E.O. 12866 Secondary Aluminum Proposal 2060-AQ40 12-30-11

6560-50-P

ENVIRONMENTAL PROTECTION

40 CFR Part 63

[EPA-HQ-OAR-2010-0544; FRL-???]

RIN 2060-AQ40

National Emissions Standards for Hazardous Air Pollutants: Secondary
Aluminum Production

AGENCY: Environmental Protection Agency (EPA)

ACTION: Proposed rule.

SUMMARY: The EPA is proposing amendments to the national emissions
standards for hazardous air pollutants for Secondary Aluminum Production
to address the results of the residual risk and technology review that
the EPA is required to conduct by the Clean Air Act. In addition, the
EPA is proposing amendments to correct and clarify rule requirements and
provisions. These proposed amendments would:

Add work practice standards for periods of startup and shutdown for some
processes;

Add a definition of affirmative defense;

Add a requirement to report performance testing through the Electronic
Reporting Tool (ERT);

Add rule provisions allowing owners and operators to change furnaces
designations;

Add rule requirements regarding testing of uncontrolled furnaces;

Add rule requirements for testing hydrogen fluoride in addition to
hydrogen chloride in furnaces that use fluorine-containing fluxes;

Add operating requirements such as monitoring of lime injection rates;
and

Make technical corrections and clarifications to the applicability,
definitions, operating, monitoring, and performance testing
requirements.

DATES: Comments must be received on or before [INSERT THE DATE 45 DAYS
AFTER THE DATE OF PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL
REGISTER]. 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 [INSERT THE DATE 30 DAYS AFTER THE DATE OF
PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL REGISTER].

Public Hearing. If anyone contacts the EPA requesting to speak at a
public hearing by [INSERT THE DATE 10 DAYS AFTER THE DATE OF PUBLICATION
IN THE FEDERAL REGISTER], a public hearing will be held on [INSERT THE
DATE 15 DAYS AFTER THE DATE OF PUBLICATION IN THE FEDERAL REGISTER].

ADDRESSES: Submit your comments, identified by Docket ID Number
EPA-HQ-OAR-2010-0544, by one of the following methods:

http://www.regulations.gov: Follow the on-line instructions for
submitting comments.

Email<EMAIL_ADDRESS>Attention Docket ID Number
EPA-HQ-OAR-2010-0544.

Fax:<PHONE_NUMBER>, Attention Docket ID Number EPA-HQ-OAR-2010-0544.

Mail: U.S. Postal Service, send comments to: EPA Docket Center, EPA West
(Air Docket), Attention Docket ID Number EPA-HQ-OAR-2010-0544, 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-2010-0544. 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-2010-0544. The 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 email. The http://www.regulations.gov
website is an “anonymous access” system, which means the EPA will
not know your identity or contact information unless you provide it in
the body of your comment. If you send an email comment directly to the
EPA without going through http://www.regulations.gov, your email address
will be automatically captured and included as part of the comment that
is placed in the public docket and made available on the Internet. If
you submit an electronic comment, the EPA recommends that you include
your name and other contact information in the body of your comment and
with any disk or CD-ROM you submit. If the EPA cannot read your comment
due to technical difficulties and cannot contact you for clarification,
the EPA may not be able to consider your comment. Electronic files
should avoid the use of special characters, any form of encryption, and
be free of any defects or viruses. For additional information about the
EPA’s public docket, visit the EPA Docket Center homepage at
http://www.epa.gov/epahome/dockets.htm.

Docket. The EPA has established a docket for this rulemaking under
Docket ID Number EPA-HQ-OAR-2010-0544. All documents in the docket are
listed in the http:// HYPERLINK "http://www.regulations.gov"
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 10:00 a.m.
on [INSERT THE DATE 15 DAYS AFTER THE DATE OF PUBLICATION OF THIS
PROPOSED RULE IN THE FEDERAL REGISTER] and will be held at the 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 Ms. Rochelle Boyd, 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 email
address<EMAIL_ADDRESS>For specific information regarding the
risk modeling methodology, contact Dr. Michael Stewart, Office of Air
Quality Planning and Standards, Health and Environmental Impacts
Division, Air Toxics Assessment Group (C504–06), U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711; telephone number:
(919) 541–7524; fax number: (919) 541–0840; and email address:
<EMAIL_ADDRESS>For information about the applicability of the
national emission standards for hazardous air pollutants (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

NESHAP for:	OECA Contact1	OAQPS Contact2

Secondary Aluminum Production	Scott Throwe,<PHONE_NUMBER>
<EMAIL_ADDRESS>Rochelle Boyd,

(919) 541-1390<EMAIL_ADDRESS>
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, for ease of reading of this preamble and
for reference purposes, the following terms and acronyms are defined
here:

ACGIH	American Conference of Government Industrial Hygienists

ADAF	age-dependent adjustment factors

AEGL	acute exposure guideline levels

AERMOD	air dispersion model used by the HEM-3 model

AMOS	ample margin of safety

ANPRM	advance notice of proposed rulemaking

ATSDR	Agency for Toxic Substances and Disease Registry

BACT	best available control technology

CAA	Clean Air Act

CBI	confidential business information

CFR	Code of Federal Regulations

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

HCl	hydrogen chloride

HEM-3	Human Exposure Model, Version 3

HF	hydrogen fluoride

HHRAP	human health risk assessment protocols

HI	hazard index

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/m3	milligrams per cubic meter

MIR	maximum individual risk

MRL	minimum risk level

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

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

ppmv	parts per million by volume

RACT	reasonably available control technology

RBLC	RACT/BACT/LAER Clearinghouse

REL	reference exposure level

RFA	Regulatory Flexibility Act

RfC	reference concentration

RfD	reference dose

RIA	regulatory impact analysis

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

UBC	used beverage containers

UF	uncertainty factor

µg/m3	microgram per cubic meter

UMRA	Unfunded Mandates Reform Act

UPL	upper predictive limit

URE	unit risk estimate

VOC	volatile organic compounds

VOHAP	volatile organic hazardous air pollutants

WHO	World Health Organization

WWW	worldwide web

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

  TOC \n \h \z \t "_Level 2-GHG Preamble,2,_Level 1-GHG Preamble,1"
HYPERLINK \l "_Toc311142794"  I. General Information

  HYPERLINK \l "_Toc311142795"  A. What is the statutory authority for
this action?

  HYPERLINK \l "_Toc311142796"  B. Does this action apply to me?

  HYPERLINK \l "_Toc311142797"  C. Where can I get a copy of this
document and other related information?

  HYPERLINK \l "_Toc311142798"  D. What should I consider as I prepare
my comments for the EPA?

  HYPERLINK \l "_Toc311142799"  II. Background

  HYPERLINK \l "_Toc311142800"  A. What is this source category and how
did the MACT standard regulate its HAP emissions?

  HYPERLINK \l "_Toc311142801"  B. What data collection activities were
conducted to support this action?

  HYPERLINK \l "_Toc311142802"  III. Analyses Performed

  HYPERLINK \l "_Toc311142803"  A. How did we estimate risks posed by
the source category?

  HYPERLINK \l "_Toc311142804"  B. How did we consider the risk results
in making decisions for this proposal?

  HYPERLINK \l "_Toc311142805"  C. How did we perform the technology
review?

  HYPERLINK \l "_Toc311142806"  D. What other issues are we addressing
in this proposal?

  HYPERLINK \l "_Toc311142807"  IV. Analytical Results and Proposed
Decisions

  HYPERLINK \l "_Toc311142808"  A. What are the results of the risk
assessments?

  HYPERLINK \l "_Toc311142809"  B. What are our proposed decisions
regarding risk acceptability and ample margin of safety?

  HYPERLINK \l "_Toc311142810"  C. What are the results and proposed
decisions based on our technology review?

  HYPERLINK \l "_Toc311142811"  D. What other actions are we proposing?

  HYPERLINK \l "_Toc311142812"  E. Compliance dates

  HYPERLINK \l "_Toc311142813"  V. Summary of Cost, Environmental, and
Economic Impacts

  HYPERLINK \l "_Toc311142814"  A. What are the affected sources?

  HYPERLINK \l "_Toc311142815"  B. What are the air quality impacts?

  HYPERLINK \l "_Toc311142816"  C. What are the cost impacts?

  HYPERLINK \l "_Toc311142817"  D. What are the economic impacts?

  HYPERLINK \l "_Toc311142818"  E. What are the benefits?

  HYPERLINK \l "_Toc311142819"  VI. Request for Comments

  HYPERLINK \l "_Toc311142820"  VII. Submitting Data Corrections

  HYPERLINK \l "_Toc311142821"  VIII. Statutory and Executive Order
Reviews

  HYPERLINK \l "_Toc311142822"  A. Executive Order 12866: Regulatory
Planning and Review and Executive Order 13563: Improving Regulation and
Regulatory Review .

  HYPERLINK \l "_Toc311142823"  B. Paperwork Reduction Act.

  HYPERLINK \l "_Toc311142824"  C. Regulatory Flexibility Act.

  HYPERLINK \l "_Toc311142825"  D. Unfunded Mandates Reform Act.

  HYPERLINK \l "_Toc311142826"  E. Executive Order 13132: Federalism.

  HYPERLINK \l "_Toc311142827"  F. Executive Order 13175: Consultation
and Coordination with Indian Tribal Governments.

  HYPERLINK \l "_Toc311142828"  G. Executive Order 13045: Protection of
Children from Environmental Health Risks and Safety Risks.

  HYPERLINK \l "_Toc311142829"  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 the EPA has identified categories of
sources emitting one or more of the HAP listed in section 112(b) of the
CAA, section 112(d) of the CAA calls for us to promulgate national
emission standards for hazardous air pollutants (NESHAP) for those
sources. “Major sources” are those that emit or have the potential
to emit (PTE) 10 tons per year (tpy) or more of a single HAP or 25 tpy
or more of any combination of HAP. For major sources, these
technology-based standards must reflect the maximum degree of emission
reductions of HAP achievable (after considering cost, energy
requirements and non-air quality health and environmental impacts) and
are commonly referred to as maximum achievable control technology (MACT)
standards.

