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PLM by EPA 600/R-93/116





Laboratory Equipment

PLM by EPA 600/R-93/116

In 1993, EPA developed an improved test method entitled ``Method for the Determination of Asbestos in Bulk Building Materials'' (EPA/600/R-93/116).

The test method provides clarifications and improvements to the 1982 EPA ``Interim Method for the Determination of Asbestos in Bulk Insulation Samples'' (as found in 40 CFR part 763 Appendix A to Subpart F).

Specifically, use of the improved method can provide more precise analytical results especially at low asbestos concentrations, enhanced analysis of floor tiles which may contain thin asbestos fibers below the limits of resolution of the polarized light microscope (PLM), and clearer instruction on the analysis of bulk materials, particularly where multiple layers are present.

The 1982 method is limited in that it does not provide guidance for analyzing materials that contain thin (<0.25 micrometers) asbestos fibers. As a consequence, floor tiles which were analyzed according to the 1982 method and for which negative results were reported may actually contain undetected asbestos.

The test method includes improved procedures for reducing matrices so that fibers may be made available for microscopic analysis.

The improved method also directs laboratories to analyze the individual strata or layers and report a single result for each layer. The 1982 method provided that the analytical result for a multi-layered sample with discrete strata be reported as one result across all layers. Because the 1982 method allowed the result to be reported as one number, multi-layered samples which may contain asbestos in a single layer may have been reported by laboratories as non-asbestos-containing. The improved method directs laboratories to analyze and report a result for individual layers. Thus, more than one result will be reported for multi-layered samples, and a multi-layered sample which previously was determined to be non-asbestos-containing may now have layers which will be classified as asbestos-containing based on the presence of asbestos in greater than 1 percent.

In light of the availability of the improved method, EPA recommends that local education agencies (LEAs) use the improved method in place of the 1982 procedures as found in 40 CFR part 763 Appendix A to Subpart F. EPA has made the determination that the improved method is more capable of producing accurate results than the 1982 protocol and thus serves as a preferred substitute method. Further, EPA recommends that LEAs which have PLM laboratory results indicating floor tiles to be non-asbestos-containing (asbestos present in less than or equal to 1 percent) reconsider whether these materials may have thin asbestos fibers. LEAs should also consider whether other materials sampled previously may contain multiple layers, whether each of these layers was analyzed separately, and whether results were reported separately by layer. (Note: For purposes of this analysis, drywall or gypsum board is considered a single-layered material.) LEAs are encouraged to determine from sampling and analysis records whether multi-layered systems were sampled and analyzed separately. (A system is an integrated group of building components which form a unit, i.e., a wall system composed of a brown coat layer as well as other plaster layers.) Although there is no modification of the AHERA requirements at this time and results obtained by following the 1982 protocol and the AHERA sampling rules meet the AHERA legal requirements, it may be prudent for LEAs to assume floor tiles and multi-layered materials with previously negative results to be asbestos-containing or resample and analyze them by the 1993 EPA Test Method.

This approach should be considered for the following circumstances: (1) Floor tiles which may contain thin fibers and which were analyzed under the 1982 PLM method and found not to be asbestos-containing; and (2) materials such as hard wall and acoustical plaster, stucco or other similar multi-layered materials or systems which were not analyzed and reported by layers (discrete strata). LEAs are reminded that they are also required to comply with the asbestos NESHAP regulation when disturbing asbestos-containing building materials. Although building owners/operators are not required by the asbestos NESHAP to collect bulk samples of building products prior to disturbance, they are responsible for knowing whether asbestos is contained in the building product. Often, identification of asbestos content may be obtained only by sampling and analyzing the material.



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