o
SB?
| V\l7y I U.S. ENVIRONMENTAL PROTECTION AGENCY
\OFFICE OF INSPECTOR GENERAL
Improving air quality
EPA Should Conduct New
Residual Risk and Technology
Reviews for Chloroprene-
and Ethylene Oxide-Emitting
Source Categories to Protect
Human Health
Report No. 21-P-0129	May 6, 2021

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Report Contributors:
Bao Chuong
Gaida Mahgoub
Andrew Lavenburg
Julie Narimatsu
Renee McGhee-Lenart
Abbreviations
|ig/m3
microgram per cubic meter
CAA
Clean Air Act
C.F.R.
Code of Federal Regulations
EPA
U.S. Environmental Protection Agency
Fed. Reg.
Federal Register
GACT
Generally Available Control Technology
HAP
Hazardous Air Pollutant
IRIS
Integrated Risk Information System
MACT
Maximum Achievable Control Technology
NATA
National Air Toxics Assessment
NESHAP
National Emission Standards for Hazardous Air Pollutants
OAQPS
Office of Air Quality Planning and Standards
OIG
Office of Inspector General
RTR
Residual Risk and Technology Review
LIRE
Unit Risk Estimate
U.S.C.
United States Code
Cover Image: The EPA should conduct new residual risk and technology reviews to address
ethylene oxide and chloroprene emissions from various types of stationary
sources. (EPA OIG image)
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U.S. Environmental Protection Agency
Office of Inspector General
At a Glance
21-P-0129
May 6, 2021
Why We Did This Audit
We conducted this audit to
determine whether the
U.S. Environmental Protection
Agency's residual risk and
technology review, known as
RTR, process has sufficiently
identified and addressed any
elevated cancer risks from air
toxics emitted by facilities.
The Clean Air Act requires the
EPA to conduct residual risk
reviews to assess the health
and environmental risks that
remain after implementation of
technology standards limiting
air toxics emissions. If health
risks are determined to be
unacceptable, the EPA is
required to revise the standards
to reduce the risks. Separately,
the EPA is required to review
each of the technology-based
standards at least every eight
years and, if necessary, revise
them, considering
developments in practices,
processes, and control
technologies. The EPA calls
this the technology review.
For efficiency, the EPA
combines RTRs in the same
regulatory package.
This audit addresses the
following:
• Improving air quality.
This audit addresses a top EPA
management challenge:
• Integrating and leading
environmental justice.
Address inquiries to our public
affairs office at (202) 566-2391 or
OIG WEBCOMMENTS@epa.gov.
List of OIG reports.
EPA Should Conduct New Residual Risk and Technology
Reviews for Chloroprene- and Ethylene Oxide-Emitting
Source Categories to Protect Human Health
What We Found
Results from the EPA's modeling and
monitoring efforts indicate that people in
some areas of the country may be exposed
to unacceptable health risks from
chloroprene and ethylene oxide emissions.
Despite the EPA classifying chloroprene as
a likely human carcinogen in 2010 and
The EPA should conduct new
RTRs for chloroprene- and
ethylene oxide-emitting source
categories to address elevated
individual lifetime cancer risks
impacting over 464,000 people, as
found in a modeling tool, and to
achieve environmental justice.
ethylene oxide a carcinogen in 2016, the
EPA has not conducted new RTRs for most types of industrial sources, referred
to as source categories, that emit chloroprene or ethylene oxide. The EPA
should take the following steps to ensure its RTR process sufficiently identifies
and addresses these emissions:
•	Conduct new residual risk reviews for four major source categories that emit
chloroprene or ethylene oxide using new risk values for these pollutants.
•	Conduct a residual risk review for the hospital sterilizers area source
category using the new risk value for ethylene oxide.
•	Conduct overdue technology reviews for four source categories.
•	Develop new National Emission Standards for Hazardous Air Pollutants, or
NESHAPs, for chemical plant area sources that emit ethylene oxide.
•	Develop a process to initiate timely reviews of existing and uncontrolled
emission sources when new or updated risk information becomes available.
New RTRs should be conducted because the EPA issued new risk values for
chloroprene and ethylene oxide in 2010 and 2016, respectively, to reflect their
potent carcinogenicity, as found in newer scientific evidence. The EPA should
exercise its discretionary authority to conduct new residual risk reviews under the
Clean Air Act whenever new data or information indicates an air pollutant is more
toxic than previously determined. Use of such discretionary authority is consistent
with the Agency's position, stated in its April 2006 commercial sterilizer RTR rule.
Recommendations and Planned Agency Corrective Actions
We recommend that the assistant administrator for Air and Radiation (1) develop
and implement an internal control process with specific criteria to determine
whether and when new residual risk reviews of existing NESHAPs and
uncontrolled emission sources are needed to incorporate new risk information;
(2) conduct new residual risk reviews for Group I polymers and resins, synthetic
organic chemical manufacturing industry, polyether polyols, commercial
sterilizers, and hospital sterilizers; (3) revise the NESHAP for chemical
manufacturing area sources to regulate ethylene oxide and conduct a residual
risk review; and (4) conduct overdue technology reviews for the source
categories listed in Recommendations 2 and 3. Recommendations 1, 2, and 3
are unresolved. Recommendation 4 is resolved with corrective actions pending.

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
THE INSPECTOR GENERAL
May 6, 2021
MEMORANDUM
SUBJECT: EPA Should Conduct New Residual Risk and Technology Reviews for Chloroprene- and
Ethylene Oxide-Emitting Source Categories to Protect Human Health
Report No. 21-P-0129
This is our report on the subject audit conducted by the Office of Inspector General of the
U.S. Environmental Protection Agency. The project number for this audit was OA&E-FY19-0091. This
report contains findings that describe the problems the OIG has identified and corrective actions the OIG
recommends. Final determinations on matters in this report will be made by EPA managers in accordance
with established audit resolution procedures.
The Office of Air and Radiation is responsible for the issues discussed in this report.
In accordance with EPA Manual 2750, your office provided acceptable planned corrective actions and
estimated milestone dates for Recommendation 4. This recommendation is resolved with corrective
actions pending.
Action Required
Recommendations 1, 2, and 3 are unresolved. The resolution process, as described in the EPA's Audit
Management Procedures, begins immediately with the issuance of this report. Furthermore, we request a
written response to the final report within 60 days of this memorandum. Your response will be posted on
the OIG's website, along with our memorandum commenting on your response. Your response should be
provided as an Adobe PDF file that complies with the accessibility requirements of Section 508 of the
Rehabilitation Act of 1973, as amended. The final response should not contain data that you do not want
to be released to the public; if your response contains such data, you should identify the data for redaction
or removal along with corresponding justification.
FROM: Sean W. O'Donnell
TO:
Joseph Goffman, Acting Assistant Administrator
Office of Air and Radiation
We will post this report to our website at www.epa.gov/oig.

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EPA Should Conduct New Residual Risk and Technology
Reviews for Chloroprene- and Ethylene Oxide-Emitting
Source Categories to Protect Human Health
21-P-0129
Table of C
Chapters
1	Introduction		1
Purpose		1
Background		1
Responsible Office		11
Scope and Methodology		11
Prior OIG Reports		13
2	EPA Should Conduct New RTRs for Source Categories That Emit
Chloroprene or Ethylene Oxide or Both to Ensure Protection
of Human Health		14
Modeling and Monitoring Results Indicate Elevated Cancer Risks
from Chloroprene and Ethylene Oxide Emissions		14
EPA Should Ensure RTR Process Sufficiently Identifies
and Addresses Elevated Cancer Risks from Chloroprene
and Ethylene Oxide Emissions		21
Environmental Justice May Not Be Achieved Without New RTRs or
Emission Standards		25
Conclusions		26
Recommendations		26
Agency Response and OIG Assessment		27
Status of Recommendations and Potential Monetary Benefits		29
Appendices
A Residual Risk Review Status of Source Categories with
MACT Standards	 30
B Comparison of Residual Risk Review and Technology Review	 31
C Ethylene Oxide Facilities That EPA Identified as Contributing to
Cancer Risks Equal to or Greater Than 100 in One Million in
2014 NATA Interim Work Files at Census Block Level
but Not at Census Tract Level	 32
D Agency Response to Draft Report	 34
E Distribution	 38

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Chapter 1
Introduction
Purpose
The Office of Inspector General for the
U.S. Environmental Protection Agency
conducted this audit to determine
whether the EPA's residual risk and
technology review, or RTR, process has
sufficiently identified and addressed
any elevated cancer risks from air
toxics emitted by facilities.
Background
Hazardous air pollutants, known as HAPs, are those air pollutants known or
suspected to cause cancer or other serious health effects—such as reproductive
effects or birth defects—or adverse environmental effects. HAPs are also known
as toxic air pollutants or air toxics. The Clean Air Act, known as the CAA,
Amendments of 1990 established a list of 189 air toxics that the EPA is required
to regulate. Since 1990, the EPA has revised the list slightly to regulate 187 air
toxics.1
According to the EPA, most air toxics originate from human-made sources, both
stationary and mobile. A stationary source is any building, structure, facility, or
installation that emits or may emit any air pollutant. Stationary sources are further
divided into two groups: major and area sources. Table 1 provides descriptions
of the sources of air toxics.
Table 1: Definitions of stationary and mobile sources of air toxics emissions
Source
Description
Stationary
major
Stationary sources that emit or have the potential to emit ten tons or more per year of any of the
listed toxic air pollutants or 25 tons or more per year of a combination of listed air toxics.
Stationary
area
Stationary sources that emit or have the potential to emit less than ten tons per year of a single listed
toxic air pollutant and less than 25 tons per year of a combination of air toxics.
Mobile
Pollution sources that move. They include vehicles and motorized equipment that produce exhaust
and evaporative emissions.
Source: OIG summary of CAA and information from the EPA. (EPA OIG table)
1 On June 18, 2020, the EPA granted petitions to add 1-bromopropane to the list of air toxics contained in the CAA.
The EPA stated in the petition grant that it will take a separate regulatory action to add 1-bromopropane to the list of
air toxics under CAA § 112(b)(1). Once this separate regulatory action is completed, the number of listed air toxics
will be 188.
Top Management Challenge
This audit addresses the following top
management challenge for the Agency, as
identified in OIG Report No. 20-N-0231. EPA's
FYs 2020-2021 Top Management Challenges,
issued July 21, 2020:
• Integrating and leading environmental
justice.
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Two-Stage Regulatory Process to Control Air Toxics Emissions from
Stationary Sources
Section 112 of the CAA outlines a two-stage regulatory process for addressing air
toxics emissions from stationary sources. In the first stage, the EPA is required to
promulgate technology-based National Emission Standards for Hazardous Air
Pollutants, or NESHAPs, for categories of sources. For major sources, the EPA
must promulgate maximum achievable control technology, or MACT,
standards. MACT standards reflect, at a minimum, the level of emissions that the
best performing 12 percent of sources in the category were achieving in practice.
For area sources, the CAA gives the EPA discretion to set standards that are based
on generally available control technologies or management practices, or GACT
standards, in lieu of MACT standards. The CAA outlines a series of deadlines and
the number of source categories for which MACT or GACT standards are to be
promulgated, with the last of them to be promulgated by November 15, 2000. The
EPA has promulgated these standards, as required under the first stage of the
process, for almost all source categories. Figure 1 is a schematic of the two-stage
regulatory process.
Figure 1: Schematic of the two-stage regulatory process for addressing air toxics emissions
from stationary sources (major and area sources)
Stage 1: Promulgation of Technology-Based Standards
Major Source
Area Source
\
i / \
MACT standards MACT standards / or ^^ACT standard^






Stage 2:
Residual Risk Review

j Residual risk review j j Residual risk review j
\
[ l
d
I i
If necessary, If necessary,
revise standards. revise standards.