MACT standards must require the maximum degree of emissions reduction
achievable through the application of measures, processes, methods,
systems or techniques including, but not limited to, measures which (1)
reduce the volume of or eliminate emissions of pollutants through
process changes, substitution of materials or other modifications, (2)
enclose systems or processes to eliminate emissions, (3) capture or
treat pollutants when released from a process, stack, storage or
fugitive emissions point, (4) are design, equipment, work practice or
operational standards (including requirements for operator training or
certification) or (5) are a combination of the above. CAA section
112(d)(2)(A)-(E). The MACT standard may take the form of a design,
equipment, work practice or operational standard where the EPA first
determines that either (1) a pollutant cannot be emitted through a
conveyance designed and constructed to emit or capture the pollutant or
that any requirement for, or use of, such a conveyance would be
inconsistent with law, or (2) the application of measurement methodology
to a particular class of sources is not practicable due to technological
and economic limitations. CAA sections 112(h)(1)-(2).

The MACT “floor” is the minimum control level allowed for MACT
standards promulgated under CAA section 112(d)(3) and may not be based
on cost considerations. For new sources, the MACT floor cannot be less
stringent than the emission control that is achieved in practice by the
best-controlled similar source. The MACT floors for existing sources can
be less stringent than floors for new sources, but they cannot be less
stringent than the average emission limitation achieved by the
best-performing 12 percent of existing sources in the category or
subcategory (or the best-performing five sources for categories or
subcategories with fewer than 30 sources). In developing MACT standards,
we must also consider control options that are more stringent than the
floor. We may establish standards more stringent than the floor based on
consideration of the cost of achieving the emissions reductions and any
non-air quality health and environmental impacts and energy
requirements.

Under CAA section 112(d)(6), the EPA is then required to review these
technology-based standards and to revise them “as necessary (taking
into account developments in practices, processes, and control
technologies)” no less frequently than every 8 years. In conducting
this review, the EPA is not obliged to completely recalculate the prior
MACT determination. NRDC v. EPA, 529 F.3d 1077, 1084 (D.C. 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 the EPA prepare a Report to Congress discussing
(among other things) methods of calculating risk posed (or potentially
posed) by sources after implementation of the MACT standards, the public
health significance of those risks, and the EPA’s recommendations as
to legislation regarding such remaining risk. The 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 the EPA’s obligation under CAA
section 112(f)(2) to analyze and address residual risk.

CAA section 112(f)(2) requires us to determine, for source categories
subject to certain MACT standards, whether the emissions standards
provide an ample margin of safety to protect public health. If the MACT
standards for HAP “classified as a known, probable, or possible human
carcinogen do not reduce lifetime excess cancer risks to the individual
most exposed to emissions from a source in the category or subcategory
to less than one in one million,” the EPA must promulgate residual
risk standards for the source category (or subcategory), as necessary,
to provide an ample margin of safety to protect public health. In doing
so, the EPA may adopt standards equal to existing MACT standards if the
EPA determines that the existing standards are sufficiently protective.
NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008). (“If EPA determines
that the existing technology-based standards provide an “ample margin
of safety,” then the agency is free to readopt those standards during
the residual risk rulemaking.”) The EPA must also adopt more stringent
standards, if necessary, to prevent an adverse environmental effect but
must consider cost, energy, safety and other relevant factors in doing
so.

Section 112(f)(2) of the CAA expressly preserves our use of a two-step
process for developing standards to address any residual risk and our
interpretation of “ample margin of safety” developed in the National
Emission Standards for Hazardous Air Pollutants: Benzene Emissions from
Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage
Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery Plants
(Benzene NESHAP) (54 FR 38044, September 14, 1989). The first step in
this process is the determination of acceptable risk. The second step
provides for an ample margin of safety to protect public health, which
is the level at which the standards are set (unless a more stringent
standard is 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 the EPA’s interpretation
set out in the Benzene NESHAP, and the United States Court of Appeals
for the District of Columbia Circuit in NRDC v. EPA, concluded that the
EPA’s interpretation of subsection 112(f)(2) is a reasonable one. See
NRDC v. EPA, 529 F.3d 1077 1083 (D.C. Cir. 2008) (“[S]ubsection
112(f)(2)(B) expressly incorporates the 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 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, 54 FR at 38044-38045, we stated as an overall
objective: In protecting public health with an ample margin of safety
under section 112, EPA strives 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 plant would have if he or
she were exposed to the maximum pollutant concentrations for 70 years.

The agency stated that, “[t]he EPA also considers incidence (the
number of persons estimated to suffer cancer or other serious health
effects as a result of exposure to a pollutant) to be an important
measure of the health risk to the exposed population. Incidence measures
the extent of health risk to the exposed population as a whole, by
providing an estimate of the occurrence of cancer or other serious
health effects in the exposed population.” 54 FR 38045. The agency
went on to conclude that “estimated incidence would be weighed along
with other health risk information in judging acceptability.” 54 FR at
38046. As explained more fully in our Residual Risk Report to Congress,
the EPA does not define “rigid line[s] of acceptability,” but
considers rather broad objectives to be weighed with a series of other
health measures and factors (EPA–453/R–99–001, p. ES–11). The
determination of what represents an “acceptable” risk is based on a
judgment of “what risks are acceptable in the world in which we
live” (Residual Risk Report to Congress, p. 178, quoting the Vinyl
Chloride decision at 824 F.2d 1165) recognizing that our world is not
risk-free.

In the Benzene NESHAP, we stated that “EPA will generally presume that
if the risk to [the maximum exposed] individual is no higher than
approximately 1 in 10 thousand, that risk level is considered
acceptable.” 54 FR at 38045. We discussed the maximum individual
lifetime cancer risk (or maximum individual risk (MIR)) 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: “[i]n
establishing a presumption for MIR, 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 km [kilometer]
exposure radius around facilities, the science policy assumptions and
estimation uncertainties associated with the risk measures, weight of
the scientific evidence for human health effects, other quantified or
unquantified health effects, effects due to co-location of facilities,
and co-emission of pollutants.” Id.

In some cases, these health measures and factors taken together may
provide a more realistic description of the magnitude of risk in the
exposed population than that provided by maximum individual lifetime
cancer risk alone. As explained in the Benzene NESHAP, “[e]ven though
the risks judged ’acceptable‘ by the 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 * * *.” 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.” 54 FR at 38046.

As discussed above, we apply a two-step process for developing standards
to address residual risk. In the first step, the EPA determines whether
risks are acceptable. This determination “considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR) of
approximately 1-in-10 thousand [i.e., 100 in 1 million].” 54 FR at
38045. In the second step of the process, the 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.

In past residual risk determinations, the EPA presented a number of
human health risk metrics associated with emissions from the category
under review, including: the MIR; the numbers of persons in various risk
ranges; cancer incidence; the maximum noncancer hazard index (HI); and
the maximum acute noncancer hazard. In estimating risks, the EPA
considered source categories under review that are located near each
other and that affect the same population. The EPA estimates risk based
on the actual emissions from the source category under review as well as
based on the emissions allowed pursuant to the source category MACT
standard. The EPA also discussed and considered risk estimation
uncertainties. The EPA is providing this same type of information in
support of these actions.

The agency acknowledges that the Benzene NESHAP provides flexibility
regarding what factors the EPA might consider in making our
determinations and how they might be weighed for each source category.
In responding to comment on our policy under the Benzene NESHAP, the EPA
explained that: “[t]he policy chosen by the Administrator permits
consideration of multiple measures of health risk. Not only can the MIR
figure be considered, but also incidence, the presence of noncancer
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.

For example, the level of the MIR is only one factor to be weighed in
determining acceptability of risks. The Benzene NESHAP explains “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.” 54 FR at 38045. Similarly, with regard to the
ample margin of safety analysis, the Benzene NESHAP states 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.” 54 FR at 38061.

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. The EPA defined the Secondary
Aluminum source category in 1992 as any establishment using clean
charge, aluminum scrap, or dross from aluminum production, as the raw
material and performing one or more of the following processes: scrap
shredding, scrap drying/delacquering/decoating, thermal chip drying,
furnace operations (i.e., melting, holding, sweating, refining, fluxing,
or alloying), recovery of aluminum from dross, in-line fluxing, or dross
cooling.

Table 2. NESHAP and Industrial Source Categories Affected By This
Proposed Action

Source Category

NESHAP

NAICS code1	MACT code2

Secondary Aluminum Production

Primary aluminum production facilities

Aluminum sheet, plate, and foil manufacturing facilities

Aluminum extruded product manufacturing facilities

Other aluminum rolling and drawing facilities

Aluminum die casting facilities

Aluminum foundry facilities	Secondary Aluminum Production

	331314

331312

331315

331316

331319

331521

331524	0044

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 including the residual risk and technology review
(RTR) and 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 the EPA?

Submitting CBI. Do not submit information containing CBI to the EPA
through http://www.regulations.gov or email. 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 the EPA, mark the outside of the disk
or CD ROM as CBI and then identify electronically within the disk or CD
ROM the specific information that is claimed as CBI. In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information claimed
as CBI must be submitted for inclusion in the public docket. If you
submit a CD ROM or disk that does not contain CBI, mark the outside of
the disk or CD ROM clearly that it does not contain CBI. Information not
marked as CBI will be included in the public docket and the EPA’s
electronic public docket without prior notice. Information marked as CBI
will not be disclosed except in accordance with procedures set forth in
40 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-2010-0544.

II. Background

A. What is this source category and how did the MACT standard regulate
its HAP emissions?

The Secondary Aluminum Production source category includes facilities
that produce aluminum from scrap aluminum material and consists of the
following operations: (1) Preprocessing of scrap aluminum, including
size reduction and removal of oils, coatings, and other contaminants;
(2) Furnace operations including melting, in-furnace refining, fluxing,
and tapping; (3) Additional refining, by means of in-line fluxing; and
(4) Cooling of dross. The following sections include descriptions of the
affected sources in the secondary aluminum production source category,
the origin of HAP emissions from these affected sources, and factors
affecting the emissions.

