[Federal Register: October 21, 2010 (Volume 75, Number 203)]
[Proposed Rules]
[Page 65067-65149]
[DOCID:fr21oc10-24]

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Part II

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutant Emissions: Hard
and Decorative Chromium Electroplating and Chromium Anodizing Tanks;
Group I Polymers and Resins; Marine Tank Vessel Loading Operations;
Pharmaceuticals Production; The Printing and Publishing Industry; and
Steel Pickling--HCl Process Facilities and Hydrochloric Acid
Regeneration Plants; Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2010-0600; FRL-9203-7]
RIN 2060-AO91

National Emission Standards for Hazardous Air Pollutant
Emissions: Hard and Decorative Chromium Electroplating and Chromium
Anodizing Tanks; Group I Polymers and Resins; Marine Tank Vessel
Loading Operations; Pharmaceuticals Production; The Printing and
Publishing Industry; and Steel Pickling--HCl Process Facilities and
Hydrochloric Acid Regeneration Plants

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; and supplemental notice of proposed rulemaking.

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SUMMARY: This action proposes how EPA will address the residual risk
and technology reviews conducted for two national emission standards
for hazardous air pollutants (NESHAP), and this action is a
supplemental notice of proposed rulemaking for an October 2008 action
that proposed how EPA would address the residual risk and technology
reviews for four NESHAP. The six NESHAP include 16 source categories,
12 of which are the subject of residual risk and technology reviews in
this package. This action proposes to modify the existing emissions
standards for eight source categories in three of the six NESHAP to
address certain emission sources not currently regulated under these
standards. It also proposes for all six NESHAP to address provisions
related to emissions during periods of startup, shutdown, and
malfunction. Finally, this action proposes changes to two of the six
NESHAP to correct editorial errors, make clarifications, or address
issues with implementation or determining compliance.

DATES: Comments. Comments must be received on or before December 6,
2010. Under the Paperwork Reduction Act, comments on the information
collection provisions are best assured of having full effect if the
Office of Management and Budget (OMB) receives a copy of your comments
on or before November 22, 2010.
    Public Hearing. We will hold a public hearing on November 5, 2010.
Persons requesting to speak at the public hearing must contact EPA by
November 1, 2010.

ADDRESSES: Comments. Submit your comments, identified by Docket ID No.
EPA-HQ-OAR-2010-0600, by one of the following methods:
     http://www.regulations.gov: Follow the on-line
instructions for submitting comments.
     E-mail<EMAIL_ADDRESS>Attention Docket ID No.
EPA-HQ-OAR-2010-0600.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2010-0600.
     Mail: U.S. Postal Service, send comments to: EPA Docket
Center, EPA West (Air Docket), Attention Docket ID No. EPA-HQ-OAR-2010-
0600, U.S. Environmental Protection Agency, Mailcode: 2822T, 1200
Pennsylvania Ave., NW., Washington, DC 20460. Please include a total of
two copies. In addition, please mail a copy of your comments on the
information collection provisions to the Office of Information and
Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk
Officer for EPA, 725 17th Street, NW., Washington, DC 20503.
     Hand Delivery: U.S. Environmental Protection Agency, EPA
West (Air Docket), Room 3334, 1301 Constitution Ave., NW., Washington,
DC 20004. Attention Docket ID No. EPA-HQ-OAR-2010-0600. Such deliveries
are only accepted during the Docket's normal hours of operation, and
special arrangements should be made for deliveries of boxed
information.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2010-0600. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
confidential business information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected through http://
www.regulations.gov or e-mail. The http://www.regulations.gov Web site
is an ``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov, your e-mail 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, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket, visit the EPA Docket Center homepage at http://www.epa.gov/
epahome/dockets.htm.
    Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2010-0600. All documents in the docket are
listed in the http://www.regulations.gov index. Although listed in the
index, some information is not publicly available, e.g., 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 http://
www.regulations.gov or in hard copy at the EPA Docket Center, EPA West,
Room 3334, 1301 Constitution Ave., 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>.
    Public Hearing. We will hold a public hearing concerning this
proposed rule on November 5, 2010, from 9 a.m. to 7 p.m. Persons
interested in presenting oral testimony at the hearing should contact
Ms. Mary Tom Kissell, Sector Policies and Programs Division (E143-01),
Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, telephone number,
(919) 541-4516, by November 1, 2010. The public hearing will be held at
the U.S. Environmental Protection Agency--Research Triangle Park
Campus, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709. If
no one requests to speak at the public hearing by November 1, 2010,
then the public hearing will be cancelled and a notification of
cancellation posted on the following Web site: http://www.epa.gov/ttn/
oarpg/t3main.html.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Ms. Mary Tom Kissell, Sector Policies and Programs
Division (E143-01), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC 27711,
telephone (919) 541-

4516; fax number:<PHONE_NUMBER>; and e-mail address:
<EMAIL_ADDRESS>For specific information regarding the risk
modeling methodology, contact Ms. Elaine Manning, Health and
Environmental Impacts Division (C539-02), Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC 27711; telephone number:<PHONE_NUMBER>; fax number:
(919) 541-0840; and e-mail address<EMAIL_ADDRESS>For
information about the applicability of these six NESHAP to a particular
entity, contact the appropriate person listed in Table 1 to this
preamble.

SUPPLEMENTARY INFORMATION:

                                     Table 1--List of EPA Contacts for the NESHAP Addressed in This Proposed Action
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               NESHAP for:                                   OECA contact \1\                                        OAQPS contact \2\
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Hard and Decorative Chromium              Scott Throwe,<PHONE_NUMBER><EMAIL_ADDRESS> Phil Mulrine,<PHONE_NUMBER><EMAIL_ADDRESS> Electroplating and Chromium Anodizing
 Tanks.
Group I Polymers and Resins Production..  Scott Throwe,<PHONE_NUMBER><EMAIL_ADDRESS> Randy McDonald,<PHONE_NUMBER>,
<EMAIL_ADDRESS>Marine Vessel Loading Operations........  Maria Malave,<PHONE_NUMBER><EMAIL_ADDRESS> Steve Shedd,<PHONE_NUMBER><EMAIL_ADDRESS>Pharmaceuticals Production..............  Marcia Mia,<PHONE_NUMBER><EMAIL_ADDRESS> Randy McDonald,<PHONE_NUMBER>,
<EMAIL_ADDRESS>Printing and Publishing Industry........  Len Lazarus,<PHONE_NUMBER><EMAIL_ADDRESS> David Salman,<PHONE_NUMBER><EMAIL_ADDRESS>Steel Pickling--HCl Process Facilities    Maria Malave,<PHONE_NUMBER><EMAIL_ADDRESS> Phil Mulrine,<PHONE_NUMBER><EMAIL_ADDRESS> and Hydrochloric Acid Regeneration
 Plants.
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\1\ OECA stands for EPA's Office of Enforcement and Compliance Assurance.
\2\ OAQPS stands for EPA's Office of Air Quality Planning and Standards.

I. Preamble Acronyms and Abbreviations

    Several acronyms and terms used to describe industrial processes,
data inventories, and risk modeling are included in this preamble.
While this may not be an exhaustive list, to ease the reading of this
preamble and for reference purposes, the following terms and acronyms
are defined here:

AERMOD--The air dispersion model used by the HEM-3 model
AEGL--Acute Exposure Guideline Levels
ANPRM--Advance Notice of Proposed Rulemaking
ASTM--An international standards organization that develops and
publishes voluntary consensus technical standards
ATCM--Airborne Toxics Control Measure
ATSDR--Agency for Toxic Substances and Disease Registry
BACT--Best Available Control Technology
bbl/yr--Barrels per Year
BID--Background Information Document
CalEPA--California Environmental Protection Agency
CARB--California Air Resources Board
CAA--Clean Air Act
CBI--Confidential Business Information
CEEL--Community Emergency Exposure Levels
CIIT--Chemical Industry Institute of Toxicology
CFR--Code of Federal Regulations
CMP--Composite Mesh Pad
CO--Carbon Monoxide
CO2--Carbon Dioxide
D/F--Dioxin/Furan
EED--Emission Elimination Device
EPA--Environmental Protection Agency
EPS--Eco Pickled Surface
ERPG--Emergency Response Planning Guidelines
HAP--Hazardous Air Pollutants
HCl--Hydrochloric Acid
HI--Hazard Index
HEM-3--Human Exposure Model version 3
HEPA--High Efficiency Particulate Air
HON--Hazardous Organic National Emissions Standards for Hazardous
Air Pollutants
HQ--Hazard Quotient
ICR--Information Collection Request
IRIS--Integrated Risk Information System
Km--Kilometer
LAER--Lowest Achievable Emission Rate
MACT--Maximum Achievable Control Technology
MACT Code--A code within the NEI used to identify processes included
in a source category
mg/dscm--Milligrams per Dry Standard Cubic Meter
MIR--Maximum Individual Risk
MTVLO--Marine Tank Vessel Loading Operations
NAC/AEGL Committee--National Advisory Committee for Acute Exposure
Guideline Levels for Hazardous Substances
NAICS--North American Industry Classification System
NAS--National Academy of Sciences
NATA--National Air Toxics Assessment
NESHAP--National Emissions Standards for Hazardous Air Pollutants
NEI--National Emissions Inventory
NOX--Nitrogen Oxide
NRC--National Research Council
NSR--New Source Review
NTTAA--National Technology Transfer and Advancement Act
OECA--Office of Enforcement and Compliance Assurance
OLD--Organic Liquids Distribution
OMB--Office of Management and Budget
PB-HAP--Hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PFC--Perfluorinated Chemical
PFOS--Perfluorooctyl Sulfonate
PM--Particulate Matter
POM--Polycyclic Organic Matter
RACT--Reasonably Available Control Technology
RBLC--RACT/BACT/LAER Clearinghouse
REL--CalEPA Chronic Reference Exposure Level
RFA--Regulatory Flexibility Act
RfC--Reference Concentration
RfD--Reference Dose
RTR--Residual Risk and Technology Review
SAB--Science Advisory Board
SCC--Source Classification Codes
SCS--Smooth Clean Surface
SF3--2000 Census of Population and Housing Summary File 3
SO2--Sulfur Dioxide
SOP--Standard Operating Procedures
SSM--Startup, Shutdown, and Malfunction
TOSHI--Target Organ-Specific Hazard Index
TPY--Tons Per Year
TRIM--Total Risk Integrated Modeling System
TTN--Technology Transfer Network
UF--Uncertainty Factor
UMRA--Unfunded Mandates Reform Act
URE--Unit Risk Estimate
VOC--Volatile Organic Compounds
WAFS--Wetting Agent/Fume Suppressant
WCSC--Waterborne Commerce Statistics Center
WWW--Worldwide Web

II. General Information

A. Does this action apply to me?

    The regulated industrial source categories that are the subject of
this proposal are listed in Table 2 to this preamble. Table 2 is not
intended to be exhaustive, but rather provides a guide for readers
regarding entities likely to be affected by the proposed action for the
source categories listed. These standards, and any changes considered
in this rulemaking, would be directly applicable to sources as a
Federal program. Thus, Federal, State, local, and tribal government
entities are not affected by this proposed action. The

regulated categories affected by this proposed action include:

                Table 2--NESHAP and Industrial Source Categories Affected by This Proposed Action
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                           NESHAP and source category                             NAICS code \1\   MACT code \2\
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Chromium Electroplating.......................  Chromium Anodizing Tanks........          332813            1607
                                                Decorative Chromium                       332813            1610
                                                 Electroplating.
                                                Hard Chromium Electroplating....          332813            1615
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Group I Polymers and Resins...................  Butyl Rubber Production.........          325212            1307
                                                Epichlorohydrin Elastomers                325212            1311
                                                 Production.
                                                Ethylene Propylene Rubber                 325212            1313
                                                 Production.
                                                Hypalon\TM\ Production \3\......          325212            1315
                                                Neoprene Production.............          325212            1320
                                                Nitrile Butadiene Rubber                  325212            1321
                                                 Production.
                                                Polybutadiene Rubber Production.          325212            1325
                                                Polysulfide Rubber Production             325212            1332
                                                 \3\.
                                                Styrene Butadiene Rubber and              325212            1339
                                                 Latex Production.
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Marine Vessel Loading Operations................................................            4883            0603
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Pharmaceuticals Production......................................................            3254            1201
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Printing and Publishing Industry................................................           32311            0714
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Steel Pickling--HCl Process Facilities and Hydrochloric Acid Regeneration Plants      3311, 3312            0310
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\1\ North American Industry Classification System.
\2\ Maximum Achievable Control Technology.
\3\ There are no longer any operating facilities in either the Hypalon\TM\ or Polysulfide Rubber source
  categories. Therefore, this proposal does not address these source categories.

