Particle Deposition of Airborne Microplastic Fibers in the Human Lung: A modeling framework linking fiber size, shape, orientation, and polymer type to regional lung deposition

Journal of Environmental Exposure Assessment (2026)

DOI: 10.20517/jeea.2025.45

Authors:

Ashish C. Jachak, PhD, MBA           Frank Pagone, PhD, CIH     

 

 

 

 

 

Why Particle Deposition of Airborne Microplastic Fibers in the Human Lung Matters

Airborne microplastics are increasingly recognized as an inhalation exposure concern, and environmental measurements indicate they are predominantly fibrous, not spherical . Because aerodynamic diameter—not geometric size alone—drives where particles deposit in the respiratory tract, fiber geometry and orientation become central to exposure and risk evaluation.

If you can estimate (or measure) a microplastic fiber’s aerodynamic diameter, you can better predict where dose is delivered in the lung—nasopharyngeal, tracheobronchial, or alveolar regions.

About RHP’s Study

This study systematically modeled deposition of fibrous microplastics in three regions of the lung using the International Commission on Radiological Protection (ICRP) deposition model, with fiber-specific adjustments for geometry, density, and orientation.

Study Design Highlights

• Modeled deposition in nasopharyngeal, tracheobronchial, and alveolar regions using the ICRP framework.
• Evaluated fiber length (10–50 µm) and diameter (0.75–5 µm) ranges representative of reported airborne fibers.
• Compared orientations (parallel, perpendicular, random) to bound real-world behavior.
• Compared common polymers: PS, PP, PE, PET, PVC, PMMA.

Key Findings

1. Nasopharyngeal deposition is the dominant site for many fiber conditions
   Modeled deposition fraction peaks at ~0.87 in the nasopharyngeal region for fibers with aerodynamic diameters ~5–7 µm
2. Tracheobronchial deposition peaks are lower and narrowly size-dependent
   Maximum tracheobronchial deposition is ~0.06, generally associated with aerodynamic diameters around ~2–4 µm
3. Alveolar deposition is highest for thin, shorter fibers
   Maximum alveolar deposition reaches ~0.13 for 0.75 µm diameter fibers with lengths up to ~35 µm under random orientation assumptions
4. Geometry dominates polymer type across modeled ranges
   Across PS, PP, PE, PET, PVC, and PMMA, patterns are qualitatively consistent, indicating fiber geometry/aerodynamics is often the primary driver of regional deposition trends

Why Modeling Adds Value

Using theoretical deposition modeling offers practical advantages for decision-making, including:

• Builds from deposition equations widely used in lung deposition modeling and can reduce reliance on burdensome resource-intensive approaches
• Enables repeatable, scalable scenario evaluation across conditions without the cost of extensive experimental campaigns
• Produces predictions efficiently compared with prolonged experimental timelines
• Can reduce the need for animal/human testing as an ethical alternative to historical approaches

Contact RHP Risk Management to Learn More About Our Peer-Reviewed Research, “Particle Deposition of Airborne Microplastic Fibers in the Human Lung”

Call (866) 481-8188 to contact RHP Risk Management to discuss how RHP can support:

• exposure model implementation and scenario analysis
• derivation of regional lung burden estimates from monitoring inputs
• uncertainty characterization and defensible reporting for regulatory contexts