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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 - fbAFS - 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 (s,.) in an evaluation of mixed amosite and wollastonite fibers_ The estimate of the asbestos <br /> fraction, however, had a precision of 0.11 (s �). When this fraction was applied to the PCM count, the <br /> overall precision.of the combined analysis was 0.20 (21. <br /> REFERENCES: <br /> (11 Walton, W. H. 'The Nature, Hazards, and Assessment of Occupational Exposure to Airborne <br /> Asbestos Dust: A Review," Ann. Occup. Hyg., 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_ O. 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 /> 177-204 (1977)- <br /> (51 Baron, P. A_ and G_ C_ Pickford. "An Asbestos Sample Filter Clearing Procedure," Appl. Ind. HYq., <br /> 1:169-171,199 (1986). <br /> (61 LeGuen, J. M_ and S. Galvin "Clearing and Mounting Techniques for the Evaluation of Asbestos <br /> Fibers by the Membrane Filter Method" Ann. Occup. Hva. 24 273-280 (1981). <br /> (71 Yamate, G., S. A. Agarwal, and R. O. 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 /> NIOSH Manual of Analytical Methods(NMAM),Fourth Edition, 8115194 <br />