[Federal Register Volume 84, Number 96 (Friday, May 17, 2019)]
[Proposed Rules]
[Pages 22642-22685]
[FR Doc No: 2019-09583]

Vol. 84

Friday,

No. 96

May 17, 2019

Part III

 Envionmental Protection Agency

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40 CFR Part 63

 National Emission Standards for Hazardous Air Pollutants: Boat
Manufacturing and Reinforced Plastic Composites Production Residual
Risk and Technology Review; Proposed Rule

Federal Register / Vol. 84, No. 96 / Friday, May 17, 2019 / Proposed
Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2016-0447 and EPA-HQ-OAR-2016-0449; FRL-9992-76-OAR]
RIN 2060-AT12

National Emission Standards for Hazardous Air Pollutants: Boat
Manufacturing and Reinforced Plastic Composites Production Residual
Risk and Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing
amendments to the National Emission Standards for Hazardous Air
Pollutants (NESHAP) for Boat Manufacturing and the NESHAP for
Reinforced Plastic Composites Production. The proposed amendments
address the results of the residual risk and technology review (RTR)
conducted as required under the Clean Air Act (CAA) for these source
categories. The EPA is proposing to find the risks due to emissions of
air toxics from these source categories under the current standards to
be acceptable and that the standards provide an ample margin of safety
to protect public health. We are proposing no revisions to the
numerical emission limits or other aspects of the rules based on these
risk analyses or technology reviews. Additionally, the EPA is proposing
to amend provisions addressing emissions during periods of startup,
shutdown, and malfunction (SSM) and to amend provisions regarding
electronic reporting of certain notifications, performance test
results, and semiannual reports.

DATES:
    Comments. Comments must be received on or before July 1, 2019.
Under the Paperwork Reduction Act (PRA), comments on the information
collection provisions are best assured of consideration if the Office
of Management and Budget (OMB) receives a copy of your comments on or
before June 17, 2019.
    Public Hearing. If anyone contacts us requesting a public hearing
on or before May 22, 2019, we will hold a hearing. Additional
information about the hearing, if requested, will be published in a
subsequent Federal Register document and posted at https://www.epa.gov/stationary-sources-air-pollution/boat-manufacturing-national-emission-standards-hazardous-air for the Boat Manufacturing NESHAP, and https://www.epa.gov/stationary-sources-air-pollution/reinforced-plastic-composites-production-national-emission for the Reinforced Plastic
Composites Production NESHAP. See SUPPLEMENTARY INFORMATION for
information on requesting and registering for a public hearing.

ADDRESSES:
    Comments. Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2016-0447 for the Boat Manufacturing NESHAP and Docket ID No. EPA-
HQ-OAR-2016-0449 for the Reinforced Plastic Composites Production
NESHAP, at https://www.regulations.gov. Follow the online instructions
for submitting comments. Once submitted, comments cannot be edited or
removed from Regulations.gov. See SUPPLEMENTARY INFORMATION for detail
about how the EPA treats submitted comments. Regulations.gov is our
preferred method of receiving comments. However, the following other
submission methods are also accepted:
     Email<EMAIL_ADDRESS>Include Docket ID No. EPA-
HQ-OAR-2016-0447 for the Boat Manufacturing NESHAP or Docket ID No.
EPA-HQ-OAR-2016-0449 for the Reinforced Plastic Composites Production
NESHAP in the subject line of the message.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2016-0447 for the Boat Manufacturing NESHAP or Docket ID No. EPA-HQ-
OAR-2016-0449 for the Reinforced Plastic Composites Production NESHAP.
     Mail: To ship or send mail via the United States Postal
Service, use the following address: U.S. Environmental Protection
Agency, EPA Docket Center, Docket ID No. EPA-HQ-OAR-2016-0447 for the
Boat Manufacturing NESHAP or Docket ID No. EPA-HQ-OAR-2016-0449 for the
Reinforced Plastic Composites Production NESHAP, Mail Code 28221T, 1200
Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: Use the following Docket Center
address if you are using express mail, commercial delivery, hand
delivery, or courier: EPA Docket Center, EPA WJC West Building, Room
3334, 1301 Constitution Avenue NW, Washington, DC 20004. Delivery
verification signatures will be available only during regular business
hours.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Mr. Brian Storey, 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. James Hirtz,
Health and Environmental Impacts Division (C539-02), Office of Air
Quality Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711; telephone number: (919)
541-0881; fax number:<PHONE_NUMBER>; and email address:
<EMAIL_ADDRESS>For information about the applicability of the
Boat Manufacturing NESHAP or Reinforced Plastic Composites Production
NESHAP to a particular entity, contact Mr. John Cox, Office of
Enforcement and Compliance Assurance, U.S. Environmental Protection
Agency, EPA WJC South Building (Mail Code 2221A), 1200 Pennsylvania
Avenue NW, Washington DC 20460; telephone number:<PHONE_NUMBER>; and
email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    Public hearing. Please contact Ms. Nancy Perry at<PHONE_NUMBER> or
by email at<EMAIL_ADDRESS>to request a public hearing, to
register to speak at the public hearing, or to inquire as to whether a
public hearing will be held.
    Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2016-0447 for the Boat Manufacturing NESHAP or
Docket ID No. EPA-HQ-OAR-2016-0449 for the Reinforced Plastic
Composites Production NESHAP. All documents in the docket are listed in
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. Publicly available
docket materials are available either electronically in Regulations.gov
or in hard copy at the EPA Docket Center, Room 3334, EPA WJC West
Building, 1301 Constitution Avenue NW, Washington, DC. The Public
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Public
Reading Room is<PHONE_NUMBER>, and the telephone number for the EPA
Docket Center is<PHONE_NUMBER>.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2016-0447 for the Boat Manufacturing NESHAP or Docket ID No. EPA-HQ-

OAR-2016-0449 for the Reinforced Plastic Composites Production NESHAP.
The EPA's policy is that all comments received will be included in the
public docket without change and may be made available online at
https://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be CBI or
other information whose disclosure is restricted by statute. Do not
submit information that you consider to be CBI or otherwise protected
through https://www.regulations.gov or email. This type of information
should be submitted by mail as discussed below.
    The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the Web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit https://www2.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov website allows you to submit your
comment anonymously, which means the EPA will not know your identity or
contact information unless you provide it in the body of your comment.
If you send an email comment directly to the EPA without going through
https://www.regulations.gov, your email address will be automatically
captured and included as part of the comment that is placed in the
public docket and made available on the internet. If you submit an
electronic comment, the EPA recommends that you include your name and
other contact information in the body of your comment and with any
digital storage media you submit. If the EPA cannot read your comment
due to technical difficulties and cannot contact you for clarification,
the EPA may not be able to consider your comment. Electronic files
should not include special characters or any form of encryption and be
free of any defects or viruses. For additional information about the
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    Submitting CBI. Do not submit information containing CBI to the EPA
through https://www.regulations.gov or email. Clearly mark the part or
all of the information that you claim to be CBI. For CBI information on
any digital storage media that you mail to the EPA, mark the outside of
the digital storage media as CBI and then identify electronically
within the digital storage media the specific information that is
claimed as CBI. In addition to one complete version of the comments
that includes information claimed as CBI, you must submit a copy of the
comments that does not contain the information claimed as CBI directly
to the public docket through the procedures outlined in Instructions
above. If you submit any digital storage media that does not contain
CBI, mark the outside of the digital storage media clearly that it does
not contain CBI. Information not marked as CBI will be included in the
public docket and the EPA's electronic public docket without prior
notice. Information marked as CBI will not be disclosed except in
accordance with procedures set forth in 40 Code of Federal Regulations
(CFR) part 2. Send or deliver information identified as CBI only to the
following address: OAQPS Document Control Officer (C404-02), OAQPS,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2016-0447 for the
Boat Manufacturing NESHAP or Docket ID No. EPA-HQ-OAR-2016-0449 for the
Reinforced Plastic Composites Production NESHAP.
    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
BMC bulk molding compound
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CEDRI compliance and emissions data reporting interface
CFR Code of Federal Regulations
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guideline
ERT electronic reporting tool
GACT generally available control technologies
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-3 Human Exposure Model, Version 1.1.0
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
ICR information collection request
IRIS Integrated Risk Information System km kilometer
MACT maximum achievable control technology
MDI 4,4'-diphenylmethane diisocyanate
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
MMA methyl methacrylate
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NEI national emissions inventory
NESHAP national emission standards for hazardous air pollutants
NSR new source review
NTTAA National Technology Transfer and Advancement Act
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
POM polycyclic organic matter
ppm parts per million
PRA Paperwork Reduction Act
RBLC Reasonably Available Control Technology, Best Available Control
Technology, and Lowest Achievable Emission Rate (RACT/BACT/LAER)
Clearinghouse
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RTR residual risk and technology review
SAB Science Advisory Board
SMC sheet molding compound
SSM startup, shutdown, and malfunction
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology. Fate, Transport, and
Ecological Exposure model
UF uncertainty factor
[micro]g/m\3\ microgram per cubic meter
UMRA Unfunded Mandates Reform Act
URE unit risk estimate

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

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
II. Background
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP
regulate its HAP emissions?
    C. What data collection activities were conducted to support
this action?
    D. What other relevant background information and data are
available?
III. Analytical Procedures and Decision Making
    A. How do we consider risk in our decision-making?
    B. How do we perform the technology review?
    C. How do we estimate post-MACT risk posed by the source
category?
IV. Analytical Results and Proposed Decisions

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

I. General Information

A. Does this action apply to me?

    Table 1 of this preamble lists the NESHAP and associated regulated
industrial source categories that are the subject of this proposal.
Table 1 is not intended to be exhaustive, but rather provides a guide
for readers regarding the entities that this proposed action is likely
to affect. The proposed standards, once promulgated, will be directly
applicable to the affected sources. Federal, state, local, and tribal
government entities would not be affected by this proposed action.