Scrap aluminum is often preprocessed prior to melting. Preprocessing
steps may include shredding to reduce the size of aluminum scrap; drying
of oily scrap such as machine turnings and borings; and/or heating in a
scrap dryer, delacquering kiln or decoating kiln to remove coatings or
other contaminants that may be present on the scrap. Heating of high
iron content scrap in a sweat furnace to reclaim the aluminum content is
also a preprocessing operation.

Crushing, shredding and grinding operations are used to reduce the size
of scrap aluminum. Particulate matter (PM) and HAP metals are generated
as dust from coatings and other contaminants contained in the scrap
aluminum as they are processed.

A chip dryer is used to evaporate oil and/or moisture from uncoated
aluminum chips and borings. Chip dryers typically operate at
temperatures ranging between 150°C to 400°C (300°F to 750°F). An
uncontrolled chip dryer may emit dioxins and furans (D/F) and total
hydrocarbons (THC), of which some fraction is organic HAP.

Painted and/or coated materials are processed in a scrap
dryer/delacquering kiln/decoating kiln to remove coatings and other
contaminants that may be present in the scrap prior to melting.
Coatings, oils, grease, and lubricants represent up to 20 percent of the
total weight of these materials. Organic HAP, D/F, and inorganic HAPs
including particulate metal HAP are emitted during the
drying/delacquering/decoating process.

Used beverage containers (UBC) comprise a major portion of the recycled
aluminum scrap used as feedstock by the industry. In scrap
drying/delacquering/decoating operations, UBC and other post-consumer,
coated products (e.g., aluminum siding) are heated to an exit
temperature of up to 540°C (1,000°F) to volatilize and remove various
organic contaminants such as paints, oils, lacquers, rubber, and plastic
laminates prior to melting. An uncontrolled scrap dryer/delacquering
kiln/decoating kiln emits PM (of which some fraction is particulate
metal HAP), HCl, THC (of which some fraction is organic HAP), and D/F.

A sweat furnace is typically used to reclaim (or ‘‘sweat’’) the
aluminum from scrap with high levels of iron. These furnaces operate in
batch mode at a temperature that is high enough to melt the aluminum but
not high enough to melt the iron. The aluminum melts and flows out of
the furnace while the iron remains in the furnace in solid form. The
molten aluminum can be cast into sows, ingots, or T-bars that are used
as feedstock for aluminum melting and refining furnaces. Alternately,
molten aluminum can be fed directly to a melting or refining furnace. An
uncontrolled sweat furnace emits D/F.

Process (i.e. melting, holding or refining) furnaces are
refractory-lined metal vessels heated by an oil or gas burner to achieve
a metal temperature of about 760°C (1,400°F). The melting process
begins with the charging of scrap into the furnace. A gaseous
(typically, chlorine) or salt flux may be added to remove impurities and
reduce aluminum oxidation. Once molten, the chemistry of the bath is
adjusted by adding selected scrap or alloying agents, such as silicon.
Salt and other fluxes contain chloride and fluoride compounds that may
be released when introduced to the bath. HCl may also be released when
chlorine-containing contaminants (such as polyvinyl chloride coatings)
present in some types of scrap are introduced to the bath. Argon and
nitrogen fluxes are not reactive and do not produce HAPs. In a sidewell
melting furnace, fluxing is performed in the sidewell and fluxing
emissions from the sidewell are controlled. In this type of furnace,
fluxing is not typically done in the hearth and hearth emissions (which
include products of combustion from the oil and gas fired furnaces) are
typically uncontrolled.

Process furnaces may process contaminated scrap which can result in HAP
emissions. In addition, fluxing agents may contain HAPs, some fraction
of which is emitted from the furnace. Process furnaces are significant
sources of HAP emissions in the secondary aluminum industry. An
uncontrolled melting furnace which processes contaminated scrap and uses
reactive fluxes emits PM (of which some fraction is particulate metal
HAP), HCl, and D/F.

Process furnaces are divided into group 1 and group 2 furnaces. Group 1
furnaces are unrestricted in the type of scrap they process and the type
of fluxes they can use. Group 2 furnaces process only clean charge and
conduct no reactive fluxing.

Dross-only furnaces are furnaces dedicated to reclamation of
aluminum from drosses formed during the melting/ holding/alloying
operations carried out in other furnaces. Exposure to the atmosphere
causes the molten aluminum to oxidize, and the flotation of the
impurities to the surface along with any salt flux creates
‘‘dross.’’ Prior to tapping, the dross is periodically skimmed
from the surface of the aluminum bath and cooled. Dross-only furnaces
are typically rotary barrel furnaces (also known as salt furnaces). A
dross-only furnace without controls emits PM (of which some fraction is
particulate metal HAP).

Rotary dross coolers are devices used to cool dross in a rotating,
water-cooled drum. A rotary dross cooler without controls emits PM (of
which some fraction is particulate metal HAP).

In-line fluxers are devices used for aluminum refining, including
degassing, outside the furnace. The process involves the injection of
chlorine, argon, nitrogen or other gases to achieve the desired metal
purity. Argon and nitrogen are not reactive and do not produce HAPs.
In-line fluxers are found primarily at facilities that manufacture very
high quality aluminum or in facilities with no other means of degassing.
An in-line fluxer operating without emission controls emits HCl and PM.

The Secondary Aluminum Production NESHAP was promulgated on March 23,
2000, (65 FR 15690) and codified as 40 CFR part 63, subpart RRR. The
rule was amended at 67 FR 79807, December, 30, 2002; 69 FR 53980,
September 3, 2004; 70 FR 57513, October 3, 2005 and 70 FR 75320,
December 19, 2005. The existing subpart RRR NESHAP regulates HAP
emissions from secondary aluminum production facilities that are major
sources of HAP that operate aluminum scrap shredders, thermal chip
dryers, scrap dryers/delacquering kilns/decoating kilns, group 1
furnaces, group 2 furnaces, sweat furnaces, dross only furnaces, rotary
dross coolers, and secondary aluminum processing units (SAPUs). The
SAPUs include group 1 furnaces and in-line fluxers. The subpart RRR
NESHAP regulates HAP emissions from secondary aluminum production
facilities that are area sources of HAP only with respect to emissions
of dioxins/furans (D/F) from thermal chip dryers, scrap
dryers/delacquering kilns/decoating kilns, group 1 furnaces, sweat
furnaces, and SAPUs.

The secondary aluminum industry consists of approximately 161 secondary
aluminum production facilities, of which the EPA estimates 53 to be
major sources of HAP. Several of the secondary aluminum facilities are
co-located with primary aluminum, coil coating, and possibly other
source category facilities. Natural gas boilers or process heaters may
also be co-located at a few secondary aluminum facilities.

The HAP emitted by these facilities are metals, organic HAP, D/F,
hydrogen chloride (HCl), and hydrogen fluoride (HF).  The standards
promulgated in 2000 established emission limits for particulate matter
(PM) as a surrogate for metal HAP, total hydrocarbons (THC) as a
surrogate for organic HAP other than D/F, D/F expressed as toxicity
equivalents, and HCl as a surrogate for acid gases including HF,
chlorine and fluorine. HAP are emitted from the following affected
sources: aluminum scrap shredders (subject to PM standards), thermal
chip dryers (subject to standards for THC and D/F), scrap
dryers/delacquering kilns/decoating kilns (subject to standards for PM,
D/F, HCl and THC), sweat furnaces (subject to D/F standards), dross-only
furnaces (subject to PM standards), rotary dross coolers (subject to PM
standards), group 1 furnaces (subject to standards for PM, HCl and D/F),
and in-line fluxers (subject to standards for PM and HCl). Group 2
furnaces and certain in-line fluxers are subject to work practice
standards. Table 3 provides a summary of the current MACT emissions
limits for existing and new sources under the 2000 NESAHP and the 2005
amendments.

Table 3. Emission Standards for New and Existing Affected Sources for
the Secondary Aluminum Source Category

Affected source/ Emission unit	Pollutant	Limit	Units

All new and existing affected sources and emission units that are
controlled with a PM add-on control device and that choose to monitor
with a Continuous Opacity Monitor (COM) and all new and existing
aluminum scrap shredders that choose to monitor with a COM or to monitor
visible emissions	Opacity	10	Percent

New and existing aluminum scrap shredder	PM	0.01	gr/dscf

New and existing thermal chip dryer	THC

D/Fa	0.80

2.50	lb/ton of feed

µg TEQ/Mg of feed

New and existing scrap dryer/delacquering kiln/decoating kiln

                            Or	PM

HCl

THC

D/Fa	0.08

0.80

0.06

0.25	lb/ton of feed

lb/ton of feed

lb/ton of feed

µg TEQ/Mg of feed

Alternative limits if afterburner has a design residence time of at
least 1 second and operates at a temperature of at least 1400 °F	PM

HCl

THC

D/Fa	0.30

1.50

0.20

5.0	lb/ton of feed

lb/ton of feed

lb/ton of feed

µg TEQ/Mg of feed

New and existing sweat furnace	D/Fa	0.80	ng TEQ/dscm @ 11% O2b

New and existing dross-only furnace	PM	0.30	lb/ton of feed

New and existing in-line fluxerc 	HCl

PM	0.04

0.01	lb/ton of feed

lb/ton of feed

New and existing in-line fluxer with no reactive fluxing

No limit	Work practice: no reactive fluxing

New and existing rotary dross cooler	PM	0.04	gr/dscf

New and existing clean furnace (Group 2)

No limit	Work practices: clean charge only and no reactive fluxing

New and existing group 1 melting/holding furnace (processing only clean
charge)c 	PM

