Microplastics in Artery Plaques Linked to Higher Stroke and Heart Attack Risk

Plastics have become ubiquitous, and minute particles have been detected in several key organs of the human body, placenta included.

Because these microscopic particles can so readily enter our tissues, establishing precisely what health risks they may present is essential.

Scientists have investigated microplastics in miniature organ models and in mice to understand their possible effects on the human body. Yet the microplastic levels used in such research may not mirror real-world human exposure, while human studies remain scarce.

Microplastics found in artery plaques

In March, a small Italian study detected microplastic fragments in fatty deposits removed surgically from patients undergoing an operation to clear their blocked arteries, then tracked their health outcomes for almost 3 years.

Watch the clip below for an overview of its findings:

A procedure known as carotid endarterectomy removes fatty plaques from narrowed arteries, helping to lower the risk of later strokes.

The researchers behind the recent work, headed by University of Campania medical researcher Raffaele Marfella in Naples, sought to compare the chances of stroke, heart attack and death in patients whose plaques contained microplastics with those whose plaques did not.

Over 34 months of follow-up involving 257 patients, nearly 60 percent had detectable polyethylene in plaques removed from their fat-thickened arteries. A further 12 percent had polyvinyl chloride (PVC) in the extracted fatty deposits.

PVC is available in both rigid and flexible types, and is used in water pipes, plastic bottles, flooring and packaging. Polyethylene, meanwhile, is the most widely manufactured plastic and is also used for plastic bags, films and bottles.

Potential cardiovascular effects of microplastics

As earlier research had found microplastics circulating in people’s bloodstreams, the team had reasonable concerns about their implications for heart health.

Laboratory studies indicate that microplastics may provoke inflammation and oxidative stress in heart cells, reduce heart function, change heart rate and lead to heart scarring in animals including mice.

"Observational data from occupational-exposure studies [also] suggest an increased risk of cardiovascular disease among persons who are exposed to plastics-related pollution, including polyvinyl chloride, than that seen in the general population," Marfella and colleagues write.

After 34 months, those with microplastics in their removed plaques were 4.5 times more likely to have had a stroke, a non-fatal heart attack or died from any cause than patients with no detectable microplastics in the plaques removed by surgeons.

Researchers quantified microplastics and the still smaller particles known as nanoplastics with pyrolysis–gas chromatography–mass spectrometry. They confirmed their presence through stable isotopes analysis, another technique that can differentiate carbon in human tissue from carbon in plastics produced from petrochemicals.

Inflammation and the study’s limitations

The microplastics could also be seen using high-powered microscopes. The researchers identified sharply edged plastic pieces inside macrophages, which are immune cells, as well as within the fatty plaques. Tissue analysis further showed increased levels of inflammatory markers in patients whose plaques contained microplastics.

It is important to note, though, that an observational study of this kind cannot establish that microplastics cause subsequent heart-related effects; it can show only an association. Other cardiovascular disease risk factors, including smoking, physical inactivity and air pollution, were not assessed by the study.

"Although we do not know what other exposures may have contributed to the adverse outcomes among 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," such as how to reduce exposure, explained paediatrician, public health physician and epidemiologist Philip J. Landrigan, of Boston College, in an accompanying editorial.

Over the past two decades, plastic production has surged, with only a small share recycled. However, cardiovascular disease rates have declined in certain regions of the world, meaning further research is required to clarify the relationship between the two.

The study was published in The New England Journal of Medicine.

A version of this article was first published in March 2024.