Computational assessment of the impact that wildland fire smoke exposure has on airflow and particle deposition in the mouse respiratory tract.

Wildland firefighters are frequently exposed to high concentrations of wildland fire smoke (WFS), yet the long-term health impacts of repeated occupational exposures remain poorly understood. To address this, our group recently developed a mouse exposure model to investigate the health effects of repeated exposure to WFS. To complement this previous study, here we perform multi-scale computational dosimetry simulations to quantitatively assess how WFS particulates deposit throughout the mouse respiratory tract. A multi-generational 3-dimensional model of the mouse respiratory tract is created from μCT images and used to perform high-fidelity computational fluid-particle dynamics simulations. Airflow and particle transport in airways not resolved through μCT images are modeled through a custom 1-dimensional dosimetry model. A novel integration of experimentally measured data of mouse lung mechanics, mouse breathing patterns, and smoke particle size distribution is used to parameterize the computational models. Our simulations predict between 1-3% of inhaled WFS particulates are deposited in the olfactory region of the nasal cavity, depending on the particle size and breathing conditions. Furthermore, over half of the total deposited particles did so in the alveolar region of the lungs. Deposition in these regions are particularly noteworthy as they may translocate to the blood stream and reach other organ systems. We found that the breathing pattern adopted by mice during WFS exposure led to an approximately 25% increase in the total deposition fraction of inhaled particles. Nonetheless, the significantly lower minute volume during smoke exposure ultimately decreased total deposited mass compared to normal breathing. This computational investigation improves our understanding of the regional deposition of WFS particulates in the mouse respiratory tract, which is vital for understanding how WFS exposure impacts health.