Source: OIG summary of the EPA's two-stage regulatory process for addressing air toxics
emissions from stationary sources. (EPA OIG image)
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For NESHAPs that require MACT standards, Section 112(f)(2) requires the EPA
to complete the second stage of the regulatory process, known as the residual
risk review, within eight years of promulgation of the MACT standard. In the
residual risk review, the EPA is required to assess the health and environmental
risks that remain after implementation of the MACT standards. The EPA has not
completed the second stage—that is, residual risk review—of the two-stage
regulatory process for all source categories. Residual risk reviews are still needed
for 21 of 119 source categories with MACT standards. Appendix A provides
more details on the status of the residual risk reviews for source categories with
MACT standards. The CAA does not require the EPA to conduct residual risk
reviews for area source categories subject to GACT standards.
The EPA bases its approach to the residual risk review on the CAA, which
incorporates the approach used to develop the 1989 Benzene NESHAP.2 This
approach is a two-step process, as follows, intended to protect human health with
an ample margin of safety:
1.	In the first step, the EPA determines whether risks are acceptable. If risks
are unacceptable, the EPA must determine the emission standards
necessary to reduce risk to an acceptable level without considering costs.
A maximum individual risk level of less than 100 in one million is
generally considered acceptable, but the overall determination of risk
acceptability is also dependent on other health measures and factors,
including the chronic and acute noncancer risks, number of people
exposed at various risk levels, and uncertainties.3
2.	In the second step, the EPA considers whether the emission standards
provide an ample margin of safety to protect public health, taking into
consideration health information, including the number of people subject
to risk levels higher than one in one million, and other relevant
information, such as technological feasibility, costs, and economic
impacts. In this step, the EPA strives to protect the greatest number of
people possible to a maximum individual risk level no higher than
approximately one in one million.
Figure 2 shows the decision-making process that the EPA uses to address residual
risk to public health from inhaling carcinogens. After conducting the ample-
margin-of-safety analysis, the EPA considers whether a more stringent emission
standard is necessary to prevent an adverse environmental effect, taking into
consideration safety, costs, energy, and other relevant factors.
2	"National Emission Standards for Hazardous Air Pollutants; Benzene Emissions from Maleic Anhydride Plants,
Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery
Plants," 54 Fed. Reg. 38044 (September 14, 1989). See also CAA § 112(f)(2)(B), 42 U.S.C. § 7412(f)(2)(B).
3	Maximum individual risk or maximum individual lifetime cancer risk is the estimated cancer risk if an individual
were continuously exposed to the maximum level of a pollutant for a lifetime of 70 years.
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Separately, under Section 112(d)(6), the EPA must also review each of the
technology-based standards at least every eight years and, if necessary, revise
them, taking into account developments in practices, processes, and control
technologies. The EPA calls this the technology review. Based on the results of
the residual risk review, the technology review, or both, the EPA revises the
NESHAP or determines that revisions are not necessary. For efficiency, the EPA
combines the residual risk review and the first required technology review in the
same regulatory package and calls the rulemaking the RTR. Appendix B provides
a comparison of residual risk reviews and technology reviews.
Figure 2: EPA decision-making process for addressing residual risk for carcinogens
in the Agency's regulatory program
Maximum
individual	EPA decision-making process
cancer risk
"Ample margin of safety" is met. No additional action is
needed.
~N

Costs, technical feasibility, and other factors are considered
in determining whether additional actions are needed.
Risk level is generally not considered sufficiently protective
of public health, and additional actions are needed to
reduce elevated cancer risk.
™\

Source: OIG summary of information from the EPA. (EPA OIG image)
Note: A maximum individual risk level of less than 100 in one million is generally considered
acceptable, but the overall determination of risk acceptability and ample margin of safety are
also dependent on other health measures and factors, including the chronic and acute non-
cancer risks, number of people exposed at various risk levels, and uncertainties.
Air Toxics Driving Cancer Risks
The EPA periodically conducts the National Air Toxics Assessment, known as
NATA, to assess the public health risk from exposure to air toxics. NATA is not
required by regulation. The results of the NATA are not used to set regulatory
standards for sources of air toxics emissions, as would the results of assessments
conducted in the RTR program. NATA is a screening tool that can assist the EPA
and state, local, and tribal air agencies in identifying geographic areas, pollutants,
or emission sources for further examination.
The EPA's latest NATA—that is, the 2014 NATA, which was based on
2014 emissions data and was published on August 22, 2018—estimated that more
than 472,000 people lived in 106 census tracts where the individual lifetime
cancer risk was elevated or equal to or greater than 100 in one million.
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Census tracts are small, relatively permanent statistical subdivisions of a county
with boundaries that normally follow visible features, such as roads and rivers.
Figure 3 is a map showing what census tracts look like. The U.S. Census Bureau
designs census tracts with a goal that each tract contains about 4,000 people and
1,600 housing units. The elevated cancer risks in these 106 census tracts were
driven by ethylene oxide, chloroprene, and coke oven emissions, with the risks in
the majority of the census tracts driven by ethylene oxide emissions. These
106 census tracts are located in 19 metropolitan areas.
Figure 3: Map showing census tracts in the Willowbrook, Illinois area with red numbers
representing the census tract numbers and pink lines representing the census tract
boundaries from the 2010 census
Source: U.S. Census Bureau. (U.S. Census Bureau image)
Each census tract is made up of at least one block group, which is a statistical
division of census tracts. A block group consists of clusters of blocks covering a
contiguous area within the same census tract. Census blocks represent smaller
statistical areas bounded by visible features, such as roads and streams, and by
nonvisible boundaries, such as property lines. A block is the smallest geographic
unit for which the U.S. Census Bureau tabulates decennial census data. Figure 4 is
a map showing what census blocks look like.
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Figure 4: Map showing census blocks in Tract 4703 in Verona, Missouri, with pink numbers
representing census block numbers and pink lines representing census block boundaries
from the 2010 census
Chloroprene
Chloroprene is a chemical used in the production of a class of synthetic rubber
called "neoprene." Neoprene is used to make a variety of products, including
wetsuits, gaskets, hoses, and adhesives. The EPA classifies chloroprene as a likely
human carcinogen, which means there is sufficient evidence to conclude that a
chemical is suspected to be carcinogenic to humans.

Short-Term Effects

of Chloroprene Exposure
•
Headaches.
•
Irritability.
•
Dizziness.
•
Rapid heartbeat.
•
Gastrointestinal disorders.
•
Dermatitis.
•
Temporary hair loss.
•
Corneal damage.
•
Negative effects on lungs, liver,

kidneys, and immune system.

Long-Term Effects

of Chloroprene Exposure
•
Cancer.
•
Respiratory, eye, and skin irritation.
•
Chest pains.
•
Temporary hair loss.
•
Dizziness.
•
Headaches.
•
Fatigue.
•
Rapid heartbeat and reduced blood

