Ethylene Oxide Profile


CAS No. 75-21-8
IARC Supplement 7, 1987 (Group 2A)
IARC Monograph Vol. 60, 1994 (Group 1)
IARC Monograph Vol. 97, 2008 (Group 1)
IARC Monograph Vol. 100F, 2012 (Group 1)

Ethylene Oxide Profile

General Information

Ethylene oxide is a colourless gas with a characteristically sweet, ether-like odour.[1,2] It is highly flammable and dissolves easily in water, alcohol, and most organic solvents.[2] Produced since the early 1900’s, ethylene oxide has been used as a chemical intermediate and as a sterilizing agent.[3] Ethylene oxide may also be referred to as oxirane and EtO.[3] There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.[4]

Ethylene oxide was classified in 1994 by the International Agency for Research on Cancer (IARC) as Group 1, carcinogenic to humans.[3] The Volume 100 IARC review reaffirmed this classification, finding limited evidence in humans and sufficient evidence in animals for lymphatic and haematopoietic cancers, as well as breast cancer.[5] Mechanistic studies provided strong support for the Group 1 designation, as EtO is a potent alkylating agent, frequently showing genotoxic effects.[6] The effective sterilizing properties of EtO and its carcinogenicity both arise from its capacity to damage DNA.[1]

Ethylene oxide can irritate the eyes, skin, and respiratory system, and can cause central nervous system effects.[2] With chronic exposure, neurological effects including memory loss, peripheral neuropathies, and impaired coordination have been reported.[2] Asthmatic reactions can occur in individuals sensitized to EtO.[6] There is limited evidence that EtO exposure may be associated with increased risk of miscarriage.[2]

Regulations and Guidelines

Occupational exposure limits (OEL) [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]

Canadian Jurisdictions OEL (ppm)
Canada Labour Code 1 [sk]
AB, MB, NB, PE 1
QC 1 [em]
BC 0.1
1 [stel]
NL, NS 1 [sk]
NT, NU, SK 1
2 [stel]
ON 1
10 [stel]
YT 50
75 [stel]
Other Jurisdiction OEL (ppm)
ACGIH 2020 TLV 1 [sk]
ppm = parts per million
sk = easily absorbed through the skin
em = exposure must be reduced to the minimum
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value

Canadian environmental guidelines and standards*

Jurisdiction Limit Year
Ontario Ambient Air Quality Criteria Annual: 0.04 µg/m3 2016[22]
24 hour: 0.2 µg/m3 2016[22]
Alberta Ambient Air Quality Objectives and Guidelines 1 hr: 15 μg/m3 2017[23]
Government of Canada’s Indoor Air Reference Levels 0.002 µg/m3 (critical effect: lymphoid and breast cancer) 2018[24]
Quebec’s Clean Air Regulation 1 year limit: 0.0005 µg/m3; Prohibited discharge into the air if the concentration of ethylene oxide exceeds the standard 2011[25]
BC’s Contaminated Sites Regulation, BC Reg 375/96 Sets vapour standards for:
Agricultural, urban park, residential, commercial, and industrial air: 10 μg/m3
(Vapours derived from soil, sediment, or water)
Cosmetic Ingredients Hotlist Not Permitted 2004[27]
PMRA Registered for use as a bactericide 2016[28]
Health Canada’s Maximum Residue Limits for food Food type:
Vanilla: 7 ppm
Juniper berries: 7 ppm
Dried spices (e.g. black pepper, cinnamon, cumin, safron, thyme): 7 ppm
µg/m3 = micrograms per cubic meter
µg/g = micrograms per gram
µg/L = micrograms per litre
*Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects

EtO use is also monitored through the Pest Control Products Act. In order to reduce duplication in regulatory oversight, EtO was removed from Health Canada’s List of Permitted Food Additives with “Other Generally Accepted Uses (List 8)” in 2016.[30]

Canadian agencies/organizations

Agency Designation/Position Year
Health Canada DSL – low priority substance (already risk managed)* 2006[31]
CEPA Schedule 1, paragraph ‘c’ 2003[32]
National Classification System for Contaminated Sites Rank = “High hazard”; confirmed human carcinogen 2008[33]
Environment Canada’s National Pollutant Release Inventory Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than 10 tonnes. 2016[34]
* as oxirane
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act

Ethylene oxide was not included in other Canadian government guidelines, standards, or chemical listings reviewed.

Main Uses

Ethylene oxide is used as a chemical intermediate, primarily to produce ethylene glycol (antifreeze).[1]

Smaller amounts of EtO are used as sterilizing agents, disinfectants, fumigants, or insecticides.[1] Medical facilities (hospitals, medical and dental clinics) and manufacturers of sterile medical supplies account for the majority of its use as a sterilant.[1] In Canada, approximately 120 healthcare facilities use ethylene oxide as a sterilant.[35]

Other applications where EtO is used as a sterilant include heat sensitive materials such as furs, furniture, beehives, cosmetics, drugs, and tobacco,[1] and in publication and wood products industries.[5]

Ethylene oxide is used as a fumigant to control bacteria in spices and natural seasonings and to control insects in stored products.[5] There is one product listed with ethylene oxide as an active ingredient registered with the Canadian Pest Management Regulatory Agency (PMRA).[36]

Canadian Production and Trade

Production and trade

Activity Quantity Year
Canadian Production 108,400 t 2004[3]
Export 4 t of ‘oxirane (ethylene oxide)’ 2021[37]
Import 7,197 t of ‘oxirane (ethylene oxide)’ 2021[37]
t = tonne

