Modeling transport and evolution of aerosols for accurate predictions of local deposition in an in-vitro exposure system

Authored by  A Kuczaj, M Nordlund, S Majeed, S Frentzel, M Peitsch, J Hoeng

Presented at SRNT 2015 21st Annual Meeting     


Humans are continuously exposed to aerosols and depending on the physical and chemical properties of them, the exposure can be neutral, therapeutic or pose a potential health hazard. Understanding physical conditions that govern deposition of aerosol droplets and its influence on the cell function is a key step towards the ultimate goal to relate the exposure of inhaled and deposited aerosols to health outcomes. We present here our approach to model the transport and evolution of aerosols that undergo dynamic changes due to simultaneously altered physical conditions along the flow path in a geometry frequently used in in-vitro exposure systems. The acquired knowledge will further strengthen the non-animal safety testing approaches for consumer safety risk assessments related to aerosols, which are aligned with the new directions of the Toxicity Testing in the 21st Century guidelines.Deposition of aerosol is governed by the various physical mechanisms (i.e., diffusion, impaction, interception, sedimentation), and implicitly is also dependent on the flow and surrounding aerosol particles’ thermal conditions. This is in particular important when considering that aerosols consisting of liquid droplets are being diluted with air as they may still evolve. Using Computational Fluid Dynamics, a computational model of an in-vitro system was constructed, in which we considered flow with embedded droplets characterized by its mean size droplet diameter. The simulations took in account fully coupled equations for mass, momentum and energy in the Eulerian-Eulerian framework as well as one-way coupling of gas phase and liquid phase (droplets).The influence of flow on the transport and evolution of liquid aerosol droplets flowing in an in-vitro exposure system will be addressed. Simultaneously the numerical investigation of impaction and gravitational settling for various flow rates and droplet diameters will be presented. Aerosol aging and stability will be assessed, which has a particular importance for the uniformity of aerosol deposition at consecutive wells where cell cultures inserts are present and exposed to substances of interest.Key words: Technology, ToxicologyTopic: Basic Science