In a recent study published within the journal EBioMedicineresearchers in China wanted to grasp the impact of microplastic pollution on human health by identifying and quantifying the mass concentrations, physical properties and polymer varieties of microplastics obtained from clots collected from the deep veins of the lower limbs and coronary and cerebral arteries.

Test: Multimodal detection and evaluation of microplastics in human thrombi from multiple anatomically distinct sites. Image Source: Ezume Images / Shutterstock

Background

The sturdiness, versatility and affordability of plastics, which have made them almost indispensable to humans, have also led to widespread plastic pollution and the persistence of microplastics within the environment. Discarded plastic products often break down 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 lower than 5 mm in size, and secondary microplastics, that are formed when larger plastics break down through chemical or physical fragmentation.

Microplastics have been detected in various animals, corresponding to marine life and humans. Within the human body, microplastics are obtained from blood, sputum, liver, heart, lungs, testicles, endometrium, placenta and amniotic fluid. Studies have also shown the presence of microplastics in clots, or blood clots. On condition that clot formation has genetic and environmental risk aspects, these findings suggest that microplastics may pose a high risk to vascular health.

Concerning the study

In the current study, scientists used multimodal methods corresponding to gas chromatography-mass spectrometry, scanning electron microscopy, and direct infrared laser spectroscopy to investigate and quantify polymer types, mass concentrations, and physical properties of microplastics obtained from clots from three major blood vessels – veins deep, coronary arteries and intracranial arteries.

The study included individuals who required venous or arterial thrombectomy after myocardial infarction, ischemic stroke or deep vein thrombosis, if their thrombus was collected immediately after surgery; they’d 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 every participant.

The clot samples were analyzed for microplastics using pyrolyzed gas chromatography-mass spectrometry, during which microplastics are thermally broken down. The fragments are then separated on a gas chromatography column, after which the particle is characterised by mass spectrometry.

The study focused on ten varieties of polymers, including polyethylene, polystyrene, polyvinyl chloride, polycarbonate, polypropylene, polyamide 6 and 4 others. Scanning electron microscopy and direct infrared laser spectroscopy were then used to evaluate particle size, number and morphology. Some samples were excluded at this stage on account of insufficient thrombus samples or inability to tell apart the predominant microplastic, polyamide 66, from natural proteins.

The abundance and size distribution of microplastics were then analyzed and in comparison with a library of microplastic spectra. The particular varieties of microplastics present in each sample were also quantified. Strict quality control measures are in place at every step of the method, in addition to quite a few negative and positive controls to regulate background contamination.

Results

The findings revealed that microplastics product of various kinds of polymers and with different physical properties were present at different mass concentrations in clots forming in major human arteries and veins. The extent of microplastics in human clots has a positive correlation with the severity of ischemic strokes.

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

The essential polymers identified within the microplastics recovered from the clots were polyethylene, polyvinyl chloride and polyamide 66. Laser infrared spectroscopy also revealed that of the 15 varieties of microplastics identified, polyethylene was the dominant one, having a diameter of 35.6 micrometers and accounting for 53.6% of all microplastics recovered. The microplastics were heterogeneous in size.

The concentration of D-dimer, one in all the biomarkers of hypercoagulability indicating an increased risk of thrombotic events, was significantly higher within the groups during which microplastics were detected within the thrombi, in comparison with the groups during which no microplastics were detected. This suggested a direct link between the concentration of microplastics within the body and the danger of thrombotic events.

Conclusions

Overall, the study found that clots taken from major blood vessels of patients with myocardial infarction, ischemic stroke or deep vein thrombosis contain significant concentrations of microplastics with different polymer types and physical properties. Furthermore, the danger of thrombotic events and disease severity increases as microplastic levels increase.