Frequent Questions about Ethylene Oxide (EtO)
Ethylene oxide (EtO) is a gas that is produced in large volumes at some chemical manufacturing facilities. It is used to make other chemicals that are then used to make a range of common products, including antifreeze, plastics, detergents, and adhesives. It is also used to sterilize devices that can’t be sterilized using steam or radiation, such as some medical and dental equipment. According to the Food and Drug Administration, approximately 50 percent of sterile medical devices are treated with EtO – about 20 billion devices each year. EtO also is used to sterilize some food products such as spices, certain dried herbs, dried vegetables, sesame seeds and walnuts.
Please see the information below for answers to frequently asked questions about EtO.
Does EtO cause cancer?
Yes, EtO is a human carcinogen. It causes cancer in humans. Scientific evidence in humans indicates that exposure to EtO for many years increases the risk of cancers of the white blood cells, including non-Hodgkin lymphoma, myeloma, and lymphocytic leukemia. Studies also show that long-term exposure to EtO increases the risk of breast cancer in women.
People who live near facilities that release EtO to the outdoor air may be exposed to EtO, depending on how much EtO is released and how close they live to the facility.
What is the main way people are exposed to ethylene oxide?
Breathing air containing EtO is the main way people are exposed to ethylene oxide. Here are some ways people may be exposed to EtO in the air:
- Workers may be exposed to EtO if they work in places where EtO is produced or used, such as chemical plants and commercial or hospital sterilizers.
- People who live near facilities that release EtO to the outdoor air may be exposed to EtO, depending on how much EtO is released and how close they live to the facility.
- People also can be exposed to EtO from tobacco smoke.
Has EPA measured ethylene oxide in mobile source exhaust?
No, EPA has not confirmed that ethylene oxide is present in mobile source exhaust. We are working diligently to develop test methods that will allow us to carefully evaluate combustion sources, including mobile sources, to determine the extent to which ethylene oxide may be emitted.
The pandemic has impeded our ability to do the laboratory research needed to address this question, but we remain committed to understanding whether mobile sources and other combustion sources emit ethylene oxide.
Studies from the 1980s reported ethylene oxide in emissions from mobile sources. Why isn’t EPA relying on these studies?
While some preliminary studies from 50 to 60 years ago suggested that ethylene oxide may be formed when fuels are burned in an engine or in other combustion conditions, this work used methods that are outdated, and have significant uncertainties. It is not clear that the investigators identified ethylene oxide as an emission product. Because of the lack of robust data and research into the potential for formation of ethylene oxide in combustion, EPA is working to develop methods that will allow us to carefully evaluate combustion sources, including mobile sources, to determine if ethylene oxide is being emitted.
Are levels of ethylene oxide in my area high enough to cause immediate health effects?
No. The short-term (one-hour) estimated levels in the air are well below levels that may immediately cause serious, long-lasting or irreversible noncancer health effects.
When did EPA know about the cancer risks from ethylene oxide?
What we know about ethylene oxide has changed over time. EPA changed its toxicity value for EtO in December 2016. The new value, which we use in risk assessments, reflects our updated understanding that EtO is 60 times more toxic than the previous estimate. This includes the fact that children are more sensitive to EtO than adults because they are growing.
Knowing how toxic a chemical is just one piece of understanding risk. We also need to know how much of that chemical is emitted to the air, and how long people are exposed to it.
We put those pieces together in 2018, with the release of our National Air Toxics Assessment. That was the first time EPA used the updated toxicity value for EtO, and it highlighted the increased risks from sterilizers and other EtO sources. We’ve continued to use the updated value in all other assessments that look at EtO, including the assessment we are conducting for the upcoming commercial sterilizers rulemaking.
Are children at risk?
Children are more sensitive to EtO than adults. This is because ethylene oxide can damage DNA, and growing children are more susceptible to DNA damage because their cells divide more rapidly than adults. The contribution to lifetime cancer risk from a single year of exposure to ethylene oxide is greater if that year occurred during childhood. For everyone, including children, risks would decrease with decreased exposure.
