[Federal Register Volume 84, Number 174 (Monday, September 9, 2019)]
[Proposed Rules]
[Pages 47346-47404]
[FR Doc No: 2019-18330]

Vol. 84

Monday,

No. 174

September 9, 2019

Part II

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants for Cellulose
Products Manufacturing Residual Risk and Technology Review; Proposed
Rule

Federal Register / Vol. 84 , No. 174 / Monday, September 9, 2019 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

EPA-HQ-OAR-2018-0415; FRL-9998-78-OAR]
RIN 2060-AU23

National Emission Standards for Hazardous Air Pollutants for
Cellulose Products Manufacturing Residual Risk and Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is proposing
amendments to the National Emissions Standards for Hazardous Air
Pollutants (NESHAP) for Cellulose Products Manufacturing to address the
results of the residual risk and technology review (RTR) that the EPA
is required to conduct under the Clean Air Act (CAA). The EPA is
proposing to amend provisions addressing periods of startup, shutdown,
and malfunction (SSM); to add provisions regarding periodic emissions
testing and electronic reporting; to provide more flexibility for
monitoring requirements; and to make technical and editorial changes.
While the proposed amendments would not result in reductions in
emissions of hazardous air pollutants (HAP), this action, if finalized,
would result in improved monitoring, compliance, and implementation of
the rule.

DATES: Comments. Comments must be received on or before October 24,
2019. Under the Paperwork Reduction Act (PRA), comments on the
information collection provisions are best assured of consideration if
the Office of Management and Budget (OMB) receives a copy of your
comments on or before October 9, 2019.
    Public hearing. If anyone contacts us requesting a public hearing
on or before September 16, 2019, we will hold a hearing. Additional
information about the hearing, if requested, will be published in a
subsequent Federal Register document and posted at https://www.epa.gov/stationary-sources-air-pollution/cellulose-products-manufacturing-national-emission-standards. See SUPPLEMENTARY INFORMATION for
information on requesting and registering for a public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2018-0415, by any of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov/
(our preferred method). Follow the online instructions for submitting
comments.
     Email<EMAIL_ADDRESS>Include Docket ID No. EPA-
HQ-OAR-2018-0415 in the subject line of the message.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2018-0415.
     Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2018-0415, Mail Code 28221T, 1200
Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-
Friday (except federal holidays).
    Instructions: All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to https://www.regulations.gov/, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the SUPPLEMENTARY
INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Dr. Kelley Spence, Sector Policies and Programs
Division (Mail Code: E143-03), Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711; telephone number:<PHONE_NUMBER>; fax
number:<PHONE_NUMBER>; and email address<EMAIL_ADDRESS>For
specific information regarding the risk modeling methodology, contact
Mr. James Hirtz, Health and Environmental Impacts Division (C539-02),
Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina 27711;
telephone number:<PHONE_NUMBER>; and email address:
<EMAIL_ADDRESS>For questions about monitoring and testing
requirements, contact Ms. Theresa Lowe, Sector Policies and Programs
Division (D243-05), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>;
and email address<EMAIL_ADDRESS>For information about the
applicability of the NESHAP to a particular entity, contact Ms. Maria
Malave, Office of Enforcement and Compliance Assurance, U.S.
Environmental Protection Agency, WJC South Building (Mail Code 2227A),
1200 Pennsylvania Avenue NW, Washington DC 20460; telephone number:
(202) 564-7027; and email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    Public hearing. Please contact Ms. Virginia Hunt at<PHONE_NUMBER>
or by email at<EMAIL_ADDRESS>to request a public hearing, to
register to speak at the public hearing, or to inquire as to whether a
public hearing will be held.
    Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2018-0415. All documents in the docket are
listed in Regulations.gov. Although listed, some information is not
publicly available, e.g., CBI (Confidential Business Information) or
other information whose disclosure is restricted by statute. Certain
other material, such as copyrighted material, is not placed on the
internet and will be publicly available only in hard copy. Publicly
available docket materials are available either electronically in
Regulations.gov or in hard copy at the EPA Docket Center, Room 3334,
WJC West Building, 1301 Constitution Avenue NW, Washington, DC. The
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Public
Reading Room is<PHONE_NUMBER>, and the telephone number for the EPA
Docket Center is<PHONE_NUMBER>.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2018-0415. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at https://www.regulations.gov/, including any personal
information provided, unless the comment includes information claimed
to be CBI or other information whose disclosure is restricted by
statute. Do not submit information that you consider to be CBI or
otherwise protected through https://www.regulations.gov/ or email. This
type of information should be submitted by mail as discussed below.
    The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the

primary submission (i.e., on the Web, cloud, or other file sharing
system). For additional submission methods, the full EPA public comment
policy, information about CBI or multimedia submissions, and general
guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov/ website allows you to submit your
comment anonymously, which means the EPA will not know your identity or
contact information unless you provide it in the body of your comment.
If you send an email comment directly to the EPA without going through
https://www.regulations.gov/, your email address will be automatically
captured and included as part of the comment that is placed in the
public docket and made available on the internet. If you submit an
electronic comment, the EPA recommends that you include your name and
other contact information in the body of your comment and with any
digital storage media you submit. If the EPA cannot read your comment
due to technical difficulties and cannot contact you for clarification,
the EPA may not be able to consider your comment. Electronic files
should not include special characters or any form of encryption and be
free of any defects or viruses. For additional information about the
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    Submitting CBI. Do not submit information containing CBI to the EPA
through https://www.regulations.gov/ or email. Clearly mark the part or
all of the information that you claim to be CBI. For CBI information on
any digital storage media that you mail to the EPA, mark the outside of
the digital storage media as CBI and then identify electronically
within the digital storage media the specific information that is
claimed as CBI. In addition to one complete version of the comments
that includes information claimed as CBI, you must submit a copy of the
comments that does not contain the information claimed as CBI directly
to the public docket through the procedures outlined in Instructions
above. If you submit any digital storage media that does not contain
CBI, mark the outside of the digital storage media clearly that it does
not contain CBI. Information not marked as CBI will be included in the
public docket and the EPA's electronic public docket without prior
notice. Information marked as CBI will not be disclosed except in
accordance with procedures set forth in 40 Code of Federal Regulations
(CFR) part 2. Send or deliver information identified as CBI only to the
following address: OAQPS Document Control Officer (C404-02), OAQPS,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2018-0415.
    Preamble acronyms and abbreviations. We use multiple acronyms and
terms in this preamble. While this list may not be exhaustive, to ease
the reading of this preamble and for reference purposes, the EPA
defines the following terms and acronyms here:

%R percent recovery
ADI Applicability Determination Index
AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-3 model
ASTM American Society for Testing and Materials
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting Interface
CEMS continuous emissions monitoring system
CEP Cellulose Ethers Production
CFR Code of Federal Regulations
CMC carboxymethyl cellulose
COS carbonyl sulfide
CS2 carbon disulfide
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guideline
ERT Electronic Reporting Tool
FTIR Fourier Transform Infrared
GACT generally available control technology
H2S hydrogen sulfide
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEC hydroxyethyl cellulose
HEM-3 Human Exposure Model-3
HF hydrogen fluoride
HI hazard index
HPC hydroxypropyl cellulose
HPMC hydroxypropyl methyl cellulose
HQ hazard quotient
IBR incorporation by reference
ICR information collection request
ID identifier
IRIS Integrated Risk Information System
km kilometers
km\2\ square kilometers
MACT maximum achievable control technology
MC methyl cellulose
mg/kg-day milligrams per kilogram per day
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
MVP Miscellaneous Viscose Processes
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NaOH sodium hydroxide
NATA National Air Toxics Assessment
NESHAP national emission standards for hazardous air pollutants
NRC National Research Council
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OECA Office of Enforcement and Compliance Assurance
OMB Office of Management and Budget
PAH polycyclic aromatic hydrocarbons
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PDF portable document format
PM particulate matter
POM polycyclic organic matter
ppm parts per million
PRA Paperwork Reduction Act
QA quality assurance
RBLC Reasonably Available Control Technology/Best Available Control
Technology/Lowest Achievable Emission Limits Clearinghouse
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SBA Small Business Administration
SCC source classification code
SSM startup, shutdown, and malfunction
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and
Ecological Exposure model
UF uncertainty factor
[micro]g/m\3\ microgram per cubic meter
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
USGS United States Geological Survey
VCS voluntary consensus standards
VOC volatile organic compounds

    Organization of this document. The information in this preamble is
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
II. Background
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP
regulate its HAP emissions?
    C. What data collection activities were conducted to support
this action?
    D. What other relevant background information and data are
available?
III. Analytical Procedures and Decision-Making
    A. How do we consider risk in our decision-making under CAA
section 112(f)(2)?
    B. How do we perform the technology review?
    C. How do we estimate post-MACT risk posed by the source
category?
IV. Analytical Results and Proposed Decisions
    A. What are the results of the risk assessment and analyses?
    B. What are our proposed decisions regarding risk acceptability,
ample margin of safety, and adverse environmental effect?

    C. What are the results and proposed decisions based on our
technology review?
    D. What other actions are we proposing?
    E. What compliance dates are we proposing?
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulation and Controlling
Regulatory Costs
    C. Paperwork Reduction Act (PRA)
    D. Regulatory Flexibility Act (RFA)
    E. Unfunded Mandates Reform Act (UMRA)
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    J. National Technology Transfer and Advancement Act (NTTAA) and
1 CFR part 51
    K. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. General Information

A. Does this action apply to me?

    Table 1 of this preamble lists the NESHAP and associated regulated
industrial source categories that are the subject of this proposal.
Table 1 is not intended to be exhaustive, but rather provides a guide
for readers regarding the entities that this proposed action is likely
to affect. The proposed standards, once promulgated, will be directly
applicable to the affected sources. This proposed action will not
affect federal, state, local, and tribal government entities. The
Initial List of Categories of Sources Under Section 112(c)(1) of the
Clean Air Act Amendments of 1990 (see 57 FR 31576, July 16, 1992) and
Documentation for Developing the Initial Source Category List, Final
Report (see EPA-450/3-91-030, July 1992) included separate source
categories for the various cellulose products manufacturing industries.
The source categories on the initial list were Cellulose Food Casings,
Rayon, Cellophane, Methyl Cellulose, Carboxymethyl Cellulose, and
Cellulose Ethers Production. The Cellulose Ethers Production source
category on the initial list included the hydroxyethyl cellulose,
hydroxypropyl cellulose, and hydroxypropyl methyl cellulose industries.
In developing the original proposed rule for Cellulose Products
Manufacturing, we identified another cellulose products manufacturing
industry, Cellulosic Sponge Manufacturing, that was not on the initial
source category list. We added Cellulosic Sponge Manufacturing to the
source category list on November 18, 1999 (64 FR 63026) in accordance
with section 112(c) of the CAA. When the EPA proposed the Cellulose
Products Manufacturing NESHAP on August 28, 2000 (65 FR 52166), the
Cellulose Food Casings, Rayon, Cellophane, and Cellulosic Sponge
Manufacturing source categories were combined to create a new source
category called ``Miscellaneous Viscose Processes.'' At the same time,
we combined the Methyl Cellulose, Carboxymethyl Cellulose, and
Cellulose Ethers Production source categories to create a newly
expanded ``Cellulose Ethers Production'' source category. On February
12, 2002 (67 FR 6521), we published an updated source category list
that included the Miscellaneous Viscose Processes (MVP) and Cellulose
Ethers Production (CEP) source categories.

