An Open Memo to Medical Facilities using Ethylene Oxide as a Sterilant

Alternatives to the Use of Ethylene Oxide as a Medical Sterilant

From: Janette DeFelice, MD, MA
Subject: Reducing the Use of Ethylene Oxide as a Medical Sterilant
Date: August 10, 2019

Executive Summary

Hospitals are beacons of health and healing. Hospital practices should, above all, do no harm. As of the time of this writing, your hospital is participating in a practice that causes harm to workers, patients, and community members.

The use of ethylene oxide as a medical sterilant has been shown to cause pulmonary irritation and acute neurotoxic effects at best, explosions and cancer at worst. In fact, the 2014 National Air Toxics Assessment has shown that people in a community surrounding an ethylene oxide sterilization plant have a cancer risk of over 100 times the average.

Hospitals that have shifted away from the use of ethylene oxide as their method of sterilizing medical equipment have shown improvements not only in employee-, patient-, and community satisfaction, they have also seen increased efficiency and decreased cost.

Below, we recommend four options to explore:

  • the Amsco®V-PRO® maX Low Temperature Sterilization System (STERIS Corporation, Mentor, OH)
  • the STERRAD®100NX® Sterilizer (Advanced Sterilization Products, Irvine, CA)
  • the STERIZONE®125L+ Sterilizer (TSO3, Québec, Canada)
  • the Noxilizer (Baltimore, MD)

What is Ethylene Oxide?

Ethylene oxide (EtO) is an organic compound made up of two carbon atoms, 4 hydrogen atoms, and one oxygen atom. It is a highly-flammable gas at room temperature. In the past, EtO was mixed with chlorofluorocarbons (CFCs) as a diluent, but since concern over the effect of CFCs on the atmosphere, industry has shifted toward using 100% EtO for medical sterilization. This had the effect of reducing the adverse effects of the CFCs on the ozone layer, but also increased the toxic effects of the sterilant. Ethylene oxide has also been found to be carcinogenic (can be cancer-causing) [1], mutagenic (can cause changes in DNA of living organisms), and endocrine disrupting (can interfere with the normal activity of hormones, including sex-specific hormones) [2]. Despite this, and despite that fact that effective alternatives exist [3], since the 1950s ethylene oxide has been used as a medical sterilant, specifically for heat- or moisture-sensitive medical equipment.

Disadvantages of Ethylene Oxide

  • Inhalation can cause acute affects such as nausea/vomiting and neurological symptoms (lethargy, headache, dizziness, twitching)
  • Highly flammable, posing explosion risk
  • Cancer-causing
  • Mutagenic, causing changes in DNA
  • Endocrine disrupting, interfering with the normal function of hormones
  • Inefficient, long cycle time
  • Cost

Real-life Effects of Ethylene Oxide as a Medical Sterilant: Case Study

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The community of Willowbrook, IL has been suffering the ill-effects of the use of EtO to sterilize medical equipment thanks to a medical sterilization plant in the area called Sterigenics. As of the mid-1980s regulators knew that those who lived near the Sterigenics plant would be exposed to more than 14 times higher than safe levels of ethylene oxide[4]. The population exposed to this toxic chemical in Willowbrook, IL (as well as in Lake County, IL where another EtO sterilization plant exists) is estimated to be over 600,000 people. Furthermore, this map of the 2014 National Air Toxics Assessment clearly shows that people in the Willowbrook community surrounding the ethylene oxide sterilization plant have a cancer risk of over 100 times the average.

Alternatives to Using Ethylene Oxide as a Medical Sterilant

Several effective alternatives to using ethylene oxide as a medical sterilant are available. First, there is a process that uses vaporized hydrogen peroxide. It is called the Amsco® V-PRO® maX Low Temperature Sterilization System (STERIS Corporation, Mentor, OH). It uses something called a sterilization pulse, which utilizes a vacuum pulse to remove load moisture, then injects vaporized hydrogen peroxide into a chamber that is held at increased pressure, followed by air injection. The hydrogen peroxide is then converted to a harmless mixture of oxygen and water using a catalytic converter. This process does not require special venting.

The second option uses hydrogen peroxide vapor and gas plasma, called the STERRAD® 100NX® Sterilizer (Advanced Sterilization Products, Irvine, CA). Again, vaporized hydrogen peroxide is injected into a vacuum chamber. A gas plasma is then encouraged using a cycle of increased and decreased pressurization. Free radicals from the gas plasma aid in sterilization. Gases then go through a filter and are decomposed into oxygen and water vapor.

A third option, called the STERIZONE® 125L+ Sterilizer (TSO3, Québec, Canada), uses ozone and water vapor. This process also uses a vacuum chamber and hydrogen peroxide vapor. Hydroxyl radicals are then put to work to begin the sterilization process. Next, ozone is introduced for a number of cycles. Again, the exhaust is decomposed to oxygen and water. No special ventilation is needed.

