[Federal Register Volume 82, Number 182 (Thursday, September 21, 2017)]
[Proposed Rules]
[Pages 44254-44285]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-19448]



[[Page 44253]]

Vol. 82

Thursday,

No. 182

September 21, 2017

Part II





Environmental Protection Agency





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





40 CFR Part 63





 National Emission Standards for Hazardous Air Pollutants From the 
Portland Cement Manufacturing Industry Residual Risk and Technology 
Review; Proposed Rule

Federal Register / Vol. 82 , No. 182 / Thursday, September 21, 2017 / 
Proposed Rules

[[Page 44254]]


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

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2016-0442; FRL-9967-61-OAR]
RIN 2060-AS92


National Emission Standards for Hazardous Air Pollutants From the 
Portland Cement Manufacturing Industry Residual Risk and Technology 
Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: The Environmental Protection Agency (EPA) is proposing 
amendments to the National Emission Standards for Hazardous Air 
Pollutants (NESHAP) From the Portland Cement Manufacturing Industry to 
address the results of the residual risk and technology review (RTR) 
the EPA is required to conduct in accordance with section 112 of the 
Clean Air Act (CAA). We found risks due to emissions of air toxics to 
be acceptable from this source category with an ample margin of safety, 
and we identified no new cost-effective controls under the technology 
review to achieve further emissions reductions. Therefore, we are 
proposing no revisions to the numerical emission limits based on these 
analyses. However, the EPA is proposing amendments to correct and 
clarify rule requirements and provisions. While the proposed amendments 
would not result in reductions in emissions of hazardous air pollutants 
(HAP), this action, if finalized, would result in improved monitoring, 
compliance, and implementation of the rule.

DATES: 
    Comments. Comments must be received on or before November 6, 2017.
    Public Hearing. If a public hearing is requested by September 26, 
2017, the EPA will hold a public hearing on October 6, 2017. The last 
day to pre-register in advance to speak at the public hearing will be 
October 4, 2017.

ADDRESSES: Comments. Submit your comments, identified by Docket ID No. 
EPA-HQ-OAR-2016-0442, at http://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. The EPA may publish any 
comment received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
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 http://www2.epa.gov/dockets/commenting-epa-dockets.
    Public Hearing. If a hearing is requested, it will be held at the 
EPA WJC East Building, 1201 Constitution Avenue NW., Washington, DC 
20004. If a public hearing is requested, then we will provide details 
about the public hearing on our Web site at https://www.epa.gov/stationary-sources-air-pollution/portland-cement-manufacturing-industry-national-emission-standards. The EPA does not intend to 
publish any future notices in the Federal Register announcing any 
updates on the request for public hearing. Please contact Aimee St. 
Clair at (919) 541-1063 or by email at <a href="/cdn-cgi/l/email-protection#572423343b363e2579363e3a32321732273679303821"><span class="__cf_email__" data-cfemail="7b080f18171a1209551a12161e1e3b1e0b1a551c140d">[email protected]</span></a> to request 
a public hearing, to register to speak at the public hearing, or to 
inquire as to whether a public hearing will be held.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Mr. Brian Storey, Sector Policies and Programs Division 
(D243-04), Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711; telephone number: (919) 541-1103; fax number: (919) 541-5450; 
and email address: <a href="/cdn-cgi/l/email-protection#3744435845524e1955455e56597752475619505841"><span class="__cf_email__" data-cfemail="7b080f14091e02551909121a153b1e0b1a551c140d">[email protected]</span></a>. For specific information 
regarding the risk modeling methodology, contact Mr. 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#c6aeafb4b2bce8aca7aba3b586a3b6a7e8a1a9b0"><span class="__cf_email__" data-cfemail="5f37362d2b2571353e323a2c1f3a2f3e71383029">[email protected]</span></a>. For information about the applicability of the 
NESHAP to a particular entity, contact Ms. Sara Ayres, Office of 
Enforcement and Compliance Assurance, U.S. Environmental Protection 
Agency, U.S. EPA Region 5 (E-19J), 77 West Jackson Boulevard, Chicago, 
IL 60604; telephone number: (312) 353-6266; email address: 
<a href="/cdn-cgi/l/email-protection#3f5e464d5a4c114c5e4d5e7f5a4f5e11585049"><span class="__cf_email__" data-cfemail="6100181304124f12001300210411004f060e17">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION:
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2016-0442. All documents in the docket are 
listed in the Regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, is not placed on the Internet and will be 
publicly available only in hard copy. Publicly available docket 
materials are available either electronically in Regulations.gov or in 
hard copy at the EPA Docket Center, Room 3334, EPA WJC West Building, 
1301 Constitution Avenue NW., Washington, DC. The Public Reading Room 
is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding 
legal holidays. The telephone number for the Public Reading Room is 
(202) 566-1744, and the telephone number for the EPA Docket Center is 
(202) 566-1742.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2016-0442. 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 http://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 information that you consider to be CBI or 
otherwise protected through http://www.regulations.gov or email. The 
http://www.regulations.gov Web site is an ``anonymous access'' system, 
which means the EPA will not know your identity or contact information 
unless you provide it in the body of your comment. If you send an email 
comment directly to the EPA without going through http://www.regulations.gov, your email address will be automatically captured 
and included as part of the comment that is placed in the public docket 
and made available on the Internet. If you submit an electronic 
comment, the EPA recommends that you include your name and other 
contact information in the body of your comment and with any disk or 
CD-ROM you submit. If the EPA cannot read your comment due to technical 
difficulties and cannot contact you for clarification, the EPA may not 
be able to consider your comment. Electronic files should not include 
special characters or any form of encryption and be free of any defects 
or

[[Page 44255]]

viruses. For additional information about the EPA's public docket, 
visit the EPA Docket Center homepage at http://www.epa.gov/dockets.
    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 reference purposes, the EPA 
defines the following terms and acronyms here:

ACI activated carbon injection
AEGL acute exposure guideline levels
AERMOD air dispersion model used by the HEM-3 model
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting Interface
CFR Code of Federal Regulations
CISWI commercial and industrial solid waste incinerators
CO carbon monoxide
D/F dioxins and furans
EPA Environmental Protection Agency
ERP Emergency Response Planning
ERPG Emergency Response Planning Guidelines
ERT Electronic Reporting Tool
ESP electrostatic precipitators
FR Federal Register
GHGRP Greenhouse Gas Reporting Program
HAP hazardous air pollutants
HCl hydrochloric acid
HEM-3 Human Exposure Model
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
IRIS Integrated Risk Information System
km kilometer
lb/hr pounds per hour
lb/ton pounds per ton
LOAEL lowest-observed-adverse-effect level
MACT maximum achievable control technology
mg/kg-day milligrams per kilogram per day
mg/m\3\ milligrams per cubic meter
mg/Nm\3\ milligrams per normal cubic meter
MIR maximum individual risk
NAAQS National Ambient Air Quality Standards
NAC National Advisory Committee
NAICS North American Industry Classification System
NAS National Academy of Sciences
NATA National Air Toxics Assessment
NEI National Emissions Inventory
NESHAP national emission standards for hazardous air pollutants
NO<INF>X</INF> nitrogen oxides
NOAA National Oceanic and Atmospheric Administration
NOAEL no-observed-adverse-effect level
NRC National Research Council
NRDC Natural Resources Defense Council
NSPS new source performance standards
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PCA Portland Cement Association
PEL probable effect level
PM particulate matter
POM polycyclic organic matter
ppm parts per million
ppmvd parts per million by volume, dry basis
PRA Paperwork Reduction Act
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTO regenerative thermal oxidizers
RTR residual risk and technology review
SAB Science Advisory Board
SCR selective catalytic reduction
SO<INF>2</INF> sulfur dioxide
TEF toxicity equivalence factors
TEQ toxic equivalents
THC total hydrocarbons
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and 
Ecological Exposure model
UF uncertainty factor
[micro]g/m\3\ microgram per cubic meter
UISIS Universal Industrial Sectors Integrated Solutions
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
U.S.C. United States Code
WebFIRE Web Factor Information Retrieval System

    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?
    C. What should I consider as I prepare my comments for the EPA?
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
    A. How did we estimate post-MACT risks posed by the source 
category?
    B. How did we consider the risk results in making decisions for 
this proposal?
    C. How did we perform the technology review?
IV. Analytical Results and Proposed Decisions
    A. What are the results of the risk assessment and analyses?
    B. What are our proposed decisions regarding risk acceptability, 
ample margin of safety, and adverse environmental effects?
    C. What are the results and proposed decisions based on our 
technology review?
    D. What other actions are we proposing?
    E. What compliance dates are we proposing?
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the impacts to 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?

    Table 1 of this preamble lists the NESHAP and associated regulated 
industrial source category that is the subject of this proposal. Table 
1 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), the Portland Cement Manufacturing Industry source 
category is any facility engaged in manufacturing Portland cement by 
either the wet or dry process. The category includes, but is not 
limited to, the following process units: Kiln, clinker cooler, raw mill 
system, finish mill system, raw mill dryer, raw material storage, 
clinker storage, finished product storage, conveyor transfer points, 
bagging, and bulk loading and unloading systems.

[[Page 44256]]



    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
------------------------------------------------------------------------
       Source category                 NESHAP           NAICS code \1\
------------------------------------------------------------------------
Portland cement manufacturing  40 CFR part 63                    327310
 facilities.                    subpart LLL.
------------------------------------------------------------------------
\1\ North American Industry Classification System.

The source category does not include those kilns that burn hazardous 
waste and are subject to and regulated under 40 CFR part 63, subpart 
EEE, or kilns that burn solid waste and are subject to the Commercial 
and Industrial Solid Waste Incinerator (CISWI) rule under 40 CFR part 
60, subparts CCCC and DDDD.

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://www3.epa.gov/airquality/cement/actions.html. Following 
publication in the Federal Register, the EPA will post the Federal 
Register version of the proposal and key technical documents at this 
same Web site. Information on the overall RTR program is available at 
https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.

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

    Submitting CBI. Do not submit information containing CBI to the EPA 
through http://www.regulations.gov or email. Clearly mark the part or 
all of the information that you claim to be CBI. For CBI information on 
a disk or CD-ROM that you mail to the EPA, mark the outside of the disk 
or CD-ROM as CBI and then identify electronically within the disk or 
CD-ROM the specific information that is claimed as CBI. In addition to 
one complete version of the comments that includes information claimed 
as CBI, you must submit a copy of the comments that does not contain 
the information claimed as CBI for inclusion in the public docket. If 
you submit a CD-ROM or disk that does not contain CBI, mark the outside 
of the disk or CD-ROM clearly that it does not contain CBI. Information 
not marked as CBI will be included in the public docket and the EPA's 
electronic public docket without prior notice. Information marked as 
CBI will not be disclosed except in accordance with procedures set 
forth in 40 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-2016-0442.

II. Background

A. What is the statutory authority for this action?

    Section 112 of the CAA establishes a two-stage regulatory process 
to address emissions of HAP from stationary sources. In the first 
stage, after the EPA has identified categories of sources emitting one 
or more of the HAP listed in CAA section 112(b), CAA section 112(d) 
requires us to promulgate technology-based NESHAP for those sources. 
``Major sources'' are those that emit or have the potential to emit 10 
tons per year (tpy) or more of a single HAP or 25 tpy or more of any 
combination of HAP. For major sources, 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) and are commonly referred to as 
maximum achievable control technology (MACT) standards.
    MACT standards must reflect the maximum degree of emissions 
reduction achievable through the application of measures, processes, 
methods, systems, or techniques, including, but not limited to, 
measures that: (1) Reduce the volume of or eliminate pollutants through 
process changes, substitution of materials, or other modifications; (2) 
enclose systems or processes to eliminate emissions; (3) capture or 
treat pollutants when released from a process, stack, storage, or 
fugitive emissions point; (4) are design, equipment, work practice, or 
operational standards (including requirements for operator training or 
certification); or (5) are a combination of the above. CAA section 
112(d)(2)(A)-(E). The MACT standards may take the form of design, 
equipment, work practice, or operational standards where the EPA first 
determines either that: (1) A pollutant cannot be emitted through a 
conveyance designed and constructed to emit or capture the pollutant, 
or that any requirement for, or use of, such a conveyance would be 
inconsistent with law; or (2) the application of measurement 
methodology to a particular class of sources is not practicable due to 
technological and economic limitations. CAA section 112(h)(1)-(2).
    The MACT ``floor'' is the minimum control level allowed for MACT 
standards promulgated under CAA section 112(d)(3) and may not be based 
on cost considerations. For new sources, the MACT floor cannot be less 
stringent than the emissions control that is achieved in practice by 
the best-controlled similar source. The MACT floor for existing sources 
can be less stringent than floors for new sources, but not less 
stringent than the average emissions limitation achieved by the best-
performing 12 percent of existing sources in the category or 
subcategory (or the best-performing five sources for categories or 
subcategories with fewer than 30 sources). In developing MACT 
standards, the EPA must also consider control options that are more 
stringent than the floor. We may establish standards more stringent 
than the floor based on considerations of the cost of achieving the 
emission reductions, any non-air quality health and environmental 
impacts, and energy requirements.
    The EPA is then required to review these technology-based standards 
and revise them ``as necessary (taking into account developments in 
practices, processes, and control technologies)'' no less frequently 
than every 8 years. CAA section 112(d)(6). In conducting this 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 second stage in standard-setting focuses on reducing any 
remaining (i.e., ``residual'') risk according to CAA section 112(f). 
Section 112(f)(1) of the CAA required that the EPA prepare a report to 
Congress discussing (among other things) methods of calculating the 
risks posed (or potentially posed) by sources after implementation of 
the MACT standards, the public health significance of those risks, and 
the EPA's recommendations as to legislation regarding such remaining 
risk. The EPA prepared and submitted the Residual Risk Report to 
Congress, EPA-453/R-99-001 (Risk Report) in March 1999.

[[Page 44257]]

Section 112(f)(2) of the CAA then provides that if Congress does not 
act on any recommendation in the Risk Report, the EPA must analyze and 
address residual risk for each category or subcategory of sources 8 
years after promulgation of such standards pursuant to CAA section 
112(d).
    Section 112(f)(2) of the CAA requires the EPA to determine for 
source categories subject to MACT standards whether promulgation of 
additional standards is needed to provide an ample margin of safety to 
protect public health. Section 112(f)(2)(B) of the CAA expressly 
preserves the EPA's use of the two-step process 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 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 in a challenge to the 
risk review for the Synthetic Organic Chemical Manufacturing source 
category, the United States Court of Appeals for the District of 
Columbia Circuit (the Court) upheld as reasonable 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) (``[S]ubsection 112(f)(2)(B) expressly incorporates 
the EPA's interpretation of the Clean Air Act from the Benzene 
standard, complete with a citation to the Federal Register.''); see 
also, A Legislative History of the Clean Air Act Amendments of 1990, 
vol. 1, p. 877 (Senate debate on Conference Report).
    The first step in the process of evaluating residual risk is the 
determination of acceptable risk. If risks are unacceptable, the EPA 
cannot consider cost in identifying the emissions standards necessary 
to bring risks to an acceptable level. The second step is the 
determination of whether standards must be further revised in order to 
provide an ample margin of safety to protect public health. The ample 
margin of safety is the level at which the standards must be set, 
unless an even more stringent standard is necessary to prevent, taking 
into consideration costs, energy, safety, and other relevant factors, 
an adverse environmental effect.
1. Step 1--Determination of Acceptability
    The Agency in the Benzene NESHAP concluded that ``the acceptability 
of risk under section 112 is best judged on the basis of a broad set of 
health risk measures and information'' and that the ``judgment on 
acceptability cannot be reduced to any single factor.'' Benzene NESHAP 
at 38046. The determination of what represents an ``acceptable'' risk 
is based on a judgment of ``what risks are acceptable in the world in 
which we live'' (Risk Report at 178, quoting NRDC v. EPA, 824 F. 2d 
1146, 1165 (D.C. Cir. 1987) (en banc) (``Vinyl Chloride''), recognizing 
that our world is not risk-free.
    In the Benzene NESHAP, we stated that ``EPA will generally presume 
that if the risk to [the maximum exposed] individual is no higher than 
approximately one in 10 thousand, that risk level is considered 
acceptable.'' 54 FR at 38045, September 14, 1989. We discussed the 
maximum individual lifetime cancer risk (or maximum individual risk 
(MIR)) as being ``the estimated risk that a person living near a plant 
would have if he or she were exposed to the maximum pollutant 
concentrations for 70 years.'' Id. We explained that this measure of 
risk ``is an estimate of the upper bound of risk based on conservative 
assumptions, such as continuous exposure for 24 hours per day for 70 
years.'' Id. We acknowledged that maximum individual lifetime cancer 
risk ``does not necessarily reflect the true risk, but displays a 
conservative risk level which is an upper-bound that is unlikely to be 
exceeded.'' Id.
    Understanding that there are both benefits and limitations to using 
the MIR as a metric for determining acceptability, we acknowledged in 
the Benzene NESHAP that ``consideration of maximum individual risk * * 
* must take into account the strengths and weaknesses of this measure 
of risk.'' Id. Consequently, the presumptive risk level of 100-in-1 
million (1-in-10 thousand) provides a benchmark for judging the 
acceptability of maximum individual lifetime cancer risk, but does not 
constitute a rigid line for making that determination. Further, in the 
Benzene NESHAP, we noted that:

[p]articular attention will also be accorded to the weight of 
evidence presented in the risk assessment of potential 
carcinogenicity or other health effects of a pollutant. While the 
same numerical risk may be estimated for an exposure to a pollutant 
judged to be a known human carcinogen, and to a pollutant considered 
a possible human carcinogen based on limited animal test data, the 
same weight cannot be accorded to both estimates. In considering the 
potential public health effects of the two pollutants, the Agency's 
judgment on acceptability, including the MIR, will be influenced by 
the greater weight of evidence for the known human carcinogen.

Id. at 38046. The Agency also explained in the Benzene NESHAP that:

[i]n establishing a presumption for MIR, rather than a rigid line 
for acceptability, the Agency intends to weigh it with a series of 
other health measures and factors. These include the overall 
incidence of cancer or other serious health effects within the 
exposed population, the numbers of persons exposed within each 
individual lifetime risk range and associated incidence within, 
typically, a 50 km exposure radius around facilities, the science 
policy assumptions and estimation uncertainties associated with the 
risk measures, weight of the scientific evidence for human health 
effects, other quantified or unquantified health effects, effects 
due to co-location of facilities, and co-emission of pollutants.

Id. at 38045. In some cases, these health measures and factors taken 
together may provide a more realistic description of the magnitude of 
risk in the exposed population than that provided by maximum individual 
lifetime cancer risk alone.
    As noted earlier, in NRDC v. EPA, the Court held that CAA section 
112(f)(2) ``incorporates the EPA's interpretation of the Clean Air Act 
from the Benzene Standard.'' The Court further held that Congress' 
incorporation of the Benzene standard applies equally to carcinogens 
and non-carcinogens. 529 F.3d at 1081-82. Accordingly, we also consider 
non-cancer risk metrics in our determination of risk acceptability and 
ample margin of safety.
2. Step 2--Determination of Ample Margin of Safety
    Section 112(f)(2) of the CAA requires the EPA to determine, for 
source categories subject to MACT standards, whether those standards 
provide an ample margin of safety to protect public health. As 
explained in the Benzene NESHAP, ``the second step of the inquiry, 
determining an `ample margin of safety,' again includes consideration 
of all of the health factors, and whether to reduce the risks even 
further * * *. Beyond that information, additional factors relating to 
the appropriate level of control will also be considered, including 
costs and economic impacts of controls, technological feasibility, 
uncertainties, and any other relevant factors. Considering all of these 
factors, the agency will establish the standard at

[[Page 44258]]

a level that provides an ample margin of safety to protect the public 
health, as required by section 112.'' 54 FR 38046, September 14, 1989.
    According to CAA section 112(f)(2)(A), if the MACT standards for 
HAP ``classified as a known, probable, or possible human carcinogen do 
not reduce lifetime excess cancer risks to the individual most exposed 
to emissions from a source in the category or subcategory to less than 
one in one million,'' the EPA must promulgate residual risk standards 
for the source category (or subcategory), as necessary to provide an 
ample margin of safety to protect public health. In doing so, the EPA 
may adopt standards equal to existing MACT standards if the EPA 
determines that the existing standards (i.e., the MACT standards) are 
sufficiently protective. NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 
2008) (``If EPA determines that the existing technology-based standards 
provide an 'ample margin of safety,' then the Agency is free to readopt 
those standards during the residual risk rulemaking.'') The EPA must 
also adopt more stringent standards, if necessary, to prevent an 
adverse environmental effect,\1\ but must consider cost, energy, 
safety, and other relevant factors in doing so.
---------------------------------------------------------------------------

    \1\ ``Adverse environmental effect'' is defined as any 
significant and widespread adverse effect, which may be reasonably 
anticipated to wildlife, aquatic life, or natural resources, 
including adverse impacts on populations of endangered or threatened 
species or significant degradation of environmental qualities over 
broad areas. CAA section 112(a)(7).
---------------------------------------------------------------------------

    The CAA does not specifically define the terms ``individual most 
exposed,'' ``acceptable level,'' and ``ample margin of safety.'' In the 
Benzene NESHAP, 54 FR at 38044-38045, September 14, 1989, we stated as 
an overall objective:

    In protecting public health with an ample margin of safety under 
section 112, EPA strives to provide maximum feasible protection 
against risks to health from hazardous air pollutants by (1) 
protecting the greatest number of persons possible to an individual 
lifetime risk level no higher than approximately 1-in-1 million and 
(2) limiting to no higher than approximately 1-in-10 thousand [i.e., 
100-in-1 million] the estimated risk that a person living near a 
plant would have if he or she were exposed to the maximum pollutant 
concentrations for 70 years.

