[Federal Register Volume 86, Number 10 (Friday, January 15, 2021)]
[Proposed Rules]
[Pages 3906-3927]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-00374]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0532; FRL-10018-49-OAR]
RIN 2060-AU64


National Emission Standards for Hazardous Air Pollutants: Cyanide 
Chemicals Manufacturing Residual Risk and Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is proposing 
the results of the residual risk and technology review (RTR) for the 
National Emission Standards for Hazardous Air Pollutants (NESHAP) for 
the Cyanide Chemicals Manufacturing source category as required under 
the Clean Air Act (CAA). We are proposing to find that risk from 
emissions of air toxics from this source category is acceptable, and 
that the current standards provide an ample margin of safety to protect 
public health. We are also proposing to find that there are no 
developments in practices, processes, and control technologies, and, as 
such, we are not proposing any development-based changes to the current 
standards pursuant to the technology review. The EPA is, however, 
proposing new emissions standards to address emissions from process 
wastewater at existing sources. We are proposing to amend provisions 
addressing startup, shutdown, and malfunction (SSM), to add electronic 
reporting, and to update the reporting and recordkeeping requirements. 
We do not expect these proposed amendments to result in changes in 
emissions from the source category but anticipate improved monitoring, 
compliance, and implementation of the existing standards.

DATES: Comments must be received on or before March 1, 2021. 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 16, 2021.
    Public hearing: If anyone contacts us requesting a public hearing 
on or before January 21, 2021, we 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-2020-0532, by any of the following methods:
    <bullet> Federal eRulemaking Portal: https://www.regulations.gov/ 
(our preferred method). Follow the online instructions for submitting 
comments.
    <bullet> Email: <a href="/cdn-cgi/l/email-protection#6d0c400c0309401f4009020e0608192d081d0c430a021b"><span class="__cf_email__" data-cfemail="02632f636c662f702f666d61696776426772632c656d74">[email protected]</span></a>. Include Docket ID No. EPA-
HQ-OAR-2020-0532 in the subject line of the message.
    <bullet> Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2020-0532.
    <bullet> Mail: U.S. Environmental Protection Agency, EPA Docket 
Center, Docket ID No. EPA-HQ-OAR-2020-0532, 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 https://www.regulations.gov/, 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. We encourage the public to submit comments via https://www.regulations.gov/ 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 
https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Nathan Topham, 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) 541-0483; fax number: (919) 541-4991; 
and email address: <a href="/cdn-cgi/l/email-protection#6b1f041b030a0645050a1f030a052b0e1b0a450c041d"><span class="__cf_email__" data-cfemail="becad1ced6dfd390d0dfcad6dfd0fedbcedf90d9d1c8">[email protected]</span></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) 541-0840; and email address: <a href="/cdn-cgi/l/email-protection#541c3d26202e7a1e35393127143124357a333b22"><span class="__cf_email__" data-cfemail="fdb5948f8987d3b79c90988ebd988d9cd39a928b">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION: 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#f4a7a4a4b0848196989d979c9195869d9a93b4918495da939b82"><span class="__cf_email__" data-cfemail="1d4e4d4d596d687f71747e75787c6f74737a5d786d7c337a726b">[email protected]</span></a>. If 
requested, the virtual hearing will be held on February 1, 2021. 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 https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen.
    The EPA will begin pre-registering speakers for the hearing upon 
publication of this document in the Federal Register, if a hearing is 
requested. To register to speak at the virtual hearing, please use the 
online registration form available at https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen or contact the public hearing team at (888) 372-8699 or 
by email at <a href="/cdn-cgi/l/email-protection#89dad9d9cdf9fcebe5e0eae1ece8fbe0e7eec9ecf9e8a7eee6ff"><span class="__cf_email__" data-cfemail="2f7c7f7f6b5f5a4d43464c474a4e5d4641486f4a5f4e01484059">[email protected]</span></a>. The last

[[Page 3907]]

day to pre-register to speak at the hearing will be January 27, 2021. 
Prior to the hearing, the EPA will post a general agenda that will list 
pre-registered speakers in approximate order at: https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen.
    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#86f2e9f6eee7eba8e8e7f2eee7e8c6e3f6e7a8e1e9f0"><span class="__cf_email__" data-cfemail="95e1fae5fdf4f8bbfbf4e1fdf4fbd5f0e5f4bbf2fae3">[email protected]</span></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 https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen. 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#9ccfccccd8ece9fef0f5fff4f9fdeef5f2fbdcf9ecfdb2fbf3ea"><span class="__cf_email__" data-cfemail="95c6c5c5d1e5e0f7f9fcf6fdf0f4e7fcfbf2d5f0e5f4bbf2fae3">[email protected]</span></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 
22, 2021. 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-2020-0532. All documents in the docket are 
listed in https://www.regulations.gov. Although listed, some 
information is not publicly available, e.g., Confidential Business 
Information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, is 
not placed on the internet and will be publicly available only in hard 
copy. With the exception of such material, publicly available docket 
materials are available electronically in Regulations.gov.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2020-0532. The EPA's policy is that all comments received will be 
included in the public docket without change and may be made available 
online at https://www.regulations.gov/, including any personal 
information provided, unless the comment includes information claimed 
to be CBI or other information whose disclosure is restricted by 
statute. Do not submit 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 https://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov/ website allows you to submit your 
comment anonymously, which means the EPA will not know your identity or 
contact information unless you provide it in the body of your comment. 
If you send an email comment directly to the EPA without going through 
https://www.regulations.gov/, your email address will be automatically 
captured and included as part of the comment that is placed in the 
public docket and made available on the internet. If you submit an 
electronic comment, the EPA recommends that you include your name and 
other contact information in the body of your comment and with any 
digital storage media you submit. If the EPA cannot read your comment 
due to technical difficulties and cannot contact you for clarification, 
the EPA may not be able to consider your comment. Electronic files 
should not include special characters or any form of encryption and be 
free of any defects or viruses. For additional information about the 
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    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. We 
encourage the public to submit comments via https://www.regulations.gov/ 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 https://www.epa.gov/dockets.
    The EPA continues to carefully and continuously monitor information 
from the CDC, local area health departments, and our Federal partners 
so that we can respond rapidly as conditions change regarding COVID-19.
    Submitting CBI. Do not submit information containing CBI to the EPA 
through https://www.regulations.gov/ or email. Clearly mark the part or 
all of the information that you claim to be CBI. For CBI information on 
any digital storage media that you mail to the EPA, mark the outside of 
the digital storage media as CBI and then identify electronically 
within the digital storage media the specific information that is 
claimed as CBI. In addition to one complete version of the comments 
that includes information claimed as CBI, you must submit a copy of the 
comments that does not contain the information claimed as CBI directly 
to the public docket through the procedures outlined in Instructions 
above. If you submit any digital storage media that does not contain 
CBI, mark the outside of the digital storage media clearly that it does 
not contain CBI. Information not marked as CBI will be included in the 
public docket and the EPA's electronic public docket without prior 
notice. Information marked as CBI will not be disclosed except in 
accordance with procedures set forth in 40 Code of Federal Regulations 
(CFR) part 2. Send or deliver information identified as CBI only to the 
following address: OAQPS Document Control Officer (C404-02), OAQPS, 
U.S. Environmental Protection Agency, Research Triangle Park, North 
Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2020-0532. Note that 
written comments containing CBI and submitted by mail may be delayed 
and no hand deliveries will be accepted.
    Preamble acronyms and abbreviations. We use multiple acronyms and 
terms in this preamble. While this list may not be exhaustive, to ease 
the reading of this preamble and for

[[Page 3908]]

reference purposes, the EPA defines the following terms and acronyms 
here:

AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-3 model
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CFR Code of Federal Regulations
EPA Environmental Protection Agency
ERPG emergency response planning guideline
ERT Electronic Reporting Tool
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-3 Human Exposure Model, Version 1.5.5
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
IRIS Integrated Risk Information System
km kilometer
MACT maximum achievable control technology
mg/kg-day milligrams per kilogram per day
mg/m3 milligrams per cubic meter
MIR maximum individual risk
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NESHAP national emission standards for hazardous air pollutants
NRC National Research Council
OAQPS Office of Air Quality Planning and Standards
OMB Office of Management and Budget
PAH polycyclic aromatic hydrocarbons
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
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SBA Small Business Administration
SSM startup, shutdown, and malfunction
SV screening value
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/m3 microgram per cubic meter
URE unit risk estimate
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. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulations and Controlling 
Regulatory Costs
    C. Paperwork Reduction Act (PRA)
    D. Regulatory Flexibility Act (RFA)
    E. Unfunded Mandates Reform Act (UMRA)
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    I. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    J. National Technology Transfer and Advancement Act (NTTAA)
    K. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

A. Does this action apply to me?

    The source category that is the subject of this proposal is cyanide 
chemicals manufacturing major sources regulated under 40 CFR 63, 
subpart YY. The North American Industry Classification System (NAICS) 
codes for the cyanide chemicals manufacturing industry are 325188 and 
325199. 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. Federal, state, local, and tribal government entities 
would not be affected by this proposed action. As defined in the 
Initial List of Categories of Sources Under Section 112(c)(1) of 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 Cyanide Chemicals 
Manufacturing source category is any facility engaged in the production 
of hydrogen cyanide or sodium cyanide. Hydrogen cyanide production 
includes, but is not limited to, production of hydrogen cyanide using 
any of the following methods: Reaction of methane and ammonia over a 
platinum catalyst, reaction of methane and ammonia over a platinum-
rhodium catalyst, co-production with acrylonitrile (via Sohio process), 
or pyrolysis of formaldehyde. Sodium cyanide production includes, but 
is not limited to, production of sodium cyanide via the neutralization 
process, or so-called wet process. In this process, hydrogen cyanide 
reacts with sodium hydroxide solution usually in a reactor that 
involves evaporation of water and crystallization of the product, 
commonly called white cyanide.

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

    In addition to being available in the docket, an electronic copy of 
this action is available on the internet. Following signature by the 
EPA Administrator, the EPA will post a copy of this proposed action at 
https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen. Following publication 
in the Federal Register, the EPA will post the Federal Register version 
of the proposal and key technical documents at this same website. 
Information on the overall RTR program is available at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.
    The proposed changes to the CFR that would be necessary to 
incorporate the changes proposed in this action are set out in an 
attachment to the memorandum titled Proposed Regulation Edits for 40 
CFR part 63, subpart YY, available in the docket for this action 
(Docket ID No. EPA-HQ-

[[Page 3909]]

OAR-2020-0532). The document includes the specific proposed amendatory 
language for revising the CFR and, for the convenience of interested 
parties, a redline version of the regulation. Following signature by 
the EPA Administrator, the EPA will also post a copy of this memorandum 
and the attachments to https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen.

