ethylene oxide
Meaning of ethylene oxide: The property that sterilizes is the property that harms, since the gas reacts with DNA whether that DNA belongs to a microbe or a person.
Definition of ethylene oxide
Ethylene oxide is a colorless, flammable gas used to sterilize medical equipment that heat or steam would destroy, and as a raw material for making other chemicals, including antifreeze. It kills microorganisms by chemically attacking their DNA and proteins, and that same reactivity is what makes exposure hazardous to people.
Why is it used to sterilize?
Steam under pressure is the usual method of sterilization, and it is cheaper, faster and harmless once it cools. It also melts plastics, ruins electronics and blunts optical instruments. Ethylene oxide works at low temperature and near ordinary humidity, and as a gas it diffuses through sealed packaging and into the narrow channels of tubing, so a device can be sterilized inside the wrapper it will be opened from. That combination makes it the standard for single use plastic supplies, catheters, implants, surgical kits and flexible endoscopes.
The trade is time. A cycle involves conditioning, exposure to the gas, and then a prolonged aeration period in which absorbed gas is drawn back out of the materials, since residue left in a device would carry into the patient. That whole process runs far longer than an autoclave cycle.
How does it kill?
The molecule is a strained three membered ring that opens readily and attaches itself to whatever it meets. Attaching to the DNA and proteins of a microorganism disrupts both, and the process needs no heat and works against bacteria, fungi, viruses and the resistant spores that survive many other methods. Nothing about that chemistry is selective for microbes, which is the root of its toxicity.
What are the health effects of exposure?
| Timescale | What has been observed |
|---|---|
| Short term, at higher concentrations | Irritation of the eyes, skin and respiratory tract, headache, nausea, and at high levels drowsiness and difficulty coordinating movement |
| Long term, repeated occupational exposure | Classified as a human carcinogen, with the strongest evidence for cancers of the blood and lymphatic system, and evidence for breast cancer in exposed women |
| Other | Damage to genetic material in exposed workers, and reproductive effects reported in occupational studies |
Because it is a reactive oxide with no safe reliance on smell as a warning, workplace use is governed by enclosed equipment, air monitoring, ventilation and legal exposure limits, and emissions from sterilizing plants are regulated as well.
Also known as
Used in a sentence
The single-use catheter kits were sterilized using ethylene oxide gas prior to distribution.
Good to know
Ethylene oxide sterilization is reserved for medical devices that cannot withstand steam sterilization, since the process requires a lengthy aeration period afterward to remove residual gas from the sterilized items.