The Agency further stated that ``[t]he EPA also considers incidence 
(the number of persons estimated to suffer cancer or other serious 
health effects as a result of exposure to a pollutant) to be an 
important measure of the health risk to the exposed population. 
Incidence measures the extent of health risks to the exposed population 
as a whole, by providing an estimate of the occurrence of cancer or 
other serious health effects in the exposed population.'' Id. at 38045.
    In the ample margin of safety decision process, the Agency again 
considers all of the health risks and other health information 
considered in the first step, including the incremental risk reduction 
associated with standards more stringent than the MACT standard or a 
more stringent standard that the EPA has determined is necessary to 
ensure risk is acceptable. In the ample margin of safety analysis, the 
Agency considers additional factors, including costs and economic 
impacts of controls, technological feasibility, uncertainties, and any 
other relevant factors. Considering all of these factors, the Agency 
will establish the standard at a level that provides an ample margin of 
safety to protect the public health, as required by CAA section 112(f). 
54 FR 38046, September 14, 1989.

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

    The EPA initially promulgated the Portland Cement Manufacturing 
Industry NESHAP on June 14, 1999 (64 FR 31898), under title 40, part 
63, subpart LLL of the CFR (40 CFR part 63, subpart LLL). The rule was 
amended on April 5, 2002 (67 FR 16614); July 5, 2002 (67 FR 44766); 
December 6, 2002 (67 FR 72580); December 20, 2006 (71 FR 76518); 
September 9, 2010 (75 FR 54970); January 18, 2011 (76 FR 2832); 
February 12, 2013 (78 FR 10006); July 27, 2015 (80 FR 44772); September 
11, 2015 (80 FR 54728); and July 25, 2016 (81 FR 48356). The amendments 
further defined affected cement kilns as those used to manufacture 
Portland cement, except for kilns that burn hazardous waste, and are 
subject to and regulated under 40 CFR part 63, subpart EEE, and kilns 
that burn solid waste, which are subject to the CISWI rule under 40 CFR 
part 60, subparts CCCC and DDDD. Additionally, onsite sources that are 
subject to standards for nonmetallic mineral processing plants in 40 
CFR part 60, subpart OOO are not subject to 40 CFR part 63, subpart 
LLL. Crushers are not covered by 40 CFR part 63, subpart LLL regardless 
of their location. Subpart LLL NESHAP regulates HAP emissions from new 
and existing Portland cement production facilities that are major or 
area sources of HAP, with one exception. Kilns located at facilities 
that are area sources, are not regulated for hydrochloric acid (HCl) 
emissions.
    Portland cement manufacturing is an energy-intensive process in 
which cement is made by grinding and heating a mixture of raw materials 
such as limestone, clay, sand, and iron ore in a rotary kiln. The kiln 
is a large furnace that is fueled by coal, oil, gas, coke, and/or 
various waste materials. The product (known as clinker) from the kiln 
is cooled, ground, and then mixed with a small amount of gypsum to 
produce Portland cement.
    The main source of air toxics emissions from a Portland cement 
plant is the kiln. Emissions originate from the burning of fuels and 
heating of feed materials. Air toxics are also emitted from the 
grinding, cooling, and materials handling steps in the manufacturing 
process. Pollutants regulated under the subpart LLL NESHAP are 
particulate matter (PM) as a surrogate for non-mercury HAP metals, 
total hydrocarbons (THC) as a surrogate for organic HAP other than 
dioxins and furans (D/F), organic HAP as an alternative to the limit 
for THC, mercury, HCl (from major sources only), and D/F expressed as 
toxic equivalents (TEQ). The kiln is regulated for all HAP and raw 
material dryers are regulated for THC or the alternative organic HAP. 
Clinker coolers are regulated for PM. Finish mills and raw mills are 
regulated for opacity. During periods of startup and shutdown, the 
kiln, clinker cooler, and raw material dryer are regulated by work 
practices. Open clinker storage piles are regulated by work practices. 
The emission standards for the affected sources are summarized in Table 
2.

         Table 2--Emission Limits for Kilns, Clinker Coolers, Raw Material Dryers, Raw and Finish Mills
----------------------------------------------------------------------------------------------------------------
                                                                                   And the units
                                   And the         And it is      Your emissions       of the        The oxygen
  If your source is a (an):     operating mode   located at a:     limits are:    emissions limit    correction
                                     is:                                                are:         factor is:
----------------------------------------------------------------------------------------------------------------
1. Existing kiln.............  Normal           Major or area    PM \1\ 0.07....  Pounds (lb)/ton  NA.
                                operation.       source.                           clinker.

[[Page 44259]]

 
                                                                 D/F \2\ 0.2....  Nanograms/dry    7 percent.
                                                                                   standard cubic
                                                                                   meters (ng/
                                                                                   dscm) (TEQ).
                                                                 Mercury 55.....  lb/million (MM)  NA.
                                                                                   tons clinker.
                                                                 THC \3\ \4\ 24.  Parts per        7 percent.
                                                                                   million,
                                                                                   volumetric dry
                                                                                   (ppmvd).
2. Existing kiln.............  Normal           Major source...  HCl 3..........  ppmvd..........  7 percent.
                                operation.
3. Existing kiln.............  Startup and      Major or area    Work practices.  NA.............  NA.
                                shutdown.        source.         (63.1346(g))...
4. New kiln..................  Normal           Major or area    PM \1\ 0.02....  lb/ton clinker.  NA.
                                operation.       source.
                                                                 D/F \2\ 0.2....  ng/dscm (TEQ)..  7 percent.
                                                                 Mercury 21.....  lb/MM tons       NA.
                                                                                   clinker.
                                                                 THC \3\ \4\ 24.  ppmvd..........  7 percent.
5. New kiln..................  Normal           Major source...  HCl 3..........  ppmvd..........  7 percent.
                                operation.
6. New kiln..................  Startup and      Major or area    Work practices.  NA.............  NA.
                                shutdown.        source.         (63.1346(g))...
7. Existing clinker cooler...  Normal           Major or area    PM 0.07........  lb/ton clinker.  NA.
                                operation.       source.
8. Existing clinker cooler...  Startup and      Major or area    Work practices   NA.............  NA.
                                shutdown.        source.          (63.1348(b)(9)
                                                                  ).
9. New clinker cooler........  Normal           Major or area    PM 0.02........  lb/ton clinker.  NA.
                                operation.       source.
10. New clinker cooler.......  Startup and      Major or area    Work practices   NA.............  NA.
                                shutdown.        source.          (63.1348(b)(9)
                                                                  ).
11. Existing or new raw        Normal           Major or area    THC \3\ \4\ 24.  ppmvd..........  NA.
 material dryer.                operation.       source.
12. Existing or new raw        Startup and      Major or area    Work practices   NA.............  NA.
 material dryer.                shutdown.        source.          (63.1348(b)(9)
                                                                  ).
13. Existing or new raw or     All operating    Major source...  Opacity 10.....  percent........  NA.
 finish mill.                   modes.
----------------------------------------------------------------------------------------------------------------
\1\ The initial and subsequent PM performance tests are performed using Method 5 or 5I and consist of three test
  runs.
\2\ If the average temperature at the inlet to the first PM control device (fabric filter or electrostatic
  precipitator) during the D/F performance test is 400 [deg]F or less, this limit is changed to 0.40 ng/dscm
  (TEQ).
\3\ Measured as propane.
\4\ Any source subject to the 24 ppmvd THC limit may elect to meet an alternative limit of 12 ppmvd for total
  organic HAP.

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

    For the Portland Cement Manufacturing Industry source category, we 
did not submit data collection requests to the industry or request 
emissions testing by the industry for the information used in this 
analysis. The data and data sources used to support this action are 
described in section II.D below.

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

    For the Portland Cement Manufacturing Industry source category, a 
comprehensive list of facilities and kilns was compiled using 
information from the EPA's Greenhouse Gas Reporting Program (GHGRP) 
(https://www.epa.gov/ghgreporting). All manufacturers of Portland 
cement are required to report annually their greenhouse gas emissions 
to the EPA (40 CFR part 98, subpart H). In reporting year 2015, 95 
Portland cement facilities reported under the GHGRP. As explained above 
in section II.B, kilns that are fueled by hazardous waste are subject 
to the hazardous waste regulations in 40 CFR part 63, subpart EEE and, 
therefore, are not subject to 40 CFR part 63, subpart LLL. Kilns that 
are fueled by solid waste are subject to regulations in 40 CFR part 60, 
subpart CCCC or DDDD and are also not subject to subpart LLL. To assist 
in the identification of which sources are subject to subpart LLL, the 
comprehensive list of Portland cement manufacturing facilities was 
submitted to the Portland Cement Association (PCA) for review. The PCA 
is an organization that represents the manufacturers of cement. The PCA 
provided information on the status of each kiln and clinker cooler, 
whether or not they were subject to subpart LLL regulations, and 
identified other sources at facilities, such as raw material dryers, 
that were also subject to subpart LLL.
    The risk modeling dataset was developed in a two-step process. 
Initially, a draft dataset was developed using available information on 
emissions, stack parameters, and emission source locations. In step 
two, the draft dataset for each Portland cement manufacturing facility 
was submitted to the facility or its parent company to review for 
accuracy. Based on the review by each company and the submittal of 
documentation supporting the changes, the risk modeling dataset was 
revised. Copies of the datasets sent to the companies for review and 
the revised datasets and supporting documentation submitted by each 
company are contained in the docket to this rulemaking (Docket ID No. 
EPA-HQ-OAR-2016-0442).
    The initial draft dataset was developed using emission test data to 
the extent possible. Under 40 CFR part 63, subpart LLL, the EPA 
requires that performance test results be submitted to the EPA via the 
Compliance and Emissions Data Reporting Interface (CEDRI), which can be 
accessed through the EPA's Central Data Exchange (CDX). Emissions data 
are publicly available through the EPA's Web Factor Information 
Retrieval System (WebFIRE) using the EPA's electronic reporting tool 
(ERT) as listed on the EPA's ERT Web site (https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert). To 
estimate actual emissions, available emissions data were extracted from 
each facility's submitted ERT file. When emissions data were not 
available in ERT, the subpart LLL emissions limit was substituted as a 
placeholder for actual emissions until the data set could be reviewed 
and revised by industry.

III. Analytical Procedures

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

[[Page 44260]]

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

    The EPA conducted a risk assessment that provides estimates of the 
MIR posed by the HAP emissions from each source in the source category, 
the hazard index (HI) for chronic exposures to HAP with the potential 
to cause non-cancer health effects, and the hazard quotient (HQ) for 
acute exposures to HAP with the potential to cause non-cancer health 
effects. The assessment also provides estimates of the distribution of 
cancer risks within the exposed populations, cancer incidence, and an 
evaluation of the potential for adverse environmental effects. The 
eight 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 Portland Cement Manufacturing Industry Source 
Category in Support of the Risk and Technology Review September, 2017 
Proposed Rule. The methods used to assess risks (as described in the 
eight primary steps below) are consistent with those peer-reviewed by a 
panel of the EPA's Science Advisory Board (SAB) in 2009 and described 
in their peer review report issued in 2010;\2\ they are also consistent 
with the key recommendations contained in that report.
---------------------------------------------------------------------------

    \2\ U.S. EPA SAB. 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, May 2010.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    The pollutants regulated under 40 CFR part 63, subpart LLL are PM, 
HCl, THC, mercury, and D/F. The emission standards apply to Portland 
cement plants that are major or area sources, with one exception. Kilns 
that are located at a facility that is an area source are not subject 
to the emission limits for HCl. Sources subject to the emissions limit 
for THC may elect to meet an alternative limit for total organic HAP. 
For purposes of subpart LLL, total organic HAP is the sum of the 
concentrations of compounds of formaldehyde, benzene, toluene, styrene, 
m-xylene, p-xylene, o-xylene, acetaldehyde, and naphthalene as measured 
by EPA Test Method 320 or Method 18 of appendix A to 40 CFR part 63 or 
ASTM D6348-03 or a combination of these methods, as appropriate. The 
affected sources at Portland cement plants that were accounted for in 
the risk modeling dataset include the kiln, as well as any alkali 
bypass or inline raw mill or inline coal mill, clinker coolers, and raw 
material dryers. Kilns fueled with hazardous waste or solid waste and 
not subject to subpart LLL were excluded from the dataset. All affected 
sources in the risk modeling dataset emit through stacks. As mentioned 
in section II.D above, the risk modeling dataset used for estimating 
actual emissions was developed in a two-step process. Initially, the 
dataset was developed using available information and is described 
below. The dataset for each Portland cement manufacturing facility was 
then submitted to the facility, or its parent company, to review for 
accuracy. Based on the review by each company, and the submittal of 
documentation supporting the changes, the risk modeling dataset was 
then revised. Copies of the datasets sent to the companies for review 
and the revised datasets submitted by each company are contained in the 
docket to this rulemaking (Docket ID No. EPA-HQ-OAR-2016-0442).
    As described in section II.D above, available emissions data were 
extracted from each facility's submitted ERT file. To ensure that the 
emissions data reflect process and control device changes made at each 
Portland cement plant to comply with the 2013 final amendments to 40 
CFR part 63, subpart LLL (February 12, 2013, 78 FR 10006), emissions 
data from mid-2015 and later were used as inputs into the emissions 
modeling file.
    Emissions data are reported in ERT in units of pounds per hour (lb/
hr), which were multiplied by a facility's reported annual hours of 
operation to calculate emissions in tpy. If hours of operation were not 
reported, the default of 8,760 hours per year was used. When emissions 
data were not available in ERT, the 40 CFR part 63, subpart LLL 
emissions limit was substituted as a placeholder for actual emissions 
until the data set could be reviewed and revised by industry.
    Subpart LLL of 40 CFR part 63 uses PM as a surrogate for non-
mercury metallic HAP and THC as a surrogate for organic HAP. The 
specific non-mercury metallic HAP that went into the modeling file are 
antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, 
manganese, mercury, nickel, and selenium. As an alternative to 
measuring THC, subpart LLL allows sources to measure directly their 
emissions of the nine organic HAP listed in subpart LLL. The specific 
organic HAP that went into the modeling file are acetaldehyde, 
formaldehyde, naphthalene, styrene, toluene, m-xylene, o-xylene, p-
xylene, and benzene. Because subpart LLL compliance testing is 
typically performed for the surrogates PM and THC, there are limited 
test data available for compound-specific non-mercury metallic and 
organic HAP emissions. To generate compound-specific metallic HAP and 
organic HAP emissions estimates, recent emissions tests were identified 
in which testing was done for compound-specific metallic and organic 
HAP emissions. To account for recent changes in emission controls and 
production processes that have been implemented by facilities to comply 
with the subpart LLL MACT standards, emissions testing that occurred in 
2015 and later were used to develop compound-specific estimates for 
metallic HAP and organic HAP emissions. In the case of D/F, the subpart 
LLL emission limits for D/F were unchanged in the 2013 final rule. 
Thus, older D/F test data could be used along with more recent test 
data.
    The approach used to develop the final risk modeling dataset 
assures the quality of the data at various steps in the process of 
developing the dataset. The initial step in developing the dataset was 
to compile a list of affected facilities. A comprehensive list of 
cement manufacturing facilities and kilns was derived from the EPA's 
GHGRP, which requires reporting by all cement manufacturing facilities. 
Not all Portland cement kilns are subject to 40 CFR part 63, subpart 
LLL. Kilns that burn commercial and industrial solid waste are subject 
to 40 CFR part 60, subpart CCCC and DDDD. Kilns that burn hazardous 
waste are subject to 40 CFR part 63, subpart EEE. To help identify the 
cement kilns that are subject to subpart LLL regulations, the list of 
facilities and kilns was submitted to the PCA for review. In their 
review, they provided useful information on which cement manufacturing 
facilities were or were not subject to subpart LLL, whether kilns and 
clinker coolers used separate or combined stacks, the presence of 
additional affected sources not on the initial list, and the presence 
of kilns that were not currently operating. For those kilns identified 
as not currently operating, the appropriate state permitting agency was 
contacted to determine whether the kiln was currently permitted to 
operate. If the kiln was not operating, but retained their title V 
permit, they were kept in the dataset. In other instances, company 
representatives were contacted to verify that kilns at their facilities 
were or were

[[Page 44261]]

not subject to subpart LLL regulations. In developing the emissions 
data, operating hours, stack parameters (i.e., stack height, 
temperature, diameter, velocity, and flowrate), and stack locations 
(i.e., latitude and longitude), the use of the EPA's ERT provides a 
single source of electronic test data and replaces the manual 
collection and evaluation of test data. The regulated facility owner or 
operator submits their summary report semiannually to the EPA via the 
CEDRI, which is accessed through the EPA's CDX (www.epa.gov/cdx). This 
electronic submission of data helps to ensure that information and 
procedures required by test methods are documented, provides consistent 
criteria to quantitatively characterize the quality of the data 
collected during the emissions test, and standardizes the reporting of 
results. Information on stack parameters and stack locations were also 
derived from ERT. For facilities that had not yet submitted their test 
information to ERT, the emission limits were used as placeholders until 
industry could review the information. When operating hours were not in 
ERT, a placeholder of 8,760 hours was used until industry could review 
the information. When stack parameters and stack locations were not in 
ERT, other sources of information such as the 2013 Universal Industrial 
Sectors Integrated Solutions (UISIS) modeling file created by the EPA 
and the 2011 National Emissions Inventory (NEI) were used. As a check 
on the emissions data, operating hours, stack parameters, and stack 
locations compiled for each facility, a draft of the dataset consisting 
of the data for all the facilities under a single company was sent to a 
representative at the appropriate company for review. Instructions for 
reviewing and making changes to the dataset required that any revisions 
be supported with appropriate documentation. In addition, example 
calculations for emissions estimates and default stack parameters were 
provided. Revisions made to the data for each facility were 
incorporated into a master final dataset. The master final dataset was 
subjected to further quality evaluation. For example, exhaust gas 
flowrates were checked using information on stack diameters and gas 
velocities. Stack diameters and stack velocities are checked for 
outliers. Stack locations were also checked using Google Earth[supreg] 
to ensure that stack locations were correctly located at the cement 
manufacturing facility.
    The derivation of actual emission estimates is discussed in more 
detail in the document, Development of the RTR Risk Modeling Dataset 
for the Portland Cement Manufacturing Industry Source Category, which 
is available in the docket for this proposed rulemaking.
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 the specified annual time 
period. In some cases, these ``actual'' emission levels are lower than 
the emission levels required to comply with the current MACT standards. 
The emissions level allowed to be emitted by the MACT standards is 
referred to as the ``MACT-allowable'' emissions level. We discussed the 
use of both MACT-allowable and actual emissions in the final Coke Oven 
Batteries RTR (70 FR 19998-19999, April 15, 2005) and in the proposed 
and final Hazardous Organic NESHAP RTRs (71 FR 34428, June 14, 2006, 
and 71 FR 76609, December 21, 2006, respectively). In those actions, we 
noted that assessing the risks at the MACT-allowable level is 
inherently reasonable since these risks reflect 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, 
September 14, 1989).
    Allowable emissions are calculated using the emission limits in the 
rule for existing sources along with the emission factors for metallic 
HAP, organic HAP, and D/F congeners, the annual production capacity, 
and, when the emission limit is a concentration-based limit, the annual 
hours of operation reported by each source. We note that these are 
conservative estimates of allowable emissions. It is unlikely that 
emissions would be at the maximum limit at all times because sources 
cannot emit HAP at a level that is exactly equal to the limit and 
remain in compliance with the standard due to day-to-day variability in 
process operations and emissions. On average, facilities must emit at 
some level below the MACT limit to ensure that they are always in 
compliance. The derivation of allowable emissions is discussed in more 
detail in the document, Development of the RTR Risk Modeling Dataset 
for the Portland Cement Manufacturing Industry Source Category, which 
is available in the docket for this proposed rulemaking.
3. How did we conduct dispersion modeling, determine inhalation 
exposures, and estimate individual and population inhalation risks?
    Both long-term and short-term inhalation exposure concentrations 
and health risks from the source category addressed in this proposal 
were estimated using the Human Exposure Model (Community and Sector 
HEM-3). 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,\3\ and (3) estimating individual and population-level 
inhalation risks using the exposure estimates and quantitative dose-
response information.
---------------------------------------------------------------------------