HCl	0.80

0.40

or

10	lb/ton of feed

lb/ton of feed

percent of the HCl upstream of an add-on control device

New and existing group 1 furnacec 	PM

HCl

	0.40

0.40

or

10	lb/ton of feed

lb/ton of feed

percent of the HCl upstream of an add-on control device

	D/Fa	15.0	µg TEQ/Mg of feed

New and existing group 1 furnacec with clean charge only	PM

HCl	0.40

0.40

or	lb/ton of feed

lb/ton of feed

10	percent of the HCl upstream of an add-on control device

	D/Fa	No Limit	Clean charge only

New and existing secondary aluminum processing unita,d (consists of all
existing group 1 furnaces and existing in-line flux boxes at the
facility, or all simultaneously constructed new group 1 furnaces and new
in-line fluxers)	PMe

	HClf

a D/F limit applies to a unit at a major or area source.

b Sweat furnaces equipped with afterburners meeting the specifications
of §63.1505(f)(1) are not required to conduct a performance test.

c These limits are also used to calculate the limits applicable to
secondary aluminum processing units.

d Equation definitions: LiPM = the PM emission limit for individual
emission unit i in the secondary aluminum processing unit [kg/Mg
(lb/ton) of feed]; Ti = the feed rate for individual emission unit i in
the secondary aluminum processing unit; LtPM = the overall PM emission
limit for the secondary aluminum processing unit [kg/Mg (lb-ton) of
feed]; LiHCl = the HCl emission limit for individual emission unit i in
the secondary aluminum processing unit [kg/Mg (lb/ton) of feed]; LtHCl =
the overall HCl emission limit for the secondary aluminum processing
unit [kg/Mg (lb/ton) of feed]; LiD/F = the D/F emission limit for
individual emission unit i [µg TEQ/Mg (gr TEQ/ton) of feed]; LtD/F =
the overall D/F emission limit for the secondary aluminum processing
unit [µg TEQ/Mg (gr TEQ/ton) of feed]; n = the number of units in the
secondary aluminum processing unit.

e In-line fluxers using no reactive flux materials cannot be included in
this calculation since they are not subject to the PM limit.

f In-line fluxers using no reactive flux materials cannot be included in
this calculation since they are not subject to the HCl limit.

g Clean charge furnaces cannot be included in this calculation since
they are not subject to the D/F limit.

Control devices currently in use to reduce emissions from affected
sources subject to the subpart RRR NESHAP include fabric filters for
control of PM from aluminum scrap shredders; afterburners for control of
THC and D/F from thermal chip dryers; afterburners plus lime-injected
fabric filters for control of PM, HCl, THC, and D/F from scrap
dryers/delacquering kilns/decoating kilns; afterburners for control of
D/F from sweat furnaces; fabric filters for control of PM from
dross-only furnaces and rotary dross coolers; lime-injected fabric
filters for control of PM and HCl from in-line fluxers; and
lime-injected fabric filters for control of PM, HCl and D/F from group 1
furnaces. All affected sources with add-on controls are also subject to
design requirements and operating limits to limit fugitive emissions.

Compliance with the emission limits in the current rule is demonstrated
by an initial performance test for each affected source. Repeat
performance tests are required every 5 years. Area sources are only
subject to one-time performance tests for D/F. After the compliance
tests, facilities are required to monitor various control parameters or
conduct other types of monitoring to ensure continuous compliance with
the MACT standards. Owners or operators of sweat furnaces that operate
an afterburner that meets temperature and residence time requirements
are not required to conduct performance tests.

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

For the Secondary Aluminum Production source category, we compiled a
dataset from two primary sources: (1) an all-company information
collection request (ICR) sent to companies in February 2011, and (2) a
nine-company testing ICR, sent in May 2010.

Responses to the all-company ICR contained data on stack release
characteristics such as height, volumetric flow rate, temperature, and
location (latitude/longitude) coordinates. Responses to the all-company
ICR also contained data on maximum production capacity and actual
production in tpy and testing results for pollutants regulated under
subpart RRR.

As mentioned above, the pollutants regulated under subpart RRR are PM,
HCl, THC and D/F. PM is a surrogate for metal HAP and THC is a surrogate
for organic HAP. Since subpart RRR compliance testing is performed for
the surrogates PM and THC, there are limited test data available for
HAP-speciated metal and organic HAP emissions. Therefore, responses to
the nine-company testing ICR were used to extrapolate the PM and THC
testing results reported in the all-company ICR to specific metal and
organic HAP emissions. In the nine-company testing ICR, companies were
asked to provide speciated metal HAP concentrations (e.g. arsenic,
cadmium, cobalt, lead, nickel, etc.) in the particulate collected by
fabric filters. These data were then used to estimate speciated metal
HAP emissions, based on the PM emissions reported in the all-company
ICR. For example, if a response to the all-company ICR indicated a
particular piece of equipment at a specific secondary aluminum facility
had 10 tpy of PM emissions, and based on an analysis of the results of
the nine-company testing ICR the EPA determined that the cobalt
concentration in the fabric filter particulate matter catch was 20
parts-per-million (ppm), the estimated emissions of cobalt would be
0.0002 tpy. In the nine-company testing ICR, companies were also
required to conduct speciated organic HAP and THC emission testing for
the two types of equipment that have THC limits under subpart RRR, scrap
dryer/delacquering/decoating kilns and thermal chip dryers. The
speciated organic HAPs for which data were provided included volatile
HAPs (e.g., benzene, chloroprene, toluene, etc.) and semi-volatile HAPs
(anthracene, chrysene, naphthalene, etc.).

Using the reported amount of charge or production for the most recent
year and the reported test results (in lb per ton of charge) from the
all-company ICR, emissions were calculated. Where test results from the
all-company ICR responses were expressed in terms of PM and THC
surrogates, emissions were converted to speciated metal and organic HAP
emissions using the nine-company test results, as described above.
Allowable and actual emissions were calculated for each piece of
equipment. The derivation of allowable emissions estimates is described
in Section III of this preamble.

The emissions data, calculations and risk assessment inputs for the
Secondary Aluminum Production source category are described further in
the memorandum Draft Development of the RTR Risk Modeling Dataset for
the Secondary Aluminum Production Source Category which is available in
the docket for this proposed rulemaking.

III. Analyses Performed

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

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

	The EPA conducted risk assessments that provide estimates of the MIR
posed by the HAP emissions for each source in the category, the HI for
chronic exposures to HAP with the potential to cause noncancer health
effects, and the hazard quotient (HQ) for acute exposures to HAP with
the potential to cause noncancer health effects. The assessments also
provided estimates of the distribution of cancer risks within the
exposed populations, cancer incidence and an evaluation of the potential
for adverse environmental effects for the source category. The risk
assessments consisted of seven primary steps, as discussed below. 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 Aluminum Production
Source Category. The methods used to assess risks (as described in the
six primary steps below) are consistent with those peer-reviewed by a
panel of the EPA’s Science Advisory Board (SAB) in 2009 and described
in their peer review report issued in 2010; they are also consistent
with the key recommendations contained in that report.

1. Establishing the nature and magnitude of actual emissions and
identifying the emissions release characteristics

	As discussed in Section II.B. of this preamble, we used a dataset based
on the estimated actual and allowable emissions as the basis for the
risk assessment. This dataset was based on responses to an Information
Collection Request (ICR) sent to approximately 425 facilities
potentially subject to the subpart RRR NESHAP. Approximately 161 sources
subject to the NESHAP responded, approximately 166 facilities confirmed
that they were not subject to the NESHAP and no responses were received
to approximately 51 ICRs. In addition to these responses, as described
in section II.B, an earlier ICR was sent to 9 companies requiring them
to provide speciated metal and organic HAP concentrations for purposes
of calculating speciated HAP emissions based on reported emissions of
the surrogate pollutants, THC and PM. As part of our quality assurance
(QA) process, we checked the coordinates of every facility in the
dataset using tools such as Google Earth. We corrected coordinates that
were found to be incorrect. We also performed QA of the emissions data
and release characteristics to identify outliers and then confirmed or
corrected the data.

2. Establishing the relationship between actual emissions and
MACT-allowable emissions levels

The available emissions data in the MACT dataset include estimates of
the mass of HAP actually emitted during the specified annual time
period. These “actual” emission levels are often lower than the
emission levels that a facility might be allowed to emit and still
comply with the MACT standards. The emissions level allowed to be
emitted by the MACT standards is referred to as the “MACT-allowable”
emissions level. This represents the highest emissions level that could
be emitted by the facility without violating the MACT standards.

We discussed the use of both MACT-allowable and actual emissions in the
final Coke Oven Batteries residual risk rule (70 FR 19998–19999, April
15, 2005) and in the proposed and final Hazardous Organic NESHAP
residual risk rules (71 FR 34428, June 14, 2006, and 71 FR 76609,
December 21, 2006, respectively). In those previous actions, we noted
that assessing the risks at the MACT-allowable level is inherently
reasonable since these risks reflect the maximum level sources could
emit and still comply with national emission standards. But we also
explained that it is reasonable to consider actual emissions, where such
data are available, in both steps of the risk analysis, in accordance
with the Benzene NESHAP. (54 FR 38044, September 14, 1989.)

As discussed above, allowable and actual emissions were calculated for
each piece of equipment. The estimates of actual emissions are described
in Section II of this preamble.

Allowable emissions for this source category were calculated by assuming
emissions were at the maximum level allowed by the MACT standard (i.e.,
we assume emissions would be emitted at a level equal to the MACT
emission limit). Nevertheless, we note that these are conservative
estimates of allowable emissions. It is unlikely that emissions would be
at the maximum limit at all times because sources cannot emit HAP at a
level that is exactly equal to the limit at all times and remain in
compliance with the standard due to day-to-day variability in process
operations and emissions. On average, facilities must emit at some level
below the MACT limit to ensure that they are always in compliance. The
derivation of actual and allowable emissions estimates are discussed in
more detail in the document Draft Development of the RTR Emissions
Dataset for the Secondary Aluminum Production Source Category which is
available in the docket for this proposed rulemaking.

