Bioaccumulation of Microplastics: From Environmental Pollutants to Multisystemic Toxicity in Humans

Plastic products are ubiquitous, and their tendency to break down into smaller pieces has led to their extensivedistribution through oceans, terrestrial environments, and atmospheric winds. Microplastics are plasticparticles ranging in size from 5 millimeters to 1 micrometre, while nanoplastics are smaller, typically measuringunder 1,000 nanometres. The continuous shredding of larger plastic debris into smaller pieces has resulted insignificant and persistent environmental pollution. The projected rise in microplastics as contaminants due totheir widespread presence across ecosystems and living organisms has attracted increasing scientific andsocietal attention. Microplastics have already been found in plant life, animal species, and human tissues.1 The release of microplastics and nanoplastics into the air as they fragment in the environment is a concern, as istheir human exposure via digestive ingestion, inhalation, and dermal contact. In 2022, researchers comparedtwo modes of human exposure to microplastics: microplastic exposure from seafood consumption and inhalingplastic fibres through breathing air at home. Invisible plastic fibres shed by upholstery or clothing wereidentified as a greater threat to human exposure than seafood consumption.1-3 The microplastics, as airborneparticles, with their potential to penetrate human tissues, raise the question of what effect, if any, they have onhuman health. In 2022, plastic particles were reported in the lungs and blood of living humans.3-4 The presence of micro- andnanoplastics in human blood implies systemic distribution, with the potential for these particles to reachorgans and tissues throughout the body. Chronic exposure to microplastics and their long-term physiologicaleffects are emerging as potential risk factors for multisystemic adverse outcomes. Both particles have beenreported to interact and trigger toxicological effects, including dysbiosis in the gut and oxidative stress,inflammatory, and immune responses in human tissue. A recent study from the University of New Mexico hasfound up to 10 times higher concentrations of microplastics in the human brain among individuals withdementia than in those without the condition.2 Using electron microscopy and chemical analysis, researchersdiscovered nanoparticles, mainly polyethylene, in brain tissue samples, and surprisingly, microplasticbioaccumulation is more concentrated in the brain than in the liver or kidneys, possibly due to damage to theblood-brain barrier.2-4 Although causation has not been confirmed, scientists warn of micro- and nanoplastics'role in exacerbating neurodegenerative diseases such as Alzheimer's, Parkinson's, and prion disease, throughmechanisms involving oxidative stress, mitochondrial dysfunction, neuroinflammation, protein aggregation,and impaired brain waste removal systems, such as the glymphatic system.2-4 A recent cardiac study highlighted that two plastic types were consistently found in atherosclerotic plaque samples: polyethylene (PE) and polyvinyl chloride (PVC) in patients undergoing carotid endarterectomy.4 Researchers suggest thatphysicochemical differences, such as molecular weight, polarity, and shape, may make these plastics morelikely to accumulate in vascular tissues and contribute to inflammation, potentially leading to a higherincidence of major cardiovascular events.4 Animal studies have shown that microplastics can inducecardiovascular toxicity, including promoting thrombosis, impeding angiogenesis, and causing structural cardiacissues; however, the levels used in animal experiments were significantly higher than those observed in humansamples, limiting a direct comparison.4,5 Although current findings are primarily derived from observationalstudies and do not establish definitive causal relationships, a growing body of evidence suggests associationsbetween microplastic exposure and impacts on human health. While further mechanistic and longitudinalstudies are necessary to clarify the nature and extent of these effects, in light of emerging evidence, adopting aprecautionary approach to reducing plastic exposure is crucial. Reducing microplastic exposure requires minimizing single-use plastics, improving waste managementsystems, and promoting sustainable product alternatives. The healthcare sector must protect public health byprioritizing education, supporting continued research, fostering greater public and policy awareness, drivingbehavioural change, promoting sustainable choices, and advocating for stronger regulations to reduce plasticproduction and usage, thereby minimizing microplastic contamination in food systems and the environment. Editor-in-Chief How to cite this: Alamgir W, Shan H. Bioaccumulation of Microplastics: From Environmental Pollutants to Multisystemic Toxicity in Humans. Life and Science. 2025; 6(2): 154-155. doi: http://doi.org/10.37185/LnS.1.1.946