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Ethylene Oxide (EtO)

Registration Review of Ethylene Oxide (EtO)

Ethylene Oxide (EtO) is an EPA-registered antimicrobial pesticide used to sterilize medical equipment and spices. It is the only sterilization method available for many medical devices and approximately 50 percent of all sterile medical devices in the United States are treated with EtO annually.

EtO is currently undergoing registration review, a process EPA conducts for all pesticides every 15 years to ensure that products can carry out their intended function without creating unreasonable risks to human health and the environment. EPA’s registration review of EtO focuses on mitigating EtO’s impact on human health and the agency has determined that EtO can pose risks to human health. In 2021, EPA will put forward specific, detailed mitigation measures in its proposed interim decision, which is the next step in the registration review process.

More information

  • EPA’s November 2020 draft risk assessment for the registration review found that inhaling EtO over many decades can cause cancer risks of concern. Therefore, additional mitigation measures are necessary to protect the health of workers and surrounding communities.
    • Read EPA’s press release about its draft risk assessment of EtO’s pesticidal use.
    • Read the draft risk assessment and other documents related to EtO’s registration review in docket EPA-HQ-OPP-2013-0244 at
    • Questions and Answers on the draft risk assessment
  • Learn more about how EPA is working to reduce EtO emissions to protect communities hosting EtO facilities under the Clean Air Act.

Nov. 2020 Draft Risk Assessment Questions and Answers

What did EPA’s 2020 draft risk assessment find regarding EtO’s impact on human health?

Inhaling EtO over many decades is known to cause cancers of the white blood cells (such as non-Hodgkin’s lymphoma, myeloma, and lymphocytic leukemia), and may cause breast cancer. Children are thought to be more susceptible to EtO than adults; those who are exposed to EtO early in life are more likely to develop cancer later in life. Chronic exposure to EtO can also cause neurological symptoms, including memory loss and impaired hand-eye coordination.

No EtO residues remain on spices at the time they are consumed, and residues of the EtO reaction products, ethylene chlorohydrin (ECH) and ethylene glycol (EG), do not exceed levels of concern.

Why is EPA allowing this chemical to be used despite its potential human health risks?

EPA considers EtO critical for sterilizing medical equipment and necessary to protect public health. According to the Food and Drug Administration (FDA), EtO is the only sterilization method available for many medical devices. Approximately 50 percent of all medical devices are treated with EtO in the United States annually. EtO treatment is also a principal method used to reduce bacterial levels in herbs and spices. The spice industry estimated that approximately 32 percent of herbs and whole spices are treated with EtO annually.

What are the alternatives to using EtO to sterilize medical devices and treat spices?

While certain devices can only be sterilized using EtO, some devices can be sterilized through other methods, including heat, gamma radiation, electron beam radiation, x-ray, and hydrogen peroxide plasma. FDA is holding an innovation challenge to find alternatives to EtO.

The primary methods for sterilizing spices are steam, irradiation, propylene oxide, and EtO. Which method is used depends on the pathogen of concern, particular characteristics of the spice, and whether the spice can withstand a particular treatment without significant degradation in quality.

How did EPA conduct this risk assessment?

The draft risk assessment considers available toxicity information and data from a range of analyses discussing how EtO was assessed, key differences in modeling approaches, the peer review process, and results. These sources include:

  • EPA Office of Chemical Safety and Pollution Prevention’s 2008 Reregistration Eligibility Decision;
  • EPA’s Office of Research and Development 2016 IRIS assessment, based on the available epidemiological data
  • Dose response results developed by the Texas Commission on Environmental Quality
  • Input from the EtO Task Force (an industry group comprised of EtO registrants);
  • CDC’s Agency for Toxic Substances and Disease Registry EtO Toxicity Profile; and
  • White paper submitted by Exponent (a third-party consulting firm).

Why isn't EPA choosing a single cancer risk value?

EPA has chosen to present a range of dose response results, developed by EPA and other organizations, all utilizing the same database. While there are differences in the assumptions and methods used to analyze this information, all of the assessments have identified cancer risks of concern from inhalation exposures. Based on the information provided in the draft risk assessment, mitigation measures are required to protect the health of workers and surrounding communities. EPA is committed to implementing measures that will mitigate EtO's risk to human health as quickly as possible.

How can pesticide labels mitigate the risk EtO poses to occupational handlers?

EtO is an EPA-registered antimicrobial pesticide. Pesticide labels are legally binding under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). The directions and precautions on EPA-accepted labels define who may use a pesticide, as well as where, how, how much, and how often it may be used. Risks of exposure to humans and the environment increase if the label is not followed. Failure to follow the label is a violation of federal law.

Currently, all labels require personal protective equipment (PPE) consisting of a long-sleeved shirt, long pants, shoes plus socks, chemical-resistant gloves and a respirator. If a worker’s eye or skin may come into contact with EtO or EtO solutions, they must wear chemical-resistant attire (e.g., apron or footwear) and face-sealing goggles, a full-face shield, or a full-face respirator.

Detailed mitigation will be proposed in the proposed interim decision following the publication and comment period of this draft risk assessment.

EPA also is working to reduce EtO emissions to the outdoor air by reviewing Clean Air Act rules for industries that emit EtO and by coordinating with state air agency partners to identify opportunities for early reductions. In addition, the agency is working to better understand background EtO in the air through monitoring at existing air toxics monitoring sites and is evaluating new technologies and methods for measuring the chemical. Learn more how EPA is working to reduce EtO emissions under the Clean Air Act.

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