NASAL DOSIMETRY MODELING FOR HUMANS

An anatomically accurate, finite element mesh of the right human nasal cavity was constructed from computerized axial tomography (CAT) scans of a healthy adult nose. The equations of motion were solved numerica lly to determine the steady laminar inspiratory airflow patterns at qu iet breathing flow rates. The numerically computed velocity field was compared with the experimentally measured velocity field in a large-sc ale (20x) model, which was built by scaling up from the same CAT scans . Numerical results showed good agreement with the experimental result s throughout the nasal cavity. The numerical velocity field was then u sed in the solution of the steady convective diffusion equation using the finite element mesh to determine the uptake pattern of inhaled pol lutants. The mass transfer boundary condition used at the nasal cavity wall included the effects of solubility, diffusivity, and removal of pollutants by first-order chemical reaction in the mucosal lining. The results showed that about 80% of highly soluble or highly reactive po llutants are absorbed up to the posterior end of the nasal turbinates. For these pollutants, most uptake occured in the anterior and lower h alf of the nasal cavity. For more insoluble pollutants, uptake was mor e uniform along the nasal cavity. Finite element and physical models a re powerful new tools that, when combined with information on human na sal mucosal histology, blood Now, and biochemistry of the pollutant re actions in the mucosa and throughout the body, can provide valuable in formation on nasal dosimetry of inhaled pollutants.