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Hazardous Air Pollutants: Ethylene Oxide

Agency Actions on Ethylene Oxide

Under Administrator Michael S. Regan’s leadership, EPA has a renewed commitment to protecting human health and the environment by following science, enforcing environmental laws and engaging with communities as we do our work.

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EPA is taking a closer look at regulations to address ethylene oxide emissions. The agency anticipates issuing a proposed rule for commercial sterilizers in 2021. In addition, the agency is beginning work to review other regulations for facilities that emit ethylene oxide. These include complex rulemakings, which can take about three years to complete. The following rules are under review, with their anticipated final date:

  • Commercial Sterilizers:  2022
  • Hospital Sterilizers:  2023
  • Group 1 Polymers and Resins (Neoprene):  2024
  • Synthetic Organic Chemicals Manufacturing Industry:  2024
  • Polyether Polyols Production:  2024
  • Chemical Manufacturing Area Sources:  2024


EPA is continuing to work with states to measure ethylene oxide in the outdoor air. In late 2019, EPA added EtO to the list of pollutants that will be routinely measured at National Air Toxics Trends Stations (NATTS) and Urban Air Toxics Monitoring Program (UATMP) networks to learn whether EtO is present more broadly in the air in the U.S.

Because EtO can be difficult to analyze, EPA has been providing training for states that use their own laboratories to assist them as they begin analyzing air quality samples for this pollutant.  Sample results are uploaded to EPA’s Air Quality System (AQS) after they are quality assured. AQS houses outdoor air quality data collected by EPA, state, local, and tribal air pollution control agencies across the country. EPA has prepared a paper which provides more information on the agency's work to understand ambient levels of ethylene oxide

Gathering Emissions Information

For ethylene oxide, facility emissions data, combined with air quality modeling, can provide a more complete picture of ethylene oxide in the air in an area than air quality monitoring can currently provide. Existing monitoring methods are not sensitive enough to detect ethylene oxide at all levels in the outdoor air. EPA is actively working to develop new techniques for measuring ethylene oxide in the outdoor air.

In addition, data from emissions testing can be used in the review and development of air toxics regulations; data from air quality monitoring cannot. Under the Clean Air Act, air toxics regulations focus on setting limits on the amount of a pollutant an industrial facility can emit to the air.

The information EPA obtains will help the Agency as it evaluates opportunities to reduce ethylene oxide emissions as part of its regulations review. It also will help EPA determine whether more immediate emission reduction steps are possible in any locations.


EPA Administrator Michael S. Regan has directed several EPA Regions to update information on emissions and risk in areas identified in the 2014 NATA (released in 2018) where outreach had not been conducted, and to share that updated information with communities. That work is underway and will be continuing this summer.  In addition, EPA is compiling more current and complete emissions data to generate new risk estimates for the more than 100 EtO sterilizers across the country as part of its work to review the air toxics regulation for ethylene oxide commercial sterilizers. These estimates will be updates to the NATA estimates. EPA will share this information with the public as part of its upcoming proposed rule.

Learn more about technical and outreach efforts in the regional status reports as part of the follow up to the Inspector General.