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Tracheobronchial Particle Dose Considerations for In Vitro Toxicology Studies

Robert F. Phalen, Michael J. Oldham, André E. Nel

Toxicological Sciences, 2006

91 citations

Abstract

The purpose of this paper is to present a method for estimating particle doses that may be used to reconcile particle deposition doses used in in vitro toxicology studies with in vivo exposure levels. The focus is on the tracheobronchial (TB) tree of heavily exposed individuals. A review of the factors that influence inhaled particle deposition doses in environmental exposures leads to the identification of cases in which greater than average TB tree doses are received. Exercising individuals and those with chronic obstructive pulmonary disease not only inhale increased volumes of air but they also may have uneven ventilation that leads to greater than average particle deposition doses per unit of TB tree surface area. In addition, deposition hot spots, as occur at airway bifurcations, will greatly increase the particle exposures of target cells in the TB tree. Three particle exposure scenarios are proposed, and the average and local doses to the TB epithelium are calculated. When various factors that enhance particle doses (enhancement factors, or EFs) in vivo are considered, substantial particle doses may be justified for in vitro tissue culture studies that use TB target cells, such as epithelial cell cultures. The use of such EFs is intended to improve in vitro dosing with particles. Although the exposure of cells in vitro cannot fully replicate the complexity of in vivo exposures, it is possible to calculate toxicologically relevant doses that may define adverse health…

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