National Emission Standards for Hazardous Air Pollutants for Cellulose Products Manufacturing Residual Risk and Technology Review

Federal RegisterSep 9, 2019

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

EPA-HQ-OAR-2018-0415; FRL-9998-78-OAR]

RIN 2060-AU23

National Emission Standards for Hazardous Air Pollutants for Cellulose Products Manufacturing Residual Risk and Technology Review

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The U.S. Environmental Protection Agency (EPA) is proposing amendments to the National Emissions Standards for Hazardous Air Pollutants (NESHAP) for Cellulose Products Manufacturing to address the results of the residual risk and technology review (RTR) that the EPA is required to conduct under the Clean Air Act (CAA). The EPA is proposing to amend provisions addressing periods of startup, shutdown, and malfunction (SSM); to add provisions regarding periodic emissions testing and electronic reporting; to provide more flexibility for monitoring requirements; and to make technical and editorial changes. 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 October 24, 2019. Under the Paperwork Reduction Act (PRA), comments on the information collection provisions are best assured of consideration if the Office of Management and Budget (OMB) receives a copy of your comments on or before October 9, 2019.

Public hearing.

If anyone contacts us requesting a public hearing on or before September 16, 2019, we will hold a hearing. Additional information about the hearing, if requested, will be published in a subsequent

Federal Register

document and posted at

https://www.epa.gov/stationary-sources-air-pollution/cellulose-products-manufacturing-national-emission-standards

. See

SUPPLEMENTARY INFORMATION

for information on requesting and registering for a public hearing.

ADDRESSES:

You may send comments, identified by Docket ID No. EPA-HQ-OAR-2018-0415, by any of the following methods:

•

Federal eRulemaking Portal: https://www.regulations.gov/

(our preferred method). Follow the online instructions for submitting comments.

•

Email: a-and-r-docket@epa.gov

. Include Docket ID No. EPA-HQ-OAR-2018-0415 in the subject line of the message.

•

Fax:

(202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-2018-0415.

•

Mail:

U.S. Environmental Protection Agency, EPA Docket Center, Docket ID No. EPA-HQ-OAR-2018-0415, Mail Code 28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460.

•

Hand/Courier Delivery:

EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-Friday (except federal holidays).

Instructions:

All submissions received must include the Docket ID No. for this rulemaking. Comments received may be posted without change to

https://www.regulations.gov/,

including any personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process, see the

SUPPLEMENTARY INFORMATION

section of this document.

FOR FURTHER INFORMATION CONTACT:

For questions about this proposed action, contact Dr. Kelley Spence, Sector Policies and Programs Division (Mail Code: E143-03), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-3158; fax number: (919) 541-0516; and email address:

spence.kelley@epa.gov

. 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; and email address:

hirtz.james@epa.gov

. For questions about monitoring and testing requirements, contact Ms. Theresa Lowe, Sector Policies and Programs Division (D243-05), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-4786; fax number: (919) 541-4991; and email address:

lowe.theresa@epa.gov

. For information about the applicability of the NESHAP to a particular entity, contact Ms. Maria Malave, Office of Enforcement and Compliance Assurance, U.S. Environmental Protection Agency, WJC South Building (Mail Code 2227A), 1200 Pennsylvania Avenue NW, Washington DC 20460; telephone number: (202) 564-7027; and email address:

malave.maria@epa.gov

SUPPLEMENTARY INFORMATION:

Public hearing.

Please contact Ms. Virginia Hunt at (919) 541-0832 or by email at

hunt.virginia@epa.gov

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.

Docket.

The EPA has established a docket for this rulemaking under Docket ID No. EPA-HQ-OAR-2018-0415. All documents in the docket are listed in

Regulations.gov

. Although listed, some information is not publicly available,

e.g.,

CBI (Confidential Business Information) 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, 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-2018-0415. The EPA's policy is that all comments received will be included in the public docket without change and may be made available online at

https://www.regulations.gov/,

including any personal information provided, unless the comment includes information claimed to be CBI or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through

https://www.regulations.gov/

or email. This type of information should be submitted by mail as discussed below.