Did ethylene oxide from the commercial sterilizer in our town cause my cancer?
We don’t know. Our risk assessment cannot tell us if a person’s cancer is attributable to EtO or the facility’s EtO emissions. The development of cancer is a complex process and there are many factors that can impact an individual’s cancer risk, including their genetics and overall health.
How far away from the facility do I have to be so that I am not at risk?
Unfortunately, there is not a simple answer to how far away is far enough, because many factors impact how far EtO can travel and how long it stays concentrated in outdoor air. As EtO moves through the air, it becomes less concentrated. How much and how quickly this happens depends on weather conditions, such as wind speed. How much a facility emits, exactly where the emissions leave the facility, and the amount of dispersion all impact how far EtO travels and whether it will remain at high enough concentrations to pose long-term risks.
I live close to a commercial sterilizer and think I and my family are being exposed to ethylene oxide. How do I take care of my health?
Taking care of your and your family’s health is always important. Keeping up with regular medical checkups and recommended health screenings is an important part of taking care of your and your family’s health.
For Adults: If you have health concerns that you believe may be related to EtO exposure in the outdoor air, start by discussing these concerns with your healthcare provider. In addition, the Agency for Toxic Substances and Disease Registry (ATSDR) can help answer general questions about associations between EtO exposure and health conditions based on research study evidence. They can also answer questions about biological testing, its limitations, and why CDC/ATSDR does not recommend blood testing in a community setting. You can reach ATSDR at: EtO@cdc.gov. Note: Don’t smoke! Tobacco smoke also contains ethylene oxide.
For children: Keeping up with your child's regular well checkups and age-appropriate health screenings is an important part of taking care of your child's health. If you have concerns about your child's health that you believe may be related to EtO exposure in the outdoor air, start by discussing these concerns with their healthcare provider. In addition, you or your child's healthcare provider can contact the Pediatric Environmental Health Specialty Units (PEHSU), a network of experts specializing in the impacts of environmental factors on the health of children and reproductive-age adults. Find PEHSU experts for your area.
Is ethylene oxide produced by the human body?
Yes, our bodies produce ethylene oxide when metabolizing ethylene. Ethylene is produced naturally in the body. The amount of ethylene converted to ethylene oxide in the body is unknown. However, ethylene is easily lost from the body through exhalation, which limits the amount of ethylene oxide produced.
I’ve been living in a community with a commercial sterilizer for many years. What is my risk of getting cancer?
Cancer is a complex disease with many causes, and EPA can’t estimate any one individual’s risk of getting cancer.
What EPA is able to do is to estimate the risk of developing cancer from breathing air containing EtO emitted from a particular facility or group of facilities. Those estimates are based on the amount of EtO the facility currently puts into the air and assume people living nearby are breathing air containing EtO 24 hours a day for 70 years. This risk is in addition to the risk of cancer from other causes.
EPA can’t estimate risk based on past exposure. How risks have changed over time depends on whether emissions were higher or lower in the past. We have current information about how much ethylene oxide has been emitted recently, but we don’t have information going back many years. Since we don’t have emissions information going back very far, we can’t be sure how risks may have changed over time.
I don’t live near the facility, but I work near it, and my child goes to school near the facility, too. What is our risk?
We can’t give you an exact estimate on that. Our models show that the amount of EtO in the air drops off as you get further away from the facility.
Different people might also have different levels of risk depending on how they are exposed to EtO.
EPA is working to reduce the risks EtO creates for people who spend time near sterilization facilities in two ways:
- By updating Clean Air Act rules for facilities that put ethylene oxide into the air, and
- Using our authority under federal pesticide law to change how EtO is used in sterilizer facilities.
What about workers at the facility? What is their risk?
In 2020, EPA issued a draft risk assessment as part of its review of EtO as a registered pesticide. That assessment determined that EtO poses risks to workers and that mitigation is required to protect workers’ health.
EPA is working to use our authority under federal pesticide law to change how EtO is used in sterilizer facilities. The Agency will propose specific, detailed measures to better protect the health of workers. As part of that assessment, EPA will coordinate with the Occupational Safety and Health Administration (OSHA), which sets limits for worker exposure to EtO.
