COAL DUST, >5%
OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
CAS: None; Chemical Formula: None
OSHA's former limits for coal dust included a formula limit of 10 mg/m3/% SiO(2)+2 for coal dust containing a respirable quartz fraction greater than 5 percent and a 2.4 mg/m3 limit for coal dust containing a respirable quartz fraction of less than 5 percent. The ACGIH has a TLV-TWA of 0.1 mg/m3 for the respirable quartz fraction of coal dust containing more than 5 percent quartz, and 2 mg/m3 for the respirable dust fraction of coal dust containing less than 5 percent quartz. OSHA proposed 8-hour TWA limits of 0.1 mg/m3 for the respirable quartz fraction of coal dust containing more than 5 percent quartz and 2 mg/m3 for the respirable dust fraction containing less than 5 percent quartz; the final rule establishes these limits. OSHA's proposed and final rule limits do not represent an actual change in the value of the limits for coal dust containing more than 5 percent respirable quartz; instead, they do away with the Agency's previous and cumbersome formula limit. Coal is a dark brown to black solid formed from fossilized plants.
Because OSHA is not lowering the limits for coal dust or considering the health effects evidence for these limits but is merely changing the form in which the limits are expressed, no discussion of the health evidence is included in the final rule. The Gulf Power Company (Exs. 3-938 and 3-1144) believed that OSHA was proposing to change the value of the coal dust limits rather than the form in which those limits were being expressed. In the final rule, OSHA has clarified this fact by emphasizing it in the beginning and end of this discussion. Lawrence Hecker, Corporate Director of Industrial Hygiene and Toxicology for Abbott Laboratories, requested that both Z-table entries for coal dust in the final rule specifically indicate that it is the "respirable quartz fraction" that is to be measured (Ex. 367f, p.9). In response to this comment, OSHA intended to identify the "respirable fraction" in the final rule Z-1-A table since OSHA's intent was only to simplify the units and not make any substantive changes (see last paragraph of discussion on coal dust). The suggested change by Mr. Hecker (respirable quartz fraction) would result in up to an order of magnitude increase in the PEL for a highly toxic substance.
NIOSH (Ex. 8-47, Table N2; Tr. p. 3-86) believes that the limit for quartz-bearing coal dust should be reduced to 0.05 mg/m3 as an 8-hour TWA on the basis of the potential carcinogenicity of respirable crystalline silica. OSHA is aware of some recent studies (NIOSH 1986b; Hurley and Maclaren 1987; IARC 1987) on the health effects of exposure to coal dust, and the Agency is monitoring this literature to assess the need for a reevaluation of this limit.
In the final rule, OSHA is establishing an 8-hour TWA PEL of 0.1 mg/m3, measured as the respirable dust fraction, for coal dust having a respirable quartz fraction of more than 5 percent quartz, and an 8-hour TWA PEL of 2 mg/m3 TWA, measured as the respirable dust fraction, for coal dust having a respirable quartz fraction of less than 5 percent quartz. The Agency's previous formula limit for silica containing more than 5 percent quartz (respirable fraction) is equivalent to the 0.1 mg/m3 limit in terms of airborne concentration. Thus, the final rule's limit is intended to simplify the units used to measure and express the limit; it does not represent an actual change in the value of the limit (see discussion for crystalline silica-quartz later in this section). OSHA believes that this revision will simplify employee exposure monitoring.
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