The EPA may publish any comment received to its public docket. Multimedia submissions (audio, video,

etc.

) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the

primary submission (

i.e.,

on the Web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit

https://www.epa.gov/dockets/commenting-epa-dockets

The

https://www.regulations.gov/

website allows you to submit your comment anonymously, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through

https://www.regulations.gov/,

your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the internet. If you submit an electronic comment, the EPA recommends that you include your name and other contact information in the body of your comment and with any digital storage media you submit. If the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment. Electronic files should not include special characters or any form of encryption and be free of any defects or viruses. For additional information about the EPA's public docket, visit the EPA Docket Center homepage at

https://www.epa.gov/dockets

Submitting CBI.

Do not submit information containing CBI to the EPA through

https://www.regulations.gov/

or email. Clearly mark the part or all of the information that you claim to be CBI. For CBI information on any digital storage media that you mail to the EPA, mark the outside of the digital storage media as CBI and then identify electronically within the digital storage media the specific information that is claimed as CBI. In addition to one complete version of the comments that includes information claimed as CBI, you must submit a copy of the comments that does not contain the information claimed as CBI directly to the public docket through the procedures outlined in

Instructions

above. If you submit any digital storage media that does not contain CBI, mark the outside of the digital storage media clearly that it does not contain CBI. Information not marked as CBI will be included in the public docket and the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 Code of Federal Regulations (CFR) part 2. Send or deliver information identified as CBI only to the following address: OAQPS Document Control Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2018-0415.

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:

%R percent recovery

ADI Applicability Determination Index

AEGL acute exposure guideline level

AERMOD air dispersion model used by the HEM-3 model

ASTM American Society for Testing and Materials

CAA Clean Air Act

CalEPA California EPA

CBI Confidential Business Information

CDX Central Data Exchange

CEDRI Compliance and Emissions Data Reporting Interface

CEMS continuous emissions monitoring system

CEP Cellulose Ethers Production

CFR Code of Federal Regulations

CMC carboxymethyl cellulose

COS carbonyl sulfide

carbon disulfide

EPA Environmental Protection Agency

ERPG Emergency Response Planning Guideline

ERT Electronic Reporting Tool

FTIR Fourier Transform Infrared

GACT generally available control technology

S hydrogen sulfide

HAP hazardous air pollutant(s)

HCl hydrochloric acid

HEC hydroxyethyl cellulose

HEM-3 Human Exposure Model-3

HF hydrogen fluoride

HI hazard index

HPC hydroxypropyl cellulose

HPMC hydroxypropyl methyl cellulose

HQ hazard quotient

IBR incorporation by reference

ICR information collection request

ID identifier

IRIS Integrated Risk Information System

km kilometers

square kilometers

MACT maximum achievable control technology

MC methyl cellulose

mg/kg-day milligrams per kilogram per day

mg/m

milligrams per cubic meter

MIR maximum individual risk

MVP Miscellaneous Viscose Processes

NAAQS National Ambient Air Quality Standards

NAICS North American Industry Classification System

NaOH sodium hydroxide

NATA National Air Toxics Assessment

NESHAP national emission standards for hazardous air pollutants

NRC National Research Council

NTTAA National Technology Transfer and Advancement Act

OAQPS Office of Air Quality Planning and Standards

OECA Office of Enforcement and Compliance Assurance

OMB Office of Management and Budget

PAH polycyclic aromatic hydrocarbons

PB-HAP hazardous air pollutants known to be persistent and bio-accumulative in the environment

PDF portable document format

PM particulate matter

POM polycyclic organic matter

ppm parts per million

PRA Paperwork Reduction Act

QA quality assurance

RBLC Reasonably Available Control Technology/Best Available Control Technology/Lowest Achievable Emission Limits Clearinghouse

