Rhodium (soluble compounds, as Rh)

May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: Varies

NIOSH REL: 0.001 mg/m3 TWA

Current OSHA PEL: 0.001 mg/m3 TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.01 mg/m3 TWA

Description of substance Varies

Original (SCP) IDLH*: No evidence [*Note: “Effective” IDLH = 2 mg Rh/m3 — see discussion below.]

Basis for original (SCP) IDLH: There is no indication from experimental data or industrial experience that the soluble compounds of rhodium produce toxic effects in man. Therefore, because no evidence of an IDLH exists, respirators have been selected on the basis of the assigned protection factor afforded by each device up to 2,000 ´ the OSHA PEL of 0.001 mg Rh/m3 (i.e., 2 mg Rh/m3); only the “most protective” respirators are permitted for use in concentrations exceeding 2 mg Rh/m3.

Short-term exposure guidelines: None developed


Animal or human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 2 mg Rh/m3

Basis for revised IDLH: The available toxicological data contain no evidence that an acute exposure to a high concentration of soluble rhodium compounds would impede escape or cause any irreversible health effects within 30 minutes. However, the revised IDLH for soluble rhodium compounds is 2 mg Rh/m3 based on being 2,000 times the NIOSH REL and OSHA PEL of 0.001 mg Rh/m3 (2,000 is an assigned protection factor for respirators and was used during the Standards Completion Program for deciding when the "most protective" respirators should be used for soluble rhodium compounds).

Page last reviewed: December 4, 2014