Review of the U.S. Navy's Exposure Standard for Manufactured Vitreous Fibers (2000) / Chapter Skim
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7 Evaluation of the Navy's Exposure Standard
7 Evaluation of the Navy's Exposure Standard
Pages 51-58
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From page 51... ...
The exposure standard of 2 f/cm3 was based on the systematic adoption or incorporation of existing laws and standards as defined in the Navy's 1994 OccupationaZ Safety and Health Program Manual (CNO 1994~. As stated in the manual, "...instructions based on these standards may simply refer to a specific Occupational Safety and Health Administration (OSHA)
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From page 52... ...
In January 1999, the Navy revised its Occupational Safety and Health Program Mar~uaZ, changing the occupational exposure limit for MVF to the American Conference of Governmental Industrial Hygienists (ACGTH) threshold limit value (TEV)
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From page 53... ...
Although the Navy's document reviews much of the relevant literature on physical, chemical, toxicological, and epidemiolog~cal data on MVF, the Navy did not conduct the kind of systematic analysis, integration, and thorough evaluation of alternative arguments that are necessary for the kind of scientifically based risk analysis within which the Navy hopes to couch its exposure standards. Nor was the Navy able to find the scientific justification that it sought for its proposed standard through reference to a rigorous risk analysis conducted and documented by another organization.
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From page 54... ...
needs to be examined, and potential alternatives need to be explored. · Existing analyses focus on tumorigenicity, but fibrosis, bronchitis, and other potential chronic noncancer responses might be important in evaluating the health protectiveness of a fiber exposure standard.
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From page 55... ...
The subcommittee notes, however, that none of the existing MVF exposure limits is based on a quantitative analysis of risks of any chronic respiratory disease, including cancer. TABLE 7-1 Occupational Exposure Limits for MVF Country Australia Canada (Alberta)
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From page 56... ...
The subcommittee notes that although a 1-f/cm3 standard is appropriate for MVF that include conventional glass fibers and rock and slag wools, it is unlikely to be sufficiently protective for MVF that are more biopersistent or have a high proportion of respirable fibers that are much smaller in diameter than the conventional glass fibers and rock and slag wools, which average at least 6 ,um. For instance, some RCF and other durable MVF are sufficiently biopersistent to warrant a more restrictive exposure limit.
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From page 58... ...
For RCF that have experienced repeated thermal stress, the resulting airborne fibers can have altered physical and chemical properties, including length distributions and crystalline forms that affect their biopersistence (TIMA 1993, p.
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