pressure.
•
Changes in blood cell parameters.
EPA Standards Used to Control Chloroprene Emissions
The Denka facility in LaPlace, Louisiana, is the only facility in the United States
that produces chloroprene. Denka is subject to the following NESHAPs that
regulate chloroprene emissions:
• Synthetic organic chemical manufacturing industry, outlined in 40 C.F.R.
Part 63, Subparts F, G, H, and I.
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• Group I polymers and resins, which covers neoprene production, outlined
in 40 C.F.R. Part 63, Subpart U.
The unit at Denka that produces chloroprene is subject to the NESHAP for
synthetic organic chemical manufacturing industry, while the unit at Denka that
makes neoprene is subject to the NESHAP for Group I polymers and resins. Both
units emit chloroprene.4
The EPA conducted the RTR for synthetic organic chemical manufacturing
industry and published the final rule on December 21, 2006.5 The Agency made
no changes to the control requirements in the final rule, but it published technical
amendments designed to clarify provisions of the existing NESHAP and to
provide for effective implementation.
The EPA conducted the RTR for Group I polymers and resins that covered
neoprene production and published the final rule on December 16, 2008.6 Based
on the results of this RTR, the EPA decided not to revise the NESHAP because
air toxics emissions from eight source categories under Group I polymers and
resins did not pose cancer risks equal to or greater than one in one million and
there had been no significant developments in practices, processes, or control
technologies since promulgation of the MACT standards. Furthermore, the air
toxics emitted from neoprene production were not known, probable, or possible
human carcinogens at that time.
EPA Set New Risk Values for Chloroprene
In September 2010, the EPA's Integrated Risk Information System, or IRIS,
program completed a toxicological review of chloroprene. The IRIS program
calculated an adult-based inhalation unit risk estimate, known as a URE, of
3 x 10"4 (microgram per cubic meter, or |ig/m3)"' and determined that the pollutant
was a likely human carcinogen.7 When adjusted to include early-life susceptibility
as part of a default lifetime exposure of 70 years, the chloroprene URE increased
to 5 x 10"4 (iig/m3)"1. At the time that the IRIS program issued a new URE for
chloroprene, the Agency had already completed the RTRs for the two source
categories that apply to chloroprene or neoprene production. A URE provides the
4	According to an EPA inspector, while the majority of Denka's chloroprene emissions come from the chloroprene
and neoprene production units, approximately 1 percent of chloroprene emissions are emitted from the facility's
hydrochloric acid production furnace that is regulated under the hazardous waste combustor MACT standards.
5	"National Emission Standards for Organic Hazardous Air Pollutants from the Synthetic Organic Chemical
Manufacturing Industry," 71 Fed. Reg. 76603, December 21, 2006.
6	"National Emission Standards for Hazardous Air Pollutant Emissions: Group I Polymers and Resins (Polysulfide
Rubber Production, Ethylene Propylene Rubber Production, Butyl Rubber Production, Neoprene Production);
National Emission Standards for Hazardous Air Pollutants for Epoxy Resins Production and Non-Nylon Polyamides
Production; National Emission Standards for Hazardous Air Pollutants for Source Categories: Generic Maximum
Achievable Control Technology Standards (Acetal Resins Production and Hydrogen Fluoride Production) (Risk and
Technology Review)," 73 Fed. Reg. 76220, December 16, 2008.
7	(Microgram per cubic meter)1 or (ng/m3)1 is also referred to as "per microgram per cubic metef' or "per ng/m3".
In this document, we refer to the units as (ng/m3)1.
21-P-0129
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upper-bound excess individual lifetime, assumed to be 70 years, cancer risk
estimated to result from continuous exposure to a single chemical at a
concentration of one microgram per cubic meter in air. The EPA did not become
aware of the impact of the newly developed URE on individual lifetime cancer
risk until it conducted the 2011 NAT A in 2015.
Ethylene Oxide
Ethylene oxide is a flammable colorless gas used to make chemicals to
manufacture a variety of products, including antifreeze, textiles, plastics,
detergents, and adhesives. It is also used to sterilize medical equipment or other
devices that cannot be sterilized by other methods, such as steam, and to fumigate
spices. The EPA classifies ethylene oxide as carcinogenic to humans. Studies
show that breathing air containing elevated ethylene oxide levels over many years
increases the risk of developing lymphoid cancers in males and females and breast
cancer in females.
EPA Standards Used to Control Ethylene Oxide Emissions
According to information from the EPA, the following are the source categories
or types of facilities that can emit ethylene oxide and the corresponding
regulations, if any, that limit the emissions of ethylene oxide:
•	Ethylene oxide-emitting sterilization facilities, also known as commercial
sterilizers (40 C.F.R. Part 63, Subpart O).
•	Miscellaneous organic chemical manufacturing (40 C.F.R. Part 63,
Subpart FFFF).
•	Polyether polyols production (40 C.F.R. Part 63, Subpart PPP).
•	Synthetic organic chemical manufacturing industry (40 C.F.R. Part 63,
Subparts F, G, H, and I).
•	Organic liquids distribution (nongasoline) (40 C.F.R. Part 63,
Subpart EEEE).
•	Hospital sterilizers (40 C.F.R. Part 63, Subpart WWWWW).
•	Chemical plant area sources (No applicable NESHAP).
Table 2 shows the date of the RTR final rule, if applicable, for the source
categories or types of facilities that emit ethylene oxide and whether revisions
were made to the NESHAP as a result of the RTR.
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Table 2: Applicable NESHAPs and RTRs for source categories with facilities that emit ethylene oxide
Facility type
HAP major/
area source
NESHAP (subpart)
Date of RTR
final rule
Revisions made to
NESHAP as a result
of RTR?
Commercial
sterilizers
Major
Ethylene oxide-emitting
sterilization facilities (O)
April 7, 2006
No
Area
Hospital
sterilizers
Area
Hospital ethylene oxide
sterilizers (WWWWW)
N/A a
N/A
Chemical
plants
Major
Synthetic organic chemical
manufacturing industry
(F, G, H, and I)b
December 21, 2006 c
No d
Miscellaneous organic
chemical manufacturing
(FFFF)
August 12, 2020 e f
Yes
Polyether polyols production
(PPP)
March 27, 2014 a
Yes h
Organic liquids distribution
(nongasoline) (EEEE)'
July 7, 2020 f.i
Yes
Area
N/A
N/A
N/A
Source: OIG analysis based on review of NESHAPs and information from the EPA. (EPA OIG table)
a Although the EPA is not required to conduct a residual risk review for area sources subject to GACT
standards, it is required to conduct a technology review for these sources every eight years. The technology
review for hospital ethylene oxide sterilizers was due on December 28, 2015.
b The synthetic organic chemical manufacturing industry NESHAP is also applicable to Denka, which emits
chloroprene.
c "National Emission Standards for Organic Hazardous Air Pollutants from the Synthetic Organic Chemical
Manufacturing Industry," 71 Fed. Reg. 76603 (December 21, 2006).
d Although no changes to the control requirements were made, the EPA published technical amendments
designed to clarify provisions of the existing rule and provide for effective implementation.
e "National Emission Standards for Hazardous Air Pollutants: Miscellaneous Organic Chemical Manufacturing
Residual Risk and Technology Review," 85 Fed. Reg. 49084 (August 12, 2020).
f With the exception of the RTRs for miscellaneous organic chemical manufacturing and organic liquids
distribution (nongasoline) source categories, RTRs for other source categories were conducted prior to the
IRIS program's issuance of a revised URE for ethylene oxide and any changes made to those NESHAPs were
not due to ethylene oxide.
g "National Emission Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins; Pesticide
Active Ingredient Production; and Polyether Polyols Production," 79 Fed. Reg. 17340 (March 27, 2014).
h The EPA made revisions in three areas. First, it eliminated the exemption for periods of startup, shutdown,
and malfunction. Second, it required electronic reporting of performance test results. Finally, it required
monitoring of pressure relief devices in organic HAP service that release to the atmosphere.
' Subpart EEEE applies to two types of facilities: (a) chemical plants with a distribution terminal not subject to
another major source NESHAP or that have a few miscellaneous storage tanks or transfer racks that are not
otherwise subject to another major source NESHAP and (b) petrochemical terminals primarily in the business
of storing and distributing organic liquids.
1 "National Emission Standards for Hazardous Air Pollutants: Organic Liquids Distribution (Nongasoline)
Residual Risk and Technology Review," 85 Fed. Reg. 40740 (July 7, 2020).
EPA Updated Risk Values for Ethylene Oxide
In December 2016, the EPA IRIS program completed an evaluation of the
inhalation carcinogenicity of ethylene oxide. It found ethylene oxide to be more
carcinogenic, changing its cancer descriptor from "probably carcinogenic to
humans" to "carcinogenic to humans." The IRIS program also changed ethylene
oxide's adult-based inhalation URE from 0.0001 (iig/m3)"1 to 0.003 (iig/m3)"1.
When adjusted to include early-life susceptibility as part of a default lifetime
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exposure of 70 years, the updated URE of 0.005 (|ig/m3)"' is approximately
57 times greater than the 8.8 x 10"5 (iig/m3)"1 value, which was based on animal
data, used previously by the EPA in its risk assessments. At the time that the EPA
issued a revised URE for ethylene oxide in December 2016, the Agency had
already conducted RTRs for commercial sterilizers, synthetic organic chemical
manufacturing industry, and polyether polyols production in April 2006,
December 2006, and March 2014, respectively.
Two-Pronged Strategy to Address Ethylene Oxide Emissions
In 2018, the EPA developed a two-pronged approach to address ethylene oxide
emissions. The approach consists of (1) reviewing existing regulations and
(2) gathering information to inform regulatory efforts and determine whether
more immediate reduction steps are necessary in any particular location. With
regard to the first prong of the two-pronged strategy, the EPA has:
•	Promulgated the final RTR rules for the organic liquids distribution
(nongasoline) and miscellaneous organic chemical manufacturing source
categories on July 7, 2020, and August 12, 2020, respectively, both of
which incorporated the revised URE for ethylene oxide.
•	Issued an advance notice of proposed rulemaking for the commercial
sterilizers source category technology review on December 12, 2019,8 but
has not scheduled technology reviews for the synthetic organic chemical
manufacturing industry and hospital sterilizers source categories.
With regard to the second prong, the EPA gathered information to inform the
recent RTR rulemaking for the miscellaneous organic chemical manufacturing
source category and the upcoming commercial sterilizers technology review.
EPA's Mission
The EPA's mission is to protect human health and the environment. The Agency
achieves its mission in part by ensuring that:
•	U.S. residents have clean air, land, and water.
•	National efforts to reduce environmental risks, including those that impact
human health, are based on the best available scientific information.
8 84 Fed. Reg. 67889, December 12, 2019.
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EPA's Commitment to Environmental Justice
Signed on February 11, 1994, Executive Order 12898 requires that each federal
agency:
[M]ake achieving environmental justice part of its mission by
identifying and addressing, as appropriate, disproportionately high
and adverse human health or environmental effects of its programs,
policies, and activities on minority populations and low-income
populations in the United States.
On June 30, 2020, the EPA administrator reaffirmed the Agency's commitment to
environmental justice in a press release announcing funding for environmental
justice small grants, stating that "[rjegardless of zip code, the EPA works day in
and day out to provide clean air, clean water, and clean land to all Americans."9
The EPA defines environmental justice as "the fair treatment and meaningful
involvement of all people regardless of race, color, national origin, or income, with
respect to the development, implementation, and enforcement of environmental
laws, regulations, and policies." According to the EPA, fair treatment "means no
group of people should bear a disproportionate share of the negative environmental
consequences resulting from industrial, governmental and commercial operations
or policies." Integration of environmental justice principles into all EPA programs
and across all regions is necessary to achieve environmental equity across all
communities.
Responsible Office
The EPA's Office of Air Quality Planning and Standards, known as OAQPS,
within the Office of Air and Radiation, conducts RTRs and periodic NATAs.
OAQPS works with regional offices and states to ensure the accuracy of the
emissions data used in conducting NATAs and also coordinates the release of
NAT A results with them.
Scope and Methodology
We conducted our work from February 2019 to January 2021. We conducted this
performance audit in accordance with generally accepted government auditing
standards. Those standards require that we plan and perform the audit to obtain
sufficient, appropriate evidence to provide a reasonable basis for our findings and
conclusions based on our objectives. We believe that the evidence obtained