    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
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        Source category               NESHAP           NAICS code \1\
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Miscellaneous Viscose           Cellulose          325211, 325220,
 Processes.                      Products           326121, 326199.
                                 Manufacturing.
Cellulose Ethers Production...  Cellulose          325199.
                                 Products
                                 Manufacturing.
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\1\ North American Industry Classification System.

B. Where can I get a copy of this document and other related
information?

    In addition to being available in the docket, an electronic copy of
this action is available on the internet. Following signature by the
EPA Administrator, the EPA will post a copy of this proposed action at
https://www.epa.gov/cellulose-products-manufacturing-national-emission-standards. Following publication in the Federal Register, the EPA will
post the Federal Register version of the proposal and key technical
documents at this same website. Information on the overall RTR program
is available at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.
    A redline version of the regulatory language that incorporates the
proposed changes in this action is available in the docket for this
action (Docket ID No. EPA-HQ-OAR-2018-0415).

II. Background

A. What is the statutory authority for this action?

    The statutory authority for this action is provided by sections 112
and 301 of the CAA, as amended (42 U.S.C. 7401 et seq.). Section 112 of
the CAA establishes a two-stage regulatory process to develop standards
for emissions of HAP from stationary sources. Generally, the first
stage involves establishing technology-based standards and the second
stage involves evaluating those standards that are based on maximum
achievable control technology (MACT) to determine whether additional
standards are needed to address any remaining risk associated with HAP
emissions. This second stage is commonly referred to as the ``residual
risk review.'' In addition to the residual risk review, the CAA also
requires the EPA to review standards set under CAA section 112 every 8
years to determine if there are ``developments in practices, processes,
or control technologies'' that may be appropriate to incorporate into
the standards. This review is commonly referred to as the ``technology
review.'' When the two reviews are combined into a single rulemaking,
it is commonly referred to as the ``risk and technology review.'' The
discussion that follows identifies the most relevant statutory sections
and briefly explains the contours of the methodology used to implement
these statutory requirements. A more comprehensive discussion appears
in the document titled CAA Section 112 Risk and Technology Reviews:
Statutory Authority and Methodology, in the docket for this rulemaking.
    In the first stage of the CAA section 112 standard setting process,
the EPA

promulgates technology-based standards under CAA section 112(d) for
categories of sources identified as emitting one or more of the HAP
listed in CAA section 112(b). Sources of HAP emissions are either major
sources or area sources, and CAA section 112 establishes different
requirements for major source standards and area source standards.
``Major sources'' are those that emit or have the potential to emit 10
tons per year (tpy) or more of a single HAP or 25 tpy or more of any
combination of HAP. All other sources are ``area sources.'' For major
sources, CAA section 112(d)(2) provides that the technology-based
NESHAP must reflect the maximum degree of emission reductions of HAP
achievable (after considering cost, energy requirements, and non-air
quality health and environmental impacts). These standards are commonly
referred to as MACT standards. CAA section 112(d)(3) also establishes a
minimum control level for MACT standards, known as the MACT ``floor.''
The EPA must also consider control options that are more stringent than
the floor. Standards more stringent than the floor are commonly
referred to as beyond-the-floor standards. In certain instances, as
provided in CAA section 112(h), the EPA may set work practice standards
where it is not feasible to prescribe or enforce a numerical emission
standard. For area sources, CAA section 112(d)(5) gives the EPA
discretion to set standards based on generally available control
technologies or management practices (GACT standards) in lieu of MACT
standards.
    The second stage in standard-setting focuses on identifying and
addressing any remaining (i.e., ``residual'') risk according to CAA
section 112(f). For source categories subject to MACT standards,
section 112(f)(2) of the CAA requires the EPA to determine whether
promulgation of additional standards is needed to provide an ample
margin of safety to protect public health or to prevent an adverse
environmental effect. Section 112(d)(5) of the CAA provides that this
residual risk review is not required for categories of area sources
subject to GACT standards. Section 112(f)(2)(B) of the CAA further
expressly preserves the EPA's use of the two-step approach for
developing standards to address any residual risk and the Agency's
interpretation of ``ample margin of safety'' developed in the National
Emissions 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 (Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA
notified Congress in the Risk Report that the Agency intended to use
the Benzene NESHAP approach in making CAA section 112(f) residual risk
determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently
adopted this approach in its residual risk determinations and the
United States Court of Appeals for the District of Columbia Circuit
(the Court) upheld the EPA's interpretation that CAA section 112(f)(2)
incorporates the approach established in the Benzene NESHAP. See NRDC
v. EPA, 529 F.3d 1077, 1083 (DC Cir. 2008).
    The approach incorporated into the CAA and used by the EPA to
evaluate residual risk and to develop standards under CAA section
112(f)(2) is a two-step approach. In the first step, the EPA determines
whether risks are acceptable. This determination ``considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR)
\1\ of approximately 1 in 10 thousand.'' 54 FR 38045, September 14,
1989. If risks are unacceptable, the EPA must determine the emissions
standards necessary to reduce risk to an acceptable level without
considering costs. In the second step of the approach, the EPA
considers whether the emissions standards provide an ample margin of
safety to protect public health ``in consideration of all health
information, including the number of persons at risk levels higher than
approximately 1 in 1 million, as well as other relevant factors,
including costs and economic impacts, technological feasibility, and
other factors relevant to each particular decision.'' Id. The EPA must
promulgate emission standards necessary to provide an ample margin of
safety to protect public health or determine that the standards being
reviewed provide an ample margin of safety without any revisions. After
conducting the ample margin of safety analysis, we consider whether a
more stringent standard is necessary to prevent, taking into
consideration costs, energy, safety, and other relevant factors, an
adverse environmental effect.
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    \1\ Although defined as ``maximum individual risk,'' MIR refers
only to cancer risk. MIR, one metric for assessing cancer risk, is
the estimated risk if an individual were exposed to the maximum
level of a pollutant for a lifetime.
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    CAA section 112(d)(6) separately requires the EPA to review
standards promulgated under CAA section 112 and revise them ``as
necessary (taking into account developments in practices, processes,
and control technologies)'' no less often than every 8 years. In
conducting this review, which we call the ``technology review,'' the
EPA is not required to recalculate the MACT floor. Natural Resources
Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008).
Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir.
2013). The EPA may consider cost in deciding whether to revise the
standards pursuant to CAA section 112(d)(6).

B. What is this source category and how does the current NESHAP
regulate its HAP emissions?

    The MVP source category includes any facility engaged in the
production of cellulose food casings, rayon, cellophane, or cellulosic
sponges, which includes the following process steps: Production of
alkali cellulose from cellulose and sodium hydroxide (NaOH); production
of sodium cellulose xanthate from alkali cellulose and carbon disulfide
(CS2) (xanthation); production of viscose from sodium
cellulose xanthate and NaOH solution; regeneration of liquid viscose
into solid cellulose; \2\ and washing of the solid cellulose product
(see 65 FR 52171-2, August 28, 2000). It should be noted that, while
the current Cellulose Products Manufacturing NESHAP includes standards
for rayon manufacturing, all rayon plants in the United States have
shut down since promulgation of the original rule.
---------------------------------------------------------------------------

    \2\ The MVP operations use different methods and equipment to
complete the regeneration step. Cellulose food casing operations
extrude viscose through a die, forming a tube, while rayon
operations extrude viscose through spinnerets, forming thin strands.
Cellophane operations extrude viscose through a long slit, forming a
flat sheet, while cellulosic sponge operations feed a mixture of
viscose and Glauber's salt into a sponge mold.
---------------------------------------------------------------------------

    The CEP source category includes any facility engaged in the
production of carboxymethyl cellulose (CMC), hydroxyethyl cellulose
(HEC), hydroxypropyl cellulose (HPC), methyl cellulose (MC), or
hydroxypropyl methyl cellulose (HPMC), which includes the following
process steps: Production of alkali cellulose from cellulose and NaOH;
reaction of the alkali cellulose with one or more organic chemicals to
produce a cellulose ether product; \3\ washing and purification of the
cellulose ether product; and drying of the cellulose ether product (see
65 FR 52171, August 28, 2000).
---------------------------------------------------------------------------

    \3\ To produce CMC, HEC, HPC, MC, and HPMC, alkali cellulose is
reacted with chloroacetic acid, ethylene oxide, propylene oxide,
methyl chloride, and a combination of methyl chloride and propylene
oxide, respectively.

---------------------------------------------------------------------------

    This proposal includes both a residual risk assessment and a
technology review of the emission sources subject to the Cellulose
Products Manufacturing NESHAP. The NESHAP requires MVP operations to
reduce the total sulfide emissions from their process vents and control
the CS2 emissions from their CS2 unloading and
storage operations. It also requires cellophane operations to reduce
the toluene emissions from their solvent coating operations and toluene
storage vessels. The NESHAP requires CEP operations to control the HAP
emissions from their process vents, wastewater, equipment leaks, and
liquid streams in open systems. The NESHAP requires both MVP and CEP
operations to comply with work practice standards for closed-vent
systems and heat exchanger systems. The NESHAP also includes various
operating limits, initial and continuous compliance requirements, and
recordkeeping and reporting requirements for the MVP and CEP source
categories.

C. What data collection activities were conducted to support this
action?

    On June 8, 2018, the EPA sent out a survey to the cellulose
products manufacturing industry to gather information needed to conduct
the regulatory reviews required under CAA sections 112(d)(6) and
112(f)(2). The EPA divided the survey into two parts. Part 1 requested
updated inventory data for emission sources subject to 40 CFR part 63,
subpart UUUU, to support the residual risk assessment for the two
source categories for purposes of detailed residual risk modeling. Part
2 requested available information on process equipment, control
devices, and other pertinent information to support the 40 CFR part 63,
subpart UUUU, technology review. The response rate for the survey was
100 percent. For more details on the data collection conducted to
prepare inputs for the residual risk assessment, see the memorandum
titled Preparation of the Residual Risk Modeling Input File for Subpart
UUUU, in the docket for this rulemaking. For more details on the data
collection conducted for the technology review, see the memorandum
titled Technology Review for the Cellulose Products Manufacturing
Source Category--Proposed Rule, also available in the docket.

D. What other relevant background information and data are available?

    In addition to survey data provided by the regulated facilities,
the EPA reviewed a number of other information sources to determine if
there have been developments in practices, processes, or control
technologies by cellulose products manufacturing facilities to support
the technology review. These information sources include:
     Emissions data (e.g., stack test reports and continuous
emissions monitoring system (CEMS) data) submitted with survey
responses;
     Facility operating permits submitted with survey responses
and collected from state agencies;
     Semiannual compliance reports submitted with survey
responses;
     Other documentation submitted with survey responses (e.g.,
compliance calculations; process flow diagrams; Safety Data Sheets;
information on monitoring, wastewater, and equipment leaks);
     Information on air pollution control options utilized by
the industry from the EPA's Reasonably Available Control Technology/
Best Available Control Technology/Lowest Achievable Emission Limits
Clearinghouse (RBLC);
     Information on applicability and compliance issues from
the EPA's Applicability Determination Index (ADI); and
     Literature review of recent information on MVP and CEP
practices, processes, and control technologies.

III. Analytical Procedures and Decision-Making

    In this section, we describe the analyses performed to support the
proposed decisions for the RTR and other issues addressed in this
proposal.

