Study finds microplastics in blood clots, linking them to higher risk of heart attacks and strokes

By Dr. Chinta SidharthanReviewed by Susha Cheriyedath, M.Sc.May 22 2024

In a recent study published in the journal EBioMedicine, researchers in China aimed to understand the impact of microplastic pollution on human health by identifying and quantifying the mass concentrations, physical properties, and polymer types of microplastics obtained from thrombi retrieved from deep veins found in the lower extremities, and coronary and cerebral arteries.

Study: Multimodal detection and analysis of microplastics in human thrombi from multiple anatomically distinct sites. Image Credit: Ezume Images / Shutterstock

Background

The durability, versatility, and affordability of plastics that have made them almost indispensable to humans have also led to widespread plastic pollution and the persistence of microplastics in the environment. Discarded plastic products often disintegrate into micro and nanoplastics that pollute the atmosphere, land, and water. Microplastic pollutants are of two types — primary microplastics that are produced for medical devices and cosmetics and are less than 5 mm in size, and secondary microplastics that are formed when larger plastics break down due to chemical or physical fragmentation.

Microplastics have been detected in various animals, such as marine organisms and humans. Within the human body, microplastics have been retrieved from blood, sputum, liver, heart, lungs, testes, endometrium, placenta, and amniotic fluid. Studies have also found microplastics in thrombi or blood clots. Given that thrombus formation has genetic and environmental risk factors, these findings suggest that microplastics could pose a high risk to vascular health.

About the study

In the present study, the researchers employed multimodal methods such as gas chromatography-mass spectrometry, scanning electron microscopy, and laser direct infrared spectroscopy to analyze and quantify the types of polymers, mass concentrations, and physical properties of microplastics obtained from thrombi from three major blood vessels — deep veins, coronary arteries, and intracranial arteries.

Individuals who required venous or arterial thrombectomy after suffering from myocardial infarction, ischemic stroke, or deep vein thrombosis were included in the study if their thrombus was collected immediately after the surgery; they had no stents, artificial bones, or grafts and had never used therapeutic or diagnostic agents containing microplastics. Information on demographic characteristics, medical history, lipid profile, and electrolyte panel was also collected for each participant.

The thrombus samples were analyzed for microplastics using pyrolyzed gas chromatography-mass spectrometry, where the microplastics are thermally broken down. Then, a gas chromatographic column separates the fragments, after which mass spectrometry characterizes the particle.

The study targeted ten polymer types, which included polyethylene, polystyrene, polyvinyl chloride, polycarbonate, polypropylene, polyamide 6, and four more. Subsequently, scanning electron microscopy and laser direct infrared spectroscopy were used to assess the particles' size, number, and morphology. Some samples were excluded in this step due to insufficient thrombus samples or the inability to distinguish the predominant microplastic, polyamide 66, from the natural proteins.

The abundance and the distribution of sizes of the microplastics were then analyzed and compared to a microplastics spectrum library. The individual types of microplastics present in each sample were also quantified. Rigorous measures of quality control, as well as multiple negative and positive controls, were used in each step of the process to control for background contamination.

Results

The findings revealed that microplastics made of various types of polymers and with different physical characteristics were present at varying mass concentrations in thrombi that formed in major human arteries and veins. The microplastic levels in human thrombi have a positive correlation with the severity of ischemic strokes.

Of the 30 thrombi acquired from patients with myocardial infarction, deep vein thrombosis, or ischemic stroke, 24 (80%) contained microplastics. The median concentration of microplastics in the thrombi from myocardial infarction, deep vein thrombosis, or ischemic stroke cases was 141.80 μg/g, 69.62 μg/g, and 61.75 μg/g, respectively.

The major polymers identified in the microplastics retrieved from thrombi were polyethylene, polyvinyl chloride, and polyamide 66. Laser direct infrared spectroscopy also revealed that of the 15 types of microplastics identified, polyethylene was the most dominant, having a diameter of 35.6 micrometers and constituting 53.6% of all microplastics retrieved. The microplastics were heterogeneous in size.

The D-dimer levels, one of the hypercoagulability biomarkers that indicate the increased risk of thrombotic events, were significantly higher in groups in which microplastics were detected in the thrombi, as compared to the groups in which microplastics were not detected. This suggested a direct link between microplastic concentrations in the body and the risk of thrombotic events.

Conclusions

Overall, the study found that thrombi retrieved from major blood vessels of patients with myocardial infarction, ischemic stroke, or deep vein thrombosis contain significant concentrations of microplastics of varying polymer types and physical properties. Furthermore, the risk of thrombotic events and disease severity increases with increasing levels of microplastics.