Final Amendments to Air Toxics Standards for Miscellaneous Organic Chemical
Manufacturing: Fact Sheet

ACTION

•	On May 29, 2020, the U.S. Environmental Protection Agency (EPA) finalized amendments
to the 2003 Miscellaneous Organic Chemical Manufacturing National Emission Standards
for Hazardous Air Pollutants (NESHAP), known as MON.

•	This action primarily applies to miscellaneous specialty chemical production and includes
the following emission sources: process vents, storage tanks, equipment leaks,
wastewater streams, transfer racks and heat exchange systems.

•	Following a residual risk and technology review conducted under the Clean Air Act (CAA),
EPA is finalizing:

o correcting and clarifying regulatory provisions related to emissions during periods of
startup, shutdown and malfunction (SSM), including eliminating exemptions during
periods of SSM and finalizing alternative work practice standards for certain SSM
events including for pressure relief device releases, visible emissions from flares
operating above their smokeless capacity and storage vessel degassing operations;
o adding requirements for ethylene oxide emissions from storage tanks, process vents
and equipment leaks under the risk review given that residual risk was determined to
be unacceptable;

o strengthening requirements for heat exchange systems and equipment leaks under

the technology review;
o adding monitoring and operational requirements for flares that control ethylene
oxide emissions and flares used to control emissions from processes that produce
olefins and polyolefins, and also allowing facilities outside of this subset to opt into
these flare requirements in lieu of complying with the current flare standards; and
o requiring facilities to submit electronic copies of notification of compliance status
reports and submit electronic copies of performance test results and reports.

•	EPA estimates the finalized amendments will achieve hazardous air pollutant (HAP)
emission reductions of 107 tons per year, which includes reductions in ethylene oxide
emissions of approximately 0.76 tons per year.

•	EPA also estimates that excess emissions of HAP from flares will be reduced by
approximately another 260 tons per year.

RESIDUAL RISK ASSESSMENT

•	The CAA requires EPA to assess the risk remaining after application of the final air toxics
standards. This is known as a residual risk assessment.

•	Based on the completed risk assessment, available health information and associated
uncertainties, EPA determined risks from the Miscellaneous Organic Chemical
Manufacturing source category to be unacceptable.

o At the current level of control required by the standard, the maximum individual
cancer risk for inhalation is estimated to be 400-in-l million (based on actual

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emissions) and 800-in-l million (based on allowable emissions) for the Miscellaneous
Organic Chemical Manufacturing source category driven by ethylene oxide emissions
from storage tanks, process vents and equipment leaks.

•	The agency is finalizing requirements for storage tanks, process vents and equipment
leaks with emissions of ethylene oxide and concludes that these controls will reduce
cancer risks to an acceptable level that also achieves an ample margin of safety to
protect public health.

TECHNOLOGY REVIEW

•	The CAA also requires EPA to assess, review and revise the air toxics standards as
necessary, taking into account developments in practices, processes and control
technologies since the standards were first issued.

•	The technology assessment identified cost-effective developments in practices, processes
and control technologies for heat exchange systems and equipment leaks and we are
finalizing amendments under the technology review to control these emission sources
further.

BACKGROUND

•	The CAA requires EPA to regulate HAP, also known as air toxics, from categories of
industrial facilities in two phases.

•	The first phase is "technology-based," where EPA develops standards for controlling the
emissions of air toxics from sources in an industry group (or "source category"). These
maximum achievable control technology (MACT) standards are based on emissions levels
that are already being achieved by the best-controlled and lower-emitting sources in an
industry.

•	Within 8 years of setting MACT standards, the CAA directs EPA to assess the remaining
health risks from each source category to determine whether the MACT standards
protect public health with an ample margin of safety and protect against adverse
environmental effects. This second phase is a "risk-based" approach called residual risk.
Here, EPA must determine whether more health-protective standards are necessary.

•	Also, every 8 years after setting MACT standards, the CAA requires that EPA review and
revise the standards, if necessary, to account for improvements in air pollution controls
and/or prevention.

FOR MORE INFORMATION

•	To download a copy of the final rule notice, go to EPA's website at the following address:
https://www.epa.gov/stationary-sources-air-pollution/miscellaneous-organic-chemical-
manufacturing-national-emission.

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