A. How do we consider risk in our decision-making under CAA section
112(f)(2)?

    As discussed in section II.A of this preamble and in the Benzene
NESHAP, in evaluating and developing standards under CAA section
112(f)(2), we apply a two-step approach to determine whether or not
risks are acceptable and to determine if the standards provide an ample
margin of safety to protect public health. As explained in the Benzene
NESHAP, ``the first step judgment on acceptability cannot be reduced to
any single factor'' and, thus, ``[t]he Administrator believes that the
acceptability of risk under section 112 is best judged on the basis of
a broad set of health risk measures and information.'' 54 FR 38046,
September 14, 1989. Similarly, with regard to the ample margin of
safety determination, ``the Agency again considers all of the health
risk and other health information considered in the first step. Beyond
that information, additional factors relating to the appropriate level
of control will also be considered, including cost and economic impacts
of controls, technological feasibility, uncertainties, and any other
relevant factors.'' Id.
    The Benzene NESHAP approach provides flexibility regarding factors
the EPA may consider in making determinations and how the EPA may weigh
those factors for each source category. The EPA conducts a risk
assessment that provides estimates of the MIR posed by the HAP
emissions from each source in the source category, the hazard index
(HI) for chronic exposures to HAP with the potential to cause noncancer
health effects, and the hazard quotient (HQ) for acute exposures to HAP
with the potential to cause noncancer health effects.\4\ The assessment
also provides estimates of the distribution of cancer risk within the
exposed populations, cancer incidence, and an evaluation of the
potential for an adverse environmental effect. The scope of the EPA's
risk analysis is consistent with the EPA's response to comments on our
policy under the Benzene NESHAP where the EPA explained that:
---------------------------------------------------------------------------

    \4\ The MIR is defined as the cancer risk associated with a
lifetime of exposure at the highest concentration of HAP where
people are likely to live. The HQ is the ratio of the potential HAP
exposure concentration to the noncancer dose-response value; the HI
is the sum of HQs for HAP that affect the same target organ or organ
system.

``[t]he policy chosen by the Administrator permits consideration of
multiple measures of health risk. Not only can the MIR figure be
considered, but also incidence, the presence of non-cancer health
effects, and the uncertainties of the risk estimates. In this way,
the effect on the most exposed individuals can be reviewed as well
as the impact on the general public. These factors can then be
weighed in each individual case. This approach complies with the
Vinyl Chloride mandate that the Administrator ascertain an
acceptable level of risk to the public by employing his expertise to
assess available data. It also complies with the Congressional
intent behind the CAA, which did not exclude the use of any
particular measure of public health risk from the EPA's
consideration with respect to CAA section 112 regulations, and
thereby implicitly permits consideration of any and all measures of
health risk which the Administrator, in his judgment, believes are
---------------------------------------------------------------------------
appropriate to determining what will `protect the public health'.''

    See 54 FR 38057, September 14, 1989. Thus, the level of the MIR is
only one factor to be weighed in determining acceptability of risk. The
Benzene NESHAP explained that ``an MIR of approximately one in 10
thousand should ordinarily be the upper end of the range of
acceptability. As risks increase above this benchmark, they become
presumptively less acceptable under CAA section 112, and would be
weighed with the other health risk measures and information in making
an

overall judgment on acceptability. Or, the Agency may find, in a
particular case, that a risk that includes an MIR less than the
presumptively acceptable level is unacceptable in the light of other
health risk factors.'' Id. at 38045. In other words, risks that include
an MIR above 100-in-1 million may be determined to be acceptable, and
risks with an MIR below that level may be determined to be
unacceptable, depending on all of the available health information.
Similarly, with regard to the ample margin of safety analysis, the EPA
stated in the Benzene NESHAP that: ``EPA believes the relative weight
of the many factors that can be considered in selecting an ample margin
of safety can only be determined for each specific source category.
This occurs mainly because technological and economic factors (along
with the health-related factors) vary from source category to source
category.'' Id. at 38061. We also consider the uncertainties associated
with the various risk analyses, as discussed earlier in this preamble,
in our determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information
to date in making residual risk determinations. At this time, we do not
attempt to quantify the HAP risk that may be associated with emissions
from other facilities that do not include the source categories under
review, mobile source emissions, natural source emissions, persistent
environmental pollution, or atmospheric transformation in the vicinity
of the sources in the categories.
    The EPA understands the potential importance of considering an
individual's total exposure to HAP in addition to considering exposure
to HAP emissions from the source category and facility. We recognize
that such consideration may be particularly important when assessing
noncancer risk, where pollutant-specific exposure health reference
levels (e.g., reference concentrations (RfCs)) are based on the
assumption that thresholds exist for adverse health effects. For
example, the EPA recognizes that, although exposures attributable to
emissions from a source category or facility alone may not indicate the
potential for increased risk of adverse noncancer health effects in a
population, the exposures resulting from emissions from the facility in
combination with emissions from all of the other sources (e.g., other
facilities) to which an individual is exposed may be sufficient to
result in an increased risk of adverse noncancer health effects. In May
2010, the Science Advisory Board (SAB) advised the EPA ``that RTR
assessments will be most useful to decision makers and communities if
results are presented in the broader context of aggregate and
cumulative risks, including background concentrations and contributions
from other sources in the area.'' \5\
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    \5\ Recommendations of the SAB Risk and Technology Review Panel
are provided in their report, which is available at: https://
yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
---------------------------------------------------------------------------

    In response to the SAB recommendations, the EPA incorporates
cumulative risk analyses into its RTR risk assessments, including those
reflected in this proposal. The Agency (1) conducts facility-wide
assessments, which include source category emission points, as well as
other emission points within the facilities; (2) combines exposures
from multiple sources in the same category that could affect the same
individuals; and (3) for some persistent and bioaccumulative
pollutants, analyzes the ingestion route of exposure. In addition, the
RTR risk assessments consider aggregate cancer risk from all
carcinogens and aggregated noncancer HQs for all noncarcinogens
affecting the same target organ or target organ system.
    Although we are interested in placing source category and facility-
wide HAP risk in the context of total HAP risk from all sources
combined in the vicinity of each source, we are concerned about the
uncertainties of doing so. Estimates of total HAP risk from emission
sources other than those that we have studied in depth during this RTR
review would have significantly greater associated uncertainties than
the source category or facility-wide estimates. Such aggregate or
cumulative assessments would compound those uncertainties, making the
assessments too unreliable.

B. How do we perform the technology review?

    Our technology review focuses on the identification and evaluation
of developments in practices, processes, and control technologies that
have occurred since the MACT standards were promulgated. Where we
identify such developments, we analyze their technical feasibility,
estimated costs, energy implications, and non-air environmental
impacts. We also consider the emission reductions associated with
applying each development. This analysis informs our decision of
whether it is ``necessary'' to revise the emissions standards. In
addition, we consider the appropriateness of applying controls to new
sources versus retrofitting existing sources. For this exercise, we
consider any of the following to be a ``development'':
     Any add-on control technology or other equipment that was
not identified and considered during development of the original MACT
standards;
     Any improvements in add-on control technology or other
equipment (that were identified and considered during development of
the original MACT standards) that could result in additional emissions
reduction;
     Any work practice or operational procedure that was not
identified or considered during development of the original MACT
standards;
     Any process change or pollution prevention alternative
that could be broadly applied to the industry and that was not
identified or considered during development of the original MACT
standards; and
     Any significant changes in the cost (including cost
effectiveness) of applying controls (including controls the EPA
considered during the development of the original MACT standards).
    In addition to reviewing the practices, processes, and control
technologies that were considered at the time we originally developed
the NESHAP, we review a variety of data sources in our investigation of
potential practices, processes, or controls to consider. See sections
II.C and II.D of this preamble for information on the specific data
sources that were reviewed as part of the technology review.

C. How do we estimate post-MACT risk posed by the source category?

    In this section, we provide a complete description of the types of
analyses that we generally perform during the risk assessment process.
In some cases, we do not perform a specific analysis because it is not
relevant. For example, in the absence of emissions of HAP known to be
persistent and bioaccumulative in the environment (PB-HAP), we would
not perform a multipathway exposure assessment. Where we do not perform
an analysis, we state that we do not and provide the reason. While we
present all of our risk assessment methods, we only present risk
assessment results for the analyses actually conducted (see section
IV.A of this preamble).
    The EPA conducts a risk assessment that provides estimates of the
MIR for cancer posed by the HAP emissions from each source in the
source category, the HI for chronic exposures to HAP with the potential
to cause noncancer

health effects, and the HQ for acute exposures to HAP with the
potential to cause noncancer health effects. The assessment also
provides estimates of the distribution of cancer risk within the
exposed populations, cancer incidence, and an evaluation of the
potential for an adverse environmental effect. The seven sections that
follow this paragraph describe how we estimated emissions and conducted
the risk assessment. The docket for this rulemaking contains the
following documents which provide more information on the risk
assessment inputs and models: Residual Risk Assessment for the
Miscellaneous Viscose Processes Source Category in Support of the 2019
Risk and Technology Review Proposed Rule and Residual Risk Assessment
for the Cellulose Ethers Production Source Category in Support of the
2019 Risk and Technology Review Proposed Rule. The methods used to
assess risk (as described in the eight primary steps below) are
consistent with those described by the EPA in the document reviewed by
a panel of the EPA's SAB in 2009; \6\ and described in the SAB review
report issued in 2010. They are also consistent with the key
recommendations contained in that report.
---------------------------------------------------------------------------

    \6\ U.S. EPA. Risk and Technology Review (RTR) Risk Assessment
Methodologies: For Review by the EPA's Science Advisory Board with
Case Studies--MACT I Petroleum Refining Sources and Portland Cement
Manufacturing, June 2009. EPA-452/R-09-006. https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions
release characteristics?
    As discussed in section II.C of this preamble, we used data from
Part 1 of the 2018 survey as the basis for the risk assessment for the
MVP and CEP source categories. Part 1 of the survey, which concluded in
August/September 2018, targeted facilities that are major sources of
HAP emissions and involved an update of pre-populated National
Emissions Inventory (NEI) data spreadsheets (or creation of new
datasets). The NEI is a database that contains information about
sources that emit criteria air pollutants, their precursors, and HAP.
The NEI database includes estimates of actual annual air pollutant
emissions from point and volume sources; emission release
characteristic data such as emission release height, temperature,
diameter, velocity, and flow rate; and locational latitude/longitude
coordinates. We asked facilities subject to the Cellulose Products
Manufacturing NESHAP to refine (or create new) inventories based on
their NEI datasets for purposes of detailed residual risk modeling.
Refinements included providing additional details for HAP emission
sources, providing more specific information on the location and
characteristics of emission points (e.g., updating emission release
coordinates and parameters), and adding or updating HAP emissions data
for each emission release point. We compiled the updated datasets for
each individual facility into MVP and CEP emissions databases to create
the MACT source category residual risk modeling files.
    The actual annual emissions data in the emissions databases include
data from source tests, CEMS, material balances, emission factors,
emission models, and engineering judgment provided by sources surveyed
in Part 1 of the survey. We received a comprehensive set of emissions
estimates that enabled us to conduct risk modeling of HAP emissions for
all major source facilities in the MVP and CEP source categories.
    We conducted substantial quality assurance (QA) efforts on the Part
1 data in order to create the modeling files needed for the 40 CFR part
63, subpart UUUU, residual risk assessment.\7\ We first reviewed the
Part 1 databases to remove non-applicable data (e.g., data marked for
deletion by survey respondents) unless we considered them to be source-
category data, emission units identified as not subject to the
Cellulose Products Manufacturing NESHAP, emission units identified as
shut down, records with non-HAP data, and records with zero emissions.
No duplicate emissions data were discovered during the QA.
---------------------------------------------------------------------------

