Ethylene oxide is a colourless gas with a characteristic sweet ether-like odour.[2,3] It is highly flammable and dissolves easily in water, alcohol, and most organic solvents. Produced since the early 1900’s, ethylene oxide has been used as a chemical intermediate and as a sterilizing agent.
Ethylene oxide may also be referred to as oxirane and EtO. There are numerous other synonyms and product names; see HSDB for more information.
Ethylene oxide has recently been classified by IARC as Group 1, carcinogenic to humans, with sufficient evidence of carcinogenicity in humans. Initially classified as Group 2A, with links to lymphatic and hematopoietic cancers, the upgrade to a known carcinogen is based on current epidemiological studies of workers exposed to EtO as a sterilizing agent and during chemical synthesis and production. A recent IARC review reaffirmed this classification, with strong evidence for lymphoid and breast cancers. Mechanistic studies support the Group 1 designation, as EtO is a potent alkylating agent, frequently showing genotoxic effects. EtO’s effective sterilizing properties and its carcinogenicity both arise from its capacity to damage DNA.
Ethylene oxide causes irritation of the eyes, skin and respiratory system, as well as central nervous system effects. With chronic exposure, neurological effects including memory loss, peripheral neuropathies and impaired coordination have been reported. Asthmatic reactions can occur in individuals sensitized to EtO. There is limited evidence that ethylene oxide exposure may be associated with increased risk of miscarriage.
Ethylene oxide is used as a chemical intermediate, primarily for the production of ethylene glycol (antifreeze). Other chemicals produced using EtO include glycol ethers, ethanolamines, alkanolamines, polyglycols, ethoxylates and choline chloride.
Smaller amounts of EtO are used as sterilizing agents, disinfectants, fumigants or insecticides. Medical facilities (hospitals, medical and dental clinics) and manufacturers of sterile medical supplies account for the majority of its use as a sterilant. In Canada, approximately 120 healthcare facilities use ethylene oxide as a sterilant. Information on use of ethylene oxide for sterilization in smaller clinics, such as veterinary and dental clinics, is currently unavailable.
Other applications for use as a sterilant include heat sensitive materials such as furs, furniture, beehives, cosmetics, drugs and tobacco, and in the publication and wood products industries.
EtO is used as a fumigant to control bacteria in spices and natural seasonings and to control insects in stored products.
Canadian Production and Trade
In 2004, ethylene oxide was produced by Dow Chemical Canada. (2 locations in AB), Shell Canada (AB), Alberta & Orient Glycol (AB).
Production and Trade
Export: Mainly to Argentina
68 t of ‘oxirane (ethylene oxide)’
Import: Mainly from US, Korea
7 t of 'oxirane (ethylene oxide)'
t = tonne
Inhalation is the most important route of occupational exposure to ethylene oxide. Although the majority of ethylene oxide is used for the production of chemicals, most occupational exposure occurs through its use in sterilization, particularly of medical equipment.[2,25] The highest exposures have been measured in facilities using EtO as a sterilant or fumigant, including hospitals, health care facilities and spice manufacturers. Workers may be exposed during the changing of 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. Ethylene oxide is registered in 9 products in the Drug Products Database of Health Canada for use as a disinfectant. Some studies have shown that exposures during sterilization procedures can be effectively controlled by industrial hygiene measures. 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.
Potential exists for exposure to EtO during the production of industrial chemicals. These processes are usually automated and contained in closed systems, however, which minimizes exposure. Exposures in the chemical industry occur mainly during loading and unloading of transport tanks, product sampling, and equipment maintenance and repair.
There is limited data in Canada measuring the general population’s exposure to ethylene oxide, but the most important route of exposure is inhalation. In one national study of 50 ambient air samples (24 hour) taken in randomly selected residential areas, 94% of the samples were below the detection limit. The same study, looking at indoor air, reported 98% of samples below the limit of detection.
Sources of environmental exposure mainly originate from products that have been sterilized with the compound, including medical products, foods, clothing, cosmetics, and beekeeping equipment. A minor source of exposure to ethylene oxide is from gasoline combustion and cigarette smoke (either residue from fumigation of tobacco, or as a combustion by-product).[3,6]
Data on ethylene oxide levels in water, soil, sediment and groundwater in Canada were not identified.
Searches of environmental and consumer product databases yielded the following results on current potential for exposure to ethylene oxide in Canada:
NPRI and US Household Products Database
Search term: ‘ethylene oxide'
Released into Environment
Chemical manufacturers and hospitals (9 companies)
Sent to off-site recycling
US Household Products 2010
Rust remover and driveway cleaner
t = tonne
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. To learn more about policies specific to ethylene oxide on the Directory, click here. For questions about this resource, please contact Michelle Halligan, from the prevention team at the Canadian Partnership Against Cancer.