[Federal Register Volume 76, Number 97 (Thursday, May 19, 2011)]
[Proposed Rules]
[Pages 29032-29081]
[FR Doc No: 2011-11220]

Vol. 76

Thursday,

No. 97

May 19, 2011

Part II

Environmental Protection Agency

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40 CFR Part 63

National Emissions Standards for Hazardous Air Pollutants: Secondary
Lead Smelting; Proposed Rule

Federal Register / Vol. 76 , No. 97 / Thursday, May 19, 2011 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2011-0344; FRL-9303-4]
RIN 2060-AQ68

National Emissions Standards for Hazardous Air Pollutants:
Secondary Lead Smelting

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing amendments to the national emissions
standards for hazardous air pollutants for Secondary Lead Smelting to
address the results of the residual risk and technology review that EPA
is required to conduct by the Clean Air Act. These proposed amendments
include revisions to the stack emissions limits for lead; revisions to
the fugitive dust emissions control requirements; the addition of total
hydrocarbons emissions limits for reverberatory, electric, and rotary
furnaces; the addition of emissions limits and work practice
requirements for dioxins and furans; and the modification and addition
of testing and monitoring and related notification, recordkeeping, and
reporting requirements. We are also proposing to revise provisions
addressing periods of startup, shutdown, and malfunction to ensure that
the rules are consistent with a recent court decision.

DATES: Comments must be received on or before July 5, 2011. 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 June 20, 2011.
    Public Hearing. If anyone contacts EPA requesting to speak at a
public hearing by May 31, 2011, a public hearing will be held on June
3, 2011.

ADDRESSES: Submit your comments, identified by Docket ID Number EPA-HQ-
OAR-2011-0344, 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 Number
EPA-HQ-OAR-2011-0344.
     Fax:<PHONE_NUMBER>, Attention Docket ID Number EPA-HQ-
OAR-2011-0344.
     Mail: U.S. Postal Service, send comments to: EPA Docket
Center, EPA West (Air Docket), Attention Docket ID Number EPA-HQ-OAR-
2011-0344, 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 Number EPA-HQ-OAR-2011-0344. 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 Number EPA-HQ-OAR-
2011-0344. EPA's policy is that all comments received will be included
in the public docket without change and may be made available on-line
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. EPA has established a docket for this rulemaking under
Docket ID Number EPA-HQ-OAR-2011-0344. 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. If a public hearing is held, it will begin at 10
a.m. on June 3, 2011 and will be held at EPA's campus in Research
Triangle Park, North Carolina, or at an alternate facility nearby.
Persons interested in presenting oral testimony or inquiring as to
whether a public hearing is to be held should contact Ms. Virginia
Hunt, Office of Air Quality Planning and Standards, Sector Policies and
Programs Division, (D243-02), U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711; telephone number: (919)
541-0832.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Mr. Chuck French, Sector Policies and Programs Division
(D243-02), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711, telephone<PHONE_NUMBER>; 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, North Carolina 27711; telephone number:<PHONE_NUMBER>;
fax number:<PHONE_NUMBER>; and e-mail address<EMAIL_ADDRESS>
For information about the applicability of the NESHAP to a particular
entity, contact the appropriate person listed in Table 1 of this
preamble.

 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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Secondary Lead Smelting.........  Maria Malave,       Chuck French,
<PHONE_NUMBER><PHONE_NUMBER>,
<EMAIL_ADDRESS><EMAIL_ADDRESS>                ov
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\1\ EPA Office of Enforcement and Compliance Assurance.
\2\ EPA Office of Air Quality Planning and Standards.

SUPPLEMENTARY INFORMATION:

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:

ADAF age-dependent adjustment factors
AEGL acute exposure guideline levels
AERMOD air dispersion model used by the HEM-3 model
ANPRM advance notice of proposed rulemaking
ATSDR Agency for Toxic Substances and Disease Registry
BACT best available control technology
BLDS bag leak detection system
CAA Clean Air Act
CBI Confidential Business Information
CEMS continuous emissions monitoring system
CFR Code of Federal Regulations
CTE central tendency exposure
D/F dioxins and furans
EJ environmental justice
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guidelines
ERT Electronic Reporting Tool
HAP hazardous air pollutants
HEM-3 Human Exposure Model, Version 3
HEPA high efficiency particulate air
HHRAP Human Health Risk Assessment Protocols
HI Hazard Index
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 emissions rate
lb/yr pounds per year
MACT maximum achievable control technology
MACT Code Code within the NEI used to identify processes included in
a source category
MDL method detection level
mg/acm milligrams per actual cubic meter
mg/dscm milligrams per dry standard cubic meter
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
MRL minimum risk level
NAAQS National Ambient Air Quality Standard
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
NEI National Emissions Inventory
NESHAP National Emissions Standards for Hazardous Air Pollutants
NOAEL no observed adverse effects level
NRC National Research Council
NTTAA National Technology Transfer and Advancement Act
O&M operation and maintenance
OAQPS Office of Air Quality Planning and Standards
ODW Office of Drinking Water
OECA Office of Enforcement and Compliance Assurance
OHEA Office of Health and Environmental Assessment
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PM particulate matter
POM polycyclic organic matter
ppmv parts per million volume
RACT reasonably available control technology
RBLC RACT/BACT/LAERClearinghouse
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RIA Regulatory Impact Analysis
RME reasonable maximum exposure
RTR residual risk and technology review
SAB Science Advisory Board
SBA Small Business Administration
SCC Source Classification Codes
SF3 2000 Census of Population and Housing Summary
SIP State Implementation Plan
SOP standard operating procedures
SSM startup, shutdown, and malfunction
TEF toxic equivalency factors
TEQ toxic equivalency quotient
THC total hydrocarbons
TOSHI target organ-specific hazard index
TPY tons per year
TRIM Total Risk Integrated Modeling System
TTN Technology Transfer Network
UF uncertainty factor
[mu]/m\3\ microgram per cubic meter
UL upper limit
UMRA Unfunded Mandates Reform Act
UPL upper predictive limit
URE unit risk estimate
VOC volatile organic compounds
VOHAP volatile organic hazardous air pollutants
WESP wet electrostatic precipitator
WHO World Health Organization
WWW worldwide Web

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

I. General Information
    A. What is the statutory authority for this action?
    B. Does this action apply to me?
    C. Where can I get a copy of this document and other related
information?
    D. What should I consider as I prepare my comments for EPA?
II. Background
    A. Overview of the Source Category and MACT Standards
    B. What data collection activities were conducted to support
this action?
III. Analyses Performed
    A. Addressing Unregulated Emissions Sources
    B. How did we estimate risks posed by the source category?
    C. How did we consider the risk results in making decisions for
this proposal?
    D. How did we perform the technology review?
    E. What other issues are we addressing in this proposal?
IV. Analyses Results and Proposed Decisions
    A. What are the results of our analyses and proposed decisions
regarding unregulated emissions sources?
    B. What are the results of the risk assessments and analyses?
    C. What are our proposed decisions based on risk acceptability
and ample margin of safety?
    D. What are the results and proposed decisions based on our
technology review?
    E. What other actions are we proposing?
    F. What is the relationship of the Secondary Lead Smelting
standards proposed in today's action and implementation of the lead
NAAQS?
    G. Compliance Dates
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. 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

