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R9 Laboratory SOP 490
Determination of Asbestos in Bulk Materials By Polarized Light Microscopy
Summary
This SOP applies to the examination of bulk materials for asbestos using polarized light microscopy. The bulk materials may include insulation materials, automotive brake materials, and a variety of other building materials suspected of containing asbestos fibers. This SOP is intended to be a qualitative technique that determines the presence (>1%) or absence of asbestos although volume percent estimates of the asbestos content can be made. It is intended for use with friable materials but can be used with materials such as tiles if fibrous components are clearly present and can be physically separated from the binder material. This SOP is based on the USEPA Interim Method for the Determination of Asbestos in Bulk Insulation Materials and ASTM Standard Method of Testing For Asbestos Containing Materials by Polarized Light Microscopy (ASTM D22.05) but does not address the point counting or the X-ray powder diffraction techniques described in the EPA method.
Samples are first examined at low power (10X-30X magnification) with a binocular microscope for homogeneity, the presence or absence of fibrous components, preliminary fiber identification and an estimation of fiber content. If no fibers are apparent with examination under low power, the absence of fibers is confirmed by examination by polarized light microscopy. If fibrous components are present, the sample is then subsampled and examined by polarized light microscopy using the central stop dispersion staining technique, cross polarization, and retardation to possibly identify the fibrous components and/or confirm the presence or absence of asbestos fibers.