    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
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 NESHAP and source category      NAICS code \1\      Regulated entities
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Boat Manufacturing..........  336612..............  Boat manufacturing
                                                     facilities that
                                                     perform fiberglass
                                                     production
                                                     operations or
                                                     aluminum coating
                                                     operations.
Reinforced Plastic            326113, 326121,       Reinforced plastic
 Composites Production.        326122, 326130,       composites
                               326140, 326191,       production
                               327110, 327991,       facilities that
                               332321, 332420,       manufacture
                               333132, 333415,       intermediate, and/
                               333611, 333924,       or final products
                               334310, 335311,       using styrene
                               335313, 335932,       containing
                               336111, 336211,       thermoset resins
                               336213, 336214,       and gel coats.
                               336320, 336413,
                               336510, 337110,
                               337125, 337127,
                               337215, 339920,
                               339991.
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\1\ North American Industry Classification System.

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

    In addition to being available in the docket, an electronic copy of
this action is available on the internet. Following signature by the
EPA Administrator, the EPA will post a copy of this proposed action at
https://www.epa.gov/stationary-sources-air-pollution/boat-manufacturing-national-emission-standards-hazardous-air for the Boat
Manufacturing NESHAP, and https://www.epa.gov/stationary-sources-air-pollution/reinforced-plastic-composites-production-national-emission
for the Reinforced Plastic Composites Production NESHAP. Following
publication in the Federal Register, the EPA will post the Federal
Register version of the proposal and key technical documents at this
same website. Information on the overall RTR program is available at
https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.
    A redline version of the regulatory language that incorporates the
proposed changes in this action is available in the docket for this
action (Docket ID No. EPA-HQ-OAR-2016-0447 for the Boat Manufacturing
NESHAP or Docket ID No. EPA-HQ-OAR-2016-0449 for the Reinforced Plastic
Composites Production NESHAP).

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 hazardous air pollutants (HAP) from stationary
sources. Generally, the first stage involves establishing technology-
based standards and the second stage involves evaluating those
standards that are based on maximum achievable control technology
(MACT) to determine whether additional standards are needed to address
any remaining risk associated with HAP emissions. This second stage is
commonly referred to as the ``residual risk review.'' In addition to
the residual risk review, the CAA also requires the EPA to review
standards set under CAA section 112 every 8 years to determine if there
are ``developments in practices, processes, or control technologies''
that may be appropriate to incorporate into the standards. This review
is commonly referred to as the ``technology review.'' When the two
reviews are combined into a single rulemaking, it is commonly referred
to as the ``risk and technology review.''

The discussion that follows identifies the most relevant statutory
sections and briefly explains the contours of the methodology used to
implement these statutory requirements. A more comprehensive discussion
appears in the document titled CAA Section 112 Risk and Technology
Reviews: Statutory Authority and Methodology in the docket for this
rulemaking.
    In the first stage of the CAA section 112 standard setting process,
the EPA promulgates technology-based standards under CAA section 112(d)
for categories of sources identified as emitting one or more of the HAP
listed in CAA section 112(b). Sources of HAP emissions are either major
sources or area sources, and CAA section 112 establishes different
requirements for major source standards and area source standards.
``Major sources'' are those that emit or have the potential to emit 10
tons per year (tpy) or more of a single HAP or 25 tpy or more of any
combination of HAP. All other sources are ``area sources.'' For major
sources, CAA section 112(d)(2) provides that the technology-based
NESHAP must reflect the maximum degree of emission reductions of HAP
achievable (after considering cost, energy requirements, and non-air
quality health and environmental impacts). These standards are commonly
referred to as MACT standards. CAA section 112(d)(3) also establishes a
minimum control level for MACT standards, known as the MACT ``floor.''
The EPA must also consider control options that are more stringent than
the floor. Standards more stringent than the floor are commonly
referred to as beyond-the-floor standards. In certain instances, as
provided in CAA section 112(h), the EPA may set work practice standards
where it is not feasible to prescribe or enforce a numerical emission
standard. For area sources, CAA section 112(d)(5) gives the EPA
discretion to set standards based on generally available control
technologies or management practices (GACT standards) in lieu of MACT
standards.
    The second stage in standard-setting focuses on identifying and
addressing any remaining (i.e., ``residual'') risk according to CAA
section 112(f). For source categories subject to MACT standards,
section 112(f)(2) of the CAA requires the EPA to determine whether
promulgation of additional standards is needed to provide an ample
margin of safety to protect public health or to prevent an adverse
environmental effect. Section 112(d)(5) of the CAA provides that this
residual risk review is not required for categories of area sources
subject to GACT standards. Section 112(f)(2)(B) of the CAA further
expressly preserves the EPA's use of the two-step approach for
developing standards to address any residual risk and the Agency's
interpretation of ``ample margin of safety'' developed in the National
Emissions Standards for Hazardous Air Pollutants: Benzene Emissions
from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene
Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery
Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA
notified Congress in the Risk Report that the Agency intended to use
the Benzene NESHAP approach in making CAA section 112(f) residual risk
determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently
adopted this approach in its residual risk determinations and the
United States Court of Appeals for the District of Columbia Circuit
(the Court) upheld the EPA's interpretation that CAA section 112(f)(2)
incorporates the approach established in the Benzene NESHAP. See NRDC
v. EPA, 529 F.3d 1077, 1083 (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 38045, September 14,
1989. If risks are unacceptable, the EPA must determine the emissions
standards necessary to reduce risk to an acceptable level without
considering costs. In the second step of the approach, the EPA
considers whether the emissions standards provide an ample margin of
safety to protect public health ``in consideration of all health
information, including the number of persons at risk levels higher than
approximately 1 in 1 million, as well as other relevant factors,
including costs and economic impacts, technological feasibility, and
other factors relevant to each particular decision.'' Id. The EPA must
promulgate emission standards necessary to provide an ample margin of
safety to protect public health. 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).

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

1. What is the Boat Manufacturing source category and how does the
current NESHAP regulate its HAP emissions?
    The Boat Manufacturing NESHAP was promulgated on August 22, 2001
(66 FR 44218), and codified at 40 CFR part 63, subpart VVVV. As
promulgated, the Boat Manufacturing NESHAP applies to fiberglass and
aluminum boat manufacturing operations located at facilities considered
to be major sources of HAP emissions. The HAP emissions from these boat
manufacturing operations and processes are fugitive emissions. Fugitive
emissions result from HAP evaporating from the resins, gel coats,
solvents, adhesives, and surface coatings used in manufacturing
processes. The following is a brief description of these processes and
operations found at boat manufacturing facilities: Fiberglass boat
manufacturing operations; fabric and carpet adhesive operations; and
aluminum boat surface coating operations.
    Fiberglass boat manufacturing operations. Fiberglass boat
manufacturing involves using glass fiber reinforcements laid in a mold
and saturating the fiberglass with resin. The resin hardens to form a
rigid plastic part reinforced with fiberglass. Manufacturing processes
are generally considered either ``open molding'' or ``closed molding.''
    In open molding, the outer parts of the boat are built by first
spraying a mold with a layer of gel coat, which is a pigmented
polyester resin that hardens and becomes the smooth outside surface of
the part. The inside of the hardened gel coat layer is coated