II. Background

A. What is the statutory authority for this action?

    The statutory authority for this action is provided by sections 112 
and 301 of the CAA, as amended (42 U.S.C. 7401 et seq.). Section 112 of 
the CAA establishes a two-stage regulatory process to develop standards 
for emissions of hazardous air pollutants (HAP) from stationary 
sources. Generally, the first stage involves establishing technology-
based standards and the second stage involves evaluating those 
standards that are based on maximum achievable control technology 
(MACT) to determine whether additional standards are needed to address 
any remaining risk associated with HAP emissions. This second stage is 
commonly referred to as the ``residual risk review.'' In addition to 
the residual risk review, the CAA also requires the EPA to review 
standards set under CAA section 112 every 8 years 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 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 determinations (EPA-453/R-99-001, p. ES-11). The EPA 
subsequently adopted this approach in its residual risk determinations 
and the United States Court of Appeals for the District of Columbia 
Circuit (the court) upheld the EPA's interpretation that CAA section 
112(f)(2) incorporates the approach established in the Benzene NESHAP. 
See NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008).
    The approach incorporated into the CAA and used by the EPA to 
evaluate residual risk and to develop standards under CAA section 
112(f)(2) is a two-step approach. In the first step, the EPA determines 
whether risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) 
\1\ of approximately 1 in 10 thousand.'' (54 FR 38045). 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, we consider whether a more stringent standard is 
necessary to prevent, taking into consideration costs, energy, safety, 
and other relevant factors, an adverse environmental effect.
---------------------------------------------------------------------------

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

    CAA section 112(d)(6) separately requires the EPA to review 
standards promulgated under CAA section 112 and revise them ``as 
necessary (taking into account developments in practices, processes, 
and control technologies)'' no less often than every 8 years. In 
conducting this review, which we call the ``technology review,'' the 
EPA is not required to recalculate the MACT floor. Natural Resources 
Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008). 
Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 
2013). The EPA may consider cost in deciding whether to revise the

[[Page 3910]]

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 MACT standards for the Cyanide Chemicals Manufacturing source 
category are contained in the Generic Maximum Achievable Control 
Technology (GMACT) NESHAP which also includes MACT standards for 
several other source categories. The cyanide chemicals manufacturing 
standards were promulgated on July 12, 2002, (67 FR 46258) and codified 
at 40 CFR part 63, subpart YY. As promulgated in 2002, the cyanide 
chemicals manufacturing standards regulate HAP emissions from cyanide 
chemicals manufacturing units located at major sources. The HAP emitted 
from the source category include cyanide compounds (hydrogen cyanide 
and sodium cyanide), acetonitrile, and acrylonitrile.
    The NESHAP defines the affected source as each cyanide chemicals 
manufacturing process unit (CCMPU). The rule states that the CCMPU is 
the equipment assembled and connected by hard-piping or duct work to 
process raw materials to manufacture, store, and transport a cyanide 
chemicals product. A CCMPU shall be limited to any one of the 
following: An Andrussow process unit, a Blausaure Methane Anlage 
process unit, a sodium cyanide process unit, or a Sohio hydrogen 
cyanide process unit. For the purpose of this subpart, a CCMPU includes 
reactors and associated unit operations, associated recovery devices, 
and any feed, intermediate and product storage vessels, product 
transfer racks, and connected ducts and piping. A CCMPU also includes 
pumps, compressors, agitators, pressure relief devices, sampling 
connection systems, open-ended valves or lines, valves, connectors, 
instrumentation systems, and control devices or systems.
    The NESHAP established emissions standards for process vents, 
storage vessels, transfer racks, and equipment leaks. Cyanide process 
vents are subject to a 98 weight-percent reduction of total HAP \2\ 
performance standard or 20 parts per million by volume (ppmv) total HAP 
outlet exit concentration limit. For storage vessels in the Cyanide 
Chemicals Manufacturing source category, sources may either choose to 
comply with a 98 weight-percent reduction of hydrogen cyanide 
performance standard, a 20 ppmv hydrogen cyanide exit outlet 
concentration limit, or equipment standards (e.g., use a flare). 
Transfer racks are subject to equipment standards or the same 
performance standard or concentration limit \3\ as cyanide process 
vents. Equipment leaks are subject to work practice standards required 
by either 40 CFR part 63, subpart TT or subpart UU.
---------------------------------------------------------------------------

    \2\ ``Dry end'' process vents at sodium cyanide units must meet 
a 98 percent reduction performance standard for emissions of sodium 
cyanide since this is the form of cyanide compounds emitted from 
these emission points. The HAP emitted from other process vents that 
make up the ``total HAP'' emitted from these sources are hydrogen 
cyanide, acetonitrile, and acrylonitrile.
    \3\ Transfer racks emissions limits are expressed in terms of 
hydrogen cyanide as this is the only HAP emitted from these sources.
---------------------------------------------------------------------------

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

    The EPA used a variety of resources to obtain data about facilities 
and their emissions for use in our risk assessment. We used the EPA's 
Enforcement and Compliance History Online (ECHO) database to develop a 
list of potentially subject facilities. Using this list, we searched 
state environmental agency websites and correspondence with industry to 
obtain copies of title V permits to confirm whether facilities have 
cyanide chemicals manufacturing subject to the NESHAP. Once the 
facility list was finalized, the EPA used the 2017 National Emissions 
Inventory (NEI) to get emissions data for each facility. We compared 
the NEI data to title V permits to provide additional information 
regarding the applicability of the Cyanide Chemicals Manufacturing 
NESHAP. Further discussion of the methodology used to develop the 
emissions dataset for the risk assessment can be found in the 
memorandum titled Technical Support Document for the Cyanide Chemicals 
Manufacturing NESHAP Residual Risk and Technology Review Proposal, 
which is available in the docket for this action.

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

    We searched for information from the Reasonably Available Control 
Technology, Best Available Control Technology, and Lowest Achievable 
Emission Rate Clearinghouse (RBLC) database, reviewed title V permits 
for each cyanide chemicals manufacturing facility, and reviewed 
regulatory actions related to emissions controls at similar sources 
that could be applicable to cyanide chemicals manufacturing. We 
reviewed the RBLC to identify potential additional control 
technologies. No additional control technologies applicable to cyanide 
chemicals manufacturing were found using the RBLC. Additional 
information related to the promulgation and subsequent amendments of 
the NESHAP is available in docket ID: No. EPA-HQ-OAR-2004-0041.

III. Analytical Procedures and Decision-Making

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

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

    As discussed in section II.A of this preamble and in the Benzene 
NESHAP, in evaluating and developing standards under CAA section 
112(f)(2), we apply a two-step approach to determine whether or not 
risks are acceptable and to determine if the standards provide an ample 
margin of safety to protect public health. As explained in the Benzene 
NESHAP, ``the first step judgment on acceptability cannot be reduced to 
any single factor'' and, thus, ``[t]he Administrator believes that the 
acceptability of risk under section 112 is best judged on the basis of 
a broad set of health risk measures and information.'' (54 FR 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

[[Page 3911]]

effects.\4\ 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:
---------------------------------------------------------------------------

    \4\ 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 non-cancer health 
effects, and the uncertainties of the risk estimates. In this way, 
the effect on the most exposed individuals can be reviewed as well 
as the impact on the general public. These factors can then be 
weighed in each individual case. This approach complies with the 
Vinyl Chloride mandate that the Administrator ascertain an 
acceptable level of risk to the public by employing his expertise to 
assess available data. It also complies with the Congressional 
intent behind the CAA, which did not exclude the use of any 
particular measure of public health risk from the EPA's 
consideration with respect to CAA section 112 regulations, and 
thereby implicitly permits consideration of any and all measures of 
health risk which the Administrator, in his judgment, believes are 
---------------------------------------------------------------------------
appropriate to determining what will ``protect the public health.

(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. We also consider the uncertainties associated with the various 
risk analyses, as discussed earlier in this preamble, in our 
determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information 
to date in making residual risk determinations. At this time, we do not 
attempt to quantify the HAP risk that may be associated with emissions 
from other facilities that do not include the source 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. We recognize 
that such consideration may be particularly important when assessing 
noncancer risk, where pollutant-specific exposure health reference 
levels (e.g., reference concentrations (RfCs)) are based on the 
assumption that thresholds exist for adverse health effects. For 
example, the EPA recognizes that, although exposures attributable to 
emissions from a source category or facility alone may not indicate the 
potential for increased risk of adverse noncancer health effects in a 
population, the exposures resulting from emissions from the facility in 
combination with emissions from all of the other sources (e.g., other 
facilities) to which an individual is exposed may be sufficient to 
result in an increased risk of adverse noncancer health effects. In May 
2010, the Science Advisory Board (SAB) advised the EPA ``that RTR 
assessments will be most useful to decision makers and communities if 
results are presented in the broader context of aggregate and 
cumulative risks, including background concentrations and contributions 
from other sources in the area.'' \5\
---------------------------------------------------------------------------

    \5\ 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 we are interested in placing source category and facility-
wide HAP risk in the context of total HAP risk from all sources 
combined in the vicinity of each source, we are concerned about the 
uncertainties of doing so. Estimates of total HAP risk from emission 
sources other than those that we have studied in depth during this RTR 
review would have significantly greater associated uncertainties than 
the source category or facility-wide estimates. Such aggregate or 
cumulative assessments would compound those uncertainties, making the 
assessments too unreliable.

B. How do we perform the technology review?

    Our technology review 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. We also consider the emission reductions 
associated with applying each development. This analysis informs our 
decision of whether it is ``necessary'' to revise the emissions 
standards. In addition, we consider the appropriateness of applying 
controls to new sources versus retrofitting existing sources. For this 
exercise, we consider any of the following to be a ``development'':
    <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

[[Page 3912]]

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 we originally developed 
(or last updated) the NESHAP, we review a variety of data sources in 
our investigation of potential practices, processes, or controls. We 
also review the NESHAP and the available data to determine if there are 
any unregulated emissions of HAP within the source category and 
evaluate this 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, we provide a complete description of the types of 
analyses that we generally perform during the risk assessment process. 
In some cases, we do not perform a specific analysis because it is not 
relevant. For example, in the absence of emissions of HAP known to be 
persistent and bioaccumulative in the environment (PB-HAP), we would 
not perform a multipathway exposure assessment. Where we do not perform 
an analysis, we state that we do not and provide the reason. While we 
present all of our risk assessment methods, we only present risk 
assessment results for the analyses actually conducted (see 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 seven sections 
that follow this paragraph describe how we 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 Cyanide 
Chemicals Manufacturing Source Category in Support of the 2020 Risk and 
Technology Review Proposed Rule. The methods used to assess risk (as 
described in the seven primary steps below) are consistent with those 
described by the EPA in the document reviewed by a panel of the EPA's 
SAB in 2009; \6\ and described in the SAB review report issued in 2010. 
They are also consistent with the key recommendations contained in that 
report.
---------------------------------------------------------------------------

    \6\ U.S. EPA. Risk and Technology Review (RTR) Risk Assessment 
Methodologies: For Review by the EPA's Science Advisory Board with 
Case Studies--MACT I Petroleum Refining Sources and Portland Cement 
Manufacturing, June 2009. EPA-452/R-09-006. https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    The list of facilities subject to the NESHAP was created through 
searching the EPA's ECHO database, the 2017 NEI, and state databases of 
title V permits. The list of facilities is available in the memorandum 
titled Technical Support Document for the Cyanide Chemicals 
Manufacturing NESHAP Residual Risk and Technology Review Proposal. Once 
the facility list was finalized, available emissions data were obtained 
from the NEI. Title V permits were used to determine which emission 
points at each facility are subject to the Cyanide Chemicals 
Manufacturing NESHAP.
    We compared the NEI data to title V permits to confirm that the NEI 
included all emission points listed as subject to the NESHAP according 
to the permit. We evaluated latitudes and longitudes listed in the NEI 
to ensure their accuracy using satellite imagery. All of the latitudes 
and longitudes used in our dispersion modeling are in the modeling file 
used for the proposed rule, which is available in Docket ID No. EPA-HQ-
OAR-2020-0532. Corrections were made to emission point characteristics 
for one non-category emission point that appeared to have erroneous 
stack velocity entered into the NEI. This emission point's stack 
velocity was corrected to a default maximum value. All corrections made 
to emission point parameters are documented in the modeling file, 
available in Docket ID No. EPA-HQ-OAR-2020-0532.
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include 
estimates of the mass of HAP emitted during a specified annual time 
period. These ``actual'' emission levels are often lower than the 
emission levels allowed under the requirements of the current MACT 
standards. The emissions allowed under the MACT standards are referred 
to as the ``MACT-allowable'' emissions. We discussed the consideration 
of both MACT-allowable and actual emissions in the final Coke Oven 
Batteries RTR (70 FR 19992, 19998 and 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, we noted that assessing the risk at 
the MACT-allowable level is inherently reasonable since that risk 
reflects the maximum level facilities could emit and still comply with 
national emission standards. We also explained that it is reasonable to 
consider actual emissions, where such data are available, in both steps 
of the risk analysis, in accordance with the Benzene NESHAP approach. 
(54 FR 38044).
    We have determined that the actual emissions data are reasonable 
estimates of the MACT-allowable emissions levels for the Cyanide 
Chemicals Manufacturing source category. The ability to estimate MACT-
allowable emissions from the actual emissions dataset is largely 
dependent on the format of the standard for a given emissions source as 
well as the types of controls employed for the source. With respect to 
the various types of controls used within the Cyanide Chemicals 
Manufacturing source category, the most prevalent is the use of a flare 
as a combustion control device. A flare can be used to control 
emissions for a single emissions source, or, as is generally the case, 
to control emissions from multiple emission sources/emission source 
types. Flares are designed to handle a wide range of flowrates and 
compositions of combustible waste gases. Within the Cyanide Chemicals 
Manufacturing source category, flares generally control emissions from 
multiple emission source types. Consideration of this, along with not 
having a specific limit on how much gas can be combusted in a flare 
(given that in many cases multiple emissions sources are being 
controlled by this control device), means that it is extremely 
difficult to determine an allowable emission rate for flares. We have 
determined that flares in the Cyanide Chemicals Manufacturing

