PHOSPHORUS PENTASULFIDE

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: 1314-80-3; Chemical Formula: P₂S₅

OSHA formerly had a limit of 1 mg/m³ as an 8-hour TWA for phosphorus pentasulfide. The ACGIH also has a limit of 1 mg/m³ TWA but adds a 15-minute STEL of 3 mg/m³. The proposal retained the 8-hour TWA PEL of 1 mg/m³ and added a STEL of 3 mg/m³; NIOSH (Ex. 8-47, Table N1) concurs with these limits. The final rule retains the 8-hour TWA PEL of 1 mg/m³ for phosphorus pentasulfide and adds a STEL of 3 mg/m³. Phosphorus pentasulfide is a greenish-yellow crystalline mass with an odor like that of rotten eggs.

The primary hazard associated with exposure to phosphorus pentasulfide is respiratory irritation (Smyth 1956/Ex. 1-759). In the presence of moisture, phosphorus pentasulfide is rapidly hydrolyzed to phosphoric acid and hydrogen sulfide. The ACGIH (1986/Ex. 1-3, p. 485) considers phosphorus pentasulfide to be as toxic as phosphoric acid. Only NIOSH commented on this substance.

In the final rule, OSHA is retaining the 8-hour TWA PEL of 1 mg/m³ and adding a 15-minute STEL of 3 mg/m³ for phosphorus pentasulfide. The Agency concludes that both of these limits are necessary to reduce the significant risk of respiratory irritation, a material health impairment that is associated with exposure to this substance at the higher concentrations permitted in the past by the TWA alone.