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Return to Advocacy > Regulatory Comments > National Institute for Occupational Safety and Health (NIOSH)
September 30, 2008
Ms. Diane Miller
NIOSH Docket Office
Robert A. Taft Laboratories
4676 Columbia Parkway, MS C-34
Cincinnati, OH 45226
RE: Revised Draft Document: Asbestos and Other Elongated Mineral Particles: State of the Science and Roadmap for Research; NIOSH Docket Number NIOSH-099A
Dear Ms. Miller:
The Industrial Minerals Association – North America (IMA-NA) is a Washington, DC-based trade association created to advance the interests of North American companies that mine or process minerals used throughout the manufacturing and agricultural industries. IMA-NA membership also includes companies that provide equipment and services to the industry.
IMA-NA has reviewed the above-referenced Revised Draft Document (revised Roadmap) developed by the National Institute for Occupational Safety and Health (NIOSH) and is pleased to offer the following comments. At the outset, IMA-NA reminds NIOSH that it previously submitted comments on its initial draft document: Asbestos and Other Mineral Fibers: A Roadmap for Scientific Research (NIOSH Docket Number NIOSH-099)(Roadmap). IMA-NA incorporates by reference its previous submission as part of these comments.
IMA-NA again wishes to commend NIOSH for the contributions it has made to promoting occupational safety and health. The NIOSH revised Roadmap document on asbestos, particularly those sections related to the scientific research framework, has the potential to make additional contributions in the area of occupational health, but requires modification, specifically with regard to the pronouncement of NIOSH policy.
IMA-NA is on record as supporting regulatory changes to better protect workers potentially exposed to asbestos hazards on the job, particularly miners. For instance, IMA-NA concurs with the key provisions of the Mine Safety and Health Administration’s (MSHA) final rule updating its regulation of asbestos. Specifically, IMA-NA supports the reduction of the MSHA permissible exposure limit (PEL) for full-shift exposures and the excursion limit earlier adopted for asbestos by the Occupational Health and Safety Administration (OSHA). IMA-NA further supports the continued use of phase contrast microscopy (PCM) for initial quantification of asbestos fibers in air with the use of transmission electron microscopy (TEM) as needed to aid in the identification of asbestos. IMA-NA also supports MSHA’s approach to control take-home asbestos contamination on work clothing.
In aligning its final rule with the OSHA asbestos standard, MSHA accepted OSHA’s risk assessment in lieu of conducting its own. However, IMA-NA supported the inclusion of other asbestiform amphibole minerals if they clearly demonstrate a health risk similar in magnitude and scope to the asbestiform amphiboles currently regulated as asbestos and to which miners are exposed. It also supported extension of the rule to all mining environments.
With this background in mind, IMA-NA believes that NIOSH made a significant mistake by inappropriately expanding the scope of the draft Roadmap from a proposed pathway for scientific research to a hybrid document incorporating broad statements of NIOSH policy. In the process NIOSH has injected its own perception of the state of the science and colored the proposed research agenda.
The draft revised Roadmap now is cast as a Current Intelligence Bulletin. According to the NIOSH Web site, Current Intelligence Bulletins “review and evaluate new and emerging information about occupational hazards.” IMA-NA finds this at odds with the stated goal of the Roadmap and revised Roadmap:
The purpose of the Roadmap is to outline major areas of controversy and to recommend a research framework that can serve as a guide for the development of specific research programs within and across disciplines. The intended goals of the research to be undertaken are to provide answers to current scientific questions, reduce scientific uncertainties, and provide a sound scientific foundation for future policy development so that optimal health protection can be assured.
IMA-NA fully supports this statement of the Roadmaps’ intended purpose, but objects to NIOSH putting the policy “cart” before the science “horse.” For instance, NIOSH uses the draft revised Roadmap document as the vehicle to revise its recommended exposure limit (REL) for asbestos and expand its scope specifically to include elongated mineral particles (EMPs). Where the initial draft document was primarily a research roadmap, once finalized the revised draft document would assume regulatory consequence. OSHA and MSHA are statutorily required to propose NIOSH RELs, typically contained in criteria documents, as permissible exposure limits (PELs) or formally announce their reasons for not doing so. Moreover, legislation currently pending in Congress would mandate that MSHA adopt NIOSH RELs as PELs. Discussion of the NIOSH REL, as currently constituted or as revised, has no place in a scientific research roadmap.
The draft revised REL makes clear that even though EMPs included in the count are not necessarily asbestos fibers, they will be treated as if they are asbestos fibers. It was IMA-NA’s impression that the purpose of the Roadmap and revised Roadmap documents is to provide answers to just these types of current scientific questions. Consequently, IMA-NA recommends a return to the original and proper purpose of the Roadmap document, namely providing a framework for scientific research. NIOSH should refrain from casting the revised Roadmap document as a Current Intelligence Bulletin and refrain from using it as a vehicle for rendering policy pronouncements, such as the proposed revision to the REL for asbestos fibers.