I. General Information

A. What is the statutory authority for this action?

    Section 112 of the 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 CAA section 112(b),
CAA section 112(d) calls for us to promulgate NESHAP for those sources.
``Major sources'' are those that emit or have the potential to emit 10
tons per year (tpy) or more of a single HAP or 25 tpy or more of any
combination of HAP. For major sources, these technology-based standards
must reflect the maximum degree of emissions 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 must require the maximum degree of emissions
reduction through the application of measures, processes, methods,
systems, or techniques, including, but not limited to, measures that
(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 standards may take the form of design,
equipment, work practice, or operational standards where EPA first
determines either that, (A) a pollutant cannot be emitted through a
conveyance designed and constructed to emit or capture the pollutants,
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 emissions 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 emissions 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 considerations of the cost of achieving the
emissions reductions, any non-air quality health and environmental
impacts, and energy requirements.
    EPA is then required to review these technology-based standards and
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, and, in particular, is not obligated to recalculate the
MACT floors. NRDC v. EPA, 529 F.3d 1077, 1084 (DC Cir., 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 the risks posed
(or potentially posed) by sources after implementation of the MACT
standards, the public health significance of those risks, and EPA's
recommendations as to legislation regarding 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.
    Section 112(f)(2) of the CAA requires us to determine, for source
categories subject to certain MACT standards, whether those emissions
standards provide an ample margin of safety to protect public health.
If the MACT standards that apply to a source category emitting a HAP
that is ``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 one-in-one 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 (CAA section
112(f)(2)(A)). This requirement is procedural. It mandates that EPA
establish CAA section 112(f) residual risk standards if certain risk
thresholds are not satisfied, but does not determine the level of those
standards. NRDC v. EPA, 529 F. 3d at 1083. The second sentence of CAA
section 112(f)(2) sets out the substantive requirements for residual
risk standards: protection of public health with an ample margin of
safety based on EPA's interpretation of this standard in effect at the
time of the Clean Air Act amendments. Id. This refers to the Benzene
NESHAP, described in the next paragraph. EPA may adopt residual risk
standards equal to existing MACT standards if EPA determines that the
existing standards are sufficiently protective, even if (for example)
excess cancer risks to a most exposed individual are not reduced to
less than one-in-one million. Id. at 1083, (``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''). Section 112(f)(2) of the CAA further
authorizes EPA to adopt more stringent standards, if necessary ``to
prevent, taking into consideration costs, energy, safety, and other
relevant factors, an adverse environmental effect.'' \1\
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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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    As just noted, CAA section 112(f)(2) expressly preserves our use of
the two-step process for developing standards to address any residual
risk and our interpretation of ``ample margin of safety'' developed in
the National Emissions Standards for Hazardous Air Pollutants: Benzene
Emissions From Maleic Anhydride Plants, Ethylbenzene/Styrene Plants,
Benzene Storage Vessels,

Benzene Equipment Leaks, and Coke By-Product Recovery Plants (Benzene
NESHAP) (54 FR 38044, September 14, 1989). The 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 necessary 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 EPA's interpretation set
out in the Benzene NESHAP, and the court in NRDC v. EPA concluded that
EPA's interpretation of CAA section 112(f)(2) is a reasonable one. See
NRDC v. EPA, 529 F.3d at 1083 (DC Cir. 2008), which says ``[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.'' See also, A Legislative History of the Clean Air
Act Amendments of 1990, volume 1, p. 877 (Senate debate on Conference
Report). We also 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 risks 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 rather considers
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 DC Circuit's en banc 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-emissions 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. Does this action apply to me?

    The regulated industrial source category that is the subject of
this proposal is listed in Table 2 of this preamble. Table 2 of this
preamble is not intended to be exhaustive, but rather provides a guide
for readers regarding the entities likely to be affected by this
proposed action. These standards, once finalized, will be directly
applicable to affected sources. Federal, State, local, and Tribal
government entities are not affected by this proposed action. As
defined in the source category listing report published by EPA in 1992,
the Secondary Lead Smelting source category is defined as any facility
at which lead-bearing scrap materials (including, but not limited to
lead acid batteries) are recycled by smelting into elemental lead or
lead alloys.\2\ For clarification purposes, all references to lead
emissions in this preamble mean ``lead compounds'' (which is a listed
HAP) and all references to lead

production mean elemental lead (which is not a listed HAP as provided
under CAA section 112(b)(7)).
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    \2\ USEPA. Documentation for Developing the Initial Source
Category List--Final Report, USEPA/OAQPS, EPA-450/3-91-030, July,
1992.

                Table 2--NESHAP and Industrial Source Categories Affected by This Proposed Action
----------------------------------------------------------------------------------------------------------------
               Source category                            NESHAP               NAICS code \1\     MACT code \2\
----------------------------------------------------------------------------------------------------------------
Secondary Lead Smelting.....................  Secondary Lead Smelting.......            331492              0205
----------------------------------------------------------------------------------------------------------------
\1\ North American Industry Classification System.
\2\ Maximum Achievable Control Technology.

C. 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 EPA's 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 estimates and other data that were used as inputs to
the risk assessments.

D. 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-ROMas CBI and then identify electronically within the disk or CD-
ROMthe 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-ROMor disk that does not contain CBI, mark the outside
of the disk or CD-ROMclearly 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, North Carolina
27711, Attention Docket ID Number EPA-HQ-OAR-2011-0344.

II. Background

A. Overview of the Source Category and MACT Standards

    The NESHAP (or MACT rule) for the Secondary Lead Smelting source
category was promulgated on June 13, 1997 (62 FR 32216) and codified at
40 CFR part 63, subpart X. As promulgated in 1997, the NESHAP applies
to affected sources of HAP emissions at secondary lead smelters. The
1997 NESHAP (40 CFR 63.542) defines ``secondary lead smelters'' as
``any facility at which lead-bearing scrap material, primarily, but not
limited to, lead-acid batteries, is recycled into elemental lead or
lead alloys by smelting.'' The MACT rule for the Secondary Lead
Smelting source category does not apply to primary lead smelters, lead
remelters, or lead refiners.
    Today, there are 14 secondary lead smelting facilities that are
subject to the MACT rule. No new secondary lead smelters have been
built in the last 20 years, and we anticipate no new secondary lead
smelting facilities in the foreseeable future, although there is one
facility currently in the process of expanding operations.
    Lead is used to make various construction, medical, industrial and
consumer products such as batteries, glass, x-ray protection gear and
various fillers. The secondary lead smelting process consists of: (1)
Pre-processing of lead bearing materials, (2) melting lead metal and
reducing lead compounds to lead metal in the smelting furnace, and (3)
refining and alloying the lead to customer specifications.
    HAP are emitted from secondary lead smelting as process emissions,
process fugitive emissions, and fugitive dust emissions. Process
emissions are the exhaust gases from feed dryers and from blast,
reverberatory, rotary, and electric furnaces. The HAP in process
emissions are primarily composed of metals (mostly lead compounds, but
also some arsenic, cadmium, and other metals) and also may include
organic compounds that result from incomplete combustion of coke that
is charged to the smelting furnaces as a fuel or fluxing agent or from
fuel natural gas and/or small amounts of plastics or other materials
that get fed into the furnaces along with the lead bearing materials.
Process fugitive emissions occur at various points during the smelting
process (such as during charging and tapping of furnaces) and are
composed primarily of metal HAP. Fugitive dust emissions result from
the entrainment of HAP in ambient air due to material handling, vehicle
traffic, wind erosion from storage piles, and other various activities.
Fugitive dust emissions are composed of metal HAP only.
    The MACT rule applies to process emissions from blast,
reverberatory, rotary, and electric smelting furnaces, agglomerating
furnaces, and dryers; process fugitive emissions from smelting furnace
charging points, smelting furnace lead and slag taps, refining kettles,
agglomerating furnace product taps, and dryer transition pieces; and
fugitive dust emissions sources such as roadways, battery breaking
areas, furnace charging and tapping areas, refining and casting areas,
and material storage areas. For process sources, the NESHAP specifies
numerical emissions limits for lead compounds (as a surrogate for metal
HAP) for the following types of smelting furnaces: (1) Collocated
reverberatory and blast furnaces (reverberatory/blast), (2) blast
furnaces, and (3) reverberatory furnaces not collocated with blast
furnaces, rotary furnaces, and electric furnaces. Lead compound
emissions from all smelting furnace configurations are limited to an
outlet concentration of 2.0 milligrams per dry standard cubic meter
(mg/dscm) (0.00087 grains per dry standard cubic foot (gr/dscf)), 40
CFR 63.543(a). Total hydrocarbon (THC) emissions (as a surrogate for
organic HAP) from existing and new collocated reverberatory/blast
furnace

