Inhaled Particle Deposition in the Human Respiratory System

The deposition of inhaled particles within the human respiratory system is governed by a combination of anatomical, physical and physiological factors. As air laden with particles traverses the conducting airways, larger particles tend to deposit by inertial impaction at bifurcations and in the oropharyngeal region, whereas intermediate-sized particles settle under gravity in the bronchioles during slower flow phases. Ultrafine particles are dominated by Brownian diffusion and may reach the distal alveolar region. The overall pattern of deposition varies with particle size, shape, density and charge, as well as with breathing parameters such as tidal volume and flow rate. Individual anatomical features—airway geometry, surface area, dead space volume and alveolar dimensions—combine with dynamic factors such as airflow regime and mucociliary clearance to determine regional dose. Variability between subjects, and within the same subject under different physiological conditions, has profound implications for both toxicant exposure and targeted delivery of inhaled therapeutics. Advances in experimental measurement techniques and computational modelling have refined our understanding of regional deposition, highlighted limitations in existing predictive dosimetry models, and opened pathways to more personalised assessments of respiratory exposure and treatment efficacy.

Research from Nature Portfolio

A recent experimental model reconstructed true-scale pulmonary acinar geometries to observe particle trajectories under breathing-like motion. It revealed that gravitational settling and Brownian diffusion interact through streamline crossing, creating distinct capture and escape zones in alveolated ducts. Detailed mapping of monodispersed microspheres (0.1–2 μm) showed enhanced local deposition for particles above 0.5 μm due to gravity, and strong concordance with numerical simulations. This work provides a conceptual framework for predicting particle fate at the alveolar level and validates computational approaches for deep-lung deposition.

Inhaled Particle Deposition in the Human Respiratory System publication trend

The graph below shows the total number of articles in inhaled particle deposition in the human respiratory system across all publications each year (not limited to Nature Index journals).

Technical terms

Inertial impaction: Deposition of particles when inertia carries them out of airflow streamlines, typically at airway bifurcations.

Gravitational sedimentation: Settling of particles under gravity during slower airflow, especially in smaller bronchioles.

Brownian diffusion: Random motion of ultrafine particles leading to deposition by collision with airway surfaces.

Dead space: Volume of airways where gas exchange does not occur; influences regional deposition and effective dose.

References

1. Particle dynamics and deposition in true-scale pulmonary acinar models. Scientific Reports (2015).
2. An experimental study on lung deposition of inhaled 2 μm particles in relation to lung characteristics and deposition models. Particle and Fibre Toxicology (2023).
3. A Review of Respiratory Anatomical Development, Air Flow Characterization and Particle Deposition. International Journal of Environmental Research and Public Health (2020).
4. Deposition efficiency of inhaled particles (15-5000 nm) related to breathing pattern and lung function: an experimental study in healthy children and adults. Particle and Fibre Toxicology (2017).