Ethylene Oxide

At a Glance

Ethylene oxide (EtO), a known human carcinogen, is a colorless, flammable gas that is used to sterilize medical equipment and to make chemicals used in household and personal care products. During this process, traces of EtO are sometimes left behind. During the 1980s, it is estimated that more than 270,000 U.S. workers were exposed to the chemical every year. The use of EtO has since decreased in the United States, though it is still used.

What is ethylene oxide?

Ethylene oxide is a fumigant used to sterilize surgical equipment. It is also used in a process called ethoxylation, in which ethylene oxide is added to ingredients to make them less irritating. Ethoxylated products are widely used in personal care and household cleaning products.[1] The majority of ethylene oxide is produced in order to manufacture other chemicals.[2]

When in contact with ethylene oxide, humans absorb it through their skin or breathe it in.[3] Once it enters the bloodstream, EtO exhibits endocrine-disrupting capabilities.[4]

Where is ethylene oxide found?

Ethylene oxide is found in highest concentrations in the manufacturing plants that create it. It is also prevalent in hospitals, where it is used to sterilize medical equipment.[5]

Smaller quantities of EtO can be found in fragrances, shampoos and other cosmetic items as well as cigarette smoke.[6],[7]

What evidence links ethylene oxide to breast cancer?

The International Agency for Research on Cancer (IARC) classifies ethylene oxide as a known human carcinogen.[8]

Female Swedish, Hungarian and American hospital and manufacturing  workers who were exposed to varying levels of ethylene oxide had elevated incidences of breast cancer.[9],[10],[11],[12]

Ethylene oxide interferes with biological processes that build proteins and replicate DNA.[13] EtO does this by binding to DNA and causing mutations that can stop cells from making proteins. Most cells have the ability to recognize and repair unexpected changes that chemicals can cause, but others replicate too quickly to do so. Epithelial cells outline blood vessels, and stromal cells make up tissues that support the structure of organs. These are examples of quickly replicating cells that sometimes miss the changes that EtO makes.[14] These sorts of alterations in breast epithelial and stromal cells can cause carcinomas and sarcomas respectively.[15],[16]

There is also extensive evidence of carcinogenicity in rats and mice. After inhaling ethylene oxide, animals presented with mammary tumors. The tumor incidence increased when animals were exposed to higher concentrations of EtO.[17],[18],[19]

A study conducted on human cells in vitro showed that even small levels of exposure to EtO caused DNA damage in epithelial breast cells. This damage worsened as cells were treated with higher concentrations, demonstrating the sensitivity of breast epithelial cells to EtO.[20]

Who is most likely to be exposed to ethylene oxide?

  • Hospital personnel who sanitize surgical instruments using ethylene oxide.[21]
  • People who work in ethylene oxide manufacturing plants.[22]

Who is most vulnerable to the health effects of ethylene oxide?

People who work in close contact with ethylene oxide are most vulnerable to its health effects. Exposure to higher concentrations of EtO increase these risks.[23]

What are the top tips to avoid exposure?

  • Workers who are exposed to ethylene oxide should wear protective eye gear and clothing, and should use respirators when exposed.[24]
  • First- and secondhand cigarette smoke should be avoided.[25]
  • Avoid personal care products with ethoxylated ingredients. These show up on the label with the suffix –eth (ceteareth, laureth, steareth, etc.), the abbreviations PPG or PEG, or polysorbate.
  • Be aware of other names for ethylene oxide: Dihydrooxirene; dimethylene oxide; EO; 1,2-epoxyethane; epoxyethane ethene oxide; EtO; ETO; oxaxyclopropane; oxane; oxidoethane [26].

[1] Agency for Toxic Substances and Disease Registry (ATSDR). (1990). Toxicological profile for ethylene xide. U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA.

[2] Norman, S., Berlin, J., Soper, K., Middendorf, B., & Stolley, P. (1995).Cancer Incidence in a Group of Workers Potentially Exposed to Ethylene Oxide. International Journal of Epidemiology, 24(2).

[3] Liteplo, R., Meek, M., & Lewis, M. Concise International Chemical Assesment Document 54: Ethylene Oxide. (2003). World Health Organization. http://www.who.int/ipcs/publications/cicad/en/cicad54.pdf. Retrieved July, 2015.

[4] Norman, S., Berlin, J., Soper, K., Middendorf, B., & Stolley, P. (1995). Cancer Incidence in a Group of Workers Potentially Exposed to Ethylene Oxide. International Journal of Epidemiology, 24(2).

[5] IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: 1,3 Butadiene, Ethylene Oxide and Vinyl Halides (Vinyl Fluoride, Vinyl Chloride and Vinyl Bromide). (2008). World Health Organization International Agency for Research on Cancer 97.

[6] Konduracka E, Krzemieniecki K, Gajos G. Relationship between everyday use cosmetics and female breast cancer. Pol. Arch. Med. Wewn. 2014 Jan 1;124:264-9.

[7] Fennell, T., MacNeela, J., Morris, R., Watson, M., Thompson, C., & Bell, D. (2000). Hemoglobin Adducts from Acrylonitrile and Ethylene Oxide in Cigarette Smokers: Effects of Glutathoine S- Transferase T1-Null and M1-Null Genotypes. Cancer Epidemiological Biomakers, 9:705.