    \3\ This metric comes from the Benzene NESHAP. See 54 FR 38046, 
September 14, 1989.
---------------------------------------------------------------------------

    The air dispersion model used by the HEM-3 model (AERMOD) is one of 
the EPA's preferred models for assessing pollutant concentrations from 
industrial facilities.\4\ 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 for more than 800 
meteorological stations, selected to provide coverage of the U.S. and 
Puerto Rico. A second library of U.S. Census Bureau census block \5\ 
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 unit risk factors and other health benchmarks is used to 
estimate health risks. These risk factors and health benchmarks are the 
latest values recommended by the EPA for HAP and other toxic air 
pollutants. These values are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants and are discussed in more detail later in this 
section.
---------------------------------------------------------------------------

    \4\ 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).
    \5\ A census block is the smallest geographic area for which 
census statistics are tabulated.
---------------------------------------------------------------------------

    In developing the risk assessment for chronic exposures, we used 
the

[[Page 44262]]

estimated annual average ambient air concentrations of each HAP emitted 
by each source for which we have emissions data in the source category. 
The air concentrations at each nearby census block centroid were used 
as a surrogate for the chronic inhalation exposure concentration for 
all the people who reside in that census block. We calculated the MIR 
for each facility as the cancer risk associated with a continuous 
lifetime (24 hours per day, 7 days per week, and 52 weeks per year for 
a 70-year period) exposure to the maximum concentration at the centroid 
of inhabited census blocks. Individual cancer risks were calculated by 
multiplying the estimated lifetime exposure to the ambient 
concentration of each of the HAP (in micrograms per cubic meter ([mu]g/
m\3\)) by its unit risk estimate (URE). The URE is an upper bound 
estimate of an individual's probability of contracting cancer over a 
lifetime of exposure to a concentration of 1 microgram of the pollutant 
per cubic meter of air. For residual risk assessments, we generally use 
URE values from the EPA's Integrated Risk Information System (IRIS). 
For carcinogenic pollutants without IRIS values, we look to other 
reputable sources of cancer dose-response values, often using 
California EPA (CalEPA) URE values, where available. In cases where 
new, scientifically credible dose response values have been developed 
in a manner consistent with the EPA guidelines and have undergone a 
peer review process similar to that used by the EPA, we may use such 
dose-response values in place of, or in addition to, other values, if 
appropriate.
    The EPA estimated incremental individual lifetime cancer risks 
associated with emissions from the facilities in the source category as 
the sum of the risks for each of the carcinogenic HAP (including those 
classified as carcinogenic to humans, likely to be carcinogenic to 
humans, and suggestive evidence of carcinogenic potential \6\) emitted 
by the modeled sources. Cancer incidence and the distribution of 
individual cancer risks for the population within 50 km of the sources 
were also estimated for the source category as part of this assessment 
by summing individual risks. A distance of 50 km is consistent with 
both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044, 
September 14, 1989) and the limitations of Gaussian dispersion models, 
including AERMOD.
---------------------------------------------------------------------------

    \6\ These classifications also coincide with the terms ``known 
carcinogen, probable carcinogen, and possible carcinogen,'' 
respectively, which are the terms advocated in the EPA's previous 
Guidelines for Carcinogen Risk Assessment, published in 1986 (51 FR 
33992, September 24, 1986). 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 risks of these individual compounds to obtain the cumulative 
cancer risks is an approach that was recommended by the EPA's SAB in 
their 2002 peer review of the EPA's National Air Toxics Assessment 
(NATA) titled, NATA--Evaluating the National-scale Air Toxics 
Assessment 1996 Data--an SAB Advisory, available at http://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
---------------------------------------------------------------------------

    To assess the risk of non-cancer health effects from chronic 
exposures, we summed the HQ for each of the HAP that affects a common 
target organ system to obtain the HI for that target organ system (or 
target organ-specific HI, TOSHI). The HQ is the estimated exposure 
divided by the chronic reference value, which is a value selected from 
one of several sources. First, the chronic reference level can be the 
EPA reference concentration (RfC) (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary), 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.'' Alternatively, in cases 
where an RfC from the EPA's IRIS database is not available or where the 
EPA determines that using a value other than the RfC is appropriate, 
the chronic reference level can be a value from the following 
prioritized sources: (1) The Agency for Toxic Substances and Disease 
Registry (ATSDR) Minimal Risk Level (MRL) (http://www.atsdr.cdc.gov/mrls/index.asp), which is defined as ``an estimate of daily human 
exposure to a hazardous substance that is likely to be without an 
appreciable risk of adverse non-cancer health effects (other than 
cancer) over a specified duration of exposure''; (2) the CalEPA Chronic 
Reference Exposure Level (REL) (http://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0), which is defined as ``the concentration level (that is 
expressed in units of [mu]g/m\3\ for inhalation exposure and in a dose 
expressed in units of milligram per kilogram-day (mg/kg-day) for oral 
exposures), at or below which no adverse health effects are anticipated 
for a specified exposure duration''; or (3), as noted above, a 
scientifically credible dose-response value that has been developed in 
a manner consistent with the EPA guidelines and has undergone a peer 
review process similar to that used by the EPA, in place of or in 
concert with other values.
    As mentioned above, in order to characterize non-cancer chronic 
effects, and in response to key recommendations from the SAB, the EPA 
selects dose-response values that reflect the best available science 
for all HAP included in RTR risk assessments.\7\ More specifically, for 
a given HAP, the EPA examines the availability of inhalation reference 
values from the sources included in our tiered approach (e.g., IRIS 
first, ATSDR second, CalEPA third) and determines which inhalation 
reference value represents the best available science. Thus, as new 
inhalation reference values become available, the EPA will typically 
evaluate them and determine whether they should be given preference 
over those currently being used in RTR risk assessments.
---------------------------------------------------------------------------

    \7\ Recommendations from the SAB's review of RTR Risk Assessment 
Methodologies and the review materials are available at http://
yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf 
and at https://cfpub.epa.gov/si/si_publiclowbar;record_report.cfm?dirEntryID=238928, respectively.
---------------------------------------------------------------------------

    The EPA also evaluated screening estimates of acute exposures and 
risks for each of the HAP (for which appropriate acute dose-response 
values are available) at the point of highest potential off-site 
exposure for each facility. To do this, the EPA estimated the risks 
when both the peak hourly emissions rate and worst-case dispersion 
conditions occur. We also assume that a person is located at the point 
of highest impact during that same time. In accordance with our mandate 
in section 112 of the CAA, we use the point of highest off-site 
exposure to assess the potential risk to the maximally exposed 
individual. The acute HQ is the estimated acute exposure divided by the 
acute dose-response value. In each case, the EPA calculated acute HQ 
values using best available, short-term dose-response values. These 
acute dose-response values, which are described below, include the 
acute REL, acute exposure guideline levels (AEGL) and Emergency 
Response Planning Guidelines (ERPG) for 1-hour exposure durations. As 
discussed below, we used conservative assumptions for emissions rates, 
meteorology, and exposure location.
    As described in the CalEPA's Air Toxics Hot Spots Program Risk

[[Page 44263]]

Assessment Guidelines, Part I, The Determination of Acute Reference 
Exposure Levels for Airborne Toxicants, an acute REL value (http://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary) is defined as ``the concentration level at 
or below which no adverse health effects are anticipated for a 
specified exposure duration.'' Id. at page 2. Acute REL values are 
based on the most sensitive, relevant, adverse health effect reported 
in the peer-reviewed medical and toxicological literature. Acute REL 
values 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.
    AEGL values were derived in response to recommendations from the 
National Research Council (NRC). The National Advisory Committee (NAC) 
for the Development of Acute Exposure Guideline Levels for Hazardous 
Substances, usually referred to as the AEGL Committee or the NAC/AEGL 
committee, developed AEGL values for at least 273 of the 329 chemicals 
on the AEGL priority chemical list. The last meeting of the NAC/AEGL 
Committee was in April 2010, and its charter expired in October 2011. 
The NAC/AEGL Committee 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).
    As described in Standing Operating Procedures (SOP) of the National 
Advisory Committee on Acute Exposure Guideline Levels for Hazardous 
Chemicals (https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf),\8\ ``the 
NRC's previous name for acute exposure levels--community emergency 
exposure levels--was replaced by the term AEGL to reflect the broad 
application of these values to planning, response, and prevention in 
the community, the workplace, transportation, the military, and the 
remediation of Superfund sites.'' Id. at 2. This document also states 
that AEGL values ``represent threshold exposure limits for the general 
public and are applicable to emergency exposures ranging from 10 
minutes to eight hours.'' Id. at 2.
---------------------------------------------------------------------------

    \8\ National Academy of Sciences (NAS), 2001. Standing Operating 
Procedures for Developing Acute Exposure Levels for Hazardous 
Chemicals, page 2.
---------------------------------------------------------------------------

    The document lays out the purpose and objectives of AEGL by stating 
that ``the primary purpose of the AEGL program and the National 
Advisory Committee for Acute Exposure Guideline Levels for Hazardous 
Substances is to develop guideline levels for once-in-a-lifetime, 
short-term exposures to airborne concentrations of acutely toxic, high-
priority chemicals.'' Id. at 21. In detailing the intended application 
of AEGL values, the document states that ``[i]t is anticipated that the 
AEGL values will be used for regulatory and nonregulatory purposes by 
U.S. Federal and state agencies and possibly the international 
community in conjunction with chemical emergency response, planning, 
and prevention programs. More specifically, the AEGL values will be 
used for conducting various risk assessments to aid in the development 
of emergency preparedness and prevention plans, as well as real-time 
emergency response actions, for accidental chemical releases at fixed 
facilities and from transport carriers.'' Id. at 31.
    The AEGL-1 value is then specifically defined as ``the airborne 
concentration (expressed as ppm (parts per million) or mg/m\3\ 
(milligrams per cubic meter)) of a substance above which it is 
predicted that the general population, including susceptible 
individuals, could experience notable discomfort, irritation, or 
certain asymptomatic nonsensory effects. However, the effects are not 
disabling and are transient and reversible upon cessation of 
exposure.'' Id. at 3. The document also notes that, ``Airborne 
concentrations below AEGL-1 represent exposure levels that can produce 
mild and progressively increasing but transient and nondisabling odor, 
taste, and sensory irritation or certain asymptomatic, nonsensory 
effects.'' Id. Similarly, the document defines AEGL-2 values 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.
    ERPG values are derived for use in emergency response, as described 
in the American Industrial Hygiene Association's Emergency Response 
Planning (ERP) Committee document titled, ERPGS Procedures and 
Responsibilities (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), which 
states that, ``Emergency Response Planning Guidelines were developed 
for emergency planning and are intended as health based guideline 
concentrations for single exposures to chemicals.'' \9\ Id. at 1. The 
ERPG-1 value is defined as ``the maximum airborne concentration below 
which it is believed that nearly all individuals could be exposed for 
up to 1 hour without experiencing other than mild transient adverse 
health effects or without perceiving a clearly defined, objectionable 
odor.'' Id. at 2. Similarly, the ERPG-2 value is defined as ``the 
maximum airborne concentration below which it is believed that nearly 
all individuals could be exposed for up to 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.
---------------------------------------------------------------------------

    \9\ ERP Committee Procedures and Responsibilities. March 2014. 
American Industrial Hygiene Association.
---------------------------------------------------------------------------

    As can be seen from the definitions above, the AEGL and ERPG values 
include the similarly-defined severity levels 1 and 2. For many 
chemicals, a severity level 1 value AEGL or ERPG has not been developed 
because the types of effects for these chemicals are not consistent 
with the AEGL-1/ERPG-1 definitions; in these instances, we compare 
higher severity level AEGL-2 or ERPG-2 values to our modeled exposure 
levels to screen for potential acute concerns. When AEGL-1/ERPG-1 
values are available, they are used in our acute risk assessments.
    Acute REL values for 1-hour exposure durations are typically lower 
than their corresponding AEGL-1 and ERPG-1 values. Even though their 
definitions are slightly different, AEGL-1 values are often the same as 
the corresponding ERPG-1 values, and AEGL-2 values are often equal to 
ERPG-2 values. Maximum HQ values from our acute screening risk 
assessments typically result when basing them on the acute REL value 
for a particular pollutant. In cases where our maximum acute HQ value 
exceeds 1, we also report the HQ value based on the next highest acute 
dose-response value (usually the AEGL-1 and/or the ERPG-1 value).
    To develop screening estimates of acute exposures in the absence of 
hourly emissions data, generally we first develop estimates of maximum 
hourly emissions rates by multiplying the

[[Page 44264]]

average actual annual hourly emissions rates by a default factor to 
cover routinely variable emissions. We choose the factor to use 
partially based on process knowledge and engineering judgment. The 
factor chosen also reflects a Texas study of short-term emissions 
variability, which showed that most peak emission events in a heavily-
industrialized four-county area (Harris, Galveston, Chambers, and 
Brazoria Counties, Texas) were less than twice the annual average 
hourly emissions rate. The highest peak emissions event was 74 times 
the annual average hourly emissions rate, and the 99th percentile ratio 
of peak hourly emissions rate to the annual average hourly emissions 
rate was 9.\10\ Considering this analysis, to account for more than 99 
percent of the peak hourly emissions, we apply a conservative screening 
multiplication factor of 10 to the average annual hourly emissions rate 
in our acute exposure screening assessments as our default approach. A 
further discussion of why this factor was chosen can be found in the 
memorandum, Emissions Data and Acute Risk Factor Used in Residual Risk 
Modeling: Portland Cement Manufacturing Industry, available in the 
docket for this rulemaking.
---------------------------------------------------------------------------

    \10\ Allen, et al., 2004. Variable Industrial VOC Emissions and 
their impact on ozone formation in the Houston Galveston Area. Texas 
Environmental Research Consortium. https://www.researchgate.net/publication/237593060_Variable_Industrial_VOC_Emissions 
and_their_Impact_on_Ozone_Formation_in_the_Houston_Galveston_Area.
---------------------------------------------------------------------------

    As part of our acute risk assessment process, for cases where acute 
HQ values from the screening step are less than or equal to 1 (even 
under the conservative assumptions of the screening analysis), acute 
impacts are deemed negligible and no further analysis is performed for 
these HAP. In cases where an acute HQ from the screening step is 
greater than 1, additional site-specific data are considered to develop 
a more refined estimate of the potential for acute impacts of concern. 
For this source category, since no HQ was greater than 1, no further 
analysis was performed.
    Ideally, we would prefer to have continuous measurements over time 
to see how the emissions vary by each hour over an entire year. Having 
a frequency distribution of hourly emissions rates over a year would 
allow us to perform a probabilistic analysis to estimate potential 
threshold exceedances and their frequency of occurrence. Such an 
evaluation could include a more complete statistical treatment of the 
key parameters and elements adopted in this screening analysis. 
Recognizing that this level of data is rarely available, we instead 
rely on the multiplier approach.
    To better characterize the potential health risks associated with 
estimated acute exposures to HAP, and in response to a key 
recommendation from the SAB's 2010 peer review of the EPA's RTR risk 
assessment methodologies,\11\ we generally examine a wider range of 
available acute health metrics (e.g., RELs, AEGLs) than we do for our 
chronic risk assessments. This is in response to the SAB's 
acknowledgement that there are generally more data gaps and 
inconsistencies in acute reference values than there are in chronic 
reference values. In some cases, when Reference Value Arrays \12\ for 
HAP have been developed, we consider additional acute values (i.e., 
occupational and international values) to provide a more complete risk 
characterization.
---------------------------------------------------------------------------

    \11\ The SAB peer review of RTR Risk Assessment Methodologies is 
available at http://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
    \12\ U.S. EPA. Chapter 2.9, Chemical Specific Reference Values 
for Formaldehyde in Graphical Arrays of Chemical-Specific Health 
Effect Reference Values for Inhalation Exposures (Final Report). 
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
061, 2009, and available online at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=211003.
---------------------------------------------------------------------------

4. How did we conduct the multipathway exposure and risk screening?
    The EPA conducted a screening analysis examining the potential for 
significant human health risks due to exposures via routes other than 
inhalation (i.e., ingestion). We first determined whether any sources 
in the source category emitted any HAP known to be persistent and 
bioaccumulative in the environment (PB-HAP). The PB-HAP compounds or 
compound classes are identified for the screening from the EPA's Air 
Toxics Risk Assessment Library (available at http://www2.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the Portland Cement Manufacturing Industry source category, we 
identified emissions of lead compounds, cadmium compounds, mercury 
compounds, arsenic compounds, and D/F. Because one or more of these PB-
HAP are emitted by at least one facility in the Portland Cement 
Manufacturing Industry source category, we proceeded to the next step 
of the evaluation. In this step, we determined whether the facility-
specific emission rates of the emitted PB-HAP were large enough to 
create the potential for significant non-inhalation human health risks 
under reasonable worst-case conditions. To facilitate this step, we 
developed screening threshold emission rates for several PB-HAP using 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: Cadmium compounds, mercury 
compounds, arsenic compounds, and D/F and polycyclic organic matter 
(POM). We conducted a sensitivity analysis on the screening scenario to 
ensure that its key design parameters would represent the upper end of 
the range of possible values, such that it would represent a 
conservative, but not impossible scenario. The facility-specific PB-HAP 
emission rates were compared to their respective screening threshold 
emission rate to assess the potential for significant human health 
risks via non-inhalation pathways. We call this application of the 
TRIM.FaTE model the Tier 1 TRIM-screen or Tier 1 screen.
    For the purpose of developing emission rates for the Tier 1 TRIM-
screen, we derived emission levels for these PB-HAP (other than lead 
compounds) at which the maximum excess lifetime cancer risk would be 1-
in-1 million (i.e., D/F, arsenic compounds, and POM) or, for HAP that 
cause non-cancer health effects (i.e., cadmium compounds and mercury 
compounds), the maximum HQ would be 1. If the emission rate of any PB-
HAP included in the Tier 1 screen exceeds the Tier 1 screening 
threshold emission rates for any facility, we conduct a second screen, 
which we call the Tier 2 TRIM-screen or Tier 2 screen.
    In the Tier 2 screen, the location of each facility that exceeds 
the Tier 1 screening threshold emission rates is used to refine the 
assumptions associated with the environmental scenario while 
maintaining the exposure scenario assumptions. A key assumption that is 
part of the Tier 1 screen is that a lake is located near the facility; 
we confirm the existence of lakes near the facility as part of the Tier 
2 screen. We also examine the differences between local meteorology 
near the facility and the meteorology used in the Tier 1 screen. We 
then adjust the risk-based 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 meteorology and environmental

[[Page 44265]]

assumptions. PB-HAP emissions that do not exceed these new Tier 2 
screening threshold emission rates are considered to be below a level 
of concern. If the PB-HAP emissions for a facility exceed the Tier 2 
screening threshold emission rates and data are available, we may 
decide to conduct a more refined Tier 3 multipathway assessment or 
proceed to a site-specific assessment. There are several analyses that 
can be included in a Tier 3 screen depending upon the extent of 
refinement warranted, including validating that the lakes are fishable, 
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. For this source category a Tier 3 screen 
was conducted for 1 facility that had dioxin emissions exceeding the 
Tier 2 threshold emission rates up to a value of 100-in-1 million. If 
the Tier 3 screen is exceeded, the EPA may conduct a refined site-
specific assessment.
    When tiered screening values for any facility indicate a potential 
health risk to the public, we may conduct a more refined multipathway 
assessment. A refined assessment was conducted for mercury in lieu of 
conducting a Tier 3 screen. To select the candidate facilities for the 
site-specific assessment, we analyzed the facilities with the maximum 
exceedances of the Tier 2 screening values as well as the combined 
effect from multiple facilities on lakes within the same watershed. In 
addition to looking at the Tier 2 screen value for each lake, the 
location and number of lakes or farms impacted for each watershed was 
evaluated to assess elevation/topography influences. A review of the 
source category identified 3 facilities located in Midlothian, Texas, 
as the best candidates for mercury impacts. These candidate sites were 
selected because of their exceedances of the Tier 2 mercury screening 
value and based upon the above considerations.
    In evaluating the potential multipathway risk from emissions of 
lead compounds, rather than developing a screening threshold emission 
rate for them, we compared maximum estimated 1-hour acute inhalation 
exposures with the level of the current National Ambient Air Quality 
Standard (NAAQS) for lead.\13\ Values below the level of the Primary 
(health-based) Lead NAAQS were considered to have a low potential for 
multipathway risk.
---------------------------------------------------------------------------