[[Page 3913]]

source category are currently complying with design and operational 
requirements that are generally expected to achieve 98 percent 
destruction efficiencies or control, which is the level of control 
required by the NESHAP. HAP emissions inventories for flares in the 
Cyanide Chemicals Manufacturing source category are developed using 
engineering knowledge and, in many instances, presume this 98 percent 
level of control. The Agency is unaware of any data that suggest that 
flares used as controls in the Cyanide Chemicals Manufacturing source 
category are consistently overcontrolling HAP emissions beyond 98 
percent control. Thus, weighing all of these factors for flares, we 
determined that the actual emission levels are a reasonable estimation 
of the MACT-allowable emissions levels where the performance standards 
allow the use of a flare as an air pollution control device (e.g., 
storage vessels, process vents, and transfer racks).
    For equipment leaks, which are currently subject to work practice 
standards, there would be no difference between actual and MACT-
allowable emissions for facilities in the Cyanide Chemicals 
Manufacturing source category, provided the facilities are complying 
with the MACT standards as well as not conducting additional work 
practices that would reduce emissions beyond those required by the 
rule. We are aware of only one rule in the state of Texas, the Texas 
Commission of Environmental Quality (TCEQ) Highly Reactive Volatile 
Organic Compounds (HRVOC) Rule (i.e., 30 TAC Chapter 115, Subchapter H, 
Division 3), that may contain more stringent leak definitions and/or 
monitoring frequencies for certain pieces of equipment for the three 
facilities located in Texas that might be subject to this rule. 
However, based on our review of the Texas rule, we note the following: 
(1) Specific facilities located in the Houston-Galveston-Brazoria area 
still conduct a leak detection and repair (LDAR) program using EPA 
Method 21; (2) the vast majority of equipment, including almost all 
pieces of equipment in gas and vapor service that would tend to 
contribute considerably to the overall equipment leak air emissions, 
are complying with the same leak definition as in the MACT standards; 
and (3) the TCEQ HRVOC Rule generally requires quarterly monitoring 
while the MACT standards have varying monitoring frequencies depending 
on the percentage of leaking equipment that could lead to more 
stringent, the same, or less stringent frequencies that would require 
an EPA Method 21 measurement and repair of a leaking component (if 
measured). Therefore, considering these factors for equipment leaks, we 
determined that the actual emission levels for equipment leaks are a 
reasonable estimation of the MACT-allowable emissions levels.
3. How do we conduct dispersion modeling, determine inhalation 
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations 
and health risk from the source category addressed in this proposal 
were estimated using the Human Exposure Model (HEM-3).\7\ The HEM-3 
performs three primary risk assessment activities: (1) Conducting 
dispersion modeling to estimate the concentrations of HAP in ambient 
air, (2) estimating long-term and short-term inhalation exposures to 
individuals residing within 50 kilometers (km) of the modeled sources, 
and (3) estimating individual and population-level inhalation risk 
using the exposure estimates and quantitative dose-response 
information.
---------------------------------------------------------------------------

    \7\ For more information about HEM-3, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
---------------------------------------------------------------------------

a. Dispersion Modeling
    The air dispersion model AERMOD, used by the HEM-3 model, is one of 
the EPA's preferred models for assessing air pollutant concentrations 
from industrial facilities.\8\ To perform the dispersion modeling and 
to develop the preliminary risk estimates, HEM-3 draws on three data 
libraries. The first is a library of meteorological data, which is used 
for dispersion calculations. This library includes 1 year (2016) of 
hourly surface and upper air observations from 826 meteorological 
stations, selected to provide coverage of the United States and Puerto 
Rico. A second library of United States Census Bureau census block \9\ 
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.
---------------------------------------------------------------------------

    \8\ 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).
    \9\ A census block is the smallest geographic area for which 
census statistics are tabulated.
---------------------------------------------------------------------------

b. Risk From Chronic Exposure to HAP
    In developing the risk assessment for chronic exposures, we use the 
estimated annual average ambient air concentrations of each HAP emitted 
by each source in the source category. The HAP air concentrations at 
each nearby census block centroid located within 50 km of the facility 
are a surrogate for the chronic inhalation exposure concentration for 
all the people who reside in that census block. A distance of 50 km is 
consistent with both the analysis supporting the 1989 Benzene NESHAP 
(54 FR 38044) and the limitations of Gaussian dispersion models, 
including AERMOD.
    For each facility, we calculate the MIR as the cancer risk 
associated with a continuous lifetime (24 hours per day, 7 days per 
week, 52 weeks per year, 70 years) exposure to the maximum 
concentration at the centroid of each inhabited census block. We 
calculate individual cancer risk by multiplying the estimated lifetime 
exposure to the ambient concentration of each HAP (in micrograms per 
cubic meter ([mu]g/m\3\)) by its unit risk estimate (URE). The URE is 
an upper-bound estimate of an individual's incremental risk of 
contracting cancer over a lifetime of exposure to a concentration of 1 
microgram of the pollutant per cubic meter of air. For residual risk 
assessments, we generally use UREs from the EPA's Integrated Risk 
Information System (IRIS). For carcinogenic pollutants without IRIS 
values, we look to other reputable sources of cancer dose-response 
values, often using California EPA (CalEPA) UREs, where available. In 
cases where new, scientifically credible dose-response values have been 
developed in a manner consistent with EPA guidelines and have undergone 
a peer review process similar to that used by the EPA, we may use such 
dose-response values in place of, or in addition to, other values, if 
appropriate. The pollutant-specific dose-response values used to 
estimate health risk are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
    No data are available on the carcinogenic effects of cyanide 
compounds in humans via inhalation. Under the U.S. EPA (2005a) 
Guidelines for Carcinogen Risk Assessment, there is ``inadequate 
information to assess the carcinogenic potential'' of cyanide 
compounds.
    To estimate individual lifetime cancer risks associated with 
exposure to HAP emissions from each facility in the

[[Page 3914]]

source category, we sum 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.
---------------------------------------------------------------------------

    \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 
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing 
the risk of these individual compounds to obtain the cumulative 
cancer risk is an approach that was recommended by the EPA's SAB in 
their 2002 peer review of the EPA's National Air Toxics Assessment 
(NATA) titled NATA--Evaluating the National-scale Air Toxics 
Assessment 1996 Data--an SAB Advisory, available at https://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
---------------------------------------------------------------------------

    To assess the risk of noncancer health effects from chronic 
exposure to HAP, we calculate either an HQ or a target organ-specific 
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is 
emitted. Where more than one noncancer HAP is emitted, we sum the HQ 
for each of the HAP that affects a common target organ or target organ 
system to obtain a TOSHI. The HQ is the estimated exposure divided by 
the chronic noncancer dose-response value, which is a value selected 
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC, defined as ``an estimate (with 
uncertainty spanning perhaps an order of magnitude) of a continuous 
inhalation exposure to the human population (including sensitive 
subgroups) that is likely to be without an appreciable risk of 
deleterious effects during a lifetime'' (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary). In cases where an RfC 
from the EPA's IRIS is not available or where the EPA determines that 
using a value other than the RfC is appropriate, the chronic noncancer 
dose-response value can be a value from the following prioritized 
sources, which define their dose-response values similarly to the EPA: 
(1) The Agency for Toxic Substances and Disease Registry (ATSDR) 
Minimum Risk Level (https://www.atsdr.cdc.gov/mrls/index.asp); (2) the 
CalEPA Chronic Reference Exposure Level (REL) (https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0); or (3) as noted above, a scientifically 
credible dose-response value that has been developed in a manner 
consistent with the EPA guidelines and has undergone a peer review 
process similar to that used by the EPA. The pollutant-specific dose-
response values used to estimate health risks are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
    Cyanide is extremely toxic to humans. Acute (10-minute) inhalation 
exposure to 579 milligrams per cubic meter (mg/m\3\) of hydrogen 
cyanide will cause death in 50 percent of exposed humans. Nonlethal 
exposures to hydrogen cyanide gas will cause a variety of effects in 
humans, such as headache, dizziness, upper respiratory irritation, 
cough, altered sense of smell, nasal congestion, nosebleed, and 
difficulty breathing. Chronic (long-term) inhalation exposure of humans 
to cyanide results primarily in effects on the central nervous system. 
Other effects in humans include cardiovascular and respiratory effects, 
effects to the endocrine system (e.g., thyroid enlargement, altered 
iodine uptake), and irritation to the eyes and skin. However, short 
term exposure levels below the acute REL and chronic exposures below 
the RfC are not likely to cause adverse effects.
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,\11\ we 
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 the Cyanide Chemicals 
Manufacturing 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. This 
revised approach has been used in this proposed rule and in all other 
RTR rulemakings proposed on or after June 3, 2019.
---------------------------------------------------------------------------

    \11\ See, e.g., U.S. EPA. Screening Methodologies to Support 
Risk and Technology Reviews (RTR): A Case Study Analysis (Draft 
Report, May 2017. https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html).
---------------------------------------------------------------------------

    To assess the potential acute risk to the maximally exposed 
individual, we use the peak hourly emission rate for each emission 
point,\12\ 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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    \12\ In the absence of hourly emission data, we develop 
estimates of maximum hourly emission rates by multiplying the 
average actual annual emissions rates by a factor (either a 
category-specific factor or a default factor of 10) to account for 
variability. This is documented in Residual Risk Assessment for the 
Cyanide Chemicals Manufacturing 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.
---------------------------------------------------------------------------

    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.
    An acute REL is defined as ``the concentration level at or below 
which no adverse health effects are anticipated

[[Page 3915]]

for a specified exposure duration.'' \13\ 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.\14\ 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.'' The document also notes that ``Airborne concentrations 
below AEGL-1 represent exposure levels that can produce mild and 
progressively increasing but transient and nondisabling odor, taste, 
and sensory irritation or certain asymptomatic, nonsensory effects.'' 
Id. AEGL-2 are defined as ``the airborne concentration (expressed as 
parts per million or milligrams per cubic meter) of a substance above 
which it is predicted that the general population, including 
susceptible individuals, could experience irreversible or other 
serious, long-lasting adverse health effects or an impaired ability to 
escape.'' Id.
---------------------------------------------------------------------------

    \13\ CalEPA issues acute RELs as part of its Air Toxics Hot 
Spots Program, and the 1-hour and 8-hour values are documented in 
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The 
Determination of Acute Reference Exposure Levels for Airborne 
Toxicants, which is available at https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \14\ National Academy of Sciences, 2001. Standing Operating 
Procedures for Developing Acute Exposure Levels for Hazardous 
Chemicals, page 2. Available at https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf. Note that the 
National Advisory Committee for Acute Exposure Guideline Levels for 
Hazardous Substances ended in October 2011, but the AEGL program 
continues to operate at the EPA and works with the National 
Academies to publish final AEGLs (https://www.epa.gov/aegl).
---------------------------------------------------------------------------

    ERPGs are ``developed for emergency planning and are intended as 
health-based guideline concentrations for single exposures to 
chemicals.'' \15\ 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.
---------------------------------------------------------------------------