In its previous comments IMA-NA took exception to the term “fiber-like” cleavage fragments that NIOSH utilized throughout the Roadmap document. IMA-NA remarked that the term was a misnomer and was misleading, and that its continued inadvertent and improper use might lead to treating elongated amphibole cleavage fragments as asbestos fibers. Specifically, IMA-NA was concerned about the possible application of arbitrary fiber-counting criteria to “define” asbestos rather than to simply count asbestos fibers once identified. This unintended outcome would run counter to cleavage fragment health science. In light of the NIOSH proposed revision of the REL for asbestos fibers, that concern appears well founded.
NIOSH did drop use of the “fiber-like” descriptor in the revised Roadmap, but instead of recognizing a distinct difference between asbestos fibers and cleavage fragments NIOSH coined an entirely new descriptor: “elongated mineral particles” (EMPs). The bright-line distinction IMA-NA believes the draft Roadmap and revised Roadmap should convey regrettably continues to be obscured because EMPs include both asbestos fibers and cleavage fragments. Although NIOSH dropped its “unified theory” from the revised Roadmap, it continues to link asbestos fibers and cleavage fragments. NIOSH should refrain from linking the two by conjoining “asbestos fibers” and “elongated mineral particles” with the phrase “and other.” IMA-NA recommends that NIOSH address asbestos fibers and cleavage fragments separately. We once again refer NIOSH to the comments on the “cleavage fragment issue” IMA-NA previously submitted on the draft Roadmap document (see pages 2-6 and accompanying attachments).
What is needed is development of an analytical method, likely involving a series of analytical steps and clearer definitions, which can distinguish between asbestos fibers and cleavage fragments. The revised Roadmap recognizes this need and it should be made a top research priority. For instance, polarized light microscopy (PLM) always has been used to identify minerals, mineral types, and mineral habit characteristics prior to and during development of x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Its continued use should not be discounted. Similarly, more advanced techniques, such as SEM, may offer promise in differentiating asbestos fibers and cleavage fragments. NIOSH should investigate use of the full suite of analytical tools available to lend precision to the mineral identification process. NIOSH then could establish an REL specific to asbestos fibers. Importantly for the industrial minerals industry, development of such an analytical method would preclude nonasbestiform cleavage fragments from being improperly characterized as asbestos fibers.
IMA-NA disagrees with the conclusion in the draft revised Roadmap that the epidemiological studies previously conducted on worker populations exposed occupationally to nonasbestiform analogs of asbestos varieties are inconclusive. These studies generally can be considered negative for asbestos-related disease.
Several peer reviewers of the draft Roadmap document commented that new epidemiological studies of asbestos-exposed populations would be of limited value because exposure to asbestos fibers had decreased markedly over the years. In contrast, worker populations continue to be exposed to cleavage fragments, although these exposures likewise have decreased over the years. Rather than relying exclusively on in vitro and in vivo toxicological testing to determine conclusively whether cleavage fragments cause the same health effects as asbestos fibers, the revised Roadmap should express a strong preference for epidemiological studies of worker populations exposed occupationally to nonasbestiform analogs of asbestos varieties to make this determination. These studies should be rigorously designed to minimize confounding variables and resolve definitively, to the extent possible, the issue of whether exposures to nonasbestiform analogs of asbestos varieties produce the same health effects as asbestos fibers. Given diverse geology special care must be taken to properly characterize the mineral exposures involved in these epidemiological studies.
In vitro and in vivo studies of the various nonasbestiform analogs can help determine whether additional epidemiological studies are even necessary. Properly designed toxicological studies, utilizing properly characterized materials (examining such characteristics as mineral composition, dimension, biopersistence, surface chemistry, etc.) could help inform issues of relative mineral particle toxicity. IMA-NA believes the existing in vitro and in vivo studies that address nonasbestiform elongated mineral particulate consistently demonstrate a difference in biologic effect when contrasted with asbestos fibers. However, in light of the existing negative epidemiological studies, IMA-NA takes exception to the exclusive use of in vitro and in vivo toxicological testing to definitively determine whether EMPs cause the same adverse health effects as asbestos fibers.
Finally, in its response to the peer reviewers of the initial draft Roadmap document, NIOSH indicated that it currently was exploring having the revised Roadmap document reviewed by the National Academies of Sciences (of which the Institute of Medicine is a component). IMA-NA endorses such a high-level scientific review to validate the scope and direction of the NIOSH research agenda relative to asbestos fibers and nonasbestiform cleavage fragments. IMA-NA encourages NIOSH to pursue this additional review and would be pleased to assist the National Research Council/Institute of Medicine committee in whatever way it can.
In summary IMA-NA believes the revised Roadmap document should be a pathway for scientific research exclusively and not comingled with a NIOSH policy document with its regulatory consequences. Care must be taken to not inadvertently and improperly blur the distinction between asbestos fibers and cleavage fragments. Consequently, the research agenda should include development of an analytical method specific to asbestos that can distinguish nonasbestiform cleavage fragments from asbestos fibers. Lack of such a discerning analytical technique poses a significant problem for the mining community (especially with a reduced PEL for asbestos fibers) and hampers the ability to perform meaningful risk assessment. Cleavage fragments do not produce the same health effects as asbestos fibers. However, to the extent that questions remain concerning the health effects posed by exposure to cleavage fragments, carefully designed toxicological and epidemiological studies can help inform subsequent policy development.
Respectfully submitted,
Mark G. Ellis
President
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