    \13\ 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''). 
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 analysis approach, see 
the Residual Risk Assessment for the Portland Cement Manufacturing 
Industry Source Category in Support of the Risk and Technology Review 
September 2017 Proposed Rule, which is available in the docket for this 
action.
5. How did we assess risks considering emissions control options?
    In addition to assessing baseline inhalation risks and screening 
for potential multipathway risks, we also estimated risks considering 
the potential emission reductions that would be achieved by the control 
options under consideration. In these cases, the expected emission 
reductions were applied to the specific HAP and emission points in the 
RTR emissions dataset to develop corresponding estimates of risk and 
incremental risk reductions.
6. How did we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect
    The EPA conducts a screening assessment to examine the potential 
for adverse environmental effects 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.''
b. Environmental HAP
    The EPA focuses on eight HAP, which we refer to as ``environmental 
HAP,'' in its screening analysis: Six PB-HAP and two acid gases. The 
six PB-HAP are cadmium compounds, D/F, arsenic compounds, POM, mercury 
compounds (both inorganic mercury and methyl mercury), and lead 
compounds. The two acid gases are HCl and hydrogen fluoride (HF). The 
rationale for including these eight HAP in the environmental risk 
screening analysis is presented below.
    HAP that persist and bioaccumulate are of particular environmental 
concern because they accumulate in the soil, sediment, and water. The 
PB-HAP are taken up, through sediment, soil, water, and/or ingestion of 
other organisms, by plants or animals (e.g., small fish) at the bottom 
of the food chain. As larger and larger predators consume these 
organisms, concentrations of the PB-HAP in the animal tissues increases 
as does the potential for adverse effects. The six PB-HAP we evaluate 
as part of our screening analysis account for 99.8 percent of all PB-
HAP emissions nationally from stationary sources (on a mass basis from 
the 2005 EPA NEI).
    In addition to accounting for almost all of the mass of PB-HAP 
emitted, we note that the TRIM.FaTE model that we use to evaluate 
multipathway risk allows us to estimate concentrations of cadmium 
compounds, D/F, arsenic compounds, POM, and mercury compounds in soil, 
sediment, and water. For lead compounds, we currently do not have the 
ability to calculate these concentrations using the TRIM.FaTE model. 
Therefore, to evaluate the potential for adverse environmental effects 
from lead compounds, we compare the estimated HEM-modeled exposures 
from the source category emissions of lead with the level of the 
Secondary Lead NAAQS.\14\ We consider values below the level of the 
Secondary Lead NAAQS to be unlikely to cause adverse environmental 
effects.
---------------------------------------------------------------------------

    \14\ The Secondary Lead NAAQS is a reasonable measure of 
determining whether there is an adverse environmental effect since 
it was established considering ``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.''
---------------------------------------------------------------------------

    Due to their well-documented potential to cause direct damage to 
terrestrial plants, we include two acid gases, HCl and HF, in the 
environmental screening analysis. According to the 2005 NEI, HCl and HF 
account for about 99 percent (on a mass basis) of the total acid gas 
HAP emitted by stationary sources in the U.S. In addition to the 
potential to cause direct damage to plants, high concentrations of HF 
in the air have been linked to fluorosis in livestock. Air 
concentrations of these HAP are already calculated as part of the human 
multipathway exposure and risk screening analysis using the HEM3-AERMOD 
air dispersion model, and we are able to use the air dispersion 
modeling results to estimate the

[[Page 44266]]

potential for an adverse environmental effect.
    The EPA acknowledges that other HAP beyond the eight HAP discussed 
above may have the potential to cause adverse environmental effects. 
Therefore, the EPA may include other relevant HAP in its environmental 
risk screening in the future, as modeling science and resources allow. 
The EPA invites comment on the extent to which other HAP emitted by the 
source category may cause adverse environmental effects. Such 
information should include references to peer-reviewed ecological 
effects benchmarks that are of sufficient quality for making regulatory 
decisions, as well as information on the presence of organisms located 
near facilities within the source category that such benchmarks 
indicate could be adversely affected.
c. Ecological Assessment Endpoints and Benchmarks for PB-HAP
    An important consideration in the development of the EPA's 
screening methodology is the selection of ecological assessment 
endpoints and benchmarks. Ecological assessment endpoints are defined 
by the ecological entity (e.g., aquatic communities, including fish and 
plankton) and its attributes (e.g., frequency of mortality). Ecological 
assessment endpoints can be established for organisms, populations, 
communities or assemblages, and ecosystems.
    For PB-HAP (other than lead compounds), we evaluated the following 
community-level ecological assessment endpoints to screen for organisms 
directly exposed to HAP in soils, sediment, and water:
    <bullet> Local terrestrial communities (i.e., soil invertebrates, 
plants) and populations of small birds and mammals that consume soil 
invertebrates exposed to PB-HAP in the surface soil;
    <bullet> Local benthic (i.e., bottom sediment dwelling insects, 
amphipods, isopods, and crayfish) communities exposed to PB-HAP in 
sediment in nearby water bodies; and
    <bullet> Local aquatic (water-column) communities (including fish 
and plankton) exposed to PB-HAP in nearby surface waters.
    For PB-HAP (other than lead compounds), we also evaluated the 
following population-level ecological assessment endpoint to screen for 
indirect HAP exposures of top consumers via the bioaccumulation of HAP 
in food chains:
    <bullet> Piscivorous (i.e., fish-eating) wildlife consuming PB-HAP-
contaminated fish from nearby water bodies.
    For cadmium compounds, D/F, arsenic compounds, POM, and mercury 
compounds, we identified the available ecological benchmarks for each 
assessment endpoint. An ecological benchmark represents a concentration 
of HAP (e.g., 0.77 [micro]g of HAP per liter of water) that has been 
linked to a particular environmental effect level through scientific 
study. For PB-HAP we identified, where possible, ecological benchmarks 
at the following effect levels:
    <bullet> Probable effect levels (PEL): Level above which adverse 
effects are expected to occur frequently;
    <bullet> Lowest-observed-adverse-effect level (LOAEL): The lowest 
exposure level tested at which there are biologically significant 
increases in frequency or severity of adverse effects; and
    <bullet> No-observed-adverse-effect levels (NOAEL): The highest 
exposure level tested at which there are no biologically significant 
increases in the frequency or severity of adverse effect.
    We established a hierarchy of preferred benchmark sources to allow 
selection of benchmarks for each environmental HAP at each ecological 
assessment endpoint. In general, the EPA sources that are used at a 
programmatic level (e.g., Office of Water, Superfund Program) were used 
in the analysis, if available. If not, the EPA benchmarks used in 
Regional programs (e.g., Superfund) were used. If benchmarks were not 
available at a programmatic or Regional level, we used benchmarks 
developed by other federal agencies (e.g., National Oceanic and 
Atmospheric Administration (NOAA)) or state agencies.
    Benchmarks for all effect levels are not available for all PB-HAP 
and assessment endpoints. 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.
d. Ecological Assessment Endpoints and Benchmarks for Acid Gases
    The environmental screening analysis also evaluated potential 
damage and reduced productivity of plants due to direct exposure to 
acid gases in the air. For acid gases, we evaluated the following 
ecological assessment endpoint:
    <bullet> Local terrestrial plant communities with foliage exposed 
to acidic gaseous HAP in the air.
    The selection of ecological benchmarks for the effects of acid 
gases on plants followed the same approach as for PB-HAP (i.e., we 
examine all of the available chronic benchmarks). For HCl, the EPA 
identified chronic benchmark concentrations. We note that the benchmark 
for chronic HCl exposure to plants is greater than the reference 
concentration for chronic inhalation exposure for human health. This 
means that where the EPA includes regulatory requirements to prevent an 
exceedance of the reference concentration for human health, additional 
analyses for adverse environmental effects of HCl would not be 
necessary.
    For HF, the EPA identified chronic benchmark concentrations for 
plants and evaluated chronic exposures to plants in the screening 
analysis. High concentrations of HF in the air have also been linked to 
fluorosis in livestock. However, the HF concentrations at which 
fluorosis in livestock occur are higher than those at which plant 
damage begins. Therefore, the benchmarks for plants are protective of 
both plants and livestock.
e. Screening Methodology
    For the environmental risk screening analysis, the EPA first 
determined whether any facilities in the Portland Cement Manufacturing 
Industry sources emitted any of the eight environmental HAP. For the 
Portland Cement Manufacturing Industry source category, we identified 
emissions of lead compounds, cadmium compounds, mercury compounds, 
arsenic compounds, D/F, and HCl.
    Because one or more of the eight environmental HAP evaluated are 
emitted by at least one facility in the source category, we proceeded 
to the second step of the evaluation.
f. PB-HAP Methodology
    For cadmium compounds, arsenic compounds, mercury compounds, POM, 
and D/F, the environmental screening analysis consists of two tiers, 
while lead compounds are analyzed differently as discussed earlier. In 
the first tier, we determined whether the maximum facility-specific 
emission rates of each of the emitted environmental HAP were large 
enough to create the potential for adverse environmental effects under 
reasonable worst-case environmental conditions. These are the same 
environmental conditions used in the human multipathway exposure and 
risk screening analysis.
    To facilitate this step, TRIM.FaTE was run for each PB-HAP under 
hypothetical environmental conditions designed to provide 
conservatively high

[[Page 44267]]

HAP concentrations. The model was set to maximize runoff from 
terrestrial parcels into the modeled lake, which in turn, maximized the 
chemical concentrations in the water, the sediments, and the fish. The 
resulting media concentrations were then used to back-calculate a 
screening level emission rate that corresponded to the relevant 
exposure benchmark concentration value for each assessment endpoint. To 
assess emissions from a facility, the reported emission rate for each 
PB-HAP was compared to the screening level emission rate for that PB-
HAP for each assessment endpoint. If emissions from a facility do not 
exceed the Tier 1 screening level, the facility ``passes'' the screen, 
and, therefore, is not evaluated further under the screening approach. 
If emissions from a facility exceed the Tier 1 screening level, we 
evaluate the facility further in Tier 2.
    In Tier 2 of the environmental screening analysis, the emission 
rate screening levels 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 screen. The modeling domain for each facility in the 
Tier 2 analysis consists of 8 octants. Each octant contains 5 modeled 
soil concentrations at various distances from the facility (5 soil 
concentrations x 8 octants = total of 40 soil concentrations per 
facility) and one lake with modeled concentrations for water, sediment, 
and fish tissue. In the Tier 2 environmental risk screening analysis, 
the 40 soil concentration points are averaged to obtain an average soil 
concentration for each facility for each 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 level, the facility passes 
the screen, and typically is not evaluated further. If emissions from a 
facility exceed the Tier 2 screening level, the facility does not pass 
the screen and, therefore, may have the potential to cause adverse 
environmental effects. Such facilities are evaluated further to 
investigate factors such as the magnitude and characteristics of the 
area of exceedance.
g. Acid Gas Methodology
    The environmental screening analysis evaluates the potential 
phytotoxicity and reduced productivity of plants due to chronic 
exposure to acid gases. The environmental risk screening methodology 
for acid gases is a single-tier screen that compares the average off-
site ambient air concentration over the modeling domain to ecological 
benchmarks for each of the acid gases. Because air concentrations are 
compared directly to the ecological benchmarks, emission-based 
screening levels are not calculated for acid gases.
    For purposes of ecological risk screening, the EPA identifies a 
potential for adverse environmental effects to plant communities from 
exposure to acid gases when the average concentration of the HAP around 
a facility exceeds the LOAEL ecological benchmark. In such cases, we 
further investigate factors such as the magnitude and characteristics 
of the area of exceedance (e.g., land use of exceedance area, size of 
exceedance area) to determine if there is an adverse environmental 
effect.
    For further information on the environmental screening analysis 
approach, see the Residual Risk Assessment for the Portland Cement 
Manufacturing Industry Source Category in Support of the Risk and 
Technology Review September 2017 Proposed Rule, which is available in 
the docket for this action.
7. How did 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 the 2014 NEI. We analyzed risks due to the inhalation of HAP that 
are emitted ``facility-wide'' for the populations residing within 50 km 
of each facility, consistent with the methods used for the source 
category analysis described above. For these facility-wide risk 
analyses, the modeled source category risks were compared to the 
facility-wide risks to determine the portion of facility-wide risks 
that could be attributed to the source category addressed in this 
proposal. We specifically examined the facility that was associated 
with the highest estimate of risk and determined the percentage of that 
risk attributable to the source category of interest. The Residual Risk 
Assessment for the Portland Cement Manufacturing Industry Source 
Category in Support of the Risk and Technology Review September 2017 
Proposed Rule, available through the docket for this action, provides 
the methodology and results of the facility-wide analyses, including 
all facility-wide risks and the percentage of source category 
contribution to facility-wide risks.
8. How did we consider uncertainties in risk assessment?
    In the Benzene NESHAP, we concluded that risk estimation 
uncertainty should be considered in our decision-making under the ample 
margin of safety framework. 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 protective 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. A more thorough discussion of these 
uncertainties is included in the Residual Risk Assessment for the 
Portland Cement Manufacturing Industry Source Category in Support of 
the Risk and Technology Review September 2017 Proposed Rule, which is 
available in the docket for this action.
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,

[[Page 44268]]

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.
c. Uncertainties in Inhalation Exposure
    The EPA did not include the effects of human mobility on exposures 
in the assessment. Specifically, short-term mobility and long-term 
mobility between census blocks in the modeling domain were not 
considered.\15\ The approach of not considering short or long-term 
population mobility does not bias the estimate of the theoretical MIR 
(by definition), nor does it affect the estimate of cancer incidence 
because the total population number remains the same. It does, however, 
affect the shape of the distribution of individual risks across the 
affected population, shifting it toward higher estimated individual 
risks at the upper end and reducing the number of people estimated to 
be at lower risks, thereby increasing the estimated number of people at 
specific high risk levels (e.g., 1-in-10 thousand or 1-in-1 million).
---------------------------------------------------------------------------

    \15\ Short-term mobility is movement from one micro-environment 
to another over the course of hours or days. Long-term mobility is 
movement from one residence to another over the course of a 
lifetime.
---------------------------------------------------------------------------

    In addition, the assessment predicted the chronic exposures at the 
centroid of each populated census block as surrogates for the exposure 
concentrations for all people living in that block. Using the census 
block centroid to predict chronic exposures tends to over-predict 
exposures for people in the census block who live farther from the 
facility and under-predict exposures for people in the census block who 
live closer to the facility. Thus, using the census block centroid to 
predict chronic exposures may lead to a potential understatement or 
overstatement of the true maximum impact, but is an unbiased estimate 
of average risk and incidence. We reduce this uncertainty by analyzing 
large census blocks near facilities using aerial imagery and adjusting 
the location of the block centroid to better represent the population 
in the block, as well as adding additional receptor locations where the 
block population is not well represented by a single location.
    The assessment evaluates the cancer inhalation risks associated 
with pollutant exposures over a 70-year period, which is the assumed 
lifetime of an individual. In reality, both the length of time that 
modeled emission sources at facilities actually operate (i.e., more or 
less than 70 years) and the domestic growth or decline of the modeled 
industry (i.e., the increase or decrease in the number or size of 
domestic facilities) will influence the future risks posed by a given 
source or source category. Depending on the characteristics of the 
industry, these factors will, in most cases, result in an overestimate 
both in individual risk levels and in the total estimated number of 
cancer cases. However, in the unlikely scenario where a facility 
maintains, or even increases, its emissions levels over a period of 
more than 70 years, residents live beyond 70 years at the same 
location, and the residents spend most of their days at that location, 
then the cancer inhalation risks could potentially be underestimated. 
However, annual cancer incidence estimates from exposures to emissions 
from these sources would not be affected by the length of time an 
emissions source operates.
    The exposure estimates used in these analyses assume chronic 
exposures to ambient (outdoor) levels of pollutants. Because most 
people spend the majority of their time indoors, actual exposures may 
not be as high, depending on the characteristics of the pollutants 
modeled. For many of the HAP, indoor levels are roughly equivalent to 
ambient levels, but for very reactive pollutants or larger particles, 
indoor levels are typically lower. This factor has the potential to 
result in an overestimate of 25 to 30 percent of exposures.\16\
---------------------------------------------------------------------------

    \16\ U.S. EPA. National-Scale Air Toxics Assessment for 1996. 
(EPA 453/R-01-003; January 2001; page 85.)
---------------------------------------------------------------------------

    In addition to the uncertainties highlighted above, there are 
several factors specific to the acute exposure assessment that the EPA 
conducts as part of the risk review under section 112 of the CAA that 
should be highlighted. The accuracy of an acute inhalation exposure 
assessment depends on the simultaneous occurrence of independent 
factors that may vary greatly, such as hourly emissions rates, 
meteorology, and the presence of humans at the location of the maximum 
concentration. In the acute screening assessment that we conduct under 
the RTR program, we assume that peak emissions from the source category 
and worst-case meteorological conditions co-occur, thus, resulting in 
maximum ambient concentrations. These two events are unlikely to occur 
at the same time, making these assumptions conservative. We then 
include the additional assumption that a person is located at this 
point during this same time period. For this source category, these 
assumptions would tend to be worst-case actual exposures as it is 
unlikely that a person would be located at the point of maximum 
exposure during the time when peak emissions and worst-case 
meteorological conditions occur simultaneously.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and non-cancer effects from both chronic and acute 
exposures. Some uncertainties may be considered quantitatively, and 
others generally are expressed in qualitative terms. We note as a 
preface to this discussion a point on dose-response uncertainty that is 
brought out in the EPA's 2005 Cancer Guidelines; namely, that ``the 
primary goal of EPA actions is protection of human health; accordingly, 
as an Agency policy, risk assessment procedures, including default 
options that are used in the absence of scientific data to the 
contrary, should be health protective'' (EPA's 2005 Cancer Guidelines, 
pages 1-7). This is the approach followed here as summarized in the 
next several paragraphs. A complete detailed discussion of 
uncertainties and variability in dose-response relationships is given 
in the Residual Risk Assessment for the Portland Cement Manufacturing 
Industry Source Category in Support of the Risk and Technology Review 
September 2017 Proposed Rule, which is available in the docket for this 
action.
    Cancer URE values used in our risk assessments are those that have 
been developed to generally provide an upper bound estimate of risk. 
That is, they represent a ``plausible upper limit to the true value of 
a quantity'' (although this is usually not a true statistical 
confidence limit).\17\ In some circumstances, the true risk could be as

[[Page 44269]]

low as zero; however, in other circumstances, the risk could be 
greater.\18\ When developing an upper bound estimate of risk and to 
provide risk values that do not underestimate risk, health-protective 
default approaches are generally used. To err on the side of ensuring 
adequate health protection, the EPA typically uses the upper bound 
estimates rather than lower bound or central tendency estimates in our 
risk assessments, an approach that may have limitations for other uses 
(e.g., priority-setting or expected benefits analysis).
---------------------------------------------------------------------------

    \17\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \18\ An exception to this is the URE for benzene, which is 
considered to cover a range of values, each end of which is 
considered to be equally plausible, and which is based on maximum 
likelihood estimates.
---------------------------------------------------------------------------

    Chronic non-cancer RfC and reference dose (RfD) values represent 
chronic exposure levels that are intended to be health-protective 
levels. Specifically, these values provide an estimate (with 
uncertainty spanning perhaps an order of magnitude) of a continuous 
inhalation exposure (RfC) or a daily oral exposure (RfD) to the human 
population (including sensitive subgroups) that is likely to be without 
an appreciable risk of deleterious effects during a lifetime. To derive 
values that are intended to be ``without appreciable risk,'' the 
methodology relies upon an uncertainty factor (UF) approach (U.S. EPA, 
1993 and 1994) which considers uncertainty, variability, and gaps in 
the available data. The UF are applied to derive reference values that 
are intended to protect against appreciable risk of deleterious 
effects. The UF are commonly default values,\19\ (e.g., factors of 10 
or 3), used in the absence of compound-specific data; where data are 
available, a UF may also be developed using compound-specific 
information. When data are limited, more assumptions are needed and 
more UF are used. Thus, there may be a greater tendency to overestimate 
risk in the sense that further study might support development of 
reference values that are higher (i.e., less potent) because fewer 
default assumptions are needed. However, for some pollutants, it is 
possible that risks may be underestimated.
---------------------------------------------------------------------------