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 proposal will also be available on the World Wide Web (WWW)
through the Technology Transfer Network (TTN). Following signature by
the EPA Administrator, a copy of this proposed action will be posted on
the TTN's policy and guidance page for newly proposed or promulgated
rules at the following address: http://www.epa.gov/ttn/atw/rrisk/
rtrpg.html. The TTN provides information and technology exchange in
various areas of air pollution control.
    Additional information is available on the residual risk and
technology review (RTR) Web page at http://www.epa.gov/ttn/atw/rrisk/
rtrpg.html. This information includes source category descriptions and
detailed emissions and other data that were used as inputs to the risk
assessments.

C. What should I consider as I prepare my comments for EPA?

    Submitting CBI. Do not submit information containing CBI to EPA
through http://www.regulations.gov or e-mail. Clearly mark the part or
all of the information that you claim to be CBI. For CBI information on
a disk or CD-ROM that you mail to EPA, mark the outside of the disk or
CD-ROM as CBI and then identify electronically within the disk or CD-
ROM the specific information that is claimed as CBI. In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket. If
you submit a CD-ROM or disk that does not contain CBI, mark the outside
of the disk or CD-ROM clearly that it does not contain CBI. Information
not marked as CBI will be included in the public docket and 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 CFR part 2. Send or deliver information identified as CBI
only to the following address: Roberto Morales, OAQPS Document Control
Officer (C404-02), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC 27711,
Attention Docket ID No. EPA-HQ-OAR-2010-0600.

D. How is this document organized?

    The information in this preamble is organized as follows:

I. Preamble Acronyms and Abbreviations
II. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
    C. What should I consider as I prepare my comments for EPA?
    D. How is this document organized?
III. Background
    A. What is the statutory authority for this action?
    B. How did we consider the risk results in making decisions for
this proposal?
    C. What other actions are we addressing in this proposal?
    D. What specific RTR actions have previously been taken for
these source categories?
IV. Analyses Performed
    A. How did we estimate risk posed by the source categories?
    B. How did we perform the technology review?
    C. How did we perform the analyses for the other actions being
proposed?
V. Analyses Results and Proposed Decisions
    A. What are the results and proposed decisions for the Chromium
Electroplating source categories?
    B. What are the results and proposed decisions for the Group I
Polymers and Resins Production source categories?
    C. What are the results and proposed decisions for Marine Tank
Vessel Loading Operations source category?
    D. What are the results and proposed decisions for the
Pharmaceuticals Production source category?
    E. What are the results and proposed decisions for the Printing
and Publishing Industry source category?
    F. What are the results and proposed decisions for Steel
Pickling-HCl Process

Facilities and Hydrochloric Acid Regeneration Plants source
category?
VI. Summary of Proposed Actions
    A. What actions are we proposing as a result of the technology
reviews?
    B. What actions are we proposing as a result of the residual
risk reviews?
    C. What other actions are we proposing?
VII. Request for Comments
VIII. Submitting Data Corrections
IX. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations

III. Background

A. What is the statutory authority for this action?

    Section 112 of the Clean Air Act (CAA) establishes a two-stage
regulatory process to address emissions of hazardous air pollutants
(HAP) from stationary sources. In the first stage, after EPA has
identified categories of sources emitting one or more of the HAP listed
in section 112(b) of the CAA, section 112(d) of the CAA calls for us to
promulgate NESHAP for those sources. ``Major sources'' are those that
emit or have the potential to emit any single HAP at a rate of 10 tons
per year (TPY) or more of a single HAP or 25 TPY or more of any
combination of HAP. For major sources, these technology-based standards
must reflect the maximum degree of emission reductions of HAP
achievable (after considering cost, energy requirements, and non-air
quality health and environmental impacts) and are commonly referred to
as maximum achievable control technology (MACT) standards.
    MACT standards are to reflect application of measures, processes,
methods, systems, or techniques, including, but not limited to,
measures which, (A) reduce the volume of or eliminate pollutants
through process changes, substitution of materials or other
modifications, (B) enclose systems or processes to eliminate emissions,
(C) capture or treat pollutants when released from a process, stack,
storage, or fugitive emissions point, (D) are design, equipment, work
practice, or operational standards (including requirements for operator
training or certification), or (E) are a combination of the above. CAA
section 112(d)(2)(A)-(E). The MACT standard may take the form of a
design, equipment, work practice, or operational standard where EPA
first determines either that (A) a pollutant cannot be emitted through
a conveyance designed and constructed to emit or capture the pollutant,
or that any requirement for or use of such a conveyance would be
inconsistent with law, or (B) the application of measurement
methodology to a particular class of sources is not practicable due to
technological and economic limitations. CAA sections 112(h)(1)-(2).
    The MACT ``floor'' is the minimum control level allowed for MACT
standards promulgated under CAA section 112(d)(3), and may not be based
on cost considerations. For new sources, the MACT floor cannot be less
stringent than the emission control that is achieved in practice by the
best-controlled similar source. The MACT floors for existing sources
can be less stringent than floors for new sources, but they cannot be
less stringent than the average emission limitation achieved by the
best-performing 12 percent of existing sources in the category or
subcategory (or the best-performing five sources for categories or
subcategories with fewer than 30 sources). In developing MACT
standards, we must also consider control options that are more
stringent than the floor. We may establish standards more stringent
than the floor based on the consideration of the cost of achieving the
emissions reductions, any non-air quality health and environmental
impacts, and energy requirements.
    The EPA is then required to review these technology-based standards
and to revise them ``as necessary (taking into account developments in
practices, processes, and control technologies)'' no less frequently
than every 8 years, under CAA section 112(d)(6). In conducting this
review, EPA is not obliged to completely recalculate the prior MACT
determination. NRDC v. EPA, 529 F.3d 1077, 1084 (District of Columbia
Circuit, 2008).
    The second stage in standard-setting focuses on reducing any
remaining ``residual'' risk according to CAA section 112(f). This
provision requires, first, that EPA prepare a Report to Congress
discussing (among other things) methods of calculating risk posed (or
potentially posed) by sources after implementation of the MACT
standards, the public health significance of those risks, the means and
costs of controlling them, the actual health effects to persons in
proximity of emitting sources, and the recommendations regarding
legislation of such remaining risk. EPA prepared and submitted this
report (Residual Risk Report to Congress, EPA-453/R-99-001) in March
1999. Congress did not act in response to the report, thereby
triggering EPA's obligation under CAA section 112(f)(2) to analyze and
address residual risk.
    CAA section 112(f)(2) requires us to determine for source
categories subject to certain MACT standards, whether the emissions
standards provide an ample margin of safety to protect public health.
If the MACT standards for HAP ``classified as a known, probable, or
possible human carcinogen do not reduce lifetime excess cancer risks to
the individual most exposed to emissions from a source in the category
or subcategory to less than 1-in-1 million,'' EPA must promulgate
residual risk standards for the source category (or subcategory) as
necessary to provide an ample margin of safety to protect public
health. In doing so, EPA may adopt standards equal to existing MACT
standards if EPA determines that the existing standards are
sufficiently protective. NRDC v. EPA, 529 F.3d 1077, 1083 (District of
Columbia Circuit, 2008). (``If EPA determines that the existing
technology-based standards provide an `ample margin of safety,' then
the Agency is free to readopt those standards during the residual risk
rulemaking.'') EPA must also adopt more stringent standards, if
necessary, to prevent an adverse environmental effect,\1\ but must
consider cost, energy, safety, and other relevant factors in doing so.
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    \1\ ``Adverse environmental effect'' is defined in CAA section
112(a)(7) as any significant and widespread adverse effect, which
may be reasonably anticipated to wildlife, aquatic life, or natural
resources, including adverse impacts on populations of endangered or
threatened species or significant degradation of environmental
qualities over broad areas.
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    Section 112(f)(2) of the CAA expressly preserves our use of a two-
step process for developing standards to address any residual risk and
our interpretation of ``ample margin of safety'' developed in the
National Emission Standards for Hazardous Air Pollutants: Benzene
Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants,
Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product
Recovery Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The

first step in this process is the determination of acceptable risk. The
second step provides for an ample margin of safety to protect public
health, which is the level at which the standards are set (unless a
more stringent standard is required to prevent, taking into
consideration costs, energy, safety, and other relevant factors, an
adverse environmental effect).
    The terms ``individual most exposed,'' ``acceptable level,'' and
``ample margin of safety'' are not specifically defined in the CAA.
However, CAA section 112(f)(2)(B) preserves the interpretation set out
in the Benzene NESHAP, and the United States Court of Appeals for the
District of Columbia Circuit in NRDC v. EPA, 529 F.3d 1077, concluded
that EPA's interpretation of section 112(f)(2) is a reasonable one. See
NRDC v. EPA, 529 F.3d at 1083 (District of Columbia Circuit,
``[S]ubsection 112(f)(2)(B) expressly incorporates EPA's interpretation
of the Clean Air Act from the Benzene standard, complete with a
citation to the Federal Register''). (District of Columbia Circuit
2008). See also, A Legislative History of the Clean Air Act Amendments
of 1990, volume 1, p. 877 (Senate debate on Conference Report). We
notified Congress in the Residual Risk Report to Congress that we
intended to use the Benzene NESHAP approach in making CAA section
112(f) residual risk determinations (EPA-453/R-99-001, p. ES-11).
    In the Benzene NESHAP, we stated as an overall objective:

     * * * in protecting public health with an ample margin of
safety, we strive to provide maximum feasible protection against
risks to health from hazardous air pollutants by (1) protecting the
greatest number of persons possible to an individual lifetime risk
level no higher than approximately 1-in-1 million; and (2) limiting
to no higher than approximately 1-in-10 thousand [i.e., 100-in-1
million] the estimated risk that a person living near a facility
would have if he or she were exposed to the maximum pollutant
concentrations for 70 years.

