[Federal Register Volume 86, Number 6 (Monday, January 11, 2021)]
[Proposed Rules]
[Pages 1868-1890]
[FR Doc No: 2021-00250]

=======================================================================
-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0572; FRL-10017-90-OAR]
RIN 2060-AU57

National Emission Standards for Hazardous Air Pollutants:
Flexible Polyurethane Foam Fabrication Operations Residual Risk and
Technology Review and Flexible Polyurethane Foam Production and
Fabrication Area Source Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: This action presents the proposed results of the U.S.
Environmental Protection Agency's (EPA's) residual risk and technology
review (RTR) required under the Clean Air Act (CAA) for the National
Emission Standards for Hazardous Air Pollutants (NESHAP) for major
source Flexible Polyurethane Foam Fabrication Operations, initially
promulgated in 2003. Pursuant to the CAA, this action also presents the
proposed results of the technology review for the NESHAP for two area
source categories, Flexible Polyurethane Foam Production and Flexible
Polyurethane Foam Fabrication, which are combined in one subpart
initially promulgated in 2007. In this action, the EPA is proposing to
establish a numeric emission limit for one major source subcategory;
remove exemptions for periods of startup, shutdown, and malfunction
(SSM) and specify that the emissions standards apply at all times;
require periodic performance tests; and require electronic reporting of
performance test results and compliance reports. Implementation of
these proposed rules is not expected to result in significant changes
to the hazardous air pollutant (HAP) emissions from affected facilities
in these three source categories or to human health impacts or
environmental impacts associated with those emissions. However, this
action, if finalized, would result in improved monitoring, compliance,
and implementation of the existing standards and codify existing
industry practices to prevent backsliding.

DATES: Comments. Comments must be received on or before February 25,
2021. 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 February 10, 2021.
    Public hearing: If anyone contacts us requesting a public hearing
on or before January 19, 2021, we will hold a virtual public hearing.
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-2020-0572 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-2020-0572- in the subject line of the message.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2020-0572.
     Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2020-0572 EPA 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. Out of an abundance of caution
for members of the public and our staff, the EPA Docket Center and
Reading Room are closed to the public, with limited exceptions, to
reduce the risk of transmitting COVID-19. Our Docket Center staff will
continue to provide remote customer service via email, phone, and
webform. We encourage the public to submit comments via https://www.regulations.gov/ or email, as there may be a delay in processing
mail and faxes. Hand deliveries and couriers may be received by
scheduled appointment only. For further information on EPA Docket
Center services and the current status, please visit us online at
https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Dr. Tina Ndoh, Sector Policies and Programs Division
(D243-04), 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. Chris Sarsony,
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: (919)
541-4843; fax number:<PHONE_NUMBER>; and email address:
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    Participation in virtual public hearing. Please note that the EPA
is deviating from its typical approach for public hearings because the
President has declared a national emergency. Due to the current Centers
for Disease Control and Prevention (CDC) recommendations, as well as
state and local orders for social distancing to limit the spread of
COVID-19, the EPA cannot hold in-person public meetings at this time.
    To request a virtual public hearing, contact the public hearing
team at<PHONE_NUMBER> or by email at<EMAIL_ADDRESS>If
requested, the virtual hearing will be held on January 26, 2021. The
hearing will convene at 9:00 a.m. Eastern Time (ET) and will conclude
at 3:00 p.m. ET. The EPA may close a session 15 minutes after the last
pre-registered speaker has testified if there are no additional
speakers. The EPA will announce further details at https://www.epa.gov/stationary-sources-air-pollution/flexible-polyurethane-foam-fabrication-operations-national-emission.
    Upon publication of this document in the Federal Register, the EPA
will begin pre-registering speakers for the hearing, if a hearing is
requested. To register to speak at the virtual hearing, please use the
online registration form available at https://www.epa.gov/stationary-sources-air-pollution/flexible-polyurethane-foam-fabrication-operations-national-emission or contact the public hearing team at
(888) 372-8699 or by email at<EMAIL_ADDRESS>The last day
to pre-register to speak at the hearing will be January 25, 2021. Prior
to the hearing, the EPA will post a general agenda that will list pre-
registered speakers in approximate order at: https://www.epa.gov/stationary-sources-air-pollution/flexible-polyurethane-foam-fabrication-operations-national-emission.
    The EPA will make every effort to follow the schedule as closely as
possible on the day of the hearing; however, please plan for the
hearings to run either ahead of schedule or behind schedule.
    Each commenter will have 5 minutes to provide oral testimony. The
EPA encourages commenters to provide the EPA with a copy of their oral
testimony electronically (via email) by emailing it to
<EMAIL_ADDRESS>The EPA also recommends submitting the text of your
oral testimony as written comments to the rulemaking docket.
    The EPA may ask clarifying questions during the oral presentations
but will not respond to the presentations at that time. Written
statements and supporting information submitted during the comment
period will be considered with the same weight as oral testimony and
supporting information presented at the public hearing.
    Please note that any updates made to any aspect of the hearing will
be posted online at https://www.epa.gov/stationary-sources-air-pollution/flexible-polyurethane-foam-fabrication-operations-national-emission. While the EPA expects the hearing to go forward as set forth
above, please monitor our website or contact the public hearing team at
(888) 372-8699 or by email at<EMAIL_ADDRESS>to determine if
there are any updates. The EPA does not intend to publish a document in
the Federal Register announcing updates.
    If you require the services of a translator or a special
accommodation such as audio description, please pre-register for the
hearing with the public hearing team and describe your needs by January
19, 2021. The EPA may not be able to arrange accommodations without
advanced notice.
    Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2020-0572. All documents in the docket are
listed in https://www.regulations.gov/. Although listed, some
information is not publicly available, e.g., Confidential Business
Information (CBI) 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. With the exception of such material, publicly available docket
materials are available electronically in Regulations.gov.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2020-0572. 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 electronically any information that you consider
to be CBI or other information whose disclosure is restricted by
statute. 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.
    The EPA is temporarily suspending its Docket Center and Reading
Room for public visitors, with limited exceptions, to reduce the risk
of transmitting COVID-19. Our Docket Center staff will continue to
provide remote customer service via email, phone, and webform.