configurations are limited to an outlet concentration of 20 parts per
million volume (ppmv) (expressed as propane) corrected to 4 percent
carbon dioxide (CO2) to account for dilution. THC emissions
are limited to 360 ppmv (as propane) at 4 percent CO2 from
existing blast furnaces and 70 ppmv (as propane) at 4 percent
CO2 from new blast furnaces (40 CFR 63.543(c)). The NESHAP
does not specify emissions limits for THC emissions from reverberatory
furnaces not collocated with blast furnaces, rotary furnaces, and
electric furnaces.
    The 1997 NESHAP requires that process fugitive emissions sources be
equipped with an enclosure hood meeting minimum face velocity
requirements or be located in a total enclosure subject to general
ventilation that maintains the building at negative pressure (40 CFR
63.543(b)). Ventilation air from the enclosure hoods and total
enclosures is required to be conveyed to a control device. Lead
emissions from these control devices are limited to 2.0 mg/dscm
(0.00087 gr/dscf) (40 CFR 63.544(c)). Lead emissions for all dryer
emissions vents and agglomerating furnace vents are limited to 2.0 mg/
dscm (0.00087 gr/dscf) (40 CFR 63.544(d)). The 1997 NESHAP also
requires the use of bag leak detection systems (BLDS) for continuous
monitoring of baghouses in cases where a high efficiency particulate
air (HEPA) filter was not used in series with a baghouse (40 CFR
63.548(c)(9)).
    For fugitive dust sources, as defined in 40 CFR 63.545, the 1997
NESHAP requires that the smelting process and all control devices be
operated at all times according to a standard operating procedures
(SOP) manual developed by the facility. The SOP manual is required to
describe, in detail, the measures used to control fugitive dust
emissions from plant roadways, battery breaking areas, furnace areas,
refining and casting areas, and material storage and handling areas.

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

    In June 2010, EPA issued an information collection request (ICR),
pursuant to CAA section 114, to six companies that own and operate the
14 secondary lead smelting facilities. The ICR requested available
information regarding process equipment, control devices, point and
fugitive emissions, practices used to control fugitive emissions, and
other aspects of facility operations. The six companies completed the
surveys for their facilities and submitted the responses to us in the
fall of 2010. In addition to the ICR survey, each facility was asked to
submit reports for any emissions tests conducted in 2003 or later. We
received lead emissions test data from all 14 facilities with some
facilities submitting data for multiple years. Additionally, EPA
requested that eight facilities conduct additional emissions tests in
2010 for certain HAP from specific processes that were considered
representative of the industry. Pollutants tested included most HAP
metals, dioxins and furans, and certain organic HAP. The results of
these tests were submitted to EPA in the fall of 2010 and are available
in the docket for this action.

III. Analyses Performed

    In this section we describe the analyses performed to support the
proposed decisions for the RTR for this source category.

A. Addressing Unregulated Emissions Sources

    In the course of evaluating the Secondary Lead Smelting source
category, we identified certain HAP for which we failed to establish
emission standards in the original MACT. See National Lime v. EPA, 233
F. 3d 625, 634 (DC Cir. 2000) (EPA has ``clear statutory obligation to
set emissions standards for each listed HAP''). Specifically, we
evaluated emissions standards for three HAP (or groups of HAP),
described below, that are not specifically regulated in the existing
1997 MACT standard, or are only regulated for certain emissions points.
As described below, for two of these groups of HAP (i.e., organic HAP
and dioxins and furans) we are proposing emissions limits pursuant to
112(d)(2) and 112(d)(3). For the other HAP (mercury compounds), we are
proposing standards based on work practices pursuant to 112(h). The
results and proposed decisions based on the analyses performed pursuant
to CAA section 112(d)(2), 112(d)(3), and 112(h) are presented in
Section IV.A of this preamble.
1. Organic HAP
    EPA did not establish standards for organic HAP emitted from
reverberatory furnaces not collocated with blast furnaces, rotary
furnaces, and electric furnaces in the 1997 NESHAP. EPA is therefore
proposing to set emissions limits for organic HAP emissions from these
furnace configurations in today's action based on emissions data
received in response to the ICR.
2. Mercury
    The 1997 NESHAP specified emissions limits for metal HAP (e.g.,
arsenic, cadmium, lead) in terms of a lead emissions limit (i.e., lead
is used as a surrogate for metal HAP). There is no explicit standard
for mercury and we are therefore proposing a standard pursuant to
section 112 (as described further in section IV.A of this preamble).
3. Dioxins and Furans
    Lastly, with regard to dioxin and furan emissions, because the 1997
NESHAP did not include emissions limits, we are proposing emissions
standards for dioxins and furans pursuant to CAA section 112(d)(3). We
are also proposing work practices for dioxins and furans.

B. How did we estimate risks posed by the source category?

    EPA conducted a risk assessment that provided estimates of the
maximum individual cancer risk (MIR) posed by the HAP emissions from
the 14 sources in the source category, the distribution of cancer risks
within the exposed populations, total cancer incidence, estimates of
the maximum target organ-specific hazard index (TOSHI) for chronic
exposures to HAP with the potential to cause chronic non-cancer health
effects, worst-case screening estimates of hazard quotients (HQ) for
acute exposures to HAP with the potential to cause non-cancer health
effects, and an evaluation of the potential for adverse environmental
effects. In June of 2009, the EPA's Science Advisory Board (SAB)
conducted a formal peer review of our risk assessment methodologies in
its review of the document entitled, ``Risk and Technology Review (RTR)
Assessment Methodologies''.\3\ We received the final SAB report on this
review in May of 2010.\4\ Where appropriate, we have responded to the
key messages from this review in developing the current risk
assessment; we will be continuing our efforts to improve our
assessments by incorporating updates based on the SAB recommendations
as they are developed and become available. The risk assessment
consisted of seven primary steps, as discussed below.
---------------------------------------------------------------------------

    \3\ U.S. EPA, 2009. Risk and Technology Review (RTR) Risk
Assessment Methodologies: For Review by the EPA's Science Advisory
Board with Case Studies--MACT I Petroleum Refining Sources and
Portland Cement Manufacturing. EPA-452/R-09-006. http://www.epa.gov/ttn/atw/rrisk/rtrpg.html.
    \4\ U.S. EPA, 2010. SAB's Response to EPA's RTR Risk Assessment
Methodologies. http://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
---------------------------------------------------------------------------

    The docket for this rulemaking contains the following document,
which provides more information on the risk

