title: Computational fluid dynamics investigation of human aspiration in low-velocity air: orientation effects on mouth-breathing simulations.
abstract: Computational fluid dynamics was used to investigate particle aspiration efficiency in low-moving air typical of occupational settings (0.1-0.4 m s(-1)). Fluid flow surrounding an inhaling humanoid form and particle trajectories traveling into the mouth were simulated for seven discrete orientations relative to the oncoming wind (0°, 15°, 30°, 60°, 90°, 135° and 180°). Three continuous inhalation velocities (1.81, 4.33, and 12.11 m s(-1)), representing the mean inhalation velocity associated with sinusoidal at-rest, moderate, and heavy breathing (7.5, 20.8, and 50.3 l min(-1), respectively) were simulated. These simulations identified a decrease in aspiration efficiency below the inhalable particulate mass (IPM) criterion of 0.5 for large particles, with no aspiration of particles 100 µm and larger for at-rest breathing and no aspiration of particles 116 µm for moderate breathing, over all freestream velocities and orientations relative to the wind. For particles smaller than 100 µm, orientation-averaged aspiration efficiency exceeded the IPM criterion, with increased aspiration efficiency as freestream velocity decreased. Variability in aspiration efficiencies between velocities was low for small (<22 µm) particles, but increased with increasing particle size over the range of conditions studied. Orientation-averaged simulation estimates of aspiration efficiency agree with the linear form of the proposed linear low-velocity inhalable convention through 100 µm, based on laboratory studies using human mannequins.
authors: Department of Occupational and Environmental Health, University of Iowa, 105 River Street, Iowa City, IA 52242, USA. renee-anthony@uiowa.edu
authors: T Renée
authors: TR
authors: Anthony
authors: Kimberly R
authors: KR
authors: Anderson
mesh_terms: D000392:Air Movements; D000395:Air Pollutants, Occupational / Q000009:adverse effects / Q000032:analysis*; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods; D006801:Humans; D057446:Hydrodynamics; D019570:Inhalation Exposure / Q000009:adverse effects / Q000032:analysis; D008348:Manikins; D009058:Mouth Breathing; D009949:Orientation; D010316:Particle Size
chemical_list: D000395:Air Pollutants, Occupational
keywords: CFD inhalability; aspiration efficiency; computational fluid dynamics; continuous inhalation; inhalable particulate mass; mouth breathing; orientation averaged; particle aspiration; particle transport; ultralow velocity