    \7\ These QA efforts are discussed in an April 15, 2019
memorandum in the docket titled Preparation of the Residual Risk
Modeling Input File for Subpart UUUU.
---------------------------------------------------------------------------

    We reviewed the databases to ensure that each record contained a
facility identifier (ID), emission unit ID, and process ID. If an ID
was missing, one was assigned using information provided by industry
(e.g., from EPA databases, from emission unit description or process
description in the NEI). In some cases, emission unit IDs and process
IDs were revised for consistency. Looking across the updated MVP and
CEP inventories, we also reviewed whether there may be any referential
integrity issues associated with these IDs (e.g., having the same
emission unit ID associated with multiple emission unit descriptions or
having the same process ID associated with multiple process
descriptions or multiple source classification codes (SCCs)). In those
cases, we revised the appropriate ID to address the issue.
    In addition, each record was checked to ensure it was labeled with
a regulatory code, SCC, and emission process group. No regulatory codes
or SCCs were found missing. The SCCs for some records were revised for
consistency. Where information on emission process group was missing,
the emission process group was determined based on information from
SCCs, comments from survey respondents, etc. Next, the SCCs and
emission process groups were compared and reviewed for consistency with
each other; no issues were found.
    We reviewed the pollutant codes in the source category risk
modeling files to ensure the codes and descriptions matched the latest
code lookup table used by the EPA for risk modeling files; the review
found the records to be consistent.
    We speciated data for chromium and mercury using default speciation
criteria for those pollutants for the specific SCC. We speciated
chromium emissions as hexavalent chromium (chromium VI) and trivalent
chromium (chromium III). We speciated mercury emissions as particulate
divalent mercury, gaseous divalent mercury, and gaseous elemental
mercury. We were unable to speciate data for glycol ether for one
facility because no information on the glycol ether compound(s) emitted
was available from the facility in their Part 1 survey response or
operating permit. For unspeciated emission inventories, it is the EPA's
risk assessment policy to use the most potent noncancer health
benchmark as the default emission compound; in this case, ethylene
glycol methyl ether would be modeled.
    We reviewed the emissions data by calculating the percent of
facilities reporting each HAP, comparing emissions of a facility to
category average emissions, calculating standard deviations, and
identifying outliers. No pollutants in the MVP and CEP modeling files
were found above or below the range for either category.
    We reviewed the MVP and CEP risk modeling files to ensure that each
record in these files contained an emission release point ID. If an ID
was missing, one was assigned using information provided by industry
(e.g., from the emission unit ID or process ID). In some cases,
emission release point IDs were revised for consistency. Looking across
the updated MVP and CEP inventories, we also determined whether there
may be any referential integrity issues associated with the emission
release information. For each emission release point, each record

should have one set of coordinates (latitude and longitude) and one set
of stack or fugitive parameters. All records were reviewed for
consistency with respect to the emission release point. Where any such
issues were identified, we revised the emission release point ID,
stack/fugitive parameters, and/or coordinates to address the issue.
    We reviewed emission points labeled as stacks to ensure no fugitive
parameters were identified; any fugitive parameter values (usually
zeroes) entered for these records were deleted. We reviewed stack
parameters to ensure all were populated with reasonable values and made
changes where necessary. We checked stack height data to ensure that
they were greater than stack diameter. We checked exit gas flow rate
data to determine whether they met the EPA's criteria that the flow
rate must be within 10 percent of the calculated value (assuming a
cylindrical stack). Where exit gas flow rate values did not meet the
10-percent criteria, we conducted a review to determine the source of
the discrepancy (e.g., the reported stack parameter was in the wrong
units). We also checked for missing stack parameters and populated the
missing data using values from other records for the same emission
release point; if values from other records were not available, we
calculated the missing value based on other related parameters for the
same emission release point (e.g., calculated exit gas velocity using
available data for stack diameter and exit gas flow rate).
    We checked fugitive parameters to ensure there was an associated
length, width, and angle, and that no stack parameters for fugitive
sources were erroneously populated, other than the required national
defaults.
    We checked coordinate values (latitude and longitude) to determine
if there were any missing values and to ensure only one set of
coordinates appeared for each emission release point. We populated the
missing data using values from other records for the same emission
release point, where possible. We revised coordinate values where
necessary to ensure coordinates were consistent for the same emission
point. We also checked coordinate values to ensure that all coordinates
were on the facility property, by analyzing the distance between
coordinates at individual facilities. Only one emission point, a
wastewater treatment system emission unit, was found to be an outlier,
and the coordinates of this emission point were checked and were found
to lie on wastewater tanks near the boundary of the property.
    We checked the source category risk modeling files for missing
control measure information and filled gaps using control measure
comments provided by respondents in their Part 1 survey responses or
process diagrams provided by respondents in their Part 2 survey
responses.
    The emissions inventory for MVP sources identifies no emissions of
PB-HAP. The emissions inventory for CEP sources identifies emissions of
the following PB-HAP: Cadmium compounds, arsenic compounds, lead
compounds, and mercury compounds. Risk-based screening levels are
available for Tier 1 screening for all of the above PB-HAP except lead
compounds, which are compared to the level of the current National
Ambient Air Quality Standard (NAAQS) for lead.
    Consistent with the EPA's standard practice in conducting risk
assessments for source categories, we conducted a two-step process to
determine: (1) Whether PB-HAP are being emitted; and (2) whether they
are being released above screening levels. If these releases are
significantly above the screening levels and the EPA has detailed
information on the releases and the site, a complete multipathway
analysis of the site is conducted to estimate pathway risks for the
source category.
    We considered actual emissions of the ecological HAP emitted from
the CEP source category in the ecological HAP analysis. In addition to
the PB-HAP emitted from the CEP source category, we considered
hydrochloric acid (HCl) and hydrogen fluoride (HF) for ecological HAP
modeling. The CEP source category, however, does not emit HF. Further
information about the multipathway analysis performed for this category
follows in section IV.A.2.c of this preamble.
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include
estimates of the mass of HAP emitted during a specified annual time
period. These ``actual'' emission levels are often lower than the
emission levels allowed under the requirements of the current MACT
standards. The emissions allowed under the MACT standards are referred
to as the ``MACT-allowable'' emissions. We discussed the consideration
of both MACT-allowable and actual emissions in the final Coke Oven
Batteries RTR (70 FR 19998-19999, April 15, 2005) and in the proposed
and final Hazardous Organic NESHAP RTR (71 FR 34428, June 14, 2006, and
71 FR 76609, December 21, 2006, respectively). In those actions, we
noted that assessing the risk at the MACT-allowable level is inherently
reasonable since that risk reflects the maximum level facilities could
emit and still comply with national emission standards. We also
explained that it is reasonable to consider actual emissions, where
such data are available, in both steps of the risk analysis, in
accordance with the Benzene NESHAP approach. (54 FR 38044, September
14, 1989.)
    Actual emissions are sometimes less than allowable emissions due to
a compliance margin, a more stringent state or local rule, or over-
control due to the use of control technologies, equipment, or work
practices that are significantly better than that required to meet 40
CFR part 63, subpart UUUU, emission limits. Consequently, as part of
the Part 1 survey instructions, the EPA requested that facilities
provide MACT-allowable emissions estimates.
    Allowable emissions estimates were available for four of the five
MVP facilities. Two MVP facilities provided their allowable emissions
in their Part 1 survey spreadsheet. Two other MVP facilities provided
their allowable emissions separately, in their Part 1 survey response
letter. The latter two facilities stated that the stack parameters
would be expected to be different if they were to emit at the allowable
emissions levels because additional ductwork and ductwork modifications
would be expected in order to route additional fumes to their
biofilters if they increased capacity. While we do not intend MACT-
allowable emissions in this risk modeling effort to represent the
maximum potential-to-emit emission rate, we conservatively used this
information for modeling because it was the only readily available
information. We created new records in the MVP risk modeling file to
include just these allowable emissions data and their associated stack
parameters. To avoid any referential integrity issues, we assigned a
different emission release point ID to these allowable emissions
records.
    The remaining MVP facility did not provide allowable emissions data
in their survey spreadsheet. However, this facility is the only one in
its subcategory, so the original MACT for the subcategory was based on
their level of control. Consequently, we assumed that allowable
emissions were equal to the reported actual emissions. So, for this
facility, the allowable multiplier is 1.
    There were some gaps in the allowable emissions estimates provided
by the MVP facilities. Allowable emissions for carbonyl sulfide (COS)
were not available for one MVP facility

for one of their processes because they report it as part of the
hydrogen sulfide (H2S) limit in their title V permit. We
created a new record in the MVP risk modeling file that calculated the
COS allowable emissions for this process using the same multiplier as
H2S (6.8). Allowable emissions for CS2 were also
not available for a second MVP facility for some of their processes. We
calculated the allowable emissions for this facility using the median
of the multipliers for those processes at the facility that had
allowable emissions estimates. Using this approach, we estimated the
median allowable multiplier for CS2 for this facility to be
approximately 2.4.
    Allowable emissions estimates were available for 48 percent of the
records in the CEP risk modeling file, and the remaining 52 percent of
records had no allowable emissions estimates. Of that 52 percent of
records, 33 percent were uncontrolled sources of organic HAP, and 19
percent were controlled sources of organic HAP.
    For uncontrolled CEP sources without allowable emissions data
(e.g., fugitive emissions), we assumed that allowable emissions were
equal to their reported actual emissions, since there is no additional
control beyond current emissions. For controlled CEP sources without
allowable emissions data, we reviewed Part 2 survey data on emission
controls for these sources and found that all of these sources were
already meeting the 99-percent control required under 40 CFR part 63,
subpart UUUU, and based on the data reported, there is little if any
additional control beyond current emissions. Consequently, allowable
emissions are equal to actuals for controlled CEP sources.
3. How do we conduct dispersion modeling, determine inhalation
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations
and health risk from the source category addressed in this proposal
were estimated using the Human Exposure Model (HEM-3).\8\ The HEM-3
performs three primary risk assessment activities: (1) Conducting
dispersion modeling to estimate the concentrations of HAP in ambient
air, (2) estimating long-term and short-term inhalation exposures to
individuals residing within 50 kilometers (km) of the modeled sources,
and (3) estimating individual and population-level inhalation risk
using the exposure estimates and quantitative dose-response
information.
---------------------------------------------------------------------------

    \8\ For more information about HEM-3, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
---------------------------------------------------------------------------

a. Dispersion Modeling
    The air dispersion model AERMOD, used by the HEM-3 model, is one of
the EPA's preferred models for assessing air pollutant concentrations
from industrial facilities.\9\ To perform the dispersion modeling and
to develop the preliminary risk estimates, HEM-3 draws on three data
libraries. The first is a library of meteorological data, which is used
for dispersion calculations. This library includes 1 year (2016) of
hourly surface and upper air observations from 824 meteorological
stations, selected to provide coverage of the United States and Puerto
Rico. A second library of United States Census Bureau census block \10\
internal point locations and populations provides the basis of human
exposure calculations (U.S. Census, 2010). In addition, for each census
block, the census library includes the elevation and controlling hill
height, which are also used in dispersion calculations. A third library
of pollutant-specific dose-response values is used to estimate health
risk. These are discussed below.
---------------------------------------------------------------------------

