The short answer
Ethylene oxide is a gas used to sterilize medical devices and make other chemicals. Breathing it, mainly at work or near some facilities, is linked to blood cancers and breast cancer. Emissions controls reduce exposure.
Ethylene oxide is classified as a known human carcinogen (IARC Group 1).
People are mainly exposed by breathing the gas at work or near certain sterilizing facilities.
Lymphoma and leukemia are reported most often; stomach and breast cancers may also be linked.
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
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The full explanation.
The simple version
Ethylene oxide is a gas. It is used to sterilize medical equipment that heat would damage, and to make other chemicals. Breathing it over time is linked to certain blood cancers. The people most exposed are workers and some communities near sterilizing plants.
What ethylene oxide is
Ethylene oxide is a colorless, flammable gas. It is widely used to sterilize medical and dental equipment. It also goes into products such as antifreeze and detergents. The EPA has taken steps to cut emissions from sterilizing facilities.
How people are exposed
Common ways people come into contact with it:
- Working in medical-device sterilization or chemical manufacturing
- Living near some commercial sterilizing facilities
- Tobacco smoke contains small amounts
The cancer connection
Lymphoma and leukemia are the cancers most often reported with workplace exposure to ethylene oxide. Stomach and breast cancers may be linked as well. The evidence is strongest in exposed workers.
The World Health Organization runs a cancer agency called the International Agency for Research on Cancer, or IARC. It places ethylene oxide in Group 1, carcinogenic to humans. That is the strongest evidence category. It means there is enough evidence that the gas can cause cancer in people. The US National Toxicology Program agrees, listing ethylene oxide in its Report on Carcinogens as known to be a human carcinogen.
Hazard is not the same as risk
Two ideas get mixed up here. One is hazard. The other is risk. Listing ethylene oxide as a carcinogen is a statement about hazard. It says the gas can cause cancer under some conditions. On its own it says nothing about your personal risk. That depends on how much gas you breathe, for how long, and on other factors. A sterilization worker and a person driving past the plant share the same hazard and face very different risks. The listing answers whether the gas can cause cancer. It does not answer how likely that is for you.
How to lower your exposure
- Rely on workplace exposure limits and emissions controls
- Support EPA measures that reduce facility emissions
- Do not smoke
One gas is only part of the picture. Our overview of cancer prevention and our page on what raises cancer risk show where a single exposure fits.
The bottom line
Ethylene oxide is a known human carcinogen (IARC Group 1). Learn where the exposure comes from, and take sensible steps to cut it. The label by itself does not need to keep you up at night. For most people, the largest gains come from the risks they can control day to day, such as smoking.
Words to know
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Common questions
Does ethylene oxide cause cancer?
Yes. Ethylene oxide is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
How are people exposed to ethylene oxide?
Most exposure happens by breathing the gas at work or near certain sterilizing facilities.
Which cancers are linked to ethylene oxide?
Lymphoma and leukemia are the cancers most often reported with occupational exposure. Stomach and breast cancers may also be linked.
How can I reduce my exposure to ethylene oxide?
The main steps are workplace exposure limits and facility emissions controls.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether ethylene oxide can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
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Last updated: 2026-08-10Next planned review: 2028-07-05
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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