Ethylene oxide has long been a mainstay in sterilizing medical equipment. It is widely used at commercial sterilization facilities, and on a smaller scale, EtO has qualities that make it ideal for delicate precision instruments. The problem with EtO is that it has been shown to be toxic to humans.

Citing a body of research dating back to the 1980s, the Environmental Protection Agency called EtO a “potent cancer-causing air pollutant” in a 2024 report in which it vowed to cut emissions from large-scale commercial EtO facilities by 90% in just a few years.

In anticipation of these findings by the EPA, the FDA, in turn, held a town hall last January to tackle this complex subject. In the discussions, it was clear the FDA recognized that because of EtO’s effectiveness and its outsized role in the medical device supply chain (accounting for 50% of commercial sterilization), phasing it out entirely presents a real potential for “medical device shortages due to the lack of alternatives to EtO.”

The possible negative effects of large-scale off-gassing of EtO from commercial plants into communities is clear, but what is less known are the dangers it presents to patients and providers when used on a smaller scale.

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Garland-Rhea Grisby, CER, CFER, CSPDT, an endoscope service manager at Kaiser Permanente, in Oakland, Calif., and the co-chair of the Association for the Advancement of Medical Instrumentation’s (AAMI’s) working group that focuses on endoscope reprocessing, has his concerns. “The method of sterilization that you’re using, you have to ask yourself, what is it doing to the user?”

There is not much literature on the subject. To date there have been few, if any, studies on the effects of EtO on the people performing the sterilization, those using the instruments and those treated by them.

Despite the lack of data, the potential risks led the American Hospital Association to caution its members to find alternatives as far back as 2019. The organization listed a few options, including hydrogen peroxide vapor, which was recognized by the FDA in January as a class A sterilant that could be considered an alternative to EtO, as well as e-beam and gamma radiation. However, none of these modalities is as advantageous as EtO, and all parties involved—the FDA, EPA and providers—acknowledge that there are not many options to replace EtO, especially when it comes to sterilization of delicate precision instruments.

Mr. Grisby noted that AAMI’s working group recommends sterilization practices that are approved by the FDA, but said the choice really depends on what instruments and scopes a practice or clinic is using. “The key is to find out if the scope is compatible with the sterilization methods that are available. The choice of sterilization method could depend on the outcome, the cost and the effects on the users,” he said. “AAMI does not endorse one sterilization method over the other. There are a few different compatible sterilization processes out there, such as EtO, hydrogen peroxide with or without plasma phase, and hydrogen peroxide–ozone sterilization systems.”

How We Got Here

What drove healthcare “toward EtO years ago was the fact that it was a low-temperature sterilization method that was extremely effective,” Michelle Alfa, PhD, MSc, a certified clinical microbiologist (retired) and the CEO of AlfaMed Consulting, in Winnipeg, Manitoba, told GEN Priority Report. Although the safer technique of “steam sterilization is the best option that can be used in healthcare,” she said, “there are no flexible endoscopes that I’m aware of that actually can withstand steam sterilization.”

It’s for these reasons, Bret Petersen, MD, a professor of medicine at Mayo Clinic in Rochester, Minn., told GEN Priority Report, that in an era when there is this push by some to move away from EtO, Mayo Clinic and other centers continue to use the modality.

Back in 2014 and 2015, around the same time the EPA began to reevaluate EtO, outbreaks of a multidrug-resistant organism occurred in hospitals across the globe. The FDA suggested sterilization with EtO as one of a few processing modalities capable of having a positive effect.

“At that time, we had a very underutilized EtO processing facility in the basement of our clinic in Rochester, Minnesota,” Dr. Petersen recounted. “We have continued with high-level disinfection as has been used for many years across the country in most sites, and for duodenoscopes only, we then send them to EtO sterilization.” It is what he referred to as a belt-and-suspenders type of approach. “We know that EtO has been the one modality that has been employed to break each of the outbreaks.”

Other centers take this approach too, relying on high-level disinfection only, according to Dr. Alfa, or they choose to use a mix of scopes including single-use scopes, which eliminate the need for reprocessing.

Rigorous Protocol

Regarding the dangers to those who work with EtO or are treated with instruments sterilized by it, Dr. Petersen said he has not seen literature to support what may be an outsized fear and noted that Mayo’s methodology is rigorous. “You can’t start the machine without the room being locked down and sealed. [The instrument] is put under an intense prolonged vacuum to ensure clearance of any residual EtO on the devices.”

EtO also is expensive and time-consuming to use, experts agreed. The overall process takes almost a day to minimize the dangers to providers and patients, Dr. Petersen noted. “With most EtO facilities, the treatment itself is fairly brief, but the cycle of treatment is [17-20 hours] because of the evacuation component” needed for the EtO to dissipate.

However, “when so much of the procedure is allowing the instrument to sit so that it can be safely handled,” Mr. Grisby remains concerned about EtO’s residual toxicity.

Coordination With Scope Makers Required

Moving away from EtO as the go-to means of sterilization is a long-term process. “Transitioning from one sterilization modality to another is a complex challenge,” commented AAMI Vice President of Sterilization Amanda Benedict, MA, CStd, in a press release from the organization. Ms. Benedict underscored that “for any medical device, the device manufacturer needs to be sure that the sterilizing agent is compatible with the materials that comprise the device to ensure no negative impact on device functionality.”

Currently, when it comes to full sterilization at low temperatures, there really is no best second choice, Dr. Alfa said, and until there is one, on a small scale, EtO will still remain the go-to option.

—W. Harry Fortuna

The sources reported no relevant financial disclosures.

This article is from the December 2024 Priority Report print issue.