REL reference exposure level

RFA Regulatory Flexibility Act

RfC reference concentration

RfD reference dose

RTR residual risk and technology review

SAB Science Advisory Board

SBA Small Business Administration

SCC source classification code

SSM startup, shutdown, and malfunction

TOSHI target organ-specific hazard index

tpy tons per year

TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure model

UF uncertainty factor

µg/m

microgram per cubic meter

UMRA Unfunded Mandates Reform Act

URE unit risk estimate

USGS United States Geological Survey

VCS voluntary consensus standards

VOC volatile organic compounds

Organization of this document.

The information in this preamble is organized as follows:

I. General Information

A. Does this action apply to me?

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

II. Background

A. What is the statutory authority for this action?

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

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

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

III. Analytical Procedures and Decision-Making

A. How do we consider risk in our decision-making under CAA section 112(f)(2)?

B. How do we perform the technology review?

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

IV. Analytical Results and Proposed Decisions

A. What 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 effect?

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 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 Regulation 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) and 1 CFR part 51

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 categories that are 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. This proposed action will not affect federal, state, local, and tribal government entities. The

Initial List of Categories of Sources Under Section 112(c)(1) of the Clean Air Act Amendments of 1990

(see 57 FR 31576, July 16, 1992) and

Documentation for Developing the Initial Source Category List, Final Report

(

see

EPA-450/3-91-030, July 1992) included separate source categories for the various cellulose products manufacturing industries. The source categories on the initial list were Cellulose Food Casings, Rayon, Cellophane, Methyl Cellulose, Carboxymethyl Cellulose, and Cellulose Ethers Production. The Cellulose Ethers Production source category on the initial list included the hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose industries. In developing the original proposed rule for Cellulose Products Manufacturing, we identified another cellulose products manufacturing industry, Cellulosic Sponge Manufacturing, that was not on the initial source category list. We added Cellulosic Sponge Manufacturing to the source category list on November 18, 1999 (64 FR 63026) in accordance with section 112(c) of the CAA. When the EPA proposed the Cellulose Products Manufacturing NESHAP on August 28, 2000 (65 FR 52166), the Cellulose Food Casings, Rayon, Cellophane, and Cellulosic Sponge Manufacturing source categories were combined to create a new source category called “Miscellaneous Viscose Processes.” At the same time, we combined the Methyl Cellulose, Carboxymethyl Cellulose, and Cellulose Ethers Production source categories to create a newly expanded “Cellulose Ethers Production” source category. On February 12, 2002 (67 FR 6521), we published an updated source category list that included the Miscellaneous Viscose Processes (MVP) and Cellulose Ethers Production (CEP) source categories.

Table 1—NESHAP and Industrial Source Categories Affected by This Proposed Action

Source category

NESHAP

NAICS code

Miscellaneous Viscose Processes

Cellulose Products Manufacturing

325211, 325220, 326121, 326199.

Cellulose Ethers Production

Cellulose Products Manufacturing

325199.

North American Industry Classification System.

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

In addition to being available in the docket, an electronic copy of this action is available on the internet. Following signature by the EPA Administrator, the EPA will post a copy of this proposed action at

https://www.epa.gov/cellulose-products-manufacturing-national-emission-standards

. Following publication in the

Federal Register

, the EPA will post the

Federal Register

version of the proposal and key technical documents at this same website. Information on the overall RTR program is available at

https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html

A redline version of the regulatory language that incorporates the proposed changes in this action is available in the docket for this action (Docket ID No. EPA-HQ-OAR-2018-0415).

II. Background

A. What is the statutory authority for this action?

The statutory authority for this action is provided by sections 112 and 301 of the CAA, as amended (42 U.S.C. 7401

et seq.

