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Proposed Rule2021-28273

National Emission Standards for Hazardous Air Pollutants: Primary Copper Smelting Residual Risk and Technology Review and Primary Copper Smelting Area Source Technology Review

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Published

January 11, 2022

Issuing agencies

Environmental Protection Agency

Abstract

This proposal presents the results of the U.S. Environmental Protection Agency's (EPA's) residual risk and technology review (RTR) for the National Emission Standards for Hazardous Air Pollutants (NESHAP) for major source Primary Copper Smelters as required under the Clean Air Act (CAA). Pursuant to the CAA, this action also presents the results of the technology review for the Primary Copper Smelting area source NESHAP. The EPA is proposing new emissions standards in the major source NESHAP. The EPA is also proposing to remove exemptions for periods of startup, shutdown, and malfunction (SSM) and specify that the emission standards apply at all times and require electronic reporting of performance test results and notification of compliance reports.

Full Text

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[Federal Register Volume 87, Number 7 (Tuesday, January 11, 2022)]
[Proposed Rules]
[Pages 1616-1655]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2021-28273]

[[Page 1615]]

Vol. 87

Tuesday,

No. 7

January 11, 2022

Part V

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants: Primary
Copper Smelting Residual Risk and Technology Review and Primary Copper
Smelting Area Source Technology Review; Proposed Rule

Federal Register / Vol. 87 , No. 7 / Tuesday, January 11, 2022 /
Proposed Rules

[[Page 1616]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0430; FRL-7522-01-OAR]
RIN 2060-AU63

National Emission Standards for Hazardous Air Pollutants: Primary
Copper Smelting Residual Risk and Technology Review and Primary Copper
Smelting Area Source Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: This proposal presents the results of the U.S. Environmental
Protection Agency's (EPA's) residual risk and technology review (RTR)
for the National Emission Standards for Hazardous Air Pollutants
(NESHAP) for major source Primary Copper Smelters as required under the
Clean Air Act (CAA). Pursuant to the CAA, this action also presents the
results of the technology review for the Primary Copper Smelting area
source NESHAP. The EPA is proposing new emissions standards in the
major source NESHAP. The EPA is also proposing to remove exemptions for
periods of startup, shutdown, and malfunction (SSM) and specify that
the emission standards apply at all times and require electronic
reporting of performance test results and notification of compliance
reports.

DATES: Comments. Comments must be received on or before February 25,
2022. Under the Paperwork Reduction Act (PRA), comments on the
information collection provisions are best assured of consideration if
the Office of Management and Budget (OMB) receives a copy of your
comments on or before February 10, 2022.
Public hearing. If anyone contacts us requesting a public hearing
on or before January 18, 2022, the EPA will hold a virtual public
hearing. See SUPPLEMENTARY INFORMATION for information on requesting
and registering for a public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2020-0430, by any of the following methods:
<bullet> Federal eRulemaking Portal: <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>
(our preferred method). Follow the online instructions for submitting
comments.
<bullet> Email: <a href="/cdn-cgi/l/email-protection#c2a3efa3aca6efb0efa6ada1a9a7b682a7b2a3eca5adb4">[email&#160;protected]</a>. Include Docket ID No. EPA-
HQ-OAR-2020-0430 in the subject line of the message.
<bullet> Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2020-0430.
<bullet> Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2020-0430, Mail Code 28221T, 1200
Pennsylvania Avenue NW, Washington, DC 20460.
<bullet> Hand/Courier Delivery: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-
Friday (except federal holidays).
Instructions: All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the SUPPLEMENTARY
INFORMATION section of this document. Out of an abundance of caution
for members of the public and our staff, the EPA Docket Center and
Reading Room are closed to the public, with limited exceptions, to
reduce the risk of transmitting COVID-19. Our Docket Center staff will
continue to provide remote customer service via email, phone, and
webform. The EPA encourages the public to submit comments via <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> or email, as there may be a delay in processing
mail and faxes. Hand deliveries and couriers may be received by
scheduled appointment only. For further information on EPA Docket
Center services and the current status, please visit us online at
<a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Tonisha Dawson, 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 number: (919) 541-1454; fax number: (919) 541-4991;
and email address: <a href="/cdn-cgi/l/email-protection#9df9fceaeef2f3b3e9f2f3f4eef5fcddf8edfcb3faf2eb">[email&#160;protected]</a>. For specific information
regarding the risk modeling methodology, contact James Hirtz, Health
and Environmental Impacts Division (C539-02), Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711; telephone number: (919) 541-0881;
fax number: (919) 541-4991; and email address: <a href="/cdn-cgi/l/email-protection#b7dfdec5c3cd99ddd6dad2c4f7d2c7d699d0d8c1">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION:
Executive Summary. This proposal presents the results of the EPA's
residual risk and technology review (RTR) for the NESHAP for major
source Primary Copper Smelters as required under the CAA. Pursuant to
the CAA, this action also presents the results of the technology review
for the Primary Copper Smelting area source NESHAP.
Based on the results of the risk review, the EPA is proposing that
risks from emissions of air toxics from this major source category are
unacceptable. The EPA also completed a demographic analysis which
indicates that elevated cancer risks associated with emissions from the
major source category disproportionately affect communities with
environmental justice concerns, including low-income residents, Native
Americans, and Hispanics living near these facilities. To address these
risks, the EPA is proposing new emissions standards in the major source
NESHAP, which will reduce risks to an acceptable level, and is also
proposing work practice standards to provide an ample margin of safety
to protect public health.
The EPA is also proposing new emissions standards for the major
source NESHAP to address currently unregulated emissions of hazardous
air pollutants (HAP), as follows: Particulate matter (PM), as a
surrogate for particulate HAP metals, for anode refining furnace point
source emissions; and PM for roofline emissions from anode refining
furnaces, smelting furnaces, and converters. EPA is also proposing new
emission standards for mercury emissions from any combination of stacks
from dryers, converters, anode refining furnaces, and smelting
furnaces. The EPA is proposing test methods for roofline PM emissions
and amending the test methods to incorporate by reference three
voluntary consensus standards (VCS).
Under the technology review, the EPA identified no developments in
practices, processes, or control technologies to achieve further
emissions reductions beyond the controls and reductions proposed under
the risk review for major sources. With regard to primary copper
smelting area sources, the Agency did not identify any developments in
practices, processes, or control technologies.
The EPA is also proposing to remove exemptions for periods of
startup, shutdown, and malfunction (SSM) and specify that the emission
standards apply at all times and require electronic reporting of
performance test results and notification of compliance reports.
Implementation of these proposed rules is expected to reduce HAP metal
emissions from primary copper

[[Page 1617]]

smelters, improve human health, and reduce environmental impacts
associated with those emissions.
Participation in virtual public hearing. Please note that the EPA
is deviating from its typical approach for public hearings because the
President has declared a national emergency. Due to the current Centers
for Disease Control and Prevention (CDC) recommendations, as well as
state and local orders for social distancing to limit the spread of
COVID-19, the EPA cannot hold in-person public meetings at this time.
To request a virtual public hearing, contact the public hearing
team at (888) 372-8699 or by email at <a href="/cdn-cgi/l/email-protection#adfefdfde9ddd8cfc1c4cec5c8ccdfc4c3caedc8ddcc83cac2db">[email&#160;protected]</a>. If
requested, the virtual hearing will be held on January 26, 2022. The
hearing will convene at 9:00 a.m. Eastern Time (ET) and will conclude
at 3:00 p.m. ET. The EPA may close a session 15 minutes after the last
pre-registered speaker has testified if there are no additional
speakers. The EPA will announce further details at <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air</a>.
The EPA will begin pre-registering speakers for the hearing upon
publication of this document in the Federal Register. To register to
speak at the virtual hearing, please use the online registration form
available at <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air</a> or
contact the public hearing team at (888) 372-8699 or by email at
<a href="/cdn-cgi/l/email-protection#792a29293d090c1b15101a111c180b10171e391c0918571e160f">[email&#160;protected]</a>. The last day to pre-register to speak at the
hearing will be January 24, 2022. Prior to the hearing, the EPA will
post a general agenda that will list pre-registered speakers in
approximate order at: <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air</a>.
The EPA will make every effort to follow the schedule as closely as
possible on the day of the hearing; however, please plan for the
hearings to run either ahead of schedule or behind schedule.
Each commenter will have 5 minutes to provide oral testimony. The
EPA encourages commenters to provide the EPA with a copy of their oral
testimony electronically (via email) by emailing it to
<a href="/cdn-cgi/l/email-protection#7a1e1b0d091514540e15141309121b3a1f0a1b541d150c">[email&#160;protected]</a>. The EPA also recommends submitting the text of
your oral testimony as written comments to the rulemaking docket.
The EPA may ask clarifying questions during the oral presentations
but will not respond to the presentations at that time. Written
statements and supporting information submitted during the comment
period will be considered with the same weight as oral testimony and
supporting information presented at the public hearing.
Please note that any updates made to any aspect of the hearing will
be posted online at <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air</a>. While the EPA expects the hearing to go forward as set
forth above, please monitor our website or contact the public hearing
team at (888) 372-8699 or by email at <a href="/cdn-cgi/l/email-protection#66353636221613040a0f050e0307140f08012603160748010910">[email&#160;protected]</a> to
determine if there are any updates. The EPA does not intend to publish
a document in the Federal Register announcing updates.
If you require the services of a translator or a special
accommodation such as audio description, please pre-register for the
hearing with the public hearing team and describe your needs by January
18, 2022. The EPA may not be able to arrange accommodations without
advanced notice.
Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2020-0430. All documents in the docket are
listed in <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>. Although listed, some
information is not publicly available, e.g., Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the internet and will be publicly available only in hard
copy. With the exception of such material, publicly available docket
materials are available electronically in <a href="http://Regulations.gov">Regulations.gov</a>.
Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2020-0430. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal
information provided, unless the comment includes information claimed
to be CBI or other information whose disclosure is restricted by
statute. Do not submit electronically any information that you consider
to be CBI or other information whose disclosure is restricted by
statute. This type of information should be submitted by mail as
discussed below.
The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the Web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
The <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> website allows you to submit your
comment anonymously, which means the EPA will not know your identity or
contact information unless you provide it in the body of your comment.
If you send an email comment directly to the EPA without going through
<a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, your email address will be automatically
captured and included as part of the comment that is placed in the
public docket and made available on the internet. If you submit an
electronic comment, the EPA recommends that you include your name and
other contact information in the body of your comment and with any
digital storage media you submit. If the EPA cannot read your comment
due to technical difficulties and cannot contact you for clarification,
the EPA may not be able to consider your comment. Electronic files
should not include special characters or any form of encryption and be
free of any defects or viruses. For additional information about the
EPA's public docket, visit the EPA Docket Center homepage at <a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.
The EPA is temporarily suspending its Docket Center and Reading
Room for public visitors, with limited exceptions, to reduce the risk
of transmitting COVID-19. Our Docket Center staff will continue to
provide remote customer service via email, phone, and webform. The EPA
encourages the public to submit comments via <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> as there may be a delay in processing mail and
faxes. Hand deliveries or couriers will be received by scheduled
appointment only. For further information and updates on EPA Docket
Center services, please visit us online at <a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.
The EPA continues to carefully and continuously monitor information
from the CDC, local area health departments, and our Federal partners
so that the Agency can respond rapidly as conditions change regarding
COVID-19.
Submitting CBI. Do not submit information containing CBI to the EPA
through <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> or email. Clearly mark all of the

[[Page 1618]]

information that you claim to be CBI. For CBI information on any
digital storage media that you mail to the EPA, mark the outside of the
digital storage media as CBI and then identify electronically within
the digital storage media the specific information that is claimed as
CBI. In addition to one complete version of the comments that includes
information claimed as CBI, you must submit a copy of the comments that
does not contain the information claimed as CBI directly to the public
docket through the procedures outlined in Instructions above. If you
submit any digital storage media that does not contain CBI, mark the
outside of the digital storage media clearly that it does not contain
CBI. Information not marked as CBI will be included in the public
docket and the EPA's electronic public docket without prior notice.
Information marked as CBI will not be disclosed except in accordance
with procedures set forth in 40 Code of Federal Regulations (CFR) part
2. Send or deliver information identified as CBI only to the following
address: Office of Air Quality Planning and Standards Document Control
Officer (C404-02), OAQPS, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711, Attention Docket ID No.
EPA-HQ-OAR-2020-0430. Note that written comments containing CBI and
submitted by mail may be delayed and no hand deliveries will be
accepted.
Preamble acronyms and abbreviations. The Agency uses multiple
acronyms and terms in this preamble. While this list may not be
exhaustive, to ease the reading of this preamble and for reference
purposes, the EPA defines the following terms and acronyms here:

ACI activated carbon injection
AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-4 model
BTF beyond-the-floor
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CFR Code of Federal Regulations
mg/dscm milligrams per dry standard cubic meter
ECHO Enforcement and Compliance History Online
EPA Environmental Protection Agency
ERPG emergency response planning guideline
ERT Electronic Reporting Tool
GACT generally available control technology
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-4 Human Exposure Model, Version 1.5.5
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
ICR Information Collection Request
IRIS Integrated Risk Information System
km kilometer
MACT maximum achievable control technology
mg/kg-day milligrams per kilogram per day
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NEI National Emissions Inventory
NESHAP national emission standards for hazardous air pollutants
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PM particulate matter
POM polycyclic organic matter
ppm parts per million
RBLC Reasonably Available Control Technology, Best Available Control
Technology, and Lowest Achievable Emission Rate Clearinghouse
RfC reference concentration
RTR residual risk and technology review
SAB Science Advisory Board
SV screening value
SSM startup, shutdown, and malfunction
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and
Ecological Exposure model
UF uncertainty factor
[micro]g/m\3\ microgram per cubic meter
URE unit risk estimate
USGS U.S. Geological Survey
VCS voluntary consensus standards

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

I. General Information
A. Does this action apply to me?
B. Where can I get a copy of this document and other related
information?
II. Background
A. What is the statutory authority for this action?
B. What is this source category and how does the current NESHAP
regulate its HAP emissions?
C. What data collection activities were conducted to support
this action?
D. What other relevant background information and data are
available?
III. Analytical Procedures and Decision-Making
A. How do we consider risk in our decision-making?
B. How do we perform the technology review?
C. How do we estimate post-MACT risk posed by the source
category?
IV. Analytical Results and Proposed Decisions
A. What actions are we taking pursuant to CAA sections 112(d)(2)
and 112(d)(3)?
B. What are the results of the risk assessment and analyses?
C. What are our proposed decisions regarding risk acceptability,
ample margin of safety, and adverse environmental effect?
D. What are the results and proposed decisions based on our
technology review?
E. What other actions are we proposing?
F. What compliance dates are we proposing?
V. Summary of Cost, Environmental, and Economic Impacts
A. What are the affected sources?
B. What are the air quality impacts?
C. What are the cost impacts?
D. What are the economic impacts?
E. What are the benefits?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Incorporation by Reference
IX. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
B. Paperwork Reduction Act (PRA)
C. Regulatory Flexibility Act (RFA)
D. Unfunded Mandates Reform Act (UMRA)
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks and 1 CFR part 51
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
I. National Technology Transfer and Advancement Act (NTTAA)
J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. General Information

A. Does this action apply to me?

The source categories that are the subject of this proposal are
Primary Copper Smelting Major Sources regulated under 40 CFR part 63,
subpart QQQ, and Primary Copper Smelting Area Sources, regulated under
40 CFR part 63, subpart EEEEEE. The North American Industry
Classification System (NAICS) code for the primary copper smelting
industry is 331410. This list of categories and NAICS codes is not
intended to be exhaustive, but rather provides a guide for readers
regarding the entities that this proposed action is likely to affect.
The proposed standards, once promulgated, will be directly applicable
to the affected sources. State, local, and tribal governments would not
be directly affected by this proposed action. As defined in the Initial
List of Categories of Sources Under Section 112(c)(1) of

[[Page 1619]]

the Clean Air Act Amendments of 1990 (see 57 FR 31576, July 16, 1992)
and Documentation for Developing the Initial Source Category List,
Final Report (see EPA-450/3-91-030, July 1992), the Primary Copper
Smelting major source category was defined as any major source facility
engaged in the pyrometallurgical process used for the extraction of
copper from sulfur oxides, native ore concentrates, or other copper
bearing minerals. As originally defined, the category includes, but is
not limited to, the following smelting process units: Roasters,
smelting furnaces, and converters. Affected sources under the current
major source NESHAP are concentrate dryers, smelting furnaces, slag
cleaning vessels, converters, and fugitive emission sources. The area
source category was added to the source category list in 2002 (67 FR
70427, 70428). Affected sources under the area source NESHAP are
concentrate dryers, smelting vessels (e.g., furnaces), converting
vessels, matte drying and grinding plants, secondary gas systems, and
anode refining operations.

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

In addition to being available in the docket, an electronic copy of
this action is available on the internet. Following signature by the
EPA Administrator, the EPA will post a copy of this proposed action at
<a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air</a> and at <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-area-sources-national-emissions-standards">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-area-sources-national-emissions-standards</a>. Following publication in the
Federal Register, the EPA will post the Federal Register version of the
proposal and key technical documents at these same websites.
Information on the overall RTR program is available at <a href="https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous">https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous</a>.
The proposed changes to the CFR that would be necessary to
incorporate the changes proposed in this action are presented in
attachments to the two memoranda titled: Proposed Regulation Edits for
40 CFR part 63, subpart QQQ: Primary Copper Smelting NESHAP Risk and
Technology Review Proposal; and Proposed Regulatory Edits for 40 CFR
part 63 Subpart EEEEEE: Primary Copper Smelting Area Sources NESHAP
Technology Review Proposal, both of which are available in the docket
for this action (Docket ID No. EPA-HQ-OAR-2020-0430). These documents
include redline versions of the two regulations. Following signature by
the EPA Administrator, the EPA will also post a copy of these two
memoranda and the attachments to <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air</a> and to <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-area-sources-national-emissions-standards">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-area-sources-national-emissions-standards</a>.

