Microplastics and nanoplastics in plaque lining major blood vessel tied to heart attack, stroke, and early death: NEJM

"An increased risk of combined stroke, myocardial infarction, or death from any cause over nearly 3 years was found in people with microplastics and nanoplastics detection in atherosclerotic plaque from surgically excised carotid plaque specimens (20.0% versus 7.5%, HR 4.53)," the researchers reported.

Out of 11 types of plastics assessed, the researchers detected two in particular in the atheroma: polyethylene in 58.4% of participants (at a mean concentration of 21.7 μg/mg plaque) and polyvinyl chloride in 12.1% (mean 5.2 μg/mg).

Polyvinyl chloride and polyethylene, in their several forms, are used in a wide range of applications, including the production of cosmetics and food containers, and water pipes. MNPs have been found in drinking water, a large range of cosmetic products, foods, and air, also in a form bound to fine, inhalable particulate matter. Given the wide distribution and availability of MNPs, the attribution of all potential sources in humans is nearly impossible.

The environment is being inundated increasingly with plastic due to industrial processes. Plastics break down into smaller nanoplastics (particles smaller than 1,000 nm) and microplastics (particles smaller than 5 mm), both of which enter the human body through inhalation, ingestion, and skin exposure and have been found in the lungs, placenta, liver, and other tissue,

Microplastics and nanoplastics are emerging as a potential risk factor for cardiovascular disease (CVD) in preclinical studies. However, there is a lack of direct evidence that this risk extends to humans. To fill this knowledge gap, Raffaele Marfella, University of Campania Luigi Vanvitelli, Caserta, Italy, and colleagues conducted a prospective, multicenter, observational study comprising patients who were undergoing carotid endarterectomy for asymptomatic carotid artery disease.

The researchers analyzed excised carotid plaque specimens for the presence of MNPs using pyrolysis-gas chromatography-mass spectrometry, electron microscopy, and stable isotope analysis. Inflammatory biomarkers were assessed with immunohistochemical assay and enzyme-linked immunosorbent assay.

The study's primary endpoint was a composite of stroke, myocardial infarction, or death from any cause among patients with evidence of MNPs in plaque as compared with patients with plaque that showed no evidence of MNPs.

The study enrolled three hundred and four patients, and 257 completed a mean follow-up of 33.7 months.

The following were the key findings of the study:

• Polyethylene was detected in carotid artery plaque of 58.4% of patients, with a mean level of 21.7±24.5 μg per milligram of plaque; 12.1% of patients also had measurable amounts of polyvinyl chloride, with a mean level of 5.2±2.4 μg per milligram of plaque.
• Electron microscopy revealed visible, jagged-edged foreign particles among plaque macrophages and scattered in the external debris.
• Radiographic examination showed that some of these particles included chlorine.
• Patients in whom MNPs were detected within the atheroma were at higher risk for a primary end-point event than those in whom these substances were not detected (hazard ratio, 4.53).

According to the authors, a greater concentration of polyethylene correlated with greater expression of inflammatory biomarkers and markers of macrophage and lymphocyte infiltration.

However, study authors cautioned that the plastics group tended to be younger, more likely smokers and men, and had a greater prevalence of cardiovascular disease, diabetes, and dyslipidemia.

The study's observational nature meant that it was potentially subject to other residual confounding, precluding any causal conclusions. Also, there was a possible risk of laboratory contamination.

Reference:

Marfella R, Prattichizzo F, Sardu C, Fulgenzi G, Graciotti L, Spadoni T, D'Onofrio N, Scisciola L, La Grotta R, Frigé C, Pellegrini V, Municinò M, Siniscalchi M, Spinetti F, Vigliotti G, Vecchione C, Carrizzo A, Accarino G, Squillante A, Spaziano G, Mirra D, Esposito R, Altieri S, Falco G, Fenti A, Galoppo S, Canzano S, Sasso FC, Matacchione G, Olivieri F, Ferraraccio F, Panarese I, Paolisso P, Barbato E, Lubritto C, Balestrieri ML, Mauro C, Caballero AE, Rajagopalan S, Ceriello A, D'Agostino B, Iovino P, Paolisso G. Microplastics and Nanoplastics in Atheromas and Cardiovascular Events. N Engl J Med. 2024 Mar 7;390(10):900-910. doi: 10.1056/NEJMoa2309822. PMID: 38446676.