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2D Structure
Also known as: Oxirane, Epoxyethane, 75-21-8, 1,2-epoxyethane, Oxacyclopropane, Dihydrooxirene
Molecular Formula
C2H4O
Molecular Weight
44.05  g/mol
InChI Key
IAYPIBMASNFSPL-UHFFFAOYSA-N
FDA UNII
JJH7GNN18P

A colorless and flammable gas at room temperature and pressure. Ethylene oxide is a bactericidal, fungicidal, and sporicidal disinfectant. It is effective against most micro-organisms, including viruses. It is used as a fumigant for foodstuffs and textiles and as an agent for the gaseous sterilization of heat-labile pharmaceutical and surgical materials. (From Reynolds, Martindale The Extra Pharmacopoeia, 30th ed, p794)
1 2D Structure

2D Structure

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
oxirane
2.1.2 InChI
InChI=1S/C2H4O/c1-2-3-1/h1-2H2
2.1.3 InChI Key
IAYPIBMASNFSPL-UHFFFAOYSA-N
2.1.4 Canonical SMILES
C1CO1
2.2 Other Identifiers
2.2.1 UNII
JJH7GNN18P
2.3 Synonyms
2.3.1 MeSH Synonyms

1. Oxide, Ethylene

2. Oxirane

2.3.2 Depositor-Supplied Synonyms

1. Oxirane

2. Epoxyethane

3. 75-21-8

4. 1,2-epoxyethane

5. Oxacyclopropane

6. Dihydrooxirene

7. Oxidoethane

8. Oxyfume

9. Ethene Oxide

10. Dimethylene Oxide

11. Amprolene

12. Anprolene

13. Anproline

14. Aethylenoxid

15. 1,2-epoxyaethan

16. Merpol

17. Oxiran

18. Oxyfume 12

19. T-gas

20. Oxirene, Dihydro-

21. Fema No. 2433

22. Ethyleenoxide

23. Oxiraan

24. Etylenu Tlenek

25. Qazi-ketcham

26. Oxyde D'ethylene

27. Rcra Waste Number U115

28. Eto

29. Nci-c50088

30. Ent-26263

31. Un 1040

32. Chebi:27561

33. Jjh7gnn18p

34. E.o.

35. Epoxide Or Oxirane

36. Oxiraan [dutch]

37. Aethylenoxid [german]

38. Caswell No. 443

39. Ethyleenoxide [dutch]

40. Ethyleneoxide

41. Ethylenoxide

42. Ethox

43. Etylenu Tlenek [polish]

44. 1,2-epoxyaethan [german]

