GRAPHITE, SYNTHETIC

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 formerly had no specific limit for synthetic graphite, although it was covered under the Agency’s generic total particulate limit. OSHA’s proposed 8-hour TWA PEL for synthetic graphite was 10 mg/m³ (total particulate), and this limit is established by the final rule; the 5-mg/m³ limit for the respirable fraction is retained. The ACGIH also has a TLV-TWA limit of 10 mg/m³ for graphite as total dust. Synthetic graphite is a crystalline form of carbon made from the high-temperature treatment of coal or petroleum products; it has the same properties as natural graphite.

Meiklejohn reported in 1958 that synthetic graphite injected intraperitoneally in mice produced effects characteristic of those of the inert dusts (Meiklejohn 1958, as cited in ACGIH 1986/Ex. 1-3, p. 291).

In humans, exposure to natural graphite has long been associated with the development of pneumoconiosis (Koopman 1924/Ex. 1-131; Ruttner, Bovet, and Aufdermauer 1952/Ex. 1-661; Pendergrass, Vorwald, Mishkin et al. 1967/Ex. 1-77). Lister (1961/Ex. 1-422) and Lister and Wimborne (1972/Ex. 1-423) reported fibrotic changes in the lungs of a worker who had been engaged for 17 years in the production and milling of synthetic graphite. Other reports of lung injury caused by exposure to graphite have not distinguished between the form of the graphite (i.e., natural or synthetic) causing the injury; in addition, exposures to impurities, such as quartz silica, were involved in many of the reported cases (ACGIH 1986/Ex. 1-3, p. 291). NIOSH (Ex. 8-47) does not believe that it is appropriate to distinguish between the natural and synthetic forms of graphite and notes that the Lister and Wimborne (1972/Ex. 1-423) study described above suggests that synthetic graphite dust exposure “is capable of producing pneumo-coniosis.” NIOSH believes that a 2-mg/m³ 8-hour TWA PEL is appropriate for synthetic graphite because this is the limit set for coal dust (respirable) to protect against pneumoconiosis (Ex. 8-47). OSHA received no responses other than NIOSH’s to a question raised in the proposal about synthetic graphite-related occupational disease. OSHA intends to continue to evaluate any new evidence on synthetic graphite exposures, such as the study on carbon/graphite fibers submitted by NIOSH (Zumwalde and Harmison 1980, as cited in Ex. 8-47), to determine whether further action to reduce the PEL is warranted in the future.

At present, however, OSHA is reducing the 8-hour TWA total particulate limit for synthetic graphite from 15 mg/m³ to 10 mg/m³ and retaining the 5-mg/m³ limit for the respirable fraction to protect against the significant health risks associated with graphite exposures in the workplace. OSHA concludes that these limits will substantially reduce the risks of granite-induced respiratory disease, which constitutes a material impairment of health.