You are here:
EVALUATION OF ELECTRON MICROSCOPY FOR PROCESS CONTROL IN THE ASBESTOS INDUSTRY
Citation:
Gerber, R. AND R. Rossi. EVALUATION OF ELECTRON MICROSCOPY FOR PROCESS CONTROL IN THE ASBESTOS INDUSTRY. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-77/059 (NTIS PB266091), 1977.
Description:
The report gives results of an evaluation of the transmission electron microscope (TEM) and the scanning electron microscope (SEM) as potential tools for fine particle asbestos fiber counting for process control in the asbestos industry. The study defined the capabilities and limitations of the instruments in applications where asbestos specificity is not necessarily required, and where analysis cost must be minimal. The study showed that the microscopes are equally capable of counting all fibers in the full particle size distribution; but, for reasons of agglomeration and confusion with the filter texture, each microscope can observe only 75% of the distribution. In contrast, present standard light microscopy methods observe only the coarser 10% of the distribution, without resolving the fine fibers. Optimum asbestos fiber counting was done at 15,000 times magnification and at fiber concentrations on the filter between 40,000 and 80,000 fibers per sq mm. The minimum number of fibers counted to obtain high statistical confidence was 200 fibers per datum point. Standard techniques for filter sample preparation were found to have no effect for either instrument. Ashing of filters to remove non-asbestos fibers was responsible for 85% asbestos fiber loss.