Transport and deposition of microplastics and nanoplastics in the human respiratory tract

Recent studies have unveiled the presence of nano- and microplastics (NMPs) within both human and avian respiratory systems, prompting an exploration into the interactions between these particles and the human respiratory system. Experimental evidence has strongly suggested that these plastic particles amplify human susceptibility to a spectrum of lung disorders, including chronic obstructive pulmonary disease, fibrosis, dyspnea, asthma, and the formation of frosted glass nodules. To advance the understanding, this study employs computational fluid-particle dynamics (CFPD) to study the transfer and deposition of poly-dispersed 1-100 nm nanoplastics and 1-100 μm microplastics under three breathing conditions. Notably, this investigation utilized a computerized tomography-based full respiratory tract model, comprehensively spanning regions from the nasal cavity to the 13th generation of the bronchial tree, providing a highly detailed representation of the anatomical complexities of the human respiratory system. The outcomes reveal distinctive deposition patterns of spherical, cylindrical, and tetrahedral NMPs in the human respiratory tract, elucidating the significant impact of breathing rate, pinpointing specific deposition hotspots, and highlighting the critical role of particle size in governing transport and deposition behavior. This study establishes a link between the behavior of nanoplastics within the respiratory tract and its consequential impact, providing insights that extend across three critical domains. Firstly, in environmental health, the research contributes to understanding NMP-related air pollution. Secondly, within respiratory medicine, the findings shed light on NMPs' role in respiratory disorders. Finally, this study guides the formulation of regulations addressing permissible NMP levels and mitigating associated health and environmental risks.