We encourage the public to submit comments via https://www.regulations.gov/ as there may be a delay in processing mail and
faxes. Hand deliveries or couriers will be received by scheduled
appointment only. For further information and updates on EPA Docket
Center services, please visit us online at https://www.epa.gov/dockets.
    The EPA continues to carefully and continuously monitor information
from the CDC, local area health departments, and our Federal partners
so that we can respond rapidly as conditions change regarding COVID-19.
    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-2020-0572. Note that
written comments containing CBI and submitted by mail may be delayed
and no hand deliveries will be accepted.
    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:

AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-3 model
ATSDR Agency for Toxic Substances and Disease Registry
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CDC Centers for Disease Control and Prevention
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting
CFR Code of Federal Regulations
EPA Environmental Protection Agency
ERPG emergency response planning guideline
ERT Electronic Reporting Tool
GACT generally available control technology
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-3 Human Exposure Model, Version 1.5.5
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
IRIS Integrated Risk Information System
km kilometer
MACT maximum achievable control technology
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
NAICS North American Industry Classification System
NATA National Air Toxics Assessment
NEI National Emissions Inventory
NESHAP national emission standards for hazardous air pollutants
NSR New Source Review
OAQPS Office of Air Quality Planning and Standards
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PDF portable document format
POM polycyclic organic matter
ppm parts per million
RBLC Reasonably Available Control Technology, Best Available Control
Technology, and Lowest Achievable Emission Rate Clearinghouse
REL reference exposure level
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SDS safety data sheets
SSM startup, shutdown, and malfunction
TDI toluene diisocyanate
TOSHI target organ-specific hazard index
tpy tons per year
TRI Toxics Release Inventory
TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and
Ecological Exposure model
UF uncertainty factor
URE unit risk estimate

    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 are the source categories and how do the current NESHAP
regulate their 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?
    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 actions are we taking pursuant to CAA sections 112(d)(2)
and 112(d)(3) for the Flexible Polyurethane Foam Fabrication
Operations source category?
    B. What are the results of the risk assessment and analyses for
the Flexible Polyurethane Foam Fabrication Operations source
category?
    C. What are our proposed decisions regarding risk acceptability,
ample margin of safety, and adverse environmental effect?
    D. What are the results and proposed decisions based on our
technology review for the Flexible Polyurethane Foam Fabrication
Operations major source category and for the Flexible Polyurethane
Foam Production and Fabrication area source categories?
    E. What other actions are we proposing?
    F. 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 Regulations 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)
    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?

    The source categories that are the subject of this proposal are
Flexible Polyurethane Foam Fabrication Operations Major Sources
regulated under 40 CFR part 63, subpart MMMMM, and Flexible
Polyurethane Foam Production and Flexible Polyurethane Foam Fabrication
Area Sources, regulated under 40 CFR part 63, subpart OOOOOO. The North
American Industry Classification System (NAICS) code for fabricators of
flexible polyurethane foam industry is 326150. This list of categories
and NAICS codes 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. Federal, state, local, and
tribal government entities would not be affected by this proposed
action.
    The Flexible Polyurethane Foam Fabrication Operations major source
category was added to the EPA's HAP source category list in 1996. (61
FR 28197, June 4, 1996.) The NESHAP for that major source category, 40
CFR part 63, subpart MMMMM, was promulgated in 2003. (68 FR 18062,
April 14, 2003.) The Flexible Polyurethane Foam Fabrication area source
category was added to the EPA's HAP source category list in 1999. (64
FR 38706, July 19, 1999.) The Flexible Polyurethane Foam Production
area source category was added to the EPA's HAP source category list in
2002. (67 FR 70427, November 22, 2002.) The Flexible Polyurethane Foam
Production major source category, Part 63, subpart III, was included on
the EPA's initial HAP source category list. (57 FR 31576, July 16,
1992.) The maximum achievable control technology (MACT) standards for
subpart III were initially promulgated in 1998. (63 FR 53980, October
7, 1998.) The EPA established one area source NESHAP at 40 CFR part 63,
subpart OOOOOO, that applies to the two area source categories due to
similarity of their operations and because they are often collocated.
(72 FR 38864, July 16, 2007.)
    The Flexible Polyurethane Foam Fabrication Operations major source
category and the Flexible Polyurethane Foam Fabrication area source
category include facilities engaged in cutting, gluing, and/or
laminating pieces of flexible polyurethane foam. Those source
categories include fabrication operations that are collocated with foam
production plants as well as those located offsite from foam production
plants. Emissions from foam fabrication primarily result from the
lamination of polyurethane foam to adhere foam to other substrates and
from the use of HAP-based adhesives in the gluing process. The Flexible
Polyurethane Foam Production area source category includes facilities
that manufacture foam made from a polymer containing a plurality of
carbamate linkages in the chain backbone (polyurethane). Polyurethane
is commonly made by reacting a polyisocyanate with an organic
polyhydroxyl material in the presence of water. Application of blowing
agents, catalysts, surfactants, and fillers transform the polyurethane
into a foam with specialized properties.
    This proposed action addresses the major source NESHAP that applies
to the Flexible Polyurethane Foam Fabrication Operations major source
category and also addresses the area source NESHAP that applies to the
Flexible Polyurethane Foam Production area source category and the
Flexible Polyurethane Foam Fabrication area source category.

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/stationary-sources-air-pollution/flexible-polyurethane-foam-fabrication-operations-national-emission. 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.
    The proposed changes to the CFR that would be necessary to
incorporate the changes proposed in this action are set out in an
attachment to the memorandum titled Proposed Regulation Edits for 40
CFR Part 63, subparts MMMMM and OOOOOO, available in the docket for
this action (Docket ID No. EPA-HQ-OAR-2020-0572). This document
includes the specific proposed amendatory language for revising the CFR
and, for the convenience of interested parties, a redline version of
the regulations. Following signature by the EPA Administrator, the EPA
will also post a copy of this memorandum and the attachment to https://www.epa.gov/stationary-sources-air-pollution/flexible-polyurethane-foam-fabrication-operations-national-emission.

