrophages – the immune cells that work to protect the body from foreign particles.

In a paper published in the journal Cell Biology & Toxicology in 2021, Castillo and other UNM researchers found that when macrophages encountered and ingested microplastics, their function was altered and they released inflammatory molecules.

“It is changing the metabolism of the cells, which can alter inflammatory responses,” Castillo says. “During intestinal inflammation – states of chronic illness such as ulcerative colitis and Crohn’s disease, which are both forms of inflammatory bowel disease – these macrophages become more inflammatory and they’re more abundant in the gut.”

The next phase of Castillo’s research, which is being led by postdoctoral fellow Sumira Phatak, PhD, will explore how diet is involved in microplastic uptake. 

“Everyone’s diet is different,” he says. “So, what we’re going to do is give these laboratory animals a high-cholesterol/high-fat diet, or high-fiber diet, and they will be either exposed or not exposed to microplastics. The goal is to try to understand if diet affects the uptake of microplastics into our body.”

Castillo says one of his PhD students, Aaron Romero, is also working to understand why there is a change in the gut microbiota. “Multiple groups have shown microplastics change the microbiota, but how it changes the microbiota hasn’t been addressed.”

Castillo hopes that his research will help uncover the potential impacts microplastics are having to human health and that it will help spur changes to how society produces and filtrates plastics.

“At the end of the day, the research we are trying to do aims to find out how this is impacting gut health,” he says.

“Research continues to show the importance of gut health. If you don’t have a healthy gut, it affects the brain, it affects the liver and so many other tissues. So even imagining that the microplastics are doing something in the in the gut, that chronic exposure could lead to systemic effects.”

About this neuroscience research news

Author: Steve Carr
Source: University of New Mexico
Contact: Steve Carr – University of New Mexico
Image: The image is credited to Neuroscience News

Original Research: Open access.
In Vivo Tissue Distribution of Polystyrene or Mixed Polymer Microspheres and Metabolomic Analysis after Oral Exposure in Mice” by Eliseo Castillo et al. Environmental Health Perspectives


In Vivo Tissue Distribution of Polystyrene or Mixed Polymer Microspheres and Metabolomic Analysis after Oral Exposure in Mice


Global plastic use has consistently increased over the past century with several different types of plastics now being produced. Much of these plastics end up in oceans or landfills leading to a substantial accumulation of plastics in the environment. Plastic debris slowly degrades into microplastics (MPs) that can ultimately be inhaled or ingested by both animals and humans. A growing body of evidence indicates that MPs can cross the gut barrier and enter into the lymphatic and systemic circulation leading to accumulation in tissues such as the lungs, liver, kidney, and brain. The impacts of mixed MPs exposure on tissue function through metabolism remains largely unexplored.


This study aims to investigate the impacts of polymer microspheres on tissue metabolism in mice by assessing the microspheres ability to translocate across the gut barrier and enter into systemic circulation. Specifically, we wanted to examine microsphere accumulation in different organ systems, identify concentration-dependent metabolic changes, and evaluate the effects of mixed microsphere exposures on health outcomes.


To investigate the impact of ingested microspheres on target metabolic pathways, mice were exposed to either polystyrene (μ5μm) microspheres or a mixture of polymer microspheres consisting of polystyrene (μ5μm), polyethylene (μ1–4μm), and the biodegradability and biocompatible plastic, poly-(lactic-co-glycolic acid) (μ5μm). Exposures were performed twice a week for 4 weeks at a concentration of either 0, 2, or 4mg/week via oral gastric gavage. Tissues were collected to examine microsphere ingress and changes in metabolites.


In mice that ingested microspheres, we detected polystyrene microspheres in distant tissues including the brain, liver, and kidney. Additionally, we report on the metabolic differences that occurred in the colon, liver, and brain, which showed differential responses that were dependent on concentration and type of microsphere exposure.


This study uses a mouse model to provide critical insight into the potential health implications of the pervasive issue of plastic pollution. These findings demonstrate that orally consumed polystyrene or mixed polymer microspheres can accumulate in tissues such as the brain, liver, and kidney. Furthermore, this study highlights concentration-dependent and polymer type-specific metabolic changes in the colon, liver, and brain after plastic microsphere exposure. These results underline the mobility within and between biological tissues of MPs after exposure and emphasize the importance of understanding their metabolic impact. https://doi.org/10.1289/EHP13435

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