    The Agency also stated that, ``The EPA also considers incidence
(the number of persons estimated to suffer cancer or other serious
health effects as a result of exposure to a pollutant) to be an
important measure of the health risk to the exposed population.
Incidence measures the extent of health risk to the exposed population
as a whole, by providing an estimate of the occurrence of cancer or
other serious health effects in the exposed population.'' The Agency
went on to conclude that ``estimated incidence would be weighed along
with other health risk information in judging acceptability.'' As
explained more fully in our Residual Risk Report to Congress, EPA does
not define ``rigid line[s] of acceptability,'' but considers rather
broad objectives to be weighed with a series of other health measures
and factors (EPA-453/R-99-001, p. ES-11). The determination of what
represents an ``acceptable'' risk is based on a judgment of ``what
risks are acceptable in the world in which we live'' (Residual Risk
Report to Congress, p. 178, quoting the Vinyl Chloride decision at 824
F.2d 1165) recognizing that our world is not risk-free.
    In the Benzene NESHAP, we stated that ``EPA will generally presume
that if the risk to [the maximum exposed] individual is no higher than
approximately 1-in-10 thousand, that risk level is considered
acceptable.'' 54 FR 38045. We discussed the maximum individual lifetime
cancer risk as being ``the estimated risk that a person living near a
plant would have if he or she were exposed to the maximum pollutant
concentrations for 70 years.'' Id. We explained that this measure of
risk ``is an estimate of the upper bound of risk based on conservative
assumptions, such as continuous exposure for 24 hours per day for 70
years.'' Id. We acknowledge that maximum individual lifetime cancer
risk ``does not necessarily reflect the true risk, but displays a
conservative risk level which is an upper-bound that is unlikely to be
exceeded.'' Id.
    Understanding that there are both benefits and limitations to using
maximum individual lifetime cancer risk as a metric for determining
acceptability, we acknowledged in the 1989 Benzene NESHAP that
``consideration of maximum individual risk * * * must take into account
the strengths and weaknesses of this measure of risk.'' Id.
Consequently, the presumptive risk level of 100-in-1 million (1-in-10
thousand) provides a benchmark for judging the acceptability of maximum
individual lifetime cancer risk, but does not constitute a rigid line
for making that determination.
    The Agency also explained in the 1989 Benzene NESHAP the following:
``In establishing a presumption for MIR [maximum individual cancer
risk], rather than a rigid line for acceptability, the Agency intends
to weigh it with a series of other health measures and factors. These
include the overall incidence of cancer or other serious health effects
within the exposed population, the numbers of persons exposed within
each individual lifetime risk range and associated incidence within,
typically, a 50-kilometer (km) exposure radius around facilities, the
science policy assumptions and estimation uncertainties associated with
the risk measures, weight of the scientific evidence for human health
effects, other quantified or unquantified health effects, effects due
to co-location of facilities, and co-emission of pollutants.'' Id.
    In some cases, these health measures and factors taken together may
provide a more realistic description of the magnitude of risk in the
exposed population than that provided by maximum individual lifetime
cancer risk alone. As explained in the Benzene NESHAP, ``[e]ven though
the risks judged ``acceptable'' by EPA in the first step of the Vinyl
Chloride inquiry are already low, the second step of the inquiry,
determining an ``ample margin of safety,'' again includes consideration
of all of the health factors, and whether to reduce the risks even
further.'' In the ample margin of safety decision process, the Agency
again considers all of the health risks 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 costs and economic impacts of controls,
technological feasibility, uncertainties, and any other relevant
factors. Considering all of these factors, the Agency will establish
the standard at a level that provides an ample margin of safety to
protect the public health, as required by CAA section 112(f). 54 FR
38046.

B. How did we consider the risk results in making decisions for this
proposal?

    As discussed in section III.A. of this preamble, we apply a two-
step process for developing standards to address residual risk. In the
first step, EPA determines if 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) \2\ of approximately 1-in-10 thousand
[i.e., 100-in-1 million].'' 54 FR 38045. In the second step of the
process, EPA sets the standard at a level that provides an ample margin
of safety ``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.
---------------------------------------------------------------------------

    \2\ Although defined as ``maximum individual risk,'' MIR refers
only to cancer risk. MIR, one metric for assessing cancer risk, is
the estimated risk were an individual exposed to the maximum level
of a pollutant for a lifetime.
---------------------------------------------------------------------------

    In past residual risk determinations, EPA presented a number of
human health risk metrics associated with emissions from the category
under review, including: The MIR; the numbers of persons in various
risk ranges; cancer incidence; the maximum non-cancer hazard index
(HI); and the maximum acute non-cancer hazard. In estimating risks, EPA
considered source categories under review that are located near each
other and that affect the same population. EPA provided estimates of
the expected difference in actual emissions from the source category
under review and emissions allowed pursuant to the source category MACT
standard. EPA also discussed and considered risk estimation
uncertainties. EPA is providing this same type of information in
support of these actions.
    However, in contrast to past determinations, this notice presents
and considers additional measures of health information to support our
decision-making. These are discussed in more detail in later sections
of this notice, and include:
     Estimates of ``total facility'' cancer and non-cancer risk
(risk from all HAP emissions from the facility at which the source
category is located).
     Demographic analyses (analyses of the distributions of
HAP-related cancer risks and non-cancer risks, across different social,
demographic, and economic groups within the populations living near the
facilities where these source categories are located).
     Additional estimates of the risks associated with
emissions allowed by the MACT standard.
    The Agency is considering all of this available health information
to inform our determinations of risk acceptability and ample margin of
safety under CAA section 112(f). Specifically, 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 38044 and 38046, September 14, 1989. Similarly,
with regard to making the ample margin of safety determination, the
Benzene NESHAP state that ``[I]n the ample margin decision, 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 Agency acknowledges that the Benzene NESHAP provide flexibility
regarding what factors the EPA might consider in making our
determinations and how they might be weighed for each source category.
In responding to comment on our policy under the Benzene NESHAP, EPA
explained that: ``The policy chosen by the Administrator permits
consideration of multiple measures of health risk. Not only can the MIR
figure be considered, but also incidence, the presence of non-cancer
health effects, and the uncertainties of the risk estimates. In this
way, the effect on the most exposed individuals can be reviewed as well
as the impact on the general public. These factors can then be weighed
in each individual case. This approach complies with the Vinyl Chloride
mandate that the Administrator ascertain an acceptable level of risk to
the public by employing [her] 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 [her] judgment,
believes are appropriate to determining what will `protect the public
health.' '' 54 FR 38057.
    For example, the level of the MIR is only one factor to be weighed
in determining acceptability of risks. The Benzene NESHAP explain ``an
MIR of approximately 1-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 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 Benzene NESHAP state
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.
    EPA wishes to point out that certain health information has not
been considered in these decisions. In assessing risks to populations
in the vicinity of the facilities in each category, we present
estimates of risk associated with HAP emissions from the source
category alone (source category risk estimates) and HAP emissions from
the entire facilities at which the covered source categories are
located (facility-wide risk estimates). We have not presented estimates
of total HAP inhalation risks from all sources in the vicinity of the
covered sources (i.e., the sum of risks from ambient levels, emissions
from the source category, facility-wide emissions, and emissions from
other facilities nearby).
    The Agency 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. This is
particularly important when assessing non-cancer risks, where
pollutant-specific exposure levels (e.g., Reference Concentration
(RfC)) are based on the assumption that thresholds exist for adverse
health effects. For example, the Agency recognizes that, although
exposures attributable to emissions from a source category or facility
alone may not indicate the potential for increased risk of adverse non-
cancer 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 increased risk of adverse non-
cancer health effects. In May 2010, the EPA Science Advisory Board
(SAB) advised us ``* * * 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\
---------------------------------------------------------------------------

    \3\ EPA's responses to this and all other key recommendations of
the SAB's advisory on RTR risk assessment methodologies (which is
available at: http://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf)
are outlined in a memo to this rulemaking docket from David Guinnup
entitled, EPA's Actions in Response to the Key Recommendations of
the SAB Review of RTR Risk Assessment Methodologies.
---------------------------------------------------------------------------

    While we are interested in placing source category and facility-
wide HAP risks in the context of total HAP risks from all sources
combined in the vicinity of each source, we are concerned about the
uncertainties of doing so. At this point, we believe that such
estimates of total HAP risks will

have significantly greater associated uncertainties than for the source
category or facility-wide estimates, hence, compounding the uncertainty
in any such comparison. This is because we have not conducted a
detailed technical review of HAP emissions data for source categories
and facilities that have not previously undergone an RTR review or are
not currently undergoing such review. We are requesting comment on
whether and how best to estimate and evaluate total HAP exposure in our
assessments, and, in particular, on whether and how it might be
appropriate to use information from EPA's National Air Toxics
Assessment (NATA) to support such estimates. We are also seeking
comment on how best to consider various types and scales of risk
estimates when making our acceptability and ample margin of safety
determinations under CAA section 112(f). Additionally, we are seeking
recommendations for any other comparative measures that may be useful
in the assessment of the distribution of HAP risks across potentially
affected demographic groups.