). Section 112 of the CAA establishes a two-stage regulatory process to develop standards for emissions of HAP from stationary sources. Generally, the first stage involves establishing technology-based standards and the second stage involves evaluating those standards that are based on maximum achievable control technology (MACT) to determine whether additional standards are needed to address any remaining risk associated with HAP emissions. This second stage is commonly referred to as the “residual risk review.” In addition to the residual risk review, the CAA also requires the EPA to review standards set under CAA section 112 every 8 years to determine if there are “developments in practices, processes, or control technologies” that may be appropriate to incorporate into the standards. This review is commonly referred to as the “technology review.” When the two reviews are combined into a single rulemaking, it is commonly referred to as the “risk and technology review.” The discussion that follows identifies the most relevant statutory sections and briefly explains the contours of the methodology used to implement these statutory requirements. A more comprehensive discussion appears in the document titled

CAA Section 112 Risk and Technology Reviews: Statutory Authority and Methodology,

in the docket for this rulemaking.

In the first stage of the CAA section 112 standard setting process, the EPA

promulgates technology-based standards under CAA section 112(d) for categories of sources identified as emitting one or more of the HAP listed in CAA section 112(b). Sources of HAP emissions are either major sources or area sources, and CAA section 112 establishes different requirements for major source standards and area source standards. “Major sources” are those that emit or have the potential to emit 10 tons per year (tpy) or more of a single HAP or 25 tpy or more of any combination of HAP. All other sources are “area sources.” For major sources, CAA section 112(d)(2) provides that the technology-based NESHAP must reflect the maximum degree of emission reductions of HAP achievable (after considering cost, energy requirements, and non-air quality health and environmental impacts). These standards are commonly referred to as MACT standards. CAA section 112(d)(3) also establishes a minimum control level for MACT standards, known as the MACT “floor.” The EPA must also consider control options that are more stringent than the floor. Standards more stringent than the floor are commonly referred to as beyond-the-floor standards. In certain instances, as provided in CAA section 112(h), the EPA may set work practice standards where it is not feasible to prescribe or enforce a numerical emission standard. For area sources, CAA section 112(d)(5) gives the EPA discretion to set standards based on generally available control technologies or management practices (GACT standards) in lieu of MACT standards.

The second stage in standard-setting focuses on identifying and addressing any remaining (

i.e.,

“residual”) risk according to CAA section 112(f). For source categories subject to MACT standards, section 112(f)(2) of the CAA requires the EPA to determine whether promulgation of additional standards is needed to provide an ample margin of safety to protect public health or to prevent an adverse environmental effect. Section 112(d)(5) of the CAA provides that this residual risk review is not required for categories of area sources subject to GACT standards. Section 112(f)(2)(B) of the CAA further expressly preserves the EPA's use of the two-step approach for developing standards to address any residual risk and the Agency's interpretation of “ample margin of safety” developed in the

National Emissions Standards for Hazardous Air Pollutants: Benzene Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery Plants

(Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA notified Congress in the Risk Report that the Agency intended to use the Benzene NESHAP approach in making CAA section 112(f) residual risk determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently adopted this approach in its residual risk determinations and the United States Court of Appeals for the District of Columbia Circuit (the Court) upheld the EPA's interpretation that CAA section 112(f)(2) incorporates the approach established in the Benzene NESHAP. See

NRDC

EPA,

529 F.3d 1077, 1083 (DC Cir. 2008).

The approach incorporated into the CAA and used by the EPA to evaluate residual risk and to develop standards under CAA section 112(f)(2) is a two-step approach. In the first step, the EPA determines whether risks are acceptable. This determination “considers all health information, including risk estimation uncertainty, and includes a presumptive limit on maximum individual lifetime [cancer] risk (MIR)

of approximately 1 in 10 thousand.” 54 FR 38045, September 14, 1989. If risks are unacceptable, the EPA must determine the emissions standards necessary to reduce risk to an acceptable level without considering costs. In the second step of the approach, the EPA considers whether the emissions standards provide an ample margin of safety to protect public health “in consideration of all health information, including the number of persons at risk levels higher than approximately 1 in 1 million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision.”