    \9\ U.S. EPA. Revision to the Guideline on Air Quality Models:
Adoption of a Preferred General Purpose (Flat and Complex Terrain)
Dispersion Model and Other Revisions (70 FR 68218, November 9,
2005).
    \10\ A census block is the smallest geographic area for which
census statistics are tabulated.
---------------------------------------------------------------------------

b. Risk From Chronic Exposure to HAP
    In developing the risk assessment for chronic exposures, we use the
estimated annual average ambient air concentrations of each HAP emitted
by each source in the source category. The HAP air concentrations at
each nearby census block centroid located within 50 km of the facility
are a surrogate for the chronic inhalation exposure concentration for
all the people who reside in that census block. A distance of 50 km is
consistent with both the analysis supporting the 1989 Benzene NESHAP
(54 FR 38044, September 14, 1989) and the limitations of Gaussian
dispersion models, including AERMOD.
    For each facility, we calculate the MIR as the cancer risk
associated with a continuous lifetime (24 hours per day, 7 days per
week, 52 weeks per year, 70 years) exposure to the maximum
concentration at the centroid of each inhabited census block. We
calculate individual cancer risk by multiplying the estimated lifetime
exposure to the ambient concentration of each HAP (in micrograms per
cubic meter ([mu]g/m\3\)) by its unit risk estimate (URE). The URE is
an upper-bound estimate of an individual's incremental risk of
contracting cancer over a lifetime of exposure to a concentration of 1
microgram of the pollutant per cubic meter of air. For residual risk
assessments, we generally use UREs from the EPA's Integrated Risk
Information System (IRIS). For carcinogenic pollutants without IRIS
values, we look to other reputable sources of cancer dose-response
values, often using California EPA (CalEPA) UREs, where available. In
cases where new, scientifically credible dose-response values have been
developed in a manner consistent with the EPA guidelines and have
undergone a peer review process similar to that used by the EPA, we may
use such dose-response values in place of, or in addition to, other
values, if appropriate. The pollutant-specific dose-response values
used to estimate health risk are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
    To estimate individual lifetime cancer risks associated with
exposure to HAP emissions from each facility in the source category, we
sum the risks for each of the carcinogenic HAP \11\ emitted by the
modeled facility. We estimate cancer risk at every census block within
50 km of every facility in the source category. The MIR is the highest
individual lifetime cancer risk estimated for any of those census
blocks. In addition to calculating the MIR, we estimate the
distribution of individual cancer risks for the source category by
summing the number of individuals within 50 km of the sources whose
estimated risk falls within a specified risk range. We also estimate
annual

cancer incidence by multiplying the estimated lifetime cancer risk at
each census block by the number of people residing in that block,
summing results for all of the census blocks, and then dividing this
result by a 70-year lifetime.
---------------------------------------------------------------------------

    \11\ The EPA's 2005 Guidelines for Carcinogen Risk Assessment
classifies carcinogens as: ``carcinogenic to humans,'' ``likely to
be carcinogenic to humans,'' and ``suggestive evidence of
carcinogenic potential.'' These classifications also coincide with
the terms ``known carcinogen, probable carcinogen, and possible
carcinogen,'' respectively, which are the terms advocated in the
EPA's Guidelines for Carcinogen Risk Assessment, published in 1986
(51 FR 33992, September 24, 1986). In August 2000, the document,
Supplemental Guidance for Conducting Health Risk Assessment of
Chemical Mixtures (EPA/630/R-00/002), was published as a supplement
to the 1986 document. Copies of both documents can be obtained from
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing
the risk of these individual compounds to obtain the cumulative
cancer risk is an approach that was recommended by the EPA's SAB in
their 2002 peer review of the EPA's National Air Toxics Assessment
(NATA) titled NATA--Evaluating the National-scale Air Toxics
Assessment 1996 Data--an SAB Advisory, available at https://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
---------------------------------------------------------------------------

    To assess the risk of noncancer health effects from chronic
exposure to HAP, we calculate either an HQ or a target organ-specific
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is
emitted. Where more than one noncancer HAP is emitted, we sum the HQ
for each of the HAP that affects a common target organ or target organ
system to obtain a TOSHI. The HQ is the estimated exposure divided by
the chronic noncancer dose-response value, which is a value selected
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC, defined as ``an estimate (with
uncertainty spanning perhaps an order of magnitude) of a continuous
inhalation exposure to the human population (including sensitive
subgroups) that is likely to be without an appreciable risk of
deleterious effects during a lifetime'' (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary). In cases where an RfC
from the EPA's IRIS is not available or where the EPA determines that
using a value other than the RfC is appropriate, the chronic noncancer
dose-response value can be a value from the following prioritized
sources, which define their dose-response values similarly to the EPA:
(1) The Agency for Toxic Substances and Disease Registry (ATSDR)
Minimum Risk Level (https://www.atsdr.cdc.gov/mrls/index.asp); (2) the
CalEPA Chronic Reference Exposure Level (REL) (https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0); or (3) as noted above, a scientifically
credible dose-response value that has been developed in a manner
consistent with the EPA guidelines and has undergone a peer review
process similar to that used by the EPA. The pollutant-specific dose-
response values used to estimate health risks are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
c. Risk From Acute Exposure to HAP That May Cause Health Effects Other
Than Cancer
    For each HAP for which appropriate acute inhalation dose-response
values are available, the EPA also assesses the potential health risks
due to acute exposure. For these assessments, the EPA makes
conservative assumptions about emission rates, meteorology, and
exposure location. In this proposed rulemaking, as part of our efforts
to continually improve our methodologies to evaluate the risks that HAP
emitted from categories of industrial sources pose to human health and
the environment,\12\ we are revising our treatment of meteorological
data to use reasonable worst-case air dispersion conditions in our
acute risk screening assessments instead of worst-case air dispersion
conditions. This revised treatment of meteorological data and the
supporting rationale are described in more detail in the Residual Risk
Assessment for the Miscellaneous Viscose Processes Source Category in
Support of the 2019 Risk and Technology Review Proposed Rule and in the
Residual Risk Assessment for the Cellulose Ethers Production Source
Category in Support of the 2019 Risk and Technology Review Proposed
Rule and in Appendix 5 of both reports: Technical Support Document for
Acute Risk Screening Assessment. We will be applying this revision in
RTR rulemakings proposed on or after June 3, 2019.
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    \12\ See, e.g., U.S. EPA. Screening Methodologies to Support
Risk and Technology Reviews (RTR): A Case Study Analysis (Draft
Report, May 2017. https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html).
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    To assess the potential acute risk to the maximally exposed
individual, we use the peak hourly emission rate for each emission
point,\13\ reasonable worst-case air dispersion conditions (i.e., 99th
percentile), and the point of highest off-site exposure. Specifically,
we assume that peak emissions from the source category and reasonable
worst-case air dispersion conditions co-occur and that a person is
present at the point of maximum exposure.
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    \13\ In the absence of hourly emission data, we develop
estimates of maximum hourly emission rates by multiplying the
average actual annual emissions rates by a factor (either a
category-specific factor or a default factor of 10) to account for
variability. This is documented in Residual Risk Assessment for the
Miscellaneous Viscose Processes Source Category in Support of the
2019 Risk and Technology Review Proposed Rule, Residual Risk
Assessment for the Cellulose Ethers Production Source Category in
Support of the 2019 Risk and Technology Review Proposed Rule, and in
Appendix 5 of the reports: Technical Support Document for Acute Risk
Screening Assessment, both are available in the docket for this
rulemaking.
---------------------------------------------------------------------------

    To characterize the potential health risks associated with
estimated acute inhalation exposures to a HAP, we generally use
multiple acute dose-response values, including acute RELs, acute
exposure guideline levels (AEGLs), and emergency response planning
guidelines (ERPG) for 1-hour exposure durations), if available, to
calculate acute HQs. The acute HQ is calculated by dividing the
estimated acute exposure concentration by the acute dose-response
value. For each HAP for which acute dose-response values are available,
the EPA calculates acute HQs.
    An acute REL is defined as ``the concentration level at or below
which no adverse health effects are anticipated for a specified
exposure duration.'' \14\ Acute RELs are based on the most sensitive,
relevant, adverse health effect reported in the peer-reviewed medical
and toxicological literature. They are designed to protect the most
sensitive individuals in the population through the inclusion of
margins of safety. Because margins of safety are incorporated to
address data gaps and uncertainties, exceeding the REL does not
automatically indicate an adverse health impact. AEGLs repr esent
threshold exposure limits for the general public and are applicable to
emergency exposures ranging from 10 minutes to 8 hours.\15\ They are
guideline levels for ``once-in-a-lifetime, short-term exposures to
airborne concentrations of acutely toxic, high-priority chemicals.''
Id. at 21. The AEGL-1 is specifically defined as ``the airborne
concentration (expressed as ppm (parts per million) or mg/m\3\
(milligrams per cubic meter)) of a substance above which it is
predicted that the general population, including susceptible
individuals, could experience notable discomfort, irritation, or
certain asymptomatic nonsensory effects. However, the effects are not
disabling and are transient and reversible upon cessation of
exposure.'' The document also notes that ``Airborne concentrations
below AEGL-1 represent exposure levels that can produce mild and
progressively increasing but transient and nondisabling odor, taste,
and sensory irritation or certain

asymptomatic, nonsensory effects.'' Id. AEGL-2 are defined as ``the
airborne concentration (expressed as parts per million or milligrams
per cubic meter) of a substance above which it is predicted that the
general population, including susceptible individuals, could experience
irreversible or other serious, long-lasting adverse health effects or
an impaired ability to escape.'' Id.
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    \14\ CalEPA issues acute RELs as part of its Air Toxics Hot
Spots Program, and the 1-hour and 8-hour values are documented in
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The
Determination of Acute Reference Exposure Levels for Airborne
Toxicants, which is available at https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \15\ National Academy of Sciences, 2001. Standing Operating
Procedures for Developing Acute Exposure Levels for Hazardous
Chemicals, page 2. Available at https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf. Note that the
National Advisory Committee for Acute Exposure Guideline Levels for
Hazardous Substances ended in October 2011, but the AEGL program
continues to operate at the EPA and works with the National
Academies to publish final AEGLs (https://www.epa.gov/aegl).
---------------------------------------------------------------------------

    ERPGs are ``developed for emergency planning and are intended as
health-based guideline concentrations for single exposures to
chemicals.'' \16\ Id. at 1. The ERPG-1 is defined as ``the maximum
airborne concentration below which it is believed that nearly all
individuals could be exposed for up to 1 hour without experiencing
other than mild transient adverse health effects or without perceiving
a clearly defined, objectionable odor.'' Id. at 2. Similarly, the ERPG-
2 is defined as ``the maximum airborne concentration below which it is
believed that nearly all individuals could be exposed for up to one
hour without experiencing or developing irreversible or other serious
health effects or symptoms which could impair an individual's ability
to take protective action.'' Id. at 1.
---------------------------------------------------------------------------

    \16\ ERPGS Procedures and Responsibilities. March 2014. American
Industrial Hygiene Association. Available at: https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf.
---------------------------------------------------------------------------

