Patients with microplastics and nanoplastics (MNPs) in their carotid arteries may face a heightened risk of heart attack or stroke, according to new data published in the New England Journal of Medicine.[1]
While microplastics are smaller than 5 mm, researchers explained, nanoplastics are smaller than 1000 nanometers.
“Several studies have shown that MNPs enter the human body through ingestion, inhalation, and skin exposure, where they interact with tissues and organs,” wrote first author Raffaele Marfella, MD, PhD, a professor with the University of Campania Luigi Vanvitelli in Italy, and colleagues. “MNPs have been found in selected human tissues, such as the placenta, lungs, and liver as well as in breast milk, urine and blood. Recent studies performed in preclinical models have led to the suggestion of MNPs as a new risk factor for cardiovascular diseases. Data from in vitro studies suggest that specific MNPs promote oxidative stress, inflammation, and apoptosis in endothelial and other vascular cells; animal models support a role for MNPs in altered heart rate, cardiac-function impairment, myocardial fibrosis, and endothelial dysfunction.”
Marfella et al. explored carotid plaque specimens from more than 300 patients with asymptomatic high-grade carotid artery stenosis. All patients were treated at one of three facilities from August 2019 to July 2020. Asymptomatic patients were chosen to increase the odds of patients surviving the follow-up period and “minimize interpatient variation.”
Overall, signs of MNPs were detected in the carotid plaques of a significant amount of patients. Polyethylene was present in 58.4% of patients, for example, and polyvinyl chloride was present in 12.1%. The mean level of polyethylene was 21.7 μg per milligram; the mean level of polyvinyl chloride was 5.2 μg per milligram.
A majority of the findings were nanoplastics, meaning they were smaller than 1000 nanometers.
After a follow-up period of more than 33 months, the study’s primary endpoint—nonfatal myocardial infarction, nonfatal stroke or all-cause mortality—occurred in 20% of patients with MNPs and 7.5% of patients without MNPs.
“Comparison of data on the basis of the locations of patients’ homes and of the recruitment centers did not reveal obvious differences,” the authors wrote. “Similarly, we cannot establish why only polyethylene and polyvinyl chloride, among the 11 types of plastics assessed, were detected. Studies in animal models suggest that the physicochemical features of different MNPs influence whether they reach distant organs. Additional work is needed to assess whether polyethylene and polyvinyl chloride accumulate preferentially within plaque and whether they are more pathogenic than other types of MNPs in this regard.”
The group also emphasized that these results do not necessarily prove causality. While patients with MNPs in their carotid plaque specimens were linked to a heightened risk of the study’s primary composite outcome, it is not certain that their risk was higher because of the MNPs.
“The association between the presence of MNPs within plaque and the incidence of a composite of cardiovascular disease or death outcomes may also entail the risk from exposure to other residual, unmeasured confounding variables, such as unknown exposures during the life course of the patient or, more broadly, the health status and behaviors of the patients,” they wrote.
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Michael has more than 16 years of experience as a professional writer and editor. He has written at length about cardiology, radiology, artificial intelligence and other key healthcare topics.