Ken Takahashi's research while affiliated with Sydney Orthopaedic Research Institute and other places

Particles longer than 5 μm and with a length/diameter ratio >3 are defined as fibers. Asbestos or other fibers are still identified in residential environments due to the emission from asbestos‐used building materials. The respiratory system is the primary route of asbestos exposure; under a longer residence time, asbestos‐related adverse health effects are inevitable. Currently, asbestos fibers have been replaced with man‐made vitreous fibers (MMVFs); however, studies have revealed some similar biological effects of MMVFs with asbestos. Therefore, MMVFs‐induced diseases need to be determined by analyzing their deposition characteristics and foci in human respiratory tracts. In this study, we used computational fluid dynamics method to investigate fibers' airflow and deposition patterns in two realistic human respiratory models. Two drag models were used to predict the deposition of uniform 1 μm (asbestos) and 3.66 μm (carbon fiber‐CF) diameter, 15–300 μm long fibers. Two drag models provided comparable results with the experimental data. Comparatively, asbestos deposition was independent of fiber length, while CF deposition increased proportionally to fiber length. The highest level of local deposition was detected in the anterior nasal cavity. The results obtained from this study can extend current knowledge of human vitreous fiber exposure‐related lung diseases.

Fiber particles are generally defined as elongated particles with a length of more than 5 micron and a length/diameter ratio of greater than 3. Asbestos fibers, one of the representatives, have been proven to cause lung cancer, mesothelioma, and fibrosis. In recent years, because of their toxicity, asbestos fibers have been replaced by manmade vitreous fibers (MMVFs); however, studies have revealed some similarities in the biological effects of MMVFs and asbestos. Therefore, the risk of MMVF-induced diseases needs to be determined by finding the “hot-spot” deposition sites of the variably elongated fibers. Against this background, the current study involves performing the computational fluid dynamics (CFD) technique to investigate the deposition of MMVFs, such as carbon fibers, in two realistic human respiratory systems.