provides a reasonable basis for our findings and conclusions based on our
objectives.
9 EPA, "EPA Releases Additional Funding for 2020 Environmental Justice Small Grants," News Release. June 30,
2020.
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To understand how the EPA addresses air toxics, including the RTR process, we
interviewed OAQPS personnel. We also reviewed the EPA's website on RTR of
the NESHAP and the following statutes, policies, guidance, and documents:
•	CAA, as amended.
•	Residual Risk Report to Congress, March 1999.
•	Scientific Advisory Board Review of the EPA's draft Risk and Technology
Review (RTR) Risk Assessment Methodologies: For Review by the EPA 's
Science Advisory Board with Case Studies - MACTI Petroleum Refining
Sources and Portland Cement Manufacturing.
•	Screening Methodologies to Support Risk and Technology Reviews (RTR):
A Case Study Analysis, May 2017.
•	CAA Section 112 Risk and Technology Reviews: Statutory Authority and
Methodology, December 14, 2017.
We limited our audit to RTRs conducted for the source categories that emit
chloroprene or ethylene oxide, since the 2014 NATA found these pollutants
contributed to the majority of the individual lifetime cancer risks in census tracts
with the highest individual lifetime cancer risks greater than 100 in one million.
The source categories are:
•	Group I polymers and resins, focusing on neoprene production.
•	Commercial sterilizers.
•	Synthetic organic chemical manufacturing industry.
•	Polyether polyols production.
•	Miscellaneous organic chemical manufacturing.
•	Organic liquids distribution (nongasoline).
We reviewed the proposed and final rulemakings for these RTRs, including the
residual risk assessments. Because our scope comprises only source categories
that emit chloroprene, ethylene oxide, or both, we are not commenting on the
adequacy of other NESHAPs not reviewed as part of this audit.
We also reviewed the EPA's two-pronged strategy to address ethylene oxide
emissions. We assessed whether the EPA has sufficiently addressed ethylene
oxide emissions from other source categories or types of facilities not required to
have residual risk reviews, such as hospital sterilizers, or that lack NESHAPs,
such as chemical plant area sources that emit ethylene oxide.
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Prior OIG Reports
EPA OIG Report No. 08-P-0020. Improvements in Air Toxics Emissions Data
Needed to Conduct Residual Risk Assessments, issued October 31, 2007, found
that the reliability of National Emissions Inventory data for site-specific emissions
varied considerably, but the EPA had not established objectives to define an
acceptable level of quality for National Emissions Inventory data used in the
residual risk assessments. The OIG recommended that the EPA develop data
quality objectives for using the National Emissions Inventory data in conducting
residual risk assessments and establish requirements for state reporting of air
toxics emissions data and compliance-monitoring information. The EPA
disagreed with the recommendations, but according to the Agency, it completed
the recommendations in 2013.
EPA OIG Report No. 20-N-0128. Management Alert: Prompt Action Needed to
Inform Residents Living Near Ethylene Oxide-Emitting Facilities About Health
Concerns and Actions to Address Those Concerns, issued March 31, 2020, found
that, while the EPA or state personnel or both have met with residents living near
nine of the 25 high-priority ethylene oxide-emitting facilities, communities near
16 facilities have yet to be afforded public meetings or other direct outreach to
learn about the health risks and actions being taken to address those risks. The
EPA provided an alternative recommendation with corrective actions that the OIG
did not accept. Subsequently, the recommendation went into audit dispute
resolution, and the EPA administrator sided with the Office of Air and
Radiation's proposed corrective action plan, which committed the EPA to, among
other things, conduct additional, more-refined risk assessments and outreach to
affected communities.
EPA OIG Report No. 21-P-0123. EPA Delayed Risk Communication and Issued
Instructions Hindering Region 5 's Ability to Address Ethylene Oxide Emissions,
issued April 15, 2021, found that the EPA delayed communicating health risks to
residents in Illinois who lived near ethylene oxide-emitting facilities. Further, we
found that the Office of Air and Radiation's senior leaders issued instructions that
hindered Region 5's ability to effectively address ethylene oxide emissions. The
Agency's response to the draft report stated that the Agency's air toxics strategy
would address these recommendations. We reviewed the draft air toxics strategy,
and it did not address our concerns. As of May 2021, we consider the two
recommendations unresolved.
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Chapter 2
EPA Should Conduct New RTRs for Source
Categories That Emit Chloroprene or Ethylene Oxide
or Both to Ensure Protection of Human Health
Results from the EPA's modeling and limited monitoring efforts indicate that
there are potentially unacceptable risks from chloroprene and ethylene oxide
emissions in some areas of the country. These results are not unexpected because
the EPA issued a new URE for chloroprene after determining the pollutant was a
likely human carcinogen and a revised URE for ethylene oxide after determining
the pollutant was a human carcinogen. The URE changes occurred after the
Agency had already completed the RTR rulemakings for many of the NESHAPs
that control these emissions. In the absence of new RTRs for the applicable source
categories that use the updated UREs, the Agency cannot provide assurance that
its current NESHAPs are sufficiently protective. We identified five steps that the
EPA should take within its RTR process to provide better assurance that the
Agency is sufficiently identifying and addressing chloroprene and ethylene oxide
emissions. These steps would also help the EPA meet its requirement to address
environmental justice for overburdened minority and low-income communities.
Modeling and Monitoring Results Indicate Elevated Cancer Risks from
Chloroprene and Ethylene Oxide Emissions
Elevated cancer risks have been estimated in areas where people are exposed to
emissions of chloroprene, ethylene oxide, or both, according to the:
•	2014 NAT A.
•	Modeling conducted as part of the residual risk review for the
miscellaneous organic chemical manufacturing RTR rulemaking.
•	Chloroprene monitoring data collected in LaPlace, Louisiana, and
ethylene oxide monitoring data collected in Willowbrook, Illinois.
The EPA has stated that none of these sources of information can definitively be
used to characterize the risks from ethylene oxide and chloroprene emissions in
certain areas and that the risk assessments conducted through the RTR process
would be the appropriate process to determine risks from source categories
emitting ethylene oxide and chloroprene. Given that available information
generated by the EPA indicates elevated cancer risks and that the EPA has not
conducted residual risk assessments with current UREs for ethylene oxide or
chloroprene for Group I polymers and resins, synthetic organic chemical
manufacturing industry, polyether polyols production, commercial sterilizers, and
hospital sterilizers, the Agency cannot provide assurance that its current
NESHAPs are sufficiently protective of human health. In addition, according to
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information from the EPA, other emission sources, specifically chemical plant
area sources that emit ethylene oxide, lack applicable NESHAP standards given
that the chemical manufacturing area source NESHAP does not regulate ethylene
oxide emissions.
2014 NAT A Results Indicate Significant Number of People Live in
Areas with Elevated Cancer Risks from Chloroprene and Ethylene
Oxide Emissions
Based on our analysis of the data reported in the 2014 NATA, over 464,000
people live in 103 census tracts located in the 18 metropolitan areas with
individual lifetime cancer risks equal to or greater than 100 in one million where
ethylene oxide or chloroprene are the primary risk drivers, as shown in Figure 5.
According to information from the EPA, the individual lifetime cancer risks in the
census tracts with elevated cancer risks in 17 of these 18 metropolitan areas are
driven by ethylene oxide emissions. The individual lifetime cancer risks in the
census tracts with elevated cancer risks in the remaining metropolitan area are
driven by chloroprene emissions from the Denka facility. While the majority of
the individual lifetime cancer risks for the nearby residents of Denka are primarily
attributed to chloroprene emissions, a significant portion of those risks are also
attributed to ethylene oxide emissions from two nearby chemical plants.
Figure 5: Metropolitan areas in the United States where there is at least one census tract in
which chloroprene or ethylene oxide is the risk driver and the individual lifetime cancer risk
is equal to or greater than 100 in one million (numbers indicate EPA regions)
Source: OIG summary of data from 2014 NATA and other information from the EPA.
(EPA OIG image)
Note: According to the EPA, the New Mexico facility installed a control device that reduced
ethylene oxide emissions prior to the 2014 NATA release.
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Based on the 2014 NATA results, the EPA identified Denka and 22 ethylene
oxide-emitting facilities that contribute to individual lifetime cancer risks equal to
or greater than 100 in one million at the census tract level. The 22 ethylene
oxide-emitting facilities are listed in the OIG's March 31, 2020 management alert
report, along with three census block facilities that the EPA prioritized as
contributing to elevated estimated cancer risks.
In addition, in NATA working files used by the Agency to calculate census tract
risks, the EPA included 29 additional ethylene oxide-emitting facilities where
preliminary data showed individual lifetime cancer risks from these facilities at
the census block level equal to or greater than 100 in one million.10 These
29 ethylene oxide-emitting facilities are listed in Appendix C.
OAQPS told us there was significant uncertainty in the risk estimates for these
facilities when compared to the risks associated with facilities at the census tract
level. The EPA noted in its NATA documentation that NATA results apply best
to larger areas, not specific places, and an OAQPS manager told us that the census
tract level is the spatial scale that the EPA feels most confident in expressing
NATA risk estimates. The Agency stated that more localized studies are often
needed to better characterize local-level risk. However, it has only conducted
additional investigations of risk for nine of these 29 facilities. These additional
investigations suggest that all nine facilities likely contribute to individual lifetime
cancer risks of equal to or greater than 100 in one million. The modeling efforts
indicate that these facilities contribute to elevated cancer risks despite all of them
being subject to NESHAPs that regulate their air toxic emissions. Tables 3 and 4
show the NESHAPs under which these 23 facilities contributing to individual
lifetime cancer risks equal to or greater than 100 in one million at the census tract
level and the 29 facilities at the census block level are regulated. Some of the
chemical plant major sources are regulated under multiple NESHAPs, and as
such, Tables 3 and 4 add up to more than 23 and 29, respectively. Under the
Agency's residual risk review process, a cancer risk equal to or greater than 100
in one million is generally considered unacceptable.
As noted in Chapter 1, the 2014 NATA is a screening tool and there are
uncertainties associated with the census tract level-risks in it. Sources of
uncertainties in NATA are components that predict (1) ambient air
concentrations, such as emissions estimates; (2) exposure, such as activity
patterns; and (3) risk, such as UREs. Block-level data were used to inform the
census tract-level risk estimates, but the EPA has less confidence in the
block-level risk estimates. The EPA's technical support document for the
2014 NATA states, however, that "no scientific statement (in risk assessment or
10 During the process of conducting the 2014 NATA, the EPA also identified five additional ethylene oxide-emitting
facilities that contribute to individual lifetime cancer risks equal to or greater than 100 in one million at the census
block level. Four of the five facilities have closed or no longer use ethylene oxide in their processes. Refined
modeling indicated the fifth facility no longer contributes to elevated cancer risk. These five facilities are not
included in Table 4 or Appendix C.
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other areas of science) can be made with complete confidence. Risk estimates are
always uncertain to some degree."11 It also states "that uncertainty does not
prevent EPA from making a statement of risk, nor does it prevent EPA from
taking reasonable actions."
Nevertheless, the results indicating elevated individual lifetime cancer risks
associated with the facilities in Tables 3 and 4 suggest that the EPA should
conduct new residual risk reviews for these source categories or types of facilities.
Indeed, in the recent August 2020 RTR for the miscellaneous organic chemical
manufacturing source category, the EPA conducted more refined modeling that
confirmed six facilities in Table 3 and nine facilities in Table 4 contributed to
elevated cancer risks.
Table 3: EPA-identified facilities that contribute to individual lifetime cancer risks equal to or greater than 100
in one million at the census tract level based on the 2014 NATA results and the NESHAPs they must meeta