C. What other actions are we addressing in this proposal?

    In this proposal, we are addressing three additional types of
action for some or all of these six MACT standards. For eight source
categories subject to three of the MACT standards, we identified
significant emission sources within the categories for which standards
were not previously developed. We are proposing MACT standards for
these emission sources pursuant to CAA section 112(d)(2) and (3). For
four source categories subject to two of the MACT standards, we are
also proposing changes to correct editorial errors, to make
clarifications, and to address issues with implementation or
determining compliance. We are also proposing to revise requirements in
each of the six MACT standards related to emissions during periods of
startup, shutdown, and malfunction (SSM).
    The United States Court of Appeals for the District of Columbia
Circuit vacated portions of two provisions in EPA's CAA section 112
regulations governing the emissions of HAP during periods of SSM.
Sierra Club v. EPA, 551 F.3d 1019 (District of Columbia Circuit, 2008),
cert. denied, 130 S. Ct. 1735 (U.S. 2010). Specifically, the Court
vacated the SSM exemption contained in 40 CFR 63.6(f)(1) and (h)(1),
that is part of a regulation, commonly referred to as the General
Provisions Rule, that EPA promulgated under section 112 of the CAA.
When incorporated into a CAA section 112(d) standard for a specific
source category, these two provisions exempt sources within that source
category from the requirement to comply with the otherwise applicable
emission standard during periods of SSM. We are proposing to eliminate
the SSM exemption in each of the six MACT standards addressed in this
proposal. Consistent with Sierra Club v. EPA, we are proposing that the
established standards in these rules apply at all times. We are also
proposing to revise the General Provisions table in each of the six
MACT standards in several respects. For example, we are removing the
General Provisions' requirement that the source develop an SSM plan. We
are also removing certain recordkeeping and reporting requirements
related to the SSM exemption, but we are retaining the recordkeeping
and related requirements for malfunctions and request public comment on
the requirements. EPA has attempted to ensure that regulatory language
relating to the SSM exemption has been removed. We solicit comment on
whether we have overlooked any regulatory provisions that might be
inappropriate, unnecessary, or redundant based on our proposal to
remove the exemption from compliance with the emission limit during
periods of SSM.
    Periods of startup, normal operations, and shutdown are all
predictable and routine aspects of a source's operations. In contrast,
malfunction is defined as a ``sudden, infrequent, and not reasonably
preventable failure of air pollution control and monitoring equipment,
process equipment or a process to operate in a normal or usual manner *
* *'' (40 CFR 63.2). EPA believes that a malfunction should not be
viewed as a distinct operating mode, and, therefore, any emissions that
occur during malfunctions do not need to be factored into development
of CAA section 112(d) standards, which, once promulgated, apply at all
times. In Mossville Environmental Action Now v. EPA, 370 F.3d 1232,
1242 (District of Columbia Circuit 2004), the Court upheld as
reasonable standards that had factored in variability of emissions
under all operating conditions. However, nothing in CAA section 112(d)
or in case law requires that EPA anticipate and account for the
innumerable types of potential malfunction events in setting emission
standards. See, Weyerhaeuser v. Costle, 590 F.2d 1011, 1058 (District
of Columbia Circuit 1978) (``In the nature of things, no general limit,
individual permit, or even any upset provision can anticipate all upset
situations. After a certain point, the transgression of regulatory
limits caused by `uncontrollable acts of third parties,' such as
strikes, sabotage, operator intoxication, or insanity, and a variety of
other eventualities, must be a matter for the administrative exercise
of case-by-case enforcement discretion, not for specification in
advance by regulation.'') Further, it is reasonable to interpret CAA
section 112(d) as not requiring EPA to account for malfunctions in
setting emissions standards. For example, we note that CAA section 112
uses the concept of ``best performing'' sources in defining MACT, the
level of stringency that major source standards must meet. Applying the
concept of ``best performing'' to a source that is malfunctioning
presents significant difficulties. The goal of best performing sources
is to operate in such a way as to avoid malfunctions of their units.
    Moreover, even if malfunctions were considered a distinct operating
mode, we believe it would be impracticable to take malfunctions into
account in setting CAA section 112(d) standards. As noted above, by
definition, malfunctions are sudden and unexpected events, and it would
be difficult to set a standard that takes into account the myriad
different types of malfunctions that can occur across all sources in
each source category. Malfunctions can also vary in frequency, degree,
and duration, further complicating standard setting.
    Under this proposal, in the event that a source fails to comply
with the applicable CAA section 112(d) standards as a result of a
malfunction event, EPA would determine an appropriate response based
on, among other things, the good faith efforts of the source to
minimize emissions during malfunction periods, including preventative
and corrective actions, as well as root cause analyses to ascertain and
rectify excess emissions. EPA would also consider whether the source's
failure to comply with the CAA section 112(d) standard was, in fact,
``sudden, infrequent, not reasonably preventable'' and was not instead
``caused in part by poor maintenance or careless operation.'' 40 CRF
63.2 (definition of malfunction).
    Finally, EPA recognizes that, even equipment that is properly
designed and maintained can sometimes fail, and that such failure can
sometimes cause or contribute to an exceedance of the relevant emission
standard. (See, e.g., State Implementation Plans: Policy Regarding
Excessive Emissions During Malfunctions, Startup, and Shutdown
(September 20, 1999); Policy on Excess

Emissions During Startup, Shutdown, Maintenance, and Malfunctions
(February 15, 1983)). Therefore, consistent with our recently
promulgated final amendments to regulations addressing the Portland
Cement category (75 FR 54970, September 9, 2010), we are proposing to
add regulatory language providing an affirmative defense against civil
penalties for exceedances of emission limits that are caused by
malfunctions in each of the six MACT standards addressed in this
proposal. We are proposing to define ``affirmative defense'' to mean,
in the context of an enforcement proceeding, a response or defense put
forward by a defendant, regarding which the defendant has the burden of
proof, and the merits of which are independently and objectively
evaluated in a judicial or administrative proceeding. We are also
proposing regulatory provisions to specify the elements that are
necessary to establish this affirmative defense. (See 40 CFR 22.24).
The proposed criteria would ensure that the affirmative defense is
available only where the event that causes an exceedance of the
emission limit meets the narrow definition of malfunction in 40 CFR
63.2 (sudden, infrequent, not reasonably preventable, and not caused by
poor maintenance and/or careless operation). The proposed criteria also
are designed to ensure that steps are taken to correct the malfunction,
to minimize emissions, and to prevent future malfunctions. In any
judicial or administrative proceeding, the Administrator would be able
to challenge the assertion of the affirmative defense and, if the
respondent has not met its burden of proving all of the requirements in
the affirmative defense, appropriate penalties could be assessed in
accordance with section 113 of the CAA (see also 40 CFR 22.77).

D. What specific RTR actions have previously been taken for these
source categories?

    For some of the 16 source categories covered by these six MACT
standards, we have previously taken certain actions under the RTR
program. Following is a summary of these previous actions and also a
summary of additional reviews we have subsequently conducted for each
source category.
1. Categories for Which RTR Decisions Have Been Finalized
    There are nine source categories regulated under the Group I
Polymers and Resins MACT standard. For four of these source categories
(Butyl Rubber Production, Ethylene Propylene Rubber Production,
Neoprene Production, and Polysulfide Rubber Production), we previously
proposed and promulgated a decision not to revise the standards for
purposes of the RTR provisions in CAA sections 112(d)(6) and (f)(2).\4\
See 72 FR 70543, December 12, 2007 (proposed rule), and 73 FR 76220,
December 16, 2008 (final rule). These four categories were determined
to be ``low-risk,'' as the maximum lifetime individual cancer risks
were less than 1-in-1-million, and there were no other health concerns
of significance. Therefore, we determined that conducting additional
risk analyses for these categories was not warranted. We are not re-
opening the RTR in this notice for these four source categories, and do
not seek additional comments on that prior RTR.
---------------------------------------------------------------------------

    \4\ There are no longer any operating facilities in the United
States that produce polysulfide rubber, and we do not anticipate any
will begin to operate in the future.
---------------------------------------------------------------------------

    However, for three of these four Group I Polymers and Resins source
categories (Butyl Rubber Production, Ethylene Propylene Rubber
Production, and Neoprene Production), we have identified significant
emission sources for which MACT standards were not previously
developed. In this proposal, we are proposing MACT standards for these
emission sources, and we are also proposing that the residual risks
after implementation of these new MACT standards will not change our
previous finding that these source categories present low risks and
that our obligation to review the residual risk under CAA section
112(f) has also been satisfied.
2. Categories for Which RTR Decisions Have Been Proposed, but Not
Promulgated
    For eight source categories covered under four of the MACT
standards addressed in this proposal, we previously performed an RTR
review and proposed that no revisions of the MACT standards were
necessary to address residual risk and that it was not necessary to
revise the existing standards under CAA section 112(d)(6). See 73 FR
60423, October 10, 2008. The MACT standards addressed in this proposal
included Marine Tank Vessel Loading Operations (MTVLO), Printing and
Publishing Industry, Pharmaceuticals Production, and five of the source
categories covered under Group I Polymers and Resins (Epichlorohydrin
Elastomers, Hypalon\TM\ Production, Nitrile Butadiene Rubber
Production, Polybutadiene Rubber Production, and Styrene Butadiene
Rubber and Latex Production).\5\ Comments were received on that
proposal, but no final action has been taken. This proposal presents
additional analyses we have performed since the proposal, for each of
these source categories with regard to the RTR. In addition, we are
proposing revisions to the SSM provisions in the existing standards for
these source categories, and, for several of the source categories, we
are proposing MACT standards under CAA sections 112(d)(2) and (3) for
emission points that were not previously regulated.
---------------------------------------------------------------------------

    \5\ The Mineral Wool Production source category was also
addressed in that same October 2008 proposal. We are not proposing
any additional action for that source category in this proposal, but
will do so in a separate future action. We note that there are no
longer any operating facilities in the United States that produce
Hypalon\TM\, and we do not anticipate that any will begin operation
in the future.
---------------------------------------------------------------------------

3. Categories for Which RTR Decisions Have Not Been Proposed
    We have not previously proposed any RTR actions for the four source
categories (Hard and Decorative Chromium Electroplating, Chromium
Anodizing Tanks, and Steel Pickling--HCl Process Facilities and
Hydrochloric Acid Regeneration Plants) covered by the Chromium
Electroplating and Steel Pickling MACT standards. Therefore, this is
our initial proposed action for these two MACT standards to address the
RTR requirement. In addition, we identified significant advances in the
housekeeping requirements in the chromium source categories for which
we are proposing MACT standards. We are also proposing revisions to the
provisions addressing SSM to ensure they are consistent with the Court
decision in Sierra Club v. EPA, 551 F.3d 1019, and we are proposing
changes to correct editorial errors, make clarifications, or address
issues with implementation or determining compliance.

IV. Analyses Performed

    As discussed above, in this notice, we are taking the following
actions: (1) We are newly proposing action or supplementing our
previous proposal to address the RTR requirements of CAA sections
112(d)(6) and (f)(2) for 16 source categories covered by six different
MACT standards; (2) for eight of the source categories, we are
proposing MACT standards for significant emission sources that are not
currently subject to emission standards under the MACT standards; (3)
we are proposing to revise the provisions in each of these six MACT
standards to address SSM to ensure that the SSM provisions are
consistent with the Court

decision in Sierra Club v. EPA, 551 F. 3d 1019; and (4) for two of the
MACT standards, we are proposing amendments to correct editorial
errors, to make clarifications, and to address issues with
implementation or determining compliance.