    \15\ ERPGS Procedures and Responsibilities. March 2014. American 
Industrial Hygiene Association. Available at: https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf.
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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 used acute factors between 2 and 10, 
depending on the type of source, to estimate peak hourly emissions from 
annual emissions estimates for input into the risk assessment modeling 
analysis. Specifically, we used a factor of 2 for process vents and 
equipment leaks, a factor of 4 for storage vessels, and a factor of 10 
for transfer racks. A further discussion of why these factors were 
chosen can be found in the memorandum, Technical Support Document for 
the Cyanide Chemicals Manufacturing NESHAP Residual Risk and Technology 
Review Proposal, 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, no data were conducted.
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 
https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the Cyanide Chemicals Manufacturing source category, we 
identified potential PB-HAP emissions of arsenic, cadmium, lead, 
mercury, and polycyclic organic matter (POM) based on entries in the 
NEI. We note that for the Cyanide Chemicals Manufacturing source 
category, we modeled these pollutants to provide a conservative 
assessment of risks because these pollutants are included in the NEI. 
However, we do not believe these HAP are emitted from the cyanide 
chemicals manufacturing process. Very small amounts of these HAP are 
included in the NEI as byproducts of fuel combustion and are unrelated 
to cyanide chemicals manufacturing.
    After identifying potential PB-HAP emissions, the next step of the 
evaluation is a tiered screening assessment. 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 
ingestion exposure. 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 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. (See Volume

[[Page 3916]]

1, Appendix D at https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf.) 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 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 \16\) and 
locally grown or raised foods (90th percentile consumption of locally 
grown or raised foods for the farmer and gardener scenarios \17\). 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.
---------------------------------------------------------------------------

    \16\ Burger, J. 2002. Daily consumption of wild fish and game: 
Exposures of high end recreationists. International Journal of 
Environmental Health Research, 12:343-354.
    \17\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final). 
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
---------------------------------------------------------------------------

    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, we compare maximum estimated chronic inhalation exposure 
concentrations to the level of the current National Ambient Air Quality 
Standard (NAAQS) for lead.\18\ Values below the level of the primary 
(health-based) lead NAAQS are considered to have a low potential for 
multipathway risk.
---------------------------------------------------------------------------

    \18\ In doing so, the EPA notes that the legal standard for a 
primary NAAQS--that a standard is requisite to protect public health 
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other 
things, that the standard provide an ``ample margin of safety to 
protect public health''). However, the primary lead NAAQS is a 
reasonable measure of determining risk acceptability (i.e., the 
first step of the Benzene NESHAP analysis) since it is designed to 
protect the most susceptible group in the human population--
children, including children living near major lead emitting 
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, 
applying the level of the primary lead NAAQS at the risk 
acceptability step is conservative, since that primary lead NAAQS 
reflects an adequate margin of safety.
---------------------------------------------------------------------------

    For further information on the multipathway assessment approach, 
see the Residual Risk Assessment for the Cyanide Chemicals 
Manufacturing Source Category in Support of the Risk and Technology 
Review 2020 Proposed Rule, which is available in the docket for this 
action.
5. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological 
Benchmarks
    The EPA conducts a screening assessment to examine the potential 
for an adverse environmental effect as required under section 
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse 
environmental effect'' as ``any significant and widespread adverse 
effect, which may reasonably be anticipated, to wildlife, aquatic life, 
or other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as 
``environmental HAP,'' in its screening assessment: six PB-HAP and two 
acid gases. The PB-HAP included in the screening assessment are arsenic 
compounds, cadmium compounds, dioxins/furans, POM, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. The acid 
gases included in the screening assessment are hydrochloric acid (HCl) 
and hydrogen fluoride (HF).
    HAP that persist and bioaccumulate are of particular environmental 
concern because they accumulate in the soil, sediment, and water. The 
acid gases, HCl and HF, are included due to their well-documented 
potential to cause direct damage to terrestrial plants. In the 
environmental risk screening assessment, we evaluate the following four 
exposure media: terrestrial soils, surface water bodies (includes 
water-column and benthic sediments), fish consumed by wildlife, and 
air. Within these four exposure media, we evaluate nine ecological 
assessment endpoints, which are defined by the ecological

[[Page 3917]]

entity and its attributes. For PB-HAP (other than lead), both 
community-level and population-level endpoints are included. For acid 
gases, the ecological assessment evaluated is terrestrial plant 
communities.
    An ecological benchmark represents a concentration of HAP that has 
been linked to a particular environmental effect level. For each 
environmental HAP, we identified the available ecological benchmarks 
for each assessment endpoint. We identified, where possible, ecological 
benchmarks at the following effect levels: probable effect levels, 
lowest-observed-adverse-effect level, and no-observed-adverse-effect 
level. In cases where multiple effect levels were available for a 
particular PB-HAP and assessment endpoint, we use all of the available 
effect levels to help us to determine whether ecological risks exist 
and, if so, whether the risks could be considered significant and 
widespread.
    For further information on how the environmental risk screening 
assessment was conducted, including a discussion of the risk metrics 
used, how the environmental HAP were identified, and how the ecological 
benchmarks were selected, see Appendix 9 of the Residual Risk 
Assessment for the Cyanide Chemicals Manufacturing Source Category in 
Support of the Risk and Technology Review 2020 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 Cyanide Chemicals 
Manufacturing source category emitted any of the environmental HAP. For 
the Cyanide Chemicals Manufacturing source category, we identified 
potential emissions of arsenic, cadmium, lead, mercury, POM, and one 
acid gas, HCl, based on entries in the NEI. Because one or more of the 
environmental HAP evaluated may be emitted by at least one facility in 
the source category, we proceeded to the second step of the evaluation. 
As noted above, we modeled these emissions to err on the side of an 
overly conservative analysis because they are included in the NEI; 
however, we do not believe these HAP are emitted from the Cyanide 
Chemicals Manufacturing source category. The NEI entries for these HAP 
from these sources are likely the result of emissions factors that are 
used for fuel combustion and are unrelated to cyanide chemicals 
manufacturing.
c. PB-HAP Methodology
    The environmental screening assessment includes six PB-HAP, arsenic 
compounds, cadmium compounds, dioxins/furans, POM, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. With the 
exception of lead, the environmental risk screening assessment for PB-
HAP consists of three tiers. The first tier of the environmental risk 
screening assessment uses the same health-protective conceptual model 
that is used for the Tier 1 human health screening assessment. 
TRIM.FaTE model simulations were used to back-calculate Tier 1 
screening threshold emission rates. The screening threshold emission 
rates represent the emission rate in 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, we evaluate the 
facility further in Tier 2.
    In Tier 2 of the environmental screening assessment, the screening 
threshold emission rates are adjusted to account for local meteorology 
and the actual location of lakes in the vicinity of facilities that did 
not pass the Tier 1 screening assessment. For soils, we evaluate the 
average soil concentration for all soil parcels within a 7.5-km radius 
for each facility and PB-HAP. For the water, sediment, and fish tissue 
concentrations, the highest value for each facility for each pollutant 
is used. If emission concentrations from a facility do not exceed the 
Tier 2 screening threshold emission rate, the facility ``passes'' the 
screening assessment and typically is not evaluated further. If 
emissions from a facility exceed the Tier 2 screening threshold 
emission rate, we evaluate the facility further in Tier 3.
    As in the multipathway human health risk assessment, in Tier 3 of 
the environmental screening assessment, we examine the suitability of 
the lakes around the facilities to support life and remove those that 
are not suitable (e.g., lakes that have been filled in or are 
industrial ponds), adjust emissions for plume-rise, and conduct hour-
by-hour time-series assessments. If these Tier 3 adjustments to the 
screening threshold emission rates still indicate the potential for an 
adverse environmental effect (i.e., facility emission rate exceeds the 
screening threshold emission rate), we may elect to conduct a more 
refined assessment using more site-specific information. If, after 
additional refinement, the facility emission rate still exceeds the 
screening threshold emission rate, the facility may have the potential 
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from 
lead, we compared the average modeled air concentrations (from HEM-3) 
of lead around each facility in the source category to the level of the 
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable 
means of evaluating environmental risk because it is set to provide 
substantial protection against adverse welfare effects which can 
include ``effects on soils, water, crops, vegetation, man-made 
materials, animals, wildlife, weather, visibility and climate, damage 
to and deterioration of property, and hazards to transportation, as 
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the 
potential phytotoxicity and reduced productivity of plants due to 
chronic exposure to HF and HCl. The environmental risk screening 
methodology for acid gases is a single-tier screening assessment that 
compares modeled ambient air concentrations (from AERMOD) to the 
ecological benchmarks for each acid gas. To identify a potential 
adverse environmental effect (as defined in section 112(a)(7) of the 
CAA) from emissions of HF and HCl, we evaluate the following metrics: 
the size of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas, in acres and 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 Cyanide Chemicals Manufacturing

[[Page 3918]]

Source Category in Support of the Risk and Technology Review 2020 
Proposed Rule, which is available in the docket for this action.
6. How do we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine 
the risks from the entire ``facility,'' where the facility includes all 
HAP-emitting operations within a contiguous area and under common 
control. In other words, we examine the HAP emissions not only from the 
source category emission points of interest, but also emissions of HAP 
from all other emission sources at the facility for which we have data. 
For this source category, we conducted the facility-wide assessment 
using a dataset compiled from the 2017 NEI. The source category records 
of that NEI dataset were removed, evaluated, and updated as described 
in section II.C of this preamble: What data collection activities were 
conducted to support this action? Once a quality assured source 
category dataset was available, it was placed back with the remaining 
records from the NEI for that facility. The facility-wide file was then 
used to analyze risks due to the inhalation of HAP that are emitted 
``facility-wide'' for the populations residing within 50 km of each 
facility, consistent with the methods used for the source category 
analysis described above. For these facility-wide risk analyses, the 
modeled source category risks were compared to the facility-wide risks 
to determine the portion of the facility-wide risks that could be 
attributed to the source category addressed in this proposal. We also 
specifically examined the facility that was associated with the highest 
estimate of risk and determined the percentage of that risk 
attributable to the source category of interest. The Residual Risk 
Assessment for the Cyanide Chemicals Manufacturing Source Category in 
Support of the Risk and Technology Review 2020 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.
    For this source category, we conducted the facility-wide assessment 
using a dataset that the EPA compiled from the 2017 NEI. We used the 
NEI data for the facility and did not adjust any category or ``non-
category'' data. Therefore, there could be differences in the dataset 
from that used for the source category assessments described in this 
preamble. We analyzed risks due to the inhalation of HAP that are 
emitted ``facility-wide'' for the populations residing within 50 km of 
each facility, consistent with the methods used for the source category 
analysis described above. For these facility-wide risk analyses, we 
made a reasonable attempt to identify the source category risks, and 
these risks were compared to the facility-wide risks to determine the 
portion of facility-wide risks that could be attributed to the source 
category addressed in this proposal. We also specifically examined the 
facility that was associated with the highest estimate of risk and 
determined the percentage of that risk attributable to the source 
category of interest. The Residual Risk Assessment for the Cyanide 
Chemicals Manufacturing Source Category in Support of the Risk and 
Technology Review 2020 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.
7. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk 
assessments, including those performed for this proposal. Although 
uncertainty exists, we believe that our approach, which used 
conservative tools and assumptions, ensures that our decisions are 
health and environmentally protective. A brief discussion of the 
uncertainties in the RTR emissions 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 
Cyanide Chemicals Manufacturing Source Category in Support of the Risk 
and Technology Review 2020 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 do not 
reflect short-term fluctuations during the course of a year or 
variations from year to year. The estimates of peak hourly emission 
rates for the acute effects screening assessment were based on an 
emission adjustment factor applied to the average annual hourly 
emission rates, which are intended to account for emission fluctuations 
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration 
estimates associated with any model, including the EPA's recommended 
regulatory dispersion model, AERMOD. In using a model to estimate 
ambient pollutant concentrations, the user chooses certain options to 
apply. For RTR assessments, we select some model options that have the 
potential to overestimate ambient air concentrations (e.g., not 
including plume depletion or pollutant transformation). We select other 
model options that have the potential to underestimate ambient impacts 
(e.g., not including building downwash). Other options that we select 
have the potential to either under- or overestimate ambient levels 
(e.g., meteorology and receptor locations). On balance, considering the 
directional nature of the uncertainties commonly present in ambient 
concentrations estimated by dispersion models, the approach we apply in 
the RTR assessments should yield unbiased estimates of ambient HAP 
concentrations. We also note that the selection of meteorology dataset 
location could have an impact on the risk estimates. As we continue to 
update and expand our library of meteorological station data used in 
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant 
facilities and emission points, as well as to develop accurate 
estimates of the annual emission rates for all relevant HAP, the 
uncertainties in our emission inventory likely dominate the 
uncertainties in the exposure assessment. Some uncertainties in our 
exposure assessment include human mobility,

