An ‘Epidemiologic Nightmare’: Microplastics and GI Health

This transcript has been edited for clarity.

Hello. I’m Dr David Johnson, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia. 

Plastics are a daily part of our lives that we use all the time. We have a plastic water bottle in our hand when we travel, we cook with plastics, our groceries come wrapped in plastics, and our food gets heated up in plastic containers. This speaks to the incredible growth in plastic production over the past seven decades, stretching back to the 1950s, during which it’s estimated that approximately 9 billion tons of plastic have been produced.

We may think we’re addressing this through recycling. Although this sounds good in theory, it’s estimated that only about 10% of plastic actually gets recycled. Much of our unrecycled plastic instead gets dumped in unregulated land sites or into water or gets burned and aerosolized. With its subsequent degradation or upregulation, plastic becomes a composite of the air, water, and soil. 

Plastics are found in a variety of textiles, the dynamics of which are altered by chemical weathering, transferring them further into the environment. Furthermore, plastic microbeads are routinely used in medicines, cosmetics, personal care products, abrasives, and in 3D-printing powder. 

As such, plastics are routinely ingested by and progressively infiltrate virtually all lifeforms on the planet. In fact, it’s estimated that the average American currently ingests the equivalent of 5 grams of plastic — roughly the mass of a credit card — once a week. You can breathe it in through aerosolization and you can ingest it, although there’s not much risk from dermatologic exposure. 

Plastics are categorized as microplastics when they’re < 5 mm in size, which is something we can generally see, and nanoplastics when they’re < 1 μm in size, which you obviously can’t see. Histologically, detecting nanoplastics requires spectroscopy or some type of fluorescent micrologic analysis, meaning they won’t be found in your routine pathology report. 

The Effects of Ingesting Plastics 

As covered in a 2024 review article, ingested plastics accumulate in the gastrointestinal (GI) and pulmonary tracts, where they exhibit inflammatory properties. The authors noted that multiple animal studies conducted in a variety of nematodes and fish models have shown that microplastics have a dramatic effect on gut dysbiosis. In humans, they decrease the Bacteroidetes phylum, which is the anti-inflammatory phylum we also see decreased in inflammatory bowel disease. Basically, ingestion of plastics increases dysbiosis and decreases diversity, setting up an imbalance in your GI tract. 

Animal studies have also consistently shown that microplastics cause dramatic changes to gut integrity. The intestinal barriers are reduced, leading to downregulated expression of tight junction proteins like claudin, zonulin, or occludin. This allows for translocation of bacteria, the plastics themselves, or the microbiome’s metabolites, not only through the intestinal wall but also throughout virtually every organ in your body. Numerous studies have now shown that these plastic nanoparticles can be found anywhere in the body, including the brain. 

Plastic exposure is highly disruptive. Inflammatory cytokines that are upregulated as a result include tumor necrosis factor‒alpha, interleukin-6, and others that change gut integrity, as well as blood-brain barrier integrity. 

Emerging Disease Associations

What does this all mean in terms of disease? These plastics are not invoking cell death, but they are certainly changing cell structure and cell function. Multiple cellular analyses and in vivo studies have repeatedly shown the negative biological toll of microplastic exposure. 

One recent study that caught my eye due to its striking results appeared in The New England Journal of Medicine. Researchers enrolled 304 patients undergoing a carotid endarterectomy for asymptomatic carotid artery disease, whose excised carotid plague was then analyzed. Of these patients, 150 (58%) had nanoplastics identified in their plaque. These patients had a hazard ratio of having an associated cardiac event, stroke, or death of any cause approximately 4.5 times greater than those without nanoplastics detected in their plaque. 

In terms of GI diseases, given that these plastics change gut integrity, upregulate a variety of cytokines, and decrease biome diversity and Bacteroides phylum, it makes sense that there’s an emerging association with inflammatory bowel disease. Beyond animal studies, there are some longitudinal studies conducted in humans showing an increased likelihood of these nanoparticles being identified in patients with inflammatory bowel disease. 

A recent animal model study showed that the ingestion of nanoplastics was able to produce a Crohn’s disease–like illness in a mouse. This was provoked in mice orally exposed to nanoplastics, but not in the control population without such exposure. 

There’s also evidence suggesting a link with liver disease. This includes a recent experimental animal study providing evidence of a strong association between microplastic exposure and the development of metabolic dysfunction–associated steatotic liver disease. A very recent review looked at the methodologic reasons why this makes sense, which shows that nanoparticles get transported to the portal vein and induce various cytokine upregulations in the liver.

A retrospective, comparative cohort analysis looked at liver biopsies obtained from patients with cirrhosis. It showed that significant nanoparticle deposition was evident in those with cirrhosis, as opposed to none of the patients without underlying liver disease. 

What Can Be Done?

This is a potential epidemiologic nightmare. The environmental risk is explosive and continues at incremental rates. It’s estimated that by 2050, the annual production of plastics will exceed 1.1 billion tons per year. 

There are some directives being put in place to combat this.

In late 2023, the European Union passed a chemical legislation measure to block or restrict microplastics being added to products. When considering the scale of this measure, keep in mind that they are present in virtually everything we see— medications, cosmetics, etc. Additionally, the United Nations Environment Assembly approved an agreement in 2024 to investigate ways to potentially make and enforce policies related to exposures to nanoplastics and microplastics in humans. 

In terms of what we can do ourselves, making clinicians and patients aware of this issue is a good first step. 

Mitigation strategies can include things like reducing your exposure to plastic in consumptive forms (eg, water bottles, cooking materials), improving management practices around how plastics are processed and ultimately dealt with as they’re dumped back into the environment, and looking at ways that we can limit plastics in consumer products and developing biodegradable alternatives. 

Although we need longitudinal scientific studies to further corroborate the adverse health effects of microplastics and nanoplastics, I think the scientific evidence thus far has some striking implications. I believe it’s real. How far we go with this and its implications are yet to be defined. Nonetheless, we should be on high alert. 

Nanoplastics are something that we need to consider, particularly in GI as well as virtually all other disease states. The evidence is yet to be determined, but it’s very alarming at this point. 

Please consider this as you talk with your patients and when thinking about your own personal health. 

I’m Dr David Johnson. Thanks for listening.

David A. Johnson, MD, a regular contributor to Medscape, is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia, and a past president of the American College of Gastroenterology. His primary focus is the clinical practice of gastroenterology. He has published extensively in the internal medicine/gastroenterology literature, with principal research interests in esophageal and colon disease, and more recently in sleep and microbiome effects on gastrointestinal health and disease.