3. Conducting dispersion modeling, determining inhalation exposures and
estimating individual and population inhalation risks

Both long-term and short-term inhalation exposure concentrations and
health risks from each facility in the source category were estimated
using the Human Exposure Model (HEM) (Community and Sector HEM–3
version 1.1.0). The HEM–3 performs three primary risk assessment
activities: (1) conducting dispersion modeling to estimate the
concentrations of HAP in ambient air, (2) estimating long-term and
short-term inhalation exposures to individuals residing within 50 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 the
EPA’s preferred models for assessing pollutant concentrations from
industrial facilities. 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 (1991) of hourly
surface and upper air observations for more than 158 meteorological
stations, selected to provide coverage of the United States and Puerto
Rico. A second library of United States Census Bureau census block
internal point locations and populations provides the basis of human
exposure calculations (Census, 2000). 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 the EPA for HAP and other toxic air
pollutants. These values are available at  HYPERLINK
"http://www.epa.gov/ttn/atw/toxsource/summary.html"
http://www.epa.gov/ttn/atw/toxsource/summary.html  and are discussed in
more detail later in this section.

In developing the risk assessment for chronic exposures, we used the
estimated annual average ambient air concentration of each of the HAP
emitted by each source for which we have emissions data in the source
category. The air concentrations at each nearby census block centroid
were used as a surrogate for the chronic inhalation exposure
concentration for all the people who reside in that census block. We
calculated the MIR for each facility as the cancer risk associated with
a continuous lifetime (24 hours per day, 7 days per week, and 52 weeks
per year for a 70-year period) exposure to the maximum concentration at
the centroid of an inhabited census block. 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. For residual risk assessments, we generally use URE values
from the EPA’s Integrated Risk Information System (IRIS). For
carcinogenic pollutants without the EPA IRIS values, we look to other
reputable sources of cancer dose-response values, often using California
EPA (CalEPA) URE values, where available. In cases where new,
scientifically credible dose-response values have been developed in a
manner consistent with the EPA guidelines and have undergone a peer
review process similar to that used by the EPA, we may use such
dose-response values in place of, or in addition to, other values, if
appropriate.

Incremental individual lifetime cancer risks associated with emissions
from the source category were estimated as the sum of the risks for each
of the carcinogenic HAP (including those classified as carcinogenic to
humans, likely to be carcinogenic to humans and suggestive evidence of
carcinogenic potential) emitted by the modeled source. Cancer incidence
and the distribution of individual cancer risks for the population
within 50 km of any source were also estimated for the source category
as part of these assessments by summing individual risks. A distance of
50 km is consistent with both the analysis supporting the 1989 Benzene
NESHAP (54 FR 38044) and the limitations of Gaussian dispersion models,
including AERMOD.

To assess risk of noncancer 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 for chronic exposures is the estimated
chronic exposure divided by the chronic reference level, which is either
the EPA reference concentration (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 from
the EPA’s IRIS database is not available, a value from the following
prioritized sources: (1) the agency for Toxic Substances and Disease
Registry Minimum Risk Level, which is defined as “an estimate of daily
human exposure to a substance that is likely to be without an
appreciable risk of adverse effects (other than cancer) over a specified
duration of exposure”; (2) the CalEPA Chronic Reference Exposure Level
(REL), which is defined as “the concentration level at or below which
no adverse health effects are anticipated for a specified exposure
duration;” or (3) as noted above, a scientifically credible
dose-response value that has been developed in a manner consistent with
the EPA guidelines and has undergone a peer review process similar to
that used by the EPA, in place of or in concert with other values.

Screening estimates of acute exposures and risks were also evaluated for
each of the HAP at the point of highest off-site exposure for each
facility (i.e., not just the census block centroids), assuming that a
person is located at this spot at a time when both the peak (hourly)
emission rates from each emission point at the facility and worst-case
dispersion conditions occur. The acute HQ is the estimated acute
exposure divided by the acute dose-response value. In each case, acute
HQ values were calculated using best available, short-term dose-response
values. These acute dose-response values, which are described below,
include the acute REL, acute exposure guideline levels (AEGL) and
emergency response planning guidelines (ERPG) for 1-hour exposure
durations. As discussed below, we used conservative assumptions for
emission rates, meteorology and exposure location for our acute
analysis.

As described in the CalEPA’s Air Toxics Hot Spots Program Risk
Assessment Guidelines, Part I, The Determination of Acute Reference
Exposure Levels for Airborne Toxicants, an acute REL value (http://
HYPERLINK "http://www.oehha.ca.gov/air/pdf/acuterel.pdf"
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.” Acute REL values are
based on the most sensitive, relevant, adverse health effect reported in
the medical and toxicological literature. Acute REL values are designed
to protect the most sensitive sub-populations (e.g., asthmatics) by the
inclusion of margins of safety. Since margins of safety are incorporated
to address data gaps and uncertainties, exceeding the acute REL does not
automatically indicate an adverse health impact.

AEGL values were derived in response to recommendations from the
National Research Council (NRC). As described in Standing Operating
Procedures (SOP) of the National Advisory Committee on Acute Exposure
Guideline Levels for Hazardous Substances (http:// HYPERLINK
"http://www.epa.gov/opptintr/aegl/pubs/" www.epa.gov/opptintr/aegl/pubs/
sop.pdf), “the NRC’s previous name for acute exposure
levels—community emergency exposure levels—was replaced by the term
AEGL to reflect the broad application of these values to planning,
response, and prevention in the community, the workplace,
transportation, the military, and the remediation of Superfund sites.”
This document also states that AEGL values “represent threshold
exposure limits for the general public and are applicable to emergency
exposures ranging from 10 minutes to eight hours.” The document lays
out the purpose and objectives of AEGL by stating (page 21) that “the
primary purpose of the AEGL program and the National Advisory Committee
for Acute Exposure Guideline Levels for Hazardous Substances is to
develop guideline levels for once-in-a-lifetime, short-term exposures to
airborne concentrations of acutely toxic, high-priority chemicals.” In
detailing the intended application of AEGL values, the document states
(page 31) that “[i]t is anticipated that the AEGL values will be used
for regulatory and nonregulatory purposes by U.S. Federal and state
agencies and possibly the international community in conjunction with
chemical emergency response, planning, and prevention programs. More
specifically, the AEGL values will be used for conducting various risk
assessments to aid in the development of emergency preparedness and
prevention plans, as well as real-time emergency response actions, for
accidental chemical releases at fixed facilities and from transport
carriers.”

The AEGL–1 value is then specifically defined as “the airborne
concentration of a substance above which it is predicted that the
general population, including susceptible individuals, could experience
notable discomfort, irritation, or certain asymptomatic nonsensory
effects. However, the effects are not disabling and are transient and
reversible upon cessation of exposure.” The document also notes (page
3) that, “Airborne concentrations below AEGL–1 represent exposure
levels that can produce mild and progressively increasing but transient
and nondisabling odor, taste, and sensory irritation or certain
asymptomatic, nonsensory effects.” Similarly, the document defines
AEGL–2 values as “the airborne concentration (expressed as ppm or
mg/m3) of a substance above which it is predicted that the general
population, including susceptible individuals, could experience
irreversible or other serious, long-lasting adverse health effects or an
impaired ability to escape.”

ERPG values are derived for use in emergency response, as described in
the American Industrial Hygiene Association’s document entitled,
Emergency Response Planning Guidelines (ERPG) Procedures and
Responsibilities ( HYPERLINK
"http://www.aiha.org/1documents/committees/ERPSOPs2006.pdf"
http://www.aiha.org/1documents/committees/ERPSOPs2006.pdf )which states
that, “Emergency Response Planning Guidelines were developed for
emergency planning and are intended as health based guideline
concentrations for single exposures to chemicals.” The ERPG–1 value
is defined as “the maximum airborne concentration below which it is
believed that nearly all individuals could be exposed for up to 1 hour
without experiencing other than mild transient adverse health effects or
without perceiving a clearly defined, objectionable odor.” Similarly,
the ERPG–2 value is defined as “the maximum airborne concentration
below which it is believed that nearly all individuals could be exposed
for up to 1 hour without experiencing or developing irreversible or
other serious health effects or symptoms which could impair an
individual’s ability to take protective action.”

As can be seen from the definitions above, the AEGL and ERPG values
include the similarly defined severity levels 1 and 2. For many
chemicals, a severity level 1 value AEGL or ERPG has not been developed;
in these instances, higher severity level AEGL–2 or ERPG–2 values
are compared to our modeled exposure levels to assess potential for
acute concerns.

Acute REL values for 1-hour exposure durations are typically lower than
their corresponding AEGL–1 and ERPG–1 values. Even though their
definitions are slightly different, AEGL–1 values are often similar to
the corresponding ERPG–1 values, and AEGL–2 values are often similar
to ERPG–2 values. Maximum HQ values from our acute screening risk
assessments typically result when basing them on the acute REL value for
a particular pollutant. In cases where our maximum acute HQ value
exceeds 1, we also report the HQ value based on the next highest acute
dose-response value (usually the AEGL–1 and/or the ERPG–1 value).

To develop screening estimates of acute exposures, we developed
estimates of maximum hourly emission rates by multiplying the average
actual annual hourly emission rates by a factor to cover routinely
variable emissions. We chose the factor to use based on process
knowledge and engineering judgment and with awareness of a Texas study
of short-term emissions variability, which showed that most peak
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. This analysis is provided in
Appendix 4 of the Draft Residual Risk Assessment for Secondary Aluminum
Production which 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.
For this source category however, there was no such information
available and the default factor of 10 was used in the acute screening
process..

When worst-case HQ values from the initial acute screen step were less
than 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. However, for this source category no acute values were greater
than 1 and therefore, further refinement was not performed.

Ideally, we would prefer to have continuous measurements over time to
see how the emissions vary by each hour over an entire year. Having a
frequency distribution of hourly emission rates over a year would allow
us to perform a probabilistic analysis to estimate potential threshold
exceedances and their frequency of occurrence. Such an evaluation could
include a more complete statistical treatment of the key parameters and
elements adopted in this screening analysis. However, we recognize that
having this level of data is rare, hence our use of the multiplier
approach.

