A numerical study of the effect of breathing mode and exposure conditions on the particle inhalation and deposition

Objective: The exposure to airborne particles are of great concern in public health. The present study was aimed to clarify the effects of the breathing mode (nasal and oral inhalation) and exposure conditions on particle inhalation and deposition in human airway. Methods: A scanned upper airway embedded body model in an extended computational domain was constructed to perform numerical investigation into the inhalation and deposition of airborne particles. Results: It was clarified that the inhalation of sub-micro and micro particles was of high efficiency and insensitive to the breathing mode, while super microparticles were much less inhalable, in particular under the nasal intake. Moreover, the relative variation of environmental wind speed and direction could significantly reshape the breathing zone as well as modify the critical inhalable area at far upstream. In addition, the breathing mode was found to be affective on the regional deposition of the microparticles, and increasing the proportion of nasal inhalation flowrate slightly enhanced the total deposition in the upper airway model. Conclusion: The breathing mode and exposure conditions significantly influence the particle inhalability and deposition pattern in human airway, which should be considered in the evaluation of health risk associated with airborne particle exposure.