Environmental Exposures Overview

There is limited data in Canada on the general population’s exposure to ethylene oxide, but the most important route of exposure is inhalation.[5] In one national study of 50 ambient air samples taken over 24 hours in randomly selected residential areas, 94% of the samples were below the detection limit.[5] The same study, looking at indoor air, reported 98% of samples below the limit of detection.[5]

Sources of environmental exposure to EtO are mainly products that have been sterilized with the compound, including medical products, foods, clothing, cosmetics, and beekeeping equipment.[1] A minor source of exposure to ethylene oxide is gasoline combustion and cigarette smoke (either residue from fumigation of tobacco, or as a combustion by-product).[2,5]

Data on EtO levels in water, soil, sediment and groundwater in Canada were not identified.[5]

Searches for EtO in Environment Canada’s National Pollutant Release Inventory (NPRI) and the United States Consumer Product Information Database yielded the following results on current potential for exposure to EtO in Canada:

NPRI and US Consumer Product Information Database

NPRI 2015[38]
Substance name: ‘Ethylene oxide’
Category Quantity Industry
Released into Environment 2.2 t Chemical manufacturing
(4 facilities)
Disposed of 22 t
Sent to off-site recycling None
US Consumer Products 2016[39]
Search Term Quantity Product Type
‘ethylene oxide’ 10 Coolant (1), transmission fluid (1), auto sealant (1), cleaner (4), laundry detergent (1), rust removers (1), and pet flea & tick control (1)
t = tonne

Occupational Exposures Overview

Inhalation is the most important route of occupational exposure to ethylene oxide.[2] CAREX Canada estimates that approximately 2,400 Canadians are exposed to EtO at work.

Although the majority of ethylene oxide is used to produce chemicals, most occupational exposure occurs through its use in sterilization, particularly of medical equipment.[1,40] The highest exposures have been measured in facilities using EtO as a sterilant or fumigant, including hospitals, healthcare facilities, and spice manufacturers.[41] Workers may be exposed while changing ethylene oxide gas cylinders; from leaking equipment; from improper ventilation at the sterilizer door, discharge line, aerators, and in the general room; during removal and transfer of items from the sterilizer to an aerator; and from incomplete aeration of items.[1] Ethylene oxide is registered for use as a disinfectant in six products listed in the Drug Products Database of Health Canada.[42] Some studies show that exposures during sterilization procedures can be effectively controlled by industrial hygiene measures.[1] Current average concentrations of ethylene oxide in hospitals and production facilities have decreased substantially from historical levels, to <2 mg/m3 in western Europe and North America.[1]

There is potential for exposure to EtO during production of industrial chemicals. However, these processes are usually automated and contained in closed systems, which minimizes exposure.[41] Exposures in the chemical industry occur mainly during loading and unloading of transport tanks, product sampling, and equipment maintenance and repair.[43]

For more information, see the occupational exposure estimate for ethylene oxide.


Photo: Flickr, Niklas Morberg

1. National Toxicology Program (NTP). 15th Report on Carcinogens for Ethylene Oxide (2016) (PDF)​
2. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Ethylene oxide (1990) (PDF)
3. International Agency for Research on Cancer (IARC). Monograph summary, Volume 97 (2008) (PDF)
4. US National Library of Medicine. PubChem (Search term: ‘Ethylene oxide’)
5. International Agency for Research on Cancer (IARC). Monograph summary, Volume 100 Part F (2012) (PDF)
12. Government of Newfoundland and Labrador. Regulation 5,12 Occupational Health and Safety Regulations (2018)
13. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2020) (PDF)
15. The Canadian Legal Information Institute (CanLII). Government of Nunavut’s Occupational Health and Safety Regulations, Nu Reg 003-2016 (2010)
17. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1 (2013) (PDF)
19. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
20. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2020) (PDF)
21. Occupational Safety and Health Administration (OSHA). Annotated PELs (2020)
22. Ontario Ministry of the Environment and Climate Change. Ontario’s Ambient Air Quality Criteria (2019)
23. Alberta Environment and Parks. Ambient Air Quality Objectives (2019)
24. Government of Canada. Summary of indoor air reference levels (2018)
25. Government of Quebec. Clean Air Regulation, Q-2, r. 4.1 (2020)
26. Government of British Columbia. Contaminated Sites Regulation B.C. Reg. 375/96 (2021)
27. Health Canada. Cosmetic Ingredient Hotlist (2019)
28. Health Canada. Pesticide Label Search (2016)
31. Health Canada. Prioritization of the DSL (2006)
32. Environment and Climate Change Canada. CEPA List of Toxic Substances (1999)
33. Canadian Council of Ministers of the Environment. National Classification System for Contaminated Sites (PDF) (2008)
35. Grosse, Y. et al. “Carcinogenicity of 1,3-butadiene, ethylene oxide, vinyl chloride, vinyl fluoride, and vinyl bromide.” Lancet Oncol2007;8(8):679-680.
36. Health Canada. Product Label Search (2016)
37. International Trade Centre. TradeMap (Free subscription required)
38. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI) Facility Search (Substance name: ‘Ethylene oxide’)
39. Consumer Product Information Database (CPID) What’s in it? (2022) (Search term: ‘Ethylene oxide’)
41. World Health Organization (WHO). CICAD No. 54: Ethylene oxide (2003) (PDF)
42. Health Canada. Drug Product Database (2009)


Other Resources

  1. Agency for Toxic Substances and Disease Registry (ATSDR). ToxFAQ Sheet for Ethylene Oxide (1999) (PDF)

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