45. Ccris 297

46. Etilene (ossido Di)

47. Hsdb 170

48. Ethylene (oxyde D') [french]

49. Etilene (ossido Di) [italian]

50. Alpha,beta-oxidoethane

51. Ethylene (oxyde D')

52. Einecs 200-849-9

53. Unii-jjh7gnn18p

54. Un1040

55. Rcra Waste No. U115

56. Epa Pesticide Chemical Code 042301

57. Ethyleneoxy

58. Monooxirane

59. Ethylene-oxide

60. Epoxy Ethane

61. Ai3-26263

62. Epitope Id:116215

63. Ec 200-849-9

64. .alpha.,.beta.-oxidoethane

65. Ciba-geigy 9138

66. Ethylene Oxide [mi]

67. 11104-97-5

68. Ethylene Oxide [fhfi]

69. Ethylene Oxide [hsdb]

70. Ethylene Oxide [iarc]

71. Ethylene Oxide, >=99.5%

72. Ethylene Oxide, >=99.9%

73. Ethylene Oxide [mart.]

74. Chembl1743219

75. Dtxsid0020600

76. Ethylene Oxide (30% Or Less), Propylene Oxide Mixture

77. Ethylene Oxide [who-dd]

78. Ethylene Oxide, Purum, >=99.8%

79. C0527

80. Mfcd00014482

81. Sterilizing Gas Ethylene Oxide 100%

82. Akos009031564

83. E0647

84. E0689

85. E0690

86. E0692

87. E0693

88. Ethylene Oxide 1000 Microg/ml In Triacetin

89. Ethylene Oxide Solution, 2.5-3.3 M In Thf

90. C06548

91. D03474

92. Q407473

93. Ethylene Oxide Solution, Certified Reference Material, 50 Mg/ml In Methanol

94. Ethylene Oxide Solution, 50 Mg/ml In Methylene Chloride, Analytical Standard

95. Ethylene Oxide Solution, Certified Reference Material, 500 Mug/ml In Dmso, Ampule Of 1 Ml

96. Ethylene Oxide Solution, Certified Reference Material, 2000 Mug/ml In Dichloromethane, Ampule Of 1 Ml

97. Ethylene Oxide, Or Ethlene Oxide With Nitrogen Up To A Total Pressure Of 1mpa (10 Bar) At 50 Degrees C

98. Ethylene Oxide, Or Ethlene Oxide With Nitrogen Up To A Total Pressure Of 1mpa (10 Bar) At 50 Degrees C [un1040] [poison Gas]

2.4 Create Date
2004-09-16
3 Chemical and Physical Properties
Molecular Weight 44.05 g/mol
Molecular Formula C2H4O
XLogP3-0.1
Hydrogen Bond Donor Count0
Hydrogen Bond Acceptor Count1
Rotatable Bond Count0
Exact Mass44.026214747 g/mol
Monoisotopic Mass44.026214747 g/mol
Topological Polar Surface Area12.5 Ų
Heavy Atom Count3
Formal Charge0
Complexity10.3
Isotope Atom Count0
Defined Atom Stereocenter Count0
Undefined Atom Stereocenter Count0
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Pharmacology and Biochemistry
4.1 MeSH Pharmacological Classification

Disinfectants

Substances used on inanimate objects that destroy harmful microorganisms or inhibit their activity. Disinfectants are classed as complete, destroying SPORES as well as vegetative forms of microorganisms, or incomplete, destroying only vegetative forms of the organisms. They are distinguished from ANTISEPTICS, which are local anti-infective agents used on humans and other animals. (From Hawley's Condensed Chemical Dictionary, 11th ed) (See all compounds classified as Disinfectants.)


4.2 Absorption, Distribution and Excretion

The study reported here examined the dosimetry of ethylene oxide (EO) in male B6C3F1 mice by direct determination of blood EO concentrations. Steady-state blood EO concentrations were measured during a single 4-hr nose-only inhalation exposure (0, 50, 100, 200, 300, or 400 ppm EO). In addition, glutathione (GSH) concentrations were measured in liver, lung, kidney, and testis to assess the role of the GSH depletion in the saturable metabolism previously observed in mice. Blood EO concentrations were found to increase linearly with exposure concentration up to 200 ppm. Markedly sublinear blood dosimetry was observed at exposure concentrations exceeding 200 ppm. An EO exposure concentration-dependent reduction in tissue GSH levels was observed, with both liver and lung GSH levels significantly depressed at EO exposure concentrations of 100 ppm or greater. /The/ results also indicate that depletion of GSH is likely responsible for nonlinear dosimetry of EO in mice and that GSH depletion corresponds with reports of dose-rate effects in mice exposed to EO.