    \19\ According to the NRC report, Science and Judgment in Risk 
Assessment (NRC, 1994) ``[Default] options are generic approaches, 
based on general scientific knowledge and policy judgment, that are 
applied to various elements of the risk assessment process when the 
correct scientific model is unknown or uncertain.'' The 1983 NRC 
report, Risk Assessment in the Federal Government: Managing the 
Process, defined default option as ``the option chosen on the basis 
of risk assessment policy that appears to be the best choice in the 
absence of data to the contrary'' (NRC, 1983a, p. 63). Therefore, 
default options are not rules that bind the Agency; rather, the 
Agency may depart from them in evaluating the risks posed by a 
specific substance when it believes this to be appropriate. In 
keeping with the EPA's goal of protecting public health and the 
environment, default assumptions are used to ensure that risk to 
chemicals is not underestimated (although defaults are not intended 
to overtly overestimate risk). See EPA, An Examination of EPA Risk 
Assessment Principles and Practices, EPA/100/B-04/001, 2004, 
available at https://nctc.fws.gov/resources/course-resources/pesticides/Risk%20Assessment/Risk%20Assessment%20Principles%20and%20Practices.pdf.
---------------------------------------------------------------------------

    While collectively termed ``UF,'' these factors account for a 
number of different quantitative considerations when using observed 
animal (usually rodent) or human toxicity data in the development of 
the RfC. The UF are intended to account for: (1) Variation in 
susceptibility among the members of the human population (i.e., inter-
individual variability); (2) uncertainty in extrapolating from 
experimental animal data to humans (i.e., interspecies differences); 
(3) uncertainty in extrapolating from data obtained in a study with 
less-than-lifetime exposure (i.e., extrapolating from sub-chronic to 
chronic exposure); (4) uncertainty in extrapolating the observed data 
to obtain an estimate of the exposure associated with no adverse 
effects; and (5) uncertainty when the database is incomplete or there 
are problems with the applicability of available studies.
    Many of the UF used to account for variability and uncertainty in 
the development of acute reference values are quite similar to those 
developed for chronic durations, but they more often use individual UF 
values that may be less than 10. The UF are applied based on chemical-
specific or health effect-specific information (e.g., simple irritation 
effects do not vary appreciably between human individuals, hence a 
value of 3 is typically used), or based on the purpose for the 
reference value (see the following paragraph). The UF applied in acute 
reference value derivation include: (1) Heterogeneity among humans; (2) 
uncertainty in extrapolating from animals to humans; (3) uncertainty in 
lowest observed adverse effect (exposure) level to no observed adverse 
effect (exposure) level adjustments; and (4) uncertainty in accounting 
for an incomplete database on toxic effects of potential concern. 
Additional adjustments are often applied to account for uncertainty in 
extrapolation from observations at one exposure duration (e.g., 4 
hours) to derive an acute reference value at another exposure duration 
(e.g., 1 hour).
    Not all acute reference values are developed for the same purpose, 
and care must be taken when interpreting the results of an acute 
assessment of human health effects relative to the reference value or 
values being exceeded. Where relevant to the estimated exposures, the 
lack of short-term dose-response values at different levels of severity 
should be factored into the risk characterization as potential 
uncertainties.
    Although every effort is made to identify appropriate human health 
effect dose-response assessment values for all pollutants emitted by 
the sources in this risk assessment, some HAP emitted by this source 
category are lacking dose-response assessments. Accordingly, these 
pollutants cannot be included in the quantitative risk assessment, 
which could result in quantitative estimates understating HAP risk. To 
help to alleviate this potential underestimate, where we conclude 
similarity with a HAP for which a dose-response assessment value is 
available, we use that value as a surrogate for the assessment of the 
HAP for which no value is available. To the extent use of surrogates 
indicates appreciable risk, we may identify a need to increase priority 
for new IRIS assessment of that substance. We additionally note that, 
generally speaking, HAP of greatest concern due to environmental 
exposures and hazard are those for which dose-response assessments have 
been performed, reducing the likelihood of understating risk. Further, 
HAP not included in the quantitative assessment are assessed 
qualitatively and considered in the risk characterization that informs 
the risk management decisions, including with regard to consideration 
of HAP reductions achieved by various control options.
    For a group of compounds that are unspeciated (e.g., glycol 
ethers), we conservatively use the most protective reference 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 reference value, we also apply the most 
protective reference value from the other compounds in the group to 
estimate risk.
e. Uncertainties in the Multipathway Assessment
    For each source category, we generally rely on site-specific levels 
of PB-HAP emissions to determine whether a refined assessment of the 
impacts from multipathway exposures is necessary. This determination is 
based on the results of a three-tiered screening analysis that relies 
on the outputs from models that estimate environmental pollutant 
concentrations and human exposures for five PB-HAP. Two important types 
of uncertainty

[[Page 44270]]

associated with the use of these models in RTR risk assessments and 
inherent to any assessment that relies on environmental modeling are 
model uncertainty and input uncertainty.\20\
---------------------------------------------------------------------------

    \20\ 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 selected models are 
appropriate for the assessment being conducted and whether they 
adequately represent the actual processes that might occur for that 
situation. An example of model uncertainty is the question of whether 
the model adequately describes 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 screen are appropriate and 
state-of-the-art for the multipathway risk assessments conducted in 
support of RTR.
    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 screen, 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 and 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 assessment, 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 screen. The 
assumptions and the associated uncertainties regarding the selected 
ingestion exposure scenario are the same for Tier 1 and Tier 2.
    For both Tiers 1 and 2 of the multipathway assessment, 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 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 not screen out, it does not 
mean that multipathway impacts are significant, only that we cannot 
rule out that possibility and that a refined multipathway analysis for 
the site might be necessary to obtain a more accurate risk 
characterization for the source category. The site-specific 
multipathway assessment improves upon the screens by utilizing AERMOD 
to estimate dispersion and deposition impacts upon delineated 
watersheds and farms. This refinement also provides improved soil and 
water run-off calculations for effected watershed(s) and adjacent 
parcels in estimating media concentrations for each PB-HAP modeled.
    For further information on uncertainties and the Tier 1 and 2 
screening methods, refer to Appendix 5 of the risk report, ``Technical 
Support Document for TRIM-Based Multipathway Tiered Screening 
Methodology for RTR: Summary of Approach and Evaluation.''
f. Uncertainties in the Environmental Risk Screening Assessment
    For each source category, we generally rely on site-specific levels 
of environmental HAP emissions to perform an environmental screening 
assessment. The environmental screening assessment is based on the 
outputs from models that estimate environmental HAP concentrations. The 
TRIM.FaTE multipathway model and the AERMOD air dispersion model, are 
used to estimate environmental HAP concentrations for the environmental 
screening analysis. The human multipathway screening analysis are based 
upon the TRIM.FaTE model, while the site-specific assessments 
incorporate AERMOD model runs into the TRIM.FaTE model runs. Therefore, 
both screening assessments have similar modeling uncertainties.
    Two important types of uncertainty associated with the use of these 
models in RTR environmental screening assessments (and inherent to any 
assessment that relies on environmental modeling) are model uncertainty 
and input uncertainty.\21\
---------------------------------------------------------------------------

    \21\ In the context of this discussion, the term 
``uncertainty,'' as it pertains to exposure and risk assessment, 
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 selected models are 
appropriate for the assessment being conducted and whether they 
adequately represent the movement and accumulation of environmental HAP 
emissions 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 screen are appropriate and state-
of-the-art for the environmental risk assessments conducted in support 
of our RTR analyses.
    Input uncertainty is concerned with how accurately the models have 
been configured and parameterized for the assessment at hand. For Tier 
1 of the environmental screen for PB-HAP, we configured the models to 
avoid underestimating exposure and risk to reduce the likelihood that 
the results indicate the risks are lower than they actually are. 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, the location and size of any bodies of water, 
meteorology, surface water and soil characteristics, and structure of 
the aquatic food web. In Tier 1, we used the maximum facility-specific 
emissions for the PB-HAP (other than lead compounds, which were 
evaluated by comparison to the Secondary Lead NAAQS) that were included 
in the environmental screening assessment and each of the media when 
comparing to ecological benchmarks. This is consistent with the 
conservative design of Tier 1 of the screen. In Tier 2 of the 
environmental screening analysis for PB-HAP, 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 locations 
of water bodies near the facility location. By refining the

[[Page 44271]]

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 screen. To better represent widespread impacts, the 
modeled soil concentrations are averaged in Tier 2 to obtain one 
average soil concentration value for each facility and for each PB-HAP. 
For PB-HAP concentrations in water, sediment, and fish tissue, the 
highest value for each facility for each pollutant is used.
    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 both Tiers 1 and 2 of the environmental screening assessment, 
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 potential risks for adverse environmental 
impacts.
    Uncertainty also exists in the ecological benchmarks for the 
environmental risk screening analysis. We established a hierarchy of 
preferred benchmark sources to allow selection of benchmarks for each 
environmental HAP at each ecological assessment endpoint. In general, 
EPA benchmarks used at a programmatic level (e.g., Office of Water, 
Superfund Program) were used if available. If not, we used EPA 
benchmarks used in regional programs (e.g., Superfund Program). If 
benchmarks were not available at a programmatic or regional level, we 
used benchmarks developed by other agencies (e.g., NOAA) or by state 
agencies.
    In all cases (except for lead compounds, which were evaluated 
through a comparison to the NAAQS), we searched for benchmarks at the 
following three effect levels, as described in section III.A.6 of this 
preamble:
    1. A no-effect level (i.e., NOAEL).
    2. Threshold-effect level (i.e., LOAEL).
    3. Probable effect level (i.e., PEL).
    For some ecological assessment endpoint/environmental HAP 
combinations, we could identify benchmarks for all three effect levels, 
but for most, we could not. In one case, where different agencies 
derived significantly different numbers to represent a threshold for 
effect, we included both. In several cases, only a single benchmark was 
available. In cases where multiple effect levels were available for a 
particular PB-HAP and assessment endpoint, we used all of the available 
effect levels to help us to determine whether risk exists and if the 
risks could be considered significant and widespread.
    The EPA evaluates the following eight HAP in the environmental risk 
screening assessment: cadmium compounds, D/F, arsenic compounds, POM, 
mercury compounds (both inorganic mercury and methyl mercury), lead 
compounds, HCl, and HF, where applicable. These eight HAP represent 
pollutants that can cause adverse impacts for plants and animals either 
through direct exposure to HAP in the air or through exposure to HAP 
that is deposited from the air onto soils and surface waters. These 
eight HAP also represent those HAP for which we can conduct a 
meaningful environmental risk screening assessment. For other HAP not 
included in our screening assessment, 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 the eight HAP that we are evaluating 
may have the potential to cause adverse environmental effects and, 
therefore, the EPA may evaluate other relevant HAP in the future, as 
modeling science and resources allow.
    Further information on uncertainties and the Tier 1 and 2 
environmental screening methods is provided in Appendix 5 of the 
document, Technical Support Document for TRIM-Based Multipathway Tiered 
Screening Methodology for RTR: Summary of Approach and Evaluation. 
Also, see the Residual Risk Assessment for Portland Cement 
Manufacturing Industry Source Category in Support of the Risk and 
Technology Review September 2017 Proposed Rule, available in the docket 
for this action.

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

    As discussed in section II.A of this preamble, in evaluating and 
developing standards under CAA section 112(f)(2), we apply a two-step 
process to address residual risk. In the first step, the EPA determines 
whether risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) 
\22\ of approximately [1-in-10 thousand] [i.e., 100-in-1 million].'' 54 
FR 38045, September 14, 1989. If risks are unacceptable, the EPA must 
determine the emission standards necessary to bring risks to an 
acceptable level without considering costs. In the second step of the 
process, the EPA considers whether the emissions standards provide an 
ample margin of safety ``in consideration of all health information, 
including the number of persons at risk levels higher than 
approximately 1-in-1 million, as well as other relevant factors, 
including costs and economic impacts, technological feasibility, and 
other factors relevant to each particular decision.'' Id. The EPA must 
promulgate emission standards necessary to provide an ample margin of 
safety. 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.
---------------------------------------------------------------------------

    \22\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk were an individual exposed to the maximum level 
of a pollutant for a lifetime.
---------------------------------------------------------------------------

    In past residual risk actions, the EPA considered a number of human 
health risk metrics associated with emissions from the categories under 
review, including the MIR, the number of persons in various risk 
ranges, cancer incidence, the maximum non-cancer HI and the maximum 
acute non-cancer hazard. See, e.g., 72 FR 25138, May 3, 2007; and 71 FR 
42724, July 27, 2006. The EPA considered this health information for 
both actual and allowable emissions. See, e.g., 75 FR 65068, October 
21, 2010; 75 FR 80220, December 21, 2010; 76 FR 29032, May 19, 2011. 
The EPA also discussed risk estimation uncertainties and considered the 
uncertainties in the determination of acceptable risk and ample margin 
of safety in these past actions. The EPA considered this same type of 
information in support of this action.
    The Agency is considering these various measures of health 
information to inform our determinations of risk acceptability and 
ample margin of safety under CAA section 112(f). As explained in the 
Benzene NESHAP, ``the first step judgment on acceptability cannot be 
reduced to any single factor'' and, thus, ``[t]he Administrator 
believes that the acceptability of risk under [previous] section 112 is 
best judged on the basis of a broad set of health risk measures and 
information.'' 54 FR 38046, September 14, 1989. Similarly, with

[[Page 44272]]

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. In responding to comment on our 
policy under the Benzene NESHAP, the EPA explained that:

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

    See 54 FR at 38057, September 14, 1989. Thus, the level of the MIR 
is only one factor to be weighed in determining acceptability of risks. 
The Benzene NESHAP explained that ``an MIR of approximately 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 MIR less than the 
presumptively acceptable level is unacceptable in the light of other 
health risk factors.'' Id. at 38045. Similarly, with regard to the 
ample margin of safety analysis, the 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 those HAP risks that may be associated with 
emissions from other facilities that do not include the source 
categories in question, mobile source emissions, natural source 
emissions, persistent environmental pollution, or atmospheric 
transformation in the vicinity of the sources in these categories.
    The Agency understands the potential importance of considering an 
individual's total exposure to HAP in addition to considering exposure 
to HAP emissions from the source category and facility. We recognize 
that such consideration may be particularly important when assessing 
non-cancer risks, where pollutant-specific exposure health reference 
levels (e.g., RfCs) are based on the assumption that thresholds exist 
for adverse health effects. For example, the Agency recognizes that, 
although exposures attributable to emissions from a source category or 
facility alone may not indicate the potential for increased risk of 
adverse non-cancer health effects in a population, the exposures 
resulting from emissions from the facility in combination with 
emissions from all of the other sources (e.g., other facilities) to 
which an individual is exposed may be sufficient to result in increased 
risk of adverse non-cancer health effects. In May 2010, the 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.'' \23\
---------------------------------------------------------------------------

    \23\ The EPA's responses to this and all other key 
recommendations of the SAB's advisory on RTR risk assessment 
methodologies (which is available at: http://yosemite.epa.gov/sab/
sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-
007-unsigned.pdf) are outlined in a memorandum to this rulemaking 
docket from David Guinnup titled, EPA's Actions in Response to the 
Key Recommendations of the SAB Review of RTR Risk Assessment 
Methodologies.
---------------------------------------------------------------------------

    In response to the SAB recommendations, the EPA is incorporating 
cumulative risk analyses into its RTR risk assessments, including those 
reflected in this proposal. The Agency is: (1) Conducting facility-wide 
assessments, which include source category emission points, as well as 
other emission points within the facilities; (2) considering sources in 
the same category whose emissions result in exposures to the same 
individuals; and (3) for some persistent and bioaccumulative 
pollutants, analyzing the ingestion route of exposure. In addition, the 
RTR risk assessments have always considered aggregate cancer risk from 
all carcinogens and aggregate non-cancer HI from all non-carcinogens 
affecting the same target organ system.
    Although we are interested in placing source category and facility-
wide HAP risks in the context of total HAP risks from all sources 
combined in the vicinity of each source, we are concerned about the 
uncertainties of doing so. Because of the contribution to total HAP 
risk from emission sources other than those that we have studied in 
depth during this RTR review, such estimates of total HAP risks 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.

C. How did we perform the technology review?

    Our technology review focused on the identification and evaluation 
of developments in practices, processes, and control technologies that 
have occurred since the MACT standards were promulgated. Where we 
identified such developments, in order to inform our decision of 
whether it is ``necessary'' to revise the emissions standards, we 
analyzed the technical feasibility of applying these developments and 
the estimated costs, energy implications, non-air environmental 
impacts, as well as considering the emission reductions. We also 
considered the appropriateness of applying controls to new sources 
versus retrofitting existing sources.
    Based on our analyses of the available data and information, we 
identified potential developments in practices, processes, and control 
technologies. For this exercise, we considered 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

[[Page 44273]]

MACT standards) that could result in additional emissions reduction;
    <bullet> Any work practice or operational procedure that was not 
identified or considered during development of the original MACT 
standards;
    <bullet> Any process change or pollution prevention alternative 
that could be broadly applied to the industry and that was not 
identified or considered during development of the original MACT 
standards; and
    <bullet> Any significant changes in the cost (including cost 
effectiveness) of applying controls (including controls the EPA 
considered during the development of the original MACT standards).
    In addition to reviewing the practices, processes, and control 
technologies that were considered at the time we originally developed 
(or last updated) the NESHAP, we reviewed a variety of data sources in 
our investigation of potential practices, processes, or controls to 
consider. Among the sources we reviewed were the NESHAP for various 
industries that were promulgated since the MACT standards being 
reviewed in this action. We reviewed the regulatory requirements and/or 
technical analyses associated with these regulatory actions to identify 
any practices, processes, and control technologies considered in these 
efforts that could be applied to emission sources in the Portland 
Cement Manufacturing Industry source category, as well as the costs, 
non-air impacts, and energy implications associated with the use of 
these technologies. Finally, we reviewed information from other 
sources, such as state and/or local permitting agency databases and 
industry-supported databases.

IV. Analytical Results and Proposed Decisions

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

1. Inhalation Risk Assessment Results
    Table 3 of this preamble provides an overall summary of the 
inhalation risk results. The results of the chronic baseline inhalation 
cancer risk assessment indicate that, based on estimates of current 
actual and allowable emissions, the MIR posed by the Portland Cement 
Manufacturing Industry source category was estimated to be 1-in-1 
million and 4-in-1 million, respectively, from volatile HAP being 
emitted from the kilns. The total estimated cancer incidence from 
Portland Cement Manufacturing Industry emission sources based on actual 
emission levels is 0.01 excess cancer cases per year, or one case in 
every 100 years. The total estimated cancer incidence from Portland 
Cement Manufacturing Industry emission sources based on allowable 
emission levels is 0.03 excess cancer cases per year, or one case in 
every 33 years. Emissions of formaldehyde, benzene, naphthalene, and 
acetaldehyde contributed 91 percent to this cancer incidence. The 
population exposed to cancer risks greater than or equal to 1-in-1 
million considering actual emissions was estimated to be approximately 
130; for allowable emissions, approximately 2,300 people were estimated 
to be exposed to cancer risks greater than or equal to 1-in-1 million.

                         Table 3--Inhalation Risk Assessment Summary for Portland Cement Manufacturing Industry Source Category
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Cancer MIR (in-1 million)                                             Population
                                    ----------------------------------------------     Cancer        Population     with risk of
                                                                                      incidence    with risk of 1-     10-in-1     Max chronic noncancer
                                        Based on actual       Based on allowable     (cases per     in-1 million     million or              HI
                                           emissions              emissions           year) \1\    or greater \1\    greater \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category....................  1 (formaldehyde,       4 (formaldehyde,                 0.01             130               0  HI < 1 (Actuals and
                                      benzene).              benzene).                                                              Allowables).
Whole Facility.....................  70 (arsenic and        .....................            0.02          20,000             690  HI = 1 (Actuals).
                                      chromium VI).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Cancer incidence and populations exposed are based upon actual emissions.

