INDIUM AND COMPOUNDS

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: 7440-74-6; Chemical Formula: In

There was no former OSHA limit for indium and compounds; however, the proposed and final rule PEL is 0.1 mg/m³ as an 8-hour TWA. NIOSH (Ex. 8-47, Table N1) concurred with this limit. The ACGIH recommends that exposures to indium not exceed 0.1 mg/m³ over an 8-hour shift. Indium metal is silver-white, shiny, and ductile.

Although there is no direct human evidence of the effect of indium compounds, severe effects have been produced by indium exposures in experimental animals. Rats that inhaled the sesquioxide form of indium at airborne concentrations ranging from 24 to 97 mg/m³ daily for a total of 224 hours developed widespread alveolar edema; these histologic lesions did not change over a 12-week post-exposure period (Leach, Scott, Armstrong et al. 1961, as cited in ACGIH 1986/Ex. 1-3, p. 322). Exposure of animals to indium reduces alveolar clearance and may be associated with chronic respiratory insufficiency, recurrent acute pneumonitis, and death (Jones 1960, as cited in ACGIH 1986/Ex. 1-3, p. 322). NIOSH was the only commenter on this substance.

Because of the severity of indium-induced injury and the persistence of such injuries, OSHA concludes that, in the absence of any exposure limit, exposed employees are at significant risk of developing chronic lung function impairment. The Agency is establishing an 8-hour TWA limit of 0.1 mg/m³ for indium and compounds to substantially reduce this risk.