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Formic acid

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

CAS number: 64–18–6

NIOSH REL: 5 ppm (9 mg/m3) TWA

Current OSHA PEL: 5 ppm (9 mg/m3) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 5 ppm (9.4 mg/m3) TWA, 10 ppm (19 mg/m3) STEL

Description of Substance: Colorless liquid with a pungent, penetrating odor.

LEL(90% solution): 18% (10% LEL (90% solution), 18,000 ppm)

Original (SCP) IDLH: 30 ppm

Basis for original (SCP) IDLH: Because no data on acute inhalation toxicity are available on which to base an IDLH for formic acid, the chosen IDLH is based on an analogy with formaldehyde, which has an IDLH of 30 ppm.

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF) Derivedvalue
RatMouse Gig Tr Prof Zabol 1963Gig Tr Prof Zabol 1963 7,8533,246 ———- 15 min15 min 6,204 ppm (0.79)2,564 ppm (0.79) 620 ppm256 ppm


Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived value


Gig Tr Prof Zabol 1963Gig Tr Prof Zabol 1963

von Oettingen 1959







4,031 ppm2,565 ppm

14,659 ppm

403 ppm256 ppm

1,466 ppm


Human data: Workers exposed to about 15 ppm have complained of nausea [Fahy and Elkins 1954].



1. Fahy JP, Elkins HB [1954]. Unpublished data. [From: ACGIH [1986]. Formic acid. In: Documentation of the threshold limit values and biological exposure indices. 5th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 279.].

2. Gig Tr Prof Zabol [1963]; 23(12):49 (in Russian).

3. von Oettingen WF [1959]. The aliphatic acids and their esters toxicity and potential dangers. AMA Arch Ind Health 20:517-531.