Background: Microplastics (MPs;<5 mm) and nanoplastics (NPs;<1 μm) are emerging pollutants increasingly causing environmental and health concerns due to their widespread presence and poor biodegradability. Humans are exposed to these particles through ingestion, inhalation, and dermal contact. Methods: This narrative review explores the impact of microplastics on human health by assessing exposure pathways and organ-specific effects. Studies (2010–2024) from major databases were synthesized by polymer type, exposure route, and observed outcomes across key body systems. Results: Studies have reported that nylon microfibers impair respiratory health by releasing toxic compounds that inhibit epithelial cell differentiation, disrupt tissue repair, and suppress Hoxa5 transcription factor expression. Evidence also indicates that MPs alter nasal and gut microbiota composition, potentially contributing to respiratory, digestive, and immune disorders. Some studies suggest that exposure to sources such as clothing dryers can modify airway protection gene expression. Additionally, MPs disrupt cellular signaling pathways and have been observed to accumulate in male reproductive tissues, including the prostate and semen, raising concerns about infertility and prostate cancer risk. Conclusion: Further research is urgently needed to clarify the long-term health effects of MPs, particularly regarding gastrointestinal function and chronic disease. This review highlights that MPs enter the human body through multiple pathways and exert detrimental effects on various organ systems. Effective mitigation strategies and improved public awareness are essential to reduce exposure and protect human and environmental health.
Beigrezaee et al. (Tue,) studied this question.