Microplastics and nanoplastics are an emerging threat to cardiovascular health

Plastics, ubiquitous in our modern lives, have infiltrated every corner of our planet. From the depths of our oceans to the air we breathe, these synthetic polymers have become integral to our environment. The production of plastics continues to rise steadily, with this trend expected to persist until 2050. 

Plastics can contaminate the environment through ocean currents, atmospheric winds, and terrestrial processes, leading to their widespread dispersion. Once released into nature, plastics undergo degradation, resulting in the formation of microplastics (particles smaller than 5 millimetres) and nanoplastics (particles smaller than 1,000 nanometres). 

Both types of particles induce various toxic effects. While the detrimental effects of microplastics and nanoplastics (MNP) on marine life and ecosystems are well-documented, a new concern is emerging: The potential impact of MNPs on human health, particularly cardiovascular disease.

Recent preclinical studies have highlighted a concerning correlation between MNPs and cardiovascular dysfunction. These minuscule particles, measuring less than 5 mm for microplastics and under 1,000 nanometres for nanoplastics, penetrate our bodies through ingestion, inhalation, and skin exposure. Once inside, they interact with our tissues and organs, raising concerns about cardiovascular harm. 

Several studies have demonstrated that MNPs enter the human body via ingestion, inhalation, and skin contact, where they interact with tissues and organs. MNPs have been detected in various human tissues, including the placenta, lungs, and liver, as well as in breast milk, urine, and blood. Recent studies conducted in preclinical models have also implicated MNPs as a potential new risk factor for cardiovascular diseases.

However, the question remains: Do these findings have implications for human health? Until now, direct evidence linking MNPs to cardiovascular disease in humans has been limited. However, a study published in The New England Journal of Medicine has started to shed light on this mystery.

In the study, researchers examined carotid artery plaque to uncover clues regarding the presence and potential impact of MNPs. Initially, a cohort of 304 patients was enrolled, with 257 participants completing the follow-up period. Employing cutting-edge techniques such as pyrolysis-gas chromatography-mass spectrometry and electron microscopy, researchers meticulously analysed carotid plaque specimens to identify the presence of MNPs. 

Among the 11 different MNPs measured, polyethylene and polyvinyl chloride were detectable within the carotid plaque in microgrammes (μg) per mg of plaque. Patients with MNPs in their plaque exhibited a significantly higher risk of myocardial infarction, stroke, or death compared to those without, even after a follow-up period of 34 months.

The findings of the study were groundbreaking. Polyethylene, one of the most prevalent forms of plastic, was detected in the carotid plaque of 150 patients (58.4 per cent), with an average concentration of 21.7 ±24.5 μg per mg of plaque. Additionally, polyvinyl chloride, another common plastic polymer, was found in plaque from 31 patients (12.1 per cent), with an average concentration of 5.2 ± 2.4 μg per mg of plaque. 

Remarkably, patients with MNPs in their plaque exhibited a significantly higher risk of myocardial infarction, stroke, or death from any cause at 34 months of follow-up compared to those in whom MNPs were not detected.

Stable isotope analysis further supported these findings, identifying two distinct clusters of patients based on their isotopic values. Patients with lower isotopic values, indicative of MNPs contamination, displayed a higher incidence of plaque-associated MNPs and a correspondingly elevated risk of cardiovascular events.

Source: Marfella et al (2024) / Microplastics and Nanoplastics in Atheromas and Cardiovascular Events, The New England Journal of Medicine

Observational data from occupational exposure studies indicated a heightened risk of cardiovascular disease among individuals exposed to plastics-related pollution, including polyvinyl chloride, compared to the general population. 

The prevalence of MNPs in various human tissues and bodily fluids emphasised the widespread nature of plastic pollution and its potential health ramifications. The findings of the study raise concerns regarding the cardiovascular effects of MNPs and underscore the pressing need for additional research into their mechanisms of action and long-term health implications.

But how do these insidious particles find their way into our bodies? The omnipresence of plastics in our environment provides numerous pathways for exposure. MNPs have been identified in drinking water, various foods, cosmetic products, and can even be inhaled as part of fine particulate matter. Their small size enables easy absorption and distribution, allowing them to penetrate highly vascularised organs, including the heart.

Source: Marfella et al (2024) / Microplastics and Nanoplastics in Atheromas and Cardiovascular Events, The New England Journal of Medicine

While the precise mechanisms underlying the cardiovascular toxicity of MNPs are yet to be fully understood, their potential impact cannot be overlooked. Polyethylene and polyvinyl chloride, which are omnipresent in our daily lives, have been linked to various cardiovascular abnormalities in animal models. 

From inducing pericardial effusions to promoting prothrombotic states, these plastics represent a significant threat to cardiovascular health. As plastics continue to infiltrate our environment, mitigating their impact on human health must become a top priority.