II. Background

A. What is the statutory authority for this action?

The statutory authority for this action is provided by sections 112
and 301 of the CAA, as amended (42 U.S.C. 7401 et seq.). Section 112 of
the CAA establishes a two-stage regulatory process to develop standards
for emissions of HAP from stationary sources. Generally, the first
stage involves establishing technology-based standards and the second
stage involves evaluating those standards that are based on maximum
achievable control technology (MACT) to determine whether additional
standards are needed to address any remaining risk associated with HAP
emissions. This second stage is required under CAA section 112(f) and
is commonly referred to as the ``residual risk review.'' In addition to
the residual risk review, section 112(d)(6) of the CAA requires the EPA
to review standards set under CAA section 112 every 8 years and revise
the standards as necessary taking into account any ``developments in
practices, processes, or control technologies.'' This review is
commonly referred to as the ``technology review.'' When the two reviews
are combined into a single rulemaking, it is commonly referred to as
the ``risk and technology review.'' The discussion that follows
identifies the most relevant statutory sections and briefly explains
the contours of the methodology used to implement these statutory
requirements. A more comprehensive discussion appears in the document
titled CAA Section 112 Risk and Technology Reviews: Statutory Authority
and Methodology, in the docket for this rulemaking.
In the first stage of the CAA section 112 standard setting process,
the EPA promulgates technology-based standards under CAA section 112(d)
for categories of sources identified as emitting one or more of the HAP
listed in CAA section 112(b). Sources of HAP emissions are either major
sources or area sources, and CAA section 112 establishes different
requirements for major source standards and area source standards.
``Major sources'' are those that emit or have the potential to emit 10
tons per year (tpy) or more of a single HAP or 25 tpy or more of any
combination of HAP. All other sources are ``area sources.'' For major
sources, CAA section 112(d)(2) provides that the technology-based
NESHAP must reflect the maximum degree of emission reductions of HAP
achievable (after considering cost, energy requirements, and non-air
quality health and environmental impacts). These standards are commonly
referred to as MACT standards. CAA section 112(d)(3) also establishes a
minimum control level for MACT standards, known as the MACT ``floor.''
In certain instances, as provided in CAA section 112(h), the EPA may
set work practice standards in lieu of numerical emission standards.
The EPA must also consider control options that are more stringent than
the floor. Standards more stringent than the floor are commonly
referred to as beyond-the-floor (BTF) standards. For area sources, CAA
section 112(d)(5) gives the EPA discretion to set standards based on
generally available control technologies or management practices (GACT
standards) in lieu of MACT standards.
The second stage in standard-setting focuses on identifying and
addressing any remaining (i.e., ``residual'') risk pursuant to CAA
section 112(f). For source categories subject to MACT standards,
section 112(f)(2) of the CAA requires the EPA to determine whether
promulgation of additional standards is needed to provide an ample
margin of safety to protect public health or to prevent an adverse
environmental effect. Section 112(d)(5) of the CAA provides that this
residual risk review is not required for categories of area sources
subject to GACT standards. Section 112(f)(2)(B) of the CAA further
expressly preserves the EPA's use of the two-step approach for
developing standards to address any residual risk and the Agency's
interpretation of ``ample margin of safety'' developed in the National
Emissions Standards for Hazardous Air Pollutants: Benzene Emissions
from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene
Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery
Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA
notified Congress in the Residual Risk Report that the Agency intended
to use the Benzene NESHAP approach in making CAA section 112(f)
residual risk

[[Page 1620]]

determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently
adopted this approach in its residual risk determinations and the
United States Court of Appeals for the District of Columbia Circuit
upheld the EPA's interpretation that CAA section 112(f)(2) incorporates
the approach established in the Benzene NESHAP. See NRDC v. EPA, 529
F.3d 1077, 1083 (D.C. Cir. 2008).
The approach incorporated into the CAA and used by the EPA to
evaluate residual risk and to develop standards under CAA section
112(f)(2) is a two-step approach. In the first step, the EPA determines
whether risks are acceptable. This determination ``considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR)
\1\ of approximately 1 in 10 thousand.'' (54 FR at 38045). If risks are
unacceptable, the EPA must determine the emissions standards necessary
to reduce risk to an acceptable level without considering costs. In the
second step of the approach, the EPA considers whether the emissions
standards provide an ample margin of safety to protect public health
``in consideration of all health information, including the number of
persons at risk levels higher than approximately 1 in 1 million, as
well as other relevant factors, including costs and economic impacts,
technological feasibility, and other factors relevant to each
particular decision.'' Id. The EPA must promulgate emission standards
necessary to provide an ample margin of safety to protect public health
or determine that the standards being reviewed provide an ample margin
of safety without any revisions. After conducting the ample margin of
safety analysis, the Agency considers whether a more stringent standard
is necessary to prevent, taking into consideration costs, energy,
safety, and other relevant factors, an adverse environmental effect.
---------------------------------------------------------------------------

\1\ Although defined as ``maximum individual risk,'' MIR refers
only to cancer risk. MIR, one metric for assessing cancer risk, is
the estimated risk if an individual were exposed to the maximum
level of a pollutant for a lifetime.
---------------------------------------------------------------------------

CAA section 112(d)(6) separately requires the EPA to review
standards promulgated under CAA section 112 and revise them ``as
necessary (taking into account developments in practices, processes,
and control technologies)'' no less often than every 8 years. While
conducting the technology review, the EPA is not required to
recalculate the MACT floor. Natural Resources Defense Council (NRDC) v.
EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008). Association of Battery
Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 2013). The EPA may
consider cost in deciding whether to revise the standards pursuant to
CAA section 112(d)(6). The EPA is required to address regulatory gaps,
such as missing standards for listed air toxics known to be emitted
from the source category. Louisiana Environmental Action Network (LEAN)
v. EPA, 955 F.3d 1088 (D.C. Cir. 2020).

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

The primary copper smelting source category includes any facility
that uses a pyrometallurgical process to produce anode copper from
copper ore concentrates. Primary copper smelting begins with copper
mines supplying the ore concentrate (typically 30 percent copper). In
most cases, the moisture is reduced from the ore concentrate in dryers,
and then fed through a smelting furnace where it is melted and reacts
to produce copper matte. One existing smelter is able to feed its
copper concentrate directly to the smelting furnace without prior
drying. Copper matte is a molten solution of copper sulfide mixed with
iron sulfide and is about 60 percent copper. The solution is further
refined using converters to make blister copper, which is approximately
98 percent copper. Converters use oxidation to remove sulfide as sulfur
dioxide (SO<INF>2</INF>) gas and the iron as a ferrous oxide slag. The
majority of the SO<INF>2</INF> gases are sent to a sulfuric acid plant.
The slag is removed, cooled, and often processed again to remove any
residual copper. The blister copper is reduced in the anode furnace to
remove impurities and oxygen, typically by injecting natural gas and
steam, to produce a high purity copper. The molten copper from the
anode refining furnace is poured into molds and cooled to produce solid
copper ingots called anodes. This process is known as casting. The
anodes are sent to a copper refinery, either on-site or at an off-site
location, for further purification using an electrolytic process to
obtain high purity copper that is sold as a product.
The processing units of interest at primary copper smelters,
because of their potential to generate HAP emissions, are the
following: Dryers, smelting furnaces, copper converters, anode refining
furnaces, and, if present, copper holding vessels, slag cleaning
vessels, and matte drying and grinding plants. In addition, fugitive
emissions are sources of HAP at primary copper smelters. The transfer
of matte, converter slag, and blister copper is the primary source of
fugitive emissions.
There are three primary copper smelting facilities in the U.S. that
are subject to the NESHAPs in this review. Two of the facilities
(Asarco and Freeport--both located in Arizona) are major sources of HAP
emissions and are subject to subpart QQQ, the major source NESHAP; the
third facility (Kennecott--located in Utah) is an area source and
subject to subpart EEEEEE, the area source NESHAP.
Two of the facilities (Asarco and Kennecott) use flash smelting
furnaces (the INCO smelting furnace and the Outotec[supreg],
respectively). Flash smelting furnaces consist of blowing fine, dried
copper sulfide concentrate and silica flux with air, oxygen-enriched
air or oxygen into a hot hearth-type furnace. The sulfide minerals in
the concentrate react with oxygen resulting in oxidation of the iron
and sulfur, which produces heat and therefore melting of the solids.
The molten matte and slag are removed separately from the furnace as
they accumulate, and at the facility using the INCO furnace, the matte
is transferred via ladles to the copper converters. The Freeport
facility uses an ISA smelting furnace. The ISA smelt[supreg] process
involves dropping wet feed through a feed port, such that dryers are
not needed. A mixture of air, oxygen, and natural gas is blown through
a vertical lance in the center of the furnace, generating heat and
melting the feed. The molten metal is then tapped from the bottom and
sent to an electric furnace to separate the matte from slag. The slag
is removed from the electric furnace through tapholes and is
transferred to slag pots via ladles. The matte is also removed from the
electric furnace through tapholes and transferred to the converter via
ladles.
At the area source primary copper smelter, molten copper matte
tapped from the Outotec[supreg] smelting furnace is not transferred as
molten material directly to the converting vessel as is performed at
the two major source smelters. Instead, the matte is first quenched
with water to form solid granules of copper matte. These matte granules
are then ground to a finer texture and fed to the flash converting
furnace for the continuous converting of copper. The continuous copper
converter differs significantly in design and operation from the
cylindrical batch converters operated at the other U.S. smelters.
Because there are no transfers of molten material between the smelting
furnace and the continuous copper converter, this technology has
inherently lower potential HAP emissions than a smelter using batch
copper converting technology.

[[Page 1621]]

Molten blister copper is transferred from the converting vessel to
an anode furnace for refining to further remove residual impurities and
oxygen. The blister copper is reduced in the anode refining furnace to
remove oxygen, typically by injecting natural gas and steam to produce
a high purity copper. The molten copper from the anode refining furnace
is poured into molds to produce solid copper ingots called anodes. The
anode copper is sent to a copper refinery, either on-site or at another
location, where it is further purified using an electrolytic process to
obtain the high purity copper that is sold as a product. The copper
refinery is not part of the primary copper smelting source category.
The current NESHAP for major sources (40 CFR part 63, subpart QQQ)
was proposed on April 20, 1998 (63 FR 19582), with a supplement to the
proposed rule published on June 26, 2000 (65 FR 39326). The final rule,
promulgated on June 12, 2002 (67 FR 40478), established PM standards as
a surrogate for HAP metals for copper concentrate dryers, smelting
furnaces, slag cleaning vessels, and existing converters. The major
source NESHAP applies to major sources that use batch copper
converters. Regarding new sources, the NESHAP prohibits batch
converters for new sources, which indirectly means that any new source
would need to have continuous converters, similar to the area source
(Kennecott), or another technology. The converter building is subject
to an opacity limit that only applies during performance testing. A
fugitive dust plan is required to minimize fugitive dust emissions.
Subpart QQQ also establishes requirements to demonstrate initial and
continuous compliance with all applicable emission limitations, work
practice standards, and operation and maintenance requirements. Annual
performance testing is required to demonstrate compliance.
The NESHAP for area sources (40 CFR part 63, subpart EEEEEE)
establishes GACT standards for primary copper smelting area sources and
was proposed on October 6, 2006 (71 FR 59302), and finalized on January
23, 2007 (72 FR 2930). Technical corrections were then published on
July 3, 2007, via direct final rule (72 FR 36363). The affected sources
(i.e., copper concentrate dryers, smelting vessels, converting vessels,
matte drying and grinding plants, secondary gas systems and anode
refining departments) are subject to PM limits as a surrogate for HAP
metals. Compliance must be demonstrated by performance tests conducted
every 2.5 years.

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

For the Primary Copper Smelting source category, the EPA used the
best available data. Initially, emissions and supporting data from the
2017 National Emissions Inventory (NEI) were gathered to develop the
initial draft model input file for the residual risk assessments for
major source primary copper smelters. The NEI is a database that
contains information about sources that emit criteria air pollutants,
their precursors, and HAP. The database includes estimates of annual
air pollutant emission from point, nonpoint, and mobile sources in the
50 states, the District of Columbia, Puerto Rico, and the U.S. Virgin
Islands. The EPA collects this information and releases an updated
version of the NEI database every 3 years. The NEI includes data
necessary for conducting risk modeling, including annual HAP emissions
estimates from individual emission sources at facilities and the
related emissions release parameters.
The Arizona Department of Environmental Quality (ADEQ) provided
2018 emissions test data for both major source primary copper smelters
located in that state, which allowed the EPA to use more current metal
HAP emissions data than what was available in the 2017 NEI in some
cases. The data from ADEQ and the NEI were used to develop an initial
draft risk model input file. This initial draft model file was posted
to the EPA's Primary Copper website on February 26, 2020, and
stakeholders were provided an opportunity to voluntarily review and
provide input regarding the sources of emissions and release parameters
that were reported in the NEI. The Asarco and Freeport facilities
provided input, and the modeling file was finalized. The data include
multiple emissions test reports for PM and HAP metals for point source
emissions from both facilities and seven test reports for emissions
tests conducted in 2018, 2019 and 2020 for process fugitive emissions
for anode refining, smelting furnaces and converters at Freeport.
However, we have no test data for Asarco process fugitive emissions.
The process fugitive emissions estimates for Asarco are based on
emissions factors and process information. Therefore, we have higher
confidence and less uncertainty with our emissions estimates for
Freeport as compared to Asarco. We made an adjustment to the lead
emissions estimates from the anode refining roofline at Freeport by
applying a weighting factor to one of the 2018 test results. This
factor is based on information in the document titled: Technical Report
on Test Method for Roofline Lead Emissions, Operational Influences
During Testing, And Effect of Smelter Reconfiguration, by Trinity
Consultants, December 2018, which is available in the docket for this
action. The data and data sources used to support this action and
additional information on the development of the modeling file are
described in Appendix 1 to the Residual Risk Assessment for the Primary
Copper Smelting Major Source Category in Support of the 2021 Risk and
Technology Review Proposed Rule, which is available in the docket for
this proposed rule (Docket ID No. EPA-HQ-OAR-2020-0430). Additional
information is provided in section II.D below.

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

The EPA used multiple sources of information to support this
proposed action. Before developing the final list of affected
facilities described in section II.B of this preamble, the EPA's
Enforcement and Compliance History Online (ECHO) database was used as a
tool to identify potentially affected facilities with primary copper
smelting operations that are subject to the NESHAPs. The ECHO database
provides integrated compliance and enforcement information for
approximately 800,000 regulated facilities nationwide. The EPA also
reviewed the compliance history on the ADEQ website, active consent
decrees, and consent orders to verify that the facilities were
accurately classified as major sources.
During the technology review, the EPA examined information in the
Reasonably Available Control Technology (RACT)/Best Available Control
Technology (BACT)/Lowest Achievable Emission Rate (LAER) Clearinghouse
(RBLC) to identify technologies in use and determine whether there have
been relevant developments in practices, processes, or control
technologies. The RBLC is a database that contains case specific
information on air pollution technologies that have been required to
reduce the emissions of air pollutants from stationary sources. Under
the EPA's New Source Review (NSR) program, if a facility is planning
new construction or a modification that will significantly increase air
emissions, an NSR permit must be obtained. This central database
promotes the sharing of information among permitting agencies and aids
in case-by-case determinations for NSR permits. The EPA also reviewed
subsequent air toxics regulatory actions for other source categories
and

[[Page 1622]]

information from a virtual site visit at the Freeport plant to
determine whether there have been developments in practices, processes,
or control technologies in the Primary Copper Smelting source category.
The docket for this rulemaking contains the following document which
provides more information on the technology review: Final Technology
Review for the Primary Copper Smelting Source Category.

III. Analytical Procedures and Decision-Making

In this section, the Agency describes the analyses performed to
support the proposed decisions for the RTR and other issues addressed
in this proposal. In this proposed action, pursuant to CAA section
112(f), the EPA conducted a risk review for the major sources in the
primary copper smelting source category. Consistent with CAA section
112(f)(5), the risk review did not cover the area source category.
Therefore, the discussions of risk assessment procedures described in
the following paragraphs apply only to the major source category.
However, pursuant to CAA section 112(d)(6), the EPA conducted a
technology review for the NESHAPs covering both the major source
category and the area source category (40 CFR part 63, subpart EEEEEE).
Therefore, the following discussions of the technology reviews apply to
both major sources and area sources.

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

As discussed in section II.A of this preamble and in the Benzene
NESHAP, in evaluating and developing standards under CAA section
112(f)(2), the Agency applies a two-step approach to determine whether
or not risks are acceptable and to determine if the standards provide
an ample margin of safety to protect public health. As explained in the
Benzene NESHAP, ``the first step judgment on acceptability cannot be
reduced to any single factor'' and, thus, ``[t]he Administrator
believes that the acceptability of risk under section 112 is best
judged on the basis of a broad set of health risk measures and
information.'' (54 FR at 38046). Similarly, with regard to the ample
margin of safety determination, ``the Agency again considers all of the
health risk and other health information considered in the first step.
Beyond that information, additional factors relating to the appropriate
level of control will also be considered, including cost and economic
impacts of controls, technological feasibility, uncertainties, and any
other relevant factors.'' Id.
The Benzene NESHAP approach provides flexibility regarding factors
the EPA may consider in making determinations and how the EPA may weigh
those factors for each source category. The EPA conducts a risk
assessment that provides estimates of the MIR posed by emissions of HAP
that are carcinogens from each source in the source category, the
hazard index (HI) for chronic exposures to HAP with the potential to
cause noncancer health effects, and the hazard quotient (HQ) for acute
exposures to HAP with the potential to cause noncancer health
effects.\2\ The assessment also provides estimates of the distribution
of cancer risk within the exposed populations, cancer incidence, and an
evaluation of the potential for an adverse environmental effect. The
scope of the EPA's risk analysis is consistent with the explanation in
EPA's response to comments on our policy under the Benzene NESHAP:
---------------------------------------------------------------------------

\2\ The MIR is defined as the cancer risk associated with a
lifetime of exposure at the highest concentration of HAP where
people are likely to live. The HQ is the ratio of the potential HAP
exposure concentration to the noncancer dose-response value; the HI
is the sum of HQs for HAP that affect the same target organ or organ
system.

The policy chosen by the Administrator permits consideration of
multiple measures of health risk. Not only can the MIR figure be
considered, but also incidence, the presence of 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 his expertise to
assess available data. It also complies with the Congressional
intent behind the CAA, which did not exclude the use of any
particular measure of public health risk from the EPA's
consideration with respect to CAA section 112 regulations, and
thereby implicitly permits consideration of any and all measures of
health risk which the Administrator, in his judgment, believes are
---------------------------------------------------------------------------
appropriate to determining what will ``protect the public health''.