Number of
Number of
Number of



facilities
facilities that
facilities that
Facility type
HAP major/
area source
NESHAP (subpart)
subject to
NESHAP b
emit
chloroprenebc
emit ethylene
oxide b
Commercial
Major
Ethylene oxide-emitting
6
0
11
sterilizers
Area
sterilization facilities (O)
5


Synthetic organic
chemical manufacturing
industry (F, G, H, and I)
5
1
4


Miscellaneous organic
chemical manufacturing
(FFFF)
1
0
1
Chemical
plants2
Major
Polyether polyols
production (PPP)
3
0
3

Organic liquids
distribution
(Nongasoline) (EEEE)d
1e
0
1


Group I polymers and
1
1
0


resins (U)

Area
N/A
5
0
5
Source: OIG summary of information from the EPA and facility permits. (EPA OIG table)
a Elevated individual lifetime cancer risks from six facilities were confirmed with more refined modeling in the
miscellaneous organic chemical manufacturing RTR.
b Some of the chemical plant major sources are subject to more than one NESHAP. As such, the fourth and sixth
columns add up to more than 23.
c Denka is the only facility in the United States that emits chloroprene and is subject to the synthetic organic
chemical manufacturing industry NESHAP and Group I polymers and resins NESHAP.
d Subpart EEEE applies to two types of facilities: (a) chemical plants with a distribution terminal not subject to
another major source NESHAP or that have a few miscellaneous storage tanks or transfer racks that are not
otherwise subject to another major source NESHAP and (b) petrochemical terminals primarily in the business
of storing and distributing organic liquids.
e While a portion of this facility's ethylene oxide emissions are regulated under the organic liquids distribution
(nongasoline) NESHAP, the majority of its ethylene oxide emissions are regulated under the synthetic organic
chemical manufacturing industry NESHAP.
11 EPA, Technical Support Document, EPA's 2014 National Air Toxics Assessment, August 2018.
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Table 4: EPA-identified ethylene oxide-emitting facilities that contribute to individual lifetime cancer risks
equal to or greater than 100 in one million at the census block level during the process of conducting the
2014 NATA and the NESHAPs they must meeta
Facility type
HAP major/
area source
NESHAP (subpart)2
Number of facilities
subject to NESHAPb
Commercial
sterilizers
Major
Ethylene oxide-emitting sterilization facilities (O)
1
Area
5
Hospital
sterilizers
Area
Hospital ethylene oxide sterilizers (WWWWW)
4
Chemical
plants a
Major
Synthetic organic chemical manufacturing industry
(F, G, H, and I)
10
Miscellaneous organic chemical manufacturing (FFFF)
5c
Polyether polyols production (PPP)
5
Organic liquids distribution (Nongasoline) (EEEE)d
2e
Area
N/A
8
Source: OIG summary of information from the EPA and facility permits. (EPA OIG table)
a Elevated individual lifetime cancer risks from nine facilities were confirmed with more refined modeling in the
miscellaneous organic chemical manufacturing RTR.
b Some of the chemical plant major sources are subject to more than one NESHAP standard. As such, the last
column adds up to more than 29.
c While a portion of each of these five facilities' ethylene oxide emissions is regulated under the miscellaneous
organic chemical manufacturing NESHAP, the majority of the facilities' ethylene oxide emissions are regulated
under the synthetic organic chemical manufacturing industry NESHAP or polyether polyols production NESHAP.
d Subpart EEEE applies to two types of facilities: (a) chemical plants with a distribution terminal not subject to
another major source NESHAP or that have a few miscellaneous storage tanks or transfer racks that are not
otherwise subject to another major source NESHAP and (b) petrochemical terminals primarily in the business of
storing and distributing organic liquids.
e While a portion of each of these facilities' ethylene oxide emissions was regulated under the organic liquids
distribution (nongasoline) NESHAP, the majority of their ethylene oxide emissions are regulated under the
synthetic organic chemical manufacturing industry NESHAP and/or polyether polyols production NESHAP.
Residual Risk Review for the Miscellaneous Organic Chemical
Manufacturing Source Category Identified Elevated Cancer Risks
from Chloroprene and Ethylene Oxide Emissions from Three Source
Categories' Processes
Since the release of the 2014 NATA in August 2018, the EPA has performed
more refined modeling through a residual risk review for the miscellaneous
organic chemical manufacturing RTR rulemaking that was finalized on
August 12, 2020. The residual risk review included determining facilitywide
cancer risks from miscellaneous organic chemical manufacturing facilities that
also emitted air toxics from processes regulated under other source category
NESHAP, including Group I polymers and resins; synthetic organic chemical
manufacturing industry; and polyether polyols production processes, if present,
since not all facilities have these processes.
According to the EPA, facilitywide cancer risks in RTR rulemakings are generally
more uncertain because the emissions data for the other source categories may not
have undergone the same level of data quality review as those being assessed in the
regulatory assessment. For the miscellaneous organic chemical manufacturing RTR,
however, the facilitywide cancer risks that were determined likely had fewer
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uncertainties than those determined for other RTR rulemakings. According to
information in the rulemaking docket and information from the EPA, the EPA
communicated with 20 of 24 facilities regulated under the miscellaneous organic
chemical manufacturing NESHAP that emit ethylene oxide about their emissions
and processes to ensure risks were determined accurately. The four facilities that the
EPA did not communicate with during the RTR rule development have facilitywide
cancer risks equal to or less than ten in one million. Based on facility permits,
information from the residual risk review for the miscellaneous organic chemical
manufacturing RTR rulemaking, and other information in the rulemaking docket,
we determined that individual lifetime cancer risks attributed to chloroprene or
ethylene oxide emissions from Group I polymers and resins, synthetic organic
chemical manufacturing industry, and polyether polyols production processes are
likely to be equal to or greater than 100 in one million, suggesting that the existing
NESHAPs for these source categories may not be protective of human health.
Monitoring Data Indicated Elevated Cancer Risks in LaPlace,
Louisiana, and Willowbrook, Illinois
Monitoring data indicate that existing NESHAPs for the synthetic organic
chemical manufacturing industry, which covers chloroprene production; Group I
polymers and resins, which covers neoprene production; and commercial
sterilizers may not be protective of human health. Since May 2016, the EPA has
measured chloroprene concentrations in the air at six different locations near
Denka in LaPlace, Louisiana. Figure 6 shows the EPA-calculated "rolling annual
average" ambient chloroprene concentrations at the six different monitoring
locations, represented by six different color points. A rolling annual average is
calculated by taking the sample results for the 12 months preceding a sampling
day, averaging them, and placing that value as a data point in the figure. With
every subsequent sampling day, those 12 months roll forward to capture the
12 months preceding that day, the results are averaged, and this rolling annual
average is shown as the next data point.
Figure 6: Rolling annual average ambient chloroprene concentrations (|jg/m3) at six sites
near Denka in LaPlace, Louisiana, from 2017 to 2020