PMID:9473528 Brown CD et al; Toxicol Appl Pharmacol 148 (2): 215-21 (1998)


... The objectives of this study were to examine the relationship between cigarette smoking and hemoglobin adducts derived from ... EO and to investigate whether null genotypes for glutathione transferase (GSTM1 and GSTT1) alter the internal dose of these agents. The hemoglobin adduct ... N-(2-hydroxyethyl)valine (HEVal), which is formed from EO, and GST genotypes were determined in blood samples obtained from 16 nonsmokers and 32 smokers (one to two packs/day). Smoking information was obtained by questionnaire, and plasma cotinine levels were determined by immunoassay. Glutathione transferase null genotypes (GSTM1 and GSTT1) were determined by PCR. ... HEVal levels increased with increased cigarette smoking dose (both self-reported and cotinine-based). ... HEVal levels were also correlated. ... GSTM1 null genotypes had no significant impact on HEVal. However, HEVal levels were significantly elevated in GSTT1-null individuals when normalized to smoking status or cotinine levels. ... The lack of a functional GSTT1 is estimated to increase the internal dose of EO derived from cigarette smoke by 50-70%.

PMID:10919741 Fennell TR et al; Cancer Epidemiol Biomarkers Prev 9 (7): 705-12 (2000)


AFTER EXPOSURE OF MICE TO MIXT OF 1,2-(3)H-ETHYLENE OXIDE VAPOR IN AIR FOR 75 MIN, 90-95% OF RADIOACTIVITY WAS ELIMINATED IN 24 HR. HIGHEST CONCN OF RESIDUAL RADIOACTIVITY WERE FOUND IN PROTEIN FRACTIONS OF SPLEEN; SMALLER AMT OCCURRED IN LIVER, KIDNEY, LUNG & TESTIS.

IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: https://monographs.iarc.fr/ENG/Classification/index.php, p. V11 162 (1976)


Iv injection of (14)C-labeled ethylene oxide indicated that (14)C concn in the testicle, epididymis and other organs were higher than those in the blood when measured 20 min to 4 hr after exposure. Radioactivity was still present in the epididymis 24 hr after exposure had ended.

Appelgren LE et al; Europ Soc Toxicol 18: 315 (1977)


For more Absorption, Distribution and Excretion (Complete) data for ETHYLENE OXIDE (11 total), please visit the HSDB record page.


4.3 Metabolism/Metabolites

Ethylene oxide reacts with glutathione to form cysteine derivatives, forms ethylene glycol by epoxide hydrolase with subsequent metabolism of the glycol, and reacts with chloride to form 2-chloroethanol. The relative importance of these pathways is undefined. Ethylene glycol glutathione conjugates are metabolites of ethylene oxide. ...

Dart, R.C. (ed). Medical Toxicology. Third Edition, Lippincott Williams & Wilkins. Philadelphia, PA. 2004., p. 1244


In adult male Sprague-Dawley rats, male Swiss CD-1 mice, and male rabbits, 20 or 60 mg/kg ethylene oxide as a solution in distilled water was injected into the caudal vein in rats and mice or in the marginal vein in rabbits. Some animals were exposed to 200 ppm ethylene oxide in inhalation chambers. The animals were housed in metabolism cages, and urine samples were collected at 0-6 hr and 6-24 hr. The urine samples were analyzed for 2-hydroxyethylmercapturic acid, N-acetyl-S-carboxy-methyl-L cysteine, S-(2-hydroxyethyl)-L-cysteine, S-carboxymethyl-L-cysteine, and ethylene glycol. Species-related differences in the metabolic disposition of ethylene oxide were observed. Excretion product patterns did not differ significantly between injected doses. Rats (n= 5) eliminated 37% of ethylene oxide as 2-hydroxyethylmercapturic acid (31%) and ethylene glycol (6%); mice (n= 10) converted 19.3% of the ethylene oxide to 2-hydroxyethylmercapturic acid (8.3%), S-2-hydroxyethyl-L-cysteine (5.8%), S-carboxymethyl-L-cysteine (1.9%), and ethylene glycol (3.3%). The rabbits (n= 3) excreted only 2% of the ethylene oxide, primarily as ethylene glycol. In rats, larger amounts of 2-hydroxyethylmercapturic acid were excreted in the 6-24 hr period, and larger amounts of ethylene glycol were excreted in the 0-6 hr period. In mice, equal amounts of 3-hydroxyethylmercapturic acid were excreted in the two collection periods and larger amounts of ethylene glycol were excreted in the 6-24 hr period. No urine was voided by the rabbits in the 0-6 hr period. No qualitative differences in urinary metabolite excretion of ethylene oxide were observed relative to the method of exposure.

