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ASBESTOS by TEM_ METHOD 7402, Issue 2, dated 15 August 1994 -Page 7 of 7 <br /> ! CALCULATIONS: <br /> ! 21. Calculate and report the fraction of optically visible asbestos fibers on the filter, <br /> (fs -fb)/(FS - Fb). Apply this fraction to fiber counts obtained by PCM on the same filter or on other <br /> filters for which the TEM sample is representative. The final result is an asbestos fiber count. The <br /> ! type of asbestos present should also be reported. <br /> 22. As an integral part of the report, give the model and manufacturer of the TEM as well as the model <br /> and manufacturer of the EDX system. <br /> ! EVALUATION OF METHOD: <br /> ! The TEM method, using the direct count of asbestos fibers, has been shown to have a precision of <br /> 0.275 (sr) in an evaluation of mixed amosite and wollastonite fibers. The estimate of the asbestos <br /> fraction, however, had a precision of 0.11 (s f). When this fraction was applied to the PCM count, the <br /> overall precision,of the combined analysis was 0.20 [21. <br /> REFERENCES: <br /> ! j11 Walton, W. H_ "The Nature, Hazards, and Assessment of Occupational Exposure to Airborne <br /> Asbestos Dust. A Review," Ann_ Occup. Hvq., 25, 115-247 (1982). <br /> [21 Taylor, D. G., P. A_ Baron, S. A. Shulman and J. W. Carter. "Identification and Counting of <br /> Asbestos Fibers," Am_ Ind. Hvq. Assoc. J. 45(2), 84-88 (1984)_ <br /> [31 Johnston, A. M_, A. D. Jones, and J. H. Vincent. "The Influence of External Aerodynamic Factors <br /> on the Measurement of the Airborne Concentration of Asbestos Fibers by the Membrane Filter <br /> Method," Ann. Occup. Hvq., 25, 309-316 (1982). <br /> [41 Zumwalde, R. D. and J_ M. Dement_ Review and Evaluation of Analytical Methods for <br /> Environmental Studies of Fibrous Particulate Exposures, NIOSH Technical Information Bulletin <br /> !€77-204 (1977). <br /> [51 Baron, P. A. and G. C. Pickford. "An Asbestos Sample Filter Clearing Procedure," Appl. Ind. IHyg., <br /> 1:169-171,199 (1986). <br /> j61 LeGuen, J. M. and S. Galvin "Clearing and Mounting Techniques for the Evaluation of Asbestos <br /> Fibers by the Membrane Filter Method" Ann. Occup_ Hvq. 24 273-280 (1981). <br /> [71 Yamate, G., S. A_ Agarwal, and R. D. Gibbons. "Methodology for the Measurement of Airborne <br /> Asbestos by Electron Microscopy," EPA Contract No. 68-02-3266 (in press). <br /> ! [81 Steel, E. B. and J. A_ Small. "Accuracy of Transmission Electron Microcopy for the Analysis of <br /> Asbestos in Ambient Environments," Anal_ Chem., 57, 209-213 (1985). <br /> ! METHOD REVISED BY: <br /> Paul A. Baron, Ph.D.; NIOSH/DPSE. <br /> ! <br /> ! <br /> ! <br /> ! <br /> ! NIOSH Manual of Analytical Methods(NMAM),Fourth Edition,8115194 <br />