BISMUTH TELLURIDE

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: 1304-82-1; Chemical Formula: Bi₂Te₃

OSHA had no former limit for undoped bismuth telluride, although OSHA’s generic total particulate limit of 15 mg/m³ formerly applied. The ACGIH has a total-dust TLV-TWA of 10 mg/m 3 for the undoped form of this substance. The proposed PELs for bismuth telluride in the undoped form were 10 mg/m³ (total particulate) and 5 mg/m³ (respirable particulate); however, in the final rule, OSHA is retaining the total particulate limit of 15 mg/m³ for this substance, as well as the 5-mg/m³ respirable-fraction limit. Bismuth telluride appears as gray, hexagonal platelets; it is also available as ingots or single crystals.

An eleven-month inhalation study of dogs, rabbits, and rats exposed to pure undoped bismuth telluride dust at 15 mg/m³ showed the pulmonary responses typical of exposures to inert dusts (Wagner, Madden, Zimber, and Stokinger 1974, as cited in ACGIH 1986/Ex. 1-3, p. 59). NIOSH has not evaluated the evidence for undoped bismuth telluride in depth (Ex. 8-47, Table N4). No other comments on this substance were submitted.

OSHA is retaining its permissible exposure limits of 15 mg/m³ TWA, as total particulate, and 5 mg/m³, as the respirable fraction, for pure undoped bismuth telluride. The Agency concludes that these limits protect workers from the significant risks associated with workplace exposures to bismuth telluride.