A. How did we estimate risk posed by the source categories?

    To support the proposed decision under the RTR for each source
category, EPA conducted risk assessments that provided estimates of the
MIR posed by the HAP emissions from each source in a category and by
each source category, the distribution of cancer risks within the
exposed populations, cancer incidence, HI for chronic exposures to HAP
with non-cancer health effects, hazard quotients (HQ) for acute
exposures to HAP with non-cancer health effects, and an evaluation of
the potential for adverse environmental effects. The risk assessments
consisted of seven primary steps, as discussed below.
    The docket for this rulemaking contains the following documents
which provide more information on the risk assessment inputs and
models, Draft Residual Risk Assessment for 9 Source Categories, Draft
Residual Risk Assessment for Steel Pickling, and Draft Residual Risk
Assessment for Chromium Electroplating, as well as the memoranda for
the Printing and Publishing Industry, MTVLO, Epichlorohydrin Elastomers
Production, Polybutadiene Rubber Production, Styrene Butadiene Rubber
Production, Nitrile Butadiene Production, and Pharmaceuticals
Production source categories.
1. Establishing the Nature and Magnitude of Actual Emissions and
Identifying the Emissions Release Characteristics
    For the source categories included in the October 10, 2008,
proposal, we compiled preliminary data sets using readily-available
information, reviewed the data, and made changes where necessary, and
shared these data with the public via an Advanced Notice of Proposed
Rulemaking (ANPRM). 72 FR 29287, March 29, 2007. The data sets were
then updated based on comments received on the ANPRM and, in some
cases, with additional information gathered by EPA. For the five Group
I Polymers and Resins I Production source categories included in the
October 2008 proposal (Epichlorohydrin Elastomers Production,
Hypalon\TM\ Production, Nitrile Butadiene Rubber Production,
Polybutadiene Rubber Production, and Styrene Butadiene Rubber and Latex
Production), the preliminary data sets were based on information we
collected directly from industry on emissions data and emissions
release characteristics. For the MTVLO, Pharmaceuticals Production, and
the Printing and Publishing Industry source categories, we created the
preliminary data sets using data in the 2002 National Emissions
Inventory (NEI) Final Inventory, Version 1 (made publicly available on
February 26, 2006), supplemented by data collected directly from
industry when available. The NEI is a database that contains
information about sources that emit criteria air pollutants and 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.
    In the March 29, 2007, ANPRM, we specifically requested comment on,
and updates to, these preliminary data sets. We received comments on
emissions data and emissions release characteristics data for
facilities in these source categories. These comments were reviewed,
considered, and the emissions information was adjusted where we
concluded the comments supported such adjustment. After incorporation
of changes to the data sets from this public data review process, data
sets were created that were used to conduct the risk assessments and
other analyses that formed the basis for the proposed actions included
in the October 10, 2008, proposal.
    Since the proposal, we have continued to scrutinize the data sets
for these source categories and to review additional data that has
become available since the October 10, 2008, proposal. For the Printing
and Publishing Industry source category, we became aware that some
facilities had closed. We also reviewed the emissions data and had
questions about the emissions of certain HAP. After contact with
industry, it was determined that those emissions did not occur from
those facilities. We updated the Printing and Publishing Industry data
set to reflect these changes in operating facilities and emissions. For
the MTVLO data set, we had concerns that several emission points in our
existing data set were mislabeled, and, thus, we extracted more recent
data from the NEI. For this source category, the data set is based on
the 2005 NEI. For the Pharmaceuticals Production source category data
set, no changes are necessary to the data set used for the proposal.
For the Polymers and Resins I MACT standard source categories included
in the October 10, 2008, proposal, updates have been made based on
information received in response to an industry information collection
survey. Documentation for industry contacts, surveys, and other
information gathered to support these changes is available in the
docket for this action.
    For the four source categories not included in the December 10,
2008, proposal, we compiled preliminary data sets using the best
available information, reviewed the data, and made changes where
necessary. For the three Chromium Electroplating MACT standard source
categories (Chromium Anodizing Tanks, Decorative Chromium
Electroplating, and Hard Chromium Electroplating) and the Steel
Pickling source category, we compiled the preliminary data sets using
data in the 2005 NEI. Then, for the Steel Pickling source category,
seven facilities were contacted to verify their emissions and emissions
release characteristic data, and we updated the data set based on the
information collected. This updated data set was used to conduct the
risk assessments and other analyses that form the bases for the
proposed actions.
    For the Chromium Electroplating source categories, a review of the
2005 NEI data indicated that not all chromium electroplating facilities
were included in the data set. To develop an emissions inventory for
the entire industry that could be used for modeling, an additional data
set was developed based on facilities with known addresses--a total of
1,629 facilities compared to 122 facilities in the NEI. Emissions for
each type of plant were estimated based on the model plants developed
for the original Chromium Electroplating MACT standard,\6\ with hard
chromium model plants having the highest emissions, followed by
decorative chromium electroplating, and then chromium anodizing. If the
type of electroplating performed at a specific plant was unknown, we
assumed these facilities were hard chrome electroplating when we
estimated emissions and risks for those facilities. Although we knew
that, by doing so, we would be overestimating emissions of chromium,
and, therefore, also of risk, we made this conservative assumption
because we did not have complete information, and we chose to
overestimate to preserve an

ample margin of safety in the risk assessment upon which our risk
modeling would be based. This analysis and a supplemental assessment
are fully described in section V.A.
---------------------------------------------------------------------------

    \6\ See EPA-HQ-OAR-2010-0600, Model Plant Data Used to Estimate
Risk from Chromium Electroplating Sources.
---------------------------------------------------------------------------

2. Establishing the Relationship Between Actual Emissions and MACT-
Allowable Emissions Levels
    The available emissions data in the NEI and from other sources
typically represent the mass of emissions actually emitted during the
specified annual time period. These ``actual'' emission levels are
often lower than the level of emissions that a facility might be
allowed to emit and still comply with the MACT standard. The emissions
level allowed to be emitted by the MACT standard is referred to as the
``MACT-allowable'' emissions level. This represents the highest
emission level that could be emitted by the facility without violating
the MACT standard.
    We discussed the use of both MACT-allowable and actual emissions in
the final Coke Oven Batteries residual risk rule (70 FR 19998-19999,
April 15, 2005) and in the proposed and final Hazardous Organic NESHAP
(HON) residual risk rules (71 FR 34428, June 14, 2006, and 71 FR 76609,
December 21, 2006, respectively). In those previous actions, we noted
that assessing the risks at the MACT-allowable level is inherently
reasonable since these risks reflect the maximum level sources could
emit and still comply with national emission standards. But 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. (54 FR 38044, September 14, 1989.)
It is reasonable to consider actual emissions because sources typically
seek to perform better than required by emission standards to provide
an operational cushion to accommodate the variability in manufacturing
processes and control device performance.
    As described above, the actual emissions data were compiled based
on the NEI, information gathered from facilities and States, and
information received in response to the ANPRM for several of the source
categories. To estimate emissions at the MACT-allowable level, we
developed a ratio of MACT-allowable to actual emissions for each
emissions source type in each source category, based on the level of
control required by the MACT standard compared to the level of reported
actual emissions and available information on the level of control
achieved by the emissions controls in use. For example, if there was
information to suggest several facilities in a source category were
controlling storage tank emissions by 98 percent while the MACT
standards required only 92-percent control, we would estimate that
MACT-allowable emissions from these emission points could be as much as
four times higher (8-percent allowable emissions compared with 2-
percent actually emitted), and the ratio of MACT-allowable to actual
would be 4:1 for this emission point type at the facilities in this
source category. After developing these ratios for each emission point
type in each source category, we next applied these ratios on a
facility-by-facility basis to the maximum chronic risk values from the
inhalation risk assessment to obtain facility-specific maximum risk
values based on MACT-allowable emissions.
3. Conducting Dispersion Modeling, Determining Inhalation Exposures,
and Estimating Individual and Population Inhalation Risks
    Both long-term and short-term inhalation exposure concentrations
and health risks from each of the source categories addressed in this
proposal were estimated using the Human Exposure Model (Community and
Sector HEM-3 version 1.1.0). The HEM-3 performs three of the primary
risk assessment activities listed above: (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 km of the modeled sources, and (3) estimating
individual and population-level inhalation risks using the exposure
estimates and quantitative dose-response information.
    The dispersion model used by HEM-3 is AERMOD, which is one of EPA's
preferred models for assessing pollutant concentrations from industrial
facilities.\7\ 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 of hourly surface and upper
air observations for 130 meteorological stations, selected to provide
coverage of the United States and Puerto Rico. A second library of
United States Census Bureau census block \8\ internal point locations
and populations provides the basis of human exposure calculations
(Census, 2000). In addition, the census library includes the elevation
and controlling hill height for each census block, which are also used
in dispersion calculations. A third library of pollutant unit risk
factors and other health benchmarks is used to estimate health risks.
These risk factors and health benchmarks are the latest values
recommended by EPA for HAP and other toxic air pollutants. These values
are available at http://www.epa.gov/ttn/atw/toxsource/summary.html and
are discussed in more detail later in this section.
---------------------------------------------------------------------------

    \7\ 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).
    \8\ A census block is generally the smallest geographic area for
which census statistics are tabulated.
---------------------------------------------------------------------------

    In developing the risk assessment for chronic exposures, we used
the estimated annual average ambient air concentration of each of the
HAP emitted by each source for which we have emissions data in the
source category. The air concentrations at each nearby census block
centroid were used as a surrogate for the chronic inhalation exposure
concentration for all the people who reside in that census block. We
calculated the MIR for each facility as the cancer risk associated with
a lifetime (70-year period) of exposure to the maximum concentration at
the centroid of an inhabited census block. Individual cancer risks were
calculated as the lifetime exposure to the ambient concentration of
each of the HAP multiplied by its Unit Risk Estimate (URE), which is an
upper bound estimate of an individual's probability 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 URE values from EPA's Integrated Risk Information System
(IRIS).\9\ For carcinogenic pollutants without EPA IRIS values, we look
to other reputable sources of cancer dose-response values, often using
California Environmental Protection Agency (CalEPA) URE values, 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 EPA,
we may use such dose-response values in place of, or in addition to,
other values.
---------------------------------------------------------------------------

    \9\ The IRIS information is available at http://www.epa.gov/
IRIS.

