Microplastics in Arterial Plaques Linked to Higher Heart Risks

Plastics have become ubiquitous, and minute particles have been detected in several of the body’s principal organs, including the placenta.

Because these microscopic particles can so readily enter human tissue, establishing precisely what danger they may present to health is essential.

Scientists have been investigating the effects of microplastics in miniature organ models and in mice to understand their potential consequences for the human body. Yet the microplastic concentrations used in these experiments may not match the exposure people experience in everyday life, and human studies remain limited.

Microplastics in arterial plaques

In March, a small Italian study identified microplastic fragments in fatty deposits surgically removed 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 the findings:

Removing fatty plaque from narrowed arteries through a procedure known as a carotid endarterectomy lowers the likelihood of subsequent strokes.

The researchers behind the new study, led by medical researcher Raffaele Marfella of the University of Campania in Naples, set out to compare the risk of stroke, heart attack and death in patients whose plaques contained microplastics with that in those whose plaques did not.

Over 34 months of follow-up involving 257 patients, the team found that almost 60 percent had measurable polyethylene in plaques taken from their fat-thickened arteries. A further 12 percent had polyvinyl chloride (PVC) in the removed fatty deposits.

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

As microplastics had previously been found circulating in human blood, the researchers had understandable concerns about their implications for heart health.

Laboratory research indicates that microplastics may provoke inflammation and oxidative stress in heart cells, disrupt cardiac function, change heart rate and produce 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.

Heart risks linked with microplastics

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

Researchers measured microplastics and even smaller particles known as nanoplastics with pyrolysis–gas chromatography–mass spectrometry. They confirmed their presence with stable isotope analysis, a separate technique able to tell the carbon in human tissue apart from the carbon in petrochemical-derived plastics.

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

Limits of the Italian study

It is important to note that an observational study of this kind cannot establish conclusively that microplastics cause later heart-related effects; it can identify only 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 pediatrician, public health physician and epidemiologist Philip J. Landrigan, of Boston College, in an accompanying editorial.

Plastic production has risen dramatically over the past two decades, while only a small proportion has been recycled. However, cardiovascular disease rates have declined in certain parts 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.