    The maximum chronic noncancer HI (TOSHI) values for the source 
category, based on actual and allowable emissions, were estimated to be 
0.02 and 0.06, respectively, with formaldehyde, acetaldehyde, and 
hydrochloric acid driving the TOSHI value.
2. Acute Risk Results
    Worst-case acute HQs were calculated for every HAP for which there 
is an acute health benchmark using actual emissions. The maximum acute 
noncancer HQ value for the source category was less than 1. Acute HQs 
are based upon actual emissions.
3. Multipathway Risk Screening Results
    Results of the worst-case Tier 1 screening analysis indicate that 
PB-HAP emissions (based on estimates of actual emissions) from 70 of 
the 91 facilities in the source category exceed the screening values 
for the carcinogenic PB-HAP (D/F and arsenic) and that PB-HAP emissions 
from 68 of the 91 facilities exceed the screening values for mercury, a 
noncarcinogenic PB-HAP. Cadmium emissions were below the Tier 1 
emission noncancer screening level for each facility based upon the 
combined Farmer and Fisher scenarios. For the PB-HAP and facilities 
that did not screen out at Tier 1, we conducted a Tier 2 screening 
analysis.
    The Tier 2 screen replaces some of the assumptions used in Tier 1 
with site-specific data, the location of fishable lakes, and local wind 
direction and speed. The Tier 2 screen continues to rely on high-end 
assumptions about consumption of local fish and locally grown or raised 
foods (adult female angler at 99th percentile consumption for fish \24\ 
for the Fisher Scenario and 90th percentile for consumption of locally 
grown or raised foods \25\) for the Farmer Scenario and uses an 
assumption that the same individual consumes each of these foods in 
high end quantities (i.e., that an individual has high end ingestion 
rates for each food). The result of this analysis was the development 
of site-specific concentrations of D/F, arsenic compounds, and mercury 
compounds. It is important to note that, even with the inclusion of 
some site-specific information in the Tier 2 analysis, the multipathway 
screening analysis is still

[[Page 44274]]

a very conservative, health-protective assessment (e.g., upper-bound 
consumption of local fish, locally grown, and/or raised foods) and in 
all likelihood will yield results that serve as an upper-bound 
multipathway risk associated with a facility.
---------------------------------------------------------------------------

    \24\ Burger, J. 2002. Daily Consumption of Wild Fish and Game: 
Exposures of High End Recreationists. International Journal of 
Environmental Health Research, 12:343-354.
    \25\ U.S. EPA. Exposure Factors Handbook, 2011 Edition (Final). 
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
---------------------------------------------------------------------------

    Based on the Tier 2 screening analysis, 45 facilities emit D/F and 
arsenic that exceed the Tier 2 cancer screening value. D/F emissions 
exceeded the screening value by a factor of as much as 100 for the 
fisher scenario and by as much as 30 for the farmer scenario. For 
arsenic, the facility with the largest exceedance of the cancer 
screening value had an exceedance of 10 times the Tier 1 emission rate 
level resulting in a Tier 2 screening value less than 1 for both the 
Fisher and Farmer scenarios. For mercury, 24 facilities emit mercury 
emissions above the noncancer screening value, with at least one 
facility exceeding the screening value by a factor of 30 for the Fisher 
scenario. When we considered the effect multiple facilities within the 
source category could have on common lake(s) in the modeling domain, 
mercury emissions exceeded the noncancer screening value by a factor of 
40.
    For D/F, we conducted a Tier 3 multipathway screen for the facility 
with the highest Tier 2 multipathway cancer screen (a value of 100) for 
the Fisher scenario. The next highest facility had a Tier 2 cancer 
screen value of 40. Tier 3 has three individual stages, and we 
progressed through each of those stages until either the facility's PB-
HAP emissions did not exceed the screening value or all three stages 
had been completed. These stages included lake, plume rise, and time-
series assessments. Based on this Tier 3 screening analysis, the MIR 
facility had D/F emissions that exceeded the screening value by a 
factor of 20 for the Fisher scenario. Further details on the Tier 3 
screening analysis can be found in Appendix 11 of Residual Risk 
Assessment for the Portland Cement Manufacturing Industry Source 
Category in Support of the Risk and Technology Review September 2017 
Proposed Rule.''
    An exceedance of a screening value in any of the tiers cannot be 
equated with a risk value or a HQ (or HI). Rather, it represents a 
high-end estimate of what the risk or hazard may be. For example, 
facility emissions exceeding the screening value by a factor 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 exceeding 
the screening value by a factor of 20 for a carcinogen means that we 
are confident that the risk is lower than 20-in-1 million. Our 
confidence comes from the health-protective assumptions that are in 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 that the exposed individual exhibits ingestion behavior that 
would lead to a high total exposure.
    For mercury emissions, we conducted a site-specific assessment. 
Analysis of the facilities with the highest Tier 2 screen values helped 
identify the location for the site-specific assessment and the 
facilitie(s) to model with TRIM_FaTE. We also considered the effect 
multiple facilities within the source category could have on common 
lake(s) in the modeling domain. The selection of the facility(s) for 
the site-specific assessment also included evaluating the number and 
location of lakes impacted, watershed boundaries, and land-use features 
around the target lakes, (i.e., elevation changes, topography, rivers).
    The three facilities selected are located in Midlothian, Texas. One 
of the three facilities had the largest Tier 2 screen value, as well as 
the lake with the highest aggregated noncancer screen value for mercury 
with a lake size of over 6,600 acres. These sites were selected because 
of the Tier 2 mercury screening results and based on the feasibility, 
with respect to the modeling framework, of obtaining parameter values 
for the region surrounding the facilities. We expect that the exposure 
scenarios we assessed are among the highest that might be encountered 
for other facilities in this source category.
    The refined site-specific multipathway assessment, as in the 
screening assessments, includes some hypothetical elements, namely the 
hypothetical human receptor (e.g., the Fisher scenario which did not 
screen out in the screening assessments). We also included children in 
different age ranges and adults with lifetime cancer risks evaluated 
for carcinogens if they did not pass the screening, and noncancer 
hazards evaluated for different age groups for other chemicals that did 
not pass the screening. It is important to note that even though the 
multipathway assessment has been conducted, no data exist to verify the 
existence of the hypothetical human receptor.
    The Fisher scenario involves an individual who regularly consumes 
fish caught in freshwater lakes in the vicinity of the source of 
interest over the course of a 70-year lifetime. Since the Fisher 
scenario did not pass the screening, we evaluated risks and/or hazards 
from the one lake that was fished in the screening assessment, with the 
same adjustments to fish ingestion rates as used in the screening 
according to lake acreage and its assumed impact on fish productivity. 
The refined multipathway assessment produced an HQ of 0.6 for mercury 
for the three facilities assessed. This risk assessment represents the 
maximum hazard for mercury through fish consumption for the source 
category and, with an HQ less than 1, is below the level of concern for 
exposure to emissions from these sources.
    In evaluating the potential for multipathway effects from emissions 
of lead, we compared modeled hourly lead concentrations to the 
secondary NAAQS for lead (0.15 [mu]g/m\3\). The highest hourly lead 
concentration, of 0.023 [micro]g/m\3\, is below the NAAQS for lead, 
indicating a low potential for multipathway impacts of concern due to 
lead.
4. Environmental Risk Screening Results
    As described in section III.A of this preamble, we conducted an 
environmental risk screening assessment for the Portland Cement 
Manufacturing Industry source category for the following six 
pollutants: Mercury (methyl mercury and mercuric chloride), arsenic, 
cadmium, lead, D/F, and HCl. In the Tier 1 screening analysis for PB-
HAP (other than lead, which was evaluated differently), cadmium and 
arsenic emissions had no exceedances of any ecological benchmarks 
evaluated. D/F and methyl mercury emissions had Tier 1 exceedances for 
surface soil. Divalent mercury emissions had Tier 1 exceedances for 
sediment and surface soil. A Tier 2 screening analysis was performed 
for D/F, divalent mercury, and methyl mercury emissions. In the Tier 2 
screening analysis, D/F emissions had no exceedances of any ecological 
benchmarks evaluated. Divalent mercury emissions from six facilities 
exceeded the Tier 2 screen for a threshold level sediment benchmark by 
a maximum screening value of 2. The divalent mercury probable-effects 
benchmark for sediment was not exceeded. Methyl mercury emissions from 
two facilities exceeded the Tier 2 screen for a NOAEL surface soil 
benchmark for avian ground insectivores (woodcock) by a maximum 
screening value of 2. Other surface soil benchmarks for methyl mercury 
were not exceeded. Given the low Tier 2 maximum screening values of 2 
for divalent mercury and methyl mercury, and the fact that only the 
most protective benchmarks were exceeded, a Tier 3 environmental risk 
screen was not conducted for this source category.

[[Page 44275]]

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, 
each individual modeled concentration of HCl (i.e., each off-site data 
point in the modeling domain) was below the ecological benchmarks for 
all facilities. 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
    Results of the assessment of facility-wide emissions indicate that, 
of the 91 facilities, 16 facilities have a facility-wide cancer risk 
greater than or equal to 1-in-1 million (refer to Table 3). The maximum 
facility-wide cancer risk is 70-in-1 million, mainly driven by arsenic 
and chromium (VI) emissions from construction activities involving the 
hauling of sand and gravel from the stone quarrying process. The next 
highest facility-wide cancer risk is 8-in-1 million.
    The total estimated cancer incidence from the whole facility is 
0.02 excess cancer cases per year, or one case in every 50 years. 
Approximately 20,000 people are estimated to have cancer risks greater 
than or equal to 1-in-1 million from exposure to whole facility 
emissions from 16 facilities in the source category. Approximately 700 
people are estimated to have cancer risk greater than 10-in-1 million 
from exposure to whole facility emissions from one facility in the 
source category.
    The maximum facility-wide chronic non-cancer TOSHI is estimated to 
be equal to 1, mainly driven by emissions of HCl from a drying 
operation routed through the long kiln.
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 of the population close to the facilities. In this 
analysis, we evaluated the distribution of HAP-related cancer and non-
cancer risks from the Portland Cement Manufacturing Industry source 
category across different demographic groups within the populations 
living near facilities identified as having the highest risks. The 
methodology and the results of the demographic analyses are included in 
a technical report, Risk and Technology Review--Analysis of Demographic 
Factors for Populations Living Near Portland Cement Manufacturing 
Facilities, available in the docket for this action.
    The results of the demographic analysis are summarized in Table 4 
below. These results, for various demographic groups, are based on the 
estimated risks from actual emission levels for the population living 
within 50 km of the facilities.

        Table 4--Portland Cement Manufacturing Industry Source Category Demographic Risk Analysis Results
----------------------------------------------------------------------------------------------------------------
                                                                             Population with    Population with
                                                                            cancer risk at or    chronic hazard
                                                                               above 1-in-1    index above 1 due
                                                             Nationwide       million due to      to Portland
                                                                             Portland Cement         Cement
                                                                              Manufacturing      Manufacturing
----------------------------------------------------------------------------------------------------------------
Total Population.......................................        317,746,049                134                  0
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White..................................................                 62                 71                  0
All Other Races........................................                 38                 29                  0
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White..................................................                 62                 94                  0
African American.......................................                 12                  1                  0
Native American........................................                0.8                1.6                  0
Other and Multiracial..................................                  7                  3                  0
----------------------------------------------------------------------------------------------------------------
                                              Ethnicity by Percent
----------------------------------------------------------------------------------------------------------------
Hispanic...............................................                 18                 24                  0
Non-Hispanic...........................................                 82                 76                  0
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level....................................                 14                 10                  0
Above Poverty Level....................................                 86                 90                  0
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without High School Diploma................                 14                 11                  0
Over 25 and with a High School Diploma.................                 86                 89                  0
----------------------------------------------------------------------------------------------------------------

    The results of the Portland Cement Manufacturing Industry source 
category demographic analysis indicate that emissions from the source 
category expose approximately 130 people to a cancer risk at or above 
1-in-1 million and no people to a chronic noncancer TOSHI greater than 
1. The percentages of the at-risk population in each demographic group 
(except for White, Native American, and Hispanic) are similar to or 
lower than their respective nationwide percentages. The specific 
demographic results indicate that the percentage of the population 
potentially impacted by Portland cement emissions is greater than its 
corresponding nationwide percentage for the following

[[Page 44276]]

demographics: Native American (1.6 percent compared to 0.8 percent 
nationally), Hispanic or Latino (24 percent compared to 18 percent 
nationally) and children aged 0 to 17 (32 percent compared to 23 
percent nationally). The other demographic groups within the exposed 
population were the same or lower than the corresponding nationwide 
percentages.

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

1. Risk Acceptability
    As noted in section II.A.1 of this preamble, the EPA sets standards 
under 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 
lifetime [cancer] risk (MIR) \26\ of approximately 1-in-10 thousand 
[i.e., 100-in-1 million].'' 54 FR 38045, September 14, 1989. In this 
proposal, we estimated risks based on actual and allowable emissions. 
As discussed earlier, we consider our analysis of risk from allowable 
emissions to be conservative and, as such, to represent an upper bound 
estimate of inhalation risk from emissions allowed under the NESHAP for 
the source category.
---------------------------------------------------------------------------

    \26\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk were an individual exposed to the maximum level 
of a pollutant for a lifetime.
---------------------------------------------------------------------------

    The inhalation cancer risk to the individual most exposed to 
emissions from sources in the Portland Cement Manufacturing Industry 
source category is 1-in-1 million based on actual emissions. The 
estimated incidence of cancer due to inhalation exposure is 0.01 excess 
cancer cases per year, or one case in every 100 years, based on actual 
emissions. Approximately 130 people are exposed to actual emissions 
resulting in an increased cancer risk greater than or equal to 1-in-1 
million. We estimate that, for allowable emissions, the inhalation 
cancer risk to the individual most exposed to emissions from sources in 
this source category is up to 4-in-1 million. The estimated incidence 
of cancer due to inhalation exposure is 0.02 excess cancer cases per 
year, or one case in every 50 years, based on allowable emissions. 
Based on allowable emissions, approximately 20,000 people could be 
exposed to emissions resulting in an increased cancer risk of up to 1-
in-1 million, and about 690 people to an increased cancer risk of up to 
10-in-1 million.
    The Agency estimates that the maximum chronic noncancer TOSHI from 
inhalation exposure is less than 1 due to actual emissions, and up to 1 
due to allowable emissions. The screening assessment of worst-case 
acute inhalation impacts from worst-case 1-hour emissions indicates 
that no HAP exceed an HQ value of 1.
    Based on the results of the multipathway cancer screening analyses 
of arsenic and dioxin emissions, we conclude that the cancer risk from 
ingestion exposure to the individual most exposed is less than 1-in-1 
million for arsenic and, based on a Tier 3 analysis, less than 20-in-1 
million for dioxins. Based on the Tier 1 multipathway screening 
analysis of cadmium emissions and the refined site-specific 
multipathway analysis of mercury emissions, the maximum chronic 
noncancer TOSHI due to inhalation exposures is less than 1 for actual 
emissions.
    In determining whether risk is acceptable, the EPA considered all 
available health information and risk estimation uncertainty, as 
described above. The results indicate that both the actual and 
allowable inhalation cancer risks to the individual most exposed are 
significantly less than 100-in-1 million, which is the presumptive 
limit of acceptability. The maximum chronic noncancer TOSHI due to 
inhalation exposures is less than 1 due to actual emissions and up to 1 
due to allowable emissions, and our refined multipathway analysis 
indicates that noncancer ingestion risks also are less than 1. Finally, 
the evaluation of acute noncancer risks was very conservative and 
showed that acute risks are below a level of concern.
    Taking into account this information, we propose that the risk 
remaining after implementation of the existing MACT standards for the 
Portland Cement Manufacturing Industry is acceptable.
2. Ample Margin of Safety Analysis
    Although we are proposing that the risks from the Portland Cement 
Manufacturing Industry source category are acceptable, for allowable 
emissions, the inhalation cancer risk to the individual most exposed to 
emissions from sources in this source category is up to 4-in-1 million, 
with approximately 2,000 individuals estimated to be exposed to 
emissions resulting in an increased cancer risk of 1-in-1 million or 
greater. In addition, based on the Tier 3 multipathway screening 
analysis, dioxin emissions from the MIR facility could pose a risk of 
up to 20-in-1 million. Thus, we considered whether the existing MACT 
standards provide an ample margin of safety to protect public health. 
In addition to considering all of the health risks and other health 
information considered in the risk acceptability determination, in the 
ample margin of safety analysis, we evaluated the cost and feasibility 
of available control technologies and other measures (including the 
controls, measures, and costs reviewed under the technology review) 
that could be applied in this source category to further reduce the 
risks due to emissions of HAP.
    Our inhalation risk analysis indicates very low potential for risk 
from the facilities in the source category based upon actual emissions 
at 1-in-1 million, and just slightly higher risks based upon allowable 
emissions at 4-in-1 million. Therefore, very little reduction in 
inhalation risks could be realized regardless of the availability of 
control options. As directed by CAA section 112(f)(2), we conducted an 
analysis to determine if the standard provides an ample margin of 
safety to protect public health. The HAP risk drivers contributing to 
the inhalation MIR in excess of 1-in-1 million for 40 CFR part 63, 
subpart LLL facilities include primarily the gaseous organic HAP: 
Formaldehyde, benzene, naphthalene, and acetaldehyde. More than 62 
percent of the mass emissions of these compounds originate from kiln 
operations.
    The following paragraphs provide our analyses of HAP-reducing 
measures that we considered in our ample margin of safety analysis. For 
each option, we considered feasibility, cost-effectiveness, and health 
information in determining whether to revise standards in order to 
provide an ample margin of safety.
    The first technology we evaluated in our ample margin of safety 
analysis is a regenerative thermal oxidizer (RTO). To assess the costs 
associated with RTOs, we relied on our beyond-the-floor (BTF) analysis 
documented in the May 6, 2009, Portland Cement NESHAP proposal (74 FR 
21136). In that proposal, we assessed the potential for further 
reductions in THC and organic HAP emissions beyond the reductions 
achieved by activated carbon injection (ACI) (controlling mercury and 
THC emissions), the typical kiln controls used in the industry. To 
achieve further reductions in THC, a kiln would likely require 
additional controls, such as RTO. It was expected that RTO would only 
offer an additional 50-percent removal efficiency, due to the reduced

[[Page 44277]]

THC concentration leaving the ACI control device and entering the 
proposed RTO. The analysis indicates that addition of an RTO would 
reduce THC emissions by approximately 9 tpy, for a cost effectiveness 
of $411,000/ton. The HAP fraction would be approximately 24 percent of 
THC, so 2 tpy of organic HAP would be removed, at a cost effectiveness 
of $1.7 million/ton of organic HAP. The details of this analysis are 
included in 74 FR 21152-21153. Overall, we do not consider the use of 
an RTO to be cost effective for this industry, and given the small 
reduction in organic HAP emissions, the addition of an RTO would have 
little effect on the source category risks.
    Exposure to dioxin emissions from the MIR facility were found to 
pose a non-inhalation MIR of less than 20-in-1 million, and possibly 
greater than 1-in-1 million. Technologies evaluated included the use of 
ACI with wet scrubbers to help control D/F emissions. For the March 24, 
1998, proposal (63 FR 14182), we performed a BTF analysis that 
considered the MACT floor for D/F emissions controls to be a reduction 
of the kiln exhaust gas stream temperature at the PM control device 
inlet to 400 degrees Fahrenheit (63 FR 14200). An ACI system was 
considered as a potential BTF option. Total annual costs were estimated 
to be $426,000 to $3.3 million per kiln. The Agency determined that, 
based on the additional costs and the level of D/F emissions reduction 
achievable, the BTF costs were not justified (63 FR 14199-14201). We do 
not consider the use of ACI system to be cost effective for the 
industry to use to reduce D/F emissions, and would have little effect 
on the source category risks.
    Our multipathway screening analysis results did not necessarily 
indicate any risks from mercury emissions, but we have also performed 
an evaluation of mercury emissions controls. In the May 6, 2009, BTF 
analysis, it was estimated for a typical 1.2 million tpy kiln, the 
addition of a halogenated carbon injection system would result in a 3.0 
lb/year reduction in mercury at a cost of $1.25 million/year and a cost 
effectiveness of $420,000/lb of mercury removed. If the halogenated 
carbon injection system effectiveness is reduced due to a low level of 
mercury entering the system, 2.3 lb/year of mercury would be removed at 
a cost effectiveness of $540,000/lb of mercury removed (74 FR 21149). 
We do not consider the use of halogenated carbon injection system to be 
cost effective for the industry to use to reduce mercury emissions, and 
would have little effect on the low risks identified for this source 
category.
    The cost-effectiveness values for further reduction of organic HAP, 
as referenced herein, are significantly higher than values in other 
NESHAP we have historically rejected for not being cost effective for 
organic HAP. As examples of determinations made historically, refer to 
the National Emission Standards for Hazardous Air Pollutants Residual 
Risk and Technology Review for Flexible Polyurethane Foam Production 
(August 15, 2014, 79 FR 48078), the National Emission Standards for 
Hazardous Air Pollutant Emissions: Group I Polymers and Resins (April 
21, 2011, 77 FR 22579), and the National Emission Standards for Organic 
Hazardous Air Pollutants from the Synthetic Organic Chemical 
Manufacturing Industry (December 21, 2006, 71 FR 76605). We also 
determined that further reduction of dioxin emissions would not be cost 
effective. Due to the low level of current risk, the minimal risk 
reductions that could be achieved with the various control options that 
we evaluated, and the substantial costs associated with additional 
control options, we are proposing that the current standards provide an 
ample margin of safety.
3. Adverse Environmental Effects
    Based on the results of our environmental risk screening 
assessment, we conclude that there is not an adverse environmental 
effect from the Portland Cement Manufacturing Industry source category. 
We are 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.