with chopped glass fibers and polyester or vinylester resin. Additional
layers of fiberglass cloth or chopped glass fibers saturated with resin
are added until the part is the final thickness. The same basic process
is used to build or repair molds with tooling gel coat and tooling
resin.
    Closed molding processes include resin infusion molding and resin
transfer molding. These processes are typically used to produce smaller
boat parts and involve packing a mold cavity with fiberglass
reinforcement and infusing the fiber with resin either under pressure,
where the resin is ``pushed'' into the mold cavity, or under vacuum,
where the air of the mold cavity is removed and replaced by resin. In
either process, the mold is sealed, to effectively transfer the resin
into the mold cavity and to control the saturation of the fiber
reinforcement.
    The resins that are used in fiberglass boat manufacturing contain
styrene as a solvent and a cross-linking agent. Gel coats contain
styrene and methyl methacrylate (MMA) which provides resistance to
degradation of the gel coat by ultraviolet light. Styrene and MMA are
HAP, and, in an open mold process, a fraction evaporates during resin
and gel coat application and curing. Resins and gel coats containing
styrene and MMA are also used to make the molds used in the
manufacturing process. Mixing is done to resins or gel coats to mix the
resins and gel coats with promoters, fillers, or other additives before
being applied to the mold. Some HAP from the resins and gel coats are
emitted during the mixing process. Resin and gel coat application
equipment requires solvent cleaning to remove uncured resin or gel coat
when not in use. The resin or gel coat can catalyze in the hoses or gun
if not flushed with a solvent after each use.
    For some types of boats, the void spaces between the walls of the
boat are filled with a foam to provide additional buoyancy to the boat,
once constructed. The foam is formed by pouring a two-part foam product
into the void space. The two-part product consists of resin, where the
HAP is predominantly styrene and 4,4'-diphenylmethane diisocyanate
(MDI), another HAP in the process. The MDI component of the foam is a
reactant that reacts with the resin, when combined, to form the
hardened polyurethane foam.
    Fabric and carpet adhesive operations. The interiors of many types
of fiberglass boats and aluminum boats are covered with carpeting or
fabric to improve the appearance, provide traction, or deaden sound.
The material is bonded to the interior with contact adhesives. The
adhesives can include HAP such as methylene chloride, toluene, xylenes,
and methyl chloroform.
    Aluminum boat surface coatings. Aluminum boat hull topsides and
decks are painted with coatings applied with spray guns. These coatings
may be high-gloss polyurethane coatings or low-gloss single-part
coatings. These surface coatings often contain HAP solvents, such as
toluene, xylenes, and isocyanates. The HAP-containing solvents are also
used to clean surfaces before finishing (wipe-down solvents) and for
cleaning paint and coating spray guns.
    The Boat Manufacturing NESHAP regulates organic HAP from sources
that manufacture non-commercial and non-military aluminum boats or all
types of fiberglass boats. Coating operations on vessels used for
commercial and military purposes are covered by the Shipbuilding and
Repair NESHAP (40 CFR part 63, subpart II). The Boat Manufacturing
NESHAP applies to the following operations: All open molding
operations, including pigmented gel coat, clear gel coat, production
resin, tooling resin, and tooling gel coat, and all closed molding
resin operations. The NESHAP regulates HAP emissions by setting a HAP
content limit for the resins and gel coats used at each regulated open
molding resin and gel coat operation. For each regulated open molding
resin operation, the NESHAP establishes separate HAP content limits for
atomized and non-atomized resin application methods. For closed molding
operations, no limits apply to the resin application operation if it
meets the specific definition of closed molding provided in the NESHAP.
If a molding operation does not meet the definition of closed molding
that is provided in the NESHAP, then it must comply with the applicable
emission limits for open molding. Other operations are subject to
either work practice requirements or HAP content limits, including the
following:
     All resin and gel coat application equipment cleaning;
     All resin and gel coat mixing operations; and
     All carpet and fabric adhesive operations.
    Resin and gel coat mixing containers with a capacity of 208 liters
(55 gallons) or more must be covered with tightly fitted lids. Routine
resin and gel coat equipment cleaning operations must use solvents
containing no more than 5-percent organic HAP, but solvents used to
remove cured resin or gel coat from equipment are exempt from the HAP
content limits. However, the containers used to hold the exempt solvent
and to clean equipment being used with cured resin and gel coat must be
covered, and there is an annual limit on the amount of exempt solvent
that can be used. Lastly, the NESHAP includes HAP limits for carpet and
fabric adhesives operations, limiting use to those adhesives that
contain no more than 5-percent organic HAP by weight.
    The Boat Manufacturing NESHAP applies to aluminum recreational boat
manufacturing facilities performing the following operations:
     All aluminum recreational boat surface coating and
associated spray gun cleaning and wipe-down solvent operations; and
     All carpet and fabric adhesive operations.
    The NESHAP includes the following requirements for aluminum
recreational boat manufacturing:
     Aluminum wipe-down solvents are limited to no more than
0.33 kilograms of organic HAP per liter of total coating solids applied
(2.75 pounds per gallon) from aluminum primers, clear coats, and top
coats combined (no limit applies when cleaning surfaces are receiving
decals or adhesive graphics).
     Aluminum recreational boat surface coatings (including
thinners, activators, primers, topcoats, and clear coats) are limited
to no more than 1.22 kilograms of organic HAP per liter of total
coating solids applied (10.18 pounds per gallon) from aluminum primers,
clear coats, and top coats combined.
     Combined aluminum surface coatings and aluminum wipe-down
solvents are limited to no more than 1.55 kilograms of organic HAP per
liter of total coating solids applied (12.9 pounds per gallon) from
aluminum primers, clear coats, and top coats combined.
    In addition, aluminum recreational boat manufacturing facilities
must meet work practice standards to ensure that spray guns are cleaned
and the cleaning solvent is stored in an enclosed device, and that the
enclosure remains closed when not in use.
    The applicability of Boat Manufacturing NESHAP requirements is
described in greater detail in the 2001 rule (66 FR 44218) and 40 CFR
part 63, subpart VVVV.
2. What is the Reinforced Plastic Composites Production source category
and how does the current NESHAP regulate its HAP emissions?
    The Reinforced Plastic Composites Production NESHAP was originally
promulgated on April 21, 2003 (68 FR 19375) and was amended on August
25, 2005 (70 FR 50118). The requirements

are codified at 40 CFR part 63, subpart WWWW. The Reinforced Plastic
Composites Production source category includes the manufacturing of
reinforced and non-reinforced plastic composite products and the
production of plastic molding compounds used in the production of
plastic composite products. As with boat manufacturing, reinforced
plastic composite products are manufactured using resins containing
styrene. Some processes use gel coats containing styrene and MMA.
Operations also include mixing, tooling, and equipment cleaning. Many
of the reinforced plastic composites products are manufactured using an
open molding process similar to the boat manufacturing industry. As
with boat manufacturing, the air emissions resulting from an open mold
manufacturing process are fugitive in nature. Additionally, however,
the reinforced plastic composites production processes can include
pultrusion, sheet molding compound (SMC) and bulk molding compound
(BMC) manufacturing, filament winding, casting, and other processes.
The following paragraphs provide a brief description of some of the
various processes utilized in the Reinforced Plastic Composites
Production source category.
    Open Mold Process. The use of open molds is similar to the boat
manufacturing operations, where the mold is sprayed with a layer of gel
coat, or chopped glass fibers and polyester or vinylester resin.
Additional layers of fiberglass and resin are added until the
manufactured part is the final thickness. In addition, woven roving or
mats can also be used instead of chopped fiber, in which case a spray
gun would apply resin to saturate the fiberglass mat. Once the material
has been applied to the mold, brushes or rollers are used to remove any
entrapped air and to assure that the laminate is thoroughly ``wet.''
    Pultrusion. Pultrusion is a continuous manufacturing process that
produces parts with constant cross-sectional shapes. In a pultrusion
operation, the composite is pulled through an extrusion-type die by a
gripper/puller system. Reinforcing fibers are pulled through a resin
bath where all materials are thoroughly impregnated with liquid resin.
The wet fibrous laminate is formed to the desired geometric shape in a
pre-forming section and pulled into the heated steel die. As an
alternative to using a resin bath, resin can be injected into the pre-
forming section (resin injection) or directly into the forming die (die
injection). In the die, the resin cure is initiated by elevated
temperatures. The laminate solidifies in the exact shape of the die
cavity as it is being continuously pulled by the pultrusion machine.
The cured product can then be cut to desired lengths.
    Compression Molding. Compression molding operations involve
compressing the composite material under hydraulic pressure in matched
metal dies and holding the configured, condensed material in the
desired shape until the resin system has cured. The composite materials
used in the compression molding process include SMC and BMC. SMC
manufacturing includes an integrated composite material which contains
all reinforcement, resin, fillers, chemical thickeners, catalyst, mold
release agents, and other ingredients in an easily handled sheet. BMC
manufacturing includes preparing a putty-like molding compound, which
contains resins, catalysts, fillers, and reinforcements in a ``ready-
to-mold'' form. The production output in compression molding is
relatively high because the molding compounds cure rapidly in the
heated mold. The materials generally yield a good finish without
application of gel coat. Both surfaces of the molded product will be as
smooth as the mold surface.
    Filament Winding. Filament winding is a composite production
process for manufacturing products that are surfaces of revolution. In
this process, fibers are impregnated with resin in a resin bath and
wrapped around a rotating mold surface following a machine controlled
geometric pattern. The product is then cured in an oven or at room
temperature. All types of reinforcing fibers can be utilized in
filament winding, but continuous glass fiber is most commonly used due
to its high specific strength and relative low cost. Different winding
patterns can be applied alone or in combination to achieve the desired
strength and shape characteristics.
    Polymer Casting. In the polymer casting process, polymers, fillers,
and additives are combined by pouring or dispensing these materials
into open or partially open molds and allowing the materials to cure.
Fiberglass reinforcement is generally not used in cast polymer
products. In the polymer casting process, the resin matrix is catalyzed
and cast onto the mold which is usually vibrated to allow air bubbles
to escape. Following vibration, the product enters an exothermic stage
in which the matrix's chemical reaction generates heat that causes the
product to cure. In some cases, an oven is used to accelerate cure.
    Centrifugal Casting. In centrifugal casting, resin and fiber
reinforcements (if needed) are deposited against the inside surface of
a rotating mold. A resin applicator which is often located in the
center of the rotating mold supplies the resin to the inside of the
cast. Centrifugal force holds the material in place while the part is
cured. The outside surface of the part, which is cured against the
inside surface of the mold, represents the finished surface. The
interior surface of the centrifugally cast part can be improved by
adding an additional coat of pure resin.
    The Reinforced Plastic Composites Production NESHAP applies to
owners/operators of reinforced plastic composites production facilities
located at major sources of HAP emissions. Applicable production is
limited to operations in which reinforced and/or nonreinforced plastic
composites or plastic molding compounds are manufactured using
thermoset resins and/or gel coats that contain styrene to produce
plastic composites. Applicable operations also include cleaning,
mixing, HAP-containing materials storage, and repair operations
associated with the production of plastic composites. The Reinforced
Plastic Composites Production NESHAP does not apply to those facilities
who only repair reinforced plastic composites products. These repairs
include the non-routine manufacturing of individual components or parts
intended to repair a larger item. Additionally, the Reinforced Plastic
Composites Production NESHAP does not apply to research and development
facilities, as defined in section 112(c)(7) of the CAA. Lastly, the
Reinforced Plastic Composites Production NESHAP is limited to those
facilities that use greater than 1.2 tpy of thermoset resins and gel
coats (combined) that contain styrene. Facilities are required to
incorporate pollution-prevention techniques in their production
processes. These techniques include the following:
     Using raw materials containing low amounts of air toxics;
     Non-atomized resin application; and
     Covering open resin baths and tanks.

