10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Intranasal Airway Deposition of Dry Particles in Physical Models of Children and Adults during Inspiratory Flow Rates Representing Rest, Light, Moderate and Heavy Activity
Jana Kesavan, VALERIE J. ALSTADT, Jerold Bottiger, Keith Sedberry, Beth Laube, US ARMY ECBC
Abstract Number: 221 Working Group: Aerosols and Health - Connecting the Dots
Abstract Background: Although the potential for negative health effects from deposition of toxic particles in the intranasal airways of children makes determination of deposition in this region essential, studies of particle deposition that include exposing infants and children are not feasible. Anatomically-correct physical models provide a method for quantifying intranasal deposition of inhaled particles without direct exposure to humans. Toxic particles may be liquid or dry. However, little is known about intranasal deposition of dry particles during different activity levels within physical models of young children.
Methods: We used stereolithography and CT scans to generate anatomically-correct physical models of the head, face with nostrils and intranasal airways of a 2 and 5 year-old child and 18 year-old adult. We then quantified and compared deposition of 1-10 µm dry particles of Arizona Test Dust in the intranasal airways of the models during inspiration only, at flow rates representing rest, light, moderate and heavy activity. Data were standardized using the impaction parameter, so that deposition in the three models could be compared.
Results: Intranasal deposition of 2.458 µm dry particles at light activity flow rates was similar for all three models. However, deposition was significantly greater in the 2 and 5-year-old models, compared to the 18 year-old model, for particles smaller and larger than 2.458 µm, during inspiratory flow rates representing rest and light activity. Deposition in the 5 year-old was greater than in the 18 year-old for all particles ≥2.458 µm during moderate activity and ≤8.977 µm during heavy activity. Deposition in the 2 year-old model was significantly greater than in the 5 year-old model for ≥4.698 µm particles at light activity flows and for all particle sizes at moderate and heavy activity. Variability in intranasal deposition for the three models was reduced when standardized in terms of impaction parameter combined with the anatomical parameters of Amin (the minimum cross-sectional area of the nostrils) and Ellipticity (the ratio of nostril length to width).
Conclusions: Intranasal deposition of dry particles between 1-10 µm may be greater in 2 and 5 year-old children, at rest and during light activity, compared to adults, and may be greater in 2 year-old children, compared to 5 year-olds, during moderate and heavy activity. These results suggest that the intranasal airways of 2 and 5 year-old children may be at risk for detrimental health effects from increased exposure to toxic dry particles during nasal breathing, compared to adults. Studies in additional models based on similar age children are needed to confirm these findings.