GRAPHITE, NATURAL

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: 7782-42-5; Chemical Formula: None

The former OSHA limit for natural graphite (total dust) was 15 million particles per cubic foot (mppcf), which is equivalent to 2.5 mg/m³ as respirable dust (assuming that respirable mass is one-half total particle mass). The proposed PEL was 2.5 mg/m³ for respirable natural graphite dust containing less than 1 percent quartz; NIOSH (Ex. 8-47, Table N1) concurred with this limit, and the final rule promulgates it. The ACGIH has a graphite TLV of 2.5 mg/m³ for respirable dust containing less than 1 percent quartz. Graphite is a mineral substance that is best known for its use as the “lead” in pencils.

Early reports established that graphite deposited in the lungs of occupationally exposed workers caused pneumoconiosis (Koopman 1924/Ex. 1-131). Subsequent research described the condition produced by exposure to graphite as anthracosilicosis, a pulmonary condition similar to that seen in coal miners, based on radiographic and histologic examinations in exposed individuals (Harding and Oliver 1949/Ex. 1-71). The fibrotic changes seen in graphite workers appear to be related to the silica content of the graphite; experimental animals that were administered graphite that did not contain silica did not develop fibrotic changes (Ray, King, and Harrison 1951/Ex. 1-46), while another study found that graphite containing only a small amount of silica produced fibrotic changes in exposed animals (Ottowicz and Paradowski 1961/Ex. 1-190). Radiologic changes were also observed among graphite mine and production workers exposed to graphite containing from 3.6 to 10 percent silica (Pendergrass, Vorwald, Mishkin et al. 1967/Ex. 1-77). OSHA received no comments on this substance except for those from NIOSH.

In the final rule, OSHA is revising its former limit of 15 mppcf to a limit of 2.5 mg/m³ for the respirable fraction of graphite containing less than 1 percent quartz; this change represents a change only in the units used to express or measure the limit, not a change in the value of the limit. OSHA is revising its limit to simplify the monitoring of employee exposures, because the use of impingers and microscopic analyses are not required to measure exposures that are expressed in mg/m³ rather than in mppcf.