In general, the Reinforced Plastic Composites Production NESHAP
requirements apply to three groups of operations, which include the
following:
     Sources required to reduce HAP emissions by 95 percent;
     Sources required to comply with work practice standards;
and
     Sources required to comply with emission limits.

The applicability of these requirements is described in greater detail
in the 2003 rule (68 FR 19375), and 40 CFR part 63, subpart WWWW.

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

    For the residual risk assessment, the EPA sent out an information
collection request (ICR) to nine parent companies subject to the Boat
Manufacturing NESHAP, requesting information regarding the boat
manufacturing process and the associated air emissions. The information
requested included description of HAP-emitting processes, information
on the HAP-containing materials used, estimates of emissions, and
descriptions of control technologies, if present. After receiving
information, as requested, from the boat manufacturing facilities
surveyed, the EPA compiled the data with the intent to use the
information as a reference to develop the risk assessment modeling
file. The ICR information provided supplemental information regarding
processes, the sources of HAP emissions, material usages, and stack
information. No ICR was sent to sources in the Reinforced Plastic
Composites Production source category.
    For both the Boat Manufacturing NESHAP RTR and the Reinforced
Plastic Composites Production NESHAP RTR, the EPA used data from the
2014 National Emissions Inventory (NEI). 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 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 points at facilities and the related
emissions release parameters. The EPA used NEI emissions and supporting
data as the primary data to develop the model input files for the
residual risk assessments for the Boat Manufacturing and Reinforced
Plastic Composites Production source categories. Additional information
on the development of the modeling file for each source category can be
found in Appendix 1 to the Residual Risk Assessment for the Boat
Manufacturing Source Category in Support of the 2018 Risk and
Technology Review Proposed Rule (Docket ID No. EPA-HQ-OAR-2016-0447)
and Appendix 1 to the Residual Risk Assessment for the reinforced
Plastic Composites Production Source Category in Support of the 2018
Risk and Technology Review Proposed Rule (Docket ID No. EPA-HQ-OAR-
2016-0449).
    For both the risk modeling and technology review portion of these
RTRs, the EPA visited one boat manufacturing facility and six
reinforced plastic composites production facilities. During the visits,
the EPA discussed process operations, compliance with the existing
NESHAP, description of the emission points, process controls,
unregulated emissions, and other aspects of facility operations. We
used the information provided by the facilities to understand the
various operations, and in our evaluation of existing controls and new
developments in practices, processes, and control technologies for both
source categories. The site visit reports are included as attachments
to the memorandum, Technology Review for Boat Manufacturing and
Reinforced Plastic Composites Production Source Category, in the docket
for each source category (Docket ID No. EPA-HQ-OAR-2016-0447 for the
Boat Manufacturing NESHAP and Docket ID No. EPA-HQ-OAR-2016-0449 for
the Reinforced Plastic Composites Production NESHAP).
    For both the risk modeling and technology review, the EPA also
gathered data from facility construction and operating permits
regarding emission points, air pollution control devices, and process
operations. We collected permits and supporting documentation from
state permitting authorities through state-maintained online databases.
The facility permits were also used to confirm that the facilities were
major sources of HAP and were subject to the NESHAP that are the
subject of these risk assessments. In certain cases, we contacted
facility owners or operators to confirm and clarify the sources of
emissions that were reported in the NEI.

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

    For the technology review portion of these RTRs, we collected
information from the Reasonably Available Control Technology, Best
Available Control Technology, and Lowest Achievable Emission Rate
Clearinghouse (RBLC). This 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 Boat Manufacturing and Reinforced Plastic
Composites Production Source Category (Docket ID No. EPA-HQ-OAR-2016-
0447 for the Boat Manufacturing NESHAP and Docket ID No. EPA-HQ-OAR-
2016-0449 for the Reinforced Plastic Composites Production NESHAP).

III. Analytical Procedures and Decision-Making

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

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

    As discussed in section II.A of this preamble and in the Benzene
NESHAP, in evaluating and developing standards under CAA section
112(f)(2), we apply a two-step approach to determine whether or not
risks are acceptable and to determine if the standards provide an ample
margin of safety to protect public health. As explained in the Benzene
NESHAP, ``the first step judgment on acceptability cannot be reduced to
any single factor'' and, thus, ``[t]he Administrator believes that the
acceptability of risk under section 112 is best judged on the basis of
a broad set of health risk measures and information.'' 54 FR 38046,
September 14, 1989. Similarly, with regard to the ample margin of
safety determination, ``the Agency again considers all of the health
risk and other health information considered in the first step. Beyond
that information, additional factors relating to the appropriate level
of control will also be considered, including cost and economic impacts
of controls, technological feasibility, uncertainties, and any other
relevant factors.'' Id.
    The Benzene NESHAP approach provides flexibility regarding factors
the EPA may consider in making determinations and how the EPA may weigh
those factors for each source category. The EPA conducts a risk
assessment that provides estimates of

the MIR posed by the HAP emissions from each source in the source
category, the hazard index (HI) for chronic exposures to HAP with the
potential to cause noncancer health effects, and the hazard quotient
(HQ) for acute exposures to HAP with the potential to cause noncancer
health effects.\2\ The assessment also provides estimates of the
distribution of cancer risk within the exposed populations, cancer
incidence, and an evaluation of the potential for an adverse
environmental effect. The scope of the EPA's risk analysis is
consistent with the EPA's response to comments on our policy under the
Benzene NESHAP where the EPA explained that:
---------------------------------------------------------------------------

    \2\ 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
exposure to the HAP to the level at or below which no adverse
chronic noncancer effects are expected; the HI is the sum of HQs for
HAP that affect the same target organ or organ system.

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

    See 54 FR 38057, September 14, 1989. Thus, the level of the MIR is
only one factor to be weighed in determining acceptability of risk. The
Benzene NESHAP explained that ``an MIR of approximately one in 10
thousand should ordinarily be the upper end of the range of
acceptability. As risks increase above this benchmark, they become
presumptively less acceptable under CAA section 112, and would be
weighed with the other health risk measures and information in making
an overall judgment on acceptability. Or, the Agency may find, in a
particular case, that a risk that includes an MIR less than the
presumptively acceptable level is unacceptable in the light of other
health risk factors.'' Id. at 38045. Similarly, with regard to the
ample margin of safety analysis, the EPA stated in the Benzene NESHAP
that: ``EPA believes the relative weight of the many factors that can
be considered in selecting an ample margin of safety can only be
determined for each specific source category. This occurs mainly
because technological and economic factors (along with the health-
related factors) vary from source category to source category.'' Id. at
38061. We also consider the uncertainties associated with the various
risk analyses, as discussed earlier in this preamble, in our
determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information
to date in making residual risk determinations. At this time, we do not
attempt to quantify the HAP risk that may be associated with emissions
from other facilities that do not include the source categories under
review, mobile source emissions, natural source emissions, persistent
environmental pollution, or atmospheric transformation in the vicinity
of the sources in the categories.
    The EPA understands the potential importance of considering an
individual's total exposure to HAP in addition to considering exposure
to HAP emissions from the source category and facility. We recognize
that such consideration may be particularly important when assessing
noncancer risk, where pollutant-specific exposure health reference
levels (e.g., reference concentrations (RfCs)) are based on the
assumption that thresholds exist for adverse health effects. For
example, the EPA recognizes that, although exposures attributable to
emissions from a source category or facility alone may not indicate the
potential for increased risk of adverse noncancer health effects in a
population, the exposures resulting from emissions from the facility in
combination with emissions from all of the other sources (e.g., other
facilities) to which an individual is exposed may be sufficient to
result in an increased risk of adverse noncancer health effects. In May
2010, the Science Advisory Board (SAB) advised the EPA ``that RTR
assessments will be most useful to decision makers and communities if
results are presented in the broader context of aggregate and
cumulative risks, including background concentrations and contributions
from other sources in the area.'' \3\
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    \3\ Recommendations of the SAB Risk and Technology Review (RTR)
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.
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    In response to the SAB recommendations, the EPA incorporates
cumulative risk analyses into its RTR risk assessments, including those
reflected in this proposal. The Agency (1) conducts facility-wide
assessments, which include source category emission points, as well as
other emission points within the facilities; (2) combines exposures
from multiple sources in the same category that could affect the same
individuals; and (3) for some persistent and bioaccumulative
pollutants, analyzes the ingestion route of exposure. In addition, the
RTR risk assessments consider aggregate cancer risk from all
carcinogens and aggregated noncancer HQs for all noncarcinogens
affecting the same target organ or target organ system.
    Although we are interested in placing source category and facility-
wide HAP risk in the context of total HAP risk from all sources
combined in the vicinity of each source, we are concerned about the
uncertainties of doing so. Estimates of total HAP risk from emission
sources other than those that we have studied in depth during this RTR
review would have significantly greater associated uncertainties than
the source category or facility-wide estimates. Such aggregate or
cumulative assessments would compound those uncertainties, making the
assessments too unreliable.

