What is Ethylene Oxide (EtO) sterilization? Benefits, Cancer Risk and Regulatory perspectives

Elle Winn

What is EtO Sterilization?

Ethylene Oxide (EtO) gas sterilization is one of the most common sterilization methods used for medical devices. The practice is critical to sterilizing temperature- or moisture-sensitive devices1 and is very efficient for sterilizing devices with complex geometries with limited access2. For some devices, EtO gas sterilization is the only sterilization that does not compromise the device’s function2. Approximately 50% of sterile medical devices in the United States are sterilized using EtO gas2.

EtO kills microbes via protein, DNA, and RNA alkylation which prevents microbes from performing their required metabolic functions1. EtO is highly effective at neutralizing microbes in this way; however, its potency also has a drawback in that it is harmful to humans in significant amounts. High exposure to EtO can cause EtO toxicity, which is characterized by dizziness, nausea, vomiting, headaches, and respiratory problems (coughing, sore throat, difficulty breathing)1. More severe side effects of acute EtO toxicity include convulsions, spontaneous abortions, and damage to nerves and genetic material1. Additionally, EtO has been indicated as a Group 1 carcinogen, meaning that based on clinical data, it is likely that the chemical can cause cancer in humans1.

Link between EtO and Cancer

A systematic literature review of animal studies evaluating the link between EtO exposure and increased cancer instances performed by Lynch et al3 shows a positive correlation between high levels of EtO exposure and cancer incidences. Notably, rats exposed to 33-100 parts-per-million (ppm) of EtO gas each day for approximately 2 years had statistically significant increases in cancer incidences3. However, a literature review of epidemiological studies that evaluated the rates of cancer instances in human workers who were exposed to EtO at a maximum of 1 ppm for 8 hours in the workplace and who had also worked in the environment for at least 1 year found no statistically significant increase in the risk for cancer or mortality compared to control groups3. These two analyses show that EtO is likely carcinogenic; however, the regulations in place to protect humans from the harmful effects of acute exposure are doing their job.

As EtO is a Group 1 carcinogen, it is imperative to remove as much excess EtO as possible from devices to be compliant with regulations. Despite being quickly absorbable by most materials, excess EtO can be removed from sterilized medical devices using aeration1.

FDA Stance

The FDA stands behind the use of EtO as a medical device sterilant4 and has many standards outlined for device sterilization protocols to protect patients2. Additionally, to minimize EtO pollution and protect environmental and public health, the EPA is creating new standards to reduce EtO pollution by an estimated 90%4,5.

Conclusion

At this point, studies show that the levels of EtO exposure associated with medical device sterilization are not likely to be cancer-causing; however, due to the classification of EtO as a Group 1 carcinogen, it is always beneficial to be vigilant and continue investigation on its impacts on health.

References:

(1)            CDC. Ethylene Oxide Sterilization. Centers for Disease Control and Prevention. https://www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/ethylene-oxide.html.

(2)            Center for Devices and Health. Sterilization for Medical Devices. Food & Drug Administration. https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/sterilization-medical-devices#ethylene.

(3)            Lynch, H. N.; Kozal, J. S.; Russell, A. J.; Thompson, W. J.; Divis, H. R.; Freid, R. D.; Calabrese, E. J.; Mundt, K. A. Systematic Review of the Scientific Evidence on Ethylene Oxide as a Human Carcinogen. Chem. Biol. Interact. 2022, 364, 110031. https://doi.org/10.1016/j.cbi.2022.110031.

(4)            Coburn, L.; Kapataneas, J.; Hawkins, S.; Young, A. EtO gas used to sterilize medical devices ignites fears over link to cancer. ABC News. https://abcnews.go.com/Health/eto-gas-sterilize-medical-devices-ignites-fears-link/story?id=108654614 (accessed 2024-01-02).

(5)            United States Environmental Protection Agency. Hazardous Air Pollutants: Ethylene Oxide. US EPA. https://www.epa.gov/hazardous-air-pollutants-ethylene-oxide

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