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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


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.


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.