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 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 and revise the
standards as necessary taking into account any ``developments in
practices, processes, or control technologies.'' 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 proposed rule (Docket ID No.
EPA-HQ-OAR-2020-0572).
    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.''
In certain instances, as provided in CAA section 112(h), the EPA may
set work practice standards in lieu of numerical emission standards.
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. 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 pursuant 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 Residual 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 (D.C. 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 at 38045). 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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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). The EPA is required to
address regulatory gaps, such as missing standards for listed air
toxics known to be emitted from the source category. Louisiana
Environmental Action Network (LEAN) v. EPA, 955 F.3d 1088 (D.C. Cir.
2020). Section 112(k)(3)(B) of the CAA required the EPA to identify at
least 30 HAP that pose the greatest potential health threat in urban
areas, and CAA section 112(c)(3) requires the EPA to regulate the area
source categories that represent 90 percent of the emissions of the 30
``listed'' HAP (``urban HAP'').

B. What are the source categories and how do the current NESHAP
regulate their HAP emissions?

    For both the Flexible Polyurethane Foam Fabrication Operations
major source category and the Flexible Polyurethane Foam Fabrication
area source category, operations involve cutting, bonding, and/or
laminating pieces of flexible polyurethane foam together or to other
substrates. Typical bonding techniques include gluing, taping, and
flame lamination. In years preceding the listing of the flexible
polyurethane foam fabrication major and area source categories, some
foam fabrication operations may have used methylene chloride-based
adhesives to adhere pieces of foam together; however, the industry no
longer uses any methylene chloride-based adhesives. Most foam
fabrication adhesives are applied by workers using spray guns.
Application of adhesives is typically performed in large open rooms,
with workstations spaced along a conveyor that moves the pieces of foam
to be glued together. Loop slitter adhesive use is a specialized type
of foam fabrication adhesive use. Loop slitters are equipment used at
slabstock foam production and/or fabrication facilities to slice large
foam ``buns'' into thin sheets. Adhesive is used to attach the ends of
the foam buns to one another before they are mounted on the loop
slitter. The amount of adhesive used for loop slitters is relatively
low because the adhesive is not applied continuously, just once or
twice per shift when the foam buns are loaded onto the loop slitter.
Flame lamination refers to the bonding of foam to any substrate (e.g.,
fabric, foam, plastic) where the bonding agent is scorched or melted
foam. Thin sheets of foam are passed under a flame which scorches the
foam surface and makes it sticky. The tacky foam sheet is then applied
and adhered to a substrate.
    The Flexible Polyurethane Foam Production area source category
includes facilities that manufacture foam made from polyurethanes,
which are in the class of compounds called ``reaction polymers.''
Application of blowing agents, catalysts, surfactants, and fillers
transforms the polyurethane into a foam with specialized properties.
There are three types of polyurethane foam production facilities:
Slabstock flexible polyurethane foam (slabstock foam), molded flexible
polyurethane foam (molded foam), and rebond foam.

Slabstock foam is produced in large continuous buns that are then cut
into the desired size and shape. Slabstock foam is used in a wide
variety of applications, including furniture and mattresses. Molded
foam is produced by ``shooting'' the foam mixture into a mold of the
desired shape and size. Molded foam is used in office furniture,
automobile seats, novelties, and many other applications. Rebond foam
is made from scrap foam that is converted into a material primarily
used for carpet underlay.
    The EPA estimates that there are 32 facilities currently subject to
the area source standards, of which approximately 20 are believed to be
owned by small businesses.
    The EPA promulgated MACT standards for major source Flexible
Polyurethane Foam Fabrication Operations facilities in 2003 under 40
CFR part 63, subpart MMMMM. The standards apply to major sources of HAP
at existing and new flexible polyurethane foam fabrication facilities.
Because of their potential to generate HAP emissions, the processing
units of interest at foam fabrication facilities are loop slitters and
flame lamination units. The MACT standards for Flexible Polyurethane
Foam Fabrication Operations require HAP emissions reductions and
control for new flame lamination units and prohibit use of HAP-based
adhesives in new and existing loop slitting operations. For new flame
lamination units, a 90-percent reduction in HAP emissions is required.
For existing flame lamination units, there are currently no MACT
emission limits. For new and existing loop slitters, the MACT standards
prohibit use of any adhesive containing 5 percent or more (by weight)
of total HAP. The EPA estimates that there are currently three
facilities subject to subpart MMMMM--two in Indiana, and one in New
Mexico.
    Both the Flexible Polyurethane Foam Production and Flexible
Polyurethane Fabrication Operations area source categories were listed
for regulation due to emissions of the urban HAP methylene chloride. At
the time of the initial area source standards promulgation, methylene
chloride was the only urban HAP used at foam production and foam
fabrication facilities. Now, however, there are no known urban HAP used
at foam production and foam fabrication facilities. In the past,
slabstock foam production facilities sometimes used methylene chloride
as an auxiliary blowing agent to control the density and other
properties of the foam as it expanded during the pouring process.\2\
Methylene chloride was also sometimes used as an equipment cleaner, in
particular for mix heads. A small number of molded and rebond foam
facilities used methylene chloride in mold release agents, and some
molded foam facilities used it as a mixhead cleaner. Foam fabricators
used methylene chloride-based adhesives to adhere pieces of foam to one
another. Flame laminators have never used methylene chloride and, as
such, are not regulated by the area source standards.
---------------------------------------------------------------------------

    \2\ Other regulations address methylene chloride. For example,
the EPA listed methylene chloride as an unacceptable (prohibited)
blowing agent for use in flexible polyurethane under section 612 of
the CAA (81 FR 86778, December 1, 2016).
---------------------------------------------------------------------------

    In 2007, the EPA promulgated GACT standards for the Flexible
Polyurethane Foam Production area source category and the Flexible
Polyurethane Foam Fabrication area source category together under 40
CFR part 63, subpart OOOOOO. The GACT standards required that methylene
chloride be significantly reduced or eliminated from slabstock foam
production, molded foam release agents, equipment cleaning, rebond foam
mold release agents, and from foam fabrication adhesive use. Although
both area source categories were listed for regulation due to emissions
of the urban HAP methylene chloride, the EPA finds that methylene
chloride is no longer used within either source category.