assessment inputs and models: Draft Residual Risk Assessment for the
Secondary Lead Smelting Source Category.
1. Establishing the Nature and Magnitude of Actual Emissions and
Identifying the Emissions Release Characteristics
    For each facility in the Secondary Lead Smelting source category,
we compiled an emissions profile (including emissions estimates, stack
parameters, and location data) based on the information provided by the
industry in the ICR, the emissions test data, various calculations, and
the NEI. The site-specific emissions profiles include annual estimates
of process, process fugitive, and fugitive dust emissions for the 2008-
2010 timeframe, as well as emissions release characteristics such as
emissions release height, temperature, velocity, and location
coordinates.
    The primary risk assessment is based on estimates of the actual
emissions (though we also analyzed allowable emissions and the
potential risks due to allowable emissions). We received a substantial
amount of emissions test data and other information that enabled us to
derive estimates of stack emissions of certain HAP for all of the
facilities. However, we did not have test data for all pollutants at
all emissions points. Therefore, we estimated emissions of some
pollutants from certain emissions points (for which we had no emissions
data) using test data from similar source types with similar controls.
    With regard to fugitive emissions, because they cannot be readily
captured or directly measured, fugitive emissions are a more
challenging emissions type to estimate. In 2010, as part of an
information collection request (ICR), EPA asked the Secondary Lead
industry to provide their best estimate of the emissions from fugitive
sources (e.g., building openings, raw material storage piles, roadways,
parking areas) at their facilities and to provide a description of the
basis for the estimates (e.g., test data, emissions factors, mass
balance calculations, engineering judgment). For our analysis of
fugitive emissions for the source category, we first reviewed and
evaluated the estimates of fugitive lead emissions that were submitted
by each of the facilities in response to the 2010 ICR to determine the
reliability and appropriateness of those estimates as an input to our
risk analyses and other assessments. We concluded that there were
significant gaps and incomplete documentation for a number of
facilities, a large amount of variability in estimates between the
facilities, and various significant uncertainties. For example, five
facilities did not provide any estimates of fugitive emissions, while a
few other facilities provided emissions estimates that were quite
incomplete. Thus, we developed estimates of fugitive emissions for all
facilities in the source category based on a methodology described in
the emissions development technical document (Draft Development of the
RTR Emissions Dataset for the Secondary Lead Smelting Source Category)
for this rulemaking, which is available in the docket. In this
methodology, we began with estimates provided by one facility in the
ICR which were well-documented and covered all the various fugitive
emissions sources expected at these facilities. Using the ICR
responses, other available information on fugitive emissions (including
scientific literature), and various assumptions and calculations, we
scaled these estimates to derive site-specific fugitive emissions
estimates at each of the other 13 facilities. The estimates calculated
using this methodology were used as inputs to the risk assessment
modeling.
    The results of the risk assessment modeling (which are described
further in section IV below) indicated that the fugitive dust emissions
were the largest contributor to the risks due to lead emissions. The
impacts of fugitive emissions were generally considerably greater than
the impacts due to stack emissions. Because of these impacts, and
because of the difficulties and uncertainties associated with
estimating fugitive emissions, we decided to do further analyses and
review of the fugitive emissions estimates as a quality assurance check
on the initial fugitive emissions estimates. Therefore, we consulted
further with industry representatives, gathered additional information
from the EPA's Toxics Release Inventory, evaluated the ICR responses
further, and performed various other analyses, which led to the
development of an alternative set of fugitive emissions estimates based
on a slightly different methodology. The total fugitive estimates of
lead for the industry calculated based on the alternative approach are
within 10 percent of our initial estimates. We did not rerun the model
with the alternative estimates because we know that the overall results
would be quite similar and would not change our overall conclusions and
decisions (described later in this notice). Further details on all the
emissions data, calculations, estimates, and uncertainties, are in the
emissions technical document (Draft Development of the RTR Emissions
Dataset for the Secondary Lead Smelting Source Category) which is
available in the docket for this action. We are seeking comments on our
emissions data and estimates, and the fugitive emissions estimation
methodologies and any other potential appropriate methods or data that
could be used to estimate fugitive emissions from these facilities.
2. Establishing the Relationship Between Actual Emissions and MACT-
Allowable Emissions Levels
    The emissions data in our data set are estimates of actual
emissions on an annual basis for stacks and fugitives for the 2008-2010
timeframe. With most source categories, we generally find that
``actual'' emissions levels are lower than the emissions levels that a
facility is allowed to emit under the MACT standards. The emissions
levels allowed to be emitted by the MACT standards are referred to as
the ``MACT-allowable'' emissions levels. This represents the highest
emissions level that could be emitted by facilities without violating
the MACT standards.
    As we have discussed in prior residual risk and technology review
rules, assessing the risks at the MACT-allowable level is inherently
reasonable since these risks reflect the maximum level at which sources
could emit while still complying with the MACT standards. However, 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 emissions standards to provide
an operational cushion to accommodate the variability in manufacturing
processes and control device performance. Facilities' actual emissions
may also be significantly lower than MACT-allowable emissions for other
reasons such as State requirements, better performance of control
devices than required by the MACT standards, or reduced production.
    For the Secondary Lead Smelting source category, we evaluated
actual and allowable emissions for both stack emissions and fugitive
dust emissions. As described earlier in this section, the actual
emissions data for this source category were compiled based on the ICR
responses, available test data, various calculations, and the NEI. We
estimated actual emissions for all HAP that we identified in the
dataset. The

analysis of allowable emissions was largely focused on lead compound
emissions, which we considered the most important HAP emitted from this
source category based on our screening level risk assessment and the
HAP for which we had the most data. However, we also considered
allowable emissions for other HAP.
    With regard to fugitive emissions, because there are no numerical
emissions limits, and because all facilities are required to implement
identical fugitive emissions control work-practices, we assume that the
allowable fugitive emissions from this source category are equal to the
actual emissions.
    To estimate emissions at the MACT-allowable level from stacks
(e.g., process, process fugitive, and building vents), we estimated the
emissions that would occur if facilities were continuously emitting
lead at the maximum allowed by the existing MACT standard (i.e., 2.0
mg/dscm) from all vents. We then compared these estimated allowable
emissions to the estimated emissions using the actual stack test data
for each facility. We realize that these estimates of allowable
emissions are theoretical high-end estimates as facilities must
maintain average emissions levels at some level below the MACT limit to
ensure compliance with the standard at all times because of the day-to-
day variability in emissions. Nevertheless, these high-end estimates of
allowable emissions were adequate for us to estimate the magnitude of
allowable emissions and the differences between the estimates of actual
emissions and the MACT allowable emissions.
    Based on this analysis, we conclude that all facilities are
emitting lead at levels lower than allowable; however, the range of
differences between actual and allowable is significant. For two
facilities, the estimated actual emissions were only moderately lower
than allowable (about 2-3 times lower). The majority of other
facilities have estimated actual emissions in the range of 10 to 100
times lower than allowable. Finally, one facility, which has highly
advanced controls, has estimated actual emissions of about 1,500 times
below the MACT allowable emissions level.
    We then developed a ratio of MACT-allowable to actual emissions for
each facility in the source category. After developing these ratios, we
applied them on a facility-by-facility basis to the maximum modeled
ambient lead concentrations to estimate the maximum ambient
concentrations that would occur if all stacks were emitting at maximum
allowable levels. The ratios were applied to stack emissions while
leaving fugitive dust emissions at actual levels since, as described
above, actual fugitive dust emissions were assumed to be equal to
allowable fugitive dust emissions. The estimates of MACT-allowable
emissions are described further in the technical document: Draft
Development of the RTR Emissions Dataset for the Secondary Lead
Smelting Source Category. The estimates of risks due to allowable
emissions are summarized in Section IV.B of this preamble and described
further in the draft risk report: Draft Residual Risk Assessment for
the Secondary Lead Smelting Source Category.
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 the source category 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.\5\ 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 \6\ internal point locations
and populations, provides the basis of human exposure calculations
based on the year 2000 U.S. Census. In addition, for each census block,
the census library includes the elevation and controlling hill height,
which are also used in dispersion calculations. A third library of
pollutant 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.
---------------------------------------------------------------------------

    \5\ 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).
    \6\ A census block is 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 concentrations 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 the facilities as the cancer risk associated
with a lifetime (70-year period) of exposure to the maximum
concentration at the centroid of inhabited census blocks. Individual
cancer risks were calculated by multiplying the estimated lifetime
exposure to the ambient concentration of each of the HAP (in micrograms
per cubic meter) 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. In general, for residual risk
assessments, we use URE values from EPA's Integrated Risk Information
System (IRIS). 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, if appropriate. For this review, URE values
and their sources (e.g., IRIS, CalEPA) can be found in Table 2.6-1(a)
in the risk assessment document entitled, Draft Residual Risk
Assessment for the Secondary Lead Smelting Source Category, which is
available in the docket for this proposed rulemaking.
    Incremental individual lifetime cancer risks associated with
emissions from the 14 facilities in 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 \7\) emitted by the modeled source. Cancer incidence and the
distribution of individual cancer risks for the population within 50 km
of the sources 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 models,
including AERMOD.
---------------------------------------------------------------------------

    \7\ 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 Science Advisory Board (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.
---------------------------------------------------------------------------