B. How do we perform the technology review?

    Our technology review focuses on the identification and evaluation
of developments in practices, processes, and control technologies that
have occurred since the MACT standards were promulgated. Where we
identify such developments, we analyze their technical feasibility,
estimated costs, energy implications, and non-air environmental
impacts. We also consider the emission reductions associated with
applying each development. This analysis informs our decision of
whether it is ``necessary'' to revise the emissions standards. In
addition, we consider the appropriateness of applying controls to new
sources versus retrofitting existing sources. For this exercise, we
consider any of the following to be a ``development'':
     Any add-on control technology or other equipment that was
not identified and considered during development of the original MACT
standards;
     Any improvements in add-on control technology or other
equipment (that were identified and considered during development of
the original

MACT standards) that could result in additional emissions reduction;
     Any work practice or operational procedure that was not
identified or considered during development of the original MACT
standards;
     Any process change or pollution prevention alternative
that could be broadly applied to the industry and that was not
identified or considered during development of the original MACT
standards; and
     Any significant changes in the cost (including cost
effectiveness) of applying controls (including controls the EPA
considered during the development of the original MACT standards).
    In addition to reviewing the practices, processes, and control
technologies that were considered at the time we originally developed
the NESHAP, we review a variety of data sources in our investigation of
potential practices, processes, or controls to consider. See sections
II.C and II.D of this preamble for information on the specific data
sources that were reviewed as part of the technology review.

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

    In this section, we provide a complete description of the types of
analyses that we generally perform during the risk assessment process.
In some cases, we do not perform a specific analysis because it is not
relevant. For example, in the absence of emissions of HAP known to be
persistent and bioaccumulative in the environment (PB-HAP), we would
not perform a multipathway exposure assessment. Where we do not perform
an analysis, we state that we do not and provide the reason. While we
present all of our risk assessment methods, we only present risk
assessment results for the analyses actually conducted (see sections
IV.B and IV.G).
    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 the Boat Manufacturing
NESHAP rulemaking contains the following document which provides more
information on the risk assessment inputs and models: Residual Risk
Assessment for Boat Manufacturing Source Category in Support of the
2018 Risk and Technology Review Proposed Rule. The docket for the
Reinforced Plastic Composites Production NESHAP rulemaking contains the
following document which provides more information on the risk
assessment inputs and models: Residual Risk Assessment for Reinforced
Plastic Composites Production Source Category in Support of the 2018
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; \4\ and described in the SAB review report
issued in 2010. They are also consistent with the key recommendations
contained in that report.
---------------------------------------------------------------------------

    \4\ U.S. EPA. Risk and Technology Review (RTR) Risk Assessment
Methodologies: For Review by the EPA's Science Advisory Board with
Case Studies--MACT I Petroleum Refining Sources and Portland Cement
Manufacturing, June 2009. EPA-452/R-09-006. https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
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1. How did we estimate actual emissions and identify the emissions
release characteristics?
    The actual emissions and the emission release characteristics for
each facility in each of the two source categories were obtained from
the 2014 NEI. In addition, the EPA provided draft actual emissions data
and stack parameters to facilities in the two source categories for
review and confirmation. In some cases, facilities were contacted to
confirm emissions that appeared to be outliers, that were otherwise
inconsistent with our understanding of the industry, or that were
associated with high risk values in our initial risk screening
analyses. Where appropriate, emission values and release
characteristics were corrected, based on revised stack parameter
information provided by the facilities. These revisions were documented
and are included in the docket for each source category. Additional
information on the development of the modeling file for each source
category, including the development of the actual emissions and
emissions release characteristics, can be found in Appendix 1 to the
Residual Risk Assessment for Boat Manufacturing Source Category in
Support of the 2018 Risk and Technology Review Proposed Rule document
and Appendix 1 to the Residual Risk Assessment for Reinforced Plastic
Composites Production Source Category in Support of the 2018 Risk and
Technology Review Proposed Rule document, located in the docket for
each source category (Docket ID No. EPA-HQ-OAR-2016-0447 for the Boat
Manufacturing NESHAP and Docket ID No. EPA-HQ-OAR-2016-0449 for the
Reinforced Plastic Composites Production NESHAP).
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include
estimates of the mass of HAP emitted during a specified annual time
period. These ``actual'' emission levels are often lower than the
emission levels allowed under the requirements of the current MACT
standards. The emissions allowed under the MACT standards are referred
to as the ``MACT-allowable'' emissions. We discussed the consideration
of both MACT-allowable and actual emissions in the final Coke Oven
Batteries RTR (70 FR 19998-19999, April 15, 2005) and in the proposed
and final Hazardous Organic NESHAP RTR (71 FR 34428, June 14, 2006, and
71 FR 76609, December 21, 2006, respectively). In those actions, we
noted that assessing the risk at the MACT-allowable level is inherently
reasonable since that risk reflects the maximum level facilities could
emit and still comply with national emission standards. We also
explained that it is reasonable to consider actual emissions, where
such data are available, in both steps of the risk analysis, in
accordance with the Benzene NESHAP approach. (54 FR 38044, September
14, 1989.)
    The MACT for each of the two source categories includes HAP limits
for materials (i.e., resin and gel coats) used during open molding
operations. A majority of the facilities in both source categories use
compliant materials to demonstrate compliance. The EPA's actual
emissions estimates were based on the category information reported in
the 2014 NEI. Since the majority of facilities use compliant materials,
it is reasonable to assume that the actual emissions and the allowable
emissions are equal. This is because the allowable limits of the MACT
represent the HAP content of the materials being used. Further, this
compliance approach is referenced in, and, therefore, required by
facility permits. However, to supplement this information, and to
estimate a more conservative allowable emissions multiplier, the EPA
gathered current and historical publicly available category-specific
data from the U.S. Census Bureau over a 5-year period

(2010 to 2014). Based an analysis of the source categories, and the
utilization information indicated by the U.S. Census Bureau data for
both source categories, the EPA calculated allowable emissions by
developing a multiplier applied to the current actual emission rates.
The multiplier is based on historical data and utilization rates for
each category for the years 2010 to 2014. The multiplier developed for
both source categories is the ratio of the peak utilization rate to the
average utilization rate for the years 2005 to 2014. Details regarding
the development of the allowable multiplier are presented in the
memorandum, Emissions Data for the National Emission Standards for
Hazardous Air Pollutants for Boat Manufacturing and the National
Emission Standards for Hazardous Air Pollutants for Reinforced Plastic
Composites Production, located in the docket for each source category
(Docket ID No. EPA-HQ-OAR-2016-0447 for the Boat Manufacturing NESHAP
and Docket ID No. EPA-HQ-OAR-2016-0449 for the Reinforced Plastic
Composites Production NESHAP).
3. How do we conduct dispersion modeling, determine inhalation
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations
and health risk from the source category addressed in this proposal
were estimated using the Human Exposure Model (HEM-3).\5\ 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 kilometer (km) of the modeled sources,
and (3) estimating individual and population-level inhalation risk
using the exposure estimates and quantitative dose-response
information.
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    \5\ For more information about HEM-3, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
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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.\6\ 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 \7\
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.
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    \6\ 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).
    \7\ A census block is the smallest geographic area for which
census statistics are tabulated.
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b. Risk From Chronic Exposure to HAP
    In developing the risk assessment for chronic exposures, we use the
estimated annual average ambient air concentrations of each HAP emitted
by each source in the source category. The HAP air concentrations at
each nearby census block centroid located within 50 km of the facility
are a surrogate for the chronic inhalation exposure concentration for
all the people who reside in that census block. A distance of 50 km is
consistent with both the analysis supporting the 1989 Benzene NESHAP
(54 FR 38044, September 14, 1989) and the limitations of Gaussian
dispersion models, including AERMOD.
    For each facility, we calculate the MIR as the cancer risk
associated with a continuous lifetime (24 hours per day, 7 days per
week, 52 weeks per year, 70 years) exposure to the maximum
concentration at the centroid of each inhabited census block. We
calculate individual cancer risk by multiplying the estimated lifetime
exposure to the ambient concentration of each HAP (in micrograms per
cubic meter ([mu]g/m\3\)) by its unit risk estimate (URE). The URE is
an upper-bound estimate of an individual's incremental risk of
contracting cancer over a lifetime of exposure to a concentration of 1
microgram of the pollutant per cubic meter of air. For residual risk
assessments, we generally use UREs from the EPA's Integrated Risk
Information System (IRIS). For carcinogenic pollutants without IRIS
values, we look to other reputable sources of cancer dose-response
values, often using California EPA (CalEPA) UREs, where available. In
cases where new, scientifically credible dose-response values have been
developed in a manner consistent with 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.
    In March 2018, the International Agency for Research on Cancer
(IARC) revised the weight of evidence classification of styrene to
Group 2A--``probably carcinogenic to humans.'' Presently, the EPA's
IRIS database and other reputable peer-reviewed sources of cancer dose-
response values are not available to assess cancer risks for this
pollutant.\8\
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    \8\ https://monographs.iarc.fr/list-of-classifications-volumes/.
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    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 \9\ 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.
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    \9\ 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.
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    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. We use the peak hourly emission rate,\10\ worst-case
dispersion conditions, and, in accordance with our mandate under
section 112 of the CAA, the point of highest off-site exposure to
assess the potential risk to the maximally exposed individual.
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    \10\ 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 to account for
variability. This is documented in Residual Risk Assessment for Boat
Manufacturing Source Category in Support of the 2018 Risk and
Technology Review Proposed Rule document and the Residual Risk
Assessment for Reinforced Plastic Composites Production Source
Category in Support of the 2018 Risk and Technology Review Proposed
Rule, and in Appendix 5 of the report: Analysis of Data on Short-
term Emission Rates Relative to Long-term Emission Rates. 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 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.'' \11\ 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.\12\ 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 parts per million (ppm) or milligrams per
cubic meter (mg/m\3\)) of a substance above which it is predicted that
the general population, including susceptible individuals, could
experience notable discomfort, irritation, or certain asymptomatic
nonsensory effects. However, the effects are not disabling and are
transient and reversible upon cessation of exposure.'' The document
also notes that ``Airborne concentrations below AEGL-1 represent
exposure levels that can produce mild and progressively increasing but
transient and nondisabling odor, taste, and sensory irritation or
certain asymptomatic, nonsensory effects.'' Id. AEGL-2 are defined as
``the airborne concentration (expressed as parts per million or
milligrams per cubic meter) of a substance above which it is predicted
that the general population, including susceptible individuals, could
experience irreversible or other serious, long-lasting adverse health
effects or an impaired ability to escape.'' Id.
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    \11\ 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.
    \12\ 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.'' \13\ 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.
---------------------------------------------------------------------------

