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Inhaled fibers can potentially cause inflammation of the lung tissue and interstitium, which after long-term exposure may lead to lung cancer, malignant mesothelioma, or pulmonary and pleural fibrosis. To reduce the risk and set the appropriate occupational hygiene regulations, it is important to be able to precisely calculate the fate of inhaled fibers depending on their physical characteristics and inhalation conditions. In the absence of experimental data on the real behavior - trajectories, orientation and flipping - of inhaled fibers, a new test rig was assembled for visualization and recording of flowing fibers in a replica of the human trachea and the first bronchial bifurcation. Fibers prepared from commercially produced glass fibers have been processed, dispersed, and introduced into the airway replica. Visualization was performed using a powerful LED light and a high-speed camera. The flow of fibers was evaluated upstream and downstream of the realistic asymmetrical bifurcation and dependence on flow conditions was sought. The fractions of parallelly and perpendicularly flowing fibers were statistically evaluated in three locations. The frequency of flipping was also analyzed. The results show that the parallel orientation of the fibers is less dominant than expected. The fiber orientation tables for various conditions can be used to adjust and improve computational simulations of inhaled fibers in the human airways. [ABSTRACT FROM AUTHOR]

Inhalation of aerosols generated by electronic cigarettes leads to deposition of multiple chemical compounds in the human airways. In this work, an experimental method to determine regional deposition of multicomponent aerosols in anin vitrosegmented, realistic human lung geometry was developed and applied to two aerosols, i.e. amonodisperse glycerol aerosoland amulticomponent aerosol. The method comprised the following steps: (1)lung cast model preparation, (2)aerosol generation and exposure, (3)extraction of deposited mass, (4)chemical quantificationand (5)data processing. The method showed good agreement with literature data for the deposition efficiency when using amonodisperse glycerol aerosol, with a mass median aerodynamic diameter (MMAD) of 2.3 μm and a constant flow rate of 15 L/min. The highest deposition surface density rate was observed in the bifurcation segments, indicating inertial impaction deposition. The experimental method was also applied to the deposition of a nebulizedmulticomponent aerosolwith a MMAD of 0.50 μm and a constant flow rate of 15 L/min. The deposited amounts of glycerol, propylene glycol and nicotine were quantified. The three analyzed compounds showed similar deposition patterns and fractions as for themonodisperse glycerol aerosol, indicating that the compounds most likely deposited as parts of the same droplets. The developed method can be used to determine regional deposition for multicomponent aerosols, provided that the compounds are of low volatility. The generated data can be used to validate aerosol deposition simulations and to gain insight in deposition of electronic cigarette aerosols in human airways. [ABSTRACT FROM AUTHOR]

Man-made vitreous fibers (MMVFs) are noncrystalline substances made of glass, rock or slag and are widely used as thermal or acoustic insulation materials. There is continued concern about their potential health impacts and thus, their dosimetry and behavior in the environment still require study using filters to collect fiber samples. After deposition or exposure measurements of MMVFs it is often necessary to analyze the filters with deposited fibers. This task is tedious, time-consuming, and requires skill. Therefore, many researchers have tried to simplify or automatize fiber detection and quantification. This article describes features of our in-house software, which automatically detects and counts fibers in images of filter samples. The image analysis is based on the use of a histogram equalization and an adaptive radial convolution filter that enhances fiber contrast and thus, improves the fiber identification. The accuracy of the software analysis was verified by comparison with manual counting using ordinary phase-contrast microscopy method. The correlation between the methods was very high (coefficient of determination was 0.977). However, there were some discrepancies caused by false identifications, which led to implementation of manual corrective functions. Copyright © 2016 American Association for Aerosol Research [ABSTRACT FROM PUBLISHER]