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

    For the Flexible Foam Fabrication Operations NESHAP RTR, the EPA
used emissions and supporting data from the 2017 and 2014 National
Emissions Inventory (NEI), 2018 and 2019 Toxics Release Inventory (TRI)
data, and 2014 stack test data from one facility to develop the model
input files for the residual risk assessments for major source flexible
foam fabrication facilities.
    The NEI is a database that contains information about sources that
emit criteria air pollutants, their precursors, and HAP. The database
includes estimates of annual air pollutant emissions from point,
nonpoint, and mobile sources in the 50 states, the District of
Columbia, Puerto Rico, and the U.S. Virgin Islands. The EPA collects
this information and releases an updated version of the NEI database
every 3 years. The NEI includes data necessary for conducting risk
modeling, including annual HAP emissions estimates from individual
emission sources at facilities and the related emissions release
parameters. In certain cases, we contacted state inventory compilers
and facility owners or operators to confirm and clarify the sources of
emissions, emissions estimates, and release parameters that were
reported in the NEI.
    The TRI is a resource for learning about toxic chemical releases
and pollution prevention activities reported by industrial and federal
facilities. The TRI tracks the management of certain toxic chemicals
that may pose a threat to human health and the environment. U.S.
facilities in different industry sectors must report annually how much
of each chemical is released to the environment and/or managed through
recycling, energy recovery, and treatment.\3\
---------------------------------------------------------------------------

    \3\ Available at https://www.epa.gov/toxics-release-inventory-tri-program.
---------------------------------------------------------------------------

    Additional information on the development of the modeling file can
be found in Appendix 1 to the Residual Risk Assessment for the Flexible
Polyurethane Foam Fabrication Operations Source Category in Support of
the 2020 Risk and Technology Review Proposed Rule, which is available
in the docket for this proposed rule (Docket ID No. EPA-HQ-OAR-2020-
0572).
    For the Flexible Foam Production and Fabrication area source
standards, we relied on information provided by industry to determine
whether any urban HAP were emitted from the regulated facilities.
Through industry meetings and email and telephone conversations, the
EPA found that there are no additional urban HAP emitted from flexible
foam production and fabrication facilities subject to area source
standards. Detailed information of the technology review can be found
in the memorandum titled Technology Review for the Flexible
Polyurethane Foam Production and Fabrication Area Source Categories,
which is available in the docket for this proposed rule (Docket ID No.
EPA-HQ-OAR-2020-0572).
    The Flexible Polyurethane Foam Production and Flexible Polyurethane
Foam Fabrication MACT standards were promulgated in 1998 and 2003
respectively. Since that time, the EPA has developed air toxics
regulations for a number of additional source categories that emit HAP
from the same types of emission sources that are present in the
Flexible Polyurethane Foam Production and Fabrication source
categories. In air toxic regulatory actions carried out subsequent to
the initial MACT standard development for these source categories, the
EPA has consistently evaluated any new practices, processes, and
control technologies. A review of

these initial and subsequent air toxics regulations, including
supporting documentation used in the rulemakings, was conducted to
determine whether any practices, processes, or control technologies
could be applied to the Flexible Foam Fabrication source category.
    One potential development in practices, processes, and control
technologies was identified through the review of other air toxics
regulations, which is discussed further in section IV.D of this
document.

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

    For the risk review portion of the RTR, we reviewed facility
permits for the three major sources subjected to the Flexible
Polyurethane Foam Fabrication Operations NESHAP. Facility permits
provide data on maximum allowable emissions and other relevant
production and emission factors.
    For the technology review portion of the RTR, we collected
information from the Reasonably Available Control Technology, Best
Available Control Technology, and Lowest Achievable Emission Rate
Clearinghouse (RBLC) to identify developments in practices, processes,
and control technologies since the MACT standards were developed. The
RBLC is a database that contains case-specific information on air
pollution technologies that have been required to reduce the emissions
of air pollutants from stationary sources. Under the EPA's New Source
Review (NSR) program, if a facility is planning new construction or a
modification that will increase the air emissions above certain defined
thresholds, an NSR permit must be obtained. The RBLC promotes the
sharing of information among permitting agencies and aids in case-by-
case determinations for NSR permits. We examined information contained
in the RBLC to determine what technologies are currently used for these
source categories to reduce air emissions. Additional information about
these data collection activities for the technology reviews is
contained in the technology review memorandum titled Technology Review
for the Flexible Polyurethane Foam Fabrication Operations Source
Category, which is available in the docket for this proposed rule
(Docket ID No. EPA-HQ-OAR-2020-0572).
    The RBLC provides several options for searching the permit database
on-line to locate applicable control technologies. Our initial search
of the RBLC specified processes in polyurethane foam products
manufacturing, with permits dating back to 2001. This search did not
provide any results for foam fabrication operations. Further searches
of the database were conducted based on relevant keywords. The search
included all available data fields, which among others, included the
following:
     RBLC ID;
     Facility Name and State;
     Permit Date;
     Process name;
     Throughput;
     Pollutant;
     Control technology;
     Percent efficiency of control; and
     Pollutants/Compliance Notes.