To better characterize the potential health risks associated with
estimated acute exposures to HAP, and in response to a key
recommendation from the SAB’s peer review of the EPA’s RTR risk
assessment methodologies, we generally examine a wider range of
available acute health metrics than we do for our chronic risk
assessments. This is in response to the SAB’s acknowledgement that
there are generally more data gaps and inconsistencies in acute
reference values than there are in chronic reference values.

Comparisons of the estimated maximum off-site 1-hour exposure levels are
not typically made to occupational levels for the purpose of
characterizing public health risks in RTR assessments. This is because
they are developed for working age adults and are not generally
considered protective for the general public. We note that occupational
ceiling values are, for most chemicals, set at levels higher than a
1-hour AEGL-1.

4. Conducting multipathway exposure and risk screening

The potential for significant human health risks due to exposures via
routes other than inhalation (i.e., multipathway exposures) and the
potential for adverse environmental impacts were evaluated in a two-step
process. In the first step, we determined whether any facilities emitted
any HAP known to be persistent and bio-accumulative in the environment
(PB-HAP). There are 14 PB-HAP compounds or compound classes identified
for this screening in EPA’s Air Toxics Risk Assessment Library
(available at http://www.epa.gov/ttn/fera/risk_atra_vol1.html). They are
cadmium compounds, chlordane, chlorinated dibenzodioxins and furans,
dichlorodiphenyldichloroethylene, heptachlor, hexachlorobenzene,
hexachlorocyclohexane, lead compounds, mercury compounds, methoxychlor,
polychlorinated biphenyls, POM, toxaphene, and trifluralin. Since three
of these PB–HAP (cadmium compounds, POM and chlorinated D/F) are
emitted by at least one facility in this source category, we proceeded
to the second step  of the evaluation. In this step, we determined
whether the facility-specific emission rates of each of the emitted
PB–HAP were large enough to create the potential for significant
non-inhalation human or environmental risks under reasonable, worst-case
conditions. To facilitate this step, we developed emission rate
thresholds for each PB–HAP using a hypothetical worst-case screening
exposure scenario developed for use in conjunction with the EPA’s
TRIM.FaTE model. The hypothetical screening scenario was subjected to a
sensitivity analysis to ensure that its key design parameters were
established such that environmental media concentrations were not
underestimated (i.e., to minimize the occurrence of false negatives or
results that suggest that risks might be acceptable when, in fact,
actual risks are high) and to also minimize the occurrence of false
positives for human health endpoints. We call this application of the
TRIM.FaTE model TRIM-Screen. The facility-specific emission rates of
each of the PB–HAP were compared to the TRIM-Screen emission threshold
values for each of the PB–HAP identified in the source category
datasets to assess the potential for significant human health risks or
environmental risks via non-inhalation pathways. See Section IV for
results of this screening analysis.

5. Conducting other risk-related analyses: facilitywide assessments

To put the source category risks in context, for our residual risk
reviews, we also typically examine the risks from the entire
“facility,” where the facility includes all HAP-emitting operations
within a contiguous area and under common control. In these facilitywide
assessments 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. For the secondary aluminum source category, a
facilitywide assessment was performed for all major sources.

A facilitywide assessment was not conducted for area sources. By
definition, no major sources of HAP (e.g., primary aluminum production
or coil coating operations) are collocated with any of the secondary
aluminum area sources. Further, at many area sources, equipment subject
to the Secondary Aluminum NESHAP is the only HAP-emitting equipment.
Therefore, the most significant HAP emissions from area sources were
already being considered under the area source risk assessment, and low
levels of HAP emissions from equipment not subject to the Secondary
Aluminum NESHAP at these facilities would not contribute appreciably to
the risk profile. The results of the facilitywide assessment for major
sources are provided in Section IV.

6. Considering uncertainties in risk assessment

Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for the Secondary Aluminum source
category addressed in this proposal. Although uncertainty exists, we
believe that our approach, which used conservative tools and
assumptions, ensures that our decisions are health-protective. A brief
discussion of the uncertainties in the emissions datasets, dispersion
modeling, inhalation exposure estimates and dose-response relationships
follows below. A more thorough discussion of these uncertainties is
included in the risk assessment documentation (referenced earlier)
available in the docket for this action.

a. Uncertainties in the emissions datasets

	Although the development of the MACT dataset involved QA/quality
control processes, the accuracy of emissions values will vary depending
on the source of the data, the degree to which data are incomplete or
missing, the degree to which assumptions made to complete the datasets
are accurate, errors in estimating emissions values and other factors.
The emission estimates considered in this analysis were generally
developed from one-time or periodic performance tests that do not
reflect short-term fluctuations during the course of a year or
variations from year to year.

The estimates of peak hourly emission rates for the acute effects
screening assessment were based on a multiplication factor of 10 applied
to the average annual hourly emission rate, which is intended to account
for emission fluctuations due to normal facility operations.

b. Uncertainties in dispersion modeling

	While the analysis employed the 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, model options (e.g., rural/urban, plume
depletion, chemistry) were selected to provide an overestimate of
ambient air concentrations of the HAP rather than underestimates.
However, because of practicality and data limitation reasons, some
factors (e.g., meteorology, building downwash) have the potential in
some situations to overestimate or underestimate ambient impacts. For
example, meteorological data were taken from a single year (1991), and
facility locations can be a significant distance from the sites where
these data were taken. Despite these uncertainties, we believe that at
off-site locations and census block centroids, the approach considered
in the dispersion modeling analysis should generally yield overestimates
of ambient HAP concentrations.

c. Uncertainties in inhalation exposure

	The effects of human mobility on exposures were not included in the
assessment. Specifically, short-term mobility and long-term mobility
between census blocks in the modeling domain were not considered. The
assumption of not considering short or long-term population mobility
does not bias the estimate of the theoretical MIR, nor does it affect
the estimate of cancer incidence since the total population number
remains the same. It does, however, affect the shape of the distribution
of individual risks across the affected population, shifting it toward
higher estimated individual risks at the upper end and reducing the
number of people estimated to be at lower risks, thereby increasing the
estimated number of people at specific risk levels.

	In addition, the assessment predicted the chronic exposures at the
centroid of each populated census block as surrogates for the exposure
concentrations for all people living in that block. Using the census
block centroid to predict chronic exposures tends to over-predict
exposures for people in the census block who live further from the
facility, and under-predict exposures for people in the census block who
live closer to the facility. Thus, using the census block centroid to
predict chronic exposures may lead to a potential understatement or
overstatement of the true maximum impact, but it is an unbiased estimate
of average risk and incidence.

The assessments evaluate the cancer inhalation risks associated with
continuous pollutant exposures over a 70-year period, which is the
assumed lifetime of an individual. In reality, both the length of time
that modeled emissions sources at facilities actually operate (i.e.,
more or less than 70 years) and the domestic growth or decline of the
modeled industry (i.e., the increase or decrease in the number or size
of United States facilities) will influence the risks posed by a given
source category. Depending on the characteristics of the industry, these
factors will, 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 emission 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.

In addition to the uncertainties highlighted above, there are several
other factors specific to the acute exposure assessment. The accuracy of
an acute inhalation exposure assessment depends on the simultaneous
occurrence of independent factors that may vary greatly, such as hourly
emissions rates, meteorology, and human activity patterns. In this
assessment, we assume that individuals remain for 1 hour at the point of
maximum ambient concentration as determined by the co-occurrence of peak
emissions and worst-case meteorological conditions. These assumptions
would tend to overestimate actual exposures since it is unlikely that a
person would be located at the point of maximum exposure during the time
of worst-case impact.

d. Uncertainties in dose-response relationships

	There are uncertainties inherent in the development of the
dose-response values used in our risk assessments for cancer effects
from chronic exposures and noncancer effects from both chronic and acute
exposures. Some uncertainties 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 the EPA 2005 Cancer Guidelines; namely, that “the
primary goal of the 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). In some circumstances, the true risk could be as low as zero;
however, in other circumstances, the risk could also be greater. 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, the 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).

Chronic noncancer reference (RfC and reference dose (RfD)) values
represent chronic exposure levels that are intended to be
health-protective levels. Specifically, these values provide an estimate
(with uncertainty spanning perhaps an order of magnitude) of daily oral
exposure (RfD) or of a continuous inhalation exposure (RfC) to the human
population (including sensitive subgroups) that is likely to be without
an appreciable risk of deleterious effects during a lifetime. To derive
values that are intended to be “without appreciable risk,” the
methodology relies upon an uncertainty factor (UF) approach (U.S. EPA,
1993, 1994) which includes consideration of both uncertainty and
variability. When there are gaps in the available information, UF are
applied to derive reference values that are intended to protect against
appreciable risk of deleterious effects. The UF are commonly default
values, 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. While
collectively termed “uncertainty factor,” 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 more
often they 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).

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 noncancer effects for all pollutants emitted by the
sources included in this assessment, some HAP continue to have no
reference values for cancer or chronic noncancer or acute effects (see
table 3.1-1 of the risk assessment document available in the docket for
this proposed rulemaking). 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. For a
group of compounds that are either unspeciated or do not have reference
values for every individual compound (e.g., POM), we conservatively use
the most protective reference value to estimate risk from individual
compounds in the group of compounds.

Additionally, chronic reference values for several of the compounds
included in this assessment are currently under  the EPA IRIS review,
and revised assessments may determine that these pollutants are more or
less potent than the current value. We may re-evaluate residual risks
for the final rulemaking if these reviews are completed prior to our
taking final action for this source category and a dose-response metric
changes enough to indicate that the risk assessment supporting this
notice may significantly understate human health risk.

e. Uncertainties in the multipathway and environmental effects screening
assessment

We generally assume that when exposure levels are not anticipated to
adversely affect human health, they also are not anticipated to
adversely affect the environment. For each source category, we generally
rely on the site-specific levels of PB-HAP emissions to determine
whether a full assessment of the multipathway and environmental effects
is necessary. For this source category, we only performed a worst-case
multipathway screening assessment for PB-HAP. Thus, it is important to
note that potential PB-HAP multipathway risks are biased high.

