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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




Time Adjusted 0.5-hr


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




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 ppm

Basis 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.