The results of this search are presented in Appendix 1 of the
Technology Review for the Flexible Polyurethane Foam Manufacturing
Source Category. As shown in Appendix 1, no control technologies more
stringent than the Flexible Polyurethane Foam NESHAP were identified
through this search.
    Two of the three facilities subject to major source standards have
loop slitter operations and use adhesives. Both facilities provided the
EPA with safety data sheets (SDS) for the adhesives in use. Those SDS
were used to determine chemical composition and potential HAP emissions
from the adhesives. Additional background information on adhesive use
and regulation was collected through review of other NESHAP in similar
industrial sectors. Specifically, we searched for other NESHAP
regulating HAP emissions from coatings and adhesives and compared the
stringency of those standards to the existing requirements for HAP
adhesives for loop slitters. Data from the SDS provided and the NESHAP
for similar source categories were also used in the technology
evaluation for the Flexible Polyurethane Foam Fabrication Operations
NESHAP. The findings for the technology review are discussed further in
section IV.D of this preamble.

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.
    In this proposed action, pursuant to CAA section 112(f), the EPA is
conducting a risk review for the major source NESHAP (40 CFR part 63,
subpart MMMMM) MACT standards for Flexible Polyurethane Foam
Fabrication Operations. Consistent with the provision regarding
alternative standards for area sources in CAA section 112(d)(5), the
risk review does not cover the NESHAP for area sources. Therefore, the
discussions of risk assessment methods and modeling analyses described
in the following paragraphs only apply to the major source category.
    However, pursuant to CAA section 112(d)(6), the EPA is proposing
the technology review for both the major source NESHAP and the area
source NESHAP (40 CFR part 63, subpart OOOOOO). Therefore, the
discussions in the paragraphs below regarding how the EPA conducted the
technology reviews apply to both major sources and area sources.

A. How do we consider risk in our decision-making?

    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 at
38046). 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 emissions of HAP
that are carcinogens 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 explanation in
the EPA's response to comments on our policy under the Benzene NESHAP:
---------------------------------------------------------------------------

    \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.

    The 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''.

(54 FR at 38057). 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 category under
review, mobile source emissions, natural source emissions, persistent
environmental pollution, or atmospheric transformation in the vicinity
of the sources in the category.
    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\
---------------------------------------------------------------------------

    \5\ Recommendations of the SAB Risk and Technology Review
Methods 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. 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 primarily 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. We also review
the NESHAP and the available data to determine if there are any
unregulated emissions of HAP within the source category and evaluate
this data for use in developing new emission standards. 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.B 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 proposed rule
contains the following document that provides more information on the
risk assessment inputs and models: Residual Risk Assessment for the
Flexible Polyurethane Foam Fabrication Operations Source Category in
Support of the 2020 Risk and Technology Review Proposed Rule. The
methods used to assess risk (as described in the seven 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. Available at: https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions
release characteristics?
    The actual emissions and the emission release characteristics for
each facility were obtained primarily from either the 2014 NEI or the
2017 NEI; most data were obtained from the 2017 NEI, unless a facility
was not included in that base year file, in which case the 2014 NEI
data were used. In one instance, a facility was contacted to confirm
emissions that appeared to be outliers because they were inconsistent
with our understanding of the industry. That facility provided a test
report containing data that were more consistent with our understanding
of emissions from the industry and were ultimately used as actual
emissions for the risk modeling file. Additional information on the
development of the modeling file for the Flexible Polyurethane Foam
Fabrication Operations source category, including the development of
the actual emissions and emissions release characteristics, can be
found in the memorandum, Emissions Data for the National Emission
Standards for Hazardous Air Pollutants for Flexible Polyurethane Foam
Fabrication Operations, which is available in the respective docket for
this action.
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 19992, 19998 and 19999, April 15, 2005) and in the
proposed and final Hazardous Organic NESHAP RTR (71 FR 34421, 34428,
June 14, 2006, and 71 FR 76603, 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).
    For the Flexible Polyurethane Foam Fabrication Operations source
category, allowable emissions were assumed to be equal to actual
emissions. For the subcategory of flame laminators, there currently are
no emissions limits for existing sources, and there have been no new
sources since the promulgation of the standards. Therefore, we conclude
that the emissions that are allowed under the existing standards are
equal to actual emissions. For the loop slitter subcategory, there were
no HAP emissions from the adhesive, and we are not aware of any HAP-
based substitutes that could be used in place of current industry
practice; therefore, we again conclude that allowable emissions would
be equal to actual emissions, which in this case are zero.
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 major source category addressed in this
proposal were estimated using the Human Exposure Model (HEM-3).\7\ 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.
---------------------------------------------------------------------------

    \7\ 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.\8\ 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 \9\ 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.
---------------------------------------------------------------------------

    \8\ 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).
    \9\ 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 major 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) 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 \10\ 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.
---------------------------------------------------------------------------

    \10\ 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. 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,\11\ we
revised 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 Residual Risk Assessment for Flexible Polyurethane Foam
Fabrication Operations Source Category in Support of the 2020 Risk and
Technology Review Proposed Rule and in Appendix 5 of the report:
Technical Support Document for Acute Risk Screening Assessment. This
revised approach has been used in this proposed rule and in all other
RTR rulemakings proposed on or after June 3, 2019.
---------------------------------------------------------------------------

    \11\ 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.
---------------------------------------------------------------------------

    To assess the potential acute risk to the maximally exposed
individual, we use the peak hourly emission rate for each emission
point,\12\ 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.
---------------------------------------------------------------------------

    \12\ 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
Flexible Polyurethane Foam Fabrication Operations Source Category in
Support of the 2020 Risk and Technology Review Proposed Rule and in
Appendix 5 of the report: 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.'' \13\ 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 represent
threshold exposure limits for the general public and are applicable to
emergency exposures ranging from 10 minutes to 8 hours.\14\ 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.
---------------------------------------------------------------------------

    \13\ 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.
    \14\ 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.'' \15\ 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.
---------------------------------------------------------------------------

