DECABORANE

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: 17702-41-9; Chemical Formula: B₁₀H₁₄

OSHA’s former limit for decaborane was 0.05 ppm TWA, with a skin notation. The ACGIH has a TLV-TWA of 0.05 ppm and a TLV-STEL of 0.15 ppm, also with a skin notation. The proposal retained the 8-hour TWA of 0.05 ppm and added a 0.15-ppm STEL, with a skin notation, and the final rule establishes these limits. NIOSH (Ex. 8-47, Table N1) concurs that these limits are appropriate. Decaborane forms colorless crystals that are stable at ordinary temperatures and have a pungent odor.

The acute toxicity of decaborane is extremely high for small laboratory animals. The 40-hour LC(50)s for rats and mice are 46 and 12 ppm, respectively (Schechter 1958/ Ex. 1-363). Dermal LD(50)s for rabbits and rats are 71 and 740 mg/kg, respectively (Svirbely 1954a/Ex. 1-385). Acute exposures to decaborane cause loss of coordination, convulsions, weakness, tremors, and hyperexcitability. Decaborane’s primary effects are on the kidneys and liver. Studies of repeated exposures to this substance suggest that the toxicity of decaborane is intermediate between that of pentaborane and diborane. The ability of decaborane to penetrate the skin is particularly notable, as is its toxicity to the central nervous system in some species, e.g., rats and rabbits (Svirbely 1954a/Ex. 1-385, 1954b/Ex. 1-530, and 1955/Ex. 1-386). Monkeys showed decreased ability for certain operant behaviors when injected with doses of 3 to 6 mg/kg decaborane (Reynolds et al. 1964, as cited in ACGIH 1986/Ex. 1-3, p. 169). Central nervous system toxicity has been observed in humans exposed occupationally (Krackow 1953/Ex. 1-344). No comments other than NIOSH’s were received on the health effects of decaborane.

OSHA is retaining its 8-hour TWA PEL of 0.05 ppm TWA and skin notation, and adding a 15-minute STEL of 0.15 ppm for decaborane. The Agency concludes that these limits will provide protection against the significant risks of material health impairment in the form of neuropathy and kidney and liver damage possible in the absence of a short-term limit for decaborane.