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    We note here that several carcinogens have a mutagenic mode of
action.\10\ For these compounds, the age-dependent adjustment factors
described in EPA's Supplemental Guidance for Assessing Susceptibility
from Early-Life Exposure to Carcinogens \11\ were applied. This
adjustment has the effect of increasing the estimated lifetime risks
for these pollutants by a factor of 1.6.\12\ In addition, although only
a small fraction of the total polycyclic organic matter (POM) emissions
were reported as individual compounds, EPA expresses carcinogenic
potency for compounds in this group in terms of benzo[a]pyrene
equivalence, based on evidence that carcinogenic POM have the same
mutagenic mechanism of action as does benzo[a]pyrene. For this reason,
EPA's Science Policy Council \13\ recommends applying the Supplemental
Guidance to all carcinogenic polycyclic aromatic hydrocarbons for which
risk estimates are based on relative potency. Accordingly, we have
applied the Supplemental Guidance to all unspeciated POM mixtures.
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    \10\ U.S. EPA, 2006. Performing risk assessments that include
carcinogens described in the Supplemental Guidance as having a
mutagenic mode of action. Science Policy Council Cancer Guidelines
Implementation Workgroup Communication II: Memo from W.H. Farland
dated June 14, 2006. http://epa.gov/osa/spc/pdfs/
CGIWGCommunication_II.pdf.
    \11\ U.S. EPA, 2005. Supplemental Guidance for Assessing Early-
Life Exposure to Carcinogens. EPA/630/R-03/003F. http://www.epa.gov/
ttn/atw/childrens_supplement_final.pdf.
    \12\ Only one of these mutagenic compounds, benzo[a]pyrene, is
emitted by any of the sources covered by this proposal.
    \13\ U.S. EPA, 2005. Science Policy Council Cancer Guidelines
Implementation Workgroup Communication I: Memo from W.H. Farland
dated October 4, 2005, to Science Policy Council. http://
www.epa.gov/osa/spc/pdfs/canguid1.pdf.
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    Incremental individual lifetime cancer risks associated with
emissions from the source category were estimated as the sum of the
risks for each of the carcinogenic HAP (including those classified as
carcinogenic to humans, likely to be carcinogenic to humans, and
suggestive evidence of carcinogenic potential \14\) emitted by the
modeled source. Cancer incidence and the distribution of individual
cancer risks for the population within 50 km of any source were also
estimated for the source category as part of these assessments by
summing individual risks. A distance of 50 km is consistent with both
the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the
limitations of Gaussian dispersion modeling.
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    \14\ These classifications also coincide with the terms ``known
carcinogen, probable carcinogen, and possible carcinogen,''
respectively, which are the terms advocated in the EPA's previous
Guidelines for Carcinogen Risk Assessment, published in 1986 (51 FR
33992, September 24, 1986). Summing the risks of these individual
compounds to obtain the cumulative cancer risks is an approach that
was recommended by the EPA's SAB in their 2002 peer review of EPA's
NATA entitled, NATA--Evaluating the National-scale Air Toxics
Assessment 1996 Data--an SAB Advisory, available at: http://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
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    To assess risk of non-cancer health effects from chronic exposures,
we summed the HQ for each of the HAP that affects a common target organ
system to obtain the HI for that target organ system (or target organ-
specific HI, TOSHI). The HQ is the estimated exposure divided by the
chronic reference level, which is either the U.S. 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,'' or, in cases where an RfC
is not available, the CalEPA Chronic Reference Exposure Level (REL),
defined as ``the concentration level at or below which no adverse
health effects are anticipated for a specified exposure duration.'' As
noted above, 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 EPA,
we may use those dose-response values in place of, or in addition to,
other values.
    Screening estimates of acute exposures and risks were also
evaluated for each of the HAP at the point of highest off-site exposure
for each facility (i.e., not just the census block centroids) assuming
that a person is located at this spot at a time when both the peak
(hourly) emission rate and hourly dispersion conditions (1991 calendar
year data) occur. In each case, acute HQ values were calculated using
best available, short-term health threshold values. These acute
threshold values include REL, Acute Exposure Guideline Levels (AEGL),
and Emergency Response Planning Guidelines (ERPG) for 1-hour exposure
durations. As discussed below, we used conservative assumptions for
emission rates, meteorology, and exposure location for our acute
analysis.
    As described in the CalEPA's Air Toxics Hot Spots Program Risk
Assessment Guidelines, Part I, The Determination of Acute Reference
Exposure Levels for Airborne Toxicants, an acute REL value (http://
www.oehha.ca.gov/air/pdf/acuterel.pdf) is defined as ``the
concentration level at or below which no adverse health effects are
anticipated for a specified exposure duration is termed the REL. REL
values are based on the most sensitive, relevant, adverse health effect
reported in the medical and toxicological literature. REL values are
designed to protect the most sensitive individuals in the population by
the inclusion of margins of safety. Since margins of safety are
incorporated to address data gaps and uncertainties, exceeding the REL
value does not automatically indicate an adverse health impact.''
    AEGL values were derived in response to recommendations from the
National Research Council (NRC). As described in ``Standing Operating
Procedures (SOP) of the National Advisory Committee on Acute Exposure
Guideline Levels for Hazardous Substances'' (http://www.epa.gov/
opptintr/aegl/pubs/sop.pdf),\15\ ``the NRC's previous name for acute
exposure levels--community emergency exposure levels (CEEL)-- was
replaced by the term AEGL to reflect the broad application of these
values to planning, response, and prevention in the community, the
workplace, transportation, the military, and the remediation of
Superfund sites.'' This document also states that AEGL values
``represent threshold exposure limits for the general public and are
applicable to emergency exposures ranging from 10 minutes to 8 hours.''
The document lays out the purpose and objectives of AEGL by stating
(page 21) that ``the primary purpose of the AEGL program and the NAC/
AEGL Committee is to develop guideline levels for once-in-a-lifetime,
short-term exposures to airborne concentrations of acutely toxic, high-
priority chemicals.'' In detailing the intended application of AEGL
values, the document states (page 31) that ''[i]t is anticipated that
the AEGL values will be used for regulatory and nonregulatory purposes
by United States Federal and State agencies, and possibly the
international community in conjunction with chemical emergency
response, planning, and prevention programs. More specifically, the
AEGL values will be used for conducting various risk assessments to aid
in the development of emergency preparedness and prevention plans, as
well as real-time emergency response actions, for accidental chemical
releases at fixed facilities and from transport carriers.''
---------------------------------------------------------------------------

    \15\ NAS, 2001. Standing Operating Procedures for Developing
Acute Exposure Levels for Hazardous Chemicals, page 2.

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

    The AEGL-1 value is then specifically defined as ``the airborne
concentration 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 (page
3) 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.'' Similarly, the document defines
AEGL-2 values as ``the airborne concentration (expressed as ppm or mg/
m\3\) 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.''
    ERPG values are derived for use in emergency response, as described
in the American Industrial Hygiene Association's document entitled,
Emergency Response Planning Guidelines (ERPG) Procedures and
Responsibilities (http://www.aiha.org/1documents/committees/
ERPSOPs2006.pdf), which states that, ``Emergency Response Planning
Guidelines were developed for emergency planning and are intended as
health-based guideline concentrations for single exposures to
chemicals.'' \16\ The ERPG-1 value 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.'' Similarly, the ERPG-2 value 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 or developing irreversible or other serious health effects
or symptoms which could impair an individual's ability to take
protective action.''
---------------------------------------------------------------------------

    \16\ ERP Committee Procedures and Responsibilities. 1 November
2006. American Industrial Hygiene Association.
---------------------------------------------------------------------------

    As can be seen from the definitions above, the AEGL and ERPG values
include the similarly-defined severity levels 1 and 2. For many
chemicals, a severity level 1 value AEGL or ERPG has not been
developed; in these instances, higher severity level AEGL-2 or ERPG-2
values are compared to our modeled exposure levels to screen for
potential acute concerns.
    Acute REL values for 1-hour exposure durations are typically lower
than their corresponding AEGL-1 and ERPG-1 values. Even though their
definitions are slightly different, AEGL-1 values are often the same as
the corresponding ERPG-1 values, and AEGL-2 values are often equal to
ERPG-2 values. Maximum HQ values from our acute screening risk
assessments typically result when basing them on the acute REL value
for a particular pollutant. In cases where our maximum acute HQ value
exceeds 1, we also report the HQ value based on the next highest acute
threshold (usually the AEGL-1 and/or the ERPG-1 value).
    To develop screening estimates of acute exposures, we developed
estimates of maximum hourly emission rates by multiplying the average
actual annual hourly emission rates by a factor to cover routinely
variable emissions. We chose the factor to use based on process
knowledge and engineering judgment and with awareness of a Texas study
of short-term emissions variability, which showed that most peak
emission events, in a heavily-industrialized 4-county area (Harris,
Galveston, Chambers, and Brazoria Counties, Texas), were less than
twice the annual average hourly emission rate, and the highest peak
emission event was 8.5 times the annual average hourly emission
rate.\17\ This analysis is provided in Appendix 4 of the Draft Residual
Risk Assessment for Source Categories Report and is available in the
docket for this action. Considering this analysis, unless specific
process knowledge provided an alternate value, a conservative screening
multiplication factor of 10 was applied to the average annual hourly
emission rate in these acute exposure screening assessments.
---------------------------------------------------------------------------

    \17\ See http://www.tceq.state.tx.us/compliance/field_ops/eer/
index.html or docket to access the source of these data.
---------------------------------------------------------------------------

    In cases where all acute HQ values from the screening step were
less than or equal to 1, acute impacts were deemed negligible and no
further analysis was performed. In the cases where an acute HQ from the
screening step was greater than 1, additional site-specific data were
considered to develop a more refined estimate of the potential for
acute impacts of concern. The data refinements considered included
using a peak-to-mean hourly emissions ratio based on source category-
specific knowledge or data (rather than the default factor of 10) and
using the site-specific facility layout to distinguish facility
property from an area where the public could be exposed. Ideally, we
would prefer to have continuous measurements over time to see how the
emissions vary by each hour over an entire year. Having a frequency
distribution of hourly emission rates over a year would allow us to
perform a probabilistic analysis to estimate potential threshold
exceedances and their frequency of occurrence. Such an evaluation could
include a more complete statistical treatment of the key parameters and
elements adopted in this screening analysis. However, we recognize that
having this level of data is rare, hence our use of the multiplier
approach.
4. Conducting Multipathway Exposure and Risk Modeling
    The potential for significant human health risks due to exposures
via routes other than inhalation (i.e., multipathway exposures) and the
potential for adverse environmental impacts were evaluated in a three-
step process. In the first step, we determined whether any facilities
emitted any HAP known to be persistent and bio-accumulative in the
environment (PB-HAP). There are 14 PB-HAP compounds or compound classes
identified for this screening in EPA's Air Toxics Risk Assessment
Library (available at http://www.epa.gov/ttn/fera/risk_atra_
vol1.html). They are cadmium compounds, chlordane, chlorinated
dibenzodioxins and furans, dichlorodiphenyldichloroethylene,
heptachlor, hexachlorobenzene, hexachlorocyclohexane, lead compounds,
mercury compounds, methoxychlor, polychlorinated biphenyls, POM,
toxaphene, and trifluralin.
    In the second step of the screening process, we determined whether
the facility-specific emission rates of each of the emitted PB-HAP were
large enough to create the potential for significant non-inhalation
risks. To facilitate this step, we have developed emission rate
thresholds for each PB-HAP using a hypothetical screening exposure
scenario developed for use in conjunction with the TRIM.FaTE model. The
hypothetical screening scenario was subjected to a sensitivity analysis
to ensure that its key design parameters were established such that
environmental media concentrations were not underestimated (i.e., to
minimize the occurrence of false negatives, or results that suggest
that risks might be acceptable when, in fact, actual risks are high),
and to also minimize the occurrence of false positives for human health
endpoints.