    \15\ 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).
    For this source category, we used a default multiplier of 10 to
provide a conservatively high estimate of acute effects.
    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. 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.
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 category 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 Flexible Polyurethane Foam
Fabrication Operations source category, we did not identify emissions
of any PB-HAP. Because we did not identify PB-HAP emissions, no further
evaluation of multipathway risk was conducted for this source category.
    For further information on the multipathway assessment approach,
see the Residual Risk Assessment for the Flexible Polyurethane Foam
Fabrication Operations Source Category in Support of the 2020 Risk and
Technology Review 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, polycyclic organic matter
(POM), mercury (both inorganic mercury and methyl mercury), and lead
compounds. The acid gases included in the screening assessment are
hydrochloric acid (HCl) and hydrogen fluoride (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 Flexible Polyurethane Foam Fabrication Operations
Source Category in Support of the 2020 Risk and Technology Review
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 Flexible Polyurethane Foam
Fabrication Operations source category emitted any of the environmental
HAP. For the Flexible Polyurethane Foam Fabrication Operations source
category, we identified emissions of HCl. Because one or more of the
environmental HAP evaluated emitted HCl by at least one facility in the
source category, we proceeded to the second step of the evaluation.
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. For the
Flexible Polyurethane Foam Fabrication Operations source category, we
did not identify emissions of any PB-HAP. Because we did not identify
PB-HAP emissions, no further evaluation of PB-HAP for the environmental
risk assessment was conducted for this source category.
    For further information on the PB-HAP environmental assessment
approach, see the Residual Risk Assessment for the Flexible
Polyurethane Foam Fabrication Operations Source Category in Support of
the 2020 Risk and Technology Review Proposed Rule, available in the
docket for this proposed rule (Docket ID No. EPA-HQ-OAR-2020-0572).
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;
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 Flexible Polyurethane Foam
Fabrication Operations Source Category in Support of the 2020 Risk and
Technology Review 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 and 2017 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 Flexible Polyurethane
Foam Fabrication Operations Source Category in Support of the 2020 Risk
and Technology Review 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 dataset, 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
Flexible Polyurethane Foam Fabrication Operations Source Category in
Support of the 2020 Risk and Technology Review Proposed Rule, which is
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 Dataset
    Although the development of the RTR emissions dataset 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. The emission estimates considered in this
analysis generally 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 MIR 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'' (the 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.\16\ 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.\17\ 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,\18\ 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.
---------------------------------------------------------------------------

    \16\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \17\ 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.
    \18\ 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.
---------------------------------------------------------------------------

    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.
    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 actual 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--
Total Risk Integrated Methodology.Fate, Transport, and Ecological
Exposure model (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 National Ambient Air Quality
Standards 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.\19\
---------------------------------------------------------------------------

    \19\ 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.
---------------------------------------------------------------------------

    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 RTRs.
    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 actions are we taking pursuant to CAA sections 112(d)(2) and
112(d)(3) for the Flexible Polyurethane Foam Fabrication Operations
source category?

    We are proposing pursuant to CAA section 112(d)(2) and (3) to
establish a numeric limit for HCl emissions from existing flame
laminators. The results and proposed decisions based on the analyses
performed pursuant to CAA section 112(d)(2) and (3) are presented
below.
    For the Flexible Polyurethane Foam Fabrication Operations source
category, there are four unregulated existing source flame laminators
at two facilities. For major sources, the EPA is required to set
technology-based standards that reflect the maximum reductions of HAP
achievable (after considering cost, energy requirements, and non-air
health and environmental impacts) and are commonly referred to as MACT
standards. Furthermore, CAA section 112(d)(3)(B) provides that MACT
shall not be less stringent than ``the average emission limitation
achieved by the best performing five sources (for which the
Administrator has or could reasonably obtain emissions information) in
the category for categories with fewer than 30 sources. In this
category, the MACT floor for existing sources is the average (or mean)
of the four known flame lamination sources. However, emissions data for
HCl emissions from only one of these units is available. As this is the
only unit of which we are aware that has had emissions testing
conducted for HCl, the proposed MACT floor is based on the HCl data for
this unit. In order to determine the level of the MACT floor, the Upper
Prediction Limit method was used in order to account for variability in
flame laminator emissions performance, and the MACT floor was
calculated at 1.45 pounds per hour of HCl.\20\
---------------------------------------------------------------------------

    \20\ MACT Floor and Beyond-the-Floor Analysis for Existing Flame
Laminators in the Flexible Polyurethane Foam Fabrication Source
Category (EPA-HQ-OAR-2020-0572).
---------------------------------------------------------------------------

    When establishing an emission standard pursuant to section 112 of
the CAA, the EPA must also determine whether to control emissions
``beyond the floor'' after considering the costs, non-air quality
health and environmental impacts, and energy requirements of such more
stringent control. For the existing source flame laminators, the EPA
evaluated whether a beyond-the-floor emissions limit would be
appropriate; specifically, we evaluated whether the incremental
emissions reduction achievable with a venturi scrubber would be cost
effective. The venturi scrubber was the only control technology in use
at flame lamination sources that was identified by the EPA with the
initial promulgation of the NESHAP, and no other developments in
control technologies were identified in the review of these standards.
The EPA's previous cost estimates of this technology conducted for the
proposal of the NESHAP in 2001 showed that the average cost per ton of
HCl emissions reduced was approximately $18,000. As nothing has
substantially changed with this technology or in how it would be
implemented, the EPA assumes that the cost effectiveness today would be
similar to that previously estimated, once the costs of inflation are
considered. Inflated to 2020 dollars, the average incremental cost per
ton of HCl emissions reduced is estimated to be approximately $26,000.
We do not find this to be cost effective for the control of HCl and,
therefore, propose that floor-level MACT controls are appropriate for
existing flame laminators.

B. What are the results of the risk assessment and analyses for the
Flexible Polyurethane Foam Fabrication Operations source category?

    As described in section III.C of this preamble, for the Flexible
Polyurethane Foam Fabrication Operations major source category, we
conducted a risk assessment for all HAP emitted. We present results of
the risk assessment briefly below and in more detail in the Flexible
Polyurethane Foam Fabrication Risk Assessment Report, in the docket for
this action (Docket ID No. EPA-HQ-OAR-2020-0572).

