Ethylene oxide
Ethylene oxide is a flammable, colorless gas that is recognized as a known human carcinogen since 2000. It consists of a three-atom ring formed by two carbon atoms and one oxygen atom, and is primarily encountered through inhalation, ingestion, or skin contact. This compound is commonly used in fumigation, sterilization of medical equipment, and the production of antifreeze, particularly ethylene glycol. Despite its utility, ethylene oxide exposure is associated with an increased risk of various cancers, including leukemia, stomach, and breast cancers, among others.
Significant production of ethylene oxide has occurred in the United States since the 1920s, with estimates of annual production around 2.84 million metric tons as of 2023. Studies have indicated a likely causal relationship between ethylene oxide exposure and tumor development in workers, leading to stringent federal regulations on its use and emissions. The Environmental Protection Agency (EPA) has classified ethylene oxide as a hazardous air pollutant and has implemented measures to control its emissions, particularly in response to community concerns about health risks. Recent efforts aim to reduce emissions by up to 90% to protect public health and minimize cancer risks in affected areas.
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Ethylene oxide
ROC STATUS: Known human carcinogen since 2000
ALSO KNOWN AS: 1,2-epoxyethane, oxacyclopropane, dimethylene oxide, oxirane
RELATED CANCERS: Leukemia, stomach, lymphatic, myeloma, breast, pancreatic, and brain cancers
DEFINITION: Ethylene oxide is a flammable, colorless gas at temperatures above 51.3 degrees Fahrenheit. It is a three-atom ring made of two carbon atoms and one oxygen atom. Each of the two carbon atoms is bonded to two hydrogen atoms.
Exposure routes: Inhalation, ingestion, skin contact
Where found: Fumigation of foodstuffs, sterilization of hospital instruments, and various synthetic chemical operations
At risk: Workers in the detergent, fungicide, and synthetic chemical fields, especially those related to ethylene glycol manufacture
ETIOLOGY AND SYMPTOMS OF ASSOCIATED CANCERS: The high reactivity of ethylene oxide is shown by ring opening and the introduction of new carbon groups at reactive sites in deoxyribonucleic acid (DNA). This type of reaction takes place largely at a nitrogen atom of guanosine. Such modified nucleic acid fragments have been observed in mice and are most prevalent in the liver, kidney, spleen, and testis. A variety of mutations and reverse mutations have also been found. Gene mutations and heritable translocations are common.
History: Ethylene oxide has been produced in large quantities in the United States since 1921. Annual production ranges between 2.6 million and 3.4 million metric tons. According to the US National Toxicology Program's 13th Report on Carcinogens (2014), peak production in the United States reached over 4 million metric tons in 1999. In 2023, annual production in the US was estimated at 2.84 million metric tons. The 15th ROC also reported that ethylene oxide remained one of the top twenty-five chemicals produced in the United States in terms of production volume. Well over half of the production is consumed in the synthesis of the antifreeze, ethylene glycol. Ethylene oxide is also widely used to sterilize medical equipment and spices. In part due to efforts to make production of this chemical safer and reduce harmful emissions, releases of ethylene oxide to air in the US decreased by 43 percent between 2013 and 2022.
Five studies of workers exposed to ethylene oxide, beginning in the mid-1980s, showed that exposure produces statistically significant excess tumor appearance. There are difficulties in the interpretation of each of these studies, but a causal relationship between the compound and tumor production is likely. Animal studies involving rats, mice, and hamsters clearly show its carcinogenicity.
Federal regulations exist for the control of ethylene oxide. The Department of Transportation (DOT) lists the chemical as hazardous and requires special marking, labeling, and transporting precautions. The Environmental Protection Agency (EPA) considers ethylene oxide a likely carcinogen and requires that the manufacture of ethylene oxide meet provisions for the control of volatile organic compounds (VOCs). Also, under the Clean Air Act, the compound is listed as one of dozens of hazardous air pollutants that present the greatest threat to public health, and the EPA requires that as little as ten pounds of the substance be reported. The Occupational Safety and Health Administration (OSHA) has set the permissible exposure limit at one part per million for an eight-hour time-weighted average with a five parts per million excursion level.
In March 2024, due to pressure from people living in areas like Texas and Louisiana with high exposure rates to ethylene oxide and other environmental activists, the EPA released a new, stricter set of regulations for emissions of this chemical. These regulations, released as amendments to existing standards established under the Clean Air Act, would apply to any facilities that released ethylene oxide and aimed to reduce emissions by as much as 90 percent, with the hope that this could help lower cancer risks in surrounding communities.
Bibliography
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"Ethylene Oxide." American Chemistry Council, 2024, www.americanchemistry.com/chemistry-in-america/chemistries/ethylene-oxide. Accessed 25 June 2024.
"Ethylene Oxide." United States Environmental Protection Agency, 21 Mar. 2024, www.epa.gov/trinationalanalysis/ethylene-oxide. Accessed 25 June 2024.
“Ethylene Oxide - Cancer-Causing Substances.” National Cancer Institute, 10 June 2024, www.cancer.gov/about-cancer/causes-prevention/risk/substances/ethylene-oxide. Accessed 25 June 2024.
“Ethylene Oxide Sterilizers in Health Care Facilities (89-115) | NIOSH.” CDC, 1989, www.cdc.gov/niosh/docs/89-115/default.html. Accessed 25 June 2024.
“15th Report on Carcinogens.” National Toxicology Program, 21 June 2021, ntp.niehs.nih.gov/whatwestudy/assessments/cancer/roc. Accessed 25 June 2024.
Goodman, Brenda. "EPA Proposes New Regulations on Toxic Gas Used to Sterilize Spices and Medical Equipment." CNN Health, 11 Apr. 2024, www.cnn.com/2023/04/11/health/epa-regulations-ethylene-oxide-gas/index.html. Accessed 25 June 2024.
“Our Current Understanding of Ethylene Oxide (EtO).” Environmental Protection Agency, 3 Apr. 2024, www.epa.gov/hazardous-air-pollutants-ethylene-oxide/our-current-understanding-ethylene-oxide-eto. Accessed 25 June 2024.