PMID:3692004 Tardif R et al; Fundam Appl Toxicol 9 (3): 448-53 (1987)


In the presence of water and chloride, ethylene oxide is hydrolyzed to 2-chloroethanol and ethylene glycol. The glycol is further metabolized to oxalate, formic acid and CO2.

European Chemicals Bureau; IUCLID Dataset, Ethylene Oxide (CAS # 75-21-8) p. 155 (2000 CD-ROM edition). Available from, as of July 9, 2008: https://esis.jrc.ec.europa.eu/


Within 24 hours following iv treatment 35% of the administered doses ranging from 1 to 10 mg/kg to the rat were excreted as 2-hydroxyethyl-mercapturic acid (2-HEMA) in the urine. After inhalation exposure to different ethylene oxide concentrations, the 2-HEMA levels determined in 24 hr-urine were linearly related to ethylene oxide exposure levels.

European Chemicals Bureau; IUCLID Dataset, Ethylene Oxide (CAS # 75-21-8) p. 155 (2000 CD-ROM edition). Available from, as of July 9, 2008: https://esis.jrc.ec.europa.eu/


In animals and humans, there are two routes of ethylene oxide catabolism, both of which are considered to be detoxification pathways. The first involves hydrolysis to ethylene glycol, with subsequent conversion to oxalic acid, formic acid, and carbon dioxide. The second involves conjugation with glutathione, with subsequent metabolic steps yielding S-(2-hydroxyethyl)cysteine (S-(2-carboxymethyl)cysteine) and N-acetylated derivatives (ie, N-acetyl-S-(2-hydroxyethyl)cysteine (and N-acetyl-S-(2-carboxymethyl)cysteine)) ... . The route involving conjugation with glutathione appears to predominate in rats and mice; in larger species (rabbits, dogs), the conversion of ethylene oxide is primarily via hydrolysis through ethylene glycol ... . Ethylene oxide may also be formed from the metabolism of ethylene ... . A physiologically based pharmacokinetic (PBPK) model for the dosimetry of inhaled ethylene oxide was first developed for rats and included binding of ethylene oxide to hemoglobin and DNA in addition to tissue distribution, metabolic pathways (ie, hydrolysis by epoxide hydrolase and conjugation by glutathione-S-transferase), and depletion of hepatic and extra-hepatic glutathione ... . The model was then refined and extended to mice and humans ... . Simulations indicate that in mice, rats, and humans, about 80%, 60%, and 20%, respectively, would be metabolized via glutathione conjugation ... . This is consistent with observed levels of theta-class glutathione S-transferase (GSTT1) enzyme activity in the order mice > rats > humans. In rats and mice, GSTT1 activity was highest in the liver, followed by the kidney and testes. Rat brain and rat and mouse lung contained small amounts of activity compared with other tissues (enzyme activity in mouse brain was not examined). Ethylene oxide is a substrate for the human GSTT1 enzyme ... .

International Programme on Chemical Safety; Concise International Chemical Assessment Document Number 54: ETHYLENE OXIDE (2003). Available from, as of July 22, 2008: https://www.inchem.org/pages/cicads.html


4.4 Biological Half-Life

No reports found; [TDR, p. 694]

TDR - Ryan RP, Terry CE, Leffingwell SS (eds). Toxicology Desk Reference: The Toxic Exposure and Medical Monitoring Index, 5th Ed. Washington DC: Taylor & Francis, 1999., p. 694


Labeled ethylene oxide is primarily excreted in urine and a half-life of approximately 10 min was estimated for the first-order clearance of ethylene oxide in rodents.