1. Chronic Inhalation Risk Assessment Results
    Table 1 below provides a summary of the results of the inhalation
risk assessment for the source category. As discussed in section III.C
of this preamble, we set MACT-allowable HAP emission levels equal to
actual emissions. For more detail about the MACT-allowable emission
levels, see Appendix 1 to the Flexible Polyurethane Foam Fabrication
Risk Assessment Report, in the docket for this action.

                           Table 1--Flexible Polyurethane Foam Fabrication Source Category Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                  Maximum individual      Estimated population at   Estimated annual cancer       Maximum chronic      Maximum screening
                                  cancer risk  (in 1     increased risk of cancer    incidence  (cases per     noncancer TOSHI \21\     acute noncancer
                                       million)              >= 1-in-1 million               year)          --------------------------       HQ\22\
       Risk assessment        ------------------------------------------------------------------------------                          ------------------
                                 Based on     Based on     Based on     Based on     Based on     Based on     Based on     Based on
                                  actual     allowable      actual     allowable      actual     allowable      actual     allowable    Based on actual
                                emissions    Emissions    emissions    emissions    emissions    emissions    emissions    emissions       emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source category..............            0            0            0            0            0            0        0.002        0.002         HQREL = <1
Whole Facility...............          0.1  ...........            0  ...........      0.00001  ...........          0.2  ...........  .................
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The results of  the inhalation risk modeling using actual emissions
data, as shown in Table 1 of this preamble, indicate that no
carcinogens are emitted by this category. Therefore, the cancer MIR
based on actual emissions (lifetime) is zero and the total estimated
annual cancer incidence (national) from these facilities based on
actual emission levels is zero excess cancer cases per year. The
maximum chronic noncancer TOSHI value based on actual emissions is
0.002 driven by HCl.
---------------------------------------------------------------------------

    \21\ The TOSHI is the sum of the chronic noncancer HQ for
substances that affect the same target organ or organ system.
    \22\ The maximum estimated acute exposure concentration was
divided by available short-term threshold values to develop HQ
values.
---------------------------------------------------------------------------

2. Screening Level Acute Risk Assessment Results
    Table 1 of this preamble shows the acute risk results for the
Flexible Polyurethane Foam Fabrication source category. The screening
analysis for acute impacts was based on an emissions multiplier of 10
for all emissions sources, to estimate the peak emission rates from the
average rates. The maximum screening acute noncancer HQ value (off-
facility site) is 0.003 driven by HCl. For more detailed acute risk
screening results, refer to the Flexible Polyurethane Foam Fabrication
Risk Assessment Report, in the docket for this action.
3. Multipathway Risk Screening Results
    No PB-HAP are emitted from the Flexible Polyurethane Foam
Fabrication source category, therefore, a multipathway assessment was
not conducted.
4. Environmental Risk Screening Results
    As described in section III.A of this document, we conducted an
environmental risk screening assessment for the Flexible Polyurethane
Foam Fabrication source category for HCl.
    For HCl, the average modeled concentration around each facility
(i.e., the average concentration of all off-site data points in the
modeling domain) did not exceed any ecological benchmark. In addition,
each individual modeled concentration of HCl and HF (i.e., each off-
site data point in the modeling domain) was below the ecological
benchmarks for all facilities. Based on the results of the
environmental risk screening analysis, we do not expect an adverse
environmental effect as a result of HAP emissions from this source
category.
5. Facility-Wide Risk Results
    As shown in Table 1, the maximum facility-wide cancer MIR is 0.1-
in-1 million, driven by 2,4/2,6-toluene diisocyanate mixture (TDI)
emissions from a vertical non-category point source and a non-category
fugitive point source. The total estimated cancer incidence from the
whole facility is 0.00001 excess cancer cases per year, or one excess
case in every 100,000 years. No people were estimated to have cancer
risks above 1-in-1 million from exposure to HAP emitted from both MACT
and non-MACT sources at the three facilities in this source category.
The maximum facility-wide TOSHI for the source category is estimated to
be 0.2, mainly driven by 2,4/2,6-TDI emissions from a vertical non-
category point source and a non-category fugitive point source.
6. What demographic groups might benefit from this regulation?
    To examine the potential for any environmental justice issues that
might be associated with the Flexible Polyurethane Foam Fabrication
Operations major source category, we performed a demographic analysis,
which is an assessment of risks to individual demographic groups of the
populations living within 5 km and within 50 km of the facilities. In
the analysis, we evaluated the distribution of HAP-related cancer and
noncancer risks from the Flexible Polyurethane Foam Fabrication
Operations major source category across different demographic groups
within the populations living near facilities.\23\
---------------------------------------------------------------------------

    \23\ Demographic groups included in the analysis are: White,
African American, Native American, other races and multiracial,
Hispanic or Latino, children 17 years of age and under, adults 18 to
64 years of age, adults 65 years of age and over, adults without a
high school diploma, people living below the poverty level, people
living two times the poverty level, and linguistically isolated
people.
---------------------------------------------------------------------------

    Results of the demographic analysis for the source category
indicate that the minority population is slightly higher within 5 km of
the three facilities than the national percentage (40 percent versus 38
percent). This difference is accounted for by the larger African
American population around the facilities (17 percent versus 12 percent
nationally). In addition, the percentage of the population living
within 5 km of facilities in the source category is greater than the
corresponding national percentage for the demographic groups, ``Ages 0
to 17'' and ``Below the Poverty Level.'' When examining the risk levels
of those exposed to emissions from Flexible Polyurethane Foam
Fabrication facilities, we find that no one is exposed to a cancer risk
at or above 1-in-1 million or to a chronic noncancer TOSHI greater than
1. The methodology and the results of the demographic analysis are
presented in a technical report, Risk and Technology Review--Analysis
of Demographic Factors for Populations Living Near Flexible
Polyurethane Foam Fabrication Operations Source Category, September
2020 (hereafter referred to as the Flexible Polyurethane Foam
Fabrication Demographic Analysis Report), available in the docket for
this action.

