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May 1994

Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)


CAS number: 123–91–1

NIOSH REL: 1 ppm (3.6 mg/m3) 30-minute CEILING; NIOSH considers dioxane to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 100 ppm (360 mg/m3) TWA [skin]

1989 OSHA PEL: 25 ppm (90 mg/m3) TWA [skin]

1993-1994 ACGIH TLV: 25 ppm (90 mg/m3) TWA [skin]

Description of Substance: Colorless liquid or solid (below 53 F) with a mild, ether-like odor.

LEL:. . 2.0% (10% LEL, 2,000 ppm)

Original (SCP) IDLH: 2,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the acute inhalation toxicity data cited by AIHA [1960] in which a lethal concentration of 1,000 to 3,000 ppm for 3 hours is reported for guinea pigs, and on the lethal concentration of 2,085 ppm (8 hours) for mice [Klimmer 1937] reported by Spector [1956]. ACGIH [1971] reported that guinea pigs could tolerate 2,000 ppm for several hours without serious symptoms [Yant et al. 1930]. Therefore, exposure of workers to 2,000 ppm for 30 minutes probably would not impede escape or cause any irreversible health effects.

Short-term exposure guidelines: None developed


Lethal concentration data:







Adjusted 0.5-hr




G. pig





AIHA 1960

Izmerov et al. 1982

Klimmer 1937

Klimmer 1937

Kosm Biol Aviak Med 1977











3 hr

2 hr

7 hr

8 hr

2 hr

1,800-5,400 ppm (1.8)

16,174 ppm (1.6)

28,853 ppm (2.4)

5,213 ppm (2.5)

20,109 ppm (1.6)

180-540 ppm

1,617 ppm

2,885 ppm

521 ppm

2,011 ppm

Other animal data: Guinea pigs can tolerate 2,000 ppm by inhalation for several hours without serious symptoms; higher concentrations produced eye, nose, and lung irritation [Yant et al. 1930].

Human data: None relevant for use in determining the revised IDLH.


Revised IDLH: 500 ppm

Basis for revised IDLH: The revised IDLH for dioxane is 500 ppm based on acute inhalation toxicity data in animals [AIHA 1960; Klimmer 1937]. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for dioxane at concentrations above 1 ppm.]


1. ACGIH [1971]. Dioxane. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 94.

2. AIHA [1960]. Dioxane. In: Hygienic guide series. Am Ind Hyg Assoc J 21:533-534.

3. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 63.

4. Klimmer O [1937]. Dissertation: Beitrag zur toxikologischen wirkung technischer losungsmittel (in German). Germany: Pharmakologischen Institut der Universitat Wurzburg.

5. Kosm Biol Aviak Med [1977]; 11(6):53-57 (in Russian).

6. Spector WS, ed. [1956]. Handbook of toxicology. Vol. I. Acute toxicities of solids, liquids and gases to laboratory animals. Philadelphia, PA: W.B. Saunders Co., pp. 334-335.

7. Yant WP, Schrenk HH, Patty FA, Waite CP [1930]. Acute response of guinea pigs to vapors of some new commercial organic compounds. VI. Dioxan. Public Health Rep 45(2):2023-2032.

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