    \13\ 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 the Boat Manufacturing and Reinforced Plastic Composites
Production source categories, the hourly emission rates of the various
HAP will not have high variability during the manufacturing processes
and, therefore, are expected to remain constant over the time the
process is operating. This is because the application of resins and gel
coats, adhesives, foam, and other regulated sources of HAP in the
source categories are most efficient when applied at a constant
pressure, with maximum coverage, with the most efficient spray patterns
and number of passes made by the operator. Based on this information,
the default acute emission factor of 10 times the annual hourly
emission rate is not reasonable for the Boat Manufacturing and
Reinforced Plastic Composites Production source categories. However,
many facilities do not operate three shifts a day. Therefore, a days
worth of emissions may occur over a time period of as little as 8
hours. With this understanding of the processes, we, therefore, assumed
the maximum rate of emissions would occur in this 8-hour period each
day. Based on this information, an acute emission factor of 3 was
calculated to be applied to actual annual hourly emission rates,
derived from the ratio of an 8-hour shift in a 24-hour day. A further
discussion of why this factor was chosen can be found in the
memorandum, Emissions Data for the National Emission Standards for
Hazardous Air Pollutants for Boat Manufacturing and the National
Emission Standards for Hazardous Air Pollutants for Reinforced Plastic
Composites Production, available in the dockets for this rulemaking
(Docket ID No. EPA-HQ-OAR-2016-0447 for the Boat Manufacturing NESHAP
and Docket ID No. EPA-HQ-OAR-2016-0449 for the Reinforced Plastic
Composites Production NESHAP).
    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 (even under the conservative assumptions of the screening
assessment), and no further analysis is performed for these HAP. In
cases where an acute HQ from the screening step is greater than 1, we
consider additional site-specific data to develop a more refined
estimate of the potential for acute exposures of concern. These
refinements are discussed more fully in the Residual Risk Assessment
for Boat Manufacturing Source Category in Support of the 2018 Risk and
Technology Review Proposed Rule document and the Residual Risk
Assessment for Reinforced Plastic Composites Production Source Category
in Support of the 2018 Risk and Technology Review Proposed Rule
document, which are available in the docket for each of the respective
source categories.
4. How do we conduct the multipathway exposure and risk screening
assessment?
    The EPA conducts a tiered screening assessment examining the
potential for significant human health risks due to exposures via
routes other than inhalation (i.e., ingestion). We first determine
whether any sources in the source categories emit any HAP known to be
PB-HAP, as identified in the EPA's Air Toxics Risk Assessment Library
(See Volume 1, Appendix D, at https://www2.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the Boat Manufacturing source category, we identified PB-HAP
emissions of arsenic, polycyclic organic matter (POM), and cadmium, and
for the Reinforced Plastic Composites Production source category, we
identified PB-HAP emissions of arsenic, POM, cadmium, and mercury, so
we proceeded to the next step of the evaluation. In this step, we
determine whether the facility-specific emission rates of the emitted
PB-HAP are large enough to create the potential for significant human
health risk through ingestion exposure under reasonable worst-case
conditions. To facilitate this step, we use previously developed
screening threshold emission rates for several PB-HAP that are based on
a hypothetical upper-end screening exposure scenario developed for use
in conjunction with the EPA's Total Risk Integrated Methodology.Fate,
Transport, and Ecological Exposure (TRIM.FaTE) model. The PB-HAP with
screening threshold emission rates are arsenic compounds, cadmium
compounds, chlorinated dibenzodioxins and furans, mercury compounds,
and POM. Based on the EPA estimates of toxicity and bioaccumulation
potential, the pollutants above represent a conservative list for
inclusion in multipathway risk assessments for RTR rules. (See Volume
1, Appendix D at https://www.epa.gov/sites/production/files/201308/documents/volume_1_reflibrary.pdf). In the assessments for the Boat
Manufacturing source category, and for the Reinforced Plastic
Composites Production source category, we compare the facility-specific
emission rates of these PB-HAP to the screening threshold emission
rates for each PB-HAP to assess the potential for significant human
health risks via the ingestion pathway. We call this application of the
TRIM.FaTE model the Tier 1 screening assessment. The ratio of a
facility's actual emission rate to the Tier 1 screening threshold
emission rate is a ``screening value.''
    We derive the Tier 1 screening threshold emission rates for these
PB-HAP (other than lead compounds) to correspond to a maximum excess
lifetime cancer risk of 1-in-1 million (i.e., for arsenic compounds,
polychlorinated dibenzodioxins and furans and POM) or, for HAP that
cause noncancer health effects (i.e., cadmium compounds and mercury
compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP
or combination of carcinogenic PB-HAP in the Tier 1 screening
assessment exceeds the Tier 1 screening threshold emission rate for any
facility (i.e., the screening value is greater than 1), we conduct a
second screening assessment, which we call the Tier 2 screening
assessment.
    In the Tier 2 screening assessment, the location of each facility
that exceeds a Tier 1 screening threshold emission rate is used to
refine the assumptions associated with the Tier 1 fisher and farmer
exposure scenarios at that facility. A key assumption in the Tier 1
screening assessment is that a lake and/or farm is located near the
facility. As part of the Tier 2 screening assessment, we use a United
States Geological Survey (USGS) database to identify actual waterbodies
within 50 km of each facility. We also examine the differences between
local meteorology near the facility and the meteorology used in the
Tier 1 screening assessment. We then adjust the previously-developed
Tier 1 screening threshold emission rates for each PB-HAP for each
facility based on an understanding of how exposure concentrations
estimated for the screening scenario change with the use of local
meteorology and USGS waterbody data. If the PB-HAP emission rates for a
facility exceed the Tier 2 screening threshold emission rates and data
are available, we may conduct a Tier 3 screening assessment. If PB-HAP
emission rates do not exceed a Tier 2 screening value of 1, we consider
those PB-HAP emissions to pose risks below a level of concern.

    There are several analyses that can be included in a Tier 3
screening assessment, depending upon the extent of refinement
warranted, including validating that the lakes are fishable,
considering plume-rise to estimate emissions lost above the mixing
layer, and considering hourly effects of meteorology and plume rise on
chemical fate and transport. If the Tier 3 screening assessment
indicates that risks above levels of concern cannot be ruled out, the
EPA may further refine the screening assessment through a site-specific
assessment.
    In evaluating the potential multipathway risk from emissions of
lead compounds reported by both source categories, rather than
developing a screening threshold emission rate, we compare maximum
estimated chronic inhalation exposure concentrations to the level of
the current National Ambient Air Quality Standard (NAAQS) for lead.\14\
Values below the level of the primary (health-based) lead NAAQS are
considered to have a low potential for multipathway risk.
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    \14\ In doing so, the EPA notes that the legal standard for a
primary NAAQS--that a standard is requisite to protect public health
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other
things, that the standard provide an ``ample margin of safety to
protect public health''). However, the primary lead NAAQS is a
reasonable measure of determining risk acceptability (i.e., the
first step of the Benzene NESHAP analysis) since it is designed to
protect the most susceptible group in the human population--
children, including children living near major lead emitting
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition,
applying the level of the primary lead NAAQS at the risk
acceptability step is conservative, since that primary lead NAAQS
reflects an adequate margin of safety.
---------------------------------------------------------------------------

