Ethylene Oxide: A toxic gas you should know about

Medical technology today is pretty amazing.  In clinics and hospitals across the US, doctors and technicians use equipment to see inside, examine, and treat us in close detail.  Some equipment can be used many times, but must be properly sterilized between patients to avoid germ growth and transmission of diseases.  Ethylene Oxide, or EtO, is a gas used to sterilize catheters, endoscopes, surgical instruments, and implants, as well as various surgical kits, diagnostic tools, and some electronics that cannot tolerate heat or radiation.  Approximately 50 percent of all medical devices are sterilized with EtO, and for many of those it is the only option known to modern science. (Ethylene Oxide & Sterilization) It is also used as a pesticide for spices and dried herbs, dehydrated vegetables, sesame seeds, and walnuts, and to manufacture other industrial chemicals.  However, the sterilizing gas itself is dangerous to those who use it and even those who live nearby.  Who knew?

It seems that using a gas to sterilize equipment should not be a big deal–after all, unlike other businesses that clean things and produce toxic water or sludge, what can a gas do?  It turns out that EtO is very poisonous, and cannot be freely vented into the atmosphere after use because of its acute toxicity (immediate effects of exposure including respiratory irritation, nausea, vomiting, numbness and neurological effects, etc.) and its chronic toxicity (it’s a genotoxin, which is able to directly react with DNA and cause mutations leading to cancer).  According to this technical paper, it has a half-life in the atmosphere of 2-5 months, meaning that it doesn’t easily degrade into other gases.  If you are exposed to more than 0.1 parts per trillion of ethylene oxide, the EPA considers your EtO-related cancer risk unacceptable. The EPA has developed risk assessments for those who work in these sterilization facilities, as well as those who live, work, or go to school nearby.  According to this page, up to 1 in 17 workers at such a facility are expected to develop cancer over the course of a 35-year career; the same goes for up to 100 people in 1 million who are routinely exposed via proximity of their workplace or residence to the sterilization facility.  These cancers include non-hodgkin lymphoma, myeloma, lymphocytic leukemia, lung cancer and breast cancer. EtO exposure can also increase the risk of diseases of the nervous system and damage the lungs. Children may be more susceptible to these health effects because of their developing bodies. (Are you being exposed to EtO? Read and download our guide.)   

Here are some of the places EtO is released:

• From the plants that sterilize equipment: According to a 2023 analysis by the Union of Concerned Scientists, more than 14 million people live within 5 miles of commercial sterilization facilities, with 10,000 schools and childcare centers in these same areas.

• Trucks that transport the equipment after sterilization: Following sterilization, ethylene oxide evaporates, or off-gases, from the products/equipment. As a result, EtO concentrations can build up in shipping containers and trucks as the products are being transported, turning them into potentially significant sources of toxic air pollution. 

• Warehouses where companies house the equipment: EtO also off-gases in the warehouses that store medical devices after they’ve been sterilized. Often, medical supply warehouses are unmarked buildings in industrial parks, some distance from the company’s main sterilization plant, so they can be hard to pinpoint. The EPA does not require companies to regulate or monitor EtO emissions from warehouses.  This article contains a map showing warehouses that store products that are sterilized by EtO, and tells how you can identify such warehouses in your area. 

• Industrial chemical facilities: Some manufacture ethylene oxide or use it to manufacture other chemicals, such as antifreeze and pesticides (EtO is a key intermediate in the manufacture of ethylene glycol, which is the primary ingredient in antifreeze and coolant fluids).

• Finally, we can’t ignore the everyday items we encounter which also produce EtO, because it is produced in trace amounts in exhaust from combustion engines.  A chart from a website of a medical technology trade association shows that SUVs, gas grills, and especially gas generators emit EtO in quantities higher than the EPA's risk factor of 0.1 parts per trillion. This highlights the importance of air-sealing your attached garage (to keep it separate from your home) and keeping any gas generators a safe distance from your home. 

Here is an article containing a map that shows the location of sterilization and manufacturing facilities in the US that emit ethylene oxide.  Some facilities are grouped in the same geographical area, and sadly people in that area may be affected by multiple facilities.  Blue circles highlight the 23 commercial sterilizers that emit ethylene oxide at levels that definitively contribute to an  elevated cancer risk  for surrounding communities, as determined by the Environmental Protection Agency (EPA) in 2022.

Sadly, just like other industrial areas, these types of facilities are located closer to communities that are poor and minority-based.  In 2024, a sterilization plant called Sterigenics settled a lawsuit with plaintiffs residing near their Atlanta facility, one of which grew up within a few miles of it and was diagnosed with leukemia at 18 years old.  These types of cases can be difficult to prove cause and effect for the victims, because although documented leaks occur (between 2015 and 2019, nine alleged ethylene oxide leaks occurred at the plant in the case), the plant continues to deny responsibility for the health effects. (Atlanta Sterigenics to Pay $35M to Settle Ethylene Oxide Claims) 

Here again, it’s super-important to be aware of your surroundings, especially when deciding where you will work, play and live for a number of years.  True, sometimes we can’t help it when unhealthy neighbors move in, but by being “nosy” about what they do and their safety record, we might be able to sound the alarm and get them to keep it safe or get shut down.

Photo by Jason Mitrione on Unsplash