Microplastics in Arterial Plaques May Be Linked to Heart Risks

Plastic is now ubiquitous, and minute fragments have been detected in several major organs in the human body, including the placenta.

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

Scientists have been examining the effects of microplastics in miniature organ models and in mice to understand their potential effects on the human body. Yet the concentrations used in these experiments may not mirror real-world human exposure, while research involving people remains limited.

Microplastics in arterial plaques

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

Removing fatty plaques from constricted arteries through a procedure known as carotid endarterectomy lowers the risk of subsequent strokes.

The researchers behind the new study, headed by Raffaele Marfella, a medical researcher at the University of Campania in Naples, investigated whether the risks of stroke, heart attack and death differed between patients whose plaques contained microplastics and those whose plaques did not.

Over 34 months of follow-up involving 257 patients, almost 60 percent had measurable 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 rigid and flexible forms and is used in water pipes, plastic bottles, flooring and packaging. Polyethylene, the most widely manufactured plastic, is also used for plastic bags, films and bottles.

Heart health and microplastic exposure

As microplastics have previously been found circulating in people's bloodstreams, the researchers had understandable concerns about cardiovascular health. Laboratory studies indicate that microplastics may provoke inflammation and oxidative stress in heart cells and, in animals including mice, disrupt heart function, change heart rate and lead to cardiac scarring.

"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, patients whose removed plaques contained microplastics were 4.5 times as likely to have had a stroke, a non-fatal heart attack or died from any cause as those with no detectable microplastics in the plaques surgeons removed.

The quantities of microplastics and still smaller particles known as nanoplastics were assessed with pyrolysis–gas chromatography–mass spectrometry. Their presence was then verified through stable isotopes analysis, which distinguishes carbon in human tissue from carbon in petrochemical-derived plastics.

High-powered microscopes also revealed microplastics: the team saw jagged plastic fragments within immune cells known as macrophages and inside the fatty plaques. Tissue analysis further showed elevated levels of inflammatory markers among patients whose plaques contained microplastics.

It is important to note, though, that an observational study of this kind cannot establish definitively that microplastics cause the later heart-related effects; it can only show an association. The research also did not account for other cardiovascular disease risk factors, including smoking, physical inactivity and air pollution.

"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.

Plastic production has surged over the past two decades, with only a small proportion recycled. However, cardiovascular disease rates have declined in some 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 originally published in March 2024.