-100 in one million cancer risk if
exposed to this concentration
level for a lifetime
Source: EPA-developed image with OIG-inserted line for the 100 in one million cancer risk level if
exposed to an ambient chloroprene concentration level of 0.2 |jg/m3 for a lifetime. (EPA OIG image)
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The rolling annual average ambient chloroprene concentrations at all six
monitoring locations generally decreased after March 2018. This reduction was
the result of Denka voluntarily entering into an administrative order on consent, a
legal agreement, with the Louisiana Department of Environmental Quality. In the
2017 order, Denka agreed to install a series of new control technology and
measures that are not required under NESHAPs for Group I polymers and resins
or synthetic organic chemical manufacturing industry to reduce chloroprene
emissions. The last of the chloroprene emission-control devices became fully
operational in March 2018. Despite Denka's efforts, the annual average ambient
chloroprene concentrations remained above 0.2 |ig/m3 at all six monitoring
locations near Denka at the conclusion of the EPA's community air-monitoring
effort on September 26, 2020. According to the EPA, rolling annual average
ambient chloroprene concentrations in the community would be lower except for
occasional elevated measurements, or spikes, that contribute to the rolling annual
averages. To better understand the magnitude and frequency of occasional, but
recurring, spikes that contribute significantly to the long-term chloroprene
averages, the EPA deployed a Continuous Air Monitoring Program in
March 2020. Data from the Continuous Air Monitoring Program show that spikes
above 0.2 |ig/m3 continued into 2021.
The horizontal red line in Figure 6 delineates the 0.2 |ig/m3 chloroprene
concentration level, which is the concentration that, if exposed to for a lifetime, is
equivalent to a cancer risk of 100 in one million. A cancer risk of 100 in
one million is generally considered unacceptable and would require the EPA to
take action to reduce that risk. In a May 5, 2016 memorandum to Region 6,
OAQPS recommended that Denka aim for emission reductions such that the
maximum annual average chloroprene concentration is no higher than 0.2 |ig/m3
chloroprene at the highest modeled off-site location. The high rolling annual
average ambient chloroprene concentrations since 2017 in Figure 6 indicate that
the existing NESHAPs for Group I polymers and resins and synthetic organic
chemical manufacturing industry may not be protective of human health.
EPA short-term monitoring around the Sterigenics facility in Willowbrook,
Illinois, from November 2018 to March 2019 helped to inform the August 2019
risk assessment that the Agency conducted to assess human health risks posed by
ethylene oxide emissions from the facility. The risk assessment estimated that
risks from lifetime exposure while the facility was operating ranged from less
than 100 in one million to 1,000 in one million in residential areas closest to the
facility.12 For areas where people worked near the facility, the estimated risks
while the facility was operating ranged from 200 in one million to 1,000 in
one million closest to the facility. The risk assessment also estimated that future
risks in residential areas and areas where people work near the facility would be
below 100 in one million and potentially as low as one in one million if the
12 The short-term monitoring was conducted from November 2018 to March 2019.
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facility was more highly controlled. These results indicate that the existing
NESHAP for commercial sterilizers may not be protective of human health.
EPA Should Ensure RTR Process Sufficiently Identifies and
Addresses Elevated Cancer Risks from Chloroprene and Ethylene
Oxide Emissions
Despite indications of elevated cancer risks from chloroprene and ethylene oxide
emissions, the EPA has not incorporated new or revised UREs for chloroprene
and ethylene oxide into the RTR process for many source categories that emit
these pollutants. In the absence of updated reviews for the applicable source
categories, the Agency cannot provide assurance that its current NESHAPs are
protective. There are five steps that the EPA should take to ensure its RTR
process identifies and addresses elevated cancer risks from chloroprene and
ethylene oxide emissions. The five steps are to:
•	Conduct new residual risk reviews for four major source categories:
(1) Group 1 polymers and resins, (2) synthetic organic chemical
manufacturing industry, (3) polyether polyols production, and
(4) commercial sterilizers, since a new risk value for chloroprene was set
for the first time and a higher revised risk value for ethylene oxide was
issued after RTRs had already been conducted for these source categories.
•	Conduct a residual risk review for hospital sterilizers, which are area
sources.
•	Conduct overdue technology reviews for four source categories.
•	Develop emission standards for chemical plant area sources that emit
ethylene oxide, which currently lack applicable NESHAP standards.
•	Develop an internal control process to assure timely reviews of existing
NESHAPs and uncontrolled emission sources when information becomes
available that the risk of a pollutant has increased.
EPA Has Not Scheduled Any New Residual Risk Reviews to Be
Conducted Despite Issuance of New or Revised Higher Risk Values
for Chloroprene and Ethylene Oxide
The EPA's IRIS program issued a new URE for chloroprene for the first time in
September 2010 and a revised URE for ethylene oxide in December 2016 that
demonstrated that these pollutants were more carcinogenic than previously
understood. However, despite chloroprene being classified as a likely human
carcinogen and ethylene oxide as a human carcinogen, the EPA has not issued a
schedule to conduct new residual risk reviews for Group I polymers and resins,
synthetic organic chemical manufacturing industry, polyether polyols production,
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and commercial sterilizers. Residual risk reviews for all these source categories
were conducted prior to the issuance of new or revised UREs for chloroprene and
ethylene oxide.
We asked the Agency whether it was required to conduct new residual risk
reviews for the chloroprene and ethylene oxide source categories. OAQPS
asserted that, "while the CAA does require EPA to conduct a review of a
NESHAP for advancements in technology, it does not require such a review for
advancements related to risk."
In addition, the Agency asserted that it is not obligated to conduct a residual risk
review under any circumstances at issue in the case of Citizens for Pennsylvania's
Future v. Andrew R. Wheeler, No. 19-CV-02004-VC (N.D. Cal. June 26, 2020).
However, the issue before the court in that case was whether the CAA imposes a
mandatory duty on the EPA to conduct a new residual risk review whenever the
Agency revises technology-based standards for a source category. While the
court's analysis may have broader applications, the court did not specifically
address whether the EPA is required to conduct a new residual risk review
whenever there is new risk data or information.
The EPA has discretionary authority to conduct new residual risk reviews under
the CAA whenever new data or information suggests an air pollutant is more
toxic than previously determined. The CAA does not state that the Agency must
or should conduct only one residual risk review for a source category. Further, as
noted by the court in Citizens for Pennsylvania's Future, the CAA "expressly
contemplates that EPA might revise its risk-based standards," citing
CAA § 307(d)(1)(C), which refers to the "promulgation or revision of ... any
standard under section [CAA § 112(f)]" (emphasis added). Section 112(f) of the
CAA authorizes the EPA to promulgate risk-based standards. The Agency also
asserted in its April 2006 commercial sterilizer RTR rule that it has the authority
to revisit and revise rulemakings in light of new information related to risk. In that
rule, the EPA stated:
We [the EPA] have the authority to revisit (and revise, if
necessary) any rulemaking if there is sufficient evidence that
changes within the affected industry or significant improvements
to science suggests the public is exposed to significant increases in
risk as compared to the risk assessment prepared for the
rulemaking (e.g., CAA § 301).
Section 301 of the CAA contains the EPA's authority to issue rules to implement
the CAA. Conducting new residual risk reviews to incorporate the current UREs and
risk information for chloroprene and ethylene oxide would assure that the EPA RTR
process results in new or revised standards that are protective of human health. We
note that, on July 8, 2020, 11 senators urged the EPA to conduct a new RTR for
commercial sterilizers because a revised URE was issued for ethylene oxide since
the Agency last conducted an RTR for the source category in April 2006.
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EPA Has Not Scheduled a Residual Risk Review of Hospital
Sterilizers
The EPA is not required to conduct residual risk reviews of area sources with
GACT standards, and the EPA has not scheduled one for hospital sterilizers.
Given that ethylene oxide has been determined to be more toxic than previously
known, the EPA should conduct a residual risk review for hospital sterilizers to
ensure the protection of human health.
EPA Is Not Meeting Statutory Time Frames for Conducting
Technology Reviews
The Agency has missed deadlines for four technology reviews for four source
categories that emit chloroprene, ethylene oxide, or both, and one is due in 2022,
as shown in Table 5. While the technology review for commercial sterilizers is
being conducted, with an anticipated issuance of the final rule in late 2021 at the
earliest, those for the other three source categories were not planned, as they were
not in the regulatory agenda at the time of this report.
Table 5: Status of technology reviews for source categories that emit chloroprene, ethylene oxide, or both
Facility type
HAP major/
area source
NESHAP (subpart)
Technology review
due date
Technology
review status
Commercial
sterilizers
Major
Area
Ethylene oxide-emitting
sterilization facilities (O)
April 5, 2014 b
Overdue
Hospital
sterilizers
Area
Hospital ethylene oxide sterilizers
(WWWWW)
December 28, 2015
Overdue
Chemical
plants a
Major
Synthetic organic chemical
manufacturing industry
(F, G, H, and I)
December 19, 2014
Overdue
Miscellaneous organic chemical
manufacturing (FFFF)
August 11, 2028°
Not overdue
Polyether polyols production (PPP)
March 25, 2022
Not overdue
Organic liquids distribution
(Nongasoline) (EEEE)d
July 7, 2028 e
Not overdue
Group I polymers and resins (U)
December 16, 2016
Overdue
Area
N/A
N/A
N/A
Source: OIG analysis of CAA and information from the EPA. (EPA OIG table)
a Some of the chemical plant major sources are subject to more than one NESHAP standard.
b The estimated completion date of the technology review is late 2021 at the earliest.
c The EPA recently conducted the RTR for the miscellaneous organic chemical manufacturing source category
for the first time and issued the final rule on August 12, 2020.
d Subpart EEEE applies to two types of facilities: (a) chemical plants with a distribution terminal not subject to
another major source NESHAP or that have a few miscellaneous storage tanks or transfer racks that are not
otherwise subject to another major source NESHAP and (b) petrochemical terminals primarily in the business
of storing and distributing organic liquids.
e The EPA recently conducted the RTR for the organic liquids distribution (nongasoline) source category for the
first time and published the final rule on July 7, 2020.
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According to OAQPS personnel, the Agency has no plans to conduct the overdue
technology review for Group I polymers and resins that covers neoprene
production because it does not want to expend rulemaking resources on a
technology review covering one facility—Denka. Furthermore, the Agency
believed that emission reductions could be achieved more quickly by working with
the state and the facility—as shown in Figure 6, the large emissions reductions
after implementation of the last of the control devices in March 2018—rather than
through rulemaking. The technology review for Group I polymers and resins that
covers neoprene production was conducted in 2008. Section 112(d)(6) of the CAA
requires the EPA to conduct a technology review for each source category at least
every eight years after promulgation of MACT or GACT standards and revise the
standards, if necessary. The CAA does not provide any exceptions for this
requirement. Without revised NESHAP standards developed through another
residual risk or technology review, any new facilities built would only have to
meet the existing standards, which are not protective of human health.
While a technology review for polyether polyols production is not due until
March 2022, we believe that a technology review should be conducted as soon as
practicable in light of the potent carcinogenicity of ethylene oxide, as
demonstrated by the revised URE. The CAA provides the Agency with the
discretion to conduct a technology review sooner than eight years.
The EPA could combine the residual risk reviews with the technology reviews to
conduct new RTRs. This should be done not only to protect human health in a
timely manner but also to promote efficiency.
EPA Has Not Developed Standards for Chemical Plant Area Sources
that Emit Ethylene Oxide
The EPA has not developed standards for chemical plant area sources that emit
ethylene oxide. There is a NESHAP for chemical manufacturing area sources
outlined in 40 C.F.R. Part 63, Subpart VVVVVV. This NESHAP, however,
applies to each chemical manufacturing process unit that uses as feedstock,
generates as byproducts, or produces as products any of 15 air toxics listed in the
rule. Ethylene oxide is not one of the 15 listed air toxics in Subpart VVVVVV.
Therefore, chemical plant area sources may emit ethylene oxide without any
controls. An overdue technology review of Subpart VVVVVV is in the EPA's
long-term regulatory agenda, but the Agency has not affirmed to us that it will
add ethylene oxide to the list of regulated air toxics under Subpart VVVVVV at
the conclusion of the overdue technology review.
EPA Lacks a Process to Assure Timely Reviews of Existing NESHAPs
and Uncontrolled Emission Sources When Pollutant Risk Increases
The EPA does not have a process to assure timely reviews of existing NESHAPs
and uncontrolled emission sources when new or updated risk information becomes
available that demonstrates that a pollutant is more toxic than previously known.
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The IRIS program issued a URE value for chloroprene for the first time in 2010
and an updated, larger URE value for ethylene oxide in 2016, in both circumstances
classifying the chemicals as more carcinogenic than previously known. These
assessments were completed after the Agency had already conducted RTRs for the
Group I polymers and resins, synthetic organic chemical manufacturing industry,
polyether polyols production, and commercial sterilizers.
Although more than ten years have passed since the IRIS program issued a new
URE value for chloroprene, the EPA has not scheduled any regulatory reviews for
Group I polymers and resins and synthetic organic chemical manufacturing
industry, both of which apply to Denka units that emit chloroprene. In addition,
although over four years have passed since the IRIS program issued a revised
URE for ethylene oxide in December 2016, the EPA has yet to schedule
regulatory reviews for synthetic organic chemical manufacturing industry,
polyether polyols production, hospital sterilizers, or chemical plant area sources
that emit ethylene oxide.
By developing and implementing an internal control process, the EPA could assess
the source categories that emit pollutants with new increased risk values to
determine the significance of the resultant risks and the need to initiate and
prioritize timely regulatory reviews of impacted source categories. These actions
would assure that sources emitting air toxics with new increased risk values and
sources of air toxics emissions not previously controlled are being addressed to
protect public health in a timely manner.
Environmental Justice May Not Be Achieved Without New RTRs or
Emission Standards
Minority and low-income populations are disproportionately impacted by
chloroprene and ethylene oxide emissions. According to the EPA's environmental
justice screening tool, EJSCREEN, 100 percent of the people living in the same
census block group where Denka is located are minorities and 49 percent of them
are low-income.13 The LaPlace, Louisiana community is impacted by not only
chloroprene emissions from Denka but also ethylene oxide emissions from two
nearby chemical plants. The burden from exposure to these two toxic chemicals
resulted in the 2014 NATA estimating that these residents have an individual
lifetime cancer risk of 2,000 in one million at the census tract level, which is the
highest in the country.
According to EJSCREEN, 50 percent or more of the people living in the same
census block group as 14 of the 22 ethylene oxide-emitting facilities contributing to
cancer risks of 100 in one million or greater at the census tract level are minorities
or part of low-income households. Further, the same is true of 18 of the 29 ethylene
13 EJSCREEN defines minorities as individuals who list their racial status as a race other than white alone and/or list
their ethnicity as Hispanic or Latino. A household income is defined as low-income when it is less than or equal to
twice the federal "poverty level."
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oxide-emitting facilities contributing to cancer risks of 100 in one million or greater
at the census block level. Unless the EPA conducts new RTRs using the new UREs
for chloroprene and ethylene oxide for source categories that have not had RTRs
using the new UREs or develops emission standards for area source chemical
plants that emit ethylene oxide, the Agency may not meet its commitment and
responsibility under Executive Order 12898 to achieve environmental justice.
Conclusions
Information generated by the EPA indicates elevated cancer risks from
chloroprene and ethylene oxide emissions. The Agency has not incorporated new
risk values for these pollutants into residual risk reviews for most source
categories. Therefore, the EPA cannot assure that current emission standards are
protective of human health. The EPA should exercise its discretionary authority to
conduct new residual risk reviews under the CAA whenever new data or
information suggests an air pollutant is more toxic than previously determined,
which is consistent with the Agency's position in its April 2006 commercial
sterilizer RTR rule. If the results of new residual risk reviews show that people
are exposed to unacceptable risk levels, the EPA should revise the respective
NESHAPs for source categories emitting ethylene oxide or chloroprene without
cost considerations to reduce risks to acceptable levels. The EPA has missed
deadlines for four technology reviews for four source categories, and one is due in
2022. For efficiency purposes, the EPA could combine the residual risk reviews
with the technology reviews to conduct new RTRs for the five source categories.
Without new RTRs or emission standards, the EPA may not be able to achieve
environmental justice to protect the health of overburdened minority and
low-income communities.
Recommendations
We recommend that the assistant administrator for Air and Radiation:
1.	Develop and implement an internal control process with specific criteria to
determine whether and when new residual risk reviews of existing
National Emission Standards for Hazardous Air Pollutants and
uncontrolled emission sources are needed to incorporate new risk
information that demonstrates that an air pollutant is more toxic than
previously determined.
2.	Conduct new residual risk reviews for Group I polymers and resins that
cover neoprene production, synthetic organic chemical manufacturing
industry, polyether polyols production, commercial sterilizers, and
hospital sterilizers using the new risk values for chloroprene and ethylene
oxide and revise the corresponding National Emission Standards for
Hazardous Air Pollutants, as needed.
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3.	Revise National Emission Standards for Hazardous Air Pollutants for
chemical manufacturing area sources to regulate ethylene oxide and
conduct a residual risk review to ensure that the public is not exposed to
unacceptable risks.
4.	Conduct overdue technology reviews for Group I polymers and resins that
cover neoprene production, synthetic organic chemical manufacturing
industry, commercial sterilizers, hospital sterilizers, and chemical
manufacturing area sources, which are required to be completed at least
every eight years by the Clean Air Act.
Agency Response and OIG Assessment
The Agency offered an alternative Recommendation 1 to determine whether
regulatory changes are needed because it believes that there are other authorities
besides residual risk reviews under CAA Section 112(f) that could be equally
effective at addressing air pollutants that are more toxic than previously
determined. While the Agency did not state the authorities in its response to our
draft report, it asserted during discussions with the OIG that it can adequately
consider and account for risk in the process of conducting technology reviews.
We disagree with the Agency's position. We acknowledge that, in some instances,
revising standards under the statutorily required recurring eight-year technology
review may reduce public health risks to acceptable levels or provide an ample
margin of safety regarding air pollutants that have been determined to be more
toxic than previously understood. There is no assurance of this, however. The
CAA's two-stage process for addressing air toxics emissions from stationary
sources begins with the promulgation of technology-based standards, but it
expressly requires further analysis and more protective standards in cases in
which technology-based standards are not adequately protective of public health.
The Agency, in essence, argues that a technology review alone pursuant to CAA
Section 112(d) can be relied upon to do the work of a residual risk review
pursuant to CAA Section 112(f). This is inconsistent with the text of these
provisions and with basic principles of statutory interpretation. Since any updates
to existing risk values or an establishment of new risk values may or may not
result in unacceptable public health risks, we revised Recommendation 1 to
include establishing specific criteria to determine whether and when new residual
risk reviews are needed. The Agency's proposed corrective actions for its
suggested alternative Recommendation 1 do not meet the intent of our revised
Recommendation 1. Therefore, Recommendation 1 remains unresolved.
The Agency offered an alternative recommendation for Recommendation 2 to
seek to reduce risk from ethylene oxide and chloroprene by conducting reviews
that consider risk for the listed source categories. The Agency's alternative
recommendation does not commit to completing residual risk reviews even
though the EPA's IRIS program issued a URE for chloroprene for the first time in
2010 and a revised URE for ethylene oxide in 2016 that demonstrated that these
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pollutants were more carcinogenic than previously understood. Despite
chloroprene being classified as a likely human carcinogen and ethylene oxide as a
human carcinogen, the EPA has not conducted new residual risk reviews for
Group I polymers and resins, synthetic organic chemical manufacturing industry,
polyether polyols production, and commercial sterilizers. Residual risk reviews
for these source categories were conducted prior to the issuance of new or revised
UREs for chloroprene and ethylene oxide. Based on Agency comments on the
draft report, we divided the recommendation into two recommendations. We
recommend that the Agency conduct residual risk reviews in Recommendation 2
and technology reviews in Recommendation 4. The Agency did not offer any
proposed corrective actions to conduct residual risk reviews for the five source
categories in Recommendation 2. Therefore, Recommendation 2 is unresolved.
Based on Agency comments on the draft report, we revised Recommendation 3,
recommending that the Agency revise the NESHAP for chemical manufacturing
area sources to include regulating ethylene oxide and conducting a residual risk
review. The Agency proposed corrective actions focused on completing a
technology review. Therefore, Recommendation 3 is unresolved.
As stated above, we divided Recommendation 2 from our draft report into two
recommendations based on Agency comments and added the chemical
manufacturing area sources to Recommendation 4. In its response, the Agency
provided dates for the completion of technology reviews for the source categories
we included in Recommendations 2 and 3 of our draft report. This meets the intent
of the new Recommendation 4; therefore, this recommendation is resolved.
The Agency stated that it did not believe it was necessary to include Appendix C in
our report because the census block-level data are even less reliable than the census
tract-level data in NATA. The Agency also believed that the census tract-level data
in Table 3 already provides a complete picture of the relevant source categories
covered in the recommendations. We disagree with the Agency's position. Table 3
does not include hospital sterilizers. Appendix C provides the additional support for
our recommendations. In addition, the Agency has not conducted investigations or
refined modeling for most of the facilities in Appendix C to determine the current
risks attributed to their emissions since the Agency completed the 2014 NATA in
August 2018. Furthermore, if the EPA were to conduct only technology reviews,
the Agency would not be obligated to assess risk and communicate the resultant
risk to the public. Therefore, Appendix C is included in the report.
Appendix D contains the Agency's response to the draft report. The Agency also
provided specific technical suggestions for our consideration. We revised the report
as appropriate.
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Status of Recommendations and
Potential Monetary Benefits
RECOMMENDATIONS
Rec. No.
Page
No.
Subject
Status1
Action Official
Planned
Completion
Date
Potential
Monetary
Benefits
(in $000s)
1
26
Develop and implement an internal control process with specific
criteria to determine whether and when new residual risk reviews
of existing National Emission Standards for Hazardous Air
Pollutants and uncontrolled emission sources are needed to
incorporate new risk information that demonstrates that an air
pollutant is more toxic than previously determined.
U
Assistant Administrator for
Air and Radiation