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

    Control devices typically used to minimize emissions at Portland 
cement manufacturing industry facilities include fabric filters and 
electrostatic precipitators (ESP) for control of PM from kilns; fabric 
filters for the control of PM from clinker coolers and raw material 
handling operations; wet scrubbers or dry lime injection for control of 
HCl, and ACI, wet scrubbers, or both for the control of mercury, D/F, 
and THC. At least one kiln has controlled THC using a wet scrubber 
followed by an RTO. Process changes used at some facilities to reduce 
HAP emissions include dust shuttling to reduce mercury emissions and 
raw material substitution to reduce organic HAP emissions. The add-on 
controls and process changes used by a facility to comply with the 40 
CFR part 63, subpart LLL emission standards are highly site specific 
because of factors such as variations in the HAP content of raw 
materials and fuels, availability of alternative raw materials and 
fuels, and kiln characteristics (such as age and type of kiln). In 
addition, new or reconstructed kilns must also comply with the New 
Source Performance Standards (NSPS) for Cement Manufacturing (40 CFR 
part 60, subpart F). The NSPS sets limits for emissions of PM, nitrogen 
oxides (NO<INF>X</INF>) and sulfur dioxide (SO<INF>2</INF>). The PM 
limits in the NSPS and the subpart LLL PM limits for new sources are 
the same. Measures taken at a facility to comply with the 
NO<INF>X</INF> and SO<INF>2</INF> limits must be considered in light of 
the subpart LLL emission standards. Due to the relatively recent 
finalization of the MACT rules for Portland cement manufacturing, there 
have been no new developments in practices, processes, or control 
technologies that have been implemented in this source category since 
promulgation of the current NESHAP. Nevertheless, we did review several 
technologies that have been available, or may be available soon, to the 
industry and provided additional options to the industry for reducing 
HAP emissions. Based on information available to the EPA, these 
technologies do not clearly reduce HAP emissions relative to 
technologies that were considered by the EPA when promulgating the 
Portland Cement Manufacturing Industry NESHAP in 2013.
    Selective catalytic reduction (SCR) is the process of adding 
ammonia or urea in the presence of a catalyst to selectively reduce 
NO<INF>X</INF> emissions from exhaust gases. A benefit of SCR may be 
its ability to facilitate the removal of mercury and other HAP 
emissions from the Portland cement manufacturing process. The EPA 
considered SCR in proposing standards for NO<INF>X</INF> in 2008, but 
did not propose SCR as best demonstrated technology for several reasons 
(73 FR 34072, June 16, 2008). At the time of the proposal, SCR was in 
use at just a few kilns in Europe, and no cement kilns in the U.S. used 
SCR. There were concerns over the plugging of the SCR catalyst in high-
dust installations and, in low-dust installations where the catalyst is 
located downstream of the PM control device, the cost of reheating 
cooled exhaust was very high leading to uncertainties over what actual 
costs would be. Finally, SCR was anticipated to increase energy use due 
to the

[[Page 44278]]

pressure drop across the catalyst and produce additional liquid and 
solid waste to be handled.
    Since then, SCR has been installed on two cement kilns in the U.S. 
The two installations in the U.S. started operation in 2016 (Holcim in 
Midlothian, Texas) and 2013 (Lafarge in Joppa, Illinois). Holcim 
controls THC through addition of SCR to Kiln 1 and an RTO to Kiln 2. 
The SCR system at Lafarge controls NO<INF>X</INF> and operates with a 
long dry kiln with a hot ESP, and no reheat.
    Beyond its ability to reduce NO<INF>X</INF> by 90 percent, 
multipollutant benefits have been reported. At kilns in Europe, 
reductions in THC of 50 to greater than 70 percent have been reported. 
Although D/F reductions have been observed for SCR in many industries 
and reductions in D/F have been reported for an SCR installation at a 
cement kiln in Italy, tests of D/F reduction across SCR catalyst in the 
Portland Cement Manufacturing Industry have not been conducted. SCR 
does not directly reduce mercury emissions. Instead, SCR results in the 
oxidation of mercury from its elemental form, and the oxidized form is 
more easily captured in scrubbers. The addition of an SCR as control is 
expected to have little impact on reducing mercury emissions from 
cement kilns without requiring the addition of a scrubber system.
    Catalytic ceramic filter candles and catalytic filter bags are used 
to remove not only particulate, but may be used to remove other 
pollutants such as D/F, THC, non-D/F organic HAP, carbon monoxide (CO), 
and NO<INF>X</INF>. Catalytic ceramic filter candles are typically 
approximately 10 feet long. The length is limited to 10 feet by several 
considerations, including the weight of the candle and the fact that 
the candle cannot be flexed, limiting the height above the seal plate. 
In contrast, the length of catalytic filter bags can vary from 10 to 32 
feet. Currently, filter bags at cement manufacturing facilities are 
much longer than 10 feet. Therefore, installing ceramic filter candles 
can only be done by replacing the baghouse housing (i.e., ceramic 
filter candles are not a drop-in replacement for existing filter bags).
    FLSmidth received the first contract for removal of THC with 
ceramic catalytic filters at a U.S. cement kiln. They noted that the 
removal of THC with their ceramic catalytic filter system depends on 
the speciation of THC components, but that removal efficiencies of 
greater than 90 percent have been seen in testing for HAP THC 
pollutants. Tri-Mer Corp., a technology company specializing in 
advanced industrial air pollution control systems, claims to have fully 
commercialized a ceramic filter technology that is highly effective for 
emissions from cement kilns and other processes facing NESHAP and MACT 
compliance issues. Although no studies were identified in the 
literature documenting the performance of Tri-Mer's ceramic filter 
system, the company states that their catalyst filter system is highly 
efficient at removing PM, SO<INF>2</INF>, HCl, mercury, and heavy 
metals, while simultaneously destroying NO<INF>X</INF>, cement organic 
HAP and D/F. Tri-Mer reports NO<INF>X</INF> removal at up to 95 percent 
and D/F removal typically over 97 percent. The system can incorporate 
dry sorbent injection of hydrated lime, sodium bicarbonate, or trona 
for dry scrubbing of SO<INF>2</INF>, HCI, HF, and other acid gases. 
With dry sorbent injection, typical SO<INF>2</INF> and HCl results show 
90- to 98-percent removal. According to company information, the 
control of any combination of these pollutants is accomplished in a 
single, completely dry system that is suitable for all flow volumes.
    Powdered activated carbon (PAC) for mercury control was first used 
in the U.S. for the incinerator (waste-to-energy) industry. 
Conventional PAC was expected to be used for mercury control for 
electrical power generation. However, conventional PAC mercury removal 
performance suffers in situations involving high-sulfur coal, which 
leads to high sulfur trioxide (SO<INF>3</INF>) levels, or situations 
where SO<INF>3</INF> is injected to improve ESP performance. In 
addition, a September 2007 test conducted at the Ash Grove facility in 
Durkee, Oregon, suggests that halogen-treated PAC makes no difference 
in controlling mercury emissions from a kiln. Specifically, the report 
states, ``While studies at coal-fired power plants have indicated that 
the use of halogen-treated PAC can result in higher Hg control 
efficiencies, testing on the Durkee exhaust gas indicated that 
untreated carbon provides equivalent control to halogen-treated carbon. 
This is believed to be due to the low sulfur levels in the Durkee 
cement kiln exhaust gases as compared to coal-fired power plants.'' 
\27\ We believe that, based on our review, the addition of halogenated 
PAC controls to further reduce mercury emissions do not result in a 
substantial reduction of mercury emissions beyond current controls.
---------------------------------------------------------------------------

    \27\ Mercury Control Slipstream Baghouse Testing at Ash Grove's 
Durkee Cement Facility, September 2007.
---------------------------------------------------------------------------

    The Ash Grove facility in Durkee, Oregon, had the highest mercury 
emissions of any Portland cement manufacturing facility prior to 
promulgation of the cement NESHAP. To reach the NESHAP limit of 55 lbs 
mercury per million tons of clinker, Ash Grove installed a $20 million 
system for mercury capture. It consists of a baghouse with ACI. Dust 
collected in the baghouse is sent to an electric furnace where it is 
heated to 800 degrees Fahrenheit, which puts the mercury back into a 
gaseous state. The gaseous mercury moves into a cooling chamber where 
it is converted into liquid that is captured in a heat exchanger/
condenser. The liquid mercury is then sold for use in electronic 
devices and other products.
    Praxair has developed a technology of feeding a stream of hot 
oxygen into a cement kiln to lower emissions of CO and hydrocarbons. 
This technology involves oxidation of CO at the kiln inlet with oxygen 
enhanced combustion, and has been in commercial practice since 2014 at 
a kiln in Europe. It has not been installed on any cement kiln in the 
U.S. Oxygen is injected in the riser with the goal of lowering 
NO<INF>X</INF> and CO emissions to below permitted levels of 230 
milligrams per normal cubic meter (mg/Nm\3\) and 4,000 mg/Nm\3\, 
respectively, without use of a more expensive SCR system.
    As discussed before, there are several technologies that can be 
effective in reducing emission from the cement kiln. However, most of 
these technologies have not been widely used in the industry so source 
category specific data on their long term performance and costs are 
lacking. Their performance is typically similar to technologies already 
employed or, in some cases, only marginally better. In the case of SCR, 
it had been noted that this might be an alternative to current THC 
controls. However, we note that SCR is most effective on non-dioxin 
organic HAP and is not effective on other hydrocarbons. The organic HAP 
portion of the 24 parts per million by volume THC limit is typically 
low and is near the actual detection limits for measurement. Therefore, 
even if SCR were more widely applied in the industry, the emissions 
impact on THC and organic HAP would be small.

D. What other actions are we proposing?

    In addition to the proposed actions described above, we are 
proposing additional revisions, which include changes to clarify 
monitoring, testing, and recordkeeping and reporting requirements and 
the correction of typographical errors. Our analyses and

[[Page 44279]]

proposed changes related to these issues are discussed below.
    We are proposing to correct a paragraph in the reporting 
requirements that mistakenly requires that affected sources report 
their 30-operating day rolling average for D/F temperature monitoring. 
There are no 30-day operating rolling average temperature requirements 
pertaining to D/F in the rule. The removal of the reference to the D/F 
temperature monitoring system in 40 CFR 63.1354(b)(9)(vi) is also 
consistent with the EPA's October 2016 rule guidance for the subpart 
LLL NESHAP. See NESHAP for the Portland Cement Manufacturing Industry 
Subpart LLL Rule Guidance, which has been updated to include revisions 
from this proposed rule. (https://www.epa.gov/sites/production/files/2016-03/documents/ruleguidance_mar2016.pdf.)
    We are proposing to correct a provision that requires facility 
owners or operators to keep records of both daily clinker production 
and kiln feed rates. Section 63.1350(d)(1)(ii) requires daily kiln feed 
rate records only if the facility derives their clinker production 
rates from the measured feed rate.
    The EPA is proposing to clarify that the submittal dates for 
semiannual summary reports required under 40 CFR 63.1354(b)(9) are 60 
days after the end of the reporting period consistent with the Agency's 
statement in the October 2016 rule guidance for the subpart LLL NESHAP. 
In addition, the October 2016 rule guidance was revised in September 
2017 to ensure it reflects the various changes proposed in this rule.
    The EPA is proposing to resolve conflicting provisions that apply 
when an SO<INF>2</INF> continuous parametric monitoring system is used 
to monitor HCl compliance. If the SO<INF>2</INF> level exceeds by 10 
percent or more the site-specific SO<INF>2</INF> emissions limit, 40 
CFR 63.1349(b)(x) requires that as soon as possible, but within 30 
days, a facility must take corrective action, and within 90 days, 
conduct a performance test to demonstrate compliance with the HCl limit 
and verify or re-establish the site-specific SO<INF>2</INF> emissions 
limit. These conflict with 40 CFR 63.1350(l)(3), which requires 
corrective action within 48 hours and retesting within 60 days. We are 
proposing to adopt the requirements of 40 CFR 63.1349(b)(x) and change 
the requirement of 40 CFR 63.1350(l)(3) to reflect this.
    We are proposing to clarify the requirement in section 
63.1349(b)(1)(vi) which states that for each PM performance test, an 
owner or operator must conduct at least three separate test runs each 
while the mill is on and the mill is off. We are proposing that this 
provision only applies to kilns with inline raw mills, as inline raw 
mills are considered part of the kiln and can affect kiln PM emissions. 
It specifically would not apply to a kiln that does not have an inline 
raw mill or to a clinker cooler (unless the clinker cooler gases are 
combined with kiln exhaust and sent through an inline mill). As in 
these cases, the raw mill is a separate source from the kiln and has no 
effect on kiln or clinker cooler PM emissions.
    We are proposing changes which affect the emission limits for D/F. 
Table 1 of 40 CFR 63.1343(b) lists the emission limits for D/F. The 
units of the emission limit are ng/dscm TEQ at 7-percent oxygen. The 
TEQ is developed by determining the mass of each congener measured 
during the performance test, then multiplying each congener by the 
toxic equivalency factor (TEF). After the TEQ is developed per 
congener, they are added to obtain the total TEQs. The TEFs were re-
evaluated in 2005 by the World Health Organization--International 
Programme on Chemical Safety using a different scale of magnitude.\28\ 
The 40 CFR part 63, subpart LLL standards were developed based on TEFs 
developed in 1989, as referenced in the TEQ definition section of the 
rule (40 CFR 63.1341). Laboratories calculating the TEQs should be 
using the TEFs developed in 1989. We are proposing that the 1989 TEFs 
be incorporated into the rule to clarify that they are the appropriate 
factors for calculating TEQ.
---------------------------------------------------------------------------

    \28\ Van den Berg, Martin, et al. The 2005 World Health 
Organization Re-evaluation of Human and Mammalian Toxic Equivalency 
Factors for Dioxins and Dioxin-like Compounds. Toxicol. Sci. 2006, 
October 1993(2): 223-241.
---------------------------------------------------------------------------

    Finally, we are proposing to clarify the performance test 
requirements for certain sources. According to a stakeholder, 
compliance with 40 CFR part 63, subpart LLL is required immediately 
upon startup and does not allow companies an operating window after 
periods of extended shutdown in order to assess compliance. The 
stakeholder states that extended shutdowns of existing kilns occur in 
the Portland cement manufacturing industry in the aftermath of economic 
downturns when companies have halted production at certain facilities. 
When the economy rebounds and sources are brought back on line, they 
must immediately comply with NESHAP and other CAA requirements for 
existing facilities. The stakeholder asserts that this mandatory 
compliance requirement does not account for the fact that owners or 
operators must start the facilities back up and run them for periods of 
time to determine whether any measures must be taken to come into 
compliance with updated NESHAP or other standards. In response, we are 
proposing to clarify the performance test requirements for affected 
sources that have been idle through one or more periods that required a 
performance test to demonstrate compliance. The proposed amendment 
would require any affected source that was unable to demonstrate 
compliance before the compliance date due to being idled, or that had 
demonstrated compliance, but was idled during the normal window for the 
next compliance test, to demonstrate compliance with the emissions 
standards and operating limits by conducting their performance using 
the test methods and procedures in 40 CFR 63.1349 and 63.7. Per 40 CFR 
63.7, the necessary performance tests would need to be completed within 
180 days of the date that compliance must be demonstrated.

E. What compliance dates are we proposing?

    Because these amendments only provide corrections and 
clarifications to the current rule and do not impose new requirements 
on the industry, we are proposing that these amendments become 
effective upon promulgation of the final rule.

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the impacts to affected sources?

    The recent amendments to the Portland Cement Manufacturing NESHAP 
have included rule updates, addressing electronic reporting 
requirements, and changes in policies regarding startup, shutdown, and 
malfunction. Because we are proposing no new requirements or controls 
in this RTR, no Portland cement manufacturing facilities are adversely 
impacted by these proposed revisions. In fact, the impacts to the 
Portland cement manufacturing industry from this proposal will be 
minimal and potentially positive.

B. What are the air quality impacts?

    In this proposal, we recommend no new emission limits and require 
no additional controls; therefore, no air quality impacts are expected 
as a result of the proposed amendments.

C. What are the cost impacts?

    As previously stated, recent amendments to the Portland Cement 
Manufacturing NESHAP have addressed electronic reporting and changes in 
policies regarding startup, shutdown, and malfunction. Additionally, 
the

[[Page 44280]]

proposed amendments recommend no changes to emission standards or add-
on controls. Therefore, the proposed amendments impose no additional 
costs. In fact, the clarifications to rule language may actually result 
in a reduction of current costs because compliance will be more 
straightforward.

D. What are the economic impacts?

    No economic impacts are expected as a result of the proposed 
amendments.

E. What are the benefits?

    While the proposed amendments would not result in reductions in 
emissions of HAP, this action, if finalized, would result in improved 
monitoring, compliance, and implementation of the rule.

VI. Request for Comments

    We solicit comments on all aspects of 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 Web site at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html. 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 Web site, 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, etc.).
    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-2016-0442 (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. 
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 RTR Web 
site at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.

VIII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at http://www2.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 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 the Office of Management and Budget (OMB) 
for review.

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)

    This action does not impose any new information collection burden 
under the PRA. OMB has previously approved the information collection 
activities contained in the existing regulations (40 CFR part 63, 
subpart LLL) and has assigned OMB control number 2060-0416. This action 
does not change the information collection requirements.

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. In 
making this determination, the impact of concern is any significant 
adverse economic impact on small entities. An agency may certify that a 
rule will not have a significant economic impact on a substantial 
number of small entities if the rule relieves regulatory burden, has no 
net burden, or otherwise has a positive economic effect on the small 
entities subject to the rule. We estimate that three of the 26 existing 
Portland cement entities are small entities and comprise three plants. 
After considering the economic impacts of this proposed action on small 
entities, we have concluded that this action will have no net 
regulatory burden for all directly regulated small entities.

E. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate 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. It will neither impose substantial direct 
compliance costs on federally recognized tribal governments, nor 
preempt tribal law. The EPA is aware of one tribally owned Portland 
cement facility currently subject to 40 CFR part 63, subpart LLL that 
will be subject to this proposed action. However, the provisions of 
this proposed rule are not expected to impose new or substantial direct 
compliance costs on tribal governments since the provisions in this 
proposed action are clarifying and correcting monitoring and testing 
requirements and recordkeeping and reporting requirements. This 
proposed action also provides clarification for owners and operators on 
bringing new or previously furloughed kilns back on line. Thus, 
Executive Order 13175 does not apply to this action.

[[Page 44281]]

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

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive Order. This action is not subject to 
Executive Order 13045 because it does not concern an environmental 
health risk or safety risk.

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 rulemaking does not involve technical standards.

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.A of this 
preamble.

List of Subjects in 40 CFR Part 63

    Environmental protection, Administrative practices and procedures, 
Air pollution control, Hazardous substances, Intergovernmental 
relations, Reporting and recordkeeping requirements.

    Dated: September 1, 2017.
E. Scott Pruitt,
Administrator.

    For the reasons stated in the preamble, the Environmental 
Protection Agency is proposing to amend title 40, chapter I, part 63 of 
the Code of Federal Regulations (CFR) as follows:

PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS 
FOR SOURCE CATEGORIES

0
1. The authority citation for part 63 continues to read as follows:

    Authority: 42 U.S.C. 7401 et seq.

Subpart LLL--National Emission Standards for Hazardous Air 
Pollutants for the Portland Cement Manufacturing Industry

0
2. Section 63.1341 is amended by:
0
a. Removing the definition of ``affirmative defense;'' and
0
b. Revising the definitions of ``dioxins and furans (D/F),'' ``in-line 
coal mill,'' and ``TEQ.''
    The revisions read as follows:


Sec.  63.1341  Definitions

* * * * *
    Dioxins and furans (D/F) means tetra-, penta-, hexa-, hepta-, and 
octa-chlorinated dibenzo dioxins and furans.
* * * * *
    In-line coal mill means a coal mill using kiln exhaust gases in 
their process. A coal mill with a heat source other than the kiln or a 
coal mill using exhaust gases from the clinker cooler is not an in-line 
coal mill.
* * * * *
    TEQ means the international method of expressing toxicity 
equivalents for dioxins and furans as defined in U.S. EPA, Interim 
Procedures for Estimating Risks Associated with Exposures to Mixtures 
of Chlorinated Dibenzo-p-dioxins and -dibenzofurans (CDDs and CDFs) and 
1989 Update, March 1989. The 1989 Toxic Equivalency Factors (TEFs) used 
to determine the dioxin and furan TEQs are listed in Table 2 to subpart 
LLL of Part 63.
* * * * *


Sec.  63.1343  [Amended]

0
3. Section 63.1343 is amended by removing paragraph (d) and Table 2.
0
4. Section 63.1348 is amended by:
0
a. Revising the first sentence in paragraph (a) introductory text;
0
b. Revising paragraph (a)(3)(i);
0
c. Revising the second sentence in paragraph (a)(3)(iv);
0
d. Revising paragraphs (a)(4)(ii), (a)(7)(ii), (b)(3)(ii), and (b)(4);
0
e. Redesignating paragraph (b)(5)(i) as paragraph (b)(5) introductory 
text;
0
f. Revising newly redesignated paragraph (b)(5) introductory text; and
0
g. Adding new paragraph (b)(5)(i).
    The revisions and addition read as follows:


Sec.  63.1348  Compliance requirements.

