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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 (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 [2].
<br /> REFERENCES:
<br /> [1] Walton, W. H. 'The Nature, Hazards, and Assessment of Occupational Exposure to Airborne
<br /> Asbestos Dust:A Review," Ann. OCCUR. Hyg., 25, 115-247 (1982).
<br /> [2] Taylor, D. G., P. A. Baron, S. A. Shulman and J. W. Carter. 'Identification and Counting of
<br /> Asbestos Fibers," Am. Ind. Hva. Assoc. J. 45(2), 84-88 (1984).
<br /> [3] 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. Hyg., 25, 309-316 (1982).
<br /> [4] 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 /> [5] Baron, P. A. and G. C. Pickford. "An Asbestos Sample Filter Clearing Procedure," App1. �. Hyg., ,
<br /> 1:169-171,199 (1986).
<br /> [6] LeGuen, J. M. and S. Galvin"Clearing and Mounting Techniques for the Evaluation of Asbestos
<br /> Fibers by the Membrane Filter Method" Ann. Occup. Hyg. 24, 273-280 (1981).
<br /> [7] 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 /> [8] 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 /> S
<br /> NIOSH Manual of Analytical Methods(NMAM), Fourth Edition, 8/15/94
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