Magnesium oxide fume

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

CAS number: 1309–48–4

NIOSH REL: The 1989 OSHA PEL may not be protective to workers.

Current OSHA PEL: 15 mg/m3 (total dust) TWA

1989 OSHA PEL: 10 mg/m3 (total dust) TWA

1993-1994 ACGIH TLV: 10 mg/m3 (total dust) TWA

Description of substance: Finely divided white particulate dispersed in air.

LEL: . . Noncombustible Solid

Original (SCP) IDLH*: No Evidence [*Note: “Effective” IDLH = 7,500 mg/m3 — see discussion below.]

Basis for original (SCP) IDLH: The available toxicological data contain no evidence of an IDLH for magnesium oxide fume, because the symptoms of metal fume fever would not impede escape or cause 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 ´ 15 mg/m3 is 7,500 mg/m3).

Short-term exposure guidelines: None developed


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

Human data: Volunteers exposed to freshly generated fume at concentrations ranging from 410 to 580 mg/m3 experienced only slight (unspecified) reactions [Drinker et al. 1927].

Revised IDLH: 750 mg/m3

Basis for revised IDLH: The revised IDLH for magnesium oxide fume is 750 mg/m3 based on acute inhalation toxicity data in humans [Drinker et al. 1927].


1. Drinker P, Thomson RN, Finn JL [1927]. Metal fume fever. III. The effects of inhaling magnesium oxide fume. J Ind Hyg 9:187-192.

Page last reviewed: December 4, 2014