Asbestos simulation studies

Paustenbach, D. J., Madl, A. K., Donovan, E., Clark, K., Fehling, K., and Lee, T. C. (2006). Chrysotile asbestos exposure associated with removal of automobile exhaust systems (ca, 1945-1975) by mechanics Results of a simulation study. J Expo Sci Environ Epidemiol 16, 156-171. 

Report the area occluded by asbestos as the concentration. This estimate does not generally take into consideration the difference in density of the different species present in the sample. For most samples this is adequate. Simulation studies with similar materials must be carried out to apply microvisual estimation for that purpose and is beyond the scope of this procedure. 

In order to define the extent of emissions from automotive brakes and clutches, a study was carried out in which specially designed wear debris collectors were built for the dmm brake, the disk brake, and the clutch of a popular U.S. vehicle (1). The vehicle was driven through various test cycles to determine the extent and type of brake emissions generated under all driving conditions. Typical original equipment and aftermarket friction materials were evaluated. Brake relines were made to simulate consumer practices. The wear debris was analyzed by a combination of optical and electron microscopy to ascertain the asbestos content and its particle size distribution. It was found that more than 99.7% of the asbestos was converted to a nonfibrous form and... 

Lu J, Keane MJ, Ong T, et al. 1994a. In vitro genotoxicity studies of chrysotile asbestos fibers dispersed in simulated pulmonary surfactant. Mutat Res 320(4) 253-259. 

A test simulating a leak in a loop was made to study this phenomenon. A 2 % Cr-1% Mo steel pipe was filled with Bi containing 1000 ppm U, 350 ppm Mg, and 250 ppm Zr. A 1 /32-in. hole was drilled in the pipe below the Bi level. A patch of asbestos tape 2 in. in diameter was put over the hole. The tube was then heated to 594°C and pressurized to 5 psi to force out a small amount of Bi. The pressure was dropped as soon as some Bi had leaked out and the tube was then heated at 594°C for 1025 hr. The appearance of the pipe underneath the asbestos tape patch and a cross section of the oxidized area are shown in Fig. 21-11. A complete oxidation through the pipe wall has occurred in the area adjacent to the leak. 

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