Biochemical Effects of Microplastics on Human Health: A Comprehensive Review

Microplastics (MPs), plastic particles less than 5 mm in size, have emerged as pervasive environmental contaminants with significant biochemical implications for human health. This review systematically explores the pathways through which MPs enter the human body, primarily via ingestion, inhalation, and dermal contact, and their subsequent biodistribution to vital organs, including the lungs, liver, kidneys, gastrointestinal tract, brain, and reproductive organs. Once internalized, MPs provoke complex biochemical responses such as oxidative stress, inflammation, endocrine disruption, and genotoxicity, contributing to systemic toxicity and chronic conditions like metabolic syndrome, neurodegenerative diseases, immune dysregulation, reproductive dysfunctions, and cancer. Organ-specific impacts are detailed, showing disruptions in gut microbiota, hepatic lipid metabolism, renal filtration, and neurochemical signaling. The review further identifies critical biochemical biomarkers, including elevated cytokines, lipid peroxidation products, and hormonal fluctuations, as early indicators of MP-induced toxicity. It assesses current risk evaluation models and emphasizes the urgent need for standardized detection methods, biomonitoring frameworks, and computational modeling to predict human health outcomes. Preventive and mitigative strategies are discussed, spanning regulatory bans on microbeads, advancements in wastewater treatment, and international policy coordination. The review concludes by advocating for global collaboration in research and policy development to combat the growing threat of microplastics, while calling for more longitudinal studies to elucidate their long-term human health effects.