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

Oxalic acid

CAS number: 144–62–7

NIOSH REL: 1 mg/m3 TWA, 2 mg/m3 STEL

Current OSHA PEL: 1 mg/m3 TWA

1989 OSHA PEL: 1 mg/m3 TWA, 2 mg/m3 STEL

1993-1994 ACGIH TLV: 1 mg/m3 TWA, 2 mg/m3 STEL

Description of substance: Colorless, odorless powder or granular solid.

LEL: . Unknown

Original (SCP) IDLH: 500 mg/m3

Basis for original (SCP) IDLH: The chosen IDLH has been calculated from the total oral lethal dose for man of 5 grams [ACGIH 1971].

Short-term exposure guidelines: None developed


Lethal dose data:






Adjusted LDDerived value
DogFlury & Zernik 1935 oral-----1,0007,000 mg/m3700 mg/m3
RatShtabsky & Shatinskaya 1985 ?-----1,4009,800 mg/m3980 mg/m3
RatVernot et al. 1977 oral-----7,50052,500 mg/m3 5,250 mg/m3

Human data: It has been reported that the lethal oral dose is 15 to 30 grams [Webster 1930]. [Note: An oral dose of 15 to 30 grams is equivalent to a 30-minute exposure to 10,000 to 20,000 mg/m3 assuming a 50 liter per minute breathing rate and 100% absorption.]


Revised IDLH: 500 mg/m3 [Unchanged]

Basis for revised IDLH: No inhalation toxicity data are available on which to base an IDLH for oxalic acid. Therefore, based on acute oral toxicity data in humans [Webster 1930] and animals [Flury and Zernik 1935], the original IDLH for oxalic acid (500 mg/m3) is not being revised at this time.


1. ACGIH [1971]. Oxalic acid. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 193.

2. Flury F, Zernik F [1935]. Zusammenstellung der toxischen und letalen dosen für die gebräuchlichsten gifte und versuchstiere. Abder Hand Biol Arbeitsmethod 4:1289-1422 (in German).

3. Shtabsky BM, Shatinskaya EG [1985]. Evaluation of cumulative properties of toxic chemicals from the subchronic experiment. Gig Sanit 50(3):57-60 (in Russian).

4. Vernot EH, MacEwen JD, Haun CC, Kinkead FR [1977]. Acute toxicity and skin corrosion data for some organic and inorganic compounds and aqueous solutions. Toxicol Appl Pharmacol 42:417-423.

5. Webster RW [1930]. Legal medicine and toxicology. Philadelphia, PA: W.B. Saunders.

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