Article Abstract

Theoretical deposition of random walk-generated nanoaggregates in the lungs of healthy males and females

Authors: Robert Sturm


Background: Particle aggregates with different complexity and size represent an essential component of the ambient atmosphere. Therefore, theoretical knowledge on the effects of this particle group in the human respiratory tract is indispensable. In the present study an innovative model for the hypothetical generation of such aggregates is described in detail. In addition, lung deposition of the computed particles was predicted for both male and female subjects.
Methods: The theoretical approach used in this contribution is based on a random-walk algorithm allowing the construction of aggregates with cluster-, chain- or disk-like geometry. Basic components of these complex particulate structures are represented by monodisperse spheres with a diameter of 1 nm. These spherical elements were sticked together by random walks consisting of 10, 100 or 1,000 steps, resulting in aggregates of different size and complexity. Deposition calculations were carried out by assuming (I) a stochastic structure of the human respiratory tract and (II) different physical mechanisms seizing the inhaled particles.
Results: Under sitting breathing conditions total deposition of variably sized nanoaggregates ranges from 98.9% to 100% in males and from 98.6% to 100% in females. In the extrathoracic region particle accumulation amounts to 39.3–64.6% (males) and 40.4–64.1% (females), whereas bronchial deposition adopts values of 20.4–44.6% (males) and 20.9–43.2% (females). Alveolar deposition can be estimated at 1.68–14.9% in males and 1.58–18.4% in females. Gender-specific differences of generation-by-generation deposition of nanoaggregates are on the order of 0–0.5%.
Conclusions: According to the results of the study deposition of nanoaggregates in the human respiratory tract strongly depends on the size of the inhaled particulate structures. In addition, partly significant differences of pulmonary particle accumulation between male and female subjects can be determined. All these circumstances have to be considered with regard to the formulation of respective health risk assessments.