B. 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, the EPA determines whether
risks are acceptable. This determination “considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR) of
approximately 1 in 10 thousand [i.e., 100 in 1 million]” (54 at FR
38045). In the second step of the process, the 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 one in one million, as well as other relevant
factors, including costs and economic impacts, technological
feasibility, and other factors relevant to each particular decision”
Id.

In past residual risk actions, the 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 more recent proposals (75 FR
65068, October 21, 2010, and 75 FR 80220, December 21, 2010), the 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). The EPA also discussed and considered risk estimation
uncertainties. The EPA is providing this same type of information in
support of the proposed determinations 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
at 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 the 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, the 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).

For example, 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” (54 FR at 38045). Similarly, with
regard to the ample margin of safety analysis, the EPA stated in the
Benzene NESHAP that: “the 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”
(54 FR at 38061).

The 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 HAP emissions
from the entire facility at which the covered

source category is located (facilitywide risk estimates). We do not
attempt 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 category 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 Science Advisory
Board (SAB) advised us “… that RTR assessments will be most useful
to decision makers and communities if results are presented in the
broader context of aggregate and cumulative risks, including background
concentrations and contributions from other sources in the area.”

While we are interested in placing source category and facilitywide 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 facilitywide estimates hence compounding the
uncertainty in any such comparison. This is because we have not
conducted a detailed technical review of HAP emissions data for source
categories and facilities that have not previously undergone an RTR
review or are not currently undergoing such review. We are requesting
comment on whether and how best to estimate and evaluate total HAP
exposure in our assessments and, in particular, on whether and how it
might be appropriate to use information from EPA’s National Air Toxics
Assessment (NATA) to support such estimates. We are also seeking comment
on how best to consider various types and scales of risk estimates when
making our acceptability and ample margin of safety determinations under
CAA section 112(f).

C. 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 Secondary Aluminum Production 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 appropriate or necessary to propose
amendments to the 2000 NESHAP to require any of the identified
developments.

Based on our analyses of the data and information collected from
industry and the trade organization representing facilities subject to
the NESHAP, our general understanding of the industry, and other
available information in the literature on potential controls for this
industry, we identified several new 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 2000 Secondary Aluminum
Production NESHAP.

Any improvements in add-on control technology or other equipment (that
were identified and considered during development of the 2000 Secondary
Aluminum Production 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 2000 Secondary Aluminum Production
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 2000 Secondary Aluminum Production
NESHAP.

In addition to reviewing the practices, processes, or control
technologies that were not considered at the time we developed the 2000
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 Aluminum Production industry. Among the data
sources we reviewed were the NESHAP for various industries that were
promulgated after the 2000 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 Aluminum Production source category, as well as
the costs, non-air impacts, and energy implications associated with the
use of these technologies.

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. In particular, we
consulted the 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. The 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
Aluminum Production NESHAP. No such practices, processes or control
technologies were identified in this database.

D. 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 the court decision in Sierra Club v. EPA, 551
F. 3d 1019 (D.C. Cir. 2008).

We are also proposing changes to the rule related to affirmative defense
for exceedance of an emission limit during a malfunction. We are
proposing other changes to address HF emissions, fugitive emissions
during testing and numerous clarifications and corrections related to
the existing provisions in the rule. Descriptions of each issue and the
proposed revision to address the issue are presented in Section IV of
this preamble.

IV. Analytical Results and Proposed Decisions

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

A. What are the results of the risk assessments?

For major sources in the Secondary Aluminum source category, we
conducted an inhalation risk assessment for all HAP emitted. In
addition, we performed a facilitywide risk assessment for the major
sources in the secondary aluminum source category. For area sources, we
conducted an inhalation risk assessment for D/F since this is the only
HAP covered by the subpart RRR MACT standards at area sources. For all
sources, we conducted multipathway screening analyses for PB-HAP emitted
(e.g., D/F). Although there are 53 major sources and 108 area sources
covered by the subpart RRR MACT standards, 52 major sources and 103 area
sources were modeled due to the other sources’ lack of equipment with
applicable emission standards. Results of the risk assessment are
presented briefly below and in more detail in the residual risk
documentation referenced in Section III of this preamble, which is
available in the docket for this action.

Table 4 of this preamble provides an overall summary of the results of
the inhalation risk assessment.

Table 4. Secondary Aluminum Production Inhalation Risk Assessment
Results

Category & No of Facilities Modeled	Maximum

Individual

Cancer Risk

(in 1 million)1	Estimated Population

at increased Risk of cancer ≥ 1 in 1 Million	Estimated Annual

Cancer

Incidence (cases per year)	Maximum

Chronic Non-cancer

TOSHI2	Worst-case Maximum Refined Screening Acute Non-cancer HQ3

	Based on Actual Emissions Level	Based on Allowable Emissions Level

	Based on Actual Emissions Level	Based on Allowable Emissions Level

	Major Source (52)	1	20	2	0.0006	0.05	1	HQREL  0.7 (HCl)

Area Source (103)	0.4	6	0	0.0006	0.0003	0.004	-

Facility-wide Major Source	20	-	62,000	0.006	0.9	-	-

1 Estimated maximum individual excess lifetime cancer risk due to HAP
emissions from the source category.

We did not have allowable emissions information at the facilitywide
level, therefore, risk estimates based on facilitywide allowable
emissions were not calculated.

2 Maximum TOSHI. The target organ with the highest TOSHI for the
secondary aluminum source category is the respiratory system.

3 There is no acute dose-response value for dioxins, thus an acute HQ
value for area sources was not calculated. See Section III.B of this
preamble for explanations of acute dose-response values.

	The results of the chronic inhalation cancer risk assessment for major
sources indicate that the maximum lifetime individual cancer risk,
considering actual emissions, could be up to 1 in 1 million, driven by
dioxin emissions. The maximum cancer risks for this source category
exceeded a cancer risk of 1 in 1 million at 1 of 52 facilities. The
total estimated cancer incidence from this source category based on
actual emission levels is 0.0006 excess cancer cases per year, or one
excess case in every 1,666 years. No people were estimated to have
cancer risks above 10 in a million and approximately 2 people were
estimated to have cancer risks above 1 in 1 million considering all
major source facilities in this source category. Based on MACT-allowable
emissions for the major sources in this category, the MIR could be up to
20 in 1 million.

	With respect to chronic inhalation noncancer risk from major sources,
we estimate a maximum TOSHI value of 0.05 for the Secondary Aluminum
source category, primarily from hydrochloric acid from Group 1 furnaces
(handling clean charge only). Considering MACT-allowable emissions, this
maximum TOSHI value is estimated to be 1. Moreover, our worst-case
highest acute screening value for major sources was 0.7 based on the REL
for HCL.

	Considering facility wide emissions at the 52 major sources, the MIR is
estimated to be up to 20 in 1 million, the estimated annual incidence is
0.0006 cases per year and the chronic non-cancer TOSHI value is
calculated to be 0.9.

	In addition, we estimated risks associated with dioxin emissions at the
103 area sources in the Secondary Aluminum Production source category.
The results of the chronic inhalation cancer risk assessment indicate
that the maximum lifetime individual cancer risk could be as high as 0.4
in 1 million and an estimated annual incidence of 0.0006 cases per year.
Considering MACT-allowable emissions, the MIR could be up to 6 in 1
million. With respect to chronic inhalation noncancer risk from D/F
emissions at area sources, we estimate a maximum TOSHI value of 0.0003.
Considering MACT-allowable emissions, this maximum TOSHI value is
estimated to be 0.004 for area sources.

	In addition to the analyses presented above, to screen for potential
multipathway effects from emissions of PB-HAP (such as cadmium, dioxins
and PAHs) we compared actual emission rates from major source facilities
in this source category to the screening values for these PB HAP
described above (see Section III (A)(4)). For dioxins, we also screened
for potential multipathway effects from emissions of D/F from area
sources by comparing the estimated actual emission rates from these area
sources to the screening value for D/F described above. (see Risk
Assessment Document Appendix 4 for a more detailed discussion of
screening emission rates). Results of this worst-case screen estimate
that actual POM emissions from 20 of the 52 major source facilities
exceed the POM screening emission rate. With respect to D/F, of the 46
major sources that emitted dioxins, 39 exceeded our screening emission
rate. Similarly, 76 out of 103 area sources exceeded our D/F screening
rate. These exceedances of the worst-case multipathway screening level
for POM and dioxins indicate that there may be potential multipathway
impacts of concern due to emissions of POM and dioxins. In general,
emission rates below the worst-case multipathway screening level
indicate no significant potential for multipathway-related health
effects; whereas emission levels above this worst-case screening level
only indicate the potential for multipathway-related health risks of
concern based on a worst-case scenario. Thus, we note that these
screening values are biased high for purposes of screening and are
subject to significant uncertainties. As such, they do not represent
refined estimates of risk and thus, do not necessarily indicate that
potential multipathway risks from the source category are significant -
only that we cannot rule out the possibility that they might be
significant.

	With respect to the potential for adverse environmental effects from
non PB-HAP, we note that for both major and area sources all chronic
non-cancer HQ values for all pollutants considering actual emissions are
well below 1 using human health reference values. Thus, we believe that
it is unlikely that adverse environmental effects would occur at the
actual HAP concentrations estimated in our human health risk assessment.

B. What are our proposed decisions regarding risk acceptability and
ample margin of safety?

1. Risk acceptability

As noted in Section III.C of this preamble, we weigh all health risk
factors in our risk acceptability determination, including the MIR, the
numbers of persons in various risk ranges, cancer incidence, the maximum
noncancer HI, the maximum acute noncancer hazard, the extent of
noncancer risks, the potential for adverse environmental effects,
distribution of risks in the exposed population, and risk estimation
uncertainties (54 FR 38044, September 14, 1989).

	For the Secondary Aluminum Production source category, the risk
analysis indicates that the cancer risks to the individual most exposed
could be as high as 1 in 1 million due to actual emissions and as high
as 20 in 1 million due to MACT-allowable emissions. These risks are
considerably less than 100 in 1 million, which is the presumptive upper
limit of acceptable risk. The risk analysis also shows very low cancer
incidence (0.0006 cases per year), as well as no potential for adverse
chronic or acute non-cancer health effects.

