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The U.S. Environmental Protection Agency (EPA) announced on August 22, 2018, that it was taking steps to address Ethylene Oxide (EO) emissions from industrial facilities across the country based upon results of the latest National Air Toxics Assessment (NATA) update. The latest NATA update was released by EPA the same day and identified EO as a significant contributor to potential elevated cancer and other significant health risks.

The US EPA has identified several types of industrial facilities that emit EO, including:

  • Miscellaneous Organic Chemical Manufacturers
  • Commercial Sterilizers
  • Synthetic Organic Chemical Manufacturers
  • Hospital EO Sterilizers
  • Polyether Polyols Production

With the August 22, 2018 press release, the US EPA outlined its regulatory strategy to address the risks posed by EO. Clean Air Act regulations governing facilities that emit EO will be reviewed to ensure adequate protection and actual emissions data, ambient air monitoring and modeling data will be gathered to gain a complete picture of EO emissions nation-wide and to guide US EPA's regulatory and enforcement priorities.


EPA updated its cancer risk calculations for the 2014 NATA to reflect the inhalation unit risk estimate (IRE) for EO from EPA's Integrated Risk Information System (IRIS) Assessment. The IRE is an estimate of the increased cancer risk resulting from chronic inhalation exposure for a lifetime. For EO the IRE in IRIS is .005 microgram/m3 and a chronic exposure of 0.1 parts per trillion of EO over the course of a lifetime results in an increased cancer risk of 1 in 1,000,000.

On September 20, 2018, the EO Panel of the ACC submitted a "Request for Correction" under the Information Quality Act (IQA) to correct information contained within the 2014 NATA Update published on August 22, 2018.

The American Chemistry Council (ACC) believes the EO IRE from EPA's IRIS Database is based upon a flawed IRIS Assessment that does not provide a realistic basis for the management of health risks posed by EO. The ACC argues that the risk specific concentration (RSC) of 0.1 parts per trillion established in EPA's IRIS Assessment is:

  • Not based upon the best available science and is not a scientifically supportable risk value
  • 19,000 times lower than the normal, endogenous levels of EO in the human body, and is
  • Orders of magnitude lower than levels of EO in clean, ambient air.

The ACC points out that such numbers would suggest that normal human metabolism and the breathing of clean, ambient air is sufficient to cause cancer and provide a clear demonstration of their concerns surrounding the RSC of 0.1 parts per trillion EO currently included in the 2014 NATA Update.

The ACC has proposed that the 2014 NATA be revised to exclude the EO IRIS Assessment's RSC of 0.1 parts per trillion and to instead use "scientifically-supportable" risk values both within the NATA and for future rulemakings and regulatory actions.

When following the ACC's proposed approach to exposure response analysis, the comparable concentration associated with a 1 in 1,000,000 risk is between 0.5 - 1.2 parts per billion - three orders of magnitude greater than the EO IRIS Assessment's RSC of 0.5 parts per trillion (.005 parts per billion). The ACC believes that this approach provides a much more realistic and scientifically sound picture of EO risk to human health.

Future Implications

Regardless of the outcome of the ACC's "Request for Correction" of the 2014 NATA, EO producers and consumers can expect the US EPA to place significant emphasis on enhanced regulation and  enforcement of their industries. Particularly, facilities regulated under the Miscellaneous Organic NESHAP (the "MON") in 40 CFR 63, Subpart FFFF. The US EPA is currently reviewing this regulation and is under court order to complete the review of the MON no later than March of 2020. EPA has been clear that it will place special emphasis on ensuring EO risk is properly addressed and reflected in revisions to this regulation.

Additionally, the US EPA has stated it plans to gather additional information from industrial EO emitters identified above, to determine whether full-scale review of the regulations governing these sources is also warranted.


It is expected that EPA will specifically review the following items to investigate whether the risk posed by EO identified in the 2014 NATA is due to:

  • Over-reporting of actual emissions in annual Toxic Release Inventory (TRI) Reports,
  • True residual risk remaining from properly implemented existing HAP standards (NESHAP and NSPS Standards), or
  • Non-compliance and/or improper implementation of the HAP standards currently in place.

Industrial sources of EO emissions, especially those located in communities of concern, should expect US EPA to not only conduct detailed "data gathering" inspections, but should expect US EPA led enforcement inspections that dive into the details of applicability determinations, control and treatment standards and day-to-day monitoring and work practice standards.

Trinity's Chemical Sector Services (CSS) is actively involved helping EO clients navigate this new and complex regulatory and public environment. If you have any questions or would like assistance with assessing the potential impacts of these updates to your facility, contact Inaas Darrat at (713) 552-1371 Ext. 209, David Dempsey at (630) 495-1470, or Gena Driscoll at (251) 391-5789.

Please note, Trinity will be providing a more in depth article related to this topic as part of Trinity's 2019 Winter Environmental Quarterly publication, and additional information will be covered as part of Trinity's complimentary webinar - USEPA's Emphasis on Ethylene Oxide - What This Could Mean for You - on November 27.