Microplastics in blood: Small in size, big in threat

For decades, modern plastic was celebrated as a miracle of industrial convenience. But inside a high-tech operating suite in Thiruvananthapuram, Kerala, vascular specialists are confronting the dark side of that permanence — microscopic synthetic debris lodged directly within human blood vessels. What was long viewed as an ecological crisis confined to choked marine habitats and overflowing landfills has breached our internal biological defences. Microscopic synthetic fragments are now hitching a ride through the bloodstream and embedding deep within arterial walls, transforming microplastics from a distant environmental pollutant into an active suspect in vascular disease, plaque instability, and acute cardiac events.

When microplastics enter the body through ingestion, inhalation, or systemic absorption, their physical presence triggers a cascade of complex physiological responses. The primary concern among medical researchers centers on cellular strain, persistent biological inflammation, and oxidative stress. As these sharp, non-biodegradable particles come into direct contact with vessel walls, immune defense mechanisms treat the synthetic material as an invading threat.

Dr G Dimpu Edwin Jonathan, consultant in Interventional Cardiology at Aster RV Hospital in Bangalore, highlights how these microscopic fragments disrupt crucial vascular systems once they cross into circulation. “Microplastics are tiny pieces of plastic. People can take them in through what they eat and drink, or breathe them in with air,” notes Dr Jonathan. “Once inside the body, a portion may pass through body barriers into the bloodstream and move through blood vessels into other organs.”

This internal exposure can severely damage the delicate lining of blood vessels known as the endothelium. Healthy endothelial cells maintain vascular tone, control blood flow, and prevent inappropriate clotting. When this inner layer suffers oxidative harm, its ability to expand and relax diminishes —a crucial early indicator of cardiovascular disease.

Furthermore, the impact extends directly into cardiac muscle tissue itself. “Microplastics may disturb heart tissue and the way heart cells send signals,” explains Dr. Jonathan. “After these small bits enter the blood and reach heart cells, the cells come under strain. Some effects involve mitochondria alongside inflammation, causing cells to produce less usable energy so they cannot squeeze as strongly.” Beyond cellular energy depletion, researchers are closely observing how ongoing inflammation paired with altered platelet behaviour can accelerate plaque buildup along arterial walls, making existing plaques unstable and increasing the risk of sudden blockages.

The potential cardiovascular impact of microplastics moved to the forefront of medical discussion following landmark findings examining human arterial tissue. Researchers analysing carotid artery plaques removed during vascular surgery detected micro- and nanoplastics embedded directly within a significant portion of tissue samples.

Confirming these vascular observations, Dr Harikrishnan S, professor and head of the department of Cardiology at Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, points out that microscopic pollutants actively infiltrate arterial tissue. “Studies show that once microplastics enter the systemic circulation, they reach vascular plaques — a phenomenon we have directly observed within atherosclerotic plaques, where they are believed to accelerate arterial hardening,” explains Dr Harikrishnan S. “Research analysing carotid artery plaques identified microplastics in roughly 50% of examined patients. Emerging evidence suggests microplastics increase the overall risk of heart attacks by triggering endothelial dysfunction and elevating vascular inflammation, with mechanisms varying depending on the specific plastic polymer involved.”

However, experts urge rigorous scientific caution when interpreting these findings, noting what happens when microplastics become lodged in an arterial wall remains an active area of clinical investigation.

Dr RC Sreekumar, president of the Vascular Society of India and Chairman and head of Vascular and Endovascular Surgery at PRAN Hospital, Thiruvananthapuram, emphasises the distinction between plausible biological mechanisms and definitive epidemiological proof. “Several pathological mechanisms are biologically plausible. It can cause vessel wall inflammation, oxidative stress, and endothelial dysfunction,” says Dr Sreekumar. “It can destabilise atherosclerotic plaques, which will cause platelet aggregation that may block arteries and cause damage to organs like the brain and heart. A landmark human study found polyethylene in analysed carotid plaques. However, laboratory or operating-room contamination during sample handling is possible. So, while the finding is critically important, it should not yet be interpreted as definitive proof that plastics are damaging every person’s artery.”

Dr Niranjan Hiremath, senior consultant in Cardiovascular and Aortic Surgery at Apollo Hospital in Bangalore, also reinforces the need to view current data through an evidence-based lens. “The landmark study published in The New England Journal of Medicine in 2024 demonstrated an association, not proof of causation,” cautions Dr Hiremath. “International cardiovascular and environmental-health research is now examining whether long-term exposure could become an additional risk factor. However, the findings must be interpreted cautiously. Larger, long-term studies are needed before microplastics can be established as a direct cause of cardiovascular disease.”

Dr Jonathan edded scientists require extended tracking across diverse populations. “Nobody has proven that microplastics cause heart disease in people. Scientists need results that hold up over many years, watching how exposure builds over time and whether risk changes with different plastic polymers. For now, microplastics are best seen as a possible contributor, not a proven cause.”