What does a "1-in-1 million" cancer risk mean?
A lifetime cancer risk of 1-in-1 million means that, for every 1 million people who are continuously exposed to a certain level of a pollutant over 70 years, one person may develop cancer. These risks are on top of any other cancer risks from other sources.
Ethylene oxide is in a group of chemicals called “air toxics.” As part of EPA’s regulatory program for air toxics, we look closely at risks at or above 100-in-1 million to evaluate whether and how much the risk should be reduced. This approach helps EPA target our actions/efforts to communities facing the highest levels of risk.
Why did you use modeling to assess risk around these facilities? Wouldn’t monitoring be better?
A monitor tells us about EtO only in the area where the monitor is located. But computer models let us look at EtO across an entire community – not just at the monitor location. In addition, current monitoring methods cannot detect EtO down to all risk levels. For calculating risk across every part of a community, our experts believe that computer modeling gives us the best estimate possible of EtO concentrations in the air and the risks from breathing that air over many decades. Modeling also allows us to quickly examine how risks are expected to change when emission controls are installed, for example.
What is EPA doing to reduce ethylene oxide emissions?
EPA is reviewing Clean Air Act regulations for sterilizing facilities and for chemical manufacturing facilities that emit ethylene oxide to ensure they protect the public from significant risk.
Chemical manufacturing facilities
- In August 2020, EPA published revised regulations for Miscellaneous Organic Chemical Manufacturing facilities that require additional controls on certain equipment and processes that emit EtO in order to reduce risk to surrounding communities.
- EPA also is gathering additional information on emissions of ethylene oxide from the chemical manufacturing industry. In January 2022, EPA sent a request for information to eight chemical manufacturing entities subject to air emission standards.
- This information will help EPA as it looks for opportunities to reduce ethylene oxide emissions as it reviews chemical manufacturing regulations (such as the synthetic organic manufacturing emission standards) and as it identifies opportunities for near-term EtO reductions.
- EPA is currently reviewing its regulations for commercial sterilizers. The Agency will propose revisions to those rules soon.
- EPA and states have worked, and continue to work, in partnership to achieve near-term EtO emission reductions at commercial sterilizing facilities. This has resulted in successfully reducing EtO emissions and risk at several sterilization facilities.
- In December 2021, EPA extended Toxics Release Inventory (TRI) reporting requirements to 29 commercial sterilization facilities.
Is EPA going to monitor for EtO in my community?
- EPA believes that air modeling is a better tool for assessing risk, because it lets us look at EtO across an entire community – not just at a monitor location. In addition, EPA’s current method for measuring EtO cannot detect it when levels in the air are very low, meaning we cannot measure it at all levels of risk. Modeling does allow us to estimate risk at all levels.
While we are not planning to conduct monitoring in communities, we will continue to provide technical assistance for state and local agencies that want to conduct monitoring. Air monitoring in the U.S. is typically done by state and local air agencies, with support from EPA. In addition, EPA is conducting research to improve air monitoring techniques and technologies to better detect EtO at lower levels.
What level of ethylene oxide (EtO) in the air is safe ? Will EPA set a standard limiting EtO to that level?
- EPA is committed to reducing risks in communities with high risk from exposure to EtO from industrial facilities. As we update our regulations for facilities that emit EtO to the air, we will be looking at reducing emissions, which will reduce risk.
- EtO is a type of air pollution known as “hazardous air pollutant” or “air toxic.” The Clean Air Act tells EPA to regulate air toxics by setting limits on emissions. In other words, we have to require limits on the amount of the chemical that different industrial sources put into the air. So, for chemicals like EtO, EPA has to regulate what comes out of a facility instead of setting a specific level for the outdoor air.
Where can I find more information about ethylene oxide?
- You can start at EPA’s Ethylene Oxide website.
- Find out where to learn more.
- Visit CDC’s National Institute for Occupational Safety and Health webpage on Ethylene Oxide for additional information.