Microplastics in arterial plaque linked to 4.5x higher cardiovascular risk

In a Naples hospital, surgeons opened the carotid arteries of 257 patients to clear away the fatty buildup that was choking off blood flow to their brains. What they found when they examined the scraped plaque under an electron microscope was unexpected: jagged fragments of polyethylene and polyvinyl chloride—the same plastics used in grocery bags, food containers, and water pipes—embedded in the arterial walls of 150 of those patients. Over the next 34 months, those 150 patients suffered heart attacks, strokes, and death at a rate 4.5 times higher than the patients whose plaque remained plastic-free.

Raffaele Marfella and his team at the University of Campania had launched a straightforward investigation. They recruited patients already scheduled for carotid endarterectomy, a routine procedure to clear plaque from the neck arteries, and asked a simple question: would the debris they removed contain any of the microplastic contamination that researchers had recently begun documenting in oceans, soil, and human blood? They expected to find some traces. They were not prepared to find plastic in 58 percent of their patients. And the follow-up numbers shocked them further. Among the 150 patients with microplastics lodged in their plaque, 30 went on to have a heart attack, a non-fatal stroke, or died from any cause within 34 months of surgery. Among the 107 patients whose plaque was clean, only eight experienced such events. The hazard ratio of 4.53 survived adjustment for age, sex, smoking, diabetes, cholesterol, blood pressure, and every other cardiovascular risk factor the researchers tested. In cardiology, an effect size of that magnitude typically attaches to things like uncontrolled high blood pressure or a strong family history of early heart disease—not to a substance most doctors had long considered biologically inert.

The mechanism appears to follow the same pathway that atherosclerosis already travels. Arterial plaque begins when the endothelium, the single-cell lining that separates blood from the vessel wall, begins to fail. Low-density lipoprotein particles slip through, become oxidized, and trigger monocytes to transform into macrophages that gorge themselves on lipid until they become foam cells. When these foam cells die, their debris forms a necrotic core. A fibrous cap grows over it. When that cap thins and ruptures, the contents spill into the bloodstream and a clot forms—which is what a heart attack or stroke mechanically is. Nanoplastic particles, being smaller than a single cell, appear to slip through the endothelium the same way LDL does. Once inside the arterial wall, they seem to intensify the inflammatory response, recruiting more macrophages, driving more foam cell death, and thinning the fibrous cap. Marfella's team found that patients with microplastics in their plaque had elevated levels of inflammatory markers including interleukin-18 and tumor necrosis factor-alpha, both known to destabilize arterial walls. The plastic was not causing atherosclerosis from scratch. It was accelerating a disease process already underway.

The obvious question after any single study is whether other researchers can replicate the findings. In April 2025, Ross Clark, a vascular surgeon-scientist at the University of New Mexico, presented data at the American Heart Association's Vascular Discovery Scientific Sessions in Baltimore. His team had built on the Italian work with a smaller cohort of fewer than 50 patients, comparing three groups: people with healthy carotid arteries, people with plaque but no symptoms, and people who had already suffered a stroke or transient vision loss. The gradient was striking. Plaque from symptomatic patients contained roughly 51 times more micronanoplastic material than the arteries of healthy controls. Plaque from asymptomatic patients fell somewhere in between. Karen Furie, chair of neurology at Brown University's Warren Alpert Medical School, noted that plastic exposure has not traditionally been considered a modifiable stroke risk factor, and suggested the finding could open a new avenue for stroke prevention research. Clark himself remained cautious. His team's method—pyrolysis gas chromatography-mass spectrometry—burns tissue samples down to their molecular signatures, and lipids in arterial plaque can produce signatures that resemble polyethylene. He acknowledged that future discoveries could alter how researchers interpret these findings.

Plastic particles have now been documented in human blood, breast milk, placental tissue, testicular tissue, and brain tissue. A February 2026 study found microplastics in nine out of ten prostate cancer tumors examined, at higher concentrations in cancerous tissue than in adjacent healthy tissue. The pattern—plastic showing up preferentially in diseased tissue across multiple organ systems—is the signal that keeps triggering new research funding. Clark noted in Baltimore that consumers often mistakenly believe microplastics come primarily from direct contact with plastic items like utensils and packaging. In reality, the particles are already present in food and water supplies before packaging ever touches them.

Cardiovascular disease remains a leading cause of death worldwide. The field has spent four decades identifying modifiable risk factors—smoking, LDL cholesterol, hypertension, diabetes, obesity, sedentary behavior—and building interventions around each one. A new modifiable risk factor with a hazard ratio above 4 is not a minor addition to the list. It is a rewriting of it. The problem is that nobody yet knows what a clinical intervention would look like. You cannot prescribe less plastic the way you prescribe less salt. Regulatory action on plastic production is negotiated at international levels, but binding agreements on production caps remain elusive. The petrochemical industry has resisted upstream limits and pushed the conversation toward recycling and waste management instead. Meanwhile, plaque keeps forming, and now it keeps forming with plastic inside it.

The honest scientific position in 2026 is that association is not causation and 257 patients from a single Italian hospital is not a global cohort. It is possible that microplastics in plaque are a marker of some other exposure doing the actual harm—the fingerprint at the crime scene rather than the weapon. What has changed is the burden of proof. For decades, the assumption behind consumer plastic—that it was inert, that it passed through, that whatever fragments stuck around were biologically irrelevant—sat on no particular evidence base. It was simply the default. That default is now being tested against tissue samples, and the tissue samples keep failing to cooperate. The Marfella paper triggered a wave of follow-up research still being funded and staffed. Clark's team is working on the immunology of how macrophages behave in plaques with high plastic loads. Groups in South Korea, Germany, and the Netherlands have started their own carotid tissue studies. If the hazard ratio holds through longer follow-up, the case for classifying micronanoplastic exposure as a cardiovascular risk factor will move from tentative to conventional. If it collapses, the field will retreat. Neither outcome changes what is already true about the 150 patients whose plaque contained plastic. Something got inside them. It found a place to settle. It is still there.