Assessing inhalation intake of microplastics using MPPD model.

Increasing evidence of the presence of small microplastics in human tissues necessitates research on their intake routes and internalization. Among two major routes of exposure to microplastics (MPs), inhalation pathways are less investigated than ingestion pathways. In this study, quantitative estimation of microplastics intake and internalization was conducted using the multi-path particle dosimetry (MPPD) model by US Environmental Protection Agency assuming three representative particle size distributions (i.e., Power law, unimodal, and biomodal distributions) of cylindrical MPs within the aerodynamic diameter between 0.1 and 10 μm at the aspect ratio of 3:1. Assuming the default atmospheric concentration of MPs at 0.1 μg m-3, the estimated mass deposition in human lungs ranged 19.1-49.9 μg. Although sensitivity analysis revealed that estimated mass deposition of MPs in human lungs were not much different among three particle size distributions, deposition in the pulmonary region was strongly affected by the type of size distributions. Because of suspected health symptoms of MPs in the pulmonary region and the slower clearance in this region, it is of urgent needs to characterize MP size distribution in the inhalable particle size range (0.1-10 μm) and to analyze MPs in the same size range in human respiratory tissues.