What Is Ethylene Oxide (EtO)?

Published Oct 8, 2021

Ethylene oxide (EtO) is a flammable, colorless gas used to sterilize medical equipment and other plastics that are sensitive to heat or moisture. It's also a health threat to workers and communities.

The US Food & Drug Administration (FDA) estimates that EtO is used to sterilize about half of all medical equipment, including bandages, sutures, and stents. It is also used to make other chemicals, including antifreeze. Workers in facilities that produce and use EtO and people living near facilities that release it into the atmosphere are at risk of unsafe exposures even when the facilities are using the best available technologies to handle and contain it.

What are the health effects of exposure to EtO?

The US Environmental Protection Agency (EPA), the National Toxicology Program, and the International Association of Research on Cancer classify EtO as a substance that can cause certain cancers.

Chronic exposure to EtO is associated with the development of cancers of the white blood cells, such as non-Hodgkin lymphoma, myeloma, and lymphocytic leukemia. Studies have also shown a relationship between EtO exposure and breast cancer in women. Also, because EtO is mutagenic—meaning it can change a cell's DNA—children may be especially susceptible to its effects.

Who is at most risk from EtO exposure?

In 2016, the EPA's Integrated Risk Information System (IRIS) classified ethylene oxide as 'carcinogenic to humans' via exposures associated with inhaling the gas. This classification resulted in changes to the National Air Toxics Assessment, which revealed that more than 100 communities across the United States are exposed to ethylene oxide concentrations above the level the EPA deems safe.

The EPA's National Air Toxics Assessment was developed as a screening tool for state, local, and tribal air agencies to identify which pollutants, emission sources, and places may require additional investigation to better understand any possible risks to public health from air pollution. Long-term exposure to ethylene oxide is significantly contributing to higher cancer rates in some of the areas located close to facilities that emit the chemical, and disproportionately harm communities of color and low-income communities living near the fenceline of heavy industrial polluters.

It's important to note that fenceline communities are dealing not only with health effects from EtO but from the cumulative exposure to a variety of other hazardous chemicals resulting from a legacy of systemically racist policies.

According to the EPA's Office of the Inspector General, the census tracts nearest 14 of the 22 ethylene oxide-emitting facilities contributing to unacceptable cancer risks are made up of majority people of color and/or low-income households. One such community, St. John the Baptist Parish in Louisiana, has concentrations of ethylene oxide and the potent carcinogen chloroprene in the air that pose a cancer risk more than 200 times greater than those at levels the EPA deems acceptable.

At another EtO-emitting facility in Willowbrook, IL, the Illinois Department of Health conducted air monitoring and found that rates of Hodgkin's lymphoma among women in the nearby community were nearly 90 percent higher than those in a nearby county.

But most fenceline communities do not have access to this type of information. Without fenceline monitoring near these facilities, communities lack access to information about the exposures and health risks they face. The EPA has failed to communicate the high risks posed to community members in many communities near EtO-emitting facilities.

A 2020 EPA Inspector General report found that that the EPA had not reached out to 65 percent (16 of 25) of high-risk facilities identified by the EPA's data as contributing to unacceptably high cancer risks—many of which are located in communities of color and low-income communities. The EPA must act to protect communities from exposure and give them the information they need to advocate for change.

How is the federal government responding to this public health threat?

Reacting to the high cancer risk posed to communities near EtO-emitting facilities, the EPA proposed changes to its Miscellaneous Organic Chemical Manufacturing (MON) rule in 2019, regulating toxic emissions for about 200 chemical plants that produce solvents, plastics, and pesticides across the country. So-called MON facilities are especially concentrated in EPA's Region 6 in Texas and Louisiana, and disproportionately affect communities of color and low-income communities.

The EPA's final rule, issued in 2020, would require technological fixes to reduce EtO emissions but would continue to allow periodic, uncontrolled releases of chemical pollution and fugitive emissions into communities without monitoring. These continued emissions would leave people exposed to cancer risks at twice the level the EPA considers acceptable under the Clean Air Act. After the rule was issued, UCS joined 10 community, scientist, environmental, and environmental justice groups represented by Earthjustice on a petition for its reconsideration.

Pressure and input from an engaged public including local residents and community groups, scientists, and technical experts, along with nonprofits and coalitions working on this issue, has led the EPA to take action to protect the public. The EPA has announced that it is beginning to work on rules to curb EtO emissions at sterilizing facilities and hospital sterilizers across the country. The MON rule may be reconsidered as well. During those processes, public comments will be accepted, and all substantive comments must be considered by the agency in their rulemaking.

The Food and Drug Administration (FDA) has also acknowledged that the agency has a role to play in identifying alternatives to EtO for sterilizing medical equipment. In 2019, it announced two innovation challenges in which FDA would work closely with companies to identify alternative approachesto EtO use that are safe and effective and the development of strategies to reduce emissionsfrom the EtO sterilization process.

What else should be done to protect people from EtO?

The EPA needs to urgently act to update its emissions standards and residual risk reviews for facilities emitting ethylene oxide during the sterilization process and in the production of chemicals. To do this, it must:

  • Continue to rely on the EPA's assessment of the cancer risk from EtO. The EPA's Integrated Risk Information System (IRIS) assessments use the best available science to determine whether chemicals cause harm to human health, yet current industry-related efforts seek to undermine the IRIS EtO cancer risk value. The EPA needs to continue using their own robust scientific research and should rely on it to support the agency's EtO regulations.
  • Remove loopholes that allow periodic, uncontrolled emissions. Uncontrolled EtO emissions from industry processes continue to be a major problem and need to be regulated in future MON rulemaking.
  • Implement fenceline monitoring for EtO near all commercial sterilizers and MON facilities. Communities need and deserve strong protections, and this starts with having thorough data collection of EtO levels in fenceline communities.
  • Ensure new risk reviews include a margin of safety to protect public health. The EPA uses so-called "residual risk reviews" of chemicals to determine whether more health-protective standards are needed. In its review of EtO, the EPA should prioritize having an ample margin of safety to ensure that the people most at risk of experiencing health harms due to EtO exposure are protected.
  • Conduct public outreach to communities affected by ethylene oxide emissions, particularly those living with cumulative air pollution exposures in fenceline communities and those near highest-risk facilities. Communities must have opportunities to directly discuss their health concerns and inform the decisions made about the facilities directly harming their health.
  • Work toward requiring a complete phase-out. With other less toxic alternatives available, the EPA should continue working to phase out EtO at all commercial sterilizers.

More from UCS on EtO

Related resources