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

CAS number: 78–59–1

NIOSH REL: 4 ppm (23 mg/m3) TWA

Current OSHA PEL: 25 ppm (140 mg/m3) TWA

1989 OSHA PEL: 4 ppm (23 mg/m3) TWA

1993-1994 ACGIH TLV: 5 ppm (28 mg/m3) CEILING

Description of substance: Colorless to white liquid with a peppermint-like odor.

LEL:. . 0.8% (10% LEL, 800 ppm)

Original (SCP) IDLH: 800 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the UCC [1971] report that exposure of animals for 1 hour to 880 ppm caused serious organ damage; only 1 of 6 animals died from an 8-hour exposure to air saturated with isophorone (approximately 525 ppm at 77°F).

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF) Derived value
Rat ATSDR 1989 —– 885 6 hr 2,036 ppm (2.3) 204 ppm
G. pig Marhold 1986 4,600 —– 8 hr 11,500 ppm (2.5) 1,150 ppm
Rat Smyth & Seaton 1940 —– 1,840 4 hr 3,680 ppm (2.0) 368 ppm
Mammal UCC 1971 LC17: 525 —– 8 hr 1,316 ppm (2.5) 132 ppm

Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived value
Rat Smyth et al. 1970 oral 2,330 —– 2,841 ppm 284 ppm
Mouse Smyth et al. 1970 oral 2,690 —– 3,280 ppm 328 ppm

Other animal data: RD50 (mouse), 27.8 ppm [DeCeaurriz et al. 1981]. It has been reported that exposure of animals for 1 hour to 880 ppm caused serious organ damage [UCC 1971].

Human data: A few of the 11 or 12 volunteers exposed for a few minutes to 200 or 400 ppm complained of nausea, headache, dizziness, faintness, inebriation, and a feeling of suffocation [Smyth and Seaton 1940].

Revised IDLH: 200 ppmBasis for revised IDLH: The revised IDLH for isophorone is 200 ppm based on acute inhalation toxicity data in humans [Smyth and Seaton 1940] and animals [ATSDR 1989].


1. ATSDR [1989]. Toxicological profile for isophorone. Atlanta, GA: Agency for Toxic Substances and Disease Registry, ATSDR/TP-89/15.

2. DeCeaurriz JC, Micillino JC, Bonnet P, Guenier JP [1981]. Sensory irritation caused by various industrial airborne chemicals. Toxicol Lett 9:137-147.

3. Marhold J [1986]. Prehled Prumyslove Toxikologie, Organicke Latky. Prague, Czechoslovakia: Avicenum, p. 290 (in Czechoslovakian).

4. Smyth HF Jr, Seaton J [1940]. Acute response of guinea pigs and rats to inhalation of the vapors of isophorone. J Ind Hyg Toxicol 22(10):477-483.

5. Smyth HF Jr, Weil CS, West JS, Carpenter CP [1970]. An exploration of joint toxic action. II. Equitoxic versus equivolume mixtures. Toxicol Appl Pharmacol 17:498-503.

6. UCC [1971]. Toxicology studies: isophorone. New York, NY: Union Carbide Corporation.