    An acute REL for 1-hour exposure durations is typically lower than
its corresponding AEGL-1 and ERPG-1. Even though their definitions are
slightly different, AEGL-1s are often the same as the corresponding
ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from
our acute inhalation screening risk assessment typically result when we
use the acute REL for a HAP. In cases where the maximum acute HQ
exceeds 1, we also report the HQ based on the next highest acute dose-
response value (usually the AEGL-1 and/or the ERPG-1).
    As part of the Part 1 survey instructions, the EPA requested that
facilities provide acute emissions estimates. For the MVP source
category, acute emissions estimates were available for four of the five
facilities. One of the four facilities was missing an acute emission
estimate for COS for one process, but we were able to calculate an
estimate for COS by applying the same acute multiplier for
CS2 for the same process at this facility. We developed
separate acute multipliers for MVP process operations and MVP storage
tanks to estimate acute emissions for the fifth facility. We estimated
the average acute multipliers for MVP process operations and MVP
storage tanks to be approximately 1.9 and 1.1, respectively.
    For the CEP source category, acute emissions estimates were
available for 38 percent of the records in the CEP risk modeling file.
The remaining 62 percent of records had no acute emissions estimates.
For CEP sources without acute emissions data, we reviewed permits and
extracted maximum hourly rate data if available, and assumed the acute
multiplier would be 10 if no data were available.
    A further discussion of why these factors were chosen can be found
in the memorandum, Preparation of the Residual Risk Modeling Input File
for Subpart UUUU, available in the docket for this rulemaking.
    In our acute inhalation screening risk assessment, acute impacts
are deemed negligible for HAP for which acute HQs are less than or
equal to 1, and no further analysis is performed for these HAP. This
was the case for the CEP source category. In cases where an acute HQ
from the screening step is greater than 1, we assess the site-specific
data to ensure that the acute HQ is at an off-site location. This was
required for the MVP source category, in which the data refinements
employed consisted of ensuring that the locations where the maximum HQ
occurred were off facility property and where the public could
potentially be exposed. These refinements are discussed more fully in
the Residual Risk Assessment for the Miscellaneous Viscose Processes
Source Category in Support of the 2019 Risk and Technology Review
Proposed Rule which is available in the docket for this source
category.
4. How do we conduct the multipathway exposure and risk screening
assessment?
    The EPA conducts a tiered screening assessment examining the
potential for significant human health risks due to exposures via
routes other than inhalation (i.e., ingestion). We first determine
whether any sources in the source categories emit any HAP known to be
persistent and bioaccumulative in the environment, as identified in the
EPA's Air Toxics Risk Assessment Library (see Volume 1, Appendix D, at
https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the MVP source category, we did not identify emissions of any
PB-HAP or lead compounds. Because we did not identify PB-HAP emissions,
no further evaluation of multipathway risk was conducted for this
source category.
    For the CEP source category, we identified PB-HAP emissions of
cadmium compounds, arsenic compounds, lead compounds, and mercury
compounds, so we proceeded to the next step of the evaluation. Except
for lead, the human health risk screening assessment for PB-HAP
consists of three progressive tiers. In a Tier 1 screening assessment,
we determine whether the magnitude of the facility-specific emissions
of PB-HAP warrants further evaluation to characterize human health risk
through ingestion exposure. To facilitate this step, we evaluate
emissions against previously developed screening threshold emission
rates for several PB-HAP that are based on a hypothetical upper-end
screening exposure scenario developed for use in conjunction with the
EPA's Total Risk Integrated Methodology.Fate, Transport, and Ecological
Exposure (TRIM.FaTE) model. The PB-HAP with screening threshold
emission rates are arsenic compounds, cadmium compounds, chlorinated
dibenzodioxins and furans, mercury compounds, and polycyclic organic
matter (POM). Based on the EPA estimates of toxicity and
bioaccumulation potential, these pollutants represent a conservative
list for inclusion in multipathway risk assessments for RTR rules. (See
Volume 1, Appendix D at https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf.) In this assessment, we
compare the facility-specific emission rates of these PB-HAP to the
screening threshold emission rates for each PB-HAP to assess the
potential for significant human health risks via the ingestion pathway.
We call this application of the TRIM.FaTE model the Tier 1 screening
assessment. The ratio of a facility's actual emission rate to the Tier
1 screening threshold emission rate is a ``screening value.''
    We derive the Tier 1 screening threshold emission rates for these
PB-HAP (other than lead compounds) to correspond to a maximum excess
lifetime cancer risk of 1-in-1 million (i.e., for arsenic compounds,
polychlorinated dibenzodioxins and furans and POM) or, for HAP that
cause noncancer health effects (i.e., cadmium compounds and mercury
compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP
or combination of carcinogenic PB-HAP in the Tier 1 screening
assessment exceeds the Tier 1 screening threshold emission rate for any
facility (i.e., the screening value is greater than 1), we conduct a
second

screening assessment, which we call the Tier 2 screening assessment.
The Tier 2 screening assessment separates the Tier 1 combined fisher
and farmer exposure scenario into fisher, farmer, and gardener
scenarios that retain upper-bound ingestion rates.
    In the Tier 2 screening assessment, the location of each facility
that exceeds a Tier 1 screening threshold emission rate is used to
refine the assumptions associated with the Tier 1 fisher and farmer
exposure scenarios at that facility. A key assumption in the Tier 1
screening assessment is that a lake and/or farm is located near the
facility. As part of the Tier 2 screening assessment, we use a U.S.
Geological Survey (USGS) database to identify actual waterbodies within
50 km of each facility and assume the fisher only consumes fish from
lakes within that 50 km zone. We also examine the differences between
local meteorology near the facility and the meteorology used in the
Tier 1 screening assessment. We then adjust the previously-developed
Tier 1 screening threshold emission rates for each PB-HAP for each
facility based on an understanding of how exposure concentrations
estimated for the screening scenario change with the use of local
meteorology and USGS lakes database.
    In the Tier 2 farmer scenario, we maintain an assumption that the
farm is located within 0.5 km of the facility and that the farmer
consumes meat, eggs, dairy, vegetables, and fruit produced near the
facility. We may further refine the Tier 2 screening analysis by
assessing a gardener scenario to characterize a range of exposures,
with the gardener scenario being more plausible in RTR evaluations.
Under the gardener scenario, we assume the gardener consumes home-
produced eggs, vegetables, and fruit products at the same ingestion
rate as the farmer. The Tier 2 screen continues to rely on the high-end
food intake assumptions that were applied in Tier 1 for local fish
(adult female angler at 99th percentile fish consumption of fish \17\)
and locally grown or raised foods (90th percentile consumption of
locally grown or raised foods for the farmer and gardener scenarios
\18\). If PB-HAP emission rates do not result in a Tier 2 screening
value greater than 1, we consider those PB-HAP emissions to pose risks
below a level of concern. If the PB-HAP emission rates for a facility
exceed the Tier 2 screening threshold emission rates, we may conduct a
Tier 3 screening assessment.
---------------------------------------------------------------------------

    \17\ Burger, J. 2002. Daily consumption of wild fish and game:
Exposures of high end recreationists. International Journal of
Environmental Health Research 12:343-354.
    \18\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final).
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
---------------------------------------------------------------------------

    There are several analyses that can be included in a Tier 3
screening assessment, depending upon the extent of refinement
warranted, including validating that the lakes are fishable, locating
residential/garden locations for urban and/or rural settings,
considering plume-rise to estimate emissions lost above the mixing
layer, and considering hourly effects of meteorology and plume rise on
chemical fate and transport (a time-series analysis). If necessary, the
EPA may further refine the screening assessment through a site-specific
assessment.
    In evaluating the potential multipathway risk from emissions of
lead compounds, rather than developing a screening threshold emission
rate, we compare maximum estimated chronic inhalation exposure
concentrations to the level of the current National Ambient Air Quality
Standard (NAAQS) for lead.\19\ Values below the level of the primary
(health-based) lead NAAQS are considered to have a low potential for
multipathway risk.
---------------------------------------------------------------------------

    \19\ In doing so, the EPA notes that the legal standard for a
primary NAAQS--that a standard is requisite to protect public health
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other
things, that the standard provide an ``ample margin of safety to
protect public health''). However, the primary lead NAAQS is a
reasonable measure of determining risk acceptability (i.e., the
first step of the Benzene NESHAP analysis) since it is designed to
protect the most susceptible group in the human population--
children, including children living near major lead emitting
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition,
applying the level of the primary lead NAAQS at the risk
acceptability step is conservative, since that primary lead NAAQS
reflects an adequate margin of safety.
---------------------------------------------------------------------------

    For further information on the multipathway assessment for CEP, see
the Residual Risk Assessment for the Cellulose Ethers Production Source
Category in Support of the Risk and Technology Review 2019 Proposed
Rule, which is available in the docket for this action.
5. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological
Benchmarks
    The EPA conducts a screening assessment to examine the potential
for an adverse environmental effect as required under section
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse
environmental effect'' as ``any significant and widespread adverse
effect, which may reasonably be anticipated, to wildlife, aquatic life,
or other natural resources, including adverse impacts on populations of
endangered or threatened species or significant degradation of
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as
``environmental HAP,'' in its screening assessment: Six PB-HAP and two
acid gases. The PB-HAP included in the screening assessment are arsenic
compounds, cadmium compounds, dioxins/furans, POM, mercury (both
inorganic mercury and methyl mercury), and lead compounds. The acid
gases included in the screening assessment are HCl and HF.
    HAP that persist and bioaccumulate are of particular environmental
concern because they accumulate in the soil, sediment, and water. The
acid gases, HCl and HF, are included due to their well-documented
potential to cause direct damage to terrestrial plants. In the
environmental risk screening assessment, we evaluate the following four
exposure media: Terrestrial soils, surface water bodies (includes
water-column and benthic sediments), fish consumed by wildlife, and
air. Within these four exposure media, we evaluate nine ecological
assessment endpoints, which are defined by the ecological entity and
its attributes. For PB-HAP (other than lead), both community-level and
population-level endpoints are included. For acid gases, the ecological
assessment evaluated is terrestrial plant communities.
    An ecological benchmark represents a concentration of HAP that has
been linked to a particular environmental effect level. For each
environmental HAP, we identified the available ecological benchmarks
for each assessment endpoint. We identified, where possible, ecological
benchmarks at the following effect levels: Probable effect levels,
lowest-observed-adverse-effect level, and no-observed-adverse-effect
level. In cases where multiple effect levels were available for a
particular PB-HAP and assessment endpoint, we use all of the available
effect levels to help us to determine whether ecological risks exist
and, if so, whether the risks could be considered significant and
widespread.
    For further information on how the environmental risk screening
assessment was conducted, including a discussion of the risk metrics
used, how the environmental HAP were identified, and how the ecological
benchmarks were selected, see Appendix 9 of the Residual Risk
Assessment for the