C. What are our proposed decisions regarding risk acceptability, ample
margin of safety, and adverse environmental effect?

1. Risk Acceptability
    As noted in section III.A of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
cancer MIR, the number of persons in various cancer and noncancer risk
ranges, cancer incidence, the maximum noncancer TOSHI, the maximum
acute noncancer HQ, the extent of noncancer risks, the distribution of
cancer and noncancer risks in the exposed population, and risk
estimation uncertainties (54 FR 38044, September 14, 1989).
    For the Flexible Polyurethane Foam Fabrication Operations major
source category, the risk analysis indicates that there is no cancer
risk due to actual emissions or allowable emissions. Since there is no
cancer risk, the risks are considerably less than 100-in-1 million,
which is the presumptive upper limit of acceptable risk. The risk
analysis also shows we did not identify a potential for adverse chronic
noncancer health effects. The acute noncancer risks based on actual
emissions are low at an HQ of less than 1 (based on the REL) for HCl.
Therefore, we find there is little potential concern of acute noncancer
health impacts from actual emissions. In addition, the risk assessment
indicates no significant potential for multipathway health effects.
    Considering all of the health risk information and factors
discussed above, including the uncertainties discussed in section
III.C.7 of this preamble, we propose to find that the risks from the
Flexible Polyurethane Foam Fabrication source category are acceptable.
2. Ample Margin of Safety Analysis
    We are proposing that the risks from the Flexible Polyurethane Foam
Fabrication Operations major source category are acceptable. No
carcinogens are emitted by the Flexible Polyurethane Foam Fabrication
source category. Therefore, there are no individuals in the exposed
population with lifetime cancer risks above 1-in-1 million as a result
of actual or allowable emissions from this category. In addition, the
maximum chronic noncancer TOSHI value based on actual and allowable
emissions is well below 1 (0.002 and 0.2, respectively) and the maximum
screening acute noncancer HQ value (off-facility site) is also well
below 1 (0.003). Therefore, we are proposing that additional emissions
controls for flexible polyurethane foam fabrication facilities are not
necessary to provide an ample margin of safety to protect public
health.
3. Environmental Effect
    The emissions data for the Flexible Polyurethane Foam Fabrication
Operations major source category indicate that one environmental HAP is
emitted by sources within this source category: HCl. The screening-
level evaluation of the potential for adverse environmental effects
associated with emissions of HCl from the Flexible Polyurethane Foam
Fabrication source category indicated that each individual
concentration (i.e., each off-site data point in the modeling domain)
was below the ecological benchmarks for all facilities. In addition, we
are unaware of any adverse environmental effects caused by HAP emitted
by this source category. Therefore, we do not expect there to be an
adverse environmental effect as a result of HAP emissions from this
source category, and we are proposing that it is not necessary to set a
more stringent standard to prevent, taking into consideration costs,
energy, safety, and other relevant factors, an adverse environmental
effect.

D. What are the results and proposed decisions based on our technology
review for the Flexible Polyurethane Foam Fabrication Operations major
source category and for the Flexible Polyurethane Foam Production and
Fabrication area source categories?

    As described in section III.B of this preamble, our technology
review focused on the identification and evaluation of potential
developments in practices, processes, and control technologies that
have occurred since the major source and area source NESHAP for
Flexible Polyurethane Foam Fabrication were promulgated in 2003 and
2007, respectively. During the technology review we identified existing
flame laminators as an unregulated process in the major source
category. This proposal included the establishment of MACT standards
for that process is described in section IV.A of this preamble. In
conducting the technology review, we reviewed various information
sources regarding the emissions from flexible polyurethane foam
fabrication operations facilities and flexible polyurethane foam
production facilities. We conducted separate but similar reviews for
the Flexible Polyurethane Foam major source category and the two area
source categories. The reviews included a search of the RBLC database,
reviews of air permits for flexible polyurethane foam fabrication
operations facilities and flexible polyurethane foam production
facilities, and a review of emissions standards for similar source
categories. We reviewed these data sources for information on
practices, processes, and control technologies that were not considered
during the development of the Flexible Polyurethane Foam Fabrication
Operations NESHAP and the Flexible Polyurethane Foam Production and
Fabrication area source NESHAP. We also looked for information on
improvements in practices, processes, and control technologies that
have been employed since development of the NESHAP. Through searches of
the data sources described in section IV.D of this preamble, one
development in a practice, process, or control technology was
identified for loop slitter use in the Flexible Polyurethane Foam
Fabrication Operations major source category.
    A loop slitter is a large machine used to create thin sheets of
foam from the large blocks of foam or ``buns'' created at a foam
production plant. A slitter consists of a large, vertical, oval
conveyor belt and a cutting mechanism, which cuts a thin sheet of foam
to the desired thickness. When the buns are mounted on the conveyor of
the slitter, they are glued end-to-end, forming a loop. Loop slitter
emissions of HAP can occur from the application of the adhesives used
to glue the foam buns together if the adhesive used contains HAP. The
application of the adhesive is performed at the beginning of the loop
slitting process, which can run for several hours before the bun is
fully cut and the machine is loaded with new buns of foam.
    At the time of the development of the NESHAP, the EPA found that
the foam fabrication industry had effectively discontinued the use of
adhesives containing methylene chloride, which was the primary HAP in
the adhesives used, and had switched to other adhesives that did not
contain methylene chloride or other HAP. As a result, for both existing
and new loop slitters, the MACT standard for loop slitters proposed in
2001 was the prohibition of HAP-based adhesives. The definition in the
2001 proposed standards for a HAP-based adhesive was an adhesive
containing detectable HAP. In comments on the proposed standards,
industry representatives indicated that the adhesives used contained
small amounts of HAP rather than the estimated zero HAP content. In
response to these comments, the definition of HAP-based adhesive was
revised in the promulgated rule to be an adhesive

containing 5 percent (by weight) or greater of HAP.