    For further information on the multipathway assessment approach,
see the Residual Risk Assessment for Boat Manufacturing Source Category
in Support of the 2018 Risk and Technology Review Proposed Rule
document and the Residual Risk Assessment for Reinforced Plastic
Composites Production Source Category in Support of the 2018 Risk and
Technology Review Proposed Rule document, which are available in the
respective dockets for the source categories in this action.
5. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological
Benchmarks
    The EPA conducts a screening assessment to examine the potential
for an adverse environmental effect as required under section
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse
environmental effect'' as ``any significant and widespread adverse
effect, which may reasonably be anticipated, to wildlife, aquatic life,
or other natural resources, including adverse impacts on populations of
endangered or threatened species or significant degradation of
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as
``environmental HAP,'' in its screening assessment: Six PB-HAP and two
acid gases. The PB-HAP included in the screening assessment are arsenic
compounds, cadmium compounds, dioxins/furans, POM, mercury (both
inorganic mercury and methyl mercury), and lead compounds. The acid
gases included in the screening assessment are 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 Boat Manufacturing Source Category in Support of the
2018 Risk and Technology Review Proposed Rule document and the Residual
Risk Assessment for Reinforced Plastic Composites Production Source
Category in Support of the 2018 Risk and Technology Review Proposed
Rule document, which are available in the docket for the source
categories in this action.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first
determined whether any facilities in the Boat Manufacturing or
Reinforced Plastic Composites Production source categories emitted any
of the environmental HAP. For the Boat Manufacturing source category,
we identified emissions of arsenic, POM, cadmium, and HCl. For the
Reinforced Plastic Composites Production source category, we identified
emissions of arsenic, POM, cadmium, mercury, and HCl. Because one or
more of the environmental HAP evaluated above are emitted by at least
one facility in the source categories, 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. With the
exception of lead, the environmental risk screening assessment for PB-
HAP consists of three tiers. The first tier of the environmental risk
screening assessment uses the same health-protective conceptual model
that is used for the Tier 1 human health screening assessment.
TRIM.FaTE model simulations were used to back-calculate Tier 1
screening threshold emission rates. The screening threshold emission
rates represent the emission rate in tpy that results in media
concentrations at the facility that equal the relevant ecological
benchmark. To assess emissions from each facility in the category, the
reported emission rate for each PB-HAP was compared to the Tier 1
screening threshold emission rate for that PB-HAP for each assessment
endpoint and effect level. If emissions from a facility do not exceed
the Tier 1 screening threshold emission rate, the facility ``passes''
the screening assessment, and, therefore, is not evaluated further
under the screening

approach. If emissions from a facility exceed the Tier 1 screening
threshold emission rate, we evaluate the facility further in Tier 2.
    In Tier 2 of the environmental screening assessment, the screening
threshold emission rates are adjusted to account for local meteorology
and the actual location of lakes in the vicinity of facilities that did
not pass the Tier 1 screening assessment. For soils, we evaluate the
average soil concentration for all soil parcels within a 7.5-km radius
for each facility and PB-HAP. For the water, sediment, and fish tissue
concentrations, the highest value for each facility for each pollutant
is used. If emission concentrations from a facility do not exceed the
Tier 2 screening threshold emission rate, the facility ``passes'' the
screening assessment and typically is not evaluated further. If
emissions from a facility exceed the Tier 2 screening threshold
emission rate, we evaluate the facility further in Tier 3.
    As in the multipathway human health risk assessment, in Tier 3 of
the environmental screening assessment, we examine the suitability of
the lakes around the facilities to support life and remove those that
are not suitable (e.g., lakes that have been filled in or are
industrial ponds), adjust emissions for plume-rise, and conduct hour-
by-hour time-series assessments. If these Tier 3 adjustments to the
screening threshold emission rates still indicate the potential for an
adverse environmental effect (i.e., facility emission rate exceeds the
screening threshold emission rate), we may elect to conduct a more
refined assessment using more site-specific information. If, after
additional refinement, the facility emission rate still exceeds the
screening threshold emission rate, the facility may have the potential
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from
lead, we compared the average modeled air concentrations (from HEM-3)
of lead around each facility in the source category to the level of the
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable
means of evaluating environmental risk because it is set to provide
substantial protection against adverse welfare effects which can
include ``effects on soils, water, crops, vegetation, man-made
materials, animals, wildlife, weather, visibility and climate, damage
to and deterioration of property, and hazards to transportation, as
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the
potential phytotoxicity and reduced productivity of plants due to
chronic exposure to HF and HCl. The environmental risk screening
methodology for acid gases is a single-tier screening assessment that
compares modeled ambient air concentrations (from AERMOD) to the
ecological benchmarks for each acid gas. To identify a potential
adverse environmental effect (as defined in section 112(a)(7) of the
CAA) from emissions of HF and HCl, we evaluate the following metrics:
The size of the modeled area around each facility that exceeds the
ecological benchmark for each acid gas, in acres and km\2\; the
percentage of the modeled area around each facility that exceeds the
ecological benchmark for each acid gas; and the area-weighted average
screening value around each facility (calculated by dividing the area-
weighted average concentration over the 50-km modeling domain by the
ecological benchmark for each acid gas). For further information on the
environmental screening assessment approach, see Appendix 9 of the
Residual Risk Assessment for Boat Manufacturing Source Category in
Support of the 2018 Risk and Technology Review Proposed Rule document
and the Residual Risk Assessment for Reinforced Plastic Composites
Production Source Category in Support of the 2018 Risk and Technology
Review Proposed Rule document, which are available in the docket for
the source categories in 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 the source categories in this action, we conducted the facility-
wide assessment using datasets compiled from the 2014 NEI. The source
category records of that NEI dataset were removed, evaluated, and
updated as described in section II.C of this preamble: What data
collection activities were conducted to support this action? Once a
quality assured source category dataset was available, it was placed
back with the remaining records from the NEI for that facility. The
facility-wide file was then used to analyze risks due to the inhalation
of HAP that are emitted ``facility-wide'' for the populations residing
within 50 km of each facility, consistent with the methods used for the
source category analysis described above. For these facility-wide risk
analyses, the modeled source category risks were compared to the
facility-wide risks to determine the portion of the facility-wide risks
that could be attributed to the source category addressed in this
proposal. We also specifically examined the facility that was
associated with the highest estimate of risk and determined the
percentage of that risk attributable to the source category of
interest. The Residual Risk Assessment for Boat Manufacturing Source
Category in Support of the 2018 Risk and Technology Review Proposed
Rule document and the Residual Risk Assessment for Reinforced Plastic
Composites Production Source Category in Support of the 2018 Risk and
Technology Review Proposed Rule document, available through the docket
for the source categories in this action, provides the methodology and
results of the facility-wide analyses, including all facility-wide
risks and the percentage of source category contribution to facility-
wide risks.
7. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for this proposal. Although
uncertainty exists, we believe that our approach, which used
conservative tools and assumptions, ensures that our decisions are
health and environmentally protective. A brief discussion of the
uncertainties in the RTR emissions datasets, dispersion modeling,
inhalation exposure estimates, and dose-response relationships follows
below. Also included are those uncertainties specific to our acute
screening assessments, multipathway screening assessments, and our
environmental risk screening assessments. A more thorough discussion of
these uncertainties is included in the Residual Risk Assessment for
Boat Manufacturing Source Category in Support of the 2018 Risk and
Technology Review Proposed Rule document and the Residual Risk
Assessment for Reinforced Plastic Composites Production Source Category
in Support of the 2018 Risk and Technology Review Proposed Rule
document, which are available in the source category dockets for this
action.

a. Uncertainties in the RTR Emissions Dataset
    Although the development of the RTR emissions datasets involved
quality assurance/quality control processes, the accuracy of emissions
values will vary depending on the source of the data, the degree to
which data are incomplete or missing, the degree to which assumptions
made to complete the datasets are accurate, errors in emission
estimates, and other factors. The emission estimates considered in the
analysis for each source category generally are annual totals for 2014,
and they do not reflect short-term fluctuations during the course of a
year or variations from year to year. The estimates of peak hourly
emission rates for the acute effects screening assessment were based on
an emission adjustment factor applied to the average annual hourly
emission rates, which are intended to account for emission fluctuations
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration
estimates associated with any model, including the EPA's recommended
regulatory dispersion model, AERMOD. In using a model to estimate
ambient pollutant concentrations, the user chooses certain options to
apply. For RTR assessments, we select some model options that have the
potential to overestimate ambient air concentrations (e.g., not
including plume depletion or pollutant transformation). We select other
model options that have the potential to underestimate ambient impacts
(e.g., not including building downwash). Other options that we select
have the potential to either under- or overestimate ambient levels
(e.g., meteorology and receptor locations). On balance, considering the
directional nature of the uncertainties commonly present in ambient
concentrations estimated by dispersion models, the approach we apply in
the RTR assessments should yield unbiased estimates of ambient HAP
concentrations. We also note that the selection of meteorology dataset
location could have an impact on the risk estimates. As we continue to
update and expand our library of meteorological station data used in
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant
facilities and emission points, as well as to develop accurate
estimates of the annual emission rates for all relevant HAP, the
uncertainties in our emission inventory likely dominate the
uncertainties in the exposure assessment. Some uncertainties in our
exposure assessment include human mobility, using the centroid of each
census block, assuming lifetime exposure, and assuming only outdoor
exposures. For most of these factors, there is neither an under nor
overestimate when looking at the maximum individual risk or the
incidence, but the shape of the distribution of risks may be affected.
With respect to outdoor exposures, actual exposures may not be as high
if people spend time indoors, especially for very reactive pollutants
or larger particles. For all factors, we reduce uncertainty when
possible. For example, with respect to census-block centroids, we
analyze large blocks using aerial imagery and adjust locations of the
block centroids to better represent the population in the blocks. We
also add additional receptor locations where the population of a block
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from
chronic exposures and noncancer effects from both chronic and acute
exposures. Some uncertainties are generally expressed quantitatively,
and others are generally expressed in qualitative terms. We note, as a
preface to this discussion, a point on dose-response uncertainty that
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment;
namely, that ``the primary goal of EPA actions is protection of human
health; accordingly, as an Agency policy, risk assessment procedures,
including default options that are used in the absence of scientific
data to the contrary, should be health protective'' (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.\15\
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.\16\
Chronic noncancer RfC and reference dose 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,\17\ which considers uncertainty, variability, and gaps
in the available data. The UFs are applied to derive dose-response
values that are intended to protect against appreciable risk of
deleterious effects.
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    \15\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \16\ 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.
    \17\ See A Review of the Reference Dose and Reference
Concentration Processes, U.S. EPA, December 2002, and Methods for
Derivation of Inhalation Reference Concentrations and Application of
Inhalation Dosimetry, U.S. EPA, 1994.
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    Many of the UFs used to account for variability and uncertainty in
the development of acute dose-response values are quite similar to
those developed for chronic durations. Additional adjustments are often
applied to account for uncertainty in extrapolation from observations
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all
acute dose-response values are developed for the same purpose, and care
must be taken when interpreting the results of an acute assessment of
human health effects relative to the dose-response value or values
being exceeded. Where relevant to the estimated exposures, the lack of
acute dose-response values at different levels of severity should be
factored into the risk characterization as potential uncertainties.
    Uncertainty also exists in the selection of ecological benchmarks
for the environmental risk screening assessment. We established a
hierarchy of preferred benchmark sources to allow selection of
benchmarks for each environmental HAP at each ecological assessment
endpoint. We searched for benchmarks for three effect levels (i.e., no-
effects level, threshold-effect level, and probable effect level), but
not all combinations of ecological assessment/environmental HAP had
benchmarks for all three effect levels. Where multiple effect levels
were available for a particular HAP and assessment endpoint, we used
all of the available effect levels to help us determine whether risk
exists and whether the risk

