Microplastics and nanoplastics (MNPs) represent pervasive environmental contaminants. Although their occurrence in food, water, and air has been extensively documented, the quantitative translocation pathways from environmental media to human tissues remain inadequately characterized. This review synthesizes current evidence on human exposure to MNPs via ingestion and inhalation routes, while summarizing reported contamination levels in dietary sources and indoor environments. Investigations have consistently identified MNPs in diverse human tissues and biological fluids, demonstrating systemic internal exposure. Direct evidence of respiratory deposition emerges from their detection in pulmonary alveoli and lung tissues. The persistent presence of MNPs in peripheral blood indicates systemic circulation and potential distribution throughout the organism. Accumulation in metabolic and excretory organs, particularly the liver and kidneys, reveals potential sequestration and elimination pathways. The excretory dynamics are further evidenced by MNP detection in feces and urine, completing the exposure-excretion cycle. Of particular concern, their identification in placental tissue and breastmilk suggests possible transgenerational transmission, highlighting potential exposure risks during critical developmental windows. Substantial methodological variations in sample processing and analytical protocols, however, impede reliable cross-study comparisons and obscure definitive patterns regarding polymer-specific distributions and particle-size profiles across different organ systems. This review further examines emerging evidence on potential health implications and discusses underlying toxicological mechanisms of MNP exposure. We conclude by delineating crucial methodological challenges and proposing strategic research priorities to advance accurate risk assessment of human health impacts from MNP exposure.
 

Microplastics,Tissue Distribution,Human Exposure,Health Risk