Microplastics migrate from the gut to other organs

Every day, microplastics are making their way into our bodies through water, food, and even the air we breathe. Researchers led by the University of New Mexico (UNM) has explored the impact of microplastics on the human digestive system and organs including the kidney, liver, and brain.

“Over the past few decades, microplastics have been found in the ocean, in animals and plants, in tap water and bottled water. They appear to be everywhere,” said Eliseo Castillo, an expert in mucosal immunology at UNM.

Microplastics in organ tissues

Experts estimate that the average person ingests about five grams of microplastics each week – the equivalent of the weight of a credit card. While many studies have focused on identifying and quantifying these particles, Castillo’s team is investigating their internal effects, particularly on the gastrointestinal (GI) tract and the gut immune system.

In their experiments, mice were exposed to microplastics through their drinking water over a four-week period, mirroring the estimated weekly microplastic intake of humans. The results were alarming: microplastics not only migrated from the gut into the tissues of the liver, kidney, and brain but also altered metabolic pathways within these organs.

Microplastics can cross the intestinal barrier 

“We could detect microplastics in certain tissues after the exposure. That tells us it can cross the intestinal barrier and infiltrate into other tissues,” Castillo said. “These mice were exposed for four weeks. Now, think about how that equates to humans, if we’re exposed from birth to old age.”

The study also raises concerns about the potential for microplastics to exacerbate underlying health conditions. Castillo’s earlier research has shown that microplastics impact macrophages – the immune cells that protect the body from foreign particles. For instance, a 2021 study published in the journal Cell Biology and Toxicology revealed that microplastics alter macrophage function, triggering them to release inflammatory molecules.

“It is changing the metabolism of the cells, which can alter inflammatory responses. 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,” Castillo explained.

How does diet influence microplastic intake? 

Looking ahead, Castillo’s team, including postdoctoral fellow Sumira Phatak, is set to explore how diet influences microplastic uptake. They plan to experiment with different diets in laboratory animals to see if certain foods affect the body’s absorption of microplastics.

“Everyone’s diet is different. 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 added.

Changes in gut microbiota 

Moreover, Castillo’s PhD student, Aaron Romero, is investigating changes in the gut microbiota caused by microplastics. While it’s known that microplastics can alter the microbiota, the mechanisms behind these changes remain unclear.

Ultimately, the experts hope that these findings will not only deepen our understanding of the health impacts of microplastics but also catalyze changes in how plastics are produced and managed. 

“At the end of the day, the research we are trying to do aims to find out how this is impacting gut health. 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 gut, that chronic exposure could lead to systemic effects,” Castillo concluded.

Health impacts associated with microplastic ingestion

The extent and severity of health risks associated with microplastic exposure are still under investigation. More research is needed to determine the precise implications and to understand the mechanisms through which microplastics can affect human health. Here are some of the potential impacts:

Physical damage

Microplastics can cause physical damage to tissues, especially if they are sharp or angular. They may irritate or perforate the tissues of the digestive tract.

Chemical exposure

Microplastics can carry pollutants, including toxic chemicals like heavy metals, polychlorinated biphenyls (PCBs), and bisphenol A (BPA), which can leach into the body. These substances are known to have carcinogenic, developmental, and endocrine-disrupting effects.

Inflammation and immune response

There is evidence that microplastics can trigger inflammatory responses or affect the immune system. Small particles can be mistaken by the body as harmful invaders, leading to an immune response.

Potential for bioaccumulation

Microplastics might accumulate in the body and organs over time, especially since they are not biodegradable. The long-term health effects of this accumulation are not yet fully understood.

Effects on gut health

Research has suggested that microplastics can affect the gut microbiota, potentially leading to gastrointestinal issues or impacting nutrient absorption.

The study is published in the journal Environmental Health Perspectives.

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