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Ethylene oxide

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

CAS number: 75–21–8

NIOSH REL: <0.1 ppm (<0.18 mg/m3) TWA, 5 ppm (9 mg/m3) CEILING, 10-minutes/day; NIOSH considers ethylene oxide to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 1 ppm TWA, 5 ppm 15-minute “EXCURSION”

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 1 ppm (1.8 mg/m3) TWA, A2

Description of Substance: Colorless gas or liquid (below 51 F) with an ether-like odor.

LEL:. . 3.0% (10% LEL, 3,000 ppm)

Original (SCP) IDLH: 800 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by AIHA [1958] that the estimated LC50 for a 4-hour exposure is approximately 800 to 1,500 ppm depending on the species [Jacobson et al. 1956]. In addition, Patty [1963] stated that for humans 500 ppm is probably safe for single exposures (no more than once per week) of 1-hour duration.

Existing short-term exposure guidelines: National Research Council [NRC 1986] Emergency Exposure Guidance Levels (EEGLs):

1-hour EEGL: 20 ppm

24-hour EEGL: 1 ppm


Lethal concentration data:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF) Derivedvalue


G. pig




Back et al. 1972Carpenter et al. 1949

Deichmann and Gerarde 1969

Izmerov et al. 1982

Jacobson et al. 1956

Jacobson et al. 1956

Jacobson et al. 1956













4 hr4 hr

4 hr

4 hr

4 hr

4 hr

4 hr

1,672 ppm (2.0)8,000 ppm (2.0)

1,600 ppm (2.0)

1,638 ppm (2.0)

2,920 ppm (2.0)

1,670 ppm (2.0)

1,920 ppm (2.0)

167 ppm800 ppm

160 ppm

164 ppm

292 ppm

167 ppm

192 ppm


Human data: Other than temporary, slight irritation, no after-effects were reported in 4 men after intentional exposure to 2,500 ppm for a brief period; definite nasal irritation was reported after 10 seconds of exposure to 12,500 ppm [Walker and Greeson 1932]. Exposures to concentrations above 2,000 ppm have resulted in headache, nausea, vomiting, dyspnea, hematological abnormalities, and respiratory irritation [NRC 1986]. Based on acute toxicity data in animals, it has been suggested that injury or death would be associated with exposure to 8,000 ppm for 10 minutes, 4,000 ppm for 30 minutes, or 2,000 ppm for 60 minutes; a 1-hour exposure to 500 ppm was considered as not likely to produce injury [Clayton and Clayton 1981].

Revised IDLH: 800 ppm [Unchanged]Basis for revised IDLH: Based on acute inhalation toxicity data in humans [Clayton and Clayton 1981; NRC 1986; Walker and Greeson 1932] the original IDLH for ethylene oxide (800 ppm) is not being revised at this time. [Note: NIOSH recommends as part of its carcinogen policy that the “most protective” respirators be worn for ethylene oxide at concentrations above 5 ppm. OSHA currently requires in 29 CFR 1919.1047 that workers be provided with and required to wear and use the “most protective” respirators in concentrations exceeding 2,000 ppm (2,000 × the PEL).]



1. AIHA [1958]. Ethylene oxide. In: Hygienic guide series. Am Ind Hyg Assoc J 19:528-529.

2. Back KC, Thomas AA, MacEwen JD [1972]. Reclassification of materials listed as transportation health hazards. Wright-Patterson Air Force Base, OH: 6570th Aerospace Medical Research Laboratory, Report No. TSA-20-72-3, pp. A-204 to A-205.

3. Carpenter CP, Smyth HF Jr, Pozzani UC [1949]. The assay of acute vapor toxicity, and the grading and interpretation of results on 96 chemical compounds. J Ind Hyg Toxicol 31:343-346.

4. Clayton GD, Clayton FE, eds. [1981]. Patty’s industrial hygiene and toxicology. 3rd rev. ed. Vol. 2A. Toxicology. New York, NY: John Wiley & Sons, Inc., pp. 2166-2186.

5. Deichmann WB, Gerarde HW [1969]. Ethylene oxide (epoxyethane; oxirane; dimethylene oxide). In: Toxicology of drugs and chemicals. New York, NY: Academic Press, Inc., pp. 258-259.

6. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 67.

7. Jacobson KH, Hackley EB, Feinsilver L [1956]. The toxicity of inhaled ethylene oxide and propylene oxide vapors. Acute and chronic toxicity of ethylene oxide and acute toxicity of propylene oxide. AMA Arch Ind Health 13(3):237-244.

8. NRC [1986]. Emergency and continuous exposure limits for selected airborne contaminants. Vol. 6. Benzene and ethylene oxide. Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology and Environmental Health Hazards, Commission on Life Sciences, National Research Council, pp. 35-71.

9. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1633.

10. Walker WJG, Greeson CE [1932]. The toxicity of ethylene oxide. J Hyg 32:409-416.