[[Page 3919]]

using the centroid of each census block, assuming lifetime exposure, 
and assuming only outdoor exposures. For most of these factors, there 
is neither an under nor overestimate when looking at the maximum 
individual risk or the incidence, but the shape of the distribution of 
risks may be affected. With respect to outdoor exposures, actual 
exposures may not be as high if people spend time indoors, especially 
for very reactive pollutants or larger particles. For all factors, we 
reduce uncertainty when possible. For example, with respect to census-
block centroids, we analyze large blocks using aerial imagery and 
adjust locations of the block centroids to better represent the 
population in the blocks. We also add additional receptor locations 
where the population of a block is not well represented by a single 
location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and noncancer effects from both chronic and acute 
exposures. Some uncertainties are generally expressed quantitatively, 
and others are generally expressed in qualitative terms. We note, as a 
preface to this discussion, a point on dose-response uncertainty that 
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment; 
namely, that ``the primary goal of EPA actions is protection of human 
health; accordingly, as an Agency policy, risk assessment procedures, 
including default options that are used in the absence of scientific 
data to the contrary, should be health protective'' (the EPA's 2005 
Guidelines for Carcinogen Risk Assessment, pages 1 through 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.\19\ 
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.\20\ 
Chronic noncancer RfC and reference dose (RfD) 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,\21\ 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.
---------------------------------------------------------------------------

    \19\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \20\ 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.
    \21\ 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.
---------------------------------------------------------------------------

    Many of the UFs used to account for variability and uncertainty in 
the development of acute dose-response values are quite similar to 
those developed for chronic durations. Additional adjustments are often 
applied to account for uncertainty in extrapolation from observations 
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all 
acute dose-response values are developed for the same purpose, and care 
must be taken when interpreting the results of an acute assessment of 
human health effects relative to the dose-response value or values 
being exceeded. Where relevant to the estimated exposures, the lack of 
acute dose-response values at different levels of severity should be 
factored into the risk characterization as potential uncertainties.
    Uncertainty also exists in the selection of ecological benchmarks 
for the environmental risk screening assessment. We established a 
hierarchy of preferred benchmark sources to allow selection of 
benchmarks for each environmental HAP at each ecological assessment 
endpoint. We searched for benchmarks for three effect levels (i.e., no-
effects level, threshold-effect level, and probable effect level), but 
not all combinations of ecological assessment/environmental HAP had 
benchmarks for all three effect levels. Where multiple effect levels 
were available for a particular HAP and assessment endpoint, we used 
all of the available effect levels to help us determine whether risk 
exists and whether the risk could be considered significant and 
widespread.
    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, we generally rely on site-specific levels 
of PB-HAP or environmental HAP emissions to determine whether a refined 
assessment of the impacts from multipathway exposures is necessary or 
whether it is necessary to perform an environmental screening 
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant 
concentrations and human exposures for five PB-HAP (dioxins, POM, 
mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For 
lead, we use AERMOD to determine ambient air concentrations, which are 
then compared to the secondary NAAQS standard for lead. Two important 
types of uncertainty associated with the use of these models in RTR 
risk assessments and inherent to any assessment that relies on

[[Page 3920]]

environmental modeling are model uncertainty and input uncertainty.\22\
---------------------------------------------------------------------------

    \22\ In the context of this discussion, the term ``uncertainty'' 
as it pertains to exposure and risk encompasses both variability in 
the range of expected inputs and screening results due to existing 
spatial, temporal, and other factors, as well as uncertainty in 
being able to accurately estimate the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the model adequately represents 
the actual processes (e.g., movement and accumulation) that might occur 
in the environment. For example, does the model adequately describe the 
movement of a pollutant through the soil? This type of uncertainty is 
difficult to quantify. However, based on feedback received from 
previous EPA SAB reviews and other reviews, we are confident that the 
models used in the screening assessments are appropriate and state-of-
the-art for the multipathway and environmental screening risk 
assessments conducted in support of RTRs.
    Input uncertainty is concerned with how accurately the models have 
been configured and parameterized for the assessment at hand. For Tier 
1 of the multipathway and environmental screening assessments, we 
configured the models to avoid underestimating exposure and risk. This 
was accomplished by selecting upper-end values from nationally 
representative datasets for the more influential parameters in the 
environmental model, including selection and spatial configuration of 
the area of interest, lake location and size, meteorology, surface 
water, soil characteristics, and structure of the aquatic food web. We 
also assume an ingestion exposure scenario and values for human 
exposure factors that represent reasonable maximum exposures.
    In Tier 2 of the multipathway and environmental screening 
assessments, we refine the model inputs to account for meteorological 
patterns in the vicinity of the facility versus using upper-end 
national values, and we identify the actual location of lakes near the 
facility rather than the default lake location that we apply in Tier 1. 
By refining the screening approach in Tier 2 to account for local 
geographical and meteorological data, we decrease the likelihood that 
concentrations in environmental media are overestimated, thereby 
increasing the usefulness of the screening assessment. In Tier 3 of the 
screening assessments, we refine the model inputs again to account for 
hour-by-hour plume-rise and the height of the mixing layer. We can also 
use those hour-by-hour meteorological data in a TRIM.FaTE run using the 
screening configuration corresponding to the lake location. These 
refinements produce a more accurate estimate of chemical concentrations 
in the media of interest, thereby reducing the uncertainty with those 
estimates. The assumptions and the associated uncertainties regarding 
the selected ingestion exposure scenario are the same for all three 
tiers.
    For the environmental screening assessment for acid gases, we 
employ a single-tiered approach. We use the modeled air concentrations 
and compare those with ecological benchmarks.
    For all tiers of the multipathway and environmental screening 
assessments, our approach to addressing model input uncertainty is 
generally cautious. We choose model inputs from the upper end of the 
range of possible values for the influential parameters used in the 
models, and we assume that the exposed individual exhibits ingestion 
behavior that would lead to a high total exposure. This approach 
reduces the likelihood of not identifying high risks for adverse 
impacts.
    Despite the uncertainties, when individual pollutants or facilities 
do not exceed screening threshold emission rates (i.e., screen out), we 
are confident that the potential for adverse multipathway impacts on 
human health is very low. On the other hand, when individual pollutants 
or facilities do exceed screening threshold emission rates, it does not 
mean that impacts are significant, only that we cannot rule out that 
possibility and that a refined assessment for the site might be 
necessary to obtain a more accurate risk characterization for the 
source category.
    The EPA evaluates the following HAP in the multipathway and/or 
environmental risk screening assessments, where applicable: Arsenic, 
cadmium, dioxins/furans, lead, mercury (both inorganic and methyl 
mercury), POM, HCl, and HF. These HAP represent pollutants that can 
cause adverse impacts either through direct exposure to HAP in the air 
or through exposure to HAP that are deposited from the air onto soils 
and surface waters and then through the environment into the food web. 
These HAP represent those HAP for which we can conduct a meaningful 
multipathway or environmental screening risk assessment. For other HAP 
not included in our screening assessments, the model has not been 
parameterized such that it can be used for that purpose. In some cases, 
depending on the HAP, we may not have appropriate multipathway models 
that allow us to predict the concentration of that pollutant. The EPA 
acknowledges that other HAP beyond these that we are evaluating may 
have the potential to cause adverse effects and, therefore, the EPA may 
evaluate other relevant HAP in the future, as modeling science and 
resources allow.

IV. Analytical Results and Proposed Decisions

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

    We are proposing standards pursuant to CAA section 112(d)(2) for 
process wastewater from existing cyanide chemical manufacturing process 
units, which was previously unregulated.\23\ During development of the 
initial MACT standards, we identified process wastewater at existing 
sources as a potential source of emissions of hydrogen cyanide, 
acetonitrile, and acrylonitrile. See 65 FR 76408, 76411, and 76413, 
December 6, 2000, for a discussion of the HAP emitted from cyanide 
chemicals manufacturing. At that time, we identified measures 
undertaken at cyanide chemicals manufacturing facilities to comply with 
other NESHAP as the ``MACT floor,'' but we did not include these 
measures in 40 CFR part 63, subpart YY for existing cyanide chemical 
manufacturing process units. Based on our review, we are proposing to 
find that these measures reflect the best performing sources in the 
source category. The results and proposed decisions based on the 
analyses performed pursuant to CAA section 112(d)(2) and (3) are 
presented below.
---------------------------------------------------------------------------

    \23\ The EPA not only has authority under CAA section 112(d)(2) 
and (3) to set MACT standards for previously unregulated HAP 
emissions at any time, but is required to address any previously 
unregulated HAP emissions as part of its periodic review of MACT 
standards under CAA section 112(d)(6). LEAN v. EPA, 955 F3d at 1091-
1099.
---------------------------------------------------------------------------

    For this proposal, we reviewed title V permits for facilities 
subject to the Cyanide Chemicals Manufacturing NESHAP and determined 
that all cyanide chemicals manufacturing facilities are co-located with 
processes subject to the Hazardous Organic NESHAP (HON) or 
substantively similar requirements. In the 2000 NESHAP proposal, we 
stated that wastewater treatment units at cyanide chemicals 
manufacturing facilities are typical of synthetic organic chemicals 
manufacturing facilities subject to the HON. The wastewater 
requirements of the HON are already an approved means of compliance for 
wastewater emission sources subject to 40 CFR part 63, subpart YY as 
stated in 40 CFR 63.1100(g)(5). We are proposing to require compliance 
with HON wastewater requirements for process

[[Page 3921]]

wastewater at existing sources, which will ensure all affected sources 
at cyanide chemicals manufacturing facilities are subject to MACT 
standards. We are proposing these requirements for cyanide chemicals 
manufacturing existing sources because such requirements represent: (1) 
The measures employed by the best performing sources in the category; 
and (2) an already acceptable means of compliance for wastewater 
emissions at sources subject to subpart YY. We believe that these 
requirements will not require additional controls or emissions 
reductions since existing sources we have identified as subject to the 
Cyanide Chemicals Manufacturing NESHAP are already subject to the HON 
or substantively identical wastewater requirements in another NESHAP.
    We are also adding the HON requirements for waste management units 
upstream of an open or closed biological treatment process to the new 
source standard to ensure demonstrable compliance measures are in place 
for these sources; however, we believe these measures would already be 
employed by any new sources to achieve the combined 93 percent capture 
and control of HAP emissions from wastewater required for process 
wastewater emissions at new sources subject to the Cyanide Chemicals 
Manufacturing NESHAP.
    We have identified three HAP that may be present in process 
wastewater streams at cyanide chemicals manufacturing facilities: 
Hydrogen cyanide, acetonitrile, and acrylonitrile. We are proposing to 
include hydrogen cyanide in the calculations required to determine 
compliance with the wastewater standard for the Cyanide Chemicals 
Manufacturing source category to ensure all HAP potentially present in 
process wastewater are subject to MACT standards. The other two HAP 
that may be present in cyanide chemicals manufacturing wastewater 
(acetonitrile and acrylonitrile) are already included in the list of 
compounds subject to the HON wastewater provisions. We do not expect 
significant amounts of hydrogen cyanide to be present in these process 
wastewater streams. When developing the 2002 NESHAP, facilities that 
were surveyed reported very low levels of hydrogen cyanide in their 
wastewaters with one exception. The only facility that had high levels 
of hydrogen cyanide in its wastewater used add-on controls to remove 
the hydrogen cyanide prior to discharge. That facility was the basis 
for the ``new source'' MACT floor. We expect any facilities with high 
levels of hydrogen cyanide in their wastewater would already possess 
add-on controls similar to those present at the single existing source 
with high levels of hydrogen cyanide in order to meet effluent 
discharge limits and protect the biological wastewater treatment 
systems used at these facilities. We are including hydrogen cyanide in 
these calculations to ensure that all HAP emitted by the source 
category are subject to MACT standards.
    Nevertheless, we are seeking comment on whether facilities would 
need to install additional controls, achieve additional emissions 
reductions, or incur significant costs as a result of the proposed 
standards for process wastewater. For this proposed rule, we did not 
identify any new control technologies or developments in existing 
technologies to evaluate as ``beyond-the-floor'' controls other than 
the controls evaluated during the initial MACT standards. We did not 
find any data to support changing the conclusion that application of 
the new source MACT limit for process wastewater emissions to existing 
sources is unreasonable (See 65 FR 76419 and Docket Item No. EPA-HQ-
OAR-2004-0041-0003).