(54 FR at 38057). Thus, the level of the MIR is only one factor to be
weighed in determining acceptability of risk. The Benzene NESHAP
explained that ``an MIR of approximately one in 10 thousand should
ordinarily be the upper end of the range of acceptability. As risks
increase above this benchmark, they become presumptively less
acceptable under CAA section 112, and would be weighed with the other
health risk measures and information in making an overall judgment on
acceptability. Or, the Agency may find, in a particular case, that a
risk that includes an MIR less than the presumptively acceptable level
is unacceptable in the light of other health risk factors.'' Id. at
38045. In other words, risks that include an MIR above 100-in-1 million
may be determined to be acceptable, and risks with an MIR below that
level may be determined to be unacceptable, depending on all of the
available health information. Similarly, with regard to the ample
margin of safety analysis, the EPA stated in the Benzene NESHAP that:
``EPA believes the relative weight of the many factors that can be
considered in selecting an ample margin of safety can only be
determined for each specific source category. This occurs mainly
because technological and economic factors (along with the health-
related factors) vary from source category to source category.'' Id. at
38061. The Agency also considers the uncertainties associated with the
various risk analyses, as discussed earlier in this preamble, in our
determinations of acceptability and ample margin of safety.
The EPA notes that it has not considered certain health information
to date in making residual risk determinations. At this time, the
Agency does not attempt to quantify the HAP risk that may be associated
with emissions from other facilities that do not include the source
category under review, mobile source emissions, natural source
emissions, persistent environmental pollution, or atmospheric
transformation in the vicinity of the sources in the category.
The EPA understands the potential importance of considering an
individual's total exposure to HAP in addition to considering exposure
to HAP emissions from the source category and facility. The Agency
recognizes that such consideration may be particularly important when
assessing noncancer risk, where pollutant-specific exposure health
reference levels (e.g., reference concentrations (RfCs)) are based on
the assumption that thresholds exist for adverse health effects. For
example, the EPA recognizes that, although exposures attributable to
emissions from a source category or facility alone may not indicate the
potential for increased risk of adverse noncancer health effects in a
population, the exposures resulting from emissions from the facility in
combination with emissions from all of the other sources (e.g., other
facilities) to which an individual is exposed may be sufficient to
result in an increased risk of adverse noncancer health effects. In May
2010, the Science Advisory Board

[[Page 1623]]

(SAB) advised the EPA ``that RTR assessments will be most useful to
decision makers and communities if results are presented in the broader
context of aggregate and cumulative risks, including background
concentrations and contributions from other sources in the area.'' \3\
---------------------------------------------------------------------------

\3\ Recommendations of the SAB Risk and Technology Review
Methods Panel are provided in their report, which is available at:
https://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
---------------------------------------------------------------------------

In response to the SAB recommendations, the EPA incorporates
cumulative risk analyses into its RTR risk assessments. The Agency (1)
conducts facility-wide assessments, which include source category
emission points, as well as other emission points within the
facilities; (2) combines exposures from multiple sources in the same
category that could affect the same individuals; and (3) for some
persistent and bioaccumulative pollutants, analyzes the ingestion route
of exposure. In addition, the RTR risk assessments consider aggregate
cancer risk from all carcinogens and aggregated noncancer HQs for all
noncarcinogens affecting the same target organ or target organ system.
Although the EPA is interested in placing source category and
facility-wide HAP risk in the context of total HAP risk from all
sources combined in the vicinity of each source, the EPA is also
concerned about the uncertainties of doing so. Estimates of total HAP
risk from emission sources other than those that the Agency has studied
in depth during this RTR review would have significantly greater
associated uncertainties than the source category or facility-wide
estimates. Such aggregate or cumulative assessments would compound
those uncertainties, making the assessments too unreliable.

B. How do we perform the technology review?

Our technology review primarily focuses on the identification and
evaluation of developments in practices, processes, and control
technologies that have occurred since the MACT standards were
promulgated. Where we identify such developments, we analyze their
technical feasibility, estimated costs, energy implications, and non-
air environmental impacts. The EPA also considers the emission
reductions associated with applying each development. This analysis
informs our decision of whether it is ``necessary'' to revise the
emissions standards. In addition, the Agency considers the
appropriateness of applying controls to new sources versus retrofitting
existing sources. For this exercise, the EPA considers any of the
following to be a ``development'':
<bullet> Any add-on control technology or other equipment that was
not identified and considered during development of the original MACT
standards;
<bullet> Any improvements in add-on control technology or other
equipment (that were identified and considered during development of
the original MACT standards) that could result in additional emissions
reduction;
<bullet> Any work practice or operational procedure that was not
identified or considered during development of the original MACT
standards;
<bullet> Any process change or pollution prevention alternative
that could be broadly applied to the industry and that was not
identified or considered during development of the original MACT
standards; and
<bullet> Any significant changes in the cost (including cost
effectiveness) of applying controls (including controls the EPA
considered during the development of the original MACT standards).
In addition to reviewing the practices, processes, and control
technologies that were considered at the time the EPA originally
developed the NESHAP, we review a variety of data sources in our
investigation of potential practices, processes, or controls to
consider. The EPA also reviews the NESHAP and the available data to
determine if there are any unregulated emissions of HAP within the
source category, and evaluate the data for use in developing new
emission standards. See sections II.C and II.D of this preamble for
information on the specific data sources that were reviewed as part of
the technology review.

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

In this section, the EPA provides a complete description of the
types of analyses that we generally perform during the risk assessment
process. In some cases, the Agency does not perform a specific analysis
because it is not relevant. For example, in the absence of emissions of
hazardous air pollutants known to be persistent and bioaccumulative in
the environment (PB-HAP), the Agency would not perform a multipathway
exposure assessment. If an analysis is not performed, the Agency will
provide the reason. While we present all of our risk assessment
methods, the Agency only presents risk assessment results for the
analyses actually conducted (see section IV.B of this preamble).
The EPA conducts a risk assessment that provides estimates of the
MIR for cancer posed by the HAP emissions from each source in the
source category, the HI for chronic exposures to HAP with the potential
to cause noncancer health effects, and the HQ for acute exposures to
HAP with the potential to cause noncancer health effects. The
assessment also provides estimates of the distribution of cancer risk
within the exposed populations, cancer incidence, and an evaluation of
the potential for an adverse environmental effect. The eight sections
that follow this paragraph describe how the Agency estimated emissions
and conducted the risk assessment. The docket for this rulemaking
contains the following document which provides more information on the
risk assessment inputs and models: Residual Risk Assessment for the
Primary Copper Smelting Major Source Category in Support of the 2021
Risk and Technology Review Proposed Rule. The methods used to assess
risk (as described in the eight primary steps below) are consistent
with those described by the EPA in the document reviewed by a panel of
the EPA's SAB in 2009 \4\ and described in the SAB review report issued
in 2010. They are also consistent with the key recommendations
contained in that report.
---------------------------------------------------------------------------

\4\ U.S. EPA. Risk and Technology Review (RTR) Risk Assessment
Methodologies: For Review by the EPA's Science Advisory Board with
Case Studies--MACT I Petroleum Refining Sources and Portland Cement
Manufacturing, June 2009. EPA-452/R-09-006. <a href="https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous">https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous</a>.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions
release characteristics?
To create the initial modeling input file, the Agency gathered
actual HAP emissions data from the 2017 NEI and 2018 emissions
estimates provided by ADEQ. The 2019 emissions data for Asarco and
Freeport were not available when the initial modeling input file was
developed. The Asarco plant's smelting operation was shut down for a
significant portion of 2018 due to equipment upgrades. Since the 2019
emissions data for Asarco were not available, the 2017 NEI data were
used for the initial modeling input file. The Freeport plant made
significant upgrades in 2017, so the 2018 emissions data were used for
the initial modeling input file as the best representation of the
current plant configuration. The modeling input file was posted on the
EPA website on February 26, 2020, for

[[Page 1624]]

public review. Asarco and Freeport provided comments, revisions to the
initial modeling file, and supporting documents, which consisted of
2019 emissions data and various performance test reports. The data
provided by both facilities were used to develop the final modeling
input file.
For each NEI record, the EPA reviewed the standard classification
code (SCC) and emission unit and process descriptions, and assigned the
record to one of the emission process groups (i.e., Anode Furnaces;
Anode Refining Roofline; Combustion; Converters; Anode Furnaces and
Converters; Converters Roofline; Dryers, Furnaces, Converters and Acid
Plant; Non-process Fugitives; Rod Plant; Smelting Furnace Roofline;
Smelting Furnace Secondary; Smelting Furnaces and Converters).
If the SCC and emission unit and process descriptions were
ambiguous for a specific NEI record, the Agency used the facility air
permits and flow diagrams to help us assign the appropriate emission
process group. Both facilities have many combined gas streams that vent
to a common control system and/or stack. In those cases, there may be
multiple emissions sources included in the Emission Process Group
Description. For example, at Asarco, the exhaust gases from the two
dryers and flash furnace are vented to the same baghouse. The facility
has a sampling port at the exhaust of the baghouse to measure emissions
during performance testing. The emission sources associated with this
example are represented by ``Dryers and Flash Furnace'' under the
Emission Process Group Description.
The EPA did not conduct a risk review pursuant to section 112(f) of
the CAA for Kennecott since it is an area source subject to GACT
standards (not MACT standards). However, we did obtain emissions
estimates and evaluated some information on ambient monitoring data
near the facility.
Based on reported 2017 estimates to the NEI, Kennecott emits an
estimated 5.6 tpy of lead and 1.6 tpy of arsenic. However, we do not
have any HAP metals emissions test data for Kennecott. Therefore, we
consider these estimates uncertain and we are soliciting comments, data
and additional information regarding these emissions estimates.
With regard to ambient monitoring data, Utah Division of Air
Quality (DAQ) conducted lead monitoring at the Magna station near the
Kennecott copper smelter from January 2010 through June 2017 (see
Figure 18 of the memorandum titled Emissions Data Used for Primary
Copper Smelting Risk and Technology Review (RTR) Modeling Files). At
that time Utah DAQ was able to demonstrate that the likelihood of
violating the National Ambient Air Quality Standard (NAAQS) for lead
was so low, it would no longer be necessary to run the monitor. With
EPA's concurrence, the Magna lead monitor was shut down in June 2017.
Utah DAQ and the EPA continue to evaluate the development of
requirements, such as source emission thresholds, population, and NAAQS
revisions, that may trigger the necessity to resume monitoring lead in
Utah.\5\ Nevertheless, the Agency solicits comments, data and
additional information regarding these ambient monitoring data and how
they should be considered in the context of the EPA's technology review
of the Primary Copper Smelting area source NESHAP.
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\5\ Utah Division of Air Quality 2019 Annual Report. 2019. Utah
Department of Environmental Quality--Air Quality. Available at:
<a href="https://deq.utah.gov/air-quality/annual-reports-division-of-air-quality">https://deq.utah.gov/air-quality/annual-reports-division-of-air-quality</a>.
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2. How did we estimate MACT-allowable emissions?
The available emissions data in the RTR emissions dataset include
estimates of the mass of HAP emitted during a specified annual time
period. These ``actual'' emission levels are often lower than the
emission levels allowed under the requirements of the current MACT
standards. The emissions allowed under the MACT standards are referred
to as the ``MACT-allowable'' emissions. The Agency discussed the
consideration of both MACT-allowable and actual emissions in the final
Coke Oven Batteries RTR (70 FR 19992, 19998-19999, April 15, 2005) and
in the proposed and final Hazardous Organic NESHAP RTR (71 FR 34421,
34428, June 14, 2006, and 71 FR 76603, 76609, December 21, 2006,
respectively). In those actions, the Agency noted that assessing the
risk at the MACT-allowable level is inherently reasonable since that
risk reflects the maximum level facilities could emit and still comply
with national emission standards. The EPA also explained that it is
reasonable to consider actual emissions, where such data are available,
in both steps of the risk analysis, in accordance with the Benzene
NESHAP approach. (54 FR 38044.)
The current Primary Copper Smelting NESHAP specifies numerical
emission standards for each copper concentrate dryer, smelting vessel,
and slag cleaning vessel. Consequently, the MACT-allowable emissions
for each of these emission sources are assumed to be equal to the
numerical emission standard. The NESHAP specifies work practice
standards for fugitive dust sources. Therefore, the Agency believes
that the actual fugitive dust sources emission levels are a reasonable
estimation of the MACT-allowable emissions levels. The current NESHAP
does not include standards for anode refining departments, anode
refining rooflines, converter rooflines and smelting furnace rooflines.
However, the EPA has determined that these sources are part of the
source category and plans to propose MACT standards with this RTR. The
MACT-allowable emissions for our baseline risk assessment for the anode
refining departments, anode refining rooflines, converter rooflines and
smelting furnace rooflines are assumed to be equal to the actual
emissions, which are the estimated emissions prior to implementation of
the proposed MACT standards.
For further details on the assumptions and methodologies used to
estimate MACT-allowable emissions, see Appendix X of the document
titled Emissions Data Used for Primary Copper Smelting Risk and
Technology Review (RTR) Modeling Files, which is available in the
docket for this rulemaking.
3. How do we conduct dispersion modeling, determine inhalation
exposures, and estimate individual and population inhalation risk?
Both long-term and short-term inhalation exposure concentrations
and health risk from the source category addressed in this proposal
were estimated using the Human Exposure Model, Version 1.5.5(HEM-4).\6\
The HEM-4 performs three primary risk assessment activities: (1)
Conducting dispersion modeling to estimate the concentrations of HAP in
ambient air, (2) estimating long-term and short-term inhalation
exposures to individuals residing within 50 kilometers (km) of the
modeled sources, and (3) estimating individual and population-level
inhalation risk using the exposure estimates and quantitative dose-
response information.
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\6\ For more information about HEM-4, go to <a href="https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem">https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem</a>.
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a. Dispersion Modeling
The air dispersion model AERMOD, used by the HEM-4 model, is one of
the EPA's preferred models for assessing air pollutant concentrations
from industrial facilities.\7\ To perform the dispersion

[[Page 1625]]

modeling and to develop the preliminary risk estimates, HEM-4 draws on
three data libraries. The first is a library of meteorological data,
which is used for dispersion calculations. This library includes 1 year
(2016) of hourly surface and upper air observations from 840
meteorological stations. These stations may include multiple years
other than meteorological data from 2016. These meteorological stations
provide coverage of the United States and Puerto Rico. However, for
this source category, the EPA utilized on-site meteorological data
(2012-2013) from non-attainment modeling conducted by ADEQ. A second
library of United States Census Bureau census block \8\ internal point
locations and populations provides the basis of human exposure
calculations (U.S. Census, 2010). In addition, for each census block,
the census library includes the elevation and controlling hill height,
which are also used in dispersion calculations. A third library of
pollutant-specific dose-response values is used to estimate health
risk. These are discussed below.
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\7\ U.S. EPA. Revision to the Guideline on Air Quality Models:
Adoption of a Preferred General Purpose (Flat and Complex Terrain)
Dispersion Model and Other Revisions (70 FR 68218, November 9,
2005).
\8\ A census block is the smallest geographic area for which
census statistics are tabulated.
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b. Risk From Chronic Exposure to HAP
In developing the risk assessment for chronic exposures, the EPA
uses the estimated annual average ambient air concentrations of each
HAP emitted by each source in the source category. The HAP air
concentrations at each nearby census block centroid located within 50
km of the facility are a surrogate for the chronic inhalation exposure
concentration for all the people who reside in that census block. A
distance of 50 km is consistent with both the analysis supporting the
1989 Benzene NESHAP (54 FR 38044) and the limitations of Gaussian
dispersion models, including AERMOD.
For each facility, the Agency calculates the MIR as the cancer risk
associated with a continuous lifetime (24 hours per day, 7 days per
week, 52 weeks per year, 70 years) exposure to the maximum
concentration at the centroid of each inhabited census block. The EPA
calculates individual cancer risk by multiplying the estimated lifetime
exposure to the ambient concentration of each HAP (in micrograms per
cubic meter ([mu]g/m\3\)) by its unit risk estimate (URE). The URE is
an upper-bound estimate of an individual's incremental risk of
contracting cancer over a lifetime of exposure to a concentration of 1
microgram of the pollutant per cubic meter of air. For residual risk
assessments, the EPA generally uses UREs from the EPA's Integrated Risk
Information System (IRIS). For carcinogenic pollutants without IRIS
values, the EPA looks to other reputable sources of cancer dose-
response values, often using California EPA (CalEPA) UREs, where
available. In cases where new, scientifically credible dose-response
values have been developed in a manner consistent with the EPA's
guidelines and have undergone a similar peer review process, the Agency
may use such dose-response values in place of, or in addition to, other
values, if appropriate. The pollutant-specific dose-response values
used to estimate health risk are available at <a href="https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants">https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants</a>.
Arsenic emissions from this source category are driving cancer
risks. Inhalation cancer risks are based on an association between
cumulative arsenic exposure and an increase in lung cancer mortality in
two distinct smelter worker populations.\9\
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\9\ US EPA IRIS; Chemical Assessment Summary for Arsenic
(inorganic) <a href="https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0278_summary.pdf#nameddest=cancerinhal">https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0278_summary.pdf#nameddest=cancerinhal</a>.
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Arsenic is also evaluated for multipathway risks as a PB-HAP based
upon conservative food ingestions rates (i.e., ingestion of fish and
produce) and ingestion of contaminated soil.
To estimate individual lifetime cancer risks associated with
exposure to HAP emissions from each facility in the source category,
the Agency sums the risks for each of the carcinogenic HAP \10\ emitted
by the modeled facility. We estimate cancer risk at every census block
within 50 km of every facility in the source category. The MIR is the
highest individual lifetime cancer risk estimated for any of those
census blocks. In addition to calculating the MIR, we estimate the
distribution of individual cancer risks for the source category by
summing the number of individuals within 50 km of the sources whose
estimated risk falls within a specified risk range. We also estimate
annual cancer incidence by multiplying the estimated lifetime cancer
risk at each census block by the number of people residing in that
block, summing results for all of the census blocks, and then dividing
this result by a 70-year lifetime.
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\10\ The EPA's 2005 Guidelines for Carcinogen Risk Assessment
classifies carcinogens as: ``carcinogenic to humans,'' ``likely to
be carcinogenic to humans,'' and ``suggestive evidence of
carcinogenic potential.'' These classifications also coincide with
the terms ``known carcinogen, probable carcinogen, and possible
carcinogen,'' respectively, which are the terms advocated in the
EPA's Guidelines for Carcinogen Risk Assessment, published in 1986
(51 FR 33992, September 24, 1986). In August 2000, the document,
Supplemental Guidance for Conducting Health Risk Assessment of
Chemical Mixtures (EPA/630/R-00/002), was published as a supplement
to the 1986 document. Copies of both documents can be obtained from
<a href="https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944">https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944</a>. Summing
the risk of these individual compounds to obtain the cumulative
cancer risk is an approach that was recommended by the EPA's SAB in
their 2002 peer review of the EPA's National Air Toxics Assessment
(NATA) titled NATA--Evaluating the National-scale Air Toxics
Assessment 1996 Data--an SAB Advisory, available at https://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
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To assess the risk of noncancer health effects from chronic
exposure to HAP, we calculate either an HQ or a target organ-specific
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is
emitted. Where more than one noncancer HAP is emitted, we sum the HQ
for each of the HAP that affects a common target organ or target organ
system to obtain a TOSHI. The HQ is the estimated exposure divided by
the chronic noncancer dose-response value, which is a value selected
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC, defined as ``an estimate (with
uncertainty spanning perhaps an order of magnitude) of a continuous
inhalation exposure to the human population (including sensitive
subgroups) that is likely to be without an appreciable risk of
deleterious effects during a lifetime'' (<a href="https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary">https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary</a>). In cases where an RfC
from the EPA's IRIS is not available or where the EPA determines that
using a value other than the RfC is appropriate, sometimes the EPA uses
such an alternative value to assess risks. An example of such an
alternative value is the use of the primary NAAQS for lead. The lead
NAAQS is based upon a maximum 3-month average ambient concentration of
0.15 ug/m3. Additional chronic noncancer dose-response values can be a
value from the following prioritized sources, which define their dose-
response values similarly to the EPA: (1) The Agency for Toxic
Substances and Disease Registry (ATSDR) Minimum Risk Level (<a href="https://www.atsdr.cdc.gov/mrls/index.asp">https://www.atsdr.cdc.gov/mrls/index.asp</a>); (2) the CalEPA Chronic Reference
Exposure Level (https://oehha.ca.gov/air/crnr/notice-adoption-air-
toxics-hot-spots-program-guidance-manual-preparation-

