You are here:
MICRO DOSE ASESSMENT OF INHALED PARTICLES IN HUMAN LUNGS: A STEP CLOSER TOWARDS THE TARGET TISSUE DOSE
Citation:
Kim, C. S., Z. Zhang, AND C. Kleinstruer. MICRO DOSE ASESSMENT OF INHALED PARTICLES IN HUMAN LUNGS: A STEP CLOSER TOWARDS THE TARGET TISSUE DOSE. Presented at American Thoracic Society Meeting, Orlando, FL, May 21-26, 2004.
Description:
Rationale: Inhaled particles deposit inhomogeneously in the lung and this may result in excessive deposition dose at local regions of the lung, particularly at the anatomic sites of bifurcations and junctions of the airways, which in turn leads to injuries to the tissues and adverse biological effects. Local dose enhancement is manifested particularly in patients with obstructive airway disease. Methods: To examine the nature and extent of uneven dose distribution, we measured deposition patterns in 3-generation airway models (G3-G5) for different size particles (3-6 micron diameter) at various flow distribution conditions between two contralateral bifurcations. Deposition was obtained at each bifurcation zone as a function of particle size and flow rate. Based on the experimental data, a computational fluid dynamic (CFD) model consisting of 7-generation airways (G3-G9) was developed to assess detailed dose variations and micro-dose information within the airway network. Results: Deposition was found mainly at each bifurcation zone regardless of particle sizes and flow rates used. Deposition ratios between two contralateral bifurcations were either < or > than the flow ratio depending on the level of particle inertia. In CFD simulations, max/min flow ratios were < 2. In contrast, deposition varied widely (5-20 times) indicating a magnifying role of flow variation on local deposition dose. Micro-dose analysis shows peak local dose can be as high as 300 ? 1000 times the average dose at each airway generation. Conclusions: Local dose at micro surface area can be orders of magnitude greater than the average dose in the airways during normal breathing. Micro-dose information can be more realistically related to local tissue dose and may be useful for understanding the initial particle ?tissue interaction and for formulating improved risk assessment procedures to provide the maximum protection of public health from exposure to pollutant particles. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.