USEPA/OPPTS; Revised Ethylene Oxide HED Risk Assessment for Reregistration Eligibility Document (RED) p.9 EPA-HQ-OPP-2005-0203-0100 (May 2007). Available from, as of July 21, 2008: https://www.regulations.gov/search/Regs/home.html#home


The elimination half life is estimated at 40 to 55 minutes in humans.

Dart, R.C. (ed). Medical Toxicology. Third Edition, Lippincott Williams & Wilkins. Philadelphia, PA. 2004., p. 1244


4.5 Mechanism of Action

Ethylene oxide is an electrophilic agent that alkylates nucleophilic groups in biological macromolecules .... Since ethylene oxide is formed during the metabolism of ethylene, a natural body constituent, endogenous as well as exogenous sources of ethylene and ethylene oxide contribute to background alkylation of proteins such as hemoglobin and albumin, as well as DNA ... . N-(2-Hydroxyethyl)valine (HEVal) and hydroxyethylhistidine (HEHis) adducts have been frequently monitored in tissues of workers exposed to ethylene oxide in occupational settings ... . Background levels of HEVal in non-smokers ranged from 9 to 188 pmol/g globin ... Studies of smokers exposed to ethylene oxide in cigarette smoke ... and occupationally exposed workers ... have revealed higher levels of hemoglobin HEVal adducts among individuals with a GSTT1 null genotype (ie, homozygous deletion of GSTT1 gene) than among those with a GSTT1 positive genotype (ie, having at least one copy of the GSTT1 gene). ...

International Programme on Chemical Safety; Concise International Chemical Assessment Document Number 54: ETHYLENE OXIDE (2003). Available from, as of July 22, 2008: https://www.inchem.org/pages/cicads.html


Ethylene oxide binding to DNA results primarily in the formation of 7-(2-hydroxyethyl)guanine (7-HEGua) ... . In DNA extracted from the lymphocytes of unexposed individuals, mean background levels of 7-HEGua ranged from 2 to 8.5 pmol/mg DNA ... Human tissue contains 10- to 15-fold higher levels of endogenous 7-HEGua than rodent tissue. ... In mice, half-lives for the removal of 7-HEGua in DNA from a variety of tissues (brain, lung, spleen, liver, and testes) were 1.5- to 3.9-fold lower than in rats ... . In both rats and mice, substantive depletion of glutathione pools has been observed following single exposure to high levels (ie, > 550 mg/cu m) of ethylene oxide ... although it should be noted that increases in tumour incidence have been observed at lower concentrations. ...

International Programme on Chemical Safety; Concise International Chemical Assessment Document Number 54: ETHYLENE OXIDE (2003). Available from, as of July 22, 2008: https://www.inchem.org/pages/cicads.html


The /physiologically based pharmacokinetic (PBPK)/ models for rats, mice, and humans are qualitatively similar in their elements and provide for interspecies comparisons of internal ethylene oxide dose. The models are consistent with the conclusion that ethylene oxide is acting as a direct-acting alkylating agent in humans and rodents. Quantitative differences in response in biomarkers of exposure and effect are accounted for by differences in basic physiology between rodents and humans, rather than by factors suggesting a different mode of action.

International Programme on Chemical Safety; Concise International Chemical Assessment Document Number 54: ETHYLENE OXIDE (2003). Available from, as of July 22, 2008: https://www.inchem.org/pages/cicads.html


Evidence for a common mechanism of carcinogenesis in humans and experimental animals comes from studies that have demonstrated similar genetic damage in cells of exposed animals and workers. The DNA damaging activity of ethylene oxide provides its effectiveness as a sterilant, and it is this same property that accounts for its carcinogenic risk to humans.

DHHS/NTP; SUBSTANCE PROFILES REPORT ON CARCINOGENS, ELEVENTH EDITION: Ethylene Oxide CAS No. 75-21-8 p.1. Available from, as of July 23, 2008: https://ntp.niehs.nih.gov/