could be considered significant and widespread.
    Although we make every effort to identify appropriate human health
effect dose-response values for all pollutants emitted by the sources
in this risk assessment, some HAP emitted by these source categories
are lacking dose-response assessments. Accordingly, these pollutants
cannot be included in the quantitative risk assessment, which could
result in quantitative estimates understating HAP risk. To help to
alleviate this potential underestimate, where we conclude similarity
with a HAP for which a dose-response value is available, we use that
value as a surrogate for the assessment of the HAP for which no value
is available. To the extent use of surrogates indicates appreciable
risk, we may identify a need to increase priority for an IRIS
assessment for that substance. We additionally note that, generally
speaking, HAP of greatest concern due to environmental exposures and
hazard are those for which dose-response assessments have been
performed, reducing the likelihood of understating risk. Further, HAP
not included in the quantitative assessment are assessed qualitatively
and considered in the risk characterization that informs the risk
management decisions, including consideration of HAP reductions
achieved by various control options.
    For 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 humans
at the location of the maximum concentration. In the acute screening
assessment that we conduct under the RTR program, we assume that peak
emissions from the source category and worst-case meteorological
conditions co-occur, thus, resulting in maximum ambient concentrations.
These two events are unlikely to occur at the same time, making these
assumptions conservative. We then include the additional assumption
that a person is located at this point during this same time period.
For this source category, these assumptions would tend to be worst-case
actual exposures, as it is unlikely that a person would be located at
the point of maximum exposure during the time when peak emissions and
worst-case meteorological conditions occur simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening
Assessments
    For each source category, we generally rely on site-specific levels
of PB-HAP or environmental HAP emissions to determine whether a refined
assessment of the impacts from multipathway exposures is necessary or
whether it is necessary to perform an environmental screening
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant
concentrations and human exposures for five PB-HAP (dioxins, POM,
mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For
lead, we use AERMOD to determine ambient air concentrations, which are
then compared to the secondary NAAQS standard for lead. Two important
types of uncertainty associated with the use of these models in RTR
risk assessments and inherent to any assessment that relies on
environmental modeling are model uncertainty and input uncertainty.\18\
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    \18\ 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 RTR.
    Input uncertainty is concerned with how accurately the models have
been configured and parameterized for the assessment at hand. For Tier
1 of the multipathway and environmental screening assessments, we
configured the models to avoid underestimating exposure and risk. This
was accomplished by selecting upper-end values from nationally
representative datasets for the more influential parameters in the
environmental model, including selection and spatial configuration of
the area of interest, lake location and size, meteorology, surface
water, soil characteristics, and structure of the aquatic food web. We
also assume an ingestion exposure scenario and values for human
exposure factors that represent reasonable maximum exposures.
    In Tier 2 of the multipathway and environmental screening
assessments, we refine the model inputs to account for meteorological
patterns in the vicinity of the facility versus using upper-end
national values, and we identify the actual location of lakes near the
facility rather than the default lake location that we apply in Tier 1.
By refining the screening approach in Tier 2 to account for local
geographical and meteorological data, we decrease the likelihood that
concentrations in environmental media are overestimated, thereby
increasing the usefulness of the screening assessment. In Tier 3 of the
screening assessments, we refine the model inputs again to account for
hour-by-hour plume rise and the height of the mixing layer. We can also
use those hour-by-hour meteorological data in a TRIM.FaTE run using the
screening configuration corresponding to the lake location. These
refinements produce a more accurate estimate of chemical concentrations
in the media of interest, thereby reducing the uncertainty with those
estimates. The assumptions and the associated uncertainties regarding
the selected ingestion exposure scenario are the same for all three
tiers.
    For the environmental screening assessment for acid gases, we
employ a single-tiered approach. We use the modeled air concentrations
and compare those with ecological benchmarks.
    For all tiers of the multipathway and environmental screening
assessments, our approach to addressing model input uncertainty is
generally cautious. We choose model inputs from the upper end of the
range of possible values for the influential parameters used in the
models, and we assume that the exposed individual exhibits ingestion

behavior that would lead to a high total exposure. This approach
reduces the likelihood of not identifying high risks for adverse
impacts.
    Despite the uncertainties, when individual pollutants or facilities
do not exceed screening threshold emission rates (i.e., screen out), we
are confident that the potential for adverse multipathway impacts on
human health is very low. On the other hand, when individual pollutants
or facilities do exceed screening threshold emission rates, it does not
mean that impacts are significant, only that we cannot rule out that
possibility and that a refined assessment for the site might be
necessary to obtain a more accurate risk characterization for the
source category.
    The EPA evaluates the following HAP in the multipathway and/or
environmental risk screening assessments, where applicable: Arsenic,
cadmium, dioxins/furans, lead, mercury (both inorganic and methyl
mercury), POM, HCl, and HF. These HAP represent pollutants that can
cause adverse impacts either through direct exposure to HAP in the air
or through exposure to HAP that are deposited from the air onto soils
and surface waters and then through the environment into the food web.
These HAP represent those HAP for which we can conduct a meaningful
multipathway or environmental screening risk assessment. For other HAP
not included in our screening assessments, the model has not been
parameterized such that it can be used for that purpose. In some cases,
depending on the HAP, we may not have appropriate multipathway models
that allow us to predict the concentration of that pollutant. The EPA
acknowledges that other HAP beyond these that we are evaluating may
have the potential to cause adverse effects and, therefore, the EPA may
evaluate other relevant HAP in the future, as modeling science and
resources allow.

IV. Analytical Results and Proposed Decisions

A. What are the results of the risk assessment and analyses for the
Boat Manufacturing source category?

1. Inhalation Risk Assessment Results
    Table 2 of this preamble provides an overall summary of the
inhalation risk results. The results of the chronic baseline inhalation
cancer risk assessment indicate that, based on estimates of current
actual and allowable emissions, the MIR posed by the Boat Manufacturing
source category was estimated to be 0.2-in-1 million and 0.3-in-1
million, respectively, from HAP being emitted from the open molding
(resin/gelcoat) manufacturing process. The total estimated cancer
incidence from the Boat Manufacturing source category based on actual
emission levels is 0.00001 excess cancer cases per year, or one case in
every 100,000 years. The total estimated cancer incidence from boat
manufacturing industry emission sources based on allowable emission
levels is 0.00002 excess cancer cases per year, or one case in every
50,000 years. Emissions of nickel compounds, ethyl benzene, and
tetrachloroethene contributed 95 percent to this cancer incidence.
Based upon actual or allowable emissions, no people were exposed to
cancer risks greater than or equal to 1-in-1 million.

                                   Table 2--Inhalation Risk Assessment Summary for Boat Manufacturing Source Category
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                                           Cancer MIR (in-1 million)                                              Population
                                -----------------------------------------------     Cancer        Population     with risk of
                                                                                incidence    with risk of 1-     10-in-1     Max chronic noncancer HI
                                     Based on actual       Based on allowable     (cases per     in-1 million     million or    (actuals and allowables)
                                        emissions              emissions             year)        or greater        greater
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Source category................  0.2 (nickel compounds,  0.3 (nickel                   0.00001               0               0  HI <1
                                  ethyl benzene,          compounds, ethyl
                                  tetrachloroethene).     benzene,
                                                          tetrachloroethene).
Whole Facility.................  0.4 (naphthalene).....  .....................         0.00004               0               0  HI = 1
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