Regulated Asbestos Analysis: EPA Polarized Light Microscopy Method and the Implications for Reported Fiber Sizes

I recently reviewed the article entitled, “Health Effects of Censored Elongated Mineral Particles, a Critical Review” by Egilman et al. ¹ The article provides an excellent summary of very complex issues faced by those involved with asbestos fiber measurement and the potential ramifications to health effects. Furthermore, the article does a great service to the professionals who will utilize this information in that it provides comparative data regarding what is generated as to data obtained by selected methodologies. A compounding issue facing interpretation of data from laboratories has been defined in a Federal Register notice (Fed. Reg/Vol 85, No. 7/Friday, January 10, 2020/Notices) regarding a meeting sponsored by the U.S. Food and Drug Administration (FDA). The notice acknowledged that “… different conclusions as to whether asbestos and other potentially harmful EMPs [Elongated Mineral Particles] are present when testing consumer products.” ² Egilman et al. define the limits of detection/sensitivity of commonly used laboratory protocols/instrumentation, particularly as applicable to selected applications. In that regard, I would offer supplemental information to the section that described utilization of polarized light microscopy (PLM) in assessment for the presence and percent of asbestos in bulk samples.

Specifically, on page 216 of Egilman et al. in the section defined as “What is Counted by Current Methods,” there is a list of methods on Table 11. The intent was to demonstrate that various methods, specifically focused on PLM and phase contrast light microscopy, have inherent limitation in detection of a population of certain sized fibers commonly found in samples and which the authors consider potential pathogens. Of interest, there is one focus specifically on the U.S. Environmental Protection Agency (EPA) PLM method EPA/600/R-93/116 (Method for the Determination of Asbestos in Bulk Building Materials, referred to as the 93 method). Definitions found in the method are offered on page 219.

I would offer as supplemental information that for EPA compliance (Asbestos National Emission Standard for Hazardous Air Pollutants (NESHAP) Regulations (40 CFR Part 61, Subpart M) and the Asbestos-Containing Materials in Schools Rule (40 CFR Part 763, Subpart E, commonly referred to by the statue title The Asbestos Hazard Emergency Response Act, or simply, AHERA), the “93 method” is not the method of requirement. Most asbestos lab work in this country is not conducted in research laboratories. It is conducted within the working/accredited PLM laboratories analyzing an untold number of building material samples per year generated by accredited asbestos inspectors performing building surveys as defined under EPA/Occupational Safety and Health Administration (OSHA) and/or applicable state/local program-defined regulatory guidance documents. For their clients to be in compliance with these rules, and specifically in compliance with National Institute for Standards and Technology Voluntary Laboratory Accreditation Program- (NIST-NVLAP or simply NVLAP) accredited PLM laboratories, the method of requirement is Section 1 of Appendix E to Subpart E of Part 763-Interim Method of the Determination of Asbestos in Building Insulation Samples. The method is not listed or defined by reference in Table 11 and can be found at https://www.govinfo.gov/content/pkg/CFR-2010-title40-vol30/pdf/CFR-2010-title40-vol30-part763-subpartE-appE.pdf.

This method (hereinafter Appendix E to Subpart E) is a somewhat updated version of what we used to call the “82 method” (EPA 600/M4-82–020); this was the EPA’s original required PLM method for compliance with their rules. Importantly, the 93 method was never “codified” or formally inserted into the EPA regulation appendix replacing Appendix E to Subpart E of 40 CFR Part 763. So effectively, the 93 method is an option for additional techniques, not the method required by EPA regulations. This is not generally understood by parties outside of those intimate with commercial analysis by accredited PLM laboratories. Even within that group, many were not aware of this issue. In the past couple of years, the NVLAP program changed their accreditation certificates to reflect the required method. In the United States, the majority of asbestos bulk sample analysis/PLM laboratories are accredited by NVLAP.

This is important for many reasons including the issues Dr. Egilman raises in his paper. NVLAP-accredited laboratories cannot merely cite the 93 method on their reports; this is not compliant to the EPA AHERA and asbestos NESHAP rules. Nor can they cite the original “82 method” for the same reasons. Furthermore, in the Appendix E to Subpart E method, there is very little information about fiber geometry … from the method:

1.7.2.4 Quantitation of Asbestos Content

For the purpose of this method, “asbestos fibers” are defined as having an aspect ratio greater than 3:1 and being positively identified as one of the minerals in Table 1–1. ³

This is the only “fiber” definition in this method; no length requirements or discussion about fiber widths. The fiber geometry issues Dr. Egilman cites in his paper from the 93 method are inapplicable for regulated EPA AHERA and NESHAP work, as with 20–100:1 aspect ratio and others metrics. Actually, this makes Dr. Egilman’s case even better for method limitations in that 93 would not take into consideration the shorter fibers. The Appendix E to Subpart E method does (as with fibers with an aspect ratio >3:1), provided laboratories follow that requirement and not the 93 method geometries.

In the context of the publication by Egilman et al., I have always found this comment interesting from the required PLM method:

1.7.2.2 Sample Preparation

… A mortar and pestle can sometimes be used in the size reduction of soft or loosely bound materials though this may cause matting of some samples. … Periodic checks of the particle sizes should be made during the grinding operation so as to preserve any fiber bundles present in an identifiable form. These procedures are not recommended for samples that contain amphibole minerals or vermiculite. Grinding of amphiboles may result in the separation of fiber bundles or the production of cleavage fragments with aspect ratios greater than 3:1. Grinding of vermiculite may also produce fragments with aspect ratios greater than 3:1. (underline added) ³

It seems that this caveat is in line with the censorship premise as discussed.

I offer this commentary not as criticism, but to help illuminate the additional realities associated with the governance of regulated work, which is very structured to the described specified method. Any other PLM method (National Institute for Occupational Safety and Health (NIOSH) or OSHA) is not applicable to EPA regulated work, which is the bulk type of analysis carried out in this country—not research or that which is only OSHA-related. Almost all commercial asbestos-control work in this country is regulated under EPA’s asbestos NESHAP and to a lesser degree AHERA requirement. This is important because in the context of Dr. Egilman’s studies here, those interpretations that only focus on the 93 method do dismiss the smaller fibers and this would be noncompliant to existing EPA rules resulting in a “censoring” regarding the content of smaller fibers that may be present and/or observed during analysis. From firsthand conversations with senior Washington, DC, EPA staffers, the 93 method will likely never formally replace Appendix E to Subpart E.