    To assess the 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 value, which is either the EPA RfC,
defined as ``an estimate (with uncertainty spanning perhaps an order of
magnitude) of a continuous inhalation exposure to the human population
(including sensitive subgroups) that is likely to be without an
appreciable risk of deleterious effects during a lifetime,'' or, in
cases where an RfC is not available, the Agency for Toxic Substances
and Disease Registry (ATSDR) chronic Minimal Risk Level (MRL) or the
CalEPA Chronic Reference Exposure Level (REL). Notably, the REL is
defined as ``the concentration level at or below which no adverse
health effects are anticipated for a specified exposure duration.''
    Worst-case 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 was located at this spot at a time when both the
peak (hourly) emissions rate and worst-case hourly dispersion
conditions occurred. In general, acute HQ values were calculated using
best available, short-term dose-response values. These acute dose-
response values include REL, Acute Exposure Guideline Levels (AEGL),
and Emergency Response Planning Guidelines (ERPG) for 1-hour exposure
durations. Notably, for HAP emitted from this source category, REL
values were the only such dose-response values available. As discussed
below, we used conservative assumptions for emissions 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.'' 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
does not automatically indicate an adverse health impact.
    To develop screening estimates of acute exposures, we first
developed estimates of maximum hourly emissions rates by multiplying
the average actual annual hourly emissions 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 emissions events, in a heavily-industrialized 4-county area
(Harris, Galveston, Chambers, and Brazoria Counties, Texas) were less
than twice the annual average hourly emissions rate. The highest peak
emissions event was 74 times the annual average hourly emissions rate,
and the 99th percentile ratio of peak hourly emissions rate to the
annual average hourly emissions rate was 9.\8\ This analysis is
provided in Appendix 4 of the Draft Residual Risk Assessment for
Secondary Lead Smelting that is available in the docket for this
action. Considering this analysis, unless specific process knowledge or
data are available to provide an alternate value, to account for more
than 99 percent of the peak hourly emissions, we generally apply the
assumption to most source categories that the maximum one-hour
emissions rate from any source other than those resulting in fugitive
dust emissions are 10 times the average annual hourly emissions rate
for that source. We use a factor other than 10 in some cases if we have
information that indicates that a different factor is appropriate for a
particular source category. Moreover, the factor of 10 is not applied
to fugitive dust sources because these emissions are minimized during
the meteorological conditions associated with the worst-case short-term
impacts (i.e., during low-wind, stable atmospheric conditions) in these
acute exposure screening assessments.
---------------------------------------------------------------------------

    \8\ 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 worst-case 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 any worst-
case 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. 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 emissions 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 (i.e.,
factor of 10) approach in our screening analysis. In the case of this
source category, we had no further information on peak-to-mean
emissions which could be used to refine the estimates. The only
refinement that was made to the acute screening assessments was to
ensure that the estimated worst-case HQ was not calculated at a
location within the facility boundaries.
4. Conducting Multipathway Exposure and Risk Modeling
    EPA evaluated 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 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).
    Emissions of five PB-HAP were identified in the emissions dataset
for the Secondary Lead Smelting source category, as follows: Lead
compounds, cadmium compounds, POM, dioxin and furans, and mercury.\9\
The dataset is described in the emissions technical document (Draft
Development of the RTR Emissions Dataset for the Secondary Lead
Smelting Source Category) which is available in the docket for this
action. As described in that document, lead emissions estimates are
based on multiple emission stack tests conducted over multiple years,
cadmium and dioxin and furans are based on emissions tests conducted in
2010. Mercury emissions estimates are based on test results in 2010
which included a large number of non-detects and conservative
assumptions about non-detects, and the estimates for POM are based on
reported estimates from the NEI or estimates provided by the companies
in the ICR responses in 2010.
---------------------------------------------------------------------------

    \9\ Most of the emissions test results for mercury emissions for
this industry were below detection limit. The emissions estimates
used in the risk assessment are based on the assumption that all the
non-detect test values were at the level of the detection limit.
Therefore, these estimated emissions for mercury are clear
overestimates. We conclude that the true amounts of emissions of
mercury from this source category are much lower than shown in this
assessment, but we are not able to quantify precisely how much
lower.
---------------------------------------------------------------------------

    Emissions of cadmium compounds, POM, dioxin and furans and mercury
were evaluated for potential non-inhalation risks and adverse
environmental impacts using our recently developed screening scenario
that was developed for use with the Total Risk Integrated Methodology
(TRIM.FaTE) model. This screening scenario uses environmental media
outputs from the peer-reviewed TRIM.FaTE to estimate the maximum
potential ingestion risks for any specified emissions scenario by using
a generic farming/fishing exposure scenario that simulates a
subsistence environment. The screening scenario retains many of the
ingestion and scenario inputs developed for EPA's Human Health Risk
Assessment Protocols (HHRAP) for hazardous waste combustion facilities.
In the development of the screening scenario, a sensitivity analysis
was conducted to ensure that its key design parameters were established
such that environmental media concentrations were not underestimated,
and to also minimize the occurrence of false positives for human health
endpoints. See Appendix 3 of the risk assessment document for a
complete discussion of the development and testing of the screening
scenario, as well as for the values of facility-level de minimis
emissions rates developed for screening potentially significant
multipathway impacts. For the purpose of developing de minimis
emissions rates for our multipathway screening, we derived emissions
levels at which the maximum human health risk could be 1-in-1 million
for lifetime cancer risk, or exposures could potentially be above the
reference dose for non-cancer effects, based on a conservative model
plant analysis described in Appendix 3 of the risk assessment document.
    For the secondary lead smelting source category, there were
exceedances of de minimis emissions rates at multiple facilities for
multiple PB-HAP, and thus a multipathway analysis was performed. Two
facilities were chosen as case study analyses to assess potential
multipathway risks for mercury, cadmium, POM, and dioxins and furans.
The selection criteria for modeling these two facilities included
emissions rates of PB-HAPs, proximity to water bodies, proximity to
farmland, average rainfall, average wind speed and direction, smelting
furnace type, local change in elevation, and geographic
representativeness of sites throughout the U.S. As a result of our
selection process, we believe the multipathway risks associated with
these two facilities are in the upper end of the potential for
multipathway risks from the source category. Since the modeling used in
these case study assessments utilize site specific parameters to
describe naturally occurring physical, chemical and biological
processes, we believe that the multimedia concentrations of PB-HAPs
generated in this analysis are unbiased estimates of the true impacts.
    In general, results of this assessment were designed to
characterize multipathway risks associated with high end consumption of
PB-HAP predominantly from contaminated food sources. Thus, multipathway
exposure and risk estimates were calculated for two basic scenarios,
both of which are expected to give rise to high-end exposures and
risks. The farmer scenario involves an individual living on a farm
homestead in the vicinity of a PB-HAP source who consumes contaminated
produce grown on the farm, as well as contaminated meat and animal
products raised on the farm. The farming scenario also accounts for
incidental ingestion of contaminated surface soil at the location of
the farm homestead. The recreational fisher scenario involves an
individual who regularly consumes fish caught in freshwater lakes in
the vicinity of a PB-HAP source. In the fishing scenario, in addition
to the characterization of exposure and risks across the broad
population of recreational anglers, exposures were also calculated for
three subpopulations of recreational anglers (Hispanic, Laotian, and
Vietnamese descent) who have higher rates of fish consumption.\10\
Furthermore, in order to more fully characterize the modeled potential
multipathway risks that may be associated with high-end consumption of
PB-HAP contaminated food, we present results based on two ingestion
exposure scenarios: (1) A reasonable maximum exposure (RME) scenario
that, for example, utilizes 90th percentile ingestion rates for
farmers, recreational anglers, and the three subpopulations of
recreational anglers (e.g., ingestion rates specific to Laotian
recreational anglers); and (2) a central tendency exposure (CTE)
scenario that, for example, utilizes mean ingestion rates for the
groups just described. We provide results from both scenarios to
illustrate the range of potential modeled exposures and risks that may
exist in the high-end of the complete distribution of potential
multipathway risks for this source category.
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    \10\ In both scenarios, exposure via drinking water was not
considered because it is unlikely that humans would use surface
waters as a drinking water source. Groundwater, which is a likely
source of drinking water, also was not included in the exposure
scenarios because contamination of groundwater aquifers by air
deposition sources was not expected to be significant. For dioxin,
exposure via breast milk was considered in the farming scenario as
well as the recreational fishing scenario, but not for the three
recreational fishing subpopulations (Hispanic, Laotian, and
Vietnamese descent) since subpopulation ingestion rates were only
applicable to adult males. The breast milk pathway was not
considered with respect to mercury exposure due to a current lack of
data regarding this pathway.
---------------------------------------------------------------------------