Id.

The EPA must promulgate emission standards necessary to provide an ample margin of safety to protect public health or determine that the standards being reviewed provide an ample margin of safety without any revisions. After conducting the ample margin of safety analysis, we consider whether a more stringent standard is necessary to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect.

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

CAA section 112(d)(6) separately requires the EPA to review standards promulgated under CAA section 112 and revise them “as necessary (taking into account developments in practices, processes, and control technologies)” no less often than every 8 years. In conducting this review, which we call the “technology review,” the EPA is not required to recalculate the MACT floor.

Natural Resources Defense Council (NRDC)

EPA,

529 F.3d 1077, 1084 (D.C. Cir. 2008).

Association of Battery Recyclers, Inc.

EPA,

716 F.3d 667 (D.C. Cir. 2013). The EPA may consider cost in deciding whether to revise the standards pursuant to CAA section 112(d)(6).

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

The MVP source category includes any facility engaged in the production of cellulose food casings, rayon, cellophane, or cellulosic sponges, which includes the following process steps: Production of alkali cellulose from cellulose and sodium hydroxide (NaOH); production of sodium cellulose xanthate from alkali cellulose and carbon disulfide (CS

) (xanthation); production of viscose from sodium cellulose xanthate and NaOH solution; regeneration of liquid viscose into solid cellulose;

and washing of the solid cellulose product (see 65 FR 52171-2, August 28, 2000). It should be noted that, while the current Cellulose Products Manufacturing NESHAP includes standards for rayon manufacturing, all rayon plants in the United States have shut down since promulgation of the original rule.

The MVP operations use different methods and equipment to complete the regeneration step. Cellulose food casing operations extrude viscose through a die, forming a tube, while rayon operations extrude viscose through spinnerets, forming thin strands. Cellophane operations extrude viscose through a long slit, forming a flat sheet, while cellulosic sponge operations feed a mixture of viscose and Glauber's salt into a sponge mold.

The CEP source category includes any facility engaged in the production of carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methyl cellulose (MC), or hydroxypropyl methyl cellulose (HPMC), which includes the following process steps: Production of alkali cellulose from cellulose and NaOH; reaction of the alkali cellulose with one or more organic chemicals to produce a cellulose ether product;

washing and purification of the cellulose ether product; and drying of the cellulose ether product (see 65 FR 52171, August 28, 2000).

To produce CMC, HEC, HPC, MC, and HPMC, alkali cellulose is reacted with chloroacetic acid, ethylene oxide, propylene oxide, methyl chloride, and a combination of methyl chloride and propylene oxide, respectively.

This proposal includes both a residual risk assessment and a technology review of the emission sources subject to the Cellulose Products Manufacturing NESHAP. The NESHAP requires MVP operations to reduce the total sulfide emissions from their process vents and control the CS

emissions from their CS

unloading and storage operations. It also requires cellophane operations to reduce the toluene emissions from their solvent coating operations and toluene storage vessels. The NESHAP requires CEP operations to control the HAP emissions from their process vents, wastewater, equipment leaks, and liquid streams in open systems. The NESHAP requires both MVP and CEP operations to comply with work practice standards for closed-vent systems and heat exchanger systems. The NESHAP also includes various operating limits, initial and continuous compliance requirements, and recordkeeping and reporting requirements for the MVP and CEP source categories.

