Of all the reasons you could name that might cause a heart attack or stroke, would you classify microplastic infection as one? Well, some recently published research suggests it’s a strong possibility.

If you’re not familiar with it already, microplastic infection is all about tiny particles of plastic (less than 5 millimetres) entering and infiltrating living organisms and their respective ecosystems. Their inadvertent release and persistent nature have led to widespread distribution across land-based and marine food systems.

The Plastic Soup Foundation explains it like this: Animals carry microplastics in their bodies. When they are themselves eaten, those microplastics are also ingested. This process is called ‘trophic transfer’ of microplastics. Since one animal eats another, microplastics can move through the food chain. It also notes that “the signals that plastic is harming our health are now gathering strength.”

A group of Italian researchers would most likely agree.

Higher risk of death

About a week ago, they released findings showing that patients with carotid artery plaque, in which microplastics and nanoplastics were detected, had a higher risk for death or major cardiovascular events than those with plaques where particles were not found.

This is the first study to show plastic particles are present in atheroma plaques, but the most important finding is that this was related to a four times higher risk for cardiovascular events, study co-author Antonio Ceriello, MD, IRCCS MultiMedica, Milan, told theheart.org.

“I believe we have demonstrated that plastics are a new risk factor for cardiovascular disease,” he added. And while plastics may have made our lives easier in many respects, it appears that the price we are paying for that is a shortening of our lives. That is not a good balance.”

The trial involved 304 patients undergoing carotid endarterectomy for asymptomatic carotid artery disease, whose excised plaque specimens were analyzed for the presence of microplastics and nanoplastics, ultimately found in almost 60% of patients.

After a mean follow-up of 34 months, patients in whom microplastics and nanoplastics were detected within the atheroma had a 4.5 times higher risk for the composite endpoint of all cause death, myocardial infarction, or stroke than those in whom these substances were not detected (hazard ratio, 4.53; 95% CI, 2.00-10.27; P < .001).

The study, led by Raffaele Marfella, MD, University of Campania Luigi Vanvitelli, Naples, Italy, was published in The New England Journal of Medicine on March 7, 2024.

Although important risk factors such as diabetes, hypertension, and dyslipidemia were controlled for, researchers have warned that “many other unmeasured confounding factors” could have contributed to the findings, so the study does not prove causality.

High-risk patients

“In this study, all the patients involved were at high risk of cardiovascular events, and they were well treated with statins and antithrombotics, so the relationship between the presence of plastic particles in plaque and cardiovascular events is seen on top of good preventive therapy,” he said.

“While we cannot say for sure that we have shown a causal relationship, we found a large effect, and there is a great deal of literature that supports this. We know that plastic particles can penetrate cells and act at the mitochondrial level to increase free radical production and produce chronic inflammation, which is the basis for atherosclerosis,” Ceriello added.

Commenting for theheart.org | Medscape Cardiology, Philip Landrigan, MD, author of an editorial accompanying the study’s publication in the NEJM, described the link as “strongly suggestive.”

“Because this was just a single observational study, it doesn’t prove cause and effect, but I think this is strongly suggestive of a causal relationship,” he said. “While there may be some other confounding factors at play, it is hard for me to imagine that these could account for a hazard ratio of 4.5 — that is a large and alarming increase in just three years.”

A breakthrough discovery

Landrigan, who is director of the Program for Global Public Health and the Common Good, Boston College, points out that although it is not known what other exposures may have contributed to the adverse outcomes in patients in this study, the finding of microplastics and nanoplastics in plaque tissue is itself a breakthrough discovery that raises a series of urgent questions.

These include: “Should exposure to microplastics and nanoplastics be considered a cardiovascular risk factor? What organs, in addition to the heart, may be at risk? How can we reduce exposure?”

Landrigan said he was not surprised that plastic particles had been found in carotid plaques.

“Previous studies have found microplastics in other tissues, including the lungs, colon and placenta. Now they have turned up in the vessel wall,” he said. “But what is really striking about this study is that it suggests the presence of these plastic particles is causing serious harm.”