(1,4-Dioxane; p-dioxane; diethylene ether; 1,4-diethylene dioxide)

CAS 123-91-1





Physical Properties

Colorless liquid

bp 101 °C, mp 12 °C

Miscible with water



Mild ether-like odor detectable at 0.8 to 172 ppm (mean = 12 ppm)

Vapor Density

3 (air = 1.0)


Vapor Pressure

40 mmHg at 25 °C


Flash Point

12 °C


Autoignition Temperature

180 °C


Toxicity Data

LD50 oral (mouse)

5700 mg/kg


LC50 inhal (rat)

13,000 ppm (46,800 mg/m3; 2 h)


LD50 skin (rabbit)

7600 mg/kg



100 ppm (360 mg/m3)—skin



25 ppm (90 mg/m3)—skin

Major Hazards

Highly flammable; forms sensitive peroxides on exposure to air that may explode on concentration by distillation or drying.


The acute toxicity of 1,4-dioxane is low. Exposure to 200 to 300 ppm causes irritation of the eyes, nose, and throat. Inhalation of higher concentrations can result in damage to the kidneys and liver. Symptoms of overexposure may include upper respiratory tract irritation, coughing, drowsiness, vertigo, headache, stomach pains, nausea, and vomiting. Prolonged or repeated contact may produce drying and cracking of the skin. Ingestion of this substance will result in the effects of exposure by inhalation. The odor of dioxane is not unpleasant, and its irritating effects may be transitory; consequently, it is not regarded as a substance with adequate warning properties.

Dioxane shows carcinogenic effects in animal studies and is listed by IARC in Group 2B ("possible human carcinogen"). It is not classified as a "select carcinogen" according to the criteria of the OSHA Laboratory Standard. Prolonged or repeated exposure to this substance may result in liver and kidney injury. Dioxane has not been shown to be a reproductive or developmental toxin in humans.

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