[[Page 1626]]

health-risk-0); or (3) as noted above, a scientifically credible dose-
response value that has been developed in a manner consistent with the
EPA guidelines and has undergone a peer review process similar to that
used by the EPA. The pollutant-specific dose-response values used to
estimate health risks are available at <a href="https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants">https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants</a>.
This assessment identified emissions of arsenic and lead as a
chronic noncancer hazard concern for children. Both pollutants impact
brain development. The chronic, noncancer health effect benchmark for
arsenic exposure is based on a decrease in intellectual function and
adverse effects on neurobehavioral development in 10-yr-old children
exposed through drinking water from birth.\11\
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\11\ Wasserman et al. (2004) and Tsai et al. (2003).
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For lead, the NAAQS of 0.15 [micro]g/m\3\ specifies a level of air
quality that protects the most sensitive subpopulation, children, from
adverse effects, such as IQ loss, with an adequate margin of safety
following exposure through inhalation or ingestion of lead previously
emitted into the air.\12\ Several studies were used as the basis for
the standard, including an international pooled analysis of seven
prospective cohort studies (n = 1,333).\13\
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\12\ EPA Final Rule (National Ambient Air Quality Standards for
Lead; November 12, 2008); <a href="https://www.govinfo.gov/content/pkg/FR-2008-11-12/pdf/E8-25654.pdf">https://www.govinfo.gov/content/pkg/FR-2008-11-12/pdf/E8-25654.pdf</a>.
\13\ Lanphear et al. (2005).
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A review of the health effect benchmarks for arsenic and lead
determined that, although the target organ is the same for these two
pollutants, a TOSHI should not be calculated based upon the difference
in exposure duration for the two benchmarks. The chronic REL for
arsenic is an airborne concentration of inorganic arsenic at or below
which no adverse noncancer health effects are anticipated in
individuals indefinitely exposed to that concentration, while the lead
standard is applied to a maximum 3-month rolling average of monitored
lead concentrations.
c. Risk From Acute Exposure to HAP That May Cause Health Effects Other
Than Cancer
For each HAP for which appropriate acute inhalation dose-response
values are available, the EPA also assesses the potential health risks
due to acute exposure. For these assessments, the EPA makes
conservative assumptions about emission rates, meteorology, and
exposure location. As part of our efforts to continually improve our
methodologies to evaluate the risks that HAP emitted from categories of
industrial sources pose to human health and the environment,\14\ the
EPA revised our treatment of meteorological data to use reasonable
worst-case air dispersion conditions in our acute risk screening
assessments instead of worst-case air dispersion conditions. This
revised treatment of meteorological data and the supporting rationale
are described in more detail in Residual Risk Assessment for Primary
Copper Smelting Major Source Category in Support of the 2021 Risk and
Technology Review Proposed Rule and in Appendix 5 of the report:
Technical Support Document for Acute Risk Screening Assessment. This
revised approach has been used in this proposed rule and in all other
RTR rulemakings proposed on or after June 3, 2019.
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\14\ See, e.g., U.S. EPA. Screening Methodologies to Support
Risk and Technology Reviews (RTR): A Case Study Analysis (Draft
Report, May 2017. <a href="https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous">https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous</a>).
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To assess the potential acute risk to the maximally exposed
individual, we use the peak hourly emission rate for each emission
point,\15\ reasonable worst-case air dispersion conditions (i.e., 99th
percentile), and the point of highest off-site exposure. Specifically,
we assume that peak emissions from the source category and reasonable
worst-case air dispersion conditions co-occur and that a person is
present at the point of maximum exposure.
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\15\ In the absence of hourly emission data, the EPA develops
estimates of maximum hourly emission rates by multiplying the
average actual annual emissions rates by a factor (either a
category-specific factor or a default factor of 10) to account for
variability. This is documented in Residual Risk Assessment for
Primary Copper Smelting Major Source Category in Support of the 2020
Risk and Technology Review Proposed Rule and in Appendix 5 of the
report: Technical Support Document for Acute Risk Screening
Assessment. Both are available in the docket for this rulemaking.
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To characterize the potential health risks associated with
estimated acute inhalation exposures to a HAP, we generally use
multiple acute dose-response values, including acute RELs, acute
exposure guideline levels (AEGLs), and emergency response planning
guidelines (ERPG) for 1-hour exposure durations, if available, to
calculate acute HQs. The acute HQ is calculated by dividing the
estimated acute exposure concentration by the acute dose-response
value. For each HAP for which acute dose-response values are available,
the EPA calculates acute HQs. For this source category, acute risks
from arsenic were a concern based upon the 1-hour REL of 0.2 [mu]g/
m\3\. The acute REL is based on developmental effects in mice
(decreased fetal weight, growth retardation, skeletal defects).\16\
---------------------------------------------------------------------------

\16\ Nagymajtenyi et al. 1985.
---------------------------------------------------------------------------

An acute REL is defined as ``the concentration level at or below
which no adverse health effects are anticipated for a specified
exposure duration.'' \17\ Acute RELs are based on the most sensitive,
relevant, adverse health effect reported in the peer-reviewed medical
and toxicological literature. They are designed to protect the most
sensitive individuals in the population through the inclusion of
margins of safety. Because margins of safety are incorporated to
address data gaps and uncertainties, exceeding the REL does not
automatically indicate an adverse health impact. AEGLs represent
threshold exposure limits for the general public and are applicable to
emergency exposures ranging from 10 minutes to 8 hours.\18\ They are
guideline levels for ``once-in-a-lifetime, short-term exposures to
airborne concentrations of acutely toxic, high-priority chemicals.''
Id. at 21. The AEGL-1 is specifically defined as ``the airborne
concentration (expressed as ppm (parts per million) or mg/m\3\
(milligrams per cubic meter)) of a substance above which it is
predicted that the general population, including susceptible
individuals, could experience notable discomfort, irritation, or
certain asymptomatic nonsensory effects. However, the effects are not
disabling and are transient and reversible upon cessation of
exposure.'' Id. at 3. The document also notes that ``Airborne
concentrations below AEGL-1 represent exposure levels that can produce
mild and progressively increasing but transient and nondisabling odor,
taste, and sensory irritation or certain asymptomatic, nonsensory
effects.'' Id. AEGL-2 are defined as ``the airborne concentration
(expressed as parts per million or

[[Page 1627]]

milligrams per cubic meter) of a substance above which it is predicted
that the general population, including susceptible individuals, could
experience irreversible or other serious, long-lasting adverse health
effects or an impaired ability to escape.'' Id.
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\17\ CalEPA issues acute RELs as part of its Air Toxics Hot
Spots Program, and the 1-hour and 8-hour values are documented in
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The
Determination of Acute Reference Exposure Levels for Airborne
Toxicants, which is available at <a href="https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary">https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary</a>.
\18\ National Academy of Sciences, 2001. Standing Operating
Procedures for Developing Acute Exposure Levels for Hazardous
Chemicals, page 2. Available at <a href="https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf">https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf</a>. Note that the
National Advisory Committee for Acute Exposure Guideline Levels for
Hazardous Substances ended in October 2011, but the AEGL program
continues to operate at the EPA and works with the National
Academies to publish final AEGLs (<a href="https://www.epa.gov/aegl">https://www.epa.gov/aegl</a>).
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ERPGs are ``developed for emergency planning and are intended as
health-based guideline concentrations for single exposures to
chemicals.'' \19\ Id. at 1. The ERPG-1 is defined as ``the maximum
airborne concentration below which it is believed that nearly all
individuals could be exposed for up to 1 hour without experiencing
other than mild transient adverse health effects or without perceiving
a clearly defined, objectionable odor.'' Id. at 2. Similarly, the ERPG-
2 is defined as ``the maximum airborne concentration below which it is
believed that nearly all individuals could be exposed for up to one
hour without experiencing or developing irreversible or other serious
health effects or symptoms which could impair an individual's ability
to take protective action.'' Id. at 1.
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\19\ ERPGS Procedures and Responsibilities. March 2014. American
Industrial Hygiene Association. Available at: <a href="https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf">https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf</a>.
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An acute REL for 1-hour exposure durations is typically lower than
its corresponding AEGL-1 and ERPG-1. Even though their definitions are
slightly different, AEGL-1s are often the same as the corresponding
ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from
our acute inhalation screening risk assessment typically result when we
use the acute REL for a HAP. In cases where the maximum acute HQ
exceeds 1, we also report the HQ based on the next highest acute dose-
response value (usually the AEGL-1 and/or the ERPG-1).
For this source category, we developed source category-specific
acute factors ranging from 3 to 10 to estimate peak hourly emissions
from annual emissions estimates for the input to the acute risk
assessment modeling analysis. In general, hourly emissions estimates
were based on batch cycle times for smelting and anode furnaces with an
emission hourly multiplier of 3 applied while road fugitive emissions
were modeled with a default hourly multiplier of 10 times the annual
average. A further discussion of these factors and why they were chosen
can be found in the memorandum, Emissions Data Used for Primary Copper
Smelting Risk and Technology Review (RTR) Modeling Files, available in
the docket for this rulemaking.
In our acute inhalation screening risk assessment, acute impacts
are deemed negligible for HAP for which acute HQs are less than or
equal to 1, and no further analysis is performed for these HAP. In
cases where an acute HQ from the screening step is greater than 1, we
assess the site-specific data to ensure that the acute HQ is at an off-
site location. For this source category, the data refinements employed
consisted of overlaying satellite imagery with off-site polar receptors
to estimate off-site acute impacts. These refinements are discussed
more fully in the Residual Risk Assessment for the Primary Copper
Smelting Major Source Category in Support of the 2021 Risk and
Technology Review Proposed Rule, which is available in the docket for
this source category.
4. How do we conduct the multipathway exposure and risk screening
assessment?
The EPA conducts a tiered screening assessment examining the
potential for significant human health risks due to exposures via
routes other than inhalation (i.e., ingestion). We first determine
whether any sources in the source category emit any HAP known to be
persistent and bioaccumulative in the environment, as identified in the
EPA's Air Toxics Risk Assessment Library (see Volume 1, Appendix D, at
<a href="https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library">https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library</a>).
For the Primary Copper Smelting source category, we identified PB-
HAP emissions of lead, arsenic, mercury and cadmium, so we proceeded to
the next step of the evaluation. Except for lead, the human health risk
screening assessment for PB-HAP consists of three progressive tiers. In
a Tier 1 screening assessment, we determine whether the magnitude of
the facility-specific emissions of PB-HAP warrants further evaluation
to characterize human health risk through upper-end ingestion rates of
(meat, produce, fruits, fish, etc.) based upon a combined farmer and
fisher scenario. To facilitate this step, we evaluate emissions against
previously developed screening threshold emission rates for several PB-
HAP that are based on a hypothetical upper-end screening exposure
scenario developed for use in conjunction with the EPA's Total Risk
Integrated Methodology.Fate, Transport, and Ecological Exposure
(TRIM.FaTE) model. The PB-HAP with screening threshold emission rates
are arsenic compounds, cadmium compounds, chlorinated dibenzodioxins
and furans, mercury compounds, and polycyclic organic matter (POM).
Based on the EPA estimates of toxicity and bioaccumulation potential,
these pollutants represent a conservative list for inclusion in
multipathway risk assessments for RTR rules. (For more details see the
risk assessment report cited above and Volume 1, Appendix D at <a href="https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf">https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf</a>.). In this assessment, we compare the facility-
specific emission rates of these PB-HAP to the screening threshold
emission rates for each PB-HAP to assess the potential for significant
human health risks via the ingestion pathway. We call this application
of the TRIM.FaTE model the Tier 1 screening assessment. The ratio of a
facility's actual emission rate to the Tier 1 screening threshold
emission rate is a screening value (SV).
We derive the Tier 1 screening threshold emission rates for these
PB-HAP (other than lead compounds) to correspond to a maximum excess
lifetime cancer risk of 1-in-1 million (i.e., for arsenic compounds,
polychlorinated dibenzodioxins and furans, and POM) or, for HAP that
cause noncancer health effects (i.e., cadmium compounds and mercury
compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP
or combination of carcinogenic PB-HAP in the Tier 1 screening
assessment exceeds the Tier 1 screening threshold emission rate for any
facility (i.e., the SV is greater than 1), we conduct a second
screening assessment, which we call the Tier 2 screening assessment.
The Tier 2 screening assessment separates the Tier 1 combined fisher
and farmer exposure scenario into fisher, farmer, and gardener
scenarios that retain upper-bound ingestion rates.
In the Tier 2 screening assessment, the location of each facility
that exceeds a Tier 1 screening threshold emission rate is used to
refine the assumptions associated with the Tier 1 fisher and farmer
exposure scenarios at that facility. A key assumption in the Tier 1
screening assessment is that a lake and/or farm is located near the
facility. As part of the Tier 2 screening assessment, we use a U.S.
Geological Survey (USGS) database to identify actual waterbodies within
50 km of each facility and assume the fisher only consumes fish from
lakes within that 50 km zone. We also examine the differences between
local meteorology near the facility and the meteorology used in the
Tier 1 screening assessment. We then adjust the previously developed
Tier 1

[[Page 1628]]

screening threshold emission rates for each PB-HAP for each facility
based on an understanding of how exposure concentrations estimated for
the screening scenario change with the use of local meteorology and the
USGS lakes database.
In the Tier 2 farmer scenario, we maintain an assumption that the
farm is located within 0.5 km of the facility and that the farmer
consumes meat, eggs, dairy, vegetables, and fruit produced near the
facility. We may further refine the Tier 2 screening analysis by
assessing a gardener scenario to characterize a range of exposures,
with the gardener scenario being more plausible in RTR evaluations.
Under the gardener scenario, we assume the gardener consumes home-
produced eggs, vegetables, and fruit products at the same ingestion
rate as the farmer. The Tier 2 screen continues to rely on the high-end
food intake assumptions that were applied in Tier 1 for local fish
(adult female angler at 99th percentile fish consumption \20\) and
locally grown or raised foods (90th percentile consumption of locally
grown or raised foods for the farmer and gardener scenarios \21\). If
PB-HAP emission rates do not result in a Tier 2 SV greater than 1, we
consider those PB-HAP emissions to pose risks below a level of concern.
If the PB-HAP emission rates for a facility exceed the Tier 2 screening
threshold emission rates, we may conduct a Tier 3 screening assessment.
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\20\ Burger, J. 2002. Daily consumption of wild fish and game:
Exposures of high end recreationists. International Journal of
Environmental Health Research, 12:343-354.
\21\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final).
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
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There are several analyses that can be included in a Tier 3
screening assessment, depending upon the extent of refinement
warranted, including validating that the lakes are fishable, locating
residential/garden locations for urban and/or rural settings,
considering plume-rise to estimate emissions lost above the mixing
layer, and considering hourly effects of meteorology and plume-rise on
chemical fate and transport (a time-series analysis). If necessary, the
EPA may further refine the screening assessment through a site-specific
assessment.
In evaluating the potential multipathway risk from emissions of
lead compounds, rather than developing a screening threshold emission
rate, the Agency compares maximum estimated chronic inhalation exposure
concentrations to the level of the current NAAQS for lead.\22\ Values
below the level of the primary (health-based) lead NAAQS are considered
to have a low potential for multipathway risk. For this source category
based upon high modeled annual concentrations of lead from HEM-4, a
refined assessment was conducted to estimate the maximum 3-month
average concentration for lead over multiple years. These refinements
included the use of a post-processer (Lead-POST) in AERMOD to calculate
the maximum 3-month lead concentration for each off-site receptor to
directly compare to the current lead NAAQS standard.\23\
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\22\ In doing so, the EPA notes that the legal standard for a
primary NAAQS--that a standard is requisite to protect public health
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other
things, that the standard provide an ``ample margin of safety to
protect public health''). However, the primary lead NAAQS is a
reasonable measure of determining risk acceptability (i.e., the
first step of the Benzene NESHAP analysis) since it is designed to
protect the most susceptible group in the human population--
children, including children living near major lead emitting
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition,
applying the level of the primary lead NAAQS at the risk
acceptability step is conservative since that primary lead NAAQS
reflects an adequate margin of safety.
\23\ EPA Support Center for Regulatory Atmospheric Modeling site
to access LEADPOST utilized in the Pb NAAQS program: <a href="https://www.epa.gov/scram/air-quality-dispersion-modeling-preferred-and-recommended-models">https://www.epa.gov/scram/air-quality-dispersion-modeling-preferred-and-recommended-models</a>.
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For further information on the multipathway assessment approach,
see the Residual Risk Assessment for the Primary Copper Smelting Major
Source Category in Support of the Risk and Technology Review 2021
Proposed Rule, which is available in the docket for this action.
5. How do we assess risks considering emissions control options?
In addition to assessing baseline inhalation risks and screening
for potential multipathway risks, the EPA also estimates risks
considering the potential emission reductions that would be achieved by
the control options under consideration. In these cases, the expected
emission reductions are applied to the specific HAP and emission points
in the RTR emissions dataset to develop corresponding estimates of risk
and incremental risk reductions.
6. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological
Benchmarks
The EPA conducts a screening assessment to examine the potential
for an adverse environmental effect as required under section
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse
environmental effect'' as ``any significant and widespread adverse
effect, which may reasonably be anticipated, to wildlife, aquatic life,
or other natural resources, including adverse impacts on populations of
endangered or threatened species or significant degradation of
environmental quality over broad areas.''
The EPA focuses on eight HAP, which are referred to as
``environmental HAP,'' in its screening assessment: Six PB-HAP and two
acid gases. The PB-HAP included in the screening assessment are arsenic
compounds, cadmium compounds, dioxins/furans, POM, mercury (both
inorganic mercury and methyl mercury), and lead compounds. The acid
gases included in the screening assessment are hydrochloric acid (HCl)
and hydrogen fluoride (HF).
HAP that persist and bioaccumulate are of particular environmental
concern because they accumulate in the soil, sediment, and water. The
acid gases, HCl and HF, are included due to their well-documented
potential to cause direct damage to terrestrial plants. In the
environmental risk screening assessment, the EPA evaluates the
following four exposure media: terrestrial soils, surface water bodies
(includes water-column and benthic sediments), fish consumed by
wildlife, and air. Within these four exposure media, the Agency
evaluates nine ecological assessment endpoints, which are defined by
the ecological entity and its attributes. For PB-HAP (other than lead),
both community-level and population-level endpoints are included. For
acid gases, the ecological assessment endpoint evaluated is terrestrial
plant communities.
An ecological benchmark represents a concentration of HAP that has
been linked to a particular environmental effect level. For each
environmental HAP, the Agency identified the available ecological
benchmarks for each assessment endpoint and where possible, the
ecological benchmarks at the following effect levels: probable effect
levels, lowest-observed-adverse-effect level, and no-observed-adverse-
effect level. In cases where multiple effect levels were available for
a particular PB-HAP and assessment endpoint, the EPA uses all of the
available effect levels to help us to determine whether ecological
risks exist and, if so, whether the risks could be considered
significant and widespread.
For further information on how the environmental risk screening

