Rhodium (metal fume and insoluble compounds, as Rh)

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

CAS number: 7440–16–6 (Metal)

NIOSH REL: 0.1 mg/m3 TWA

Current OSHA PEL: 0.1 mg/m3 TWA

OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 1 mg/m3 TWA

Description of substance: Varies

Original (SCP) IDLH*: No Evidence [*Note: “Effective” IDLH = 200 mg Rh/m3 — see discussion below.]

Basis for original (SCP) IDLH: Because no evidence of an IDLH for rhodium (metal fume and insoluble compounds) is available, respirators have been selected on the basis of the assigned protection factor afforded by each device up to 2,000 ´ the OSHA PEL of 0.1 mg Rh/m3 (i.e., 200 mg Rh/m3); only the “most protective” respirators are permitted for use in concentrations exceeding 200 mg Rh/m3.

Short-term exposure guidelines: None developed


Lethal dose data:

Species Reference Route LD50




Adjusted LD Derived value
Rat RhCl3 Johnson 1981 oral >500 ----- >1,778 mg Rh/m3 >179 mg Rh/m3
Rat RhCl3 Veselov 1977 oral 1,302 ----- 4,638 mg Rh/m3 464 mg Rh/m3
Rat Na3RhCl6 Johnson 1981 oral >500 ----- >936 mg Rh/m3 >94 mg Rh/m3
Rat [Rh(NH3)5Cl ] Cl2 Johnson 1981 oral >500 ----- >1,223 mg Rh/m3 >122 mg Rh/m3

Human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 100 mg Rh/m3

Basis for revised IDLH: No inhalation toxicity data are available on which to base an IDLH for insoluble rhodium compounds. Therefore, the revised IDLH for insoluble rhodium compounds is 100 mg Rh/m3 based on acute oral toxicity data in animals [Johnson 1981; Veselov 1977]. This may be a conservative value due to the lack of relevant acute toxicity data for workers.


1. Johnson, Matthey and Co., Ltd. [1981]. Biological effects of rhodium metal and compounds. Material Safety Report N5 81-48. [From ACGIH [1985]. Rhodium and compounds. In: Documentation of the threshold limit values and biological exposure indices. 5th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 512.]

2. Veselov VG [1977]. Comparative toxicity of platinoids in conditions of acute oral intoxication of animals. Gig Tr Prof Zabol 21(7):55-57 (in Russian).

Page last reviewed: December 4, 2014