Cellulose Ethers Production Source Category in Support of the Risk and
Technology Review 2019 Proposed Rule, which is available in the docket
for this action.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first
determined whether any facilities in the MVP and CEP source categories
emitted any of the environmental HAP. For the CEP source category, we
identified emissions of cadmium compounds, arsenic compounds, lead
compounds, mercury compounds, and HCl. Because one or more of the
environmental HAP evaluated are emitted by at least one facility in the
source category, we proceeded to the second step of the evaluation. For
the MVP source category, we did not identify emissions of any of the
eight environmental HAP included in the screen. Because we did not
identify environmental HAP emissions from the MVP source category, no
further evaluation of environmental risk was conducted for that
category.
c. PB-HAP Methodology
    The environmental screening assessment includes six PB-HAP, arsenic
compounds, cadmium compounds, dioxins/furans, POM, mercury (both
inorganic mercury and methyl mercury), and lead compounds. With the
exception of lead, the environmental risk screening assessment for PB-
HAP consists of three tiers. The first tier of the environmental risk
screening assessment uses the same health-protective conceptual model
that is used for the Tier 1 human health screening assessment.
TRIM.FaTE model simulations were used to back-calculate Tier 1
screening threshold emission rates. The screening threshold emission
rates represent the emission rate in tons of pollutant per year that
results in media concentrations at the facility that equal the relevant
ecological benchmark. To assess emissions from each facility in the
category, the reported emission rate for each PB-HAP was compared to
the Tier 1 screening threshold emission rate for that PB-HAP for each
assessment endpoint and effect level. If emissions from a facility do
not exceed the Tier 1 screening threshold emission rate, the facility
``passes'' the screening assessment, and, therefore, is not evaluated
further under the screening approach. If emissions from a facility
exceed the Tier 1 screening threshold emission rate, we evaluate the
facility further in Tier 2.
    In Tier 2 of the environmental screening assessment, the screening
threshold emission rates are adjusted to account for local meteorology
and the actual location of lakes in the vicinity of facilities that did
not pass the Tier 1 screening assessment. For soils, we evaluate the
average soil concentration for all soil parcels within a 7.5-km radius
for each facility and PB-HAP. For the water, sediment, and fish tissue
concentrations, the highest value for each facility for each pollutant
is used. If emission concentrations from a facility do not exceed the
Tier 2 screening threshold emission rate, the facility ``passes'' the
screening assessment and typically is not evaluated further. If
emissions from a facility exceed the Tier 2 screening threshold
emission rate, we evaluate the facility further in Tier 3.
    As in the multipathway human health risk assessment, in Tier 3 of
the environmental screening assessment, we examine the suitability of
the lakes around the facilities to support life and remove those that
are not suitable (e.g., lakes that have been filled in or are
industrial ponds), adjust emissions for plume-rise, and conduct hour-
by-hour time-series assessments. If these Tier 3 adjustments to the
screening threshold emission rates still indicate the potential for an
adverse environmental effect (i.e., facility emission rate exceeds the
screening threshold emission rate), we may elect to conduct a more
refined assessment using more site-specific information. If, after
additional refinement, the facility emission rate still exceeds the
screening threshold emission rate, the facility may have the potential
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from
lead, we compared the average modeled air concentrations (from HEM-3)
of lead around each facility in the source category to the level of the
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable
means of evaluating environmental risk because it is set to provide
substantial protection against adverse welfare effects which can
include ``effects on soils, water, crops, vegetation, man-made
materials, animals, wildlife, weather, visibility and climate, damage
to and deterioration of property, and hazards to transportation, as
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the
potential phytotoxicity and reduced productivity of plants due to
chronic exposure to HF and HCl. The environmental risk screening
methodology for acid gases is a single-tier screening assessment that
compares modeled ambient air concentrations (from AERMOD) to the
ecological benchmarks for each acid gas. To identify a potential
adverse environmental effect (as defined in section 112(a)(7) of the
CAA) from emissions of HF and HCl, we evaluate the following metrics:
The size of the modeled area around each facility that exceeds the
ecological benchmark for each acid gas, in acres and square kilometers
(km\2\); the percentage of the modeled area around each facility that
exceeds the ecological benchmark for each acid gas; and the area-
weighted average screening value around each facility (calculated by
dividing the area-weighted average concentration over the 50-km
modeling domain by the ecological benchmark for each acid gas). For
further information on the environmental screening assessment approach,
see Appendix 9 of the Residual Risk Assessment for the Cellulose Ethers
Production Source Category in Support of the Risk and Technology Review
2019 Proposed Rule, which is available in the docket for this action.
6. How do we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine
the risks from the entire ``facility,'' where the facility includes all
HAP-emitting operations within a contiguous area and under common
control. In other words, we examine the HAP emissions not only from the
source category emission points of interest, but also emissions of HAP
from all other emission sources at the facility for which we have data.
For this source category, we conducted the facility-wide assessment
using a dataset compiled from the 2014 NEI. The source category records
of that NEI dataset were removed, evaluated, and updated as described
in section II.C of this preamble: What data collection activities were
conducted to support this action? Once a quality assured source
category dataset was available, it was placed back with the remaining
records from the NEI for that facility. The facility-wide file was then
used to analyze risks due to the inhalation of HAP that are emitted
``facility-wide'' for the populations residing within 50 km of each
facility, consistent with the methods used for the source category
analysis described above. For these facility-wide risk analyses, the
modeled

source category risks were compared to the facility-wide risks to
determine the portion of the facility-wide risks that could be
attributed to the source category addressed in this proposal. We also
specifically examined the facility that was associated with the highest
estimate of risk and determined the percentage of that risk
attributable to the source category of interest. The Residual Risk
Assessment for the Miscellaneous Viscose Processes Source Category in
Support of the Risk and Technology Review 2019 Proposed Rule and the
Residual Risk Assessment for the Cellulose Ethers Production Source
Category in Support of the Risk and Technology Review 2019 Proposed
Rule, available through the docket for this action, provides the
methodology and results of the facility-wide analyses, including all
facility-wide risks and the percentage of source category contribution
to facility-wide risks.
7. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for this proposal. Although
uncertainty exists, we believe that our approach, which used
conservative tools and assumptions, ensures that our decisions are
health and environmentally protective. A brief discussion of the
uncertainties in the RTR emissions datasets, dispersion modeling,
inhalation exposure estimates, and dose-response relationships follows
below. Also included are those uncertainties specific to our acute
screening assessments, multipathway screening assessments, and our
environmental risk screening assessments. A more thorough discussion of
these uncertainties is included in the Residual Risk Assessment for the
Miscellaneous Viscose Processes Source Category in Support of the Risk
and Technology Review 2019 Proposed Rule and the Residual Risk
Assessment for the Cellulose Ethers Production Source Category in
Support of the Risk and Technology Review 2019 Proposed Rule, which are
available in the docket for this action. If a multipathway site-
specific assessment was performed for this source category, a full
discussion of the uncertainties associated with that assessment can be
found in Appendix 11 of that document, Site-Specific Human Health
Multipathway Residual Risk Assessment Report.
a. Uncertainties in the RTR Emissions Datasets
    Although the development of the RTR emissions datasets involved
quality assurance/quality control processes, the accuracy of emissions
values will vary depending on the source of the data, the degree to
which data are incomplete or missing, the degree to which assumptions
made to complete the datasets are accurate, errors in emission
estimates, and other factors. Some of the emission estimates considered
in this analysis are annual totals for certain years, and they do not
reflect short-term fluctuations during the course of a year or
variations from year to year. The estimates of peak hourly emission
rates for the acute effects screening assessment were based on an
emission adjustment factor applied to the average annual hourly
emission rates, which are intended to account for emission fluctuations
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration
estimates associated with any model, including the EPA's recommended
regulatory dispersion model, AERMOD. In using a model to estimate
ambient pollutant concentrations, the user chooses certain options to
apply. For RTR assessments, we select some model options that have the
potential to overestimate ambient air concentrations (e.g., not
including plume depletion or pollutant transformation). We select other
model options that have the potential to underestimate ambient impacts
(e.g., not including building downwash). Other options that we select
have the potential to either under- or overestimate ambient levels
(e.g., meteorology and receptor locations). On balance, considering the
directional nature of the uncertainties commonly present in ambient
concentrations estimated by dispersion models, the approach we apply in
the RTR assessments should yield unbiased estimates of ambient HAP
concentrations. We also note that the selection of meteorology dataset
location could have an impact on the risk estimates. As we continue to
update and expand our library of meteorological station data used in
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant
facilities and emission points, as well as to develop accurate
estimates of the annual emission rates for all relevant HAP, the
uncertainties in our emission inventory likely dominate the
uncertainties in the exposure assessment. Some uncertainties in our
exposure assessment include human mobility, using the centroid of each
census block, assuming lifetime exposure, and assuming only outdoor
exposures. For most of these factors, there is neither an under nor
overestimate when looking at the maximum individual risk or the
incidence, but the shape of the distribution of risks may be affected.
With respect to outdoor exposures, actual exposures may not be as high
if people spend time indoors, especially for very reactive pollutants
or larger particles. For all factors, we reduce uncertainty when
possible. For example, with respect to census-block centroids, we
analyze large blocks using aerial imagery and adjust locations of the
block centroids to better represent the population in the blocks. We
also add additional receptor locations where the population of a block
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from
chronic exposures and noncancer effects from both chronic and acute
exposures. Some uncertainties are generally expressed quantitatively,
and others are generally expressed in qualitative terms. We note, as a
preface to this discussion, a point on dose-response uncertainty that
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment;
namely, that ``the primary goal of EPA actions is protection of human
health; accordingly, as an Agency policy, risk assessment procedures,
including default options that are used in the absence of scientific
data to the contrary, should be health protective'' (EPA's 2005
Guidelines for Carcinogen Risk Assessment, page 1-7). This is the
approach followed here as summarized in the next paragraphs.
    Cancer UREs used in our risk assessments are those that have been
developed to generally provide an upper bound estimate of risk.\20\
That is, they represent a ``plausible upper limit to the true value of
a quantity'' (although this is usually not a true statistical
confidence limit). In some circumstances, the true risk could be as