We call this application of the TRIM.FaTE model TRIM-Screen. The
facility-specific emission rates of each of the PB-HAP in each source
category were compared to the emission threshold values for each of the
PB-HAP identified in the source category data sets.
    For all of the facilities in the source categories addressed in
this proposal, all of the PB-HAP emission rates were less than the
emission threshold values. As a result of this, multi-pathway exposures
and environmental risks were deemed negligible and no further analysis
was performed. If the emission rates of the PB-HAP had been above the
emission threshold values, the source categories would have been
further evaluated for potential non-inhalation risks and adverse
environmental effects in a third step through site-specific refined
assessments using EPA's TRIM.FaTE model.
    For further information on the multi-pathway analysis approach, see
the residual risk documentation as referenced in section IV.A of this
preamble.
5. Assessing Risks Considering Emissions Control Options
    In addition to assessing baseline inhalation risks and screening
for potential multi-pathway risks, for some source categories, where
appropriate, we also estimated risks considering the potential emission
reductions that would be achieved by the particular control options
under consideration. The inhalation and multi-pathway risks estimated,
as described above, at the actual and MACT-allowable levels represent
the actual and maximum allowable operating conditions of the facilities
in the source categories analyzed. For source categories where emission
reduction options were available, we estimated risk based on the
expected emissions reductions that would be realized with those
additional emissions controls. In these cases, the expected emissions
reductions were applied to the specific HAP and emissions sources in
the source category data set. The results of the risk analyses
considering the application of emissions controls are included in the
residual risk documentation as referenced in section IV.A of this
preamble, which is available in the docket for this action.
6. Conducting Other Risk-Related Analyses, Including Facility-Wide
Assessments and Demographic Analyses
a. Facility-Wide Risk
    To put the source category risks in context, we also examined 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, for each facility that includes one or more
sources from one of the source categories under review, we examined the
HAP emissions not only from the source category of interest, but also
emissions of HAP from all other emission sources at the facility. The
emissions data for generating these ``facility-wide'' risks were
obtained from the 2005 NEI (available at http://www.epa.gov/chief/net/
2005inventory.html). We analyzed 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 facility-wide risks
that could be attributed to each of the six source categories being
addressed in this proposal, we 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 risk documentation available through the docket for this
action provides all the facility-wide risks and the percentage of
source category contribution for all source categories assessed.
    The methodology and the results of the facility-wide analyses for
each source category are included in the residual risk documentation as
referenced in section IV.A of this preamble, which is available in the
docket for this action.
b. Demographic Analysis
    To examine the potential for any environmental justice issues that
might be associated with each source category, we evaluated the
distributions of HAP-related cancer and non-cancer risks across
different social, demographic, and economic groups within the
populations living near the facilities where these source categories
are located. The development of demographic analyses to inform the
consideration of environmental justice issues in EPA rulemakings is an
evolving science. The EPA offers the demographic analyses in this
rulemaking as examples of how such analyses might be developed to
inform such consideration, and invites public comment on the approaches
used and the interpretations made from the results, with the hope that
this will support the refinement and improve utility of such analyses
for future rulemakings.
    For this analysis, we analyzed risks due to the inhalation of HAP
in two separate ways. In the first approach, we focus the analysis on
the total populations residing within 5 km of each facility (source
category and facility-wide), regardless of their estimated risks, and
examine the distributions of estimated risk across the various
demographic groups within those 5 km circles. The distance of 5 km was
chosen for the first approach to be consistent with previous
demographic analyses performed at EPA, such as the one which was
performed in support of the recent proposal for the Boilers NESHAP. In
the second approach, we focus the analysis only on the populations
within 5 km \18\ of any facility estimated to have exposures to HAP
which result in cancer risks of 1-in-1 million or greater or non-cancer
hazard indices of 1 or greater (based on the emissions of the source
category or the facility, respectively). Once again, we examine the
distributions of those risks across various demographic groups. In each
approach, we compare the percentages of particular demographic groups
to the total number of people in those demographic groups nationwide.
In this preamble, we only present the results of the second approach
since it focuses on the significant risks from either the source
category or the facility-wide emissions. The results of both approaches
including other risk metrics such as average risks for the exposed
populations are documented in source category-specific technical
reports in the docket for each of the source categories covered in this
proposal.\19\
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    \18\ Generally, we have found that using a 5 km radius in the
analysis will capture more than 90 percent of all the individuals
with cancer risks above 1-in-1 million. In the future, we plan to
extend these analyses to cover the entire modeled domain for a
facility (50 km radius) to capture all individuals with risks above
1-in-1 million from the affected facilities.
    \19\ For example, the report pertaining to the Hard Chromium
Electroplating source category is entitled Risk and Technology
Review--Analysis of Socio-Economic Factors for Populations Living
Near Hard Chromium Electroplating Facilities.
---------------------------------------------------------------------------

    The basis for the risk values used in these analyses were the
modeling results obtained from the HEM-3 model described above. The
risk values for each census block were linked to a database of
information from the 2000 Decennial census that includes data on race
and ethnicity, age distributions, poverty status, household incomes,
and education level. The Census Department Landview [supreg] database
was the source of the data on race and ethnicity, and the

data on age distributions, poverty status, household incomes, and
education level was obtained from the 2000 Census of Population and
Housing Summary File 3 (SF3) Long Form. While race and ethnicity census
data are available at the block group level, the age and income census
data are only available at the census block level (which includes an
average of 26 blocks or an average of 1,350 people). Where census data
are available at the block group level but not the block level, we
assumed that all blocks within the block group have the same
distribution of ages and incomes as the block group.
    For each source category, the analysis results include the
distribution of estimated lifetime inhalation cancer and chronic non-
cancer risks for different racial and ethnic groups, different age
groups, adults with and without a high school diploma, people living in
households below the national median income, and for people living
below the poverty line among the population living near these
facilities. The specific census population categories studied include:
     Total population.
     White.
     African American (or Black).
     Native Americans.
     Other races and multiracial.
     Hispanic or Latino.
     Children 18 years of age and under.
     Adults 19 to 64 years of age.
     Adults 65 years of age and over.
     Adults without a high school diploma.
     Households earning under the national median income.
     People living below the poverty line.
    It should be noted that these categories overlap in some instances,
resulting in some populations being counted in more than one category
(e.g., other races and multiracial and Hispanic). In addition, while
not a specific census population category, we also examined risks to
the category ``Minorities,'' which is defined as all race population
categories except white. Since these demographic analysis methods are
still evolving, EPA specifically solicits comment on the inclusion of
other demographic categories (e.g., ``Hispanic and Non-white'') in our
future analyses.
    For further information about risks to the populations local to the
facilities in these source categories, we also evaluated the estimated
distribution of inhalation cancer and chronic non-cancer risks
associated with the HAP emissions from all the emissions sources at the
facility (i.e., facility-wide). This analysis used the facility-wide
RTR modeling results and the census data described above.
    The methodology and the results of the demographic analyses for
each source category are included in the residual risk documentation as
referenced in section IV.A of this preamble, which is available in the
docket for this action.
7. Considering Uncertainties in Risk Assessment
    Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for the source categories
addressed in this proposal. Although uncertainty exists, we believe the
approach that we took, which used conservative tools and assumptions,
ensures that our decisions are health-protective. A brief discussion of
the uncertainties in the emissions data sets, dispersion modeling,
inhalation exposure estimates, and dose-response relationships follows
below. A more thorough discussion of these uncertainties is included in
the Draft Residual Risk Assessment for the Steel Pickling Source
Category (July 2010), Draft Residual Risk Assessment for the Chromium
Electroplating Source Category (July 2010), Draft Residual Risk
Assessment for 9 Source Categories (August 2008), and the Risk and
Technology Review (RTR) Assessment Plan (November 2006), each of which
are available in the docket for this action.
a. Uncertainties in the Emissions Data Sets
    Although the development of the RTR data sets 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
is incomplete or missing, the degree to which assumptions made to
complete the data sets are inaccurate, errors in estimating emissions
values, and other factors. The emission values considered in this
analysis generally are annual totals that do not reflect short-term
fluctuations during the course of a year or variations from year to
year. In contrast, the estimates of peak hourly emission rates for the
acute effects screening assessment were based on multiplication factors
applied to the average annual hourly emission rates (the default factor
is 10), which are intended to account for emission fluctuations due to
normal facility operations. In some cases, more refined estimates were
used for source categories where the screening estimates did not
``screen out'' all sources and more specific information was available.
Additionally, for some source categories our estimate of the number of
facilities may not represent the number of facilities that we have in
our notice of proposed rulemaking data set. There is also significant
uncertainty for some source categories in the identification of sources
as major or area in the NEI.
b. Uncertainties in Dispersion Modeling
    While the analysis employed EPA's recommended regulatory dispersion
model, AERMOD, we recognize that there is uncertainty in ambient
concentration estimates associated with any model, including AERMOD.
Where possible, model options (e.g., rural/urban, plume depletion,
chemistry) were selected to provide an overestimate of ambient air
concentrations of the HAP. However, because of practicality and data
limitation reasons, some factors (e.g., meteorology, building downwash)
have the potential in some situations to overestimate or underestimate
ambient impacts. For example, meteorological data were taken from a
single year (1991), and facility locations can be a significant
distance from the site where these data were taken. Despite these
uncertainties, we believe that at off-site locations and census block
centroids, the approach considered in the dispersion modeling analysis
should generally yield overestimates of ambient HAP concentrations.
c. Uncertainties in Inhalation Exposure
    The effects of human mobility on exposures were not included in the
assessment. Specifically, short-term mobility and long-term mobility
between census blocks in the modeling domain were not considered.\20\
As a result, this simplification will likely bias the assessment toward
overestimating the highest exposures. In addition, the assessment
predicted the chronic exposures at the centroid of each populated
census block as surrogates for the exposure concentrations for all
people living in that block. Using the census block centroid to predict
chronic exposures tends to over-predict exposures for people in the
census block who live further from the facility and under-predict
exposures for people in the census block who live closer to the
facility. Thus, using the census block centroid to predict chronic
exposures may lead to a potential understatement or overstatement of
the true maximum

impact, but is an unbiased estimate of average risk and incidence.
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    \20\ Short-term mobility is movement from one microenvironment
to another over the course of hours or days. Long-term mobility is
movement from one residence to another over the course of a
lifetime.
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    The assessments evaluate the cancer inhalation risks associated
with pollutant exposures over a 70-year period, which is the assumed
lifetime of an individual. In reality, both the length of time that
modeled emissions sources at facilities actually operate (i.e., more or
less than 70 years), and the domestic growth or decline of the modeled
industry (i.e., the increase or decrease in the number or size of
United States facilities), will influence the risks posed by a given
source category. Depending on the characteristics of the industry,
these factors will likely result in an overestimate (or possibly an
underestimate in the extreme case where a facility maintains or
increases its emission levels beyond 70 years and residents live beyond
70 years at the same location) both in individual risk levels and in
the total estimated number of cancer cases. Annual cancer incidence
estimates from exposures to emissions from these sources would not be
affected by uncertainty in the length of time emissions sources
operate.
    The exposure estimates used in these analyses assume chronic
exposures to ambient levels of pollutants. Because most people spend
the majority of their time indoors, actual exposures may not be as
high, depending on the characteristics of the pollutants modeled. For
many HAP, indoor levels are roughly equivalent to ambient levels, but
for very reactive pollutants or larger particles, these levels are
typically lower. This factor has the potential to result in an
overstatement of 25 to 30 percent of exposures.\21\
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    \21\ U.S. EPA. National-Scale Air Toxics Assessment for 1996.
(EPA 453/R-01-003; January 2001; page 85.)
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    In addition to the uncertainties highlighted above, there are
several factors specific to the acute exposure assessment that should
be highlighted. 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 human
activity patterns. In this assessment, we assume that individuals
remain for 1 hour at the point of maximum ambient concentration as
determined by the co-occurrence of peak emissions and worst-case
meteorological conditions. These assumptions would tend to overestimate
actual exposures since it is unlikely that a person would be located at
the point of maximum exposure during the time of worst-case impact.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the
reference values used in our risk assessments for cancer effects from
chronic exposures and non-cancer effects from both chronic and acute
exposures. Some uncertainties may be considered quantitatively, and
others generally are expressed in qualitative terms. We note as a
preface to this discussion a point on dose-response uncertainty that is
brought out in EPA's 2005 Cancer Guidelines; namely, that ``the primary
goal of EPA actions is protection of human health; accordingly, as an
Agency policy, risk assessment procedures, including default options
that are used in the absence of scientific data to the contrary, should
be health protective.'' (EPA 2005 Cancer Guidelines, pages 1-7.) This
is the approach followed here as summarized in the next several
paragraphs. A complete detailed discussion of uncertainties and
variabilities in dose-response relationships is given in the residual
risk documentation as referenced in section IV.A of this preamble,
which is available in the docket for this action.
    Cancer URE values used in our risk assessments are those that have
been developed to generally provide an upper bound estimate of risk.
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).\22\ In some circumstances, the true risk could be as
low as zero; however, in other circumstances the risk could also be
greater.\23\ When developing an upper bound estimate of risk and to
provide risk values that do not underestimate risk, health-protective
default approaches are generally used. To err on the side of ensuring
adequate health-protection, EPA typically uses the upper bound
estimates rather than lower bound or central tendency estimates in our
risk assessments, an approach that may have limitations for other uses
(e.g., priority-setting or expected benefits analysis).
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    \22\ IRIS glossary (http://www.epa.gov/NCEA/iris/help_
gloss.htm).
    \23\ 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.
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    Chronic non-cancer reference (RfC and RfD) values represent chronic
exposure levels that are intended to be health-protective levels.
Specifically, these values provide an estimate (with uncertainty
spanning perhaps an order of magnitude) of daily oral exposure (RfD) or
of a continuous inhalation exposure (RfC) to the human population
(including sensitive subgroups) that is likely to be without an
appreciable risk of deleterious effects during a lifetime. To derive
values that are intended to be ``without appreciable risk,'' the
methodology relies upon an uncertainty factor (UF) approach (U.S. EPA,
1993, 1994) which includes consideration of both uncertainty and
variability. When there are gaps in the available information, UF are
applied to derive reference values that are intended to protect against
appreciable risk of deleterious effects. UF are commonly default
values,\24\ e.g., factors of 10 or 3, used in the absence of compound-
specific data; where data are available, UF may also be developed using
compound-specific information. When data are limited, more assumptions
are needed and more UF are used. Thus, there may be a greater tendency
to overestimate risk in the sense that further study might support
development of reference values that are higher (i.e., less potent)
because fewer default assumptions are needed. However, for some
pollutants it is possible that risks may be underestimated.
---------------------------------------------------------------------------

