FACT SHEET
Reconsideration of the 2020 National Emission Standards for Hazardous Air Pollutants
(NESHAP) Final Rule: Miscellaneous Organic Chemical Manufacturing
Residual Risk and Technology Review
ACTION
• On December 14, 2022, the U.S. Environmental Protection Agency (EPA) finalized a decision
reaffirming its assessment of health risks associated with ethylene oxide, a harmful cancer-
causing pollutant emitted by commercial sterilizers, chemical production facilities, and
other industrial sources. This action will ensure that EPA's decisions relating to ethylene
oxide are based on the best available science.
• This decision completes the Agency's reconsideration of the 2020 National Emission
Standards for Hazardous Air Pollutants (NESHAP) for the Miscellaneous Organic Chemical
Manufacturing source category ("2020 MON final rule"), and reflects careful consideration
of public comments received on EPA's proposed reconsideration of the 2020 MON final rule
earlier this year.
• This action addresses two issues: (1) the use of EPA's 2016 Integrated Risk Information
System ("IRIS") value for ethylene oxide in assessing cancer risk for the source category; and
(2) the use of the Texas Commission on Environmental Quality (TCEQ)'s less-protective risk
value for ethylene oxide as an alternative to EPA's more protective 2016 IRIS value for
purposes of evaluating risk under Clean Air Act section 112(f)(2).
• EPA has decided to retain its decision to use the 2016 IRIS value for ethylene oxide when
assessing risk from Miscellaneous Organic Chemical Manufacturing facilities in the 2020
MON final rule. As described in detail in the decision, the 2016 IRIS value reflects the best
available science on health impacts of ethylene oxide and was subject to rigorous internal
review, interagency review, external peer review, and public comment. Commenters
provided no information that called into question the science underpinning the 2016 IRIS
value.
• Further, EPA has determined that TCEQ's risk value for ethylene oxide is unsuitable for use
as an alternative to the 2016 IRIS value. EPA's assessment of TCEQ's risk value found that it
excludes important scientific evidence on the health risks of ethylene oxide, and is based on
a risk model that is inconsistent with the epidemiological data and resulted from a flawed
analytical approach.
• As such, in this final action, EPA is making no changes to the risk assessment or emission
standards for the miscellaneous organic chemical manufacturing source category.
BACKGROUND
• On August 12, 2020, the U.S. Environmental Protection Agency (EPA) published 2020 MON
final rule, pursuant to Clean Air Act (CAA) sections 112(f)(2) and 112(d)(6).
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• In the residual risk review, cancer risks were calculated using EPA's Integrated Risk
Information System (IRIS) unit risk estimate (URE) for ethylene oxide and additional
standards were imposed in the 2020 MON final rule because the risks were unacceptable
based on that analysis.
• Language was also included in the 2020 MON final rule that indicated that "the EPA remains
open to new and updated scientific information, as well as new dose response values such
as the TCEQ value, as they become available" (85 FR 49098); however, by the close of the
public comment period (March 19, 2020), the TCEQ dose-response value had not yet been
finalized and could not be considered in the final action.
• Subsequently, EPA received and granted petitions for reconsideration of two issues,
specifically, on (1) the use of EPA's IRIS value for ethylene oxide in assessing cancer risk for
the source category, and (2) the use of the TCEQ risk value for ethylene oxide as an
alternative risk value to EPA's IRIS value for purposes of evaluating risk under CAA section
112(f)(2).
• EPA responded to petitioners in June 2021 that reconsideration would be granted. On
February 4, 2022, EPA published a proposed rule to reconsider the 2020 MON final rule and
to request public comment on these issues. EPA held a public hearing on February 22, 2022
and took public comment through March 24, 2022.
FOR MORE INFORMATION
• Interested parties can download a copy of the proposed rule notice from EPA's website at
https://www.epa.gov/stationarv-sources-air~pollution/miscellaneous~organic~chemical~
manufacturing-national-emission.
• Today's action and other background information are also available electronically at
https://www.regulations.gov/, EPA's electronic public docket and comment system.
• For additional technical information about the rule, contact Susan Paret at the EPA's Office
of Air Quality Planning and Standards, at (919) 541-5516 or at paret.susan@epa.gov
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