Published March 2025
Ethylene Oxide (EtO) is a highly reactive, colorless, and odorless gas used in a wide range of industrial facilities, including medical sterilization and chemical manufacturing. In the United States, EtO is currently used to sterilize 50% of all medical devices and some dried herbs and spices. It is also used in the production of detergents, thickeners, solvents, plastics, and other chemicals, most notably ethylene glycol (i.e., antifreeze). Information about the health effects of this compound and regulations to mitigate exposure in and around industrial facilities have evolved since we published our last EtO-related update, Considerations for Measuring Ethylene Oxide, in March 2024.
In 2016, the U.S. Environmental Protection Agency’s (EPA) Integrated Risk Information System (IRIS)—a program that evaluates health-impact information—set a recommendation to keep ambient exposure to EtO at or below 11 parts per trillion (ppt). This exposure level corresponds to a lifetime (70-yr) 1-in-10,000 chance of developing cancer for residential nonoccupational bystanders living near sterilization facilities with a continuous exposure of roughly 11 ppt. As the concentration of EtO in the air increases, so does the estimated cancer risk. Notably, this recommendation was beyond the capabilities of monitoring technologies that were available at the time, as was also the case in 1984 when the Occupational Safety and Health Administration (OSHA) established an EtO exposure limit for workers equal to 1 part per million (ppm) as an 8-hr, time-weighted average.
EtO National Emissions Standards for Hazardous Air Pollutants at Sterilization Facilities
As of April 5, 2024, EPA finalized the residual risk and technology review (RTR) for Commercial Sterilization Facilities under National Emission Standards for Hazardous Air Pollutants (NESHAP). The Ethylene Oxide Emissions Standards for Sterilization Facilities aimed to limit EtO emissions such that the associated cancer risk from ambient exposure never exceeds 1-in-10,000. The finalized RTR is a “final rule,” which established standards for destruction efficiency of EtO emissions from medical sterilization facilities. Specific regulatory requirements vary by facility size. Upon issuing the finalized RTR, the EPA estimated that the new standards would affect 88 existing facilities and 2 additional facilities expected to open soon, with a total implementation cost of $313 million. This RTR has been approved by the Director of the Federal Register, and is not subject to President Trump’s “Regulatory Freeze Pending Review” memorandum issued on January 20, 2025, even though EPA has announced plans to reconsider.
January 2025 Interim Decision
The EPA also released the Interim Decision for Ethylene Oxide (EtO) on January 14, 2025, which introduced measures to protect facility workers and communities near sterilization facilities that use EtO. Since EtO is used for anti-bacterial purposes, this Interim Decision was issued under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), which gives the EPA authority to regulate pesticides to protect the environment, consumers, and workers. The decision set new targets to be phased in over time, with worker exposure limits decreasing to 0.50 ppm by 2028, 0.25 ppm by 2030, and 0.10 ppm by 2035. It also finalized a number of other restrictions on the use of EtO, including separation of HVAC systems for areas where EtO is used at sterilization facilities from areas where it is not used and prohibiting the use of EtO in a number of industries, such as museums, libraries, cosmetics manufacturing, and musical instrument manufacturing. Finally, the Interim Decision requires medical device sterilization facilities to implement continuous, stationary indoor air monitoring to detect EtO concentrations at or above 100 ppb. The results of that monitoring must be made transparent to workers by January 16, 2026.
An interim decision takes effect immediately when it is published by EPA, but it may be amended or revised based on public comment before it is finalized. In keeping with the registration review process under FIFRA, a notice was published in the Federal Register announcing the availability of the Interim Decision for EtO. Procedures for registration review decisions by the EPA under the Pesticide Programs (CFR 155.58) state that a “case docket will remain open until all actions required in the final decision on the registration review case have been completed.” Documentation for the Interim Decision for EtO indicates that EPA expects to address information needs in certain topic areas, such as issuing one or more data call-ins (DCIs) for monitoring worker exposure. EPA’s process for re-evaluating the Interim Decision and/or issuing a final registration review within the next 8 years includes addressing these information needs. Once complete, a final registration review decision will be published as a final rule in the Federal Register.
The January 14, 2025, Interim Decision for EtO appears to be unaffected by President Trump’s “Regulatory Freeze Pending Review” memorandum, which (1) prevents any new rules being proposed in any manner until they have undergone review by an agency head appointed by the new President; (2) immediately pauses rules sent to the Office of the Federal Register that have not been published; and (3) asks agencies to “consider postponing for 60 days from the date of this memorandum the effective date for any rules that have been published in the Federal Register, or any rules that have been issued in any manner but have not taken effect…” (https://www.federalregister.gov/documents/2025/01/28/2025-01906/regulatory-freeze-pending-review). As of this writing, neither President Trump nor the EPA has indicated any expectations for altering the existing, multi-year trajectory for re-evaluating the Interim Decision or issuing a final registration review.
Key Takeaways
The IRIS-recommended exposure levels for EtO can be challenging for conventional, continuous monitoring technologies to reliably capture, a topic that my colleague, Dr. Ethan Emerson, is soon to address with a related post. Meanwhile, it is currently unclear whether or how President Trump’s administration may influence existing EtO regulations, especially the January 14, 2025, Interim Decision for Ethylene Oxide that is still subject to amendment or revision before it is finalized. That said, both the Interim Decision and the April 2024 NESHAP finalized RTR are currently in effect, and the regulated community should be making plans for compliance and anticipated DCIs.
Dana L. Coe