[[Page 1629]]

assessment was conducted, including a discussion of the risk metrics
used, how the environmental HAP were identified, and how the ecological
benchmarks were selected, see Appendix 9 of the Residual Risk
Assessment for the Primary Copper Smelting Major Source Category in
Support of the Risk and Technology Review 2021 Proposed Rule, which is
available in the docket for this action.
b. Environmental Risk Screening Methodology
For the environmental risk screening assessment, the EPA first
determined whether any facilities in the Primary Copper Smelting source
category emitted any of the environmental HAP. For the Primary Copper
Smelting source category, the Agency identified emissions of arsenic,
mercury, cadmium and lead. Because one or more of the environmental HAP
evaluated are emitted by at least one facility in the source category,
the Agency proceeded to the second step of the evaluation.
c. PB-HAP Methodology for Environmental Risk Screening
The environmental risk screening assessment includes six PB-HAP:
Arsenic compounds, cadmium compounds, dioxins/furans, POM, mercury
(both inorganic mercury and methyl mercury), and lead compounds. With
the exception of lead, the environmental risk screening assessment for
PB-HAP consists of three tiers. The first tier of the environmental
risk screening assessment uses the same health-protective conceptual
model that is used for the Tier 1 human health screening assessment.
TRIM.FaTE model simulations were used to back-calculate Tier 1
screening threshold emission rates. The screening threshold emission
rates represent the emission rate in tons of pollutant per year that
results in media concentrations at the facility that equal the relevant
ecological benchmark. To assess emissions from each facility in the
category, the reported emission rate for each PB-HAP was compared to
the Tier 1 screening threshold emission rate for that PB-HAP for each
assessment endpoint and effect level. If emissions from a facility do
not exceed the Tier 1 screening threshold emission rate, the facility
``passes'' the screening assessment, and, therefore, is not evaluated
further under the screening approach. If emissions from a facility
exceed the Tier 1 screening threshold emission rate, the EPA evaluates
the facility further in Tier 2.
In Tier 2 of the environmental risk screening assessment, the
screening threshold emission rates are adjusted to account for local
meteorology and the actual location of lakes in the vicinity of
facilities that did not pass the Tier 1 screening assessment. For
soils, the EPA evaluates the average soil concentration for all soil
parcels within a 7.5-km radius for each facility and PB-HAP. For the
water, sediment, and fish tissue concentrations, the highest value for
each facility for each pollutant is used. If emission concentrations
from a facility do not exceed the Tier 2 screening threshold emission
rate, the facility ``passes'' the screening assessment and typically is
not evaluated further. If emissions from a facility exceed the Tier 2
screening threshold emission rate, the EPA evaluates the facility
further in Tier 3.
As in the multipathway human health risk assessment, in Tier 3 of
the environmental risk screening assessment, the Agency examines the
suitability of the lakes around the facilities to support life and
remove those that are not suitable (e.g., lakes that have been filled
in or are industrial ponds), adjust emissions for plume-rise, and
conduct hour-by-hour time-series assessments. If these Tier 3
adjustments to the screening threshold emission rates still indicate
the potential for an adverse environmental effect (i.e., facility
emission rate exceeds the screening threshold emission rate), the
Agency may elect to conduct a more refined assessment using more site-
specific information. If, after additional refinement, the facility
emission rate still exceeds the screening threshold emission rate, the
facility may have the potential to cause an adverse environmental
effect.
To evaluate the potential for an adverse environmental effect from
lead, we compared the average modeled air concentrations (from HEM-4)
of lead around each facility in the source category to the level of the
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable
means of evaluating environmental risk because it is set to provide
substantial protection against adverse welfare effects which can
include ``effects on soils, water, crops, vegetation, man-made
materials, animals, wildlife, weather, visibility and climate, damage
to and deterioration of property, and hazards to transportation, as
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
The environmental risk screening assessment for acid gases
evaluates the potential phytotoxicity and reduced productivity of
plants due to chronic exposure to HF and HCl. The environmental risk
screening methodology for acid gases is a single-tier screening
assessment that compares modeled ambient air concentrations (from
AERMOD) to the ecological benchmarks for each acid gas. To identify a
potential adverse environmental effect (as defined in section 112(a)(7)
of the CAA) from emissions of HF and HCl, the Agency evaluates the
following metrics: the size of the modeled area around each facility
that exceeds the ecological benchmark for each acid gas, in acres and
square kilometers; the percentage of the modeled area around each
facility that exceeds the ecological benchmark for each acid gas; and
the area-weighted average SV around each facility (calculated by
dividing the area-weighted average concentration over the 50-km
modeling domain by the ecological benchmark for each acid gas). For
further information on the environmental screening assessment approach,
see Appendix 9 of the Residual Risk Assessment for the Primary Copper
Smelting Major Source Category in Support of the Risk and Technology
Review 20201 Proposed Rule, which is available in the docket for this
action.
7. How do we conduct facility-wide assessments?
To put the source category risks in context, the EPA typically
examines the risks from the entire ``facility,'' where the facility
includes all HAP-emitting operations within a contiguous area and under
common control. In other words, the Agency examines the HAP emissions
not only from the source category emission points of interest, but also
emissions of HAP from all other emission sources at the facility for
which we have data. For this source category, we conducted the
facility-wide assessment using a dataset compiled from the 2017 NEI and
2018 actual emissions provided by ADEQ. The source category records of
that 2017 and 2018 actual emissions dataset were removed, evaluated,
and updated as described in section II.C of this preamble: What data
collection activities were conducted to support this action? Once a
quality assured source category dataset was available, it was placed
back with the remaining records from the NEI for that facility. The
facility-wide file was then used to analyze risks due to the inhalation
of HAP that are emitted ``facility-wide'' for the populations residing
within 50 km of each facility, consistent with the methods used for the
source category analysis described above. For these

[[Page 1630]]

facility-wide risk analyses, the modeled source category risks were
compared to the facility-wide risks to determine the portion of the
facility-wide risks that could be attributed to the source category
addressed in this proposal. The EPA also specifically examined the
facility that was associated with the highest estimate of risk and
determined the percentage of that risk attributable to the source
category of interest. The Residual Risk Assessment for the Primary
Copper Smelting Major Source Category in Support of the Risk and
Technology Review 20201 Proposed Rule, available through the docket for
this action, provides the methodology and results of the facility-wide
analyses, including all facility-wide risks and the percentage of
source category contribution to facility-wide risks.
8. How do we consider uncertainties in risk assessment?
Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for this proposal. Although
uncertainty exists, we believe that our approach, which used
conservative tools and assumptions, ensures that our decisions are
health and environmentally protective. A brief discussion of the
uncertainties in the RTR emissions dataset, dispersion modeling,
inhalation exposure estimates, and dose-response relationships follows
below. Also included are those uncertainties specific to our acute
screening assessments, multipathway screening assessments, and our
environmental risk screening assessments. A more thorough discussion of
these uncertainties is included in the Residual Risk Assessment for the
Primary Copper Smelting Major Source Category in Support of the Risk
and Technology Review 2021 Proposed Rule, which is available in the
docket for this action. If a multipathway site-specific assessment was
performed for this source category, a full discussion of the
uncertainties associated with that assessment can be found in Appendix
11 of that document, Site-Specific Human Health Multipathway Residual
Risk Assessment Report.
a. Uncertainties in the RTR Emissions Dataset
Although the development of the RTR emissions dataset involved
quality assurance/quality control processes, the accuracy of emissions
values will vary depending on the source of the data, the degree to
which data are incomplete or missing, the degree to which assumptions
made to complete the datasets are accurate, errors in emission
estimates, and other factors. The emission estimates considered in this
analysis generally are annual totals for certain years, and they
generally do not reflect short-term fluctuations during the course of a
year or variations from year to year except in potentially a few cases,
such as the May/June 2018 lead test data for anode refining roof vent
fugitive emissions from the Freeport facility. Nevertheless, the
estimates of peak hourly emission rates for the acute effects screening
assessment were based on emission adjustment factors applied to the
average annual hourly emission rates, which are intended to account for
emission fluctuations due to normal facility operations.
b. Uncertainties in Dispersion Modeling
The EPA recognizes there is uncertainty in ambient concentration
estimates associated with any model, including the EPA's recommended
regulatory dispersion model, AERMOD. In using a model to estimate
ambient pollutant concentrations, the user chooses certain options to
apply. For RTR assessments, we select some model options that have the
potential to overestimate ambient air concentrations (e.g., not
including plume depletion or pollutant transformation). We select other
model options that have the potential to underestimate ambient impacts
(e.g., not including building downwash). Other options that we select
have the potential to either under- or overestimate ambient levels
(e.g., location and year of meteorology data and receptor locations).
On balance, considering the directional nature of the uncertainties
commonly present in ambient concentrations estimated by dispersion
models, the approach we apply in the RTR assessments should yield
unbiased estimates of ambient HAP concentrations. The uncertainties
attributed to dispersion modeling in RTR assessments were assessed by
EPA's Science Advisory Board (SAB) and deemed suitable and
appropriate.\24\ We also note that the selection of meteorology dataset
location could have an impact on the risk estimates. For this source
category, the two facilities being modeled have ambient air toxics
monitors and on-site meteorological stations in place that can be used
to help characterize the uncertainty of the emissions modeling. For the
Freeport facility, we were unable to collect on-site meteorological
data for the 2019 monitor to model comparison; therefore, the model to
monitor evaluation was based upon on-site 2011-2012 meteorological data
with the 2019 monitoring data. This was not an uncertainty for the
Asarco facility, since both model and monitoring comparisons were for
2019. A review of the model to monitor comparisons between the two
site(s) can be found in Appendix 1 of the Residual Risk Assessment for
the Primary Copper Smelting Source Category in Support of the Risk and
Technology Review 2021 Proposed Rule, report which is available in the
docket for this action and Section IV; B-6 of this proposal. As we
continue to update and expand our library of meteorological station
data used in our risk assessments, we expect to reduce this
variability.
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\24\ USEPA, 2009a. Risk and Technology Review (RTR) Risk
Assessment Methodologies: For Review by the EPA's Science Advisory
Board with Case Studies--MACT I Petroleum Refining Sources and
Portland Cement Manufacturing. EPA-452/R-09-006. https://
yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
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c. Uncertainties in Inhalation Exposure Assessment
Although every effort is made to identify all of the relevant
facilities and emission points, as well as to develop accurate
estimates of the annual emission rates for all relevant HAP, the
uncertainties in our emission inventory likely dominate the
uncertainties in the exposure assessment. Some uncertainties in our
exposure assessment include human mobility, using the centroid of each
census block, assuming lifetime exposure, and assuming only outdoor
exposures. For most of these factors, there is neither an under nor
overestimate when looking at the maximum individual risk or the
incidence, but the shape of the distribution of risks may be affected.
With respect to outdoor exposures, actual exposures may not be as high
if people spend time indoors, especially for very reactive pollutants
or larger particles. For all factors, we reduce uncertainty when
possible. For example, with respect to census-block centroids, we
analyze large blocks using aerial imagery and adjust locations of the
block centroids to better represent the population in the blocks. We
also add additional receptor locations where the population of a block
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from
chronic exposures and noncancer effects from both chronic and acute
exposures. Some uncertainties are generally expressed quantitatively,
and others are generally

[[Page 1631]]

expressed in qualitative terms. We note, as a preface to this
discussion, a point on dose-response uncertainty that is stated in the
EPA's 2005 Guidelines for Carcinogen Risk Assessment; namely, that
``the primary goal of EPA actions is protection of human health;
accordingly, as an Agency policy, risk assessment procedures, including
default options that are used in the absence of scientific data to the
contrary, should be health protective'' (the EPA's 2005 Guidelines for
Carcinogen Risk Assessment, page 1-7). This is the approach followed
here as summarized in the next paragraphs.
Cancer UREs used in our risk assessments are those that have been
developed to generally provide an upper bound estimate of risk.\25\
That is, they represent a ``plausible upper limit to the true value of
a quantity'' (although this is usually not a true statistical
confidence limit). In some circumstances, the true risk could be as low
as zero; however, in other circumstances the risk could be greater.\26\
Chronic noncancer RfC and reference dose values represent chronic
exposure levels that are intended to be health-protective levels. To
derive dose-response values that are intended to be ``without
appreciable risk,'' the methodology relies upon an uncertainty factor
(UF) approach,\27\ which considers uncertainty, variability, and gaps
in the available data. The UFs are applied to derive dose-response
values that are intended to protect against appreciable risk of
deleterious effects.
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\25\ IRIS glossary (<a href="https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary">https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary</a>).
\26\ An exception to this is the URE for benzene, which is
considered to cover a range of values, each end of which is
considered to be equally plausible, and which is based on maximum
likelihood estimates.
\27\ See A Review of the Reference Dose and Reference
Concentration Processes, U.S. EPA, December 2002, and Methods for
Derivation of Inhalation Reference Concentrations and Application of
Inhalation Dosimetry, U.S. EPA, 1994.
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Many of the UFs used to account for variability and uncertainty in
the development of acute dose-response values are quite similar to
those developed for chronic durations. Additional adjustments are often
applied to account for uncertainty in extrapolation from observations
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all
acute dose-response values are developed for the same purpose, and care
must be taken when interpreting the results of an acute assessment of
human health effects relative to the dose-response value or values
being exceeded. Where relevant to the estimated exposures, the lack of
acute dose-response values at different levels of severity should be
factored into the risk characterization as potential uncertainties.
Uncertainty also exists in the selection of ecological benchmarks
for the environmental risk screening assessment. The EPA established a
hierarchy of preferred benchmark sources to allow selection of
benchmarks for each environmental HAP at each ecological assessment
endpoint. We searched for benchmarks for three effect levels (i.e., no-
effects level, threshold-effect level, and probable effect level), but
not all combinations of ecological assessment/environmental HAP had
benchmarks for all three effect levels. Where multiple effect levels
were available for a particular HAP and assessment endpoint, we used
all of the available effect levels to help us determine whether risk
exists and whether the risk could be considered significant and
widespread.
For a group of compounds that are unspeciated (e.g., glycol
ethers), we conservatively use the most protective dose-response value
of an individual compound in that group to estimate risk. Similarly,
for an individual compound in a group (e.g., ethylene glycol diethyl
ether) that does not have a specified dose-response value, we also
apply the most protective dose-response value from the other compounds
in the group to estimate risk.
e. Uncertainties in Acute Inhalation Screening Assessments
In addition to the uncertainties highlighted above, there are
several factors specific to the acute exposure assessment that the EPA
conducts as part of the risk review under section 112 of the CAA. The
accuracy of an acute inhalation exposure assessment depends on the
simultaneous occurrence of independent factors that may vary greatly,
such as hourly emissions rates, meteorology, and the presence of a
person. In the acute screening assessment that we conduct under the RTR
program, we assume that peak emissions from the source category and
reasonable worst-case air dispersion conditions (i.e., 99th percentile)
co-occur. We then include the additional assumption that a person is
located at this point at the same time. Together, these assumptions
represent a reasonable worst-case actual exposure scenario. In most
cases, it is unlikely that a person would be located at the point of
maximum exposure during the time when peak emissions and reasonable
worst-case air dispersion conditions occur simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening
Assessments
For each source category, the Agency generally relies on site-
specific levels of PB-HAP or environmental HAP emissions to determine
whether a refined assessment of the impacts from multipathway exposures
is necessary or whether it is necessary to perform an environmental
screening assessment. This determination is based on the results of a
three-tiered screening assessment that relies on the outputs from
models--TRIM.FaTE and AERMOD--that estimate environmental pollutant
concentrations and human exposures for five PB-HAP (dioxins, POM,
mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For
lead, the Agency uses AERMOD to determine ambient air concentrations,
which are then compared to the secondary NAAQS standard for lead. Two
important types of uncertainty associated with the use of these models
in RTR risk assessments and inherent to any assessment that relies on
environmental modeling are model uncertainty and input uncertainty.\28\
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\28\ In the context of this discussion, the term ``uncertainty''
as it pertains to exposure and risk encompasses both variability in
the range of expected inputs and screening results due to existing
spatial, temporal, and other factors, as well as uncertainty in
being able to accurately estimate the true result.
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Model uncertainty concerns whether the model adequately represents
the actual processes (e.g., movement and accumulation) that might occur
in the environment. For example, does the model adequately describe the
movement of a pollutant through the soil? This type of uncertainty is
difficult to quantify. However, based on feedback received from
previous EPA SAB reviews and other reviews, we are confident that the
models used in the screening assessments are appropriate and state-of-
the-art for the multipathway and environmental screening risk
assessments conducted in support of RTRs. For example, the SAB found
that the general methodology of the tiered screening approach and the
use of TRIM.FaTE and AERMOD are appropriate for both multipathway and
ecological screening tools. The SAB noted the simplicity of the air
dispersion treatment in TRIM.FaTE and encouraged the advancement of