[8] IARC Monographs on the Evaluation of Carcinogenic Risks to Humans Volume 100F (2012). Ethylene oxide available at http://monographs.iarc.fr/ENG/Monographs/vol100F/mono100F-28.pdf. Retrieved July 2015.

[9] Mikoczy Z, Tinnerberg H, Björk J, Albin M. Cancer incidence and mortality in Swedish sterilant workers exposed to ethylene oxide: updated cohort study findings 1972–2006. International journal of environmental research and public health. 2011 Jun 3;8(6):2009-19.

[10] Norman, S., Berlin, J., Soper, K., Middendorf, B., & Stolley, P. (1995). Cancer Incidence in a Group of Workers Potentially Exposed to Ethylene Oxide. International Journal of Epidemiology, 24(2)

[11] Steenland, K., Whelan, E., Deddens, J., Stayner, L., & Ward, E. (2003). Ethylene Oxide and Breast Cancer Incidence in a Cohort Study of 7576 Women (United States). Springer, 14(6) 531-539.

[12] Toma, A., Major, J. & Jakab, M. (1999). Is breast cancer cluster influenced by Environmental and occupational factors among hospital nurses in Hungary? Pathology Oncology Research, 5(2)

[13] Liteplo, R., Meek, M., & Lewis, M. Concise International Chemical Assessment Document 54: Ethylene Oxide. (2003). World Health Organization. http://www.who.int/ipcs/publications/cicad/en/cicad54.pdf.  Retrieved July, 2016.

[14] IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: 1,3 Butadiene, Ethylene Oxide and Vinyl Halides (Vinyl Fluoride, Vinyl Chloride and Vinyl Bromide). (2008). World Health Organization International Agency for Research on Cancer 97.

[15] Types of Breast Cancers: Histologic examples of in situ & invasive carcinomas of the breast. (2015). Johns Hopkins University. http://pathology.jhu.edu/breast/types.php. Retrieved July, 2016.

[16] Ádám, B., Bárdos, H. & Ádány, R. (2005). Increased genotoxic susceptibility of breast epithelial cells to ethylene oxide. Genetic Toxicology and Environmental Mutagenesis, 585 120-126.

[17] Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide: In Support of Summary Information on the Integrated Risk Information System (IRIS). (2014). National Center for Environmental Assessment. https://yosemite.epa.gov/sab/sabproduct.nsf/fedrgstr_activites/82E68A48EE8ED66685257BA600556607/$File/CARCINOGENICITY-OF-ETO-FOR-SAB-CAAC-REVIEW.PDF.  Retrieved July, 2016.

[18] Rudel RA, Attfield KR, Schifano JN, Brody JG. Chemicals causing mammary gland tumors in animals signal new directions for epidemiology, chemicals testing, and risk assessment for breast cancer prevention. Cancer. 2007 Jun 15;109(S12):2635-66.

[19] Houle, C., Ton, T., Clayton, N., Huff, J., Hong, H. & Sills, R. (2006). Frequent p53 and H-ras Mutations in Benzene- and Ethylene Oxide-Induced Mammary Gland Carcinomas from B6C3F1 Mice. Toxicologic Pathology, 34:752.

[20] Ádám, B., Bárdos, H. & Ádány, R. (2005). Increased genotoxic susceptibility of breast epithelial cells to ethylene oxide. Genetic Toxicology and Environmental Mutagenesis, 585:120-126.

[21] IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: 1,3 Butadiene, Ethylene Oxide and Vinyl Halides (Vinyl Fluoride, Vinyl Chloride and Vinyl Bromide). (2008). World Health Organization International Agency for Research on Cancer 97.

[22] IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: 1,3 Butadiene, Ethylene Oxide and Vinyl Halides (Vinyl Fluoride, Vinyl Chloride and Vinyl Bromide). (2008). World Health Organization International Agency for Research on Cancer 97.

[23] Steenland, K., Whelan, E., Deddens, J., Stayner, L., & Ward, E. (2003). Ethylene Oxide and Breast Cancer Incidence in a Cohort Study of 7576 Women (United States). Springer, 14(6) 531-539.

[24] OSHA Fact Sheet: Ethylene Oxide. (2002) U.S. Department of Labor. https://www.osha.gov/OshDoc/data_General_Facts/ethylene-oxide-factsheet.pdf.  Retrieved July, 2016.

[25] Fennell, T., MacNeela, J., Morris, R., Watson, M., Thompson, C., & Bell, D. (2000). Hemoglobin Adducts from Acrylonitrile and Ethylene Oxide in Cigarette Smokers: Effects of Glutathoine S- Transferase T1-Null and M1-Null Genotypes. Cancer Epidemiological Biomakers, 9:705.

[26] Steenland, K., Whelan, E., Deddens, J., Stayner, L., & Ward, E. (2003). Ethylene Oxide and Breast Cancer Incidence in a Cohort Study of 7576 Women (United States). Springer, 14(6) 531-539.

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