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Tantalum (metal and oxide dust, as Ta)
May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)
CAS number: 7440–25–7 (Metal)
NIOSH REL: 5 mg/m3 TWA, 10 mg/m3 STEL
Current OSHA PEL: 5 mg/m3 TWA
1989 OSHA PEL: Same as current PEL
1993-1994 ACGIH TLV: 5 mg/m3 TWA
Description of substance: Varies
Original (SCP) IDLH*: No Evidence [*Note: “Effective” IDLH = 2,500 mg Ta/m3 — see discussion below.]
Basis for original (SCP) IDLH: Because no evidence of an IDLH is shown in the available toxicological data, respirators have been assigned on the basis of the assigned protection factor afforded by each device up to 500 ´ the OSHA PEL of 5 mg Ta/m3 (i.e., 2,500 mg Ta/m3); only the “most protective” respirators are permitted for use in concentrations exceeding 2,500 mg Ta/m3.
Short-term exposure guidelines: None developed
ACUTE TOXICITY DATA:
Lethal dose data:
| Species | Reference | Route | LD50(mg/kg) | LDLo(mg/kg) | Adjusted LD | Derived value |
|---|---|---|---|---|---|---|
| Ta2O5Rat | Coulston &Korte 1975 | oral | 8,000 | —– | 45,862 mg Ta/m3 | 4,586 mg Ta/m3 |
Human data: None relevant for use in determining the revised IDLH.
| Revised IDLH: 2,500 mg Ta/m3Basis for revised IDLH: No inhalation toxicity data are available on which to base an IDLH for tantalum metal and oxide dust. Therefore, based on acute oral toxicity data in animals [Coulston and Korte 1975], a value of about 4,500 mg Ta/m3 would have been appropriate. However, the revised IDLH for tantalum metal and oxide dust is 2,500 mg Ta/m3 based on being 500 times the NIOSH REL and OSHA PEL of 5 mg Ta/m3 (500 is an assigned protection factor for respirators and was used arbitrarily during the Standards Completion Program for deciding when the “most protective” respirators should be used for particulates). |
REFERENCE:
1. Coulston F, Korte F, eds. [1975]. Heavy metal toxicity, safety and hormology. In: Environmental Quality & Safety, Supplement 1. New York, NY: Georg Thieme Publishers, pp. 1-120.