    (a) Initial Performance Test Requirements. For an affected source 
subject to this subpart, including any affected source that was unable 
to demonstrate compliance before the compliance date due to being 
idled, or that had demonstrated compliance but was idled during the 
normal window for the next compliance test, you must demonstrate 
compliance with the emissions standards and operating limits by using 
the test methods and procedures in Sec. Sec.  63.1349 and 63.7.
* * * * *
    (3) D/F compliance. (i) If you are subject to limitations on D/F 
emissions under Sec.  63.1343(b), you must demonstrate initial 
compliance with the D/F emissions standards by using the performance 
test methods and procedures in Sec.  63.1349(b)(3). The owner or 
operator of a kiln with an in-line raw mill must demonstrate initial 
compliance by conducting separate performance tests while the raw mill 
is operating and the raw mill is not operating. Determine the D/F TEQ 
concentration for each run and calculate the arithmetic average of the 
TEQ concentrations measured for the three runs to determine continuous 
compliance.
* * * * *
    (iv) * * * Compliance is demonstrated if the system is maintained 
within <plus-minus>5 percent accuracy during the performance test 
determined in accordance with the procedures and criteria submitted for 
review in your monitoring plan required in Sec.  63.1350(p).
    (4) * * *
    (ii) Total Organic HAP Emissions Tests. If you elect to demonstrate 
compliance with the total organic HAP emissions limit under Sec.  
63.1343(b) in lieu of the THC emissions limit, you must demonstrate 
compliance with the total organic HAP emissions standards by using the 
performance test methods and procedures in Sec.  63.1349(b)(7).
* * * * *
    (7) * * *
    (ii) Perform required emission monitoring and testing of the kiln 
exhaust prior to the reintroduction of the coal mill exhaust, and also 
testing the kiln exhaust diverted to the coal mill. All emissions must 
be added together for all emission points, and must not exceed the 
limit per each pollutant as listed in Sec.  63.1343(b).
    (b) * * *
    (3) * * *
    (ii) Bag Leak Detection System (BLDS). If you install a BLDS on a 
raw mill or finish mill in lieu of conducting the daily visible 
emissions testing, you must demonstrate compliance using a BLDS that is 
installed, operated, and maintained in accordance with the requirements 
of Sec.  63.1350(f)(4)(ii).
    (4) D/F Compliance. If you are subject to a D/F emissions 
limitation under Sec.  63.1343(b), you must demonstrate

[[Page 44282]]

compliance using a continuous monitoring system (CMS) that is 
installed, operated and maintained to record the temperature of 
specified gas streams in accordance with the requirements of Sec.  
63.1350(g).
    (5) Activated Carbon Injection Compliance. (i) If you use activated 
carbon injection to comply with the D/F emissions limitation under 
Sec.  63.1343(b), you must demonstrate compliance using a CMS that is 
installed, operated, and maintained to record the rate of activated 
carbon injection in accordance with the requirements Sec.  
63.1350(h)(1).
* * * * *
0
5. Section 63.1349 is amended by:
0
a. Revising paragraphs (b)(1)(vi), (3)(iv), (4)(i), (6)(i)(A), 
(7)(viii)(A), (8)(vi), and (8)(vii)(B); and
0
b. Removing and reserving paragraph (d).
    The revisions read as follows:


Sec.  63.1349  Performance testing requirements.

* * * * *
    (b)(1) * * *
    (vi) For each performance test, conduct at least three separate 
test runs under the conditions that exist when the affected source is 
operating at the level reasonably expected to occur. Conduct each test 
run to collect a minimum sample volume of 2 dscm for determining 
compliance with a new source limit and 1 dscm for determining 
compliance with an existing source limit. Calculate the time weighted 
average of the results from three consecutive runs, including 
applicable sources as required by paragraph (b)(1)(viii) of this 
section, to determine compliance. You need not determine the 
particulate matter collected in the impingers ``back half'' of the 
Method 5 or Method 5I particulate sampling train to demonstrate 
compliance with the PM standards of this subpart. This shall not 
preclude the permitting authority from requiring a determination of the 
``back half'' for other purposes. For kilns with inline raw mills, 
testing must be conducted while the raw mill is on and while the raw 
mill is off. If the exhaust streams of a kiln with an inline raw mill 
and a clinker cooler are comingled, then the comingled exhaust stream 
must be tested with the raw mill on and the raw mill off.
* * * * *
    (3) * * *
    (iv) The run average temperature must be calculated for each run, 
and the average of the run average temperatures must be determined and 
included in the performance test report and will determine the 
applicable temperature limit in accordance with Sec.  63.1346(b).
* * * * *
    (4) * * *
    (i) If you are subject to limitations on THC emissions, you must 
operate a CEMS in accordance with the requirements in Sec.  63.1350(i). 
For the purposes of conducting the accuracy and quality assurance 
evaluations for CEMS, the THC span value (as propane) is 50 to 60 ppmvw 
and the reference method (RM) is Method 25A of appendix A to part 60 of 
this chapter.
* * * * *
    (6) * * *
    (i)(A) If the source is equipped with a wet scrubber, tray tower or 
dry scrubber, you must conduct performance testing using Method 321 of 
appendix A to this part unless you have installed a CEMS that meets the 
requirements Sec.  63.1350(l)(1). For kilns with inline raw mills, 
testing must be conducted for the raw mill on and raw mill off 
conditions.
* * * * *
    (7) * * *
    (viii) * * *
    (A) Determine the THC CEMS average values in ppmvw, and the average 
of your corresponding three total organic HAP compliance test runs, 
using Equation 12.
[GRAPHIC] [TIFF OMITTED] TP21SE17.001

Where:

x = The THC CEMS average values in ppmvw.
Xi = The THC CEMS data points for all three test runs i.
y = The organic HAP average values in ppmvw.
Yi = The organic HAP concentrations for all three test runs i.
n = The number of data points.
* * * * *
    (8) * * *
    (vi) If your kiln has an inline kiln/raw mill, you must conduct 
separate performance tests while the raw mill is operating (``mill 
on'') and while the raw mill is not operating (``mill off''). Using the 
fraction of time the raw mill is on and the fraction of time that the 
raw mill is off, calculate this limit as a weighted average of the 
SO<INF>2</INF> levels measured during raw mill on and raw mill off 
compliance testing with Equation 17.
[GRAPHIC] [TIFF OMITTED] TP21SE17.002

Where:

R = Operating limit as SO<INF>2</INF>, ppmvw.
y = Average SO<INF>2</INF> CEMS value during mill on operations, 
ppmvw.
t = Percentage of operating time with mill on, expressed as a 
decimal.
x = Average SO<INF>2</INF> CEMS value during mill off operations, 
ppmvw.
1-t = Percentage of operating time with mill off, expressed as a 
decimal.

    (vii) * * *
    (B) Determine your SO<INF>2</INF> CEMS instrument average ppm, and 
the average of your corresponding three HCl compliance test runs, using 
equation 18.
[GRAPHIC] [TIFF OMITTED] TP21SE17.003


[[Page 44283]]


Where:

x= The SO<INF>2</INF> CEMS average values in ppmvw.
X<INF>1</INF> = The SO<INF>2</INF> CEMS data points for the three 
runs constituting the performance test.
y = The HCl average values in ppmvw.
Y<INF>1</INF> = The HCl emission concentration expressed as ppmv 
corrected to 7 percent oxygen for the three runs constituting the 
performance test.
n = The number of data points.
* * * * *
    (d) [Reserved]
* * * * *
0
6. Section 63.1350 is amended by:
0
a. Revising paragraphs (g) introductory text, (g)(4), (h)(2)(ii), (j), 
(k)(2) introductory text, (k)(2)(ii), and (k)(2)(iii); and
0
b. Revising paragraphs (k)(5)(ii), (l)(1) introductory text, and 
(l)(3).
    The revisions read as follows:


Sec.  63.1350  Monitoring requirements.

* * * * *
    (g) D/F monitoring requirements. If you are subject to an emissions 
limitation on D/F emissions, you must comply with the monitoring 
requirements of paragraphs (g)(1) through (g)(5) and paragraphs (m)(1) 
through (m)(4) of this section to demonstrate continuous compliance 
with the D/F emissions standard. You must also develop an emissions 
monitoring plan in accordance with paragraphs (p)(1) through (p)(4) of 
this section.
* * * * *
    (4) Every hour, report the calculated rolling three-hour average 
temperature using the average of 180 successive one-minute average 
temperatures. See S63.1349(b)(3).
* * * * *
    (h) * * *
    (2) * * *
    (ii) Each hour, calculate the three-hour rolling average of the 
selected parameter value for the previous 3 hours of process operation 
using all of the one-minute data available (i.e., the CMS is not out-
of-control).
* * * * *
    (j) Total organic HAP monitoring requirements. If you are complying 
with the total organic HAP emissions limits, you must continuously 
monitor THC according to paragraph (i)(1) and (2) of this section or in 
accordance with Performance Specification 8 or Performance 
Specification 8A of appendix B to part 60 of this chapter and comply 
with all of the requirements for continuous monitoring systems found in 
the general provisions, subpart A of this part. You must operate and 
maintain each CEMS according to the quality assurance requirements in 
Procedure 1 of appendix F in part 60 of this chapter. You must also 
develop an emissions monitoring plan in accordance with paragraphs 
(p)(1) through (4) of this section.
    (k) * * *
    (2) In order to quality assure data measured above the span value, 
you must use one of the three options in paragraphs (k)(2)(i) through 
(iii) of this section.
* * * * *
    (ii) Quality assure any data above the span value by proving 
instrument linearity beyond the span value established in paragraph 
(k)(1) of this section using the following procedure. Conduct a weekly 
``above span linearity'' calibration challenge of the monitoring system 
using a reference gas with a certified value greater than your highest 
expected hourly concentration or greater than 75 percent of the highest 
measured hourly concentration. The ``above span'' reference gas must 
meet the requirements of PS 12A, Section 7.1 and must be introduced to 
the measurement system at the probe. Record and report the results of 
this procedure as you would for a daily calibration. The ``above span 
linearity'' challenge is successful if the value measured by the Hg 
CEMS falls within 10 percent of the certified value of the reference 
gas. If the value measured by the Hg CEMS during the above span 
linearity challenge exceeds <plus-minus>10 percent of the certified 
value of the reference gas, the monitoring system must be evaluated and 
repaired and a new ``above span linearity'' challenge met before 
returning the Hg CEMS to service, or data above span from the Hg CEMS 
must be subject to the quality assurance procedures established in 
paragraph (k)(2)(iii) of this section. In this manner all hourly 
average values exceeding the span value measured by the Hg CEMS during 
the week following the above span linearity challenge when the CEMS 
response exceeds <plus-minus>20 percent of the certified value of the 
reference gas must be normalized using Equation 22.
[GRAPHIC] [TIFF OMITTED] TP21SE17.004

    (iii) Quality assure any data above the span value established in 
paragraph (k)(1) of this section using the following procedure. Any 
time two consecutive one-hour average measured concentrations of Hg 
exceeds the span value you must, within 24 hours before or after, 
introduce a higher, ``above span'' Hg reference gas standard to the Hg 
CEMS. The ``above span'' reference gas must meet the requirements of PS 
12A, Section 7.1, must target a concentration level between 50 and 150 
percent of the highest expected hourly concentration measured during 
the period of measurements above span, and must be introduced at the 
probe. While this target represents a desired concentration range that 
is not always achievable in practice, it is expected that the intent to 
meet this range is demonstrated by the value of the reference gas. 
Expected values may include ``above span'' calibrations done before or 
after the above span measurement period. Record and report the results 
of this procedure as you would for a daily calibration. The ``above 
span'' calibration is successful if the value measured by the Hg CEMS 
is within 20 percent of the certified value of the reference gas. If 
the value measured by the Hg CEMS exceeds 20 percent of the certified 
value of the reference gas, then you must normalize the one-hour 
average stack gas values measured above the span during the 24-hour 
period preceding or following the ``above span'' calibration for 
reporting based on the Hg CEMS response to the reference gas as shown 
in equation 22. Only one ``above span'' calibration is needed per 24 
hour period.
* * * * *
    (5) * * *
    (ii) On a continuous basis, determine the mass emissions of mercury 
in lb/hr from the alkali bypass and coal mill exhausts by using the 
mercury hourly emissions rate and the exhaust gas flow rate to 
calculate hourly mercury emissions in lb/hr.
* * * * *
    (l) * * *
    (1) If you monitor compliance with the HCl emissions limit by 
operating an HCl CEMS, you must do so in accordance with Performance 
Specification 15 (PS 15) or PS 18 of appendix B to part 60 of this 
chapter, or,

[[Page 44284]]

upon promulgation, in accordance with any other performance 
specification for HCl CEMS in appendix B to part 60 of this chapter. 
You must operate, maintain, and quality assure a HCl CEMS installed and 
certified under PS 15 according to the quality assurance requirements 
in Procedure 1 of appendix F to part 60 of this chapter except that the 
Relative Accuracy Test Audit requirements of Procedure 1 must be 
replaced with the validation requirements and criteria of sections 
11.1.1 and 12.0 of PS 15. If you choose to install and operate an HCl 
CEMS in accordance with PS 18 of appendix B to part 60 of this chapter, 
you must operate, maintain, and quality assure the HCl CEMS using the 
associated Procedure 6 of appendix F to part 60 of this chapter. For 
any performance specification that you use, you must use Method 321 of 
appendix A to part 63 of this chapter as the reference test method for 
conducting relative accuracy testing. The span value and calibration 
requirements in paragraphs (l)(1)(i) and (ii) of this section apply to 
HCl CEMS other than those installed and certified under PS 15 or PS 18.
* * * * *
    (3) If the source is equipped with a wet or dry scrubber or tray 
tower, and you choose to monitor SO<INF>2</INF> emissions, monitor 
SO<INF>2</INF> emissions continuously according to the requirements of 
Sec.  60.63(e) and (f) of part 60 subpart F of this chapter. If 
SO<INF>2</INF> levels increase above the 30-day rolling average 
SO<INF>2</INF> operating limit established during your performance test 
by 10 percent or more, you must:
    (i) As soon as possible but no later than 30 days after you exceed 
the established SO<INF>2</INF> value conduct an inspection and take 
corrective action to return the SO<INF>2</INF> emissions to within the 
operating limit; and
    (ii) Within 90 days of the exceedance or at the time of the next 
compliance test, whichever comes first, conduct an HCl emissions 
compliance test to determine compliance with the HCl emissions limit 
and to verify or re-establish the SO<INF>2</INF> CEMS operating limit.
* * * * *
0
7. Section 63.1354 is amended by revising paragraph (b)(9) introductory 
text, (9)(vi), (9)(viii), and (10); and paragraph (c) to read as 
follows:


Sec.  63.1354  Reporting requirements.

* * * * *
    (b) * * *
    (9) The owner or operator shall submit a summary report 
semiannually within 60 days of the reporting period to the EPA via the 
Compliance and Emissions Data Reporting Interface (CEDRI). (CEDRI can 
be accessed through the EPA's Central Data Exchange (CDX) (www.epa.gov/cdx).) You must use the appropriate electronic report in CEDRI for this 
subpart. Instead of using the electronic report in CEDRI for this 
subpart, you may submit an alternate electronic file consistent with 
the extensible markup language (XML) schema listed on the CEDRI Web 
site (https://www.epa.gov/electronic-reporting-air-emissions/compliance-and-emissions-data-reporting-interface-cedri), once the XML 
schema is available. If the reporting form specific to this subpart is 
not available in CEDRI at the time that the report is due, you must 
submit the report the Administrator at the appropriate address listed 
in Sec.  63.13. You must begin submitting reports via CEDRI no later 
than 90 days after the form becomes available in CEDRI. The excess 
emissions and summary reports must be submitted no later than 60 days 
after the end of the reporting period, regardless of the method in 
which the reports are submitted. The report must contain the 
information specified in Sec.  63.10(e)(3)(vi). In addition, the 
summary report shall include:
* * * * *
    (vi) For each PM CPMS, HCl, Hg, and THC CEMS, or Hg sorbent trap 
monitoring system, within 60 days after the reporting periods, you must 
report all of the calculated 30-operating day rolling average values 
derived from the CPMS, CEMS, CMS, or Hg sorbent trap monitoring 
systems.
* * * * *
    (viii) You must submit the information specified in paragraphs 
(b)(9)(viii)(A) and (B) of this section no later than 60 days following 
the initial performance test. All reports must be signed by a 
responsible official.
    (A) The initial performance test data as recorded under Sec.  
63.1349(a).
    (B) The values for the site-specific operating limits or parameters 
established pursuant to Sec.  63.1349(b)(1), (3), (6), (7), and (8), as 
applicable, and a description, including sample calculations, of how 
the operating parameters were established during the initial 
performance test.
    (C) As of December 31, 2011, and within 60 days after the date of 
completing each performance evaluation or test, as defined in Sec.  
63.2, conducted to demonstrate compliance with any standard covered by 
this subpart, you must submit the relative accuracy test audit data and 
performance test data, except opacity data, to the EPA by successfully 
submitting the data electronically to the EPA's Central Data Exchange 
(CDX) by using the Electronic Reporting Tool (ERT) (see https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert). For any performance evaluations with no corresponding RATA 
pollutants listed on the ERT Web site, you must submit the results of 
the performance evaluation to the Administrator at the appropriate 
address listed in Sec.  63.13.
* * * * *
    (10) If the total continuous monitoring system downtime for any CEM 
or any CMS for the reporting period is 10 percent or greater of the 
total operating time for the reporting period, the owner or operator 
shall submit an excess emissions and continuous monitoring system 
performance report along with the summary report.
    (c) Reporting a failure to meet a standard due to a malfunction. 
For each failure to meet a standard or emissions limit caused by a 
malfunction at an affected source, you must report the failure in the 
semi-annual compliance report required by Sec.  63.1354(b)(9). The 
report must contain the date, time and duration, and the cause of each 
event (including unknown cause, if applicable), and a sum of the number 
of events in the reporting period. The report must list for each event 
the affected source or equipment, an estimate of the amount of each 
regulated pollutant emitted over the emission limit for which the 
source failed to meet a standard, and a description of the method used 
to estimate the emissions. The report must also include a description 
of actions taken by an owner or operator during a malfunction of an 
affected source to minimize emissions in accordance with Sec.  
63.1348(d), including actions taken to correct a malfunction.
0
8. Section 63.1355 is amended by revising paragraph (e) to read as 
follows:


Sec.  63.1355  Recordkeeping requirements.

* * * * *
    (e) You must keep records of the daily clinker production rates 
according to the clinker production monitoring requirements in Sec.  
63.1350(d).
* * * * *
0
9. Table 1 to subpart LLL of part 63 is amended by adding the entry 
``63.10(e)(3)(v)'' to read as follows:

[[Page 44285]]



                     Table 1 to Subpart LLL of Part 63--Applicability of General Provisions
----------------------------------------------------------------------------------------------------------------
              Citation                       Requirement          Applies to subpart LLL        Explanation
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
63.10(e)(3)(v).....................  Due Dates for Excess         No....................  Sec.   63.1354(b)(9)
                                      Emissions and CMS.                                   specifies due date.
                                     Performance Reports........
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

0
10. Add table 2 to subpart LLL of part 63 to read as follows:

Table 2 to Subpart LLL of Part 63--1989 Toxic Equivalency Factors (TEFs)
------------------------------------------------------------------------
                    Dioxins/furans                         TEFs 1989
------------------------------------------------------------------------
2,3,7,8-TCDD.........................................                  1
1,2,3,7,8-PeCDD......................................                0.5
1,2,3,4,7,8-HxCDD....................................                0.1
1,2,3,6,7,8-HxCDD....................................                0.1
1,2,3,7,8,9-HxCDD....................................                0.1
1,2,3,4,6,7,8-HpCDD..................................               0.01
OCDD.................................................              0.001
2,3,7,8-TCDF.........................................                0.1
1,2,3,7,8-PeCDF......................................               0.05
2,3,4,7,8-PeCDF......................................                0.5
1,2,3,4,7,8-HxCDF....................................                0.1
1,2,3,6,7,8-HxCDF....................................                0.1
1,2,3,7,8,9-HxCDF....................................                0.1
2,3,4,6,7,8-HxCDF....................................                0.1
1,2,3,4,6,7,8-HpCDF..................................               0.01
1,2,3,4,7,8,9-HpCDF..................................               0.01
OCDF.................................................              0.001
------------------------------------------------------------------------

[FR Doc. 2017-19448 Filed 9-20-17; 8:45 am]
 BILLING CODE 6560-50-P


</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>