Assessing inhalation intake of microplastics using MPPD model.

Area of Science:

• Environmental Health
• Toxicology
• Respiratory Medicine

Background:

• Microplastics (MPs) are increasingly detected in human tissues.
• Inhalation is a significant exposure route for MPs, yet less studied than ingestion.
• Understanding MP deposition in the respiratory system is crucial for health risk assessment.

Purpose of the Study:

• To quantitatively estimate microplastic intake and internalization via inhalation.
• To assess the impact of different particle size distributions on MP deposition in the human lungs.
• To highlight the need for characterizing MPs in the inhalable range for respiratory tissue analysis.

Main Methods:

• Utilized the US Environmental Protection Agency's Multi-Path Particle Dosimetry (MPPD) model.
• Simulated cylindrical MPs with aerodynamic diameters from 0.1 to 10 μm and an aspect ratio of 3:1.
• Assessed three particle size distributions: power law, unimodal, and bimodal.

Main Results:

• Estimated human lung deposition of MPs ranged from 19.1 to 49.9 μg under default atmospheric conditions (0.1 μg m-3).
• While overall lung deposition showed minor differences across size distributions, pulmonary deposition was significantly influenced by distribution type.
• The pulmonary region exhibited greater sensitivity to MP size distribution variations.

Conclusions:

• Inhalable microplastics (0.1-10 μm) deposit in the human lungs, with notable accumulation in the pulmonary region.
• The specific size distribution of inhaled MPs critically affects deposition patterns within the lungs.
• Urgent characterization of MP size distribution and analysis in respiratory tissues are needed due to potential pulmonary health implications and slower clearance rates.