Simulation of airflow and aerosol deposition in the nasal cavity of a 5-year-old child Jinxiang Xi a,n , Xiuhua Si b , Jong Won Kim a , Ariel Berlinski c,d a Department of Systems Engineering, University of Arkansas, Little Rock, 2801 South University Avenue, ETAS 300, Little Rock, AR 72204, United States b Department of Engineering, Calvin College, Grand Rapids, MI, United States c Department of Pediatrics, University of Arkansas for Medical Science, Little Rock, AR, United States d Arkansas Children’s Hospital, Little Rock, AR, United States article info Article history: Received 13 September 2010 Received in revised form 14 December 2010 Accepted 14 December 2010 Available online 22 December 2010 Keywords: Nasal physiology Child–adult difference Child airway model Breathing resistance Microdosimetry Nasal deposition abstract As a human grows from birth to adulthood, both airway anatomy and breathing conditions vary that alter the deposition rate and pattern of inhaled aerosols. However, deposition studies have typically focused on adult subjects, results of which may not be readily extrapolated to children. Furthermore, because of greater ventilation rate per body weight, children receive a greater dose than adults and therefore are more susceptible to respiratory risks. This study is to evaluate the transport and deposition of respiratory aerosols in a nasal-laryngeal airway model based on MRI head images of a 5-year-old boy. Differences between this child and adults in nasal physiology and aerosol filtering efficiency will be emphasized. A validated low Reynolds number (LRN) k  o turbulence model was employed to simulate laminar, transitional, and fully turbulent flow regimes within the nasal airways. Particle trajectories and deposition in the spectrum of 0.5–32 mm were evaluated using a well-tested Lagrangian tracking approach for inhalation flow rates ranging from sedentary (3 L/min) to heavily active (30 L/min) conditions. Simulation results of the inhalation pressure drop and particle deposition rate provided a reasonable match with existing experimental results in nasal airway casts of children. Much higher breathing resistance was observed in the 5-year-old child compared to adults. Furthermore, deposition patterns were sensitive to inhalation flow rate under low activity conditions. An empirical correlation of child nasal filtering efficiency was proposed for micrometer particles based on a wide range of test conditions. Results of this study demonstrate that significant child–adult difference exists in inhaled aerosol depositions, which should be taken into account for risk assessment of airborne toxicants on infants and children. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction Nasal exposure to ambient toxicants in children may cause adverse effects such as nasal obstruction, sinusitis, nasal carcinomas, and spread of infectious diseases. A number of in vivo and in vitro studies have considered the deposition of inhaled aerosols in adult and child nasal airways. Experimental in vivo studies that have evaluated the aerosol nasal depositions in adult human subjects include Heyder, Gebhart, Rudolf, Schiller, and Stahlhofen (1986), Stahlhofen, Rudolf, and James (1989), Cheng et al. (1996a, 1996b), Swift and Strong (1996), Rasmussen, Andersen, and Pedersen (2000), etc. Only a Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jaerosci Journal of Aerosol Science 0021-8502/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaerosci.2010.12.004 n Corresponding author. Tel.: +1 501 569 8165; fax: +1 501 569 8698. E-mail address: jxxi@ualr.edu (J. Xi). Journal of Aerosol Science 42 (2011) 156–173