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

1. Chronic Inhalation Risk Assessment Results
    The EPA estimated inhalation risk based on actual and allowable 
emissions, which we determined are the same for this category. The 
estimated baseline inhalation MIR posed by the source category is 5-in-
1 million based on actual emissions and MACT-allowable emissions. The 
total estimated cancer incidence based on actual or allowable emission 
levels is 0.004 excess cancer cases per year, or one case every 250 
years. Emissions of acrylonitrile from process vents account for 95 
percent of the cancer incidence. Approximately 61,653 people are 
exposed to cancer risk greater than or equal to 1-in-1 million based 
upon actual and allowable emissions (see Table 1 of this preamble).
    The maximum chronic noncancer TOSHI values for the source category 
were estimated to be 1 for neurological effects based on actual and 
allowable emissions. For both actual and allowable emissions, risk was 
driven by hydrogen cyanide emissions from process vents, wastewater, 
and equipment leaks.

            TABLE 1--Inhalation Risk Assessment Summary For Cyanide Chemicals Manufacturing \1\ Source Category (40 CFR Part 63, Subpart YY)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Maximum        Estimated       Estimated
                                                         individual     population at   annual cancer
           Risk assessment                Number of    cancer risk (1- increased risk     incidence         Maximum chronic      Maximum screening acute
                                       facilities \2\   in-1 million)  of cancer >= 1-   (cases per       noncancer TOSHI \4\        noncancer HQ \5\
                                                             \3\        in-1 million        year)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Baseline Actual Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category......................              13               5          61,653           0.004  1 (neurological)........  1 (REL)
Facility-Wide........................              13             200         266,532            0.04  1 (neurological)........  .......................
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Baseline Allowable Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category......................              13               5          61,653           0.004  1 (neurological)........  .......................
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Based on actual and allowable emissions.
\2\ Number of facilities evaluated in the risk assessment. Includes 13 operating facilities subject to 40 CFR part 63, subpart YY.
\3\ Maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\4\ Maximum TOSHI. The target organ with the highest TOSHI for the Cyanide Chemicals Manufacturing source category is the neurological system.
\5\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. The acute
  HQ shown was based upon the lowest acute 1-hour dose-response value, the REL for hydrogen cyanide. When an HQ exceeds 1, we also show the HQ using the
  next lowest available acute dose-response value.


[[Page 3922]]

2. Screening Level Acute Risk Assessment Results
    Based on our screening analysis of reasonable worst-case acute 
exposure to actual emissions from the category, no HAP exposures result 
in an HQ greater than 1 based upon the 1-hour REL. As discussed in 
section III.C.3.c of this preamble, for this source category, we used 
acute factors between 2 and 10, depending on the type of source. 
Specifically, we used a factor of 2 for process vents and equipment 
leaks, a factor of 4 for storage vessels, and a factor of 10 for 
transfer racks. A further discussion of why these factors were chosen 
can be found in the memorandum, Technical Support Document for the 
Cyanide Chemicals Manufacturing NESHAP Residual Risk and Technology 
Review Proposal, available in the docket for this rulemaking.
3. Multipathway Risk Screening Results
    Three of the 13 facilities in this source category reported 
emissions of PB-HAP in the NEI which include POM (of which polycyclic 
aromatic hydrocarbons is a subset), lead compounds, arsenic compounds, 
cadmium compounds, and mercury compounds. We note that for the Cyanide 
Chemicals Manufacturing source category, while we modeled these 
emissions, none of these HAP are expected to be emitted from the source 
category and they were only modeled to provide a conservative estimate 
of risk because they were included in the NEI. To identify potential 
multipathway health risks from PB-HAP other than lead, we first 
performed a tiered screening assessment (Tiers 1, 2, and 3) based on 
emissions of PB-HAP emitted from each facility in the source category. 
Arsenic emissions from a single facility exceeded the Tier 1 cancer 
screening threshold emission rate with a maximum SV of 2. No facilities 
had POM emissions exceeding the Tier 1 cancer screening threshold 
emission rate. Mercury emissions from a single facility exceeded the 
Tier 1 noncancer screening threshold emission rate with a maximum SV of 
2. No facilities had cadmium emissions exceeding the Tier 1 noncancer 
screening threshold emission rate. For the facilities and HAP for which 
the Tier 1 threshold emissions rates were exceeded (i.e., SV greater 
than 1), we conducted a Tier 2 screening analysis. In the Tier 2 
screening analysis, no facilities had an SV greater than 1. 
Specifically, the maximum Tier 2 cancer SV was less than 1 for both the 
farmer scenario for arsenic (0.4) and the fisher scenario for mercury 
(0.3).
    Further facility details on the multipathway screening analysis can 
be found in Appendix 10 of the Residual Risk Assessment for the Cyanide 
Chemical Manufacturing Source Category in Support of the Risk and 
Technology Review 2020 Proposed Rule.
    An SV in any of the tiers is not an estimate of the cancer risk or 
a noncancer HQ. Rather, an SV represents a high-end estimate of what 
the risk or HQ may be. For example, facility emissions resulting in an 
SV of 2 for a non-carcinogen can be interpreted to mean that we are 
confident that the HQ would be lower than 2. Similarly, facility 
emissions resulting in a cancer SV of 20 for a carcinogen means that we 
are confident that the cancer risk is lower than 20-in-1 million. Our 
confidence comes from the health-protective assumptions that are 
incorporated into the screens: We choose inputs from the upper end of 
the range of possible values for the influential parameters used in the 
screens and we assume food consumption behaviors that would lead to 
high total exposure. This risk assessment estimates the maximum hazard 
for mercury and cadmium through fish consumption based on upper bound 
screens and the maximum excess cancer risks from POM and arsenic 
through ingestion of fish and farm produce.
    In evaluating the potential for adverse health effects from 
emissions of lead, the EPA compared modeled annual lead concentrations 
to the secondary NAAQS level for lead (0.15 [mu]g/m\3\, arithmetic mean 
concentration over a 3-month period). The highest annual average lead 
concentration, 0.00000065 [micro]g/m\3\, is orders of magnitude below 
the NAAQS level for lead, indicating a low potential for adverse health 
impacts.
4. Environmental Risk Screening Results
    As described in section III.A of this preamble, we conducted an 
environmental risk screening assessment for the Cyanide Chemical 
Manufacturing source category for the following pollutants: arsenic, 
cadmium, HCl, lead, mercury (methyl mercury and mercuric chloride), and 
POM. As noted in our discussion of the multipathway risk assessment 
results, these HAP are not associated with cyanide chemicals 
manufacturing and are not emitted from the source category. There were 
NEI entries for small amounts of these pollutants and we chose to model 
these emissions to err on the side of an overly conservative 
assessment.
    In the Tier 1 screening analysis for the above PB-HAP (other than 
lead, which was evaluated differently), the maximum Tier 1 SV was less 
than or equal to 1 for all PB-HAP.
    For lead, we did not estimate any exceedances of the secondary lead 
NAAQS. For HCl, the average modeled concentration around each facility 
(i.e., the average concentration of all off-site data points in the 
modeling domain) did not exceed any ecological benchmark. In addition, 
for the one facility that reported HCl emissions, each individual 
modeled concentration of HCl (i.e., each off-site data point in the 
modeling domain) was below the ecological benchmarks for HCl.
    Based on the results of the environmental risk screening analysis, 
we do not expect an adverse environmental effect as a result of HAP 
emissions from this source category.
5. Facility-Wide Risk Results
    The EPA estimated inhalation risk based on facility-wide emissions. 
The estimated maximum individual excess lifetime cancer risk based on 
facility-wide emissions was 200-in-1 million, with 0.04 excess cancer 
cases per year, or one case every 25 years. This cancer risk is driven 
by emissions sources that are not in the Cyanide Chemicals 
Manufacturing source category; specifically, emissions of ethylene 
oxide and coke oven emissions from non-category sources account for 95 
percent of the cancer incidence. Approximately 150 people are exposed 
to an excess cancer risk greater than or equal to 100-in-1 million, 
with 266,532 people exposed to an excess cancer risk above 1-in-1 
million (see Table 1 of this preamble). The estimated maximum chronic 
noncancer TOSHI values for the facility-wide assessment was the same as 
estimated based on actual and allowable emissions from the source 
category--a TOSHI equal to 1 for neurological effects driven by 
hydrogen cyanide emissions from process vents, wastewater, and 
equipment leaks.
    Regarding the facility-wide risks due to ethylene oxide, which are 
emitted by sources that are not part of the Cyanide Chemicals 
Manufacturing source category, we intend to continue to evaluate those 
facility-wide estimated emissions and risks further and may address 
these in separate actions, as appropriate. In particular, the EPA is 
addressing ethylene oxide in response to the results of the latest NATA 
released in August 2018, which identified the chemical as a potential 
concern in several areas across the country (NATA is the Agency's 
nationwide air toxics screening tool, designed to help the EPA and 
state, local, and tribal air agencies identify areas, pollutants, or 
types of sources for

[[Page 3923]]

further examination). The latest NATA estimates that ethylene oxide 
significantly contributes to potential elevated cancer risks in some 
census tracts across the U.S. (less than 1 percent of the total number 
of tracts). These elevated risks are largely driven by an EPA risk 
value that was updated in late 2016. The EPA will work with industry 
and state, local, and tribal air agencies as the EPA takes a two-
pronged approach to address ethylene oxide emissions by: (1) Reviewing 
and, as appropriate, revising CAA regulations for facilities that emit 
ethylene oxide--starting with air toxics emissions standards for 
miscellaneous organic chemical manufacturing facilities (85 FR 49084, 
August 12, 2020) and commercial sterilizers; and (2) conducting site-
specific risk assessments and, as necessary, implementing emission 
control strategies for targeted high-risk facilities. The EPA will post 
updates on its work to address ethylene oxide on its website at: 
https://www.epa.gov/ethylene-oxide.
6. What demographic groups might benefit from this regulation?
    To examine the potential for any environmental justice issues that 
might be associated with the source category, we performed a 
demographic analysis, which is an assessment of risk to individual 
demographic groups of the populations living within 5 km and within 50 
km of the facilities. In the analysis, we evaluated the distribution of 
HAP-related cancer and noncancer risk from the Cyanide Chemicals 
Manufacturing source category across different demographic groups 
within the populations living near facilities.\24\
---------------------------------------------------------------------------

    \24\ Demographic groups included in the analysis are: White, 
African American, Native American, other races and multiracial, 
Hispanic or Latino, children 17 years of age and under, adults 18 to 
64 years of age, adults 65 years of age and over, adults without a 
high school diploma, people living below the poverty level, people 
living two times the poverty level, and linguistically isolated 
people.
---------------------------------------------------------------------------

    The results of the demographic analysis are summarized in Table 2 
below. These results, for various demographic groups, are based on the 
estimated risk from actual emissions levels for the population living 
within 50 km of the facilities.

