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U.S. EPA’s Proposed Updates to Air Emissions Standards For Ethylene Oxide Commercial Sterilization Facilities

Posted: May 9th, 2023

Authors: Mike K. 

More than three years after posting an Advance Notice of Proposed Rulemaking (ANPRM), review of information submitted by industry in response to Clean Air Act (CAA) Section 114 requests, and significant public and industry outreach, the U.S. Environmental Protection Agency (U.S. EPA) has issued proposed revisions to regulations at 40 CFR Part 63, Subpart O, that require control of ethylene oxide (EtO) emissions from commercial sterilization facilities. These facilities include medical and surgical instrument and supply manufacturers, pharmaceutical and preparation manufacturers, and food manufacturers, including spice and extract manufacturers. U.S. EPA published the proposed changes in the Federal Register on April 13, 2023, and explained that the approach to the proposed revisions accounts for balancing the importance of public health with the importance of maintaining the supply of medical equipment. This action is one of several recent actions pertaining to EtO, including a concurrent action relating to pesticides and proposed amendments to rules regulating chemical plants a few weeks earlier.


The original rule was finalized in 1994 and experienced a few amendments through 2005 that relaxed certain provisions due to safety concerns and other considerations about the industry sector. In 2016, U.S. EPA updated the cancer risk value for EtO to reflect higher cancer risk in the Integrated Risk Information System (IRIS), which triggered the more recent activities mentioned above. Public outreach has continued following publication of the proposed rule, with a webinar held on May 1, 2023, and virtual public hearings held on May 2 and 3, 2023.


The proposed rule would:

  • Revise and/or establish standards for sterilization chamber vents (SCVs), aeration room vents (ARVs), chamber exhaust vents (CEVs), and two types of room air emissions (Group 1, consisting of pre-aeration emissions from EtO storage, dispensing, vacuum pump operations, and handling of sterilized material, and Group 2, consisting of post-aeration handling of sterilized material). An exemption for CEVs was added to the rule in 2001 due to safety concerns, and sources using less than 1 ton per year (tpy) of EtO are currently exempt from the emissions standards. The proposed rule would establish emissions standards and emissions reduction standards based on whether the source is existing or new, the EtO discharge points, and the annual EtO usage in tons per year. The range of emissions reduction standards varies from 99 percent to 99.94 percent, with emissions standards ranging from 3.2E-04 to 2.8E-03 pounds per hour (lb/hr).  Table 23 of the preamble provides a summary of the proposed standards. Also of note, U.S. EPA is proposing to define each individual SCV, ARV, CEV, the collection of Group 1 emissions, and the collection of Group 2 emissions as affected sources. Therefore, “reconstruction” of an existing affected source may be triggered more easily than if the term was defined as the collection of sterilization equipment, thereby subjecting that affected source to the more stringent requirements for new sources.
  • Require emissions from SCVs and CEVs to be routed under negative pressure when ducted to a control system and require most Group 1 and Group 2 room air emissions to operate in a permanent total enclosure (PTE). PTEs must meet the criteria of Method 204 of appendix M to 40 CFR Part 51.
  • Revise requirements related to emissions during periods of startup, shutdown, and malfunction (SSM). Exemptions for periods of SSM are proposed to be removed and certain work practice standards are proposed to be added. These proposed changes are in response to the 2008 vacatur of the SSM exemptions in the 40 CFR Part 63 General Provisions.
  • Require facilities to either monitor emissions using an EtO continuous emissions monitoring system (CEMS) or conduct routine performance testing and conduct additional parametric monitoring for pollution control. In addition to the original acid-water scrubber, thermal oxidizer, and catalytic oxidizer options, the proposed rule identifies new collection and control techniques, including gas/solid reactors, peak shavers (defined in the redline markup of the proposed regulation found in the regulatory docket), and PTEs. The proposed rule also expands the types of parameters to be monitored. Originally limited to ethylene glycol concentration or liquor tank level, the proposed rule allows liquor pH monitoring for acid-water scrubbers. Rather than the recommended oxidation temperature provided by the manufacturer, thermal oxidizers will set and monitor the temperature in or immediately downstream of the firebox, and catalytic oxidizers will set and monitor the temperature at the inlet and the temperature difference across the catalyst bed. Gas/solid reactors would require the use of an EtO CEMS.

If the emissions stream includes sources of EtO other than SVCs, other possible parameters include daily mass of EtO charged, room air EtO concentration, volumetric flowrate through the exhaust stack(s), and differential pressure, as applicable. Written procedures for monitoring are proposed to be required. If not using an EtO CEMS, performance testing will be conducted annually or every three years under certain circumstances, and U.S. EPA is proposing 24-hour runs for facilities using at least 10 tpy of EtO.

  • Add provisions for electronic reporting of performance test results and reports, performance evaluation reports, and compliance reports. An initial compliance report will be due within one year of publication of the final rule in the Federal Register, or within one year of the report template being available in the Compliance and Emissions Data Reporting Interface (CEDRI). Semi-annual and quarterly compliance reports are also proposed depending on the quantity of EtO used.
  • Require affected facilities to operate under the Title V operating permit program. An exemption for area sources to operate under a Title V operating permit was added to the rule in 2005, so for facilities that are not already (or no longer) operating under a Title V operating permit, a Title V operating permit application will be required. Although the timeline for this application may vary by state, initial Title V operating permit applications are due within 12 months of becoming subject to the permitting program; therefore, it is anticipated that a Title V operating permit application will be due within 12 months from the effective date of the final rule in the Federal Register.

U.S. EPA determined that fence line monitoring and associated work practice requirements are not necessary due to the feasibility of capturing room air emissions and the requirements to install and monitor PTEs and other control options. However, U.S. EPA is soliciting comments on the possibility of beyond the fenceline (i.e., ambient) monitoring.


The proposed rule imposes an abbreviated timeline for existing affected facilities to comply with the requirements, with a deadline no later than 18 months after the effective date of the final rule (compliance timelines are typically three years).   New sources must comply with the requirements upon startup.

Due to the increased attention paid to EtO emissions since 2016, many existing sterilization facilities already implemented additional control strategies prior to the proposed rule being issued. It will be important for these facilities, in addition to those that have not implemented changes, to review the proposed amendments to ensure their equipment and monitoring approaches will meet the proposed requirements. For example, are the proposed emissions standards and reductions being met? Are PTEs in place? Are the facility’s current averaging periods for emissions or parametric monitoring consistent with the proposed rule?

Comments on the proposed rule are due by June 12, 2023. In addition to comments regarding any aspect of the proposed rule, U.S. EPA is specifically requesting comments on 82 items and provides alpha-numeric identifiers to support the submittal of comments. Obviously, this blogpost cannot address each of the 82 items or even every change proposed. If your facility is looking for assistance in determining the impact of the proposed regulations on your facility’s compliance status, please contact me at mkendall@all4inc.com or 843.460.5378.


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