[[Page 1632]]

incorporating AERMOD analysis within the TRIM.FaTE framework.\29\
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\29\ USEPA, 2018. Review of EPA's draft technical report entitle
Screening Methodologies to Support Risk and Technology Review (RTR):
A Case Study Analysis; EPA-SAB-18-004. https://yosemite.epa.gov/sab/
sabproduct.nsf/LookupWebReportsLastMonthBOARD/
7A84AADF3F2FE04A85258307005F7D70/$File/EPA-SAB-18-004+.pdf.
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Input uncertainty is concerned with how accurately the models have
been configured and parameterized for the assessment at hand. For Tier
1 of the multipathway and environmental screening assessments, the EPA
configured the models to avoid underestimating exposure and risk. This
was accomplished by selecting upper-end values from nationally
representative datasets for the more influential parameters in the
environmental model, including selection and spatial configuration of
the area of interest, lake location and size, meteorology, surface
water, soil characteristics, and structure of the aquatic food web. The
EPA also assumes an ingestion exposure scenario and values for human
exposure factors that represent reasonable maximum exposures.
In Tier 2 of the multipathway and environmental screening
assessments, we refine the model inputs to account for meteorological
patterns in the vicinity of the facility versus using upper-end
national values, and we identify the actual location of lakes near the
facility rather than the default lake location that we apply in Tier 1.
By refining the screening approach in Tier 2 to account for local
geographical and meteorological data, we decrease the likelihood that
concentrations in environmental media are overestimated, thereby
increasing the usefulness of the screening assessment. In Tier 3 of the
screening assessments, we refine the model inputs again to account for
hour-by-hour plume-rise and the height of the mixing layer. The EPA can
also use those hour-by-hour meteorological data in a TRIM.FaTE run
using the screening configuration corresponding to the lake location.
These refinements produce a more accurate estimate of chemical
concentrations in the media of interest, thereby reducing the
uncertainty with those estimates. The assumptions and the associated
uncertainties regarding the selected ingestion exposure scenario are
the same for all three tiers.
For the environmental screening assessment for acid gases, we
employ a single-tiered approach. We use the modeled air concentrations
and compare those with ecological benchmarks.
For all tiers of the multipathway and environmental screening
assessments, our approach to addressing model input uncertainty is
generally cautious. We choose model inputs from the upper end of the
range of possible values for the influential parameters used in the
models, and we assume that the exposed individual exhibits ingestion
behavior that would lead to a high total exposure. This approach
reduces the likelihood of not identifying high risks for adverse
impacts.
Despite the uncertainties, when individual pollutants or facilities
do not exceed screening threshold emission rates (i.e., screen out), we
are confident that the potential for adverse multipathway impacts on
human health is very low. On the other hand, when individual pollutants
or facilities do exceed screening threshold emission rates, it does not
mean that impacts are significant, only that the Agency cannot rule out
that possibility and that a refined assessment for the site might be
necessary to obtain a more accurate risk characterization for the
source category.
The EPA evaluates the following HAP in the multipathway and/or
environmental risk screening assessments, where applicable: Arsenic,
cadmium, dioxins/furans, lead, mercury (both inorganic and methyl
mercury), POM, HCl, and HF. These HAP represent pollutants that can
cause adverse impacts either through direct exposure to HAP in the air
or through exposure to HAP that are deposited from the air onto soils
and surface waters and then through the environment into the food web.
These HAP represent those HAP for which the Agency can conduct a
meaningful multipathway or environmental screening risk assessment. For
other HAP not included in our screening assessments, the model has not
been parameterized such that it can be used for that purpose. In some
cases, depending on the HAP, the Agency may not have appropriate
multipathway models that allow us to predict the concentration of that
pollutant. The EPA acknowledges that other HAP beyond these that we are
evaluating may have the potential to cause adverse effects and,
therefore, the EPA may evaluate other relevant HAP in the future, as
modeling science and resources allow.

IV. Analytical Results and Proposed Decisions

A. What actions are we taking pursuant to CAA sections 112(d)(2) and
112(d)(3)?

In this proposal, the EPA is proposing the following standards
pursuant to CAA section 112(d)(2) and (3) for the major source NESHAP
(40 CFR part 63, subpart QQQ):
<bullet> PM limits for anode refining point sources at existing and
new sources.
<bullet> PM limits for process fugitive emissions from rooflines of
smelting furnaces at existing and new sources.
<bullet> PM limits for process fugitive emissions from converters
at existing and new sources.
<bullet> PM limits for process fugitive emissions from roof vents
at anode refining operations at existing and new sources.
<bullet> Mercury limits for any existing and new combination of
stacks or other vents from the copper concentrate dryers, converting
department, the anode refining department, and the smelting vessels
affected sources.
<bullet> PM limits for new converters.
The results and proposed decisions based on the analyses performed
pursuant to CAA section 112(d)(2) and (3) are presented below. When
addressing previously unregulated HAP emission sources or unregulated
HAP from previously regulated sources in the proposed rule, we apply
the MACT methodology, as described in section II.A above.
1. Anode Refining Point Source Emissions
The 1998 proposal for primary copper smelting identified anode
refining in the definition of primary copper smelters. However, at that
time, the EPA said there were insufficient data to set an emission
limit for anode refining. Therefore, the Agency did not propose
specific emission standards for anode copper refining operations in the
major source NESHAP at that time. In contrast, the 2007 area source
NESHAP for primary copper smelting (subpart EEEEEE) does include
emissions standards for anode refining. We conclude that anode refining
is part of the source category and emits HAP emissions. Therefore,
pursuant to CAA section 112(d)(2) and (3), the Agency is proposing to
revise the 2002 major source NESHAP to include emission limits for new
and existing anode refining point sources. We have anode refining point
source test data from only one source, and because there are less than
30 sources in the category, the MACT floor is based on the average
performance of the best 5 sources (in this case, the upper predictive
limit (UPL) for the best single source because the Agency only has test
data from one source). Using available test data, we are proposing a
MACT floor PM limit as a surrogate for particulate metal HAP, which
includes, but is not limited to,

[[Page 1633]]

antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead,
manganese, nickel, and selenium compounds. This approach is consistent
with the approach used to limit metal HAP emissions from the other
copper smelting processes. A detailed analysis and documentation of the
MACT floor calculations can be found in the technical document, Draft
MACT Floor Analyses for the Primary Copper Smelting Source Category.
The MACT floor emissions limit was calculated based on the average of
the emissions tests, accounting for variability using the 99 percent
UPL. The MACT floor limit for the anode refining point source emissions
for existing and new sources is 5.8 milligrams per dry standard cubic
meter (mg/dscm).
We identified one BTF option to further reduce PM emissions from
anode refining furnaces point sources. The BTF option would require the
two facilities to each install and operate a wet electrostatic
precipitator (ESP) in addition to their existing controls (baghouses).
We estimated that emissions of lead would be reduced by about 0.8 tpy
and arsenic emissions would be reduced by about 0.3 tpy. For the 2
existing facilities to comply with this BTF standard, we estimated
capital costs of $72 million and annualized costs of $9.6 million for a
cost effectiveness of $8.7 million per ton of HAP metal reduced.
Regarding new sources, the MACT floor control technology would be a
baghouse since the current best performing source is controlled with a
baghouse, and the BTF control option for new sources would also be the
same as existing (i.e., new source BTF option is based on the addition
of a Wet ESP on top of the baghouse). Therefore, we assume the costs
for a new source would also be about the same (i.e., $38 million
capital, with annualized costs of $4.8 million). The Agency cannot
estimate a precise cost effectiveness number because it would depend on
unknown factors (such as concentration of HAP metals in the ore and/or
other input materials used by a new source). Therefore, the Agency
assumes the cost effectiveness for new sources would be roughly the
same as for existing sources described above. Based on this analysis,
the Agency is not proposing this BTF option for existing or new sources
because of the relatively high costs and poor cost effectiveness.
Based on the analyses described above, the Agency is proposing to
revise the 2002 NESHAP to include the following MACT floor-based
emission limits for anode refining point sources:
<bullet> For existing anode refining point sources located at
primary copper smelting facilities, we are proposing a PM emissions
limit of 5.8 mg/dscm.
<bullet> For new anode refining point sources located at primary
copper smelting facilities, we are proposing a PM emissions limit of
5.8 mg/dscm.
We propose that compliance with the PM emissions limit for anode
refining will be demonstrated through an initial compliance test
followed by a compliance test at least once every year.
2. Process Fugitive Roof Vents
The major source NESHAP currently does not include standards for
process fugitive emissions from the rooflines of smelting furnaces,
converters, or anode refining operations, with the exception of an
opacity limit for converter roof vents that applies during testing. We
note that some of these rooflines are among the main sources driving
risks as described in the discussion of the risk results in section
IV.B. Pursuant to CAA section 112(d)(2) and (3), the EPA is proposing
to revise the 2002 NESHAP to include emission limits for rooflines for
smelting furnaces, converters, and anode refining at existing and new
sources.
For smelting furnace and converter rooflines, we evaluated the
potential to establish MACT floor emissions limits for PM, as a
surrogate for HAP metals, which includes, but is not limited to,
antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead,
manganese, nickel, and selenium compounds, based on available test
data. While the Agency only had test data for one of the two facilities
(i.e., Freeport), the Agency used those data for calculating MACT floor
PM limits for converters and smelting furnaces using the UPL
methodology. Establishing PM as a surrogate for HAP metals is
consistent with the approach used to limit metal HAP emissions from the
other copper smelting processes in the current NESHAP and for many
other source categories (i.e., Ferroalloys Production, Integrated Iron
and Steel Manufacturing, Iron and Steel Foundries). Based on our
analyses, we calculated a MACT floor emissions limit of 1.7 lbs/hr PM
for process fugitive emissions for existing and new converter rooflines
and a MACT floor limit of 4.3 lbs/hr PM for existing and new smelting
furnaces rooflines.
The EPA also evaluated BTF PM limits for smelting furnace and
converter rooflines based on the potential addition of capture and
control equipment designed to achieve approximately 90 percent
reduction in process fugitive emissions. With regard to smelting
furnaces, based on available information, we estimate that 1.2 tpy year
of HAP metals are emitted from the smelting flash furnace at Asarco.
Freeport has two smelting furnaces. Freeport already has primary and
secondary capture systems that capture and control process fugitives,
resulting in total estimated HAP metal emissions from both furnaces of
0.626 tpy based on available test data, or about half of the emissions
from Asarco's furnace. Asarco has primary capture and control and some
secondary capture and control, but based on available reported emission
estimates, Asarco emits significantly more HAP metals than Freeport.
For the BTF option, we evaluated the potential to add enhanced,
improved capture and control equipment to achieve about 90 percent
reduction of HAP metal emissions from the Asarco smelting flash furnace
(i.e., reduce estimated HAP metal emissions from 1.2 tpy to about 0.12
tpy). To achieve 90 percent reduction of process fugitives from the
rooflines, the Agency assumes additional secondary capture and/or
enhanced capture (e.g., hooding, duct work, fans, etc.) would be needed
for at least one operation (i.e., matte tapping/pouring). We think
another significant source of fugitives is the material transfer
operation, which includes movement of a large ladle containing very hot
liquid matte from the flash furnace tapping/pouring operation by an
overhead crane to the converters after each tapping/pouring operation.
To capture these fugitive emissions from the material transfer
operations, we assume a roof ventilation capture system would be
needed. We also assume a new baghouse (or other PM collection control
device) would be needed to handle these additional exhaust gases.
Another potential source of fugitives is the pouring/tapping of slag,
but we are assuming 90 percent reduction could be achieved by adding a
secondary capture and/or enhanced capture system to reduce fugitive
emissions from at least one operation, such as the matte tapping/
pouring, without adding capture and control equipment to the slag
operation. Therefore, no costs are estimated for capturing fugitives
from the slag pouring process.
Furthermore, to comply with this BTF option for smelting furnaces,
we estimate Freeport would also need to reduce HAP emissions. If the
standard was based on total emissions from smelting furnaces, we
estimate Freeport would need to achieve 80 percent reduction (e.g.,
from 0.626 to 0.12 tpy,

[[Page 1634]]

which is the target level described above for the Asarco smelting
furnace). To achieve this level of additional reductions of process
fugitive emissions, we assume Freeport would need to install two roof
ventilation capture systems, one for each of its two furnaces. Further
details of this beyond the floor analysis are provided in the technical
memo Evaluation of Beyond-the-floor and Ample Margin of Safety Control
Options and Costs for Process Fugitive Emissions from Smelting Furnaces
and Converters, and for Point Source Emissions from Anode Refining
Furnaces and for the Combined Emissions Stream Emitted from the
Freeport Aisle Scrubber, which is available in the docket for this
action.
Based on this analysis, the Agency estimates the BTF PM limit of
0.12 tpy for existing sources would have total capital costs of
$26,501,600 and annualized costs of $5,443,937 and would achieve about
1.53 tpy reduction of HAP metals, with cost effectiveness of $3,445,529
per ton of HAP metal reduction. With regard to new sources (i.e., new
furnaces), since the MACT Floor limit is based on test data from
Freeport, the Agency assumes the BTF controls for a new furnace would
be similar to the BTF controls described above for Freeport (i.e., need
to install a roof ventilation capture system on top of whatever
controls they need to meet the MACT Floor level of control for each new
furnace). Based on costs estimated for Freeport, and applying this to a
potential new source, the estimated costs for BTF option for a new
furnace would be $3,700,000 capital and annualized costs of $600,000
and achieve about 0.25 tpy metal HAP reduction, with cost effectiveness
of $2,400,000 per ton of HAP. Further information and details regarding
the MACT floor and BTF analyses are provided in the memorandum titled
Draft MACT Floor Analyses for the Primary Copper Smelting Source
Category, and in the costs memo cited above, which are available in the
docket for this proposed action.
With regard to converters, Asarco has three converters and Freeport
has four converters. Asarco already has primary, secondary and tertiary
capture and controls, and the reported total estimated HAP emissions
are 0.0000022 tpy. On the other hand, Freeport has primary and
secondary capture and controls, but no tertiary controls, and the total
estimated HAP emissions from Freeport converters are 0.115 tpy.
Therefore, we considered proposing a BTF option for existing converters
for the source category that would require reductions at Freeport based
on installation of tertiary controls which would be similar to the
tertiary capture and controls on the converters at Asarco or the roof
ventilation capture system described in the BTF analysis above for
Freeport smelting furnaces. Given that all four converters at Freeport
are in the same building, we assume that one such system would be
sufficient to achieve about 80 percent reduction of fugitives. We
assume Freeport could route these additional emissions to current
control devices, since they already have two such control systems
(i.e., scrubbers). Therefore, we are not including an additional
baghouse for this potential BTF control option. Based on the analysis
described above, the Agency estimates this potential BTF standard for
existing converters would have total capital costs of $3,697,200 and
annualized costs of $599,663, and achieve about 0.09 tpy reduction of
HAP metals, with cost effectiveness of $6,662,928 per ton of HAP metal
reduction.
With regard to potential BTF standards for process fugitive
emissions from roof vents for new converters, it is difficult to
determine the appropriate standard because of a number of issues and
uncertainties. First, based on reported emissions described above,
Asarco has substantially lower HAP metal emissions as compared to
Freeport. However, we have no test data for Asarco, so we have low
confidence in these reported emissions estimates. Second, as described
above, the current NESHAP prohibits new sources from using batch
converters. Therefore, we assume any new converter would be a
continuous converter, and we have no test data or even estimates of
process fugitive emissions from continuous converter building roof
vents. Based on this lack of information, we assume the BTF limit and
associated costs for process fugitives for new sources would be the
same as the BTF limit and associated costs for existing sources
described in the paragraph above.
The EPA also evaluated the potential to establish MACT floor
limits, or BTF limits, for HAP metals based on establishing additional
opacity limits in the NESHAP for each affected source. For example, we
considered proposing opacity limits consistent with the state air
permits and opacity limits in the Consent Decree (CD) for Asarco as
potential MACT standards in addition to, or instead of, the MACT floor
PM limits. The opacity limits are not expected to result in emission
reductions. Instead, the opacity would be monitored to ensure that the
process equipment and control devices are operating properly.
Furthermore, there would be no additional costs associated with
establishing these opacity limits, since the limits would be consistent
with what the facilities are already complying with under the state air
permits or a CD. There is variability in opacity limits in the state
air permits and CD and uncertainty as to what specific opacity limits
represent MACT floor and BTF for each of the processes. These opacity
limits are described in detail in the memorandum titled Opacity
Standards for Major Primary Copper Smelting Facilities, which is
available in the docket.
Based on the above analyses, we are proposing the MACT floor PM
emissions limits as a surrogate for metal HAP for converter and
smelting furnace roof vents. The Agency is not proposing the BTF limits
for converters or smelting furnaces because of the high costs and poor
cost effectiveness and uncertainties in the estimates of emissions,
emissions reductions and costs. Furthermore, the Agency is not
proposing the opacity limits at this time due to variability in opacity
limits in the state air permits and CD and uncertainty as to what
specific opacity limits represent MACT floor and BTF for each of the
processes. Nevertheless, the EPA solicits comments regarding the
opacity limits, including whether it would be appropriate to establish
opacity limits (such as the opacity limits in the state air permits and
CD) in the NESHAP in addition to, or instead of, the numeric PM MACT
floor emissions limits described above, and, if so, an explanation as
to how or why these opacity limits reflect MACT floor, or BTF, levels
of control. The Agency also solicits comments, data and other
information regarding the MACT Floor analyses and BTF analyses, and our
proposed determinations described above.
With regard to process fugitive emissions from anode refining roof
vents, we estimate that Freeport emits 5.22 tpy of total metal HAP,
comprised mainly of lead (4.09 tpy) and arsenic (0.622 tpy), and that
Asarco emits 0.1076 tpy of total metal HAP. To develop a proposed
standard for this source, we initially calculated a MACT floor
emissions limit for PM of 15.2 lbs/hr based on available test data and
application of the UPL methodology. For this standard, PM serves as a
surrogate for all particulate HAP metals, similar to the other PM
limits in the NESHAP.
Subsequently, we evaluated a potential BTF PM emissions limit for
the anode refining roof vents, which would be set at a level
approximately 90 percent lower than the MACT floor