    In evaluating the potential air-related multipathway risks from the
emissions of lead compounds, rather than developing a de minimis
emissions rate, we compared its maximum modeled 3-month average
atmospheric lead concentration at any off-site location with the
current primary National Ambient Air Quality Standard (NAAQS) for lead
(promulgated in 2008), which is set at a level of 0.15 micrograms per
cubic meter ([micro]g/m\3\) based on rolling 3-month periods with a
not-to-be-exceeded level for any 3-month rolling average, and which
will require attainment by 2016 (73 FR 66964). Notably, in making these
comparisons, we estimated maximum rolling 3-month ambient lead
concentrations taking into account all of the elements of the NAAQS for
lead. That is, our estimated 3-month lead concentrations are

calculated in a manner that is consistent with the indicator, averaging
time, and form of the lead NAAQS, and those estimates are compared to
the level of the lead NAAQS (0.15 [micro]g/m\3\).
    The NAAQS value, a public health policy judgment, incorporated the
Agency's most recent health evaluation of air effects of lead exposure
for the purposes of setting a national standard. In setting this value,
the Administrator promulgated a standard that was requisite to protect
public health with an adequate margin of safety. That standard applies
everywhere, under all circumstances, regardless of an individual's
location, exposure patterns, or health circumstances. We consider
values below the level of the primary NAAQS to protect against
multipathway risks because, as mentioned above, the primary NAAQS is
set so as to protect public health with an adequate margin of safety.
However, ambient air lead concentrations above the NAAQS are considered
to pose the potential for increased risk to public health. We consider
this assessment--comparing modeled concentrations to the level of the
NAAQS--to be a refined analysis given: (1) The numerous health studies,
detailed risk and exposure analyses, and level of external peer and
public review that went into the development of the primary NAAQS for
lead, combined with: (2) the site-specific dispersion modeling
performed in the risk assessment to develop ambient concentration
estimates from the 14 secondary lead smelter facilities addressed in
this proposed rule. It should be noted, however, that this comparison
to the NAAQS for lead does not account for possible population
exposures to lead from sources other than the one being modeled; for
example, via consumption of water from contaminated local sources or
ingestion of contaminated locally grown food. Nevertheless, the
Administrator judged that the primary NAAQS would protect, with an
adequate margin of safety, the health of children and other at-risk
populations against an array of adverse health effects, most notably
including neurological effects, particularly neurobehavioral and
neurocognitive effects, in children (73 FR 67007). The Administrator,
in setting the standard, also recognized that no evidence of a risk-
based bright line indicated a single appropriate level. Instead, a
collection of scientific evidence and other information was used to
select the standard from a range of reasonable values (73 FR 67006).
    We further note that comparing ambient lead concentrations to the
NAAQS for lead, considering the level, averaging time, form and
indicator of the lead NAAQS, also informs whether there is the
potential for adverse environmental effects. This is because the
secondary lead NAAQS, which has the same averaging time, form, and
level as the primary standard, was set to protect the public welfare
which includes among other things soils, water, crops, vegetation and
wildlife (CAA section 302(h)). Thus, ambient lead concentrations above
the NAAQS for lead also indicate the potential for adverse
environmental effects (73 FR 67007 to 67012). For additional
information on the multipathway analysis approach, see the residual
risk documentation as referenced in Section III.A of this preamble. EPA
solicits comment generally on the modeling approach used herein to
assess air-related lead risks, and specifically on the use of the lead
NAAQS in this analytical construct.
5. Assessing Risks Considering Emissions Control Options
    In addition to assessing baseline inhalation risks and screening
for potential multipathway risks, we also estimated risks considering
the potential emissions reductions that would be achieved by the main
control options under consideration. The expected emissions reductions
were applied to the specific HAP and emissions points in the source
category dataset to develop corresponding estimates of risk reductions.
More information regarding the risks after control can be found in the
risk assessment document: Draft Residual Risk Assessment for the
Secondary Lead Smelting Source Category, 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, for our residual risk
review, we also examine the risks from the entire ``facility,'' where
the facility includes all HAP-emitting operations within a contiguous
area and under common control. In other words, we examine the HAP
emissions not only from the source category of interest, but also
emissions of HAP from all other emissions sources at the facility. In
this rulemaking, for the Secondary Lead Smelting source category, there
are no other significant HAP emissions sources present. Thus, there was
no need to perform a separate facility wide risk assessment.
    b. Demographic Analysis
    To identify specific groups that may be affected by this
rulemaking, EPA conducted demographic analyses. These analyses provide
information about the percentages of different social, demographic, and
economic groups within the populations subjected to potential HAP-
related cancer and non-cancer risks from the facilities in this source
category.
    For the demographic analyses, we focus on the populations within 50
km of any facility with emissions sources subject to the MACT standard
(identical to the risk assessment). Based on the emissions for the
source category or the facility, we then identified the populations
that are estimated to have exposures to HAP which result in: (1) Cancer
risks of 1-in-1 million or greater; (2) non-cancer HI of 1 or greater;
and/or (3) ambient lead concentrations above the level of the NAAQS for
lead. We compare the percentages of particular demographic groups
within the focused populations to the total percentages of those
demographic groups nationwide. The results, including other risk
metrics, such as average risks for the exposed populations, are
documented in a technical report in the docket for the source category
covered in this proposal.\11\
---------------------------------------------------------------------------

    \11\ Risk and Technology Review--Analysis of Socio-Economic
Factors for Populations Living Near Primary Lead Smelting
Operations.
---------------------------------------------------------------------------

    The basis for the risk estimates used in the demographic analyses
for this source category was the modeling results based on actual
emissions levels obtained from the HEM-3 model described above. The
risk estimates 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
were 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 census block level, the age and income census data are
only available at the census block group 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 census blocks within the block group have the same
distribution of ages and incomes as the block group.

    As noted above, we focused the analysis on those census blocks
where source category risk results show: (1) Estimated lifetime
inhalation cancer risks above 1-in-1 million; (2) chronic non-cancer
indices above 1; and/or (3) census blocks where estimated ambient lead
concentrations were above the level of the lead NAAQS. For each of
these cases, we determined the relative percentage of 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 people living below the poverty line within those census
blocks.
    The specific census population categories included:
     Total population
     White
     African American (or Black)
     Native Americans
     Other races and multiracial
     Hispanic or Latino
     People living below the poverty line
     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.
    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
``Minorities,'' a classification that is defined for these purposes as
all race population categories except white.
    The methodology and the results of the demographic analyses for
this source category are included in the technical report available in
the docket for this action (Risk and Technology Review--Analysis of
Socio-Economic Factors for Populations Living near Secondary Lead
Smelting Operations).
7. Considering Uncertainties in Risk Assessment
    Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for the source category
addressed in this proposal. Although uncertainty exists, we believe the
approach that we took, which used conservative tools and assumptions to
bridge data gaps, ensures that our decisions are health-protective. A
brief discussion of the uncertainties in the emissions dataset,
dispersion modeling, inhalation exposure estimates, dose-response
relationships, multipathway and environmental impacts analyses, and
demographics analysis follows below. A more thorough discussion of
these uncertainties is included in the risk assessment documentation
(Draft Residual Risk Assessment for the Secondary Lead Smelting
Category) available in the docket for this action.
a. Uncertainties in the Emissions Dataset
    Although the development of the RTR dataset involved quality
assurance/quality control processes, the accuracy of emissions values
will vary depending on the source of the data, the degree to which data
are incomplete or missing, the degree to which assumptions made to
complete the datasets are accurate, whether and to what extent errors
were made in estimating emissions values, and other factors. The
estimates of stack emissions are largely based on actual emissions test
data, and, therefore, we have a relatively high degree of confidence in
those estimates. With regard to fugitive emissions, those estimates are
largely based on engineering calculations and application of various
assumptions, and are therefore considered less certain relative to the
stack emissions estimates. Nevertheless, we believe the fugitive
estimates we derived for these facilities and used in our analyses are
reasonable estimates of the actual fugitive emissions from these
facilities partly due to the findings that the available ambient
monitoring data (which are described in the document Draft Summary of
the Ambient Lead Monitoring Data near Secondary Lead Smelting
Facilities, available in the docket) indicate that measured levels of
lead in ambient air near these facilities are generally similar in
magnitude (e.g., generally within a factor of 2) to the modeled
estimates (which are shown in the Draft Residual Risk Assessment for
the Secondary Lead Smelting Source Category, which is available in the
docket).
    The emissions estimates for stacks considered in this analysis are
hourly emissions rates primarily extracted from test reports and
extrapolated to an annual total based on the hours of operation of each
facility and may not reflect short-term fluctuations during the course
of a year or variations from year to year. The estimates of peak hourly
emissions rates from stacks for the acute effects screening assessment
were based on multiplication factors applied to the hourly emissions
rates (the default factor of 10 was used for Secondary Lead Smelting
for sources other than fugitive dust) which are intended to account for
emissions fluctuations due to normal facility operations.
    There is an unquantified level of uncertainty regarding the
emissions estimates for acute impacts of fugitive dusts. The current
set of assumptions used in deriving the worst-case acute impact
estimate for fugitive dusts assumes the average hourly emission level
(annual emissions divided by 8760 hours per year) to occur at the
default worst-case meteorological conditions (low winds with a stable
atmosphere). It is acknowledged that the combination of average
emissions during low winds would be an overestimate of the fugitive
dust emission rate during those low wind periods. Therefore, for
fugitive dusts, the worst case meteorology may not be the same as for
other process emissions, and the level of hourly fugitive dust
emissions during this alternate worst-case condition is unknown.
    We further note that there is additional uncertainty with respect
to emissions of mercury. As previously noted, most of the mercury
emissions test results for this industry were below detection limit.
The emissions estimates utilized in the risk assessment are based on
the health-protective assumption that all the non-detect test values
were at the level of the detection limit. Therefore, these estimated
emissions for mercury are clear overestimates. We conclude that the
true amounts of emissions of mercury from this source category are much
lower than those provided in the technical documents supporting today's
proposed rule, but we are not able to quantify precisely how much
lower.
b. Uncertainties in Dispersion Modeling
    Although 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. In circumstances where we had to choose between various model
options, where possible, we selected model options (e.g., rural/urban,
plume depletion, chemistry) that provided an overestimate of ambient
concentrations of the HAP rather than an underestimate. However,
because of practicality and data limitation reasons, some factors
(e.g., building downwash) have the potential in some situations to
overestimate or underestimate ambient impacts. 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.
    Furthermore, as noted previously, there is a level of uncertainty
in the