                   TABLE 2--Cyanide Chemicals Manufacturing Demographic Risk Analysis Results
----------------------------------------------------------------------------------------------------------------
                                                                                    Population
                                                                                    with cancer     Population
                                                                                    risk at or     with chronic
                                                                                   above 1-in-1   HI above 1 due
                                                                    Nationwide    million due to    to cyanide
                                                                                      cyanide        chemicals
                                                                                     chemicals     manufacturing
                                                                                   manufacturing
----------------------------------------------------------------------------------------------------------------
Total Population................................................     317,746,049          61,653               0
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White...........................................................              62              73  ..............
All Other Races.................................................              38              27  ..............
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White...........................................................              62              73  ..............
African American................................................              12              19  ..............
Native American.................................................             0.8             0.4  ..............
Other and Multiracial...........................................               7               4  ..............
----------------------------------------------------------------------------------------------------------------
                                              Ethnicity by Percent
----------------------------------------------------------------------------------------------------------------
Hispanic........................................................              18               3  ..............
Non-Hispanic....................................................              82              97  ..............
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............................................              14              16  ..............
Above Poverty Level.............................................              86              84  ..............
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without High School Diploma.........................              14              16  ..............
Over 25 and with a High School Diploma..........................              86              84  ..............
----------------------------------------------------------------------------------------------------------------

    The results of the Cyanide Chemicals Manufacturing source category 
demographic analysis indicate that emissions from the source category 
expose approximately 61,653 people to a cancer risk at or above 1-in-1 
million and nobody to a chronic noncancer TOSHI greater than 1. The 
percentages of the at-risk population in the White, African American, 
Below Poverty, and Over 25 without High School Diploma demographic 
groups are greater than their respective nationwide percentages.
    The methodology and the results of the demographic analysis are 
presented in a technical report, Risk and Technology Review--Analysis 
of Demographic Factors for Populations Living Near Cyanide Chemicals 
Manufacturing, available in the docket for this action.

C. What are our proposed decisions regarding risk acceptability, ample 
margin of safety, and adverse environmental effect?

1. Risk Acceptability
    As explained in section II.A of this preamble, the EPA sets 
standards under

[[Page 3924]]

CAA section 112(f)(2) using ``a two-step standard-setting approach, 
with an analytical first step to determine an 'acceptable risk' that 
considers all health information, including risk estimation 
uncertainty, and includes a presumptive limit on maximum individual 
risk (MIR) of approximately 1-in-10 thousand.'' (54 FR 38045, September 
14, 1989). The EPA weighed all health risk measures and information, 
including science policy assumptions and estimation uncertainties, in 
determining whether risk posed by emissions from the source category is 
acceptable.
    The estimated maximum cancer risk for inhalation exposure to actual 
and allowable emissions from the Cyanide Chemicals Manufacturing source 
category was 5-in-1 million, 20 times below 100-in-1 million, which is 
the presumptive upper limit of acceptable risk. The EPA estimates 
emissions from the category would result in a cancer incidence of 0.004 
excess cancer cases per year, or one case every 250 years. Inhalation 
exposures to HAP associated with chronic noncancer health effects 
result in a TOSHI of 1 based on actual and allowable emissions, an 
exposure level that the EPA has determined is without appreciable risk 
of adverse health effects. Exposures to HAP associated with acute 
noncancer health effects also are below levels of health concern with 
no HAP exposures resulting in an HQ greater than 1 based upon the 1-
hour REL.
    Maximum cancer risk due to ingestion exposures, estimated using 
health-protective risk screening assumptions, is below 1-in-1 million 
for the Tier 2 farmer exposure scenario. Tier 2 screening analyses of 
mercury exposure due to fish ingestion determined that the maximum HQ 
for mercury would be less than 1 as explained in section III.C.4 of 
this preamble.
    Considering all of the health risk information and factors 
discussed above, as well as the uncertainties discussed in section III 
of this preamble, we propose that the risks posed by emissions from the 
Cyanide Chemicals Manufacturing source category are acceptable.
2. Ample Margin of Safety Analysis
    As directed by CAA section 112(f)(2), we conducted an analysis to 
determine whether the current emissions standards provide an ample 
margin of safety to protect public health. Under the ample margin of 
safety analysis, we evaluated the cost and feasibility of available 
control technologies and other measures (including the controls, 
measures, and costs reviewed under the technology review) that could be 
applied to this source category to further reduce the risks (or 
potential risks) due to emissions of HAP from the source category. In 
light of the low cancer and noncancer risk posed to individuals exposed 
to HAP emitted from this source category and lack of additional control 
technologies, we are proposing to conclude that the existing standards 
under the NESHAP provide an ample margin of safety to protect public 
health.
3. Adverse Environmental Effect
    Based on the results of our environmental risk screening analysis, 
we do not anticipate an adverse environmental effect as a result of HAP 
emissions from this source category. Therefore, the EPA is proposing 
that it is not necessary to set a more stringent standard to prevent, 
taking into consideration costs, energy, safety, and other relevant 
factors, an adverse environmental effect.

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

    As part of the technology review, we identified a previously 
unregulated process, and are proposing a MACT standard for the process 
under CAA section 112(d)(2) and (3), as described in Section IV.A of 
this preamble, above. We did not identify any developments in 
processes, practices, or control technologies for cyanide chemicals 
manufacturing facilities during our analysis for this proposal. 
Facilities subject to this NESHAP use flares to control emissions from 
point sources and LDAR programs to address emissions from equipment 
leaks. As discussed in the memorandum titled Technical Support Document 
for the Cyanide Chemicals Manufacturing NESHAP Residual Risk and 
Technology Review Proposal, we did not identify any developments in 
these technologies during our technology review.

E. What other actions are we proposing?

    In addition to the proposed actions described above, we are 
proposing additional revisions to the NESHAP. We are proposing 
revisions to the SSM provisions of the MACT rule in order to ensure 
that they are consistent with the decision in Sierra Club v. EPA, 551 
F. 3d 1019 (DC Cir. 2008), in which the court vacated two provisions 
that exempted sources from the requirement to comply with otherwise 
applicable CAA section 112(d) emission standards during periods of SSM. 
We note that for the Cyanide Chemicals Manufacturing source category, 
the NESHAP currently does not include an exemption for SSM events, and 
already includes standards that apply at all times, including periods 
of SSM. Therefore, we have determined that the NESHAP is already 
consistent with the court decision mentioned above. However, we are 
making revisions to the MACT rule at 40 CFR 63.1108 through 40 CFR 
63.1112 to ensure this is clearly and consistently communicated 
throughout and no confusion results from referenced subparts associated 
with the GMACT that may contain SSM exemptions for other source 
categories. We also are proposing other changes to add electronic 
reporting. Our analyses and proposed changes related to these issues 
are discussed below.
    Electronic Reporting. The EPA is proposing that owners and 
operators of cyanide chemicals manufacturing facilities submit 
electronic copies of required notifications of compliance, performance 
test reports, and periodic reports through the EPA's Central Data 
Exchange (CDX) using the Compliance and Emissions Data Reporting 
Interface (CEDRI). A description of the electronic data submission 
process is provided in the memorandum, Electronic Reporting 
Requirements for New Source Performance Standards (NSPS) and National 
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, 
available in the docket for this action. The proposed rule requires 
that performance test results collected using test methods that are 
supported by the EPA's Electronic Reporting Tool (ERT) as listed on the 
ERT website \25\ at the time of the test be submitted in the format 
generated through the use of the ERT or an electronic file consistent 
with the xml schema on the ERT website, and other performance test 
results be submitted in portable document format (PDF) using the 
attachment module of the ERT. The proposed rule requires that 
Notification of Compliance Status (NOCS) be submitted as a PDF upload 
in CEDRI.
---------------------------------------------------------------------------

    \25\ https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.
---------------------------------------------------------------------------

    For periodic reports, the proposed rule requires that owners and 
operators use the appropriate spreadsheet template to submit 
information to CEDRI. A draft version of the proposed template for 
these reports is included in the docket for this action.\26\ The EPA 
specifically requests comment on the content, layout, and overall 
design of the template.
---------------------------------------------------------------------------

    \26\ See Draft Form_5900-
485_Subpart_YY_Cyanide_Draft_Periodic_Report_Template_Proposal.xlsm, 
available at Docket ID No. EPA-HQ-OAR-2020-0532.
---------------------------------------------------------------------------

    Additionally, the EPA has identified two broad circumstances in 
which

[[Page 3925]]

electronic reporting extensions may be provided. These circumstances 
are (1) outages of the EPA's CDX or CEDRI which preclude an owner or 
operator from accessing the system and submitting required reports and 
(2) force majeure events, which are defined as events that will be or 
have been caused by circumstances beyond the control of the affected 
facility, its contractors, or any entity controlled by the affected 
facility that prevent an owner or operator from complying with the 
requirement to submit a report electronically. Examples of force 
majeure events are acts of nature, acts of war or terrorism, or 
equipment failure or safety hazards beyond the control of the facility. 
The EPA is providing these potential extensions to protect owners and 
operators from noncompliance in cases where they cannot successfully 
submit a report by the reporting deadline for reasons outside of their 
control. In both circumstances, the decision to accept the claim of 
needing additional time to report is within the discretion of the 
Administrator, and reporting should occur as soon as possible.
    The electronic submittal of the reports addressed in this proposed 
rulemaking will increase the usefulness of the data contained in those 
reports, is in keeping with current trends in data availability and 
transparency, will further assist in the protection of public health 
and the environment, will improve compliance by facilitating the 
ability of regulated facilities to demonstrate compliance with 
requirements and by facilitating the ability of delegated state, local, 
tribal, and territorial air agencies and the EPA to assess and 
determine compliance, and will ultimately reduce burden on regulated 
facilities, delegated air agencies, and the EPA. Electronic reporting 
also eliminates paper-based, manual processes, thereby saving time and 
resources, simplifying data entry, eliminating redundancies, minimizing 
data reporting errors, and providing data quickly and accurately to the 
affected facilities, air agencies, the EPA, and the public. Moreover, 
electronic reporting is consistent with the EPA's plan \27\ to 
implement Executive Order 13563 and is in keeping with the EPA's 
Agency-wide policy \28\ developed in response to the White House's 
Digital Government Strategy.\29\ For more information on the benefits 
of electronic reporting, see the memorandum, Electronic Reporting 
Requirements for New Source Performance Standards (NSPS) and National 
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, 
referenced earlier in this section.
---------------------------------------------------------------------------

    \27\ EPA's Final Plan for Periodic Retrospective Reviews, August 
2011. Available at: https://www.regulations.gov/document?D=EPA-HQ-OA-2011-0156-0154.
    \28\ E-Reporting Policy Statement for EPA Regulations, September 
2013. Available at: https://www.epa.gov/sites/production/files/2016-03/documents/epa-ereporting-policy-statement-2013-09-30.pdf.
    \29\ Digital Government: Building a 21st Century Platform to 
Better Serve the American People, May 2012. Available at: https://obamawhitehouse.archives.gov/sites/default/files/omb/egov/digital-government/digital-government.html.
---------------------------------------------------------------------------