[[Page 1635]]

limit. Based on these analyses, which are described in detail in the
Draft MACT Floor Analyses for the Primary Copper Smelting Source
Category memorandum, which is available in the docket, the BTF
emissions limit for PM is 1.6 lbs/hr. Based on available data, to
comply with this BTF limit, we expect the Freeport facility would need
to install improved capture systems, including hoods, ductwork, and
fans, and one additional baghouse to reduce process fugitive emissions
from anode refining roof vents. We anticipate the improved capture
systems would need to be applied to four units, including the two anode
refining furnace pouring operations, the anode casting wheel, and the
holding vessel. However, the facility might identify other methods or
approaches to reduce these emissions, such as applying these equipment
to only a subset of the four units, limiting the input of certain raw
materials that have relatively high HAP metal content (such as acid
plant sludge) into the process, and/or converting their holding vessel
into an enclosed, controlled anode refining furnace. The Agency expects
that the capture, control and/or other measures the facility adopts to
reduce metal HAP emissions from roof vents on anode refining buildings
to meet the BTF limit will also significantly reduce human health risks
(e.g., due to lead and arsenic emissions) as discussed below in section
IV.C.2.
The Agency estimates that total costs for Freeport to comply with
this BTF PM emissions limit would be capital costs of $5,887,000 and
annualized costs of $1,558,000, and would achieve about 4.25 tpy
reduction of lead and arsenic emissions, with cost effectiveness of
$367,000 per ton of lead and arsenic reduction. Lead and arsenic
account for more than 90 percent of the HAP metal emissions from the
roof vents on the anode refining building at Freeport. This cost
effectiveness estimate is within the range of cost effectiveness values
that EPA has historically considered acceptable for lead when compared
to similar prior rulemakings. For example, in the 2012 Secondary Lead
Smelting RTR, EPA accepted a cost effectiveness up to about $1.3M/ton
for metal HAP (mainly Pb, based on 2009 dollars). The EPA's
consideration of the cost effectiveness estimate of $367,000 per ton of
lead and arsenic (noted above) also reflects fact-specific
circumstances for addressing lead and arsenic emissions from the
Primary Copper Smelting source category. For example, in other
instances when the focus is on controlling other pollutants, such as
PM, the agency would compare to other cost-effectiveness values. It is
also important to note that cost effectiveness is but one factor we
consider in assessing the cost of the emission reduction at issue here.
See NRDC v. EPA, 749 F.3d 1055, 1060 (D.C. Cir. April 18, 2014)
(``Section 112 does not command EPA to use a particular form of cost
analysis.''). We also consider other factors in assessing the cost of
the emission reduction as part of our BTF analysis, including, but not
limited to, total capital costs, annual costs and costs compared to
total revenues (e.g., costs to revenue ratios). As explained in section
V.D., the estimated total annualized costs for Freeport are about 0.016
percent of the annual revenue of the facility's ultimate parent company
in 2019. Furthermore, based on Freeport's existing permit, background
information in a consent order with the state of Arizona (which are
available in the docket), and discussions with facility
representatives, improvements to their anode refining capture and
control systems are already being considered. Because estimated HAP
metals emissions from Asarco are much lower, they would not be expected
to incur additional control costs to meet the BTF limit. However,
Asarco would have new costs for compliance testing and recordkeeping
and reporting, as described below. Overall, the EPA concludes that
these costs are not economically significant and the cost effectiveness
is within the range accepted in other NESHAP for these types of HAP
metals (e.g., Secondary Lead RTR Proposed Rule, 76 FR 99, 29032, May
19, 2011, and the Final rule, 77 FR 3, 556, January 5, 2012).
The Agency also considered proposing a BTF lead emissions limit in
addition to, or instead of, the PM limit since lead is the primary HAP
metal emitted from the anode refining roof vents. For example, the
Agency considered a possible lead limit of approximately 0.26 lbs/hr as
a potential BTF MACT limit for anode refining process fugitive
emissions, which is described in the MACT Floor memo cited above.
However, there is some uncertainty with this analysis. It was not clear
how best to apply the EPA's UPL methodology to the available lead
emissions data to appropriately account for variability and determine a
lead UPL limit that would reflect the MACT floor level of control, and
to then subsequently determine what lead limit would represent a 90
percent reduction from the lead MACT Floor. The EPA expects the costs
and reductions for such a lead BTF limit would be the same as the costs
and reductions for the BTF option for PM described in the above
paragraph. If the Agency was to establish such a lead limit instead of
a PM limit, it would also serve as a surrogate for all HAP metals,
similar to the Secondary Lead Smelting NESHAP, which established
emissions limits for lead that serve as surrogates for all particulate
HAP metals. Due to the uncertainties with the analysis of lead
emissions and methodology used to develop the lead UPL limit, the
Agency is not proposing this lead limit at this time. However, the EPA
solicits comments regarding this potential lead limit and whether it
would be appropriate to establish such a lead limit in addition to, or
instead of, the PM limit, and if so, why?
Further information and details regarding the derivation of the
MACT floor and BTF limits are provided in the memorandum titled Draft
MACT Floor Analyses for the Primary Copper Smelting Source Category.
Further information and details regarding the cost estimates for
Freeport to comply with the BTF limits for the anode refining process
fugitives roof vents are described in the memorandum Development of
Estimated Costs for Enhanced Capture and Control of Process Fugitive
Emissions from Anode Refining Operations at Freeport, which is
available in the docket for this proposed action.
Based on the analyses described above, the Agency is proposing a
BTF emissions limit for PM of 1.6 lbs/hr for anode refining process
fugitive emissions at existing and new sources.
In summary, based on the analyses described above, the Agency is
proposing to revise the 2002 NESHAP to include the following emission
limits for process fugitive HAP metal emissions from roof vents of
smelting furnaces, converters, and anode refining processes located at
primary copper smelting facilities, as follows:
<bullet> For existing and new converter operations located at
primary copper smelting facilities, the Agency is proposing a PM
emissions limit of 1.7 lbs/hr for process fugitive roof vents.
<bullet> For existing and new smelting furnaces located at primary
copper smelting facilities, the Agency is proposing a PM emissions
limit of 4.3 lbs/hr for process fugitive roof vents.
<bullet> For existing and new anode refining operations located at
primary copper smelting facilities, the Agency is proposing a PM
emissions limit of 1.6 lbs/hr for process fugitive roof vents.
The Agency is proposing that compliance with these emissions limits
for smelting furnaces, converters and

[[Page 1636]]

anode refining will be demonstrated through an initial compliance test
followed by a compliance test at least once every year. Moreover,
facilities will need to monitor various control parameters (e.g., fan
speed, amperage, pressure drops, and/or damper positioning) on a
continuous basis to ensure the fugitive capture system and controls are
working properly.
With regard to testing and recordkeeping costs, the Agency
estimates Asarco will have total costs of about $95,000 per year for
all the testing and recordkeeping and reporting to demonstrate
compliance with these proposed three new standards for the process
fugitive emissions roof vents for the converters, smelting furnaces and
anode refining processes. As mentioned above, Freeport will have no new
testing costs since they already conduct this testing per ADEQ
requirements.
3. Mercury
As mentioned above, the 2002 NESHAP does not include emission
limits for mercury. The source category emits an estimated 55 pounds of
mercury annually with 45 pounds per year emitted from the Freeport
facility. Because of the temperatures of exhaust gas streams
encountered at primary copper smelting operations, much of the mercury
emitted is in vapor form, not in a particulate form. The vapor form of
mercury is not captured by the controls used to reduce PM emissions.
Therefore, the PM limits do not serve as a surrogate for mercury.
Pursuant to CAA section 112(d)(2) and (3), the Agency is proposing to
revise the 2002 NESHAP to include emission limits for mercury.
Initially the Agency calculated MACT floor limits based on test
data from both of the primary copper smelting facilities. A detailed
analysis and documentation of the MACT floor calculations can be found
in the technical document, Draft MACT Floor Analyses for the Primary
Copper Smelting Source Category, available in the docket.
The MACT floor emissions limit for existing sources was calculated
based on the average of all the emissions tests from both facilities,
accounting for variability using the 99 percent UPL. A MACT floor based
on the 99 percent UPL for the combined facility-wide limit for existing
sources is 0.01 lbs/hr. Based on available data, the Agency concludes
that both facilities would be able to meet the MACT floor limit with no
additional controls.
For new sources, the Agency calculated a MACT floor limit of
0.00097 lbs/hr based on emissions data from the best performing (or
lowest emitting) facility, which is Asarco.
We then evaluated and considered a BTF option to further reduce
emissions of mercury from existing furnaces and converters. Based on
available test data, the Agency estimates that the acid plant is by far
the largest source of mercury emissions at Freeport, accounting for
about 64 percent of the total, with an estimated 29 lbs/yr of mercury
emissions. The BTF option for existing sources would require the
Freeport facility to install and operate an activated carbon injection
(ACI) system and a polishing baghouse on the combined stack emissions
release point, the acid plant. The Agency estimates the ACI system
would achieve approximately 90 percent reduction of mercury from the
acid plant stack (i.e., 26 lbs/yr reduction of mercury). Therefore, the
BTF emissions limit would be 0.0043 lbs/hr, which reflects a 90 percent
reduction from the acid plant portion of the UPL MACT floor level of
0.01 lbs//hr described above.
The EPA estimates that these controls would achieve 26 pounds of
mercury reductions per year (i.e., 90 percent reduction of emissions
from the acid plant), at a capital cost of $1.5 million and annualized
costs of $714,000 (in 2019 dollars) for a cost effectiveness of $27,500
per pound of mercury reduced. After considering both the MACT floor and
BTF options for existing sources, the EPA is proposing the BTF
facility-wide emissions limit for mercury of 0.0043 lbs/hr for existing
sources. The EPA is proposing this BTF limit for mercury because
mercury is a highly toxic, persistent and bioaccumulative HAP and the
estimated cost effectiveness is within the range of cost effectiveness
values the EPA has previously considered acceptable for this HAP after
correcting to dollar year values. For example, in the 2012 Mercury and
Air Toxics (MATS) final rule, EPA finalized a BTF standard for mercury
that had cost effectiveness of $22,496 per pound (based on 2007
dollars), which would be about $27,500 per pound based on 2019 dollars
(see Regulatory Impact Analysis for the Final Mercury and Air Toxics
Standards, December 2011, on pages 1-9 and 1-10, available at: <a href="https://www.epa.gov/mats/epa-announces-mercury-and-air-toxics-standards-mats-power-plants-technical-information">https://www.epa.gov/mats/epa-announces-mercury-and-air-toxics-standards-mats-power-plants-technical-information</a>).
A detailed analysis and documentation of the BTF option for the
Primary Copper Smelting major source NESHAP and cost calculations can
be found in the technical document, Estimated Costs for Beyond-the-
floor Controls for Mercury Emissions from Primary Copper Smelting
Facilities, available in the docket for this action.
With regard to new sources, as described above, the MACT floor for
new sources (i.e., 0.00097 lbs/hr) is already significantly lower than
the BTF limit for existing sources (i.e., 0.0043 lbs/hr). The EPA
evaluated a potential BTF option to further reduce emissions of mercury
from new furnaces and converters. This analysis is very similar to that
described above for existing furnaces and converters, which would
require the installation and operation of at least one ACI system plus
a polishing baghouse on a combined emissions stream from the converter
and furnace. Therefore, the EPA assumes the costs for a beyond the
floor option for a new source could be the same as shown above for
Freeport. With regard to numerical emissions limit, if the Agency
assumes the same percentage reduction from the new source MACT floor
(i.e., 0.00097 lbs/hr) that the Agency described above for existing
sources, that would result in a BTF limit for new sources of 0.00042
lbs/hr.
However, with regard to reductions, it is impossible to accurately
estimate potential reductions in mercury from a new source without
knowing more information regarding a potential new source. For example,
mercury emissions are highly dependent on the concentration of mercury
in the ore and mercury concentrations can vary significantly across
different ore bodies. If the EPA assumes a new source would have
similar ore as Asarco, which has much lower mercury emissions compared
to Freeport, the costs for controls could be similar to those estimated
for Freeport above. However, the emissions reductions would be far
lower, and therefore the controls would probably not be cost effective.
If, on the other hand, the ore was similar to Freeport's, it may not be
feasible for such a facility to achieve a limit of 0.00042 lbs/hr) with
these types of controls. For example, if such a facility had
characteristics similar to Freeport, they would likely need to achieve
far greater reductions than 90 percent from the acid plant to achieve a
limit of 0.00042 lbs/hr, which would require additional controls beyond
the ACI system and polishing baghouse described above.
Given these uncertainties described above, and the fact that the
new source MACT floor limit (i.e., 0.00097 lbs/hr) is already
significantly lower than the BTF limit for existing sources of 0.0043
lbs/hr, the Agency is proposing a MACT floor limit for mercury for new
sources of 0.00097 lbs/hr. More details are provided in the memorandums
titled

[[Page 1637]]

Draft MACT Floor Analyses for the Primary Copper Smelting Source
Category and Estimated Costs for Beyond-the-floor Controls for Mercury
Emissions from Primary Copper Smelting Facilities, which are available
in the docket for this action.
Based on the analysis described above, the Agency is proposing to
revise the 2002 NESHAP to include the following emission limits for
mercury:
<bullet> For existing primary copper smelting facilities, the
Agency is proposing a facility-wide BTF emissions limit for mercury of
0.0043 lbs/hr.
<bullet> For new primary copper smelting facilities, the Agency is
proposing a facility-wide MACT Floor emissions limit for mercury of
0.00097 lbs/hr.
The EPA is proposing that compliance with the mercury emissions
limits for existing sources will be demonstrated through an initial
compliance test for each of the affected sources (e.g., furnaces,
converters, anode refining) within 3 years of publication of the final
rule followed by a compliance test at least once every year. The actual
number of tests required will depend on the specific configurations of
the emissions capture and control equipment and number of release
points at each facility. For affected facilities that commence
construction or reconstruction after January 11, 2022, owners or
operators must comply with all requirements of the subpart, including
all the amendments being proposed, no later than the effective date of
the final rule or upon startup, whichever is later.
The EPA solicit comments, information and data regarding the
proposed standards for mercury, and the relevant technical analyses
described above, as well as the proposed compliance dates and testing
requirements.
4. New Source Limits for Converters in the Major Source NESHAP
The current requirement for new copper converters is that the
NESHAP prohibits the use of batch copper converters. By default, new
copper converters covered by the NESHAP would need to be continuous
converters, or some other unknown non-batch converter technology, but
the rule does not include an actual standard for new converters.
Therefore, pursuant to CAA section 112(d)(2) and (3), the Agency is
proposing to revise the 2002 NESHAP to include emission limits for new
converters. We note that there are no existing continuous converters in
the major source category, and, therefore, the Agency is not
establishing an emissions limit for existing sources. The Agency is
proposing a PM with a diameter less than 10 micrometers
(PM<INF>10</INF>) emissions limit as a surrogate for metal HAP based on
PM<INF>10</INF> test data from the Kennecott facility which is an area
source subject to 40 CFR part 63, subpart EEEEEE, area source rule.
Therefore, the limit is based on the performance of the best similar
source, which is the Kennecott primary copper smelting facility. The
proposed input-based emissions limit would require the discharge of
total PM<INF>10</INF> to be no greater than 0.031 pounds of
PM<INF>10</INF> per ton of copper concentrate feed charged to the
smelting vessel. A detailed discussion of the selection of the new
source limit can be found in the preamble to the proposed rule for
subpart EEEEEE (71 FR 59307, 59310, October 6, 2006). The calculation
of the limit of 0.031 lbs of PM<INF>10</INF> per ton of copper
concentrate feed is described in the technical memo titled: Draft MACT
Floor Analyses for the Primary Copper Smelting Source Category.
We then evaluated whether there are any potential BTF options to
further limit PM<INF>10</INF> emissions from new converters; however,
we did not identify any BTF options. Therefore, we are proposing a
limit of 0.031 pounds of PM<INF>10</INF> per ton of copper concentrate
feed charged to the smelting vessel.
The EPA proposes that compliance with the PM<INF>10</INF> emissions
limit for new converters would be demonstrated through an initial
compliance test followed by a compliance test at least once every year.

B. What are the results of the risk assessment and analyses?

1. Chronic Inhalation Risk Assessment Results
Table 1 of this preamble provides a summary of the results of the
inhalation risk assessment for the source category. The two facilities
in this major source category are located in Arizona in a rural, desert
environment that is, for the most part, sparsely populated. More
detailed information on the risk assessment can be found in the
document titled Residual Risk Assessment for the Primary Copper
Smelting Major Source Category in Support of the Risk and Technology
Review 2021 Proposed Rule, available in the docket for this rule.

Table 1--Primary Copper Smelting Major Source Category Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
Maximum individual Population at Annual cancer Maximum noncancer HI and 3-month lead Maximum screening
cancer risk (in 1 increased risk of incidence (cases per concentration (ug/m\3\) \3\ acute noncancer HQ
million) \2\ based cancer >= 1-in-1 year) based on . . . ---------------------------------------------- \4\ based on . . .
Number of on . . . million based on . . ---------------------- ---------------------
facilities \1\ ---------------------- .
---------------------- Actual Allowable Actual emissions Allowable emissions
Actual Allowable Actual Allowable emissions emissions Actual emissions
emissions emissions emissions emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
2................. 80 90 26,125 29,001 0.003 0.003 HI = 1 (arsenic) HI = 1 (arsenic) HQ (REL) = 7
developmental. developmental. (Arsenic).
......... ......... ......... ......... ......... ......... Pb Conc: 0.17........ Pb Conc: 0.24 .......
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer and noncancer risk due to arsenic emissions from the source category, 71 percent from the anode refining
roofline at Freeport and 23 percent from anode furnaces and converters point source emissions from the Aisle Scrubber at Freeport.
\3\ The max 3-month off-site lead concentration is compared to the lead (Pb) NAAQS standard of 0.15 ug/m\3\ based upon actual and allowable emissions
from the source category. The Pb NAAQS standard was developed to address all exposure pathways (inhalation and ingestion).
\4\ The maximum estimated off-site acute exposure concentration was divided by available short-term dose-response values to develop an array of HQ
values. HQ values shown use the lowest available acute dose-response value, which in most cases is the REL. There are no other acute health benchmarks
for arsenic other than the 1-hour REL.

