Experimental analysis of allergenic tree pollen deposition in a three-dimensional anatomical model of the adult nasal cavity

<b>Introduction:</b> Exposure to pollen allergens is one of the key environmental factors determining the occurrence of allergic rhinitis. In Central Europe, tree pollen plays a significant role in triggering symptoms of inhalant allergy in the spring months.Aim: This study evaluated the deposition of tree pollen grains in a 3D anatomical model of the adult nasal cavity under varying flow rates (5 L/min, 7.5 L/min, and 20 L/min per nostril).<b>Material and methods:</b> Original methods of analysis were developed, including macroscopic analysis of photographs reflecting tree pollen deposits on the surface of the lateral wall of a printed 3D anatomical model of the nasal cavity and nasal septum, and microscopic evaluation of pollen collected from selected parts of the nasal geometry. The macroscopic analysis was supplemented with original software for the quantitative determination of areas covered with pollen deposits.<b>Results:</b> The results showed statistically significant differences in the regional deposition of pollen grains of different sizes in the nasal cavity, depending on the flow conditions. The deposition of birch, alder, and hazel pollen grains in the nasal cavity exhibits similar characteristics, with significant differences between the individual segments of the lateral wall and the nasal septum. While the middle segment of the lateral wall accounted for the largest segment share of the total lateral wall deposition, the highest relative pollen deposition in relation to the segment area was found in the front segment. The posterior segment of the lateral wall showed a marginal contribution to the deposition process. The most significant percentage of the segment area of the nasal septum covered with pollen was recorded in the anterior segment. However, the posterior segment accounted for a larger share of the total septal deposition due to its larger surface area. Consistent findings describe deposits of large pollen grains from pine and spruce trees. The values of segmental pollen deposition in the anterior segment were significantly higher than in the other segments. The deposition on the nasal septum was significantly greater in the anterior than in the posterior segment. Lateral wall share % and septal share % tended to increase with increasing airflow through the nasal cavity, reaching their highest values at 20 L/min. The intensification of airflow led to a shift in the location of maximum pollen deposition towards the anterior sections of the nose, with a simultaneous reduction in pollen penetration into the posterior segments.<b>Conclusions:</b> The study confirms the role of inertial effects in the flow and deposition of aerosols in the nasal cavity, indicating that the large size of pollen grains and higher airflow rates promote pollen deposition mainly in the anterior regions of the lateral wall and nasal septum. However, it also shows that other deposition mechanisms, such as direct interception in the case of grain aggregates, and differences in effective particle density, may influence the spatial distribution of deposited pollen in the nasal cavity. The results obtained should facilitate the control of allergen exposure and the use of topical treatment.