F. What compliance dates are we proposing?

    The EPA is proposing that existing affected sources and affected 
sources that commenced construction or reconstruction on or before 
January 15, 2021, must comply with the proposed process wastewater 
standards no later than 365 days after the effective date of the final 
rule and all of the other amendments no later than 180 days after the 
effective date of the final rule. The final action is not expected to 
be a ``major rule'' as defined by 5 U.S.C. 804(2), so the effective 
date of the final rule will be the promulgation date as specified in 
CAA section 112(d)(10). For existing sources, we are proposing a change 
that would impact ongoing compliance requirements for 40 CFR part 63, 
subpart YY. As discussed elsewhere in this preamble, we are proposing 
to change the requirements for SSM by removing references to exemptions 
in other subparts. Our experience with similar industries shows that 
this sort of regulated facility generally requires a time period of 180 
days to read and understand the amended rule requirements; to evaluate 
their operations to ensure that they can meet the standards during 
periods of startup and shutdown as defined in the rule and make any 
necessary adjustments; and to update their operations to reflect the 
revised requirements.
    From our assessment of the timeframe needed for compliance with the 
revised requirements, the EPA considers a period of 180 days to be the 
most expeditious compliance period practicable, and, thus, is proposing 
that existing affected sources be in compliance with this regulation's 
revised requirements within 180 days of the regulation's effective 
date. We solicit comment on this proposed compliance period, and we 
specifically request submission of information from sources in this 
source category regarding specific actions that would need to be 
undertaken to comply with the proposed amended requirements, including 
the proposed amendments related to recordkeeping and reporting and the 
time needed to make the adjustments for compliance with them. We note 
that information provided may result in changes to the proposed 
compliance date; however, we expect the proposed compliance time to be 
sufficient given that cyanide chemicals manufacturing facilities are 
already subject to standards during these periods. We are proposing 
that facilities will have 1 year to comply with the proposed process 
wastewater standards for existing sources. We note that we do not 
expect the proposed wastewater standards for existing sources to 
require installation of any additional controls. We believe that all 
affected sources are already complying with the proposed wastewater 
requirements or requirements that are substantively identical. We are 
proposing that facilities must comply within 365 days in order to 
provide time to evaluate wastewater operations, perform compliance 
calculations, and adjust plans and reports as necessary. We are seeking 
comment on the assumption that facilities will not need to install 
additional add-on controls and whether facilities would require more or 
less time to comply with the proposed process wastewater requirements. 
Affected sources that commence construction or reconstruction after 
January 15, 2021, must comply with all requirements of the subpart, 
including the amendments being proposed, no later than the effective 
date of the final rule or upon startup, whichever is later. All 
affected facilities would have to continue to meet the current 
requirements of 40 CFR part 63, subpart YY, until the applicable 
compliance date of the amended rule.

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    There are 13 cyanide chemicals manufacturing facilities currently 
operating as major sources of HAP subject to the proposed amendments. A 
list of facilities that are currently subject to the MACT standards is 
available in the memorandum titled Technical Support Document for the 
Cyanide Chemicals Manufacturing NESHAP Residual Risk and Technology 
Review Proposal, available in Docket ID No. EPA-HQ-OAR-2020-0532.

B. What are the air quality impacts?

    We do not anticipate that the proposed amendments to this subpart 
will impact air quality. We are not proposing changes to the standard 
that

[[Page 3926]]

will result in additional emission reductions beyond the levels already 
achieved by the NESHAP.

C. What are the cost impacts?

    The proposed amendments will have a limited cost impact on affected 
facilities. Total estimated costs are $47,527 based on a $3,656 per 
facility cost for all 13 facilities. The costs result from reading and 
understanding rule requirements and adjusting compliance plans based on 
the rule proposal. All costs are one-time expenses expected to occur in 
the first year after the rule is finalized. Costs are based on Agency 
knowledge and experience with the NESHAP program, related ICRs, and 
Bureau of Labor Statistics data.

D. What are the economic impacts?

    Economic impact analyses focus on changes in market prices and 
output levels. If changes in market prices and output levels in the 
primary markets are significant enough, impacts on other markets may 
also be examined. Both the magnitude of costs associated with the 
proposed requirements and the distribution of these costs among 
affected facilities can have a role in determining how the market will 
change in response to a proposed rule.
    Economic costs to owners of cyanide chemicals manufacturing 
facilities were measured in present value (PV) total costs and 
equivalent annual value (EAV) costs. All cyanide chemicals 
manufacturing facilities were estimated to have similar costs. All 
costs are presented in 2019 dollars. See section V.C of this preamble 
for additional information on costs.
    PV total costs and EAV costs were measured at the 3 percent and 7 
percent discount rates. The duration of analysis was 8 years. Per 
facility PV total cost estimate is $3,656 at the 3 percent and 7 
percent discount rates. The similarity in both discount rates is due to 
the costs all occuring in the first year after the rule is finalized. 
EAV costs per facility are measured to be $521 and $612 at the 3 
percent and 7 percent discount rates, respectively. Combined total PV 
cost of the proposed requirements for all facilities is measured to be 
$47,527 at the 3 percent and 7 percent discount rates. The similarity 
in both discount rates is due to the costs all coming in the first year 
that the rule will be finalized. Combined EAV costs of the proposed 
requirements for all facilities are measured to be $6,771 and $7,959 at 
the 3 percent and 7 percent discount rates, respectively.
    As required by the Regulatory Flexibility Act (RFA), we performed 
an analysis to determine if any small entities would be unduly burdened 
by the proposed amendments. We determined that all facilities subject 
to the NESHAP are owned by large parent entities based on Small 
Business Administration standards. No significant economic impacts from 
the proposed amendments are anticipated because the PV and EAV costs 
associated with the proposed revisions are minimal.

E. What are the benefits?

    As discussed in section V.B of this preamble, we do not anticipate 
the proposed amendments to this subpart to impact air quality. The 
electronic submittal of the reports addressed in this proposed 
rulemaking will increase the usefulness of the data contained in those 
reports, is in keeping with current trends in data availability and 
transparency, will further assist in the protection of public health 
and the environment, will improve compliance by facilitating the 
ability of regulated facilities to demonstrate compliance with 
requirements, and by facilitating the ability of delegated state, 
local, tribal, and territorial air agencies and the EPA to assess and 
determine compliance, and will ultimately reduce burden on regulated 
facilities, delegated air agencies, and the EPA. Electronic reporting 
also eliminates paper-based, manual processes, thereby saving time and 
resources, simplifying data entry, eliminating redundancies, minimizing 
data reporting errors, and providing data quickly and accurately to the 
affected facilities, air agencies, the EPA, and the public.

VI. Request for Comments

    We solicit comments on this proposed action. In addition to general 
comments on this proposed action, we are also interested in additional 
data that may improve the risk assessments and other analyses. We are 
specifically interested in receiving any improvements to the data used 
in the site-specific emissions profiles used for risk modeling. Such 
data should include supporting documentation in sufficient detail to 
allow characterization of the quality and representativeness of the 
data or information. Section VII of this preamble provides more 
information on submitting data.

VII. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses and instructions are available for 
download on the RTR website at https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen. The data files include detailed information for each HAP 
emissions release point for the facilities in the source category.
    If you believe that the data are not representative or are 
inaccurate, please identify the data in question, provide your reason 
for concern, and provide any ``improved'' data that you have, if 
available. When you submit data, we request that you provide 
documentation of the basis for the revised values to support your 
suggested changes. To submit comments on the data downloaded from the 
RTR website, complete the following steps:
    1. Within this downloaded file, enter suggested revisions to the 
data fields appropriate for that information.
    2. Fill in the commenter information fields for each suggested 
revision (i.e., commenter name, commenter organization, commenter email 
address, commenter phone number, and revision comments).
    3. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations).
    4. Send the entire downloaded file with suggested revisions in 
Microsoft[supreg] Access format and all accompanying documentation to 
Docket ID No. EPA-HQ-OAR-2020-0532 (through the method described in the 
ADDRESSES section of this preamble).
    5. If you are providing comments on a single facility or multiple 
facilities, you need only submit one file for all facilities. The file 
should contain all suggested changes for all sources at that facility 
(or facilities). We request that all data revision comments be 
submitted in the form of updated Microsoft[supreg] Excel files that are 
generated by the Microsoft[supreg] Access file. These files are 
provided on the project website at https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen.

VIII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Orders 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is not a significant regulatory action and was, 
therefore, not submitted to OMB for review.

[[Page 3927]]

B. Executive Order 13771: Reducing Regulations and Controlling 
Regulatory Costs

    This action is not expected to be an Executive Order 13771 
regulatory action because this action is not significant under 
Executive Order 12866.

C. Paperwork Reduction Act (PRA)

    The information collection activities in this proposed rule have 
been submitted to the OMB under the PRA. The Information Collection 
Request (ICR) document that the EPA prepared has been assigned EPA ICR 
number 2678.01. You can find a copy of the ICR in the docket for this 
rule, and it is briefly summarized here.
    The EPA is proposing amendments that revise provisions pertaining 
to emissions during periods of SSM, add requirements for electronic 
reporting of NOCS, periodic reports, and performance test results, and 
make other minor clarifications and corrections. This information will 
be collected to assure compliance with the Cyanide Chemicals 
Manufacturing NESHAP.
    Respondents/affected entities: Owners or operators of cyanide 
chemicals manufacturing facilities.
    Respondent's obligation to respond: Mandatory (40 CFR part 63, 
subpart YY).
    Estimated number of respondents: 13 (assumes no new respondents 
over the next 3 years).
    Frequency of response: Initially, occasionally, and annually.
    Total estimated burden: 160 hours (per year) to comply with all of 
the requirements in the NESHAP. Burden is defined at 5 CFR 1320.3(b).
    Total estimated cost: $15,800 (per year), including no annualized 
capital or operation and maintenance costs, to comply with all of the 
requirements in the NESHAP.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to <a href="/cdn-cgi/l/email-protection#1d52544f5c426e687f70746e6e7472735d72707f3378726d337a726b"><span class="__cf_email__" data-cfemail="a2edebf0e3fdd1d7c0cfcbd1d1cbcdcce2cdcfc08cc7cdd28cc5cdd4">[email protected]</span></a>, Attention: Desk Officer for the 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after receipt, OMB must receive comments no 
later than February 16, 2021. The EPA will respond to any ICR-related 
comments in the final rule.

D. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. There are no 
small entities among the eight ultimate parent companies impacted by 
this proposed action given the Small Business Administration small 
business size definition for this industry (1,000 employees or greater 
for NAICS 325180--Other Basic Inorganic Chemical Manufacturing), and no 
significant economic impact on any of these entities.

E. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or 
more as described in UMRA, 2 U.S.C. 1531-1538, and does not 
significantly or uniquely affect small governments. The action imposes 
no enforceable duty on any state, local, or tribal governments or the 
private sector.

F. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

G. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications as specified in 
Executive Order 13175. None of the cyanide chemicals manufacturing 
production facilities that have been identified as being affected by 
this proposed action are owned or operated by tribal governments or 
located within tribal lands. Thus, Executive Order 13175 does not apply 
to this action.

H. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    This action is not subject to Executive Order 13045 because the EPA 
does not believe the environmental health risks or safety risks 
addressed by this action present a disproportionate risk to children. 
This action's health and risk assessments are contained in section IV.B 
of this preamble and the document, Residual Risk Assessment for the 
Cyanide Chemicals Manufacturing Source Category in Support of the Risk 
and Technology Review 2020 Proposed Rule, which is available in the 
docket for this rulemaking.

I. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

J. National Technology Transfer and Advancement Act (NTTAA)

    This action involves technical standards. Therefore, the EPA 
conducted a search to identify potentially applicable voluntary 
consensus standards. However, the Agency identified no such standards. 
A thorough summary of the search and results are included in the 
memorandum titled Voluntary Consensus Standard Results for Cyanide 
Chemicals Manufacturing Residual Risk and Technology Review, which is 
available in the docket for this action.

K. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    The EPA believes that this action does not have disproportionately 
high and adverse human health or environmental effects on minority 
populations, low-income populations, and/or indigenous peoples, as 
specified in Executive Order 12898 (59 FR 7629, February 16, 1994).
    The documentation for this decision is contained in section IV.B of 
this preamble and in the technical report, Risk and Technology Review--
Analysis of Demographic Factors for Populations Living Near Cyanide 
Chemicals Manufacturing Facilities, available in the docket for this 
action.

List of Subjects in 40 CFR Part 63

    Environmental protection, Air pollution control, Hazardous 
substances, Reporting and recordkeeping requirements.

Andrew Wheeler,
Administrator.
[FR Doc. 2021-00374 Filed 1-14-21; 8:45 am]
BILLING CODE 6560-50-P


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