Iron oxide dust and fume (as Fe)

CAS number: 1309–37–1

NIOSH REL: 5 mg/m³ TWA

Current OSHA PEL: 10 mg/m³ TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 5 mg/m³ TWA (fume)

Description of substance: Reddish-brown solid.

LEL: . . Noncombustible Solids

Original (SCP) IDLH*: No Evidence [*Note: "Effective" IDLH = 5,000 mg Fe/m³ -- see discussion below.]

Basis for original (SCP) IDLH: The available toxicological data contain no evidence that an acute exposure to iron oxide fume would impede escape or produce any irreversible health effects within 30 minutes. For this draft technical standard, therefore, respirators have been selected on the basis of the assigned protection factor afforded by each device. However, for some particulate substances for which no evidence of an IDLH exists, the determination of allowable respiratory protection based on protection factors may result in the assignment of respirators for concentrations that are not likely to be encountered in the occupational environment. Therefore, for all such particulate substances it has been arbitrarily determined that only the "most protective" respirators are permitted for use in concentrations exceeding 500 ´ the OSHA PEL (500 ´ 10 mg Fe/m³ is 5,000 mg Fe/m³).

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA:

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

Revised IDLH: 2,500 mg Fe/m3 Basis for revised IDLH: The available toxicological data contain no evidence that an acute exposure to a high concentration of iron oxide dust and fume would impede escape or cause any irreversible health effects within 30 minutes. However, the revised IDLH for iron oxide dust and fume is 2,500 mg Fe/m3 based on being 500 times the NIOSH REL of 5 mg Fe/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).