conditions leading to worst-case emissions for fugitive dusts. However,
in the absence of better information regarding actual short-term
impacts from fugitive dust sources, the combination of average hourly
emission level and worst-case meteorology was assumed to be useful for
deriving protective acute impact estimates.
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.\12\
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 farther 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 for any one individual, but is an unbiased
estimate of average risk and incidence.
---------------------------------------------------------------------------

    \12\ 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.
---------------------------------------------------------------------------

    The assessments evaluate the projected 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 future risks posed by
a given source or source category. Depending on the characteristics of
the industry, these factors will, in most cases, result in an
overestimate both in individual risk levels and in the total estimated
number of cancer cases. However, in rare cases, where a facility
maintains or increases its emissions levels beyond 70 years, residents
live beyond 70 years at the same location, and the residents spend most
of their days at that location, then the risks could potentially be
underestimated. 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 of the 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 for some HAP.\13\
---------------------------------------------------------------------------

    \13\ U.S. EPA. National-Scale Air Toxics Assessment for 1996.
(EPA 453/R-01-003; January 2001; page 85.)
---------------------------------------------------------------------------

    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 be worst-
case 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 dose-
response 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
variability in dose-response relationships is given in the residual
risk documentation 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).\14\ In some circumstances, the true risk could be as
low as zero; however, in other circumstances the risk could be
greater.\15\ 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).
---------------------------------------------------------------------------

    \14\ IRIS glossary (http://www.epa.gov/NCEA/iris/help_gloss.htm).
    \15\ 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.
---------------------------------------------------------------------------

    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 a continuous inhalation
exposure (RfC) or a daily oral exposure (RfD) 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 considers uncertainty, variability and gaps in the
available data. The UF are applied to derive reference values that are
intended to protect against appreciable risk of deleterious effects.
The UF are commonly default values,\16\ 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.
---------------------------------------------------------------------------

    \16\ 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.
---------------------------------------------------------------------------

    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
observed adverse effect (exposure) level to no observed adverse 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).
    As further discussed below, there is no RfD or other comparable
chronic health benchmark value for lead compounds. Thus, to address
multipathway human health and environmental risks associated with
emissions of lead from this facility, ambient lead concentrations were
compared to the NAAQS for lead. In developing the NAAQS for lead, EPA
considered human health evidence reporting adverse health effects
associated with lead exposure, as well as an EPA-conducted multipathway
risk assessment that applied models to estimate human exposures to air-
related lead and the associated risk (73 FR 66979). EPA also explicitly
considered the uncertainties associated with both the human health
evidence and the exposure and risk analyses when developing the NAAQS
for lead. For example, EPA considered uncertainties in the relationship
between ambient air lead and blood lead levels (73 FR 66974), as well
as uncertainties between blood lead levels and loss of IQ points in
children (73 FR 66981).
    In considering the evidence and risk analyses and their associated
uncertainties, EPA found that there is no evidence- or risk-based
bright line that indicates a single appropriate level. EPA noted there
is a collection of scientific evidence and judgments and other
information, including information about the uncertainties inherent in
many relevant factors, which needs to be considered together in making
the public health policy judgment and in selecting a standard level
from a range of reasonable values (73 FR 66998). In so doing, EPA
decided that a level for the primary lead standard of 0.15 [mu]g/
m3, in combination with the specified choice of indicator,
averaging time, and form, is requisite to protect public health,
including the health of sensitive groups, with an adequate margin of
safety (73 FR 67006). A thorough discussion of the health evidence,
risk and exposure analyses, and their associated uncertainties can be
found in EPA's final rule revising the lead NAAQS (73 FR 66970-66981,
November 12, 2008).
    We also note the uncertainties associated with the health-based
(i.e., primary) NAAQS are likely less than the uncertainties associated
with dose-response values developed for many of the other HAP,
particularly those HAP for which no human health data exist.
    We also note that because of the multipathway, multi-media impacts
of lead, the risk assessment supporting the NAAQS considered direct
inhalation exposures and indirect air-related multipathway exposures
from industrial sources like primary and secondary lead smelting
operations. It also considered background lead exposures from other
sources (like contaminated drinking water and exposure to lead-based
paints). In revising the NAAQS for lead, EPA placed more weight on the
evidence-based framework and less weight on the results from the risk
assessment, although the risk estimates were found to be roughly
consistent with and generally supportive of the evidence-based
framework applied in the NAAQS determination (73 FR 67004). Thus, when
revising the NAAQS for lead to protect public health with an adequate
margin of safety, EPA considered both the health evidence and the risk
assessment, albeit to different extents.
    In addition to the uncertainties discussed above with respect to
chronic, cancer, and the lead NAAQS reference values, there are also
uncertainties associated with acute reference values. 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 short-
term dose-response 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 hazardous air pollutants
continue to 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 (e.g.,
cadmium and nickel), 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 or overstate human health risk.
e. Uncertainties in the Multipathway and Environmental Impacts
Assessment
    For the secondary lead smelting source category, two facilities
were chosen as case study analyses to assess potential multipathway
risks for mercury, cadmium, POM, and dioxins and furans. The selection
criteria for modeling these two facilities included emissions rates of
PB-HAPs, proximity to water bodies, proximity to farmland, average
rainfall, average wind speed and direction, smelting furnace type,
local change in elevation, and geographic representativeness of sites
throughout the U.S. However, there is uncertainty as to whether these
two facilities represent the highest potential for multipathway human
health risks from the source category.
    Since the modeling used in these case study assessments utilize
site specific parameters to describe naturally occurring physical,
chemical and biological processes, we believe that the multimedia
concentrations of PB-HAPs generated in this analysis are unbiased
estimates of the true impacts.
    With respect to the risk estimates generated from this analysis, we
present results based on two ingestion exposure scenarios: the RME and
CTE scenarios. As noted above, we believe that these scenarios
illustrate the range of potential modeled exposures and risks that may
exist in the high-end of the complete distribution of potential
multipathway risks for this source category.
    We further note that high-end fisher populations could display
considerable variability both in terms of the degree to which they
frequent specific water bodies or watersheds and the degree to which
they target specific types of fish (or at least sizes of fish). Both of
these factors can impact estimates of exposure. If a fisher population
distributes their activity across a range of water bodies and harvests
a variety of fish species (and sizes) than the distribution of exposure
and risk across that population will be smaller compared with a
population that focuses activity at individual water bodies and tends
to focus on larger fish.
    To estimate potential high-end multipathway exposures and risks, in
addition to utilizing fish consumption rate data for the general U.S.
population of recreational anglers,\17\ we used fish consumption
information for distinct fisher subpopulations that are known to have
higher fish consumption rates. The data were obtained from Shilling, et
al. (2010).\18\ In this publication, the authors provide fish
consumption information for different ethnic groups including
Hispanics, Laotians, and Vietnamese surveyed in California's Central
Valley Delta based on sample sizes of 45, 33, and 30, respectively. We
note that there is uncertainty based on the limited sample sizes and in
the extrapolation of these fish consumption rates to other parts of the
United States. Further discussion of these values is provided in the
risk assessment supporting documents. We request comment on the use of
these data to support the RME analysis.
---------------------------------------------------------------------------