Results of the inhalation risk assessment based on actual emissions
indicate that the cancer MIR is 80-in-1 million. The total estimated
cancer incidence from this source category is 0.003 excess cancer cases
per year, or one excess case every 333 years, with arsenic compounds
contributing 95 percent of the cancer incidence for the source
category. Approximately 26,125 people of the 46,460 people in the model
domain are estimated to have cancer risks above 1-in-1 million from HAP
emitted from this source category. The HEM-4 model predicted the
maximum chronic noncancer HI value for the source category is equal to
1 (developmental), driven by emissions of

[[Page 1638]]

arsenic from the anode refining roofline at Freeport and the anode
furnaces and secondary converter point source emissions emitted through
the Aisle Scrubber at Freeport.
Results of the inhalation risk assessment based on MACT-allowable
emissions indicate that the cancer MIR is 90-in-1 million. The total
estimated cancer incidence from this source category is 0.003 excess
cancer cases per year, or one excess case every 333 years, with arsenic
contributing 90 percent and cadmium contributing 8 percent of the
cancer incidence for the source category. Approximately 29,001 people
are estimated to have cancer risks above 1-in-1 million from exposure
to HAP emissions allowed under the NESHAP. The HEM-4 model predicted
the maximum chronic noncancer HI value for the source category is equal
to 1 (developmental), driven by emissions of arsenic from the anode
refining roofline and the anode furnaces and converters. No individuals
are estimated to have exposures that result in a noncancer HI above 1
at allowable emission rates.
A refined modeling analysis was conducted at the facility with the
highest annual concentration of lead to characterize ambient
concentrations of lead for 3-month intervals. The maximum 3-month
concentration was predicted for each off-site receptor. The
concentrations were then compared to the Lead (Pb) NAAQS of 0.15 ug/
m\3\. The maximum 3-month off-site modeled concentration was 0.17 ug/
m\3\ for actual emissions and 0.24 ug/m\3\ for allowable emissions, and
these results occurred near the Freeport facility. The lead standard is
based on exposure to all pathways (inhalation and ingestion) due to
lead emitted to the air and includes an adequate margin of safety to be
protective of all sub-populations at risk, especially children. Lead
concentrations above the standard increase the risk of developmental
effects for children. Model results indicate that, based on actual
emissions, a single census block (about five people) has the potential
to be exposed to lead concentrations greater than the lead NAAQS. For
allowable emissions, the analysis predicts that eight census blocks
(about 50 people) have modeled lead concentrations greater than the
lead NAAQS. While the EPA examines the potential for lead risks and
exposure by comparing ambient levels directly to the NAAQS, the
noncancer risks predicted for this category from arsenic are also
associated with developmental effects. Thus, while the Agency did not
combine the risk of developmental effects from exposure to lead with
the hazard associated with exposure to arsenic, the Agency would expect
their combined hazard to be greater than each of the individual
exposures and hazards presented above.
2. Screening Level Acute Risk Assessment Results
To better characterize the potential health risks associated with
estimated worst-case 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, the Agency examined a wider range of
available acute health metrics than the Agency does for our chronic
risk assessments. This is in acknowledgement that there are generally
more data gaps and uncertainties in acute reference values than there
are in chronic reference values. By definition, the acute REL
represents a health-protective level of exposure, with effects not
anticipated below those levels, even for repeated exposures. However,
the level of exposure that would cause health effects is not
specifically known. Therefore, when an REL is exceeded and an AEGL-1 or
ERPG-1 level is available (i.e., levels at which mild, reversible
effects are anticipated in the general public for a single exposure),
the Agency typically uses them as an additional comparative measure, as
they provide an upper bound for exposure levels above which exposed
individuals could experience effects. As the exposure concentration
increases above the acute REL, the potential for effects increases.
A review of all modeled off-site receptors for the Primary Copper
Smelting source category identified exceedance of the 1-hour REL for
arsenic, resulting in an HQ of 7 for arsenic. This is for actual
baseline emissions. Satellite imagery for this location identifies it
as a residential location approximately 4,200 meters northeast of the
Freeport facility. It is also important to note that the primary source
of the arsenic emissions from the anode furnace/converter and anode
refining roofline was modeled with an hourly emissions multiplier of 3
times the annual average emissions rate. There are no AEGL or ERPG
levels available for arsenic. No other HAP exposure concentrations
exceeded acute benchmarks. Further details on the acute HQ estimates
are provided in Appendix 10 of the risk report for this source
category.
3. Multipathway Risk Screening
For this source category both facilities reported emissions of
lead, which are compared to the lead NAAQS, and emissions of PB-HAP,
which are compared to the Tier 1 screening threshold emission rate for
each PB-HAP based upon a combined fisher/farmer scenario with upper-
bound ingestion rates. The two facilities within this source category
both reported emissions of carcinogenic PB-HAP (arsenic) and emissions
of non-carcinogenic PB-HAP (cadmium and mercury) that exceeded their
respective Tier 1 screening threshold emission rates. For facilities
that exceed the Tier 1 multipathway screening threshold emission rate
for one or more PB-HAP, we use additional facility site-specific
information to perform a Tier 2 multipathway screening assessment. For
the Tier 2 screening, the farmer and fisher scenarios are not combined
as they are in the Tier 1 screening. Instead, the farmer and fisher
scenarios are treated as separate individuals with the fisher scenario
based upon modeled impacts to local lakes within 50 kilometers of the
facility. Further details on the tiered multipathway screening
methodology can be found in Appendix 6 of the Residual Risk Assessment
for the Primary Copper Smelting Major Source Category in Support of the
Risk and Technology Review 2021 Proposed Rule.
For arsenic, both facilities had Tier 2 SVs (cancer) greater than
1, with a maximum SV of 3,000 for the farmer scenario, a maximum SV of
1,000 for the rural gardener scenario, and a maximum SV of 100 for the
fisher scenario. For cadmium, the Tier 2 screening assessment for both
the farmer and gardener (rural) scenarios resulted in maximum Tier 2
SVs (noncancer) of 4. For the fisher scenario, Tier 2 noncancer SVs
were greater than 1 for mercury compounds and cadmium compounds for one
facility with a maximum noncancer SV of 20 for mercury and the maximum
noncancer SV of 10 for cadmium.
Based upon these results, a Tier 3 screening assessment was
conducted for both the fisher and gardener (rural) scenarios. A Tier 3
screening analysis was performed for arsenic, cadmium, and mercury
emissions. In the Tier 3 screen for the fisher scenario, lakes near the
facilities were reviewed on aerial photographs. As a result of this
assessment, the features that were initially identified as lakes
driving the Tier 2 screening risks for the fisher scenario were found
to be tailings basins (not lakes), which are not fishable. After the
tailings basins were removed from the fisher scenario analysis, the
maximum cancer SV for arsenic emissions was 30, the maximum noncancer
SV for mercury emissions

[[Page 1639]]

was 4, and the maximum noncancer SV for cadmium emissions was 4.
The Tier 3 gardener (rural) scenario was refined with the placement
of the garden at the MIR residential receptor location approximately 4
km northeast of the facility versus the worst-case near-field location.
Based on these Tier 3 refinements to the gardener scenario, the maximum
Tier 3 cancer SV of 1,000 (rounded to 1 significant figure) remained
the same for arsenic emissions, while the maximum noncancer SV
decreased from 4 to 3 for cadmium emissions. An exceedance of a
screening threshold emission rate or SV in any of the tiers cannot be
equated with a risk value or an HQ (or HI). Rather, it represents a
high-end estimate of what the risk or hazard may be. For example, an SV
of 2 for a non-carcinogen can be interpreted to mean that the Agency is
confident that the HQ would be lower than 2. Similarly, a Tier 2 cancer
SV of 7 means that we are confident that the cancer risk is lower than
7-in-1 million. Our confidence comes from the conservative, or health-
protective, assumptions encompassed in the screening tiers: The Agency
chooses inputs from the upper end of the range of possible values for
the influential parameters used in the screening tiers, and the Agency
assumes that the exposed individual exhibits ingestion behavior that
would lead to a high total exposure.
The EPA determined that it is not necessary to go beyond the Tier 3
lake and gardener analysis or conduct a site-specific assessment for
arsenic, cadmium, and mercury. The EPA compared the Tier 2 screening
results to site-specific risk estimates for five previously assessed
source categories. These are the five source categories, assessed over
the past 4 years, which had characteristics that make them most useful
for interpreting the Primary Copper Smelting screening results. For
these source categories, the EPA assessed fisher and/or gardener risks
for arsenic, cadmium, and/or mercury by conducting site-specific
assessments. The EPA used AERMOD for air dispersion and Tier 2 screens
that used multi-facility aggregation of chemical loading to lakes where
appropriate. These assessments indicated that cancer and noncancer
site-specific risk values were at least 50 times lower than the
respective Tier 2 screening values for the assessed facilities, with
the exception of noncancer risks for cadmium for the gardener scenario,
where the reduction was at least 10 times (refer to EPA Docket ID: EPA-
HQ-OAR-2017-0015 and EPA-HQ-OAR-2019-0373 for a copy of these
reports).\30\
---------------------------------------------------------------------------

\30\ EPA Docket records (EPA-HQ-OAR-2017-0015): Appendix 11 of
the Residual Risk Assessment for the Taconite Manufacturing Source
Category in Support of the Risk and Technology Review 2019 Proposed
Rule; Appendix 11 of the Residual Risk Assessment for the Integrated
Iron and Steel Source Category in Support of the Risk and Technology
Review 2019 Proposed Rule; Appendix 11 of the Residual Risk
Assessment for the Portland Cement Manufacturing Source Category in
Support of the 2018 Risk and Technology Review Final Rule; Appendix
11 of the Residual Risk Assessment for the Coal and Oil-Fired EGU
Source Category in Support of the 2018 Risk and Technology Review
Proposed Rule; and EPA Docket: (EPA-HQ-OAR-2019-0373): Appendix 11
of the Residual Risk Assessment for Iron and Steel Foundries Source
Category in Support of the 2019 Risk and Technology Review Proposed
Rule.
---------------------------------------------------------------------------

Based on our review of these analyses, if the Agency was to perform
a site-specific assessment for the Primary Copper Smelting Source
Category, the Agency would expect similar magnitudes of decreases from
the Tier 2 SVs. As such, based upon the conservative nature of the
screens and the level of additional refinements that would go into a
site-specific multipathway assessment, were one to be conducted, we are
confident that the HQ for ingestion exposure, specifically cadmium and
mercury through fish ingestion, is less than 1. For arsenic, maximum
cancer risk posed by fish ingestion would also be reduced to levels
below 1-in-1 million, and maximum cancer risk under the rural gardener
scenario would decrease to 20-in-1 million or less. Also, based upon
the arid climate of the area and the hypothetical nature/location of
the garden, estimated risks from this scenario seem unlikely. Further
details on the Tier 3 screening assessment can be found in Appendix 10-
11 of Residual Risk Assessment for the Primary Copper Smelting Major
Source Category in Support of the Risk and Technology Review 2021
Proposed Rule.
In evaluating the potential for adverse health effects from
emissions of lead, the EPA compared modeled maximum 3-month lead
concentrations to the secondary NAAQS level for lead of (0.15 [mu]g/
m\3\) over a 2-year period. The highest off-site 3-month average lead
concentration based upon actual emissions was 0.17 [mu]g/m\3\. The
highest concentration based on allowable emissions was 0.24 [mu]g/m\3\.
Both results are above the lead NAAQS standard, indicating a potential
for adverse health effects from multipathway exposure to lead. For
further information on the modeling and monitoring analysis for lead
refer to section IV.B.1 (Chronic Inhalation Risk Assessment Results)
and section IV.B.6 (Monitor to Model Analysis for Arsenic and Lead).
4. Environmental Risk Screening Results
As described in section III.A of this document, the Agency
conducted an environmental risk screening assessment for the primary
copper source category for the following pollutants: Arsenic, cadmium,
and mercury. In the Tier 1 screening analysis for PB-HAP (other than
lead, which was evaluated differently), arsenic, cadmium, divalent
mercury and methyl mercury exceeded at least one ecological benchmark,
requiring a Tier 2 screen.
A Tier 2 screening assessment was performed for arsenic, cadmium,
divalent mercury and methyl mercury. Arsenic, divalent mercury, and
methyl mercury had no Tier 2 exceedances for any ecological benchmark.
Two facilities contributing emissions to the same lake had cadmium
emissions that resulted in Tier 2 exceedances for fish no-observed-
adverse-effect level (avian piscivores), fish geometric-maximum-
allowable-toxicant level (avian piscivores), and fish lowest-observed-
adverse-effect level (avian piscivores) benchmarks with a maximum SV of
3.\31\
---------------------------------------------------------------------------

\31\ The two facilities in the multipathway analysis are within
the same model domain and contribute cadmium emissions to a common
lake with the Freeport facility contributing >99 percent of the
cadmium loading to the target lake (USGS ID:26665).
---------------------------------------------------------------------------

A Tier 3 screening analysis was performed for cadmium emissions. In
the Tier 3 screen, lakes near the facilities were reviewed on aerial
photographs. As a result of this assessment, the waterbody that was
initially identified as a lake that was driving the Tier 2
environmental screening risks for cadmium was found to be a tailings
basin and was removed from the analysis. After environmental impacts
that had been estimated for the tailings basin were removed from the
analysis, there were no exceedances of cadmium environmental screening
benchmarks in Tier 3. For lead, the Agency estimated an exceedance of
the secondary lead NAAQS at one census block at a lead concentration of
0.17 ug/m\3\. The exceeded census block constitutes less than 0.1
percent of the modeled area around the facility. Therefore, based on
the limited extent of the lead exceedance and the other results of the
environmental risk screening analysis, the Agency does not expect an
adverse environmental effect as a result of HAP emissions from this
source category.

[[Page 1640]]

5. Facility-Wide Risk Results
The source category includes all the emissions at the facility.
Thus, the facility-wide risk is the same as the risk posed by the
actual emissions from the source category, refer to Table 1, with no
change in incidence or risk drivers.
6. Monitor To Model Analysis for Arsenic and Lead
A monitor to model comparison analysis was conducted for the
monitors located at both primary copper smelting facilities to
characterize the effectiveness of the emissions modeling and for
purposes of risk characterization. Monitoring data collected from both
sites represent current process operations at the facilities including
process fugitives as well as background contributions from historic
activity such as road dust and re-entrainment. A review of emission
inventories for the area indicates both plants are the primary
contributor of arsenic and lead emissions for their locations.
Monitoring samples are collected on a one in 6-day schedule for a 24-
hour continuous period. This schedule and the number of active source-
driven monitors provide an indication of what emission sources may be
contributing to the monitor but still do not provide enough temporal
resolution to apportion the emissions to a specific source. Because the
sample is collected over a 24-hour period, this apportionment is
further complicated by factors such as varying surface winds (wind
speed and wind direction) that occur throughout the day as well as
unexpected changes in production or upset events that may occur at the
plant.
The Hayden area of Gila and Pinal Counties in Arizona is currently
classified as nonattainment for the 2010, 1-hour primary SO<INF>2</INF>
NAAQS; 2008 lead NAAQS; and 1987 PM<INF>10</INF> NAAQS. Asarco is the
only source of lead and SO<INF>2</INF> emissions in the Hayden
nonattainment area. Emission reductions required under a CD with the
EPA were designed to bring the Asarco facility into compliance with the
NESHAP by December 2018. In addition, revisions to the state
implementation plan (SIP) were intended to provide for attainment with
the SO<INF>2</INF> and lead NAAQS by the attainment dates of October
2018 and October 2019, respectively. A review of 2019 monitoring data
from four total suspended particulates (TSP) lead monitors and five
particulate (PM<INF>10</INF>) monitors in the area around Asarco that
measure arsenic and other metals were compared to model results. The
modeled concentrations predicted in the above analysis for Asarco were
two to five times lower than the monitor concentrations. Refer to Table
2 for comparisons and the respective ambient air concentrations and
risk values. Monitor 23 (4th Street and Hillcrest Avenue) was
identified as the critical monitor due to its close proximity (within
100 meters) of the modeled MIR location for Asarco. Based upon the 2019
arsenic monitoring data from Monitor 23, excess cancer risks were equal
to 90-in-1 million compared to a model-predicted monitor value of 50-
in-1 million for Asarco. Monitor values also indicate a chronic
noncancer HQ of 1 from arsenic.
The Miami area of Gila County, Arizona, was classified as
nonattainment for the 2010, 1-hour primary SO<INF>2</INF> NAAQS in
August 2013. Freeport is the only source of lead and SO<INF>2</INF>
emissions in the Miami nonattainment area. Emission reductions required
under a revision to the SIP were designed to provide for attainment of
the SO<INF>2</INF> NAAQS by October 2018. The 2019 monitoring data from
the lead NAAQS (TSP) monitor were compared to model results, with
modeled concentrations being in close agreement to monitored
concentrations. Refer to Table 2 for comparisons of the annual
monitored concentrations. AQS Monitor (04-007-8000) is located at the
Miami golf course (SR 188 and US 60) and is the only operating monitor
for the area. This monitor is located approximately 1,400 meters
southwest of the MIR location from the HEM-4 model run. Based on the
model analysis presented above, the monitor is located such that the
maximum off-site modeled lead concentration may be up to a factor of
four times higher than measured at the golf course site. Thus, based on
the modeling analysis presented in this risk assessment, the predicted
off-site ambient concentrations near the Freeport facility may approach
or exceed the maximum lead 3-month average NAAQS of 0.15 ug/m\3\.

Table 2--Monitor to Model Comparison for Primary Copper Smelting Source Category for Arsenic and Lead
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annual average conc. (ug/m\3\) Cancer risk (xx-in-1 million) HQ
Site -----------------------------------------------------------------------------------------------
Model Monitor Model Monitor Model Monitor
--------------------------------------------------------------------------------------------------------------------------------------------------------
Asarco Monitor 23 (As) \1\ \2\.......................... 0.011 0.022 50 90 0.8 1.4
Asarco Monitor 23 (Pb) \1\ \2\.......................... 0.025 0.098 NA NA NA NA
Freeport NAAQS Monitor (Pb) \2\......................... 0.026 0.022 NA NA NA NA
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ The Asarco Monitor 23 is located off-site and within 100 meters of the modeled MIR residential location.
\2\ The monitor and modeling data were based upon emission estimates and monitoring data collected for the 2019 calendar year.

With regard to emissions estimates used for the modeling analysis,
as discussed in section II.C above, the Agency has higher confidence
and less uncertainty with the Freeport emissions as compared to Asarco
because the Agency has multiple test results for both point and non-
point (i.e.,

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