    \24\ According to the NRC report, Science and Judgment in Risk
Assessment (NRC, 1994) ``[Default] options are generic approaches,
based on general scientific knowledge and policy judgment, that are
applied to various elements of the risk assessment process when the
correct scientific model is unknown or uncertain.'' The 1983 NRC
report, Risk Assessment in the Federal Government: Managing the
Process, defined default option as ``the option chosen on the basis
of risk assessment policy that appears to be the best choice in the
absence of data to the contrary'' (NRC, 1983a, p. 63). Therefore,
default options are not rules that bind the Agency; rather, the
Agency may depart from them in evaluating the risks posed by a
specific substance when it believes this to be appropriate. In
keeping with EPA's goal of protecting public health and the
environment, default assumptions are used to ensure that risk to
chemicals is not underestimated (although defaults are not intended
to overtly overestimate risk). See EPA 2004, An examination of EPA
Risk Assessment Principles and Practices, EPA/100/B-04/001 available
at: http://www.epa.gov/osa/pdfs/ratf-final.pdf.
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    While collectively termed ``UF,'' these factors account for a
number of different quantitative considerations when using observed
animal (usually rodent) or human toxicity data in the development of
the RfC. The UF are intended to account for: (1) Variation in
susceptibility among the members of the human population (i.e., inter-
individual variability); (2) uncertainty in extrapolating from
experimental animal data to humans (i.e., interspecies differences);
(3) uncertainty in extrapolating from data obtained in a study with
less-than-lifetime exposure

(i.e., extrapolating from sub-chronic to chronic exposure); (4)
uncertainty in extrapolating the observed data to obtain an estimate of
the exposure associated with no adverse effects; and (5) uncertainty
when the database is incomplete or there are problems with the
applicability of available studies. Many of the UF used to account for
variability and uncertainty in the development of acute reference
values are quite similar to those developed for chronic durations, but
they more often use individual UF values that may be less than 10. UF
are applied based on chemical-specific or health effect-specific
information (e.g., simple irritation effects do not vary appreciably
between human individuals, hence a value of 3 is typically used), or
based on the purpose for the reference value (see the following
paragraph). The UF applied in acute reference value derivation include:
(1) Heterogeneity among humans; (2) uncertainty in extrapolating from
animals to humans; (3) uncertainty in lowest observable adverse effect
(exposure) level to no observable effect (exposure) level adjustments;
and (4) uncertainty in accounting for an incomplete database on toxic
effects of potential concern. 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 reference value at
another exposure duration (e.g., 1 hour).
    Not all acute reference 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 reference value or
values being exceeded. Where relevant to the estimated exposures, the
lack of threshold values at different levels of severity should be
factored into the risk characterization as potential uncertainties.
    Although every effort is made to identify peer-reviewed reference
values for cancer and non-cancer effects for all pollutants emitted by
the sources included in this assessment, some pollutants have no peer-
reviewed reference values for cancer or chronic non-cancer or acute
effects. Since exposures to these pollutants cannot be included in a
quantitative risk estimate, an understatement of risk for these
pollutants at environmental exposure levels is possible.
    Additionally, chronic reference values for several of the compounds
included in this assessment are currently under EPA IRIS review and
revised assessments may determine that these pollutants are more or
less potent than the current value. We may re-evaluate residual risks
for the final rulemaking if, as a result of these reviews, a dose-
response metric changes enough to indicate that the risk assessment
supporting this notice may significantly understate human health risk.
e. Uncertainties in the Multipathway and Environmental Effects
Assessment
    We generally assume that when exposure levels are not anticipated
to adversely affect human health, they also are not anticipated to
adversely affect the environment. We generally rely on the facility-
specific levels of PB-HAP emissions to determine whether a full
assessment of the multi-pathway and environmental effects is necessary.
Because facility-specific PB-HAP emission levels were so far below
levels which would trigger a refined assessment of multi-pathway
impacts, we are confident that these types of impacts are insignificant
for these source categories.
f. Uncertainties in the Facility-Wide Risk Assessment
    The same uncertainties discussed above exist with regard to the
facility-wide risk assessments. Additionally, the degree of uncertainty
associated with facility-wide emissions and risks is generally greater
because we have not completed our review of emissions data for source
categories not currently undergoing an RTR review.
g. Uncertainties in the Demographic Analysis
    Our analysis of the distribution of risks across various
demographic groups is subject to the typical uncertainties associated
with census data (e.g., errors in filling out and transcribing census
forms), as well as the additional uncertainties associated with the
extrapolation of census-block group data (e.g., income level and
education level) down to the census block level.

B. How did we perform the technology review?

    Our technology review is focused on the identification and
evaluation of ``developments in practices, processes, and control
technologies.'' If a review of available information identifies such
developments, then we conduct an analysis of the technical feasibility
of requiring the implementation of these developments, along with the
impacts (costs, emission reductions, risk reductions, etc.). We then
make a decision on whether it is necessary to amend the regulation to
require these developments.
    Based on specific knowledge of each source category, we began by
identifying known developments in practices, processes, and control
technologies. For the purpose of this exercise, we considered any of
the following to be a ``development'':
     Any add-on control technology or other equipment that was
not identified and considered during MACT development;
     Any improvements in add-on control technology or other
equipment (that was identified and considered during MACT development)
that could result in significant additional emission reduction;
     Any work practice or operational procedure that was not
identified and considered during MACT development; and
     Any process change or pollution prevention alternative
that could be broadly applied that was not identified and considered
during MACT development.
    In addition to looking back at practices, processes, or control
technologies reviewed at the time we developed the MACT standard, we
reviewed a variety of sources of data to aid in our evaluation of
whether there were additional practices, processes, or controls to
consider. One of these sources of data was subsequent air toxics rules.
Since the promulgation of the MACT standards for the source categories
addressed in this proposal, EPA has developed air toxics regulations
for a number of additional source categories. In these subsequent air
toxic regulatory actions, we consistently evaluated any new practices,
processes, and control technologies. We reviewed the regulatory
requirements and/or technical analyses associated with these subsequent
regulatory actions to identify any practices, processes, and control
technologies considered in these efforts that could possibly be applied
to emission sources in the source categories under this current RTR
review.
    We also consulted EPA's RACT/BACT/LAER Clearinghouse (RBLC). The
terms ``RACT,'' ``BACT,'' and ``LAER'' are acronyms for different
program requirements under the CAA provisions addressing the national
ambient air quality standards. Control technologies, classified as RACT
(Reasonably Available Control Technology), BACT (Best Available Control
Technology), or LAER (Lowest Achievable Emission Rate) apply to
stationary sources depending on whether the sources are existing or
new, and on the size, age, and location of the facility. BACT and

LAER (and sometimes RACT) are determined on a case-by-case basis,
usually by State or local permitting agencies. EPA established the RBLC
to provide a central data base of air pollution technology information
(including technologies required in source-specific permits) to promote
the sharing of information among permitting agencies and to aid in
identifying future possible control technology options that might apply
broadly to numerous sources within a category or apply only on a
source-by-source basis. The RBLC contains over 5,000 air pollution
control permit determinations that can help identify appropriate
technologies to mitigate many air pollutant emission streams. We
searched this database to determine whether any practices, processes,
or control technologies are included for the types of processes used
for emission sources (e.g., tanks or vents) in the source categories
under consideration in this proposal.
    We also requested information from industry regarding developments
in practices, processes, or control technology. Finally, we reviewed
other information sources, such as State or local permitting agency
databases and industry-supported databases.

C. How did we perform the analyses for the other actions being
proposed?

    For several of the source categories considered in this proposal,
we identified significant emission points that were not previously
regulated under MACT. For these emission points, consistent with the
requirements of CAA sections 112(d)(2) and (3), we identified the MACT
floor for existing and new sources and considered beyond-the-floor
options.
    We also reviewed the SSM provisions of each of the six MACT
standards in light of Sierra Club v. EPA, 551 F.3d 1019. As part of
this review, we evaluated available information and engaged industry
concerning the type of activities and emissions that occur during
periods of startup or shutdown.
    Finally, we identified potential revisions to these MACT standards
to correct or clarify regulatory requirements. In the years since
promulgation and compliance with the MACT standards, EPA has received
comments and suggestions for improving the clarity of the MACT
standards in general, as well as rule-specific comments for some
individual MACT standards. These comments include such things as
identification of editorial errors in the rule, clarification of
existing rule text, regulatory obstacles to effective implementation of
or compliance with the rule provisions. EPA has also independently
identified these types of issues. We are proposing rule changes where
appropriate.

V. Analyses Results and Proposed Decisions

    This section of the preamble provides background information on the
MACT standards and source categories, the results of our RTR for each
source category, our proposed actions to address significant
unregulated emission points for a number of source categories, our
proposed decisions concerning the SSM provisions in each of the six
MACT standards, and the specific clarifications we are proposing for
selected MACT standards.

A. What are the results and proposed decisions for the Chromium
Electroplating source categories?

1. Overview of the Source Categories and MACT Standard
    National Emission Standards for Chromium Emissions from Hard and
Decorative Chromium Electroplating and Chromium Anodizing Tanks
(Chromium Electroplating MACT standards) were promulgated on January
25, 1995 (60 FR 4963), and codified at 40 CFR part 63, subpart N. The
Chromium Electroplating MACT standards regulate emissions of chromium
compounds from three related source categories: Hard Chromium
Electroplating, Decorative Chromium Electroplating, and Chromium
Anodizing. Within these source categories, the MACT standards apply to
all plants, both major and area sources, regardless of size.
    The Hard Chromium Electroplating source category consists of
facilities that plate base metals with a relatively thick layer of
chromium using an electrolytic process. Hard chromium electroplating
provides a finish that is resistant to wear, abrasion, heat, and
corrosion. These facilities plate large cylinders and industrial rolls
used in construction equipment and printing presses, hydraulic
cylinders and rods, zinc die castings, plastic molds, engine
components, and marine hardware.
    The Decorative Chromium Electroplating source category consists of