2
26
Conduct new residual risk reviews for Group I polymers and
resins that cover neoprene production, synthetic organic
chemical manufacturing industry, polyether polyols production,
commercial sterilizers, and hospital sterilizers using the new risk
values for chloroprene and ethylene oxide and revise the
corresponding National Emission Standards for Hazardous Air
Pollutants, as needed.
U
Assistant Administrator for
Air and Radiation


3
27
Revise National Emission Standards for Hazardous Air
Pollutants for chemical manufacturing area sources to regulate
ethylene oxide and conduct a residual risk review to ensure that
the public is not exposed to unacceptable risks.
u
Assistant Administrator for
Air and Radiation


4
27
Conduct overdue technology reviews for Group I polymers and
R
Assistant Administrator for
4th Quarter

resins that cover neoprene production, synthetic organic	Air and Radiation	Fiscal Year
chemical manufacturing industry, commercial sterilizers, hospital	2024
sterilizers, and chemical manufacturing area sources, which are
required to be completed at least every eight years by the Clean
Air Act.
1 C = Corrective action completed.
R = Recommendation resolved with corrective action pending.
U = Recommendation unresolved with resolution efforts in progress.
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Appendix A
Residual Risk Review Status of Source
Categories with MACT Standards
The Agency has conducted residual risk reviews for 98 of 119 source categories with MACT
standards. The Agency has not conducted residual risk reviews for 21 of 119 source categories
with MACT standards, but it is under a court order to conduct residual risk reviews, along with
technology reviews, for six of the 21 remaining source categories by November 1, 2021, as
shown in the figure below.
In 2020, the EPA completed RTRs for 28 source categories pursuant to court orders and one
source category, mercury and air toxics standards for power plants, not pursuant to court orders.
According to the Agency, it typically conducted about seven RTRs per year before 2020.
Figure A-1: Universe of 119 source categories with MACT standards controlling air toxics
emissions and their residual risk review status
I Source categories with residual risk
reviews due between 2010 and 2023, not
pursuant to court order
I Source categories with residual risk
reviews due by November 1, 2021,
pursuant to court order
Source category with residual risk and
technology reviews due by April 1, 2022,
pursuant to court order
I Source category with residual risk and
technology reviews due by December 26,
2022, pursuant to court order
I Source categories with completed
residual risk reviews
Source: OIG summary based on the CAA and information from the EPA. (EPA OIG image)
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Appendix B
Comparison of Residual Risk Review and Technoiogy Review

Residual risk review
Technology review
Purpose
• The EPA assesses the remaining health
and environmental risks from air toxics
emissions after implementation of the
original MACT standards.
•	The EPA assesses advances in practices,
processes, and control technologies.
•	The EPA also takes this opportunity to
address unregulated emission points, to
require consistent monitoring and add
electronic compliance reporting, and to
resolve administrative requirements that are
duplicative or inconsistent.
Frequency
• The EPA conducts a residual risk review
within eight years of promulgating the
original MACT standard. The CAA is silent
on the frequency of residual risk reviews
after the initial one was conducted.3
The EPA stated in the 2006 commercial
sterilizers RTR rulemaking that it has the
authority to revisit past rulemakings if
improvements to science suggest that the
public is exposed to significant increases
in risk as compared to the initial residual
risk review.
• The CAA requires the EPA to conduct a
technology review every eight years after the
original standard was developed.
Reason for
revising
standards
•	If risks are determined to be unacceptable,
the EPA revises the MACT standards
without cost considerations.
•	If current MACT standards do not provide
an "ample margin of safety" to protect
public health, the EPA revises the
standards if cost effective.
• If the Agency finds cost-effective approaches
to further reduce emissions, it revises the
MACT standards, taking into account
advances in practices, processes, and
control technologies.
Whether
review is
required for
area sources
with GACT
standards
• The EPA is not required to conduct
residual risk reviews of area source
categories subject to GACT standards.
• The EPA is required to conduct technology
reviews of all major and area source
categories.
Source: CAA and information from the EPA. (EPA OIG table)
a The court in Citizens for Pennsylvania's Future v. Andrew R. Wheeler, No. 19-CV-02004-VC (N.D. Cal. June
26, 2020) found that the CAA did not create a mandatory duty for the EPA to review risk-based standards for
potential revision when technology-based standards are revised.
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Appendix C
Ethylene Oxide Facilities That EPA Identified as Contributing
to Cancer Risks Equal to or Greater Than 100 in One Million
in 2014 NAT A Interim Work Files at
Census Block Level but Not at Census Tract Level
EPA
region
Facility
Location
Type of facility
Refined modeling
completed after
2014 NATA
N = No
Y = Yes
2
Ashland Specialty
Ingredients
Parlin, NJ
Chemical plant
N
3
Bayer Material Science-
South Charleston
South Charleston,
WV
Chemical plant
N

(Covestro)



Union Carbide
South Charleston,
WV


3
Corporation-South
Charleston Facility
Chemical plant
Y
4
Stepan Company
Winder, GA
Chemical plant
N
4
Frye Regional Medical
Center
Hickory, NC
Hospital sterilizer
N
4
Kendall Healthcare
Products
Augusta, GA
Commercial
sterilizer
N
A
International Sterilization
Groveland, FL
Commercial
N

