Higher levels of micronanoplastics were found in carotid artery plaque, especially in people with stroke symptoms, suggesting a potential new risk factor.

People with plaque buildup in the arteries of their neck have been found to carry higher concentrations of tiny plastic particles within those blood vessels compared to individuals with healthy arteries. This difference was even more pronounced among patients who had suffered a stroke, mini-stroke (also known as a transient ischemic attack), or temporary vision loss due to vascular blockages. These findings come from preliminary research recently presented at the American Heart Association's Vascular Discovery 2025 Scientific Sessions: From Genes to Medicine, held April 22–25 in Baltimore.

Micronanoplastics are extremely small plastic fragments either produced during industrial processes or formed as larger plastic debris breaks down in the environment, such as in oceans and soils. They encompass a mixture of sizes:

  • Microplastics: Typically less than 5 millimeters across (about the size of a pencil eraser) and sometimes visible to the naked eye.
  • Nanoplastics: Far smaller, measuring under 1,000 nanometers, and invisible without a microscope.

Because of their minute size, nanoplastics can disperse more widely in the environment and penetrate cells and tissues within living organisms more easily than larger plastic particles.

Researchers are increasingly advocating for a shift in terminology from "micronanoplastics" to simply "nanoplastics," to better reflect the smaller, more biologically active particles that are the primary focus of ongoing studies.

Sources and Environmental Impact

"These types of plastics are commonly found in the environment, especially in ocean garbage patches. Over many years, these plastics break down, mix into the soil and water, and can build up in the food chain," said lead study author Ross Clark, M.D., M.B.A., R.P.V.I., a vascular surgeon-scientist at the University of New Mexico in Albuquerque. "Many people think that micro and nanoplastics mainly come from using plastic utensils, cutting boards, packaging, water bottles, and other plastic items. However, the main source is the food and water we eat and drink."

In 2024, researchers in Italy reported finding micronanoplastics in plaque from some people without symptoms who underwent surgery to remove carotid artery plaque. Symptoms caused by carotid plaque buildup may include stroke, mini-stroke, or temporary blindness. Followed for almost three years after surgery, people with micronanoplastics in their carotid plaque were significantly more likely to die or to have a non-fatal heart attack or stroke.

The Current Study: Building on Previous Work

The current study, which included fewer than 50 participants, was built on the previous research conducted in Italy. Researchers compared the levels of micronanoplastics found in the carotid arteries of three groups: people with healthy arteries; those with plaque but no symptoms; and those experiencing symptoms due to plaque buildup. Researchers also compared plaques with low and high plastic levels to assess the effects of micronanoplastics on markers of inflammation, the gene activity of immune cells called macrophages and stem cells that help stabilize plaque.

The analysis found that the concentration of micronanoplastics in carotid arteries was:

  • 16 times higher (895 micrograms/gram vs. 57 micrograms/gram) in plaque among people without symptoms compared to the levels found in artery walls of deceased tissue donors of similar age with no plaque; and
  • 51 times higher (2,888 micrograms/gram vs. 57 micrograms/gram) in plaque from people who had experienced stroke, mini-stroke, or temporary loss of vision due to blockage of blood flow to the retina, in comparison to samples from age-matched, deceased tissue donors.

Comparing high-plastic and low-plastic plaque levels, the analysis found:

  • no link between the amount of micronanoplastics and signs of sudden inflammation; and
  • differences in gene activity in plaque-stabilizing cells and less activity in anti-inflammatory genes of plaque macrophage immune cells.

"These findings indicate that the biological effects of micronanoplastics on fatty deposits are more complex and nuanced than simply causing sudden inflammation," Clark said. In their next phase of work, they will focus on better understanding the immunological effects of micronanoplastics in clogged arteries.

Caution and Study Limitations

"It's very important to study what these materials do to our bodies. However, we should be cautious about the early results of this study. We won't fully understand the biological effects for many years to come," Clark said.

The study has several limitations. It cannot prove that micronanoplastics in plaque were the cause of symptoms of carotid artery disease; micronanoplastics might be a sign of another health issue that caused these symptoms. Researchers did not have access to data detailing the sex or race/ethnicity of the tissue donors. Additionally, pyrolysis gas chromatography-mass spectrometry, used to measure plastic in biological samples may have limitations. This technique allows measurements to include nanoplastics and larger microplastic particles and uses high temperatures to break down plastics into smaller organic molecules. However, parts of the biological samples may also break down into similar molecules. For instance, fatty acids found in artery-clogging plaque could break down into compounds appearing similar to polyethylene.

"We are constantly improving our method to reduce the amounts of lipids in the samples to lessen their impact on the results. Lipids have a very similar spectral signature on gas chromatography as some plastic polymers (in particular polyethylene). It can be challenging to distinguish between the lipids and the polyethylene in the results. That's why removing the lipids is so important. We believe our methods are currently the best way to address this specific criticism. However, new discoveries might change how we understand this data in the future," Clark said.

"This is a very interesting and troubling study. To date, we have not considered exposure to plastic micronanoparticles a modifiable risk factor for stroke. Although it is important to understand the mechanism at play in the pathophysiology of symptomatic carotid atherosclerosis, this association presents a novel potential target for stroke prevention," said Karen L. Furie, M.D., M.P.H., FAHA, volunteer vice chair of the American Heart Association Stroke Brain Health Science Subcommittee and professor and chair of neurology at the Warren Alpert Medical School of Brown University in Providence, Rhode Island. Furie was not involved in this study.

Study details, background, and design

  • Researchers tested 48 samples of carotid arteries from 48 different adults collected in 2023-2024 at the University of New Mexico and the Office of the Medical Investigator (a state agency and part of the Department of Pathology at the University of New Mexico).
  • About one-third of the samples were from people aged 60 to 90 who had surgery to remove plaque from their carotid arteries. These people had symptoms including stroke, mini-stroke or temporary blindness (called amaurosis fugax).
  • About one-third of the samples came from people of similar age with no symptoms. They were having surgery to remove plaque buildup in their carotid arteries because a blockage was found during screening or a physical exam.
  • The last one-third of the samples came from tissue donors. These age-matched donors had died of any cause and did not have carotid artery blockage.
  • The researchers also compared plaques with low vs. high amounts of micronanoplastics on inflammation-related measures. All samples were analyzed to measure inflammation by looking at levels of inflammatory molecules TNF-α and IL-6. The levels were compared to the amount of plastics to find any connections. For the RNA sequencing studies, researchers examined samples with the highest and lowest concentrations of plastics.
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