Chromium(II) compounds [as Cr(II)]

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

CAS number: Varies

NIOSH REL: 0.5 mg/m3 TWA

Current OSHA PEL: 0.5 mg/m3 TWA

1989 OSHA PEL: Same as current PEL

1993­1994 ACGIH TLV: 0.5 mg/m3 TWA

Description of Substance: Varies

Original (SCP) IDLH*: No Evidence [*Note: “Effective” IDLH = 250 mg Cr(II)/m3 — see discussion below.]

Basis for original (SCP) IDLH: ACGIH [1971] noted that early studies indicated trivalent chromium to be essentially nontoxic [Akatsuka and Fairhall 1934]. The available toxicological data show no evidence that an acute exposure to a high concentration of soluble chromous salts would 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; in the case of chromium(II) compounds, 500 × the OSHA PEL of 0.5 mg Cr(II)/m3 is 250 mg Cr(II)/m3.

Short­term exposure guidelines: None developed


Lethal dose data:







Adjusted LD

Derived value

Smyth et al. 1969




5,528 mg Cr(II)/m3

553 mg Cr(II)/m3

Human data: It has been reported that divalent chromium compounds (i.e., chromous salts) have a low order of toxicity and provide little industrial hazard [ACGIH 1971; Akatsuka and Fairhall 1934; Clayton and Clayton 1981].

Revised IDLH: 250 mg Cr(II)/m3

Basis for revised IDLH: The available toxicological data contain no evidence that an acute exposure to a high concentration of chromium(II) compounds would impede escape or cause any irreversible health effects within 30 minutes. However, the revised IDLH for chromium(II) compounds is 250 mg Cr(II)/m3 based on being 500 times the NIOSH REL of 0.5 mg Cr(II)/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).



1. ACGIH [1971]. Chromium (as Cr). In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 56.

2. Akatsuka K, Fairhall LT [1934]. The toxicology of chromium. J Ind Hyg 16:1­28

3. Clayton GD, Clayton FE, eds. [1981]. Patty’s industrial hygiene and toxicology. 3rd rev. ed. Vol. 2A. Toxicology. New York, NY: John Wiley & Sons, Inc., pp. 1593­1596.

4. Smyth HF Jr, Carpenter CP, Weil CS, Pozzani UC, Striegel JA, Nycum JS [1969]. Range­finding toxicity data: list VII. Am Ind Hyg Assoc J 30:470­476.

CDC home page.External CDC logoExternal

Page last reviewed: December 4, 2014