Laboratory
sterilizer
4
BASF Whitestone Plant
Whitestone, SC
Chemical plant
N
4
First Health Moore
Regional Hospital
Pinehurst, NC
Hospital sterilizer
N
4
Sterigenics U.S. LLC
Charlotte, NC
Commercial
sterilizer
N
4
Monument Chemical
Kentucky LLC
Brandenburg, KY
Chemical plant
Y
5
Pelron Corporation (Ele)
McCook, IL
Chemical plant
N
5
Cook Medical
Ellettsville, IN
Commercial
sterilizer
N a
5
Air Products Performance
Manufacturing (Evonik)
Milton, Wl
Chemical plant
N
6
Huntsman Corporation
Conroe Facility
Conroe, TX
Chemical plant
Y
6
Akzo Nobel, Houston Plant
Houston, TX
Chemical plant
N
6
Union Carbide Corp.
Seadrift Plant
Seadrift, TX
Chemical plant
Y
e
Baxter Healthcare
Mountain Home,
Commercial
N
o
Corporation
AR
sterilizer
6
BASF Corp. - Geismar Site
Geismar, LA
Chemical plant
Y
6
LyondellBasell
Channelview Plant
Channelview, TX
Chemical plant
Y
6
Dow Chemical Co. -
Louisiana Operations
Plaquemine, LA
Chemical plant
Y
6
Arkema Inc. Clear Lake
Plant
Pasadena, TX
Chemical plant
Y
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EPA
region
Facility
Location
Type of facility
Refined modeling
completed after
2014 NATA
N = No
Y = Yes
6
LyondellBasell Bayport
Underwood Plant
Pasadena, TX
Chemical plant
N
6
Shell Chemical LP -
Geismar Plant
Geismar, LA
Chemical plant
Y
7
Penford Products Co.
Cedar Rapids, IA
Chemical plant
N
7
BCP Ingredients - Verona
Plant
Verona, MO
Chemical plant
N
8
North Colorado Medical
Center
Greeley, CO
Hospital sterilizer
N
8
Community Hospital
Grand Junction,
CO
Hospital sterilizer
N
9
Sterigenics U.S. Inc.
Los Angeles, CA
Commercial
sterilizer
N
Source: OIG summary of data from EPA-generated lists of facilities contributing to elevated cancer risks at the
census block level and information from the EPA. In addition, we also used data from the residual risk
assessment for the miscellaneous organic chemical manufacturing RTR rule issued on August 12, 2020.
(EPA OIG table)
a According to Region 5, the facility has reduced emissions significantly by operating under permanent total
enclosure conditions since the end of 2019. Region 5 did not think it was necessary to conduct refined
modeling since the emission reduction was significant enough not to pose an elevated cancer risk.
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Appendix D
Agency Response to Draft Report

PRO1^
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
March 5, 2021
OFFICE OF
AIR AND RADIATION
MEMORANDUM
SUBJECT: EPA Response to OIG Draft Reports titled: "EPA Should Conduct New Residual
Risk and Technology Reviews for Chloroprene- and Ethylene Oxide-Emitting
Source Categories to Protect Human Health" - Project No. OA&E-FY19-0091,
January 14, 2021; and "EPA Delayed Risk Communication and Issued Instructions
Hindering Region 5's Ability to Address Ethylene Oxide Emissions" - Project No.
OA&E-FY19-0091, February 4, 2021
The Office of Air and Radiation (OAR) welcomes the opportunity to provide comment on the
following two draft reports and their recommendations: EPA Should Conduct New Residual Risk
and Technology Reviews for Chloroprene- and Ethylene Oxide-Emitting Source Categories to
Protect Raman Health and EPA Delayed Risk Communication and Issued Instructions Hindering
Region 5's Ability to Address Ethylene Oxide Emissions. We have provided our comments in the
attachments to this memorandum and provide our initial thoughts on the recommendations in each
of the two reports below, along with other information requested in the reports.
Section 1: EPA Response to Draft Report "EPA Should Conduct New Residual Risk and
Technology Reviews for Chloroprene- and Ethylene Oxide-Emitting Source Categories to
Protect Human Health"
OIG Recommendation 1: Develop and implement an internal control process to initiate a new
residual risk and technology review of existing National Emission Standards for Hazardous Air
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FROM:	Joseph Goffman
Acting Assistant Administrator
Office of Air and Radiation
TO:
Renee McGhee-Lenart
Acting Air Director
Office of the Inspector General

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Pollutants (NESHAP) and uncontrolled emission sources whenever new risk information becomes
available that demonstrates that an air pollutant is more toxic than previously determined.
Response 1: We recommend that OIG change the recommendation to: Develop and implement an
internal control process to review source categories that emit pollutants where new information
shows that the pollutants are more toxic than previously understood in order to determine if
regulatory changes are needed.
This change is suggested because, as written, the OIG appears to be directing EPA to use a specific
statutory authority for rulemaking; however, there are other authorities that could be equally
effective at addressing the problem.
Regarding the development of an internal control process, the Office of Air Quality Planning and
Standards (OAQPS) is establishing a process as part of its Air Toxics Strategy to identify and
effectively address emerging issues, such as changes in health benchmarks. Under the strategy, the
Air Toxics Evaluation and Screening Team, which comprises a diverse group of OAQPS and
regional staff, meets weekly to discuss, identify, and address new and emerging air toxics issues.
Team members leverage contacts to conduct preliminary characterizations of these issues and
routinely engage OAQPS senior management on status, options, roles and responsibilities of
potential project teams, and communication strategies.
Planned Completion Date: Quarter 4, FY 2021
OIG Recommendation 2: Conduct new risk and technology reviews for Group I polymers and
resins that covers neoprene production, synthetic organic chemical manufacturing industry,
polyether polyols production, commercial sterilizers, and hospital sterilizers using the new risk
values for chloroprene and ethylene oxide and revise the corresponding NESHAP, as needed.
Response 2: We recommend that OIG change the recommendation to: Seek to reduce risk from
ethylene oxide and chloroprene by conducting reviews which consider risk for the following
source categories: Group I polymers and resins that covers neoprene production, synthetic organic
chemical manufacturing industry, polyether polyols production, commercial sterilizers, and
hospital sterilizers (an area source category). The reviews should use the new risk values for
chloroprene and ethylene oxide and revise the corresponding NESHAP, as needed.
We are already working on the Commercial Sterilizers Technology Review, a project that has
included extensive information collection, and we intend to consider the increased risk identified
after application of the 2016 Integrated Risk Information System (IRIS) assessment for ethylene
oxide in the proposed rule planned for later this year.
We are currently discussing settlement of a lawsuit to conduct a rulemaking for the synthetic
organic chemical manufacturing industry, and the schedule provided below will be adjusted based
on the outcome of the schedule negotiations, or, if needed, litigation related to the schedule.
Given that no final decision has yet been made on the appropriate statutory authority to utilize for
each of the rules identified above, the draft schedules below for issuing a final rulemaking are
based on the assumption that we will conduct the statutorily required technology review as part of
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any rulemaking action for these rules. EPA will consider risk as part of the rulemakings for these
source categories and we will determine whether the Agency should conduct a discretionary
residual risk review during the rulemaking. The schedules for these actions are consistent with the
amount of time that it takes to conduct the many steps associated with a NESHAP review. These
steps include: collecting data; conducting necessary technology and economic analyses;
addressing impacts on small businesses, if warranted; considering risks; working through the
formal internal and interagency review processes; issuing a notice of proposed rulemaking;
soliciting public comment; conducting appropriate outreach; holding a public hearing, if requested;
reviewing and responding to all public input; and issuing a notice of final rulemaking. (A full
residual risk review may require additional time beyond the projected dates).
Planned Completion Dates: The draft completion dates for each action are as follows:
Commercial Sterilizers: Quarter 4, FY 2022
Hospital Sterilizers: Quarter 4, FY 2023
Group 1 Polymers and Resins (Neoprene): Quarter 2, FY 2024
Synthetic Organic Chemicals Manufacturing Industry: Quarter 2, FY 2024
Polyether Polyols Production: Quarter 4, FY 2024
OIG Recommendation 3: Develop NESHAP for chemical plant area sources that emit ethylene
oxide.
Response 3: EPA is currently planning to conduct the technology review for the NESHAP for
chemical manufacturing area sources, and we intend to consider ethylene oxide emissions from
the source category as part of that review. The schedule for this action is consistent with the amount
of time that it takes to conduct the many steps associated with a NESHAP review. These steps
include: collecting data; conducting necessary technology and economic analyses; addressing
impacts on small businesses, if warranted; considering risks; working through the formal internal
and interagency review processes; issuing a notice of proposed rulemaking; soliciting public
comment; conducting appropriate outreach; holding a public hearing, if requested; reviewing and
responding to all public input; and issuing a notice of final rulemaking. (A full residual risk review
may require additional time beyond the projected date).
Planned Completion Dates: The draft completion date for this action is Quarter 4, FY 2024.
In addition, we believe that the inclusion of the information in Appendix C is not necessary and
reflects an invalid use of the National Air Toxics Assessment (NATA) results. NAT A relies on
information at the census tract level to indicate where to look closer at potential risks in certain
communities. Even at the census tract, the risk results can be uncertain and do not provide
actionable risk information. The census block level risks used by the OIG in developing Appendix
C are even less reliable and should not be included here. (Furthermore, as noted in our comments
in the attachment. Appendix C provides no additional information in terms of identifying the
source categories covered in the recommendations. Table 3 in the draft report already provides a
complete picture of the relevant source categories.)
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As we have explained to the OIG in the past, these census block level data are not the NATA
results; they are based on interim work files generated during the development of NATA and have
two important shortcomings which prevent EPA from considering it in characterizing risk:
1.	Accuracy of Emissions Data: The most recent NATA relied on 2014 emissions inventory
data, which were the most recent available information when NATA was conducted, but
which are now, of course, several years old. In addition, because EPA does not require
nationwide reporting of air toxics emissions, the data for the approximately 40,000
facilities included in the National Emissions Inventory can be incomplete and uncertain.
Additional verification is necessary to determine whether the air toxics emissions estimates
in the NEI are correct and reflect current conditions. While attempts to verify emissions
information are made during NATA's development, we focus on those facilities with the
highest risk at the census tract.
2.	Reliability of Receptor Locations: NATA presents risk results at the census tract level,
which is the smallest geographic area at which EPA is comfortable presenting screening
level estimates of risk. There are more than 73,000 census tracts in the United States.
Additional verification is necessary to determine whether the census tract receptor
locations used in the modeling to calculate exposure (and, thus, risk) are appropriate (i.e.,
reflect locations representative of where people actually live). And there are almost seven
million census blocks in the United States. No effort is made to verify whether census block
receptor locations are appropriate.
The identification of specific facilities in Appendix C likely reflects many false positives, while
the omission of others may indicate significant false negatives. Our commitments above to
consider risk as part of the review of the various source sector rules noted above will result in the
proper identification of areas with elevated risks and produce the necessary accurate information
to support responsible risk communication. We, therefore, request that the OIG remove Appendix
C from the final report.
OIG Response: For the purpose of this appendix, we only included the relevant section of the
Agency's response. We included the section removed herein in the relevant report, EPA Delayed
Risk Communication and Issued Instructions Hindering Region 5 's Ability to Address Ethylene
Oxide Emissions, Report No. 21-P-0123.
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Appendix E
Distribution
The Administrator
Deputy Administrator
Assistant Deputy Administrator
Associate Deputy Administrator
Chief of Staff, Office of the Administrator
Deputy Chief of Staff, Office of the Administrator
Assistant Administrator for Air and Radiation
Agency Follow-Up Official (the CFO)
Agency Follow-Up Coordinator
General Counsel
Associate Administrator for Congressional and Intergovernmental Relations
Associate Administrator for Public Affairs
Principal Deputy Assistant Administrator for Air and Radiation
Deputy Assistant Administrators for Air and Radiation
Director, Office of Air Quality Planning and Standards, Office of Air and Radiation
Director, Office of Continuous Improvement, Office of the Chief Financial Officer
Audit Follow-Up Coordinator, Office of the Administrator
Audit Follow-Up Coordinators, Office of Air and Radiation
Audit Follow-Up Coordinator, Office of Air Quality Planning and Standards, Office of
Air and Radiation
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