    \17\ Data for the general U.S. population of recreational
anglers was obtained from: EPA 2002, ``Estimated Per Capita Fish
Consumption in the United States, Office of Water, Office of Science
and Technology, Washington, DC, EPA-821-C-02-003. August 2002.
    \18\ Shilling, et al. 2010 is available in the docket for this
rulemaking.
---------------------------------------------------------------------------

    A more detailed discussion of the multipathway analysis and its
associated uncertainties is presented in section 5.3 of the document
Human Health Multipathway Residual Risk Assessment for the Secondary
Lead Smelting Source Category, which can be found in the docket for the
proposed rule.
f. Uncertainties in the Demographic Analysis
    Our analysis of the distribution of risks across various
demographic groups is subject to uncertainty associated with the
extrapolation of census-block group data (e.g., income level and
education level) down to the census block level.

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

    In evaluating and developing standards under section 112(f)(2), as
discussed in Section I.A of this preamble, we apply a two-step process
to address residual risk. In the first step, EPA determines whether
risks are acceptable. This determination ``considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR)
\19\ 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.)
---------------------------------------------------------------------------

    \19\ 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 actions, EPA has presented and considered 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 (72 FR 25138, May
3, 2007; 71 FR 42724, July 27, 2006). In our most recent proposals (75
FR 65068, October 21, 2010 and 75 FR 80220, December 21, 2010), EPA
also presented and considered additional measures of health
information, such as estimates of the risks associated with the maximum
level of emissions which might be allowed by the current MACT standards
(see, e.g., 75 FR 65068, October 21, 2010 and 75 FR 80220, December 21,
2010). EPA also discussed and considered risk estimation uncertainties.
EPA is providing this same type of information in support of the
proposed actions described in this Federal Register notice.
    The Agency is considering all 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 [previous] section 112 is best
judged on the basis of a broad set of health risk measures and
information'' (54 FR 38046). Similarly, with regard to making the ample
margin of safety determination, as stated in the Benzene NESHAP ``[in
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 provides
flexibility regarding what factors EPA might consider in making
determinations and how these factors 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 at 38057).
    Thus, the level of the MIR is only one factor to be weighed in
determining acceptability of risks. The Benzene NESHAP explained that
``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, EPA stated in the
Benzene NESHAP that: ``* * * EPA believes the relative weight of the
many factors that can be considered in selecting an ample margin of
safety can only be determined for each specific source category. This
occurs mainly because technological and economic factors (along with
the health-related factors) vary from source category to source
category'' (Id. at 38061).
    EPA wishes to point out that certain health information has not
been considered to date in making residual risk determinations. 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 generally we have also assessed risks due to HAP
emissions from the entire facility at which the covered source category
is located (facility-wide risk estimates). We have not attempted to
characterize the risks associated with all HAP emissions impacting the
populations living near the sources in these categories. That is, at
this time, we do not attempt to quantify those HAP risks that may be
associated with emissions from other facilities that do not include the
source categories in question, mobile source emissions, natural source
emissions, persistent environmental pollution, or atmospheric
transformation in the vicinity of the sources in these categories.
    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 health reference levels (e.g., Reference
Concentrations (RfCs)) 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 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.'' \20\
---------------------------------------------------------------------------

    \20\ 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.
---------------------------------------------------------------------------

    Although 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,
and hence would compound 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 comments and recommendations for any other comparative measures
that may be useful in the assessment of the distribution of HAP risks
across potentially affected demographic groups.

D. How did we perform the technology review?

    Our technology review focused on the identification and evaluation
of developments in practices, processes, and control technologies that
have occurred since the 1997 NESHAP was promulgated. In cases where the
technology review identified such developments, we conducted an
analysis of the technical feasibility of applying these developments,
along with the estimated impacts (costs, emissions reductions, risk
reductions, etc.) of applying these developments. We then made
decisions on whether it is necessary to propose amendments to the
regulation to require any of the identified developments.
    Based on our analyses of the data and information collected by the
ICR and our general understanding of the industry and other available
information on potential controls for this industry, we identified
several potential 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 development of the 1997 NESHAP.
     Any improvements in add-on control technology or other
equipment (that were identified and considered during development of
the 1997

NESHAP) that could result in significant additional emissions
reduction.
     Any work practice or operational procedure that was not
identified or considered during development of the 1997 NESHAP.
     Any process change or pollution prevention alternative
that could be broadly applied to the industry and that was not
identified or considered during development of the 1997 NESHAP.
    In addition to reviewing the practices, processes, or control
technologies that were not considered at the time we developed the 1997
NESHAP, we reviewed a variety of data sources in our evaluation of
whether there were additional practices, processes, or controls to
consider for the secondary lead smelting industry. Among the data
sources we reviewed were the NESHAP for various industries that were
promulgated after the 1997 NESHAP. We reviewed the regulatory
requirements and/or technical analyses associated with these regulatory
actions to identify any practices, processes, and control technologies
considered in these efforts that could possibly be applied to emissions
sources in the Secondary Lead Smelting source category, as well as the
costs, non-air impacts, and energy implications associated with the use
of these technologies.
    We also consulted EPA's RACT/BACT/LAER Clearinghouse (RBLC) to
identify potential technology advances. Control technologies,
classified as RACT (Reasonably Available Control Technology), BACT
(Best Available Control Technology), or LAER (Lowest Achievable
Emissions 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 database 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
emissions streams. We searched this database to determine whether it
contained any practices, processes, or control technologies for the
types of processes covered by the Secondary Lead Smelting MACT.
    Additionally, we requested information from facilities 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.

E. What other issues are we addressing in this proposal?

    In addition to the analyses described above, we also reviewed other
aspects of the MACT standards for possible revision as appropriate and
necessary. Based on this review we have identified aspects of the MACT
standards that we believe need revision.
    This includes proposing revisions to the startup, shutdown, and
malfunction (SSM) provisions of the MACT rule in order to ensure that
they are consistent with a recent court decision in Sierra Club v. EPA,
551 F.3d 1019 (DC Cir. 2008). In addition, we are proposing other
various minor changes with regards to editorial errors and other
revisions to promote the use of plain language. The analyses and
proposed decisions for these actions are presented in Section IV.E of
this preamble.

IV. Analyses Results and Proposed Decisions

    This section of the preamble provides the results of our RTR for
the Secondary Lead Smelting source category and our proposed decisions
concerning changes to the 1997 NESHAP.

A. What are the results of our analyses and proposed decisions
regarding unregulated emissions sources?

1. Organic HAP
    As discussed in Section III.A of this preamble, we evaluated
emissions limits for organic HAP for reverberatory furnaces not
collocated with blast furnaces, rotary furnaces, and electric furnaces.
Section 112(d)(3)(B) of the CAA requires that the MACT standards for
existing sources be at least as stringent as the average emissions
limitation achieved by the best performing five sources (for which the
Administrator has or could reasonably obtain emissions information) in
a category with fewer than 30 sources. The Secondary Lead Smelting
source category consists of fewer than 30 sources. Where, as here,
there are less than 30 sources, we base the MACT floor limit on the