Finally, the use of nitrogen dioxide is a fourth option, via the Noxilizer (Baltimore, MD). Nitrogen dioxide gas is injected into a chamber with a predetermined pressure to ensure the proper concentration of NO2gas. Then gas then enters the sterilization chamber for cycling. The nitrogen dioxide gas then goes through a neutralizing scrubber and can be vented safely.

Process Emissions
Ethylene Oxide 5-step process involving preconditioning and humidification, EtO gas introduction, exposure, evacuation, and air washes. Alkylating agent—disrupts DNA in microorganisms. This process requires special venting equipment. Ethylene Oxide is released into the atmosphere.
Amsco® V-PRO® maX Low Temperature Sterilization System Utilizes vaporized hydrogen peroxide (H2O2) at increased pressure. This process does not require special venting equipment. It uses a catalytic converter to convert H2O2 to O2 and H20.
STERRAD® 100NX® Sterilizer Utilizes vaporized hydrogen peroxide (H2O2) at increased pressure. Gas plasma is encouraged using cycle of increased and decreased pressurization. Free radicals aid in sterilization. Gases go through filter and are decomposed into O2and H2O vapor.
STERIZONE® 125L+ Sterilizer Utilizes ozone (O3), H2O vapor, and vaporized hydrogen peroxide (H2O2). O3 and hydroxyl radicals are used in sterilization process. This process does not require special venting equipment. Exhaust is decomposed to O2and H2O.
Noxilizer Utilizes nitrogen dioxide (NO2) gas NO2 gas goes through a neutralizing scrubber and can be vented safely. 

Benefits of Using Non-Ethylene Oxide Methods for Medical Sterilization

Aside from the health benefits conferred onto the surrounding community and staff, using non-ethylene oxide methods for medical sterilization has other benefits—namely, cost and efficiency.

Cost:Mary Hitchcock Memorial Hospital in Lebanon, New Hampshire took on the challenges of incorporating non-ethylene oxide methods for sterilization. They found that the cost of sterilizing per square foot with the non-EtO method was significantly less than the EtO method (EtO/CO2 mix = $12.00 per square foot, EtO/HCFC mix = $11.31 per square foot, Sterrad = $8.44 per square foot). They also found that sterilization time was less and labor needed to operate the system was less leading to increase cost savings and increased efficiency [5].

Efficiency:When St. Joseph’s Hospital and Medical Center in Phoenix, Arizona adopted the Amsco® V-PRO® maX Low Temperature Sterilization System to replace their EtO system, they also found that sterilization time was decreased. This decrease in sterilization time increased their output load by 250%. They also found that satisfaction among physicians and staff, as well as patients, increased.[6]

Making Changes in Your Healthcare Setting

Foster a culture of caring—Hospitals are places of respite, places of health and healing. Sterilization of medical equipment using ethylene oxide causes great harm to community members, including growing children, who are exposed to EtO emissions and to workers who are at risk of acute toxic effects, as well as being in a dangerous work environment with a flammable chemical. Look at your hospital’s mission statement and see if your hospital’s practices fit.

Open up to feedback from employees and the community—A hospital that puts the needs of the people it serves and the healthcare of its staff, workers that make hospital functioning possible, is a hospital that lives up to its purpose.

Make small changes at first—Add a non-EtO sterilization procedure to your current regime of EtO sterilizers. Measure efficiency, cost-effectiveness, employee-, patient- and community satisfaction.

Final Conclusions and Recommendations    

As a healthcare setting, your hospital has an unparalleled responsibility to look toward the health of others. Whether it be employees, patients, or members of the community, your primary duty is promoting health of well-being. As every physician who walks in through your door has taken the oath ‘Primum non nocere,’ ‘First do no harm,’ your ultimate goal should be not causing harm. As shown above, using ethylene oxide to sterilize medical equipment causes harm.

Our recommendation is that you choose one of the options presented above (the Amsco® V-PRO® maX Low Temperature Sterilization System, the STERRAD® 100NX® Sterilizer, the STERIZONE® 125L+ Sterilizer, or the Noxilizer) to add to your sterilization regimen. If your hospital is not prepared to make an investment in any additional equipment at this time, another option would be to outsource sterilization of medical equipment to a company that uses one of these methods.


  1. Jinot, J., et al., Carcinogenicity of ethylene oxide: key findings and scientific issues.Toxicol Mech Methods, 2018. 28(5): p. 386-396.
  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. Schneider, P.M., New technologies and trends in sterilization and disinfection.Am J Infect Control, 2013. 41(5 Suppl): p. S81-6.
  4. Hawthorne, M., Officials knew ethylene oxide was linked to cancer for decades. Here’s why it’s still being emitted in Willowbrook and Waukegan, in Chicago Tribune. 2018.
  5. Agency, E.P., Replacing Ethylene Oxide and Glutaraldehyde. 2002.
  6. Miller, R., Eliminating ETO Translates to Improved Efficiency for Phoenix Hospital, in Infection Control Today. 2014.


Photo by Olga Kononenko on Unsplash