	In addition to the analyses presented above, to screen for potential
multipathway effects from emissions of D/F and POM, we compared the
estimated actual emission rates from facilities in this source category
to the multipathway screening levels described in section III.B. With
respect to POM and dioxins, both major and area sources in the category
exceeded our worst-case screening levels. However, we note that this is
a worst-case conservative screening level analysis, therefore these
results are biased high for purposes of screening and are subject to
significant uncertainties. Moreover, we note that due to data
limitations we were unable to further refine this worst-case screening
scenario. As such, they do not necessarily indicate that significant
multipathway risks actually exist at secondary aluminum facilities, only
that we cannot rule them out as a possibility. With regard to
facilitywide risk, based on the low level of risk identified for the
source category, a facilitywide analysis was not conducted for this
source category.

	Considering all of the health risk information and factors discussed
above, including the uncertainties discussed in section IV.A.7 of this
preamble, we propose that the risks from the Secondary Aluminum
Production source category are acceptable.

2. Ample margin of safety analysis

	We next considered whether the existing MACT standard provides an ample
margin of safety to protect public health. Under the ample margin of
safety analysis, we evaluated the cost and feasibility of available
control technologies and other measures (including the controls,
measures and costs reviewed under the technology review) that could be
applied in this source category to further reduce the risks (or
potential risks) due to emissions of HAP identified in our risk
assessment, along with all of the health risks and other health
information considered in the risk acceptability determination described
above. In this analysis we considered the results of the technology
review, risk assessment and other aspects of our MACT rule review to
determine whether there are any cost-effective controls or other
measures that would reduce emissions further to provide an ample margin
of safety with respect to the risks associated with these emissions.

	For POM, THC and metal HAP emissions, our risk analysis indicated very
low potential for risk from the facilities in the source category. Our
technology review did not identify any new practices, controls or
process options that are being used in this industry or in other
industries that would be cost-effective for further reduction of these
emissions. Based on the estimated low risk levels and absence of new
practices or control options, we conclude that the provisions of the
current MACT provide for an ample margin of safety for public health
with respect to emissions of POM, THC and metal HAP.

	Our multipathway screening analysis results indicated exceedances of
the worst case screening  levels which do not necessarily indicate any
risks, however, they do suggest a potential for risks that cannot be
ruled out. To evaluate the potential to reduce D/F emissions to ensure
an ample margin of safety, our analysis for D/F focused on two options:
1) lowering the existing D/F limit from 15 to 10 µg TEQ/Mg feed for
Group 1 furnaces processing other than clean charge at all facilities;
and 2) lowering the existing D/F limit for Group 1 furnaces processing
other than clean charge, after applying a subcategorization-based on
facility production capacity. The lower D/F limits potentially could be
met by using an activated carbon injection (ACI) system. With regard to
the option of lowering the emission limit to 10 µg TEQ/Mg feed for
Group 1 furnaces handling other than clean charge, we estimate that
about 11 facilities would need to reduce their D/F emissions and that
the costs would be about $5.9 million in total capital costs with total
annualized costs of about $2.7 million. This option would achieve an
estimated 1.66 grams TEQ reduction of D/F emissions with an overall
cost-effectiveness of about $1.61 million per gram D/F TEQ. The second
option of lowering the emission limit based on a subcategorization
according to facility production capacity yielded cost-effectiveness
estimates of greater than $1 million per gram D/F TEQ reduced.
Furthermore, our analysis indicates that these options would not result
in significant emissions reductions and would not, therefore, result in
significant changes to the potential risk levels. After considering the
costs and the small reductions that would be achieved, we have decided
not to propose any of these options that are based on ACI injection
technology.

	We also evaluated possible options based on work practices to achieve
further emissions reductions. The current subpart RRR NESHAP includes
work practices to minimize D/F emissions which include scrap inspection,
limitations on materials processed by group 2 furnaces, temperature and
residence time requirements for afterburners controlling sweat furnaces,
labeling requirements, capture/collection requirements, and requirements
for an operations, maintenance and monitoring plan that contains details
on the proper operation and maintenance of processes and control
equipment. We searched for and evaluated other possible work practices
such as good combustion practices, better scrap inspection and cleaning,
and process monitoring. However, none of these potential work practices
were determined to be feasible and effective in reducing D/F emissions
for this source category. Thus, we did not identify any feasible or
applicable work practices for this industry beyond those that are
currently in the MACT rule.

	In accordance with the approach established in the Benzene NESHAP, we
weighed all health risk information and factors considered in the risk
acceptability determination, including uncertainties, along with the
cost and feasibility of control technologies and other measures that
could be applied in this source category, in making our ample margin of
safety determination. In summary, we did not identify any cost-effective
approaches to further reduce POM, THC, metal HAP or D/F emissions beyond
the reductions that are already being achieved by the current NESHAP.
Further, our analysis indicates that none of the options considered
would result in significant emissions reductions and would not,
therefore, result in significant changes to the potential risk levels.

	Because of the high cost associated with the use of activated carbon
injection systems and because work practices are already required to
help ensure low emissions, we propose that the existing MACT standards
provide an ample margin of safety to protect public health and prevent
an adverse environmental effect.

C. What are the results and proposed decisions based on our technology
review?

As described above, the typical controls used to minimize emissions at
secondary aluminum facilities include fabric filters for control of PM
from aluminum scrap shredders; afterburners for control of THC and D/F
from thermal chip dryers; afterburners plus lime-injected fabric filters
for control of PM, HCl, THC, and D/F from scrap dryers/delacquering
kilns/decoating kilns; afterburners for control of D/F from sweat
furnaces; fabric filters for control of PM from dross-only furnaces and
rotary dross coolers; lime-injected fabric filters for control of PM and
HCl from in-line fluxers; and lime-injected fabric filters for control
of PM, HCl and D/F from group 1 furnaces. There have been some
developments in practices, processes, or control technologies that have
been implemented in this source category since promulgation of the
current NESHAP. However, these technologies do not clearly reduce HAP
emissions relative to technologies that were available at the time of
promulgation of the Secondary Aluminum Production NESHAP in 2000.

At least one company supplies multichamber furnaces that combine the
functions of a delacquering kiln and a melting furnace. At least 16 of
these furnaces are in operation in Europe, Asia and the Middle East. One
furnace of this type is presently operating in the U. S. and is
permitted as a group 1 furnace handling other than clean charge.
However, the D/F emission test data for the one operating U.S.
multichamber furnace are not lower than all other Group 1 furnaces
handling other than clean charge and are not lower than all delacquering
kiln emission test data. Based on available information it is not clear
that this technology would reduce HAP emissions relative to technologies
that are already used by other facilities in the U.S. Overall, based on
our analyses, we conclude that it would not be appropriate to require
other facilities in the U.S. to use this technology at this time.

Eddy current separators are used to separate a concentrated aluminum
fraction from a heterogeneous scrap feed. These units operate at ambient
temperature and emit no D/F or other gaseous pollutants. They are used
on the material output from mechanical shredders that shred automobiles
and appliances (not on the scrap shredders used in the secondary
aluminum industry). These units can potentially decrease the need for
sweat furnaces. However, the product of eddy current separators is not
clean charge, as with a sweat furnace. Therefore, the product of eddy
current separators must undergo further processing to produce clean
charge, and it is not possible to directly compare eddy current
separators with sweat furnaces.

Catalytic filtration systems, including catalytic filter bags, are
available to reduce D/F emissions. These bags incorporate an expanded
polytetrafluoroethylene membrane coated with a precious metal catalyst
which promotes the oxidation of D/F. The manufacturer claims that this
system is installed in over 100 applications around the world, including
at least 1 secondary aluminum processing plant. However, no respondents
to our all-company ICR reported using this technology, and we have no
data on the D/F emissions reductions that can be achieved at secondary
aluminum production facilities using this technology. We therefore
conclude that catalytic filtration systems are not yet a demonstrated
technology that can be broadly applied to the secondary aluminum
production source category at this time.

We also evaluated the potential to lower D/F emissions under the
technology review by lowering the emissions limits which would likely
result in the broader use of activated carbon injection technology.
Under this analysis, we evaluated the exact same approach that was
evaluated under the ample margin of safety analysis described in section
IV.B. In summary, we evaluated two main options, as follows: 1) lower
the existing D/F limit from 15 to 10 µg TEQ/Mg feed for Group 1
furnaces processing other than clean charge at all facilities; and 2)
lower the existing D/F limit for Group 1 furnaces processing other than
clean charge, after applying a subcategorization-based on facility
production capacity. The lower D/F emissions limits potentially could be
met by using an activated carbon injection (ACI) system. With regard to
the option of lowering the emission limit to 10 µg TEQ/Mg feed for
Group 1 furnaces handling other than clean charge, we estimate that
about 11 facilities would need to reduce their D/F emissions and that
the costs would be about $5.9 million in total capital costs with total
annualized costs of about $2.7 million. This option would achieve an
estimated 1.66 grams TEQ reduction of D/F emissions with an overall
cost-effectiveness of about $1.61 million per gram D/F TEQ. The second
option of lowering the emission limit based on a subcategorization
according to facility production capacity yielded cost-effectiveness
estimates of greater than $1 million per gram D/F TEQ reduced.
Furthermore, our analysis indicates that these options would not result
in significant emissions reductions. After considering the costs and the
small reductions that would be achieved, we have decided not to propose
either of these options that are based on ACI injection technology under
section 112(d)(6) of the CAA.

Overall, based on our technology review, we determined that the
developments in practices, processes and control technologies identified
do not clearly reduce emissions relative to technologies that were
available at the time of promulgation of the Secondary Aluminum
Production NESHAP in 2000. We did not identify any feasible and cost
effective options to further reduce emissions as part of technology
review. Therefore, we are not proposing any revisions to the NESHAP as
part of our technology review. Additional details regarding these
analyses can be found in the following technical document for this
action which is available in the docket: Draft Technology Review for the
Secondary Aluminum Production Source Category.