low as zero; however, in other circumstances the risk could be
greater.\21\ Chronic noncancer RfC and reference dose (RfD) values
represent chronic exposure levels that are intended to be health-
protective levels. To derive dose-response values that are intended to
be ``without appreciable risk,'' the methodology relies upon an
uncertainty factor (UF) approach,\22\ which considers uncertainty,
variability, and gaps in the available data. The UFs are applied to
derive dose-response values that are intended to protect against
appreciable risk of deleterious effects.
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    \20\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \21\ An exception to this is the URE for benzene, which is
considered to cover a range of values, each end of which is
considered to be equally plausible, and which is based on maximum
likelihood estimates.
    \22\ See A Review of the Reference Dose and Reference
Concentration Processes, U.S. EPA, December 2002, and Methods for
Derivation of Inhalation Reference Concentrations and Application of
Inhalation Dosimetry, U.S. EPA, 1994.
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    Many of the UFs used to account for variability and uncertainty in
the development of acute dose-response values are quite similar to
those developed for chronic durations. Additional adjustments are often
applied to account for uncertainty in extrapolation from observations
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all
acute dose-response values are developed for the same purpose, and care
must be taken when interpreting the results of an acute assessment of
human health effects relative to the dose-response value or values
being exceeded. Where relevant to the estimated exposures, the lack of
acute dose-response values at different levels of severity should be
factored into the risk characterization as potential uncertainties.
    Uncertainty also exists in the selection of ecological benchmarks
for the environmental risk screening assessment. We established a
hierarchy of preferred benchmark sources to allow selection of
benchmarks for each environmental HAP at each ecological assessment
endpoint. We searched for benchmarks for three effect levels (i.e., no-
effects level, threshold-effect level, and probable effect level), but
not all combinations of ecological assessment/environmental HAP had
benchmarks for all three effect levels. Where multiple effect levels
were available for a particular HAP and assessment endpoint, we used
all of the available effect levels to help us determine whether risk
exists and whether the risk could be considered significant and
widespread.
    Although we make every effort to identify appropriate human health
effect dose-response values for all pollutants emitted by the sources
in this risk assessment, some HAP emitted by the CEP source category
are lacking dose-response assessments. Accordingly, these pollutants
cannot be included in the quantitative risk assessment, which could
result in quantitative estimates understating HAP risk. To help to
alleviate this potential underestimate, where we conclude similarity
with a HAP for which a dose-response value is available, we use that
value as a surrogate for the assessment of the HAP for which no value
is available. To the extent use of surrogates indicates appreciable
risk, we may identify a need to increase priority for an IRIS
assessment for that substance. We additionally note that, generally
speaking, HAP of greatest concern due to environmental exposures and
hazard are those for which dose-response assessments have been
performed, reducing the likelihood of understating risk. Further, HAP
not included in the quantitative assessment are assessed qualitatively
and considered in the risk characterization that informs the risk
management decisions, including consideration of HAP reductions
achieved by various control options. For the MVP source category, we
have identified appropriate human health effect dose-response values
for all pollutants.
    For a group of compounds that are unspeciated (e.g., glycol
ethers), we conservatively use the most protective dose-response value
of an individual compound in that group to estimate risk. Similarly,
for an individual compound in a group (e.g., ethylene glycol diethyl
ether) that does not have a specified dose-response value, we also
apply the most protective dose-response value from the other compounds
in the group to estimate risk.
e. Uncertainties in Acute Inhalation Screening Assessments
    In addition to the uncertainties highlighted above, there are
several factors specific to the acute exposure assessment that the EPA
conducts as part of the risk review under section 112 of the CAA. The
accuracy of an acute inhalation exposure assessment depends on the
simultaneous occurrence of independent factors that may vary greatly,
such as hourly emissions rates, meteorology, and the presence of a
person. In the acute screening assessment that we conduct under the RTR
program, we assume that peak emissions from the source category and
reasonable worst-case air dispersion conditions (i.e., 99th percentile)
co-occur. We then include the additional assumption that a person is
located at this point at the same time. Together, these assumptions
represent a reasonable worst-case exposure scenario. In most cases, it
is unlikely that a person would be located at the point of maximum
exposure during the time when peak emissions and reasonable worst-case
air dispersion conditions occur simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening
Assessments
    For each source category, we generally rely on site-specific levels
of PB-HAP or environmental HAP emissions to determine whether a refined
assessment of the impacts from multipathway exposures is necessary or
whether it is necessary to perform an environmental screening
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant
concentrations and human exposures for five PB-HAP (dioxins, POM,
mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For
lead, we use AERMOD to determine ambient air concentrations, which are
then compared to the secondary NAAQS standard for lead. Two important
types of uncertainty associated with the use of these models in RTR
risk assessments and inherent to any assessment that relies on
environmental modeling are model uncertainty and input uncertainty.\23\
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    \23\ In the context of this discussion, the term ``uncertainty''
as it pertains to exposure and risk encompasses both variability in
the range of expected inputs and screening results due to existing
spatial, temporal, and other factors, as well as uncertainty in
being able to accurately estimate the true result.
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    Model uncertainty concerns whether the model adequately represents
the actual processes (e.g., movement and accumulation) that might occur
in the environment. For example, does the model adequately describe the
movement of a pollutant through the soil? This type of uncertainty is
difficult to quantify. However, based on feedback received from
previous EPA SAB reviews and other reviews, we are confident that the
models used in the screening assessments are appropriate and state-of-
the-art for the multipathway and environmental screening risk
assessments conducted in support of RTR.

    Input uncertainty is concerned with how accurately the models have
been configured and parameterized for the assessment at hand. For Tier
1 of the multipathway and environmental screening assessments, we
configured the models to avoid underestimating exposure and risk. This
was accomplished by selecting upper-end values from nationally
representative datasets for the more influential parameters in the
environmental model, including selection and spatial configuration of
the area of interest, lake location and size, meteorology, surface
water, soil characteristics, and structure of the aquatic food web. We
also assume an ingestion exposure scenario and values for human
exposure factors that represent reasonable maximum exposures.
    In Tier 2 of the multipathway and environmental screening
assessments, we refine the model inputs to account for meteorological
patterns in the vicinity of the facility versus using upper-end
national values, and we identify the actual location of lakes near the
facility rather than the default lake location that we apply in Tier 1.
By refining the screening approach in Tier 2 to account for local
geographical and meteorological data, we decrease the likelihood that
concentrations in environmental media are overestimated, thereby
increasing the usefulness of the screening assessment. In Tier 3 of the
screening assessments, we refine the model inputs again to account for
hour-by-hour plume rise and the height of the mixing layer. We can also
use those hour-by-hour meteorological data in a TRIM.FaTE run using the
screening configuration corresponding to the lake location. These
refinements produce a more accurate estimate of chemical concentrations
in the media of interest, thereby reducing the uncertainty with those
estimates. The assumptions and the associated uncertainties regarding
the selected ingestion exposure scenario are the same for all three
tiers.
    For the environmental screening assessment for acid gases, we
employ a single-tiered approach. We use the modeled air concentrations
and compare those with ecological benchmarks.
    For all tiers of the multipathway and environmental screening
assessments, our approach to addressing model input uncertainty is
generally cautious. We choose model inputs from the upper end of the
range of possible values for the influential parameters used in the
models, and we assume that the exposed individual exhibits ingestion
behavior that would lead to a high total exposure. This approach
reduces the likelihood of not identifying high risks for adverse
impacts.
    Despite the uncertainties, when individual pollutants or facilities
do not exceed screening threshold emission rates (i.e., screen out), we
are confident that the potential for adverse multipathway impacts on
human health is very low. On the other hand, when individual pollutants
or facilities do exceed screening threshold emission rates, it does not
mean that impacts are significant, only that we cannot rule out that
possibility and that a refined assessment for the site might be
necessary to obtain a more accurate risk characterization for the
source category.
    The EPA evaluates the following HAP in the multipathway and/or
environmental risk screening assessments, where applicable: Arsenic,
cadmium, dioxins/furans, lead, mercury (both inorganic and methyl
mercury), POM, HCl, and HF. These HAP represent pollutants that can
cause adverse impacts either through direct exposure to HAP in the air
or through exposure to HAP that are deposited from the air onto soils
and surface waters and then through the environment into the food web.
These HAP represent those HAP for which we can conduct a meaningful
multipathway or environmental screening risk assessment. For other HAP
not included in our screening assessments, the model has not been
parameterized such that it can be used for that purpose. In some cases,
depending on the HAP, we may not have appropriate multipathway models
that allow us to predict the concentration of that pollutant. The EPA
acknowledges that other HAP beyond these that we are evaluating may
have the potential to cause adverse effects and, therefore, the EPA may
evaluate other relevant HAP in the future, as modeling science and
resources allow.

IV. Analytical Results and Proposed Decisions

A. What are the results of the risk assessment and analyses?

1. MVP Source Category
a. Chronic Inhalation Risk Assessment Results
    Table 2 of this preamble provides an overall summary of the
inhalation risk results of the MVP source category. The results of the
chronic baseline inhalation cancer risk assessment indicate that, based
on estimates of current actual and allowable emissions, the MIR posed
by the source category was estimated to be less than 1-in-1 million.
The risk driver is acetaldehyde emissions from viscose process
equipment. The total estimated cancer incidence from MVP emission
sources based on actual and allowable emission levels is 0.000006
excess cancer cases per year, or one case in every 167,000 years.
Emissions of acetaldehyde contributed 100 percent to this cancer
incidence. Based upon actual or allowable emissions, no people were
exposed to cancer risks greater than or equal to 1-in-1 million.
    The maximum chronic noncancer HI (TOSHI) values for the MVP source
category, based on actual and allowable emissions, were estimated to be
less than 1. Based upon actual and allowable emissions, respiratory
risks were driven by CS2 emissions from viscose process
equipment.

                                                   Table 2--MVP Inhalation Risk Assessment Results \1\
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                                                                                Estimated
                                                                           Maximum     population  at                         Maximum         Maximum
                                                          Number of      individual       increased    Estimated  annual      chronic      refined acute
                   Risk assessment                       facilities      cancer risk       risk of     cancer  incidence     noncancer     noncancer HQ
                                                                       (in 1 million)    cancer >=1-    (cases per year)     TOSHI \3\          \4\
                                                                             \2\        in-1 million
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Baseline Actual Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category......................................               5              <1               0           0.000006            0.05             0.4
Facility-Wide........................................               5               1               0            0.00006            0.05  ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                                              Baseline Allowable Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category......................................               5              <1               0           0.000006            0.05  ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Based on actual, allowable, and facility-wide emissions.
\2\ Maximum individual excess lifetime cancer risk due to HAP emissions from the source category and facility-wide.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the MVP source category is the respiratory system.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which in most cases is the REL. When an HQ exceeds 1, we also show the HQ using the next lowest
  available acute dose-response value. The HQ of 0.4 is based upon an acute ERPG-1.

b. Screening Level Acute Risk Assessment Results
    Worst-case acute HQs were calculated for every HAP for which there
is an acute health benchmark using actual emissions. The maximum
refined off-site acute noncancer HQ value for the MVP source category
was less than 1 from CS2 emissions (based on the acute (1-
hour) ERPG-1 for CS2). It is also important to note that the
highest HQ is based on hourly emissions multiplier for each emission
process group ranging from 1 to 37 times the annual emissions rate.
Acute HQs are not calculated for allowable or whole facility emissions.
    c. Multipathway Risk Screening Results
    The five facilities modeled in the MVP source category did not
report any emissions of lead compounds, carcinogenic PB-HAP (arsenic,
dioxin/furans, and POM compounds) or any noncarcinogenic PB-HAP
(cadmium and mercury). Since, there are no PB-HAP or lead compounds
identified in the emissions inventory for this source category, no
further assessment of multipathway risk was conducted.
d. Environmental Risk Screening Results
    The five facilities modeled in the MVP source category did not
report any emissions of lead compounds, PB-HAP, or any acid gases (HCl
or HF). Since there are no ecological HAP identified in the emissions
inventory for this source category, no further assessment of ecological
risk was conducted.
e. Facility-Wide Risk Results
    Results of the assessment of facility-wide emissions indicate that
none of the five facilities have a facility-wide MIR cancer risk
greater than 1-in-1 million (refer to Table 2). The maximum facility-
wide cancer risk is 1-in-1 million, driven by formaldehyde, cadmium
compounds, and nickel compounds from a non-category fugitive area
source. The total estimated cancer incidence from the whole facility is
0.00006 excess cancer cases per year, or one case in every 16,700
years, with zero people estimated to have cancer risks greater than 1-
in-1 million. The maximum facility-wide chronic noncancer TOSHI is
estimated to be less than 1, driven by source category emissions of
CS2 from viscose process equipment.

2. CEP Source Category

a. Chronic Inhalation Risk Assessment Results
    Table 3 of this preamble provides an overall summary of the
inhalation risk results of the CEP source category. The results of the
chronic baseline inhalation cancer risk assessment indicate that, based
on estimates of current actual and allowable emissions, the MIR posed
by the source category was estimated to be 80-in-1 million. The risk
driver is from emissions of ethylene oxide from cellulose ether process
equipment used to produce hydroxyethyl cellulose (HEC). The total
estimated cancer incidence from CEP emission sources based on actual
and allowable emission levels is 0.01 excess cancer cases per year, or
one case in every 100 years. Emissions of ethylene oxide contributed 99
percent to this cancer incidence based upon actual emissions. Based