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

On June 8, 2018, the EPA sent out a survey to the cellulose products manufacturing industry to gather information needed to conduct the regulatory reviews required under CAA sections 112(d)(6) and 112(f)(2). The EPA divided the survey into two parts. Part 1 requested updated inventory data for emission sources subject to 40 CFR part 63, subpart UUUU, to support the residual risk assessment for the two source categories for purposes of detailed residual risk modeling. Part 2 requested available information on process equipment, control devices, and other pertinent information to support the 40 CFR part 63, subpart UUUU, technology review. The response rate for the survey was 100 percent. For more details on the data collection conducted to prepare inputs for the residual risk assessment, see the memorandum titled

Preparation of the Residual Risk Modeling Input File for Subpart UUUU,

in the docket for this rulemaking. For more details on the data collection conducted for the technology review, see the memorandum titled

Technology Review for the Cellulose Products Manufacturing Source Category—Proposed Rule,

also available in the docket.

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

In addition to survey data provided by the regulated facilities, the EPA reviewed a number of other information sources to determine if there have been developments in practices, processes, or control technologies by cellulose products manufacturing facilities to support the technology review. These information sources include:

• Emissions data (

e.g.,

stack test reports and continuous emissions monitoring system (CEMS) data) submitted with survey responses;

• Facility operating permits submitted with survey responses and collected from state agencies;

• Semiannual compliance reports submitted with survey responses;

• Other documentation submitted with survey responses (

e.g.,

compliance calculations; process flow diagrams; Safety Data Sheets; information on monitoring, wastewater, and equipment leaks);

• Information on air pollution control options utilized by the industry from the EPA's Reasonably Available Control Technology/Best Available Control Technology/Lowest Achievable Emission Limits Clearinghouse (RBLC);

• Information on applicability and compliance issues from the EPA's Applicability Determination Index (ADI); and

• Literature review of recent information on MVP and CEP practices, processes, and control technologies.

III. Analytical Procedures and Decision-Making

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

A. How do we consider risk in our decision-making under CAA section 112(f)(2)?

As discussed in section II.A of this preamble and in the Benzene NESHAP, in evaluating and developing standards under CAA section 112(f)(2), we apply a two-step approach to determine whether or not risks are acceptable and to determine if the standards provide an ample margin of safety to protect public health. As explained in the Benzene NESHAP, “the first step judgment on acceptability cannot be reduced to any single factor” and, thus, “[t]he Administrator believes that the acceptability of risk under section 112 is best judged on the basis of a broad set of health risk measures and information.” 54 FR 38046, September 14, 1989. Similarly, with regard to the ample margin of safety determination, “the Agency again considers all of the health risk and other health information considered in the first step. Beyond that information, additional factors relating to the appropriate level of control will also be considered, including cost and economic impacts of controls, technological feasibility, uncertainties, and any other relevant factors.”

Id.

The Benzene NESHAP approach provides flexibility regarding factors the EPA may consider in making determinations and how the EPA may weigh those factors for each source category. The EPA conducts a risk assessment that provides estimates of the MIR posed by the HAP emissions from each source in the source category, the hazard index (HI) for chronic exposures to HAP with the potential to cause noncancer health effects, and the hazard quotient (HQ) for acute exposures to HAP with the potential to cause noncancer health effects.

The assessment also provides estimates of the distribution of cancer risk within the exposed populations, cancer incidence, and an evaluation of the potential for an adverse environmental effect. The scope of the EPA's risk analysis is consistent with the EPA's response to comments on our policy under the Benzene NESHAP where the EPA explained that:

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

“[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 his expertise to assess available data. It also complies with the Congressional intent behind the CAA, which did not exclude the use of any particular measure of public health risk from the EPA's consideration with respect to CAA section 112 regulations, and thereby implicitly permits consideration of any and all measures of health risk which the Administrator, in his judgment, believes are appropriate to determining what will `protect the public health'.”

See 54 FR 38057, September 14, 1989. Thus, the level of the MIR is only one factor to be weighed in determining acceptability of risk. The Benzene NESHAP explained that “an MIR of approximately one in 10 thousand should ordinarily be the upper end of the range of acceptability. As risks increase above this benchmark, they become presumptively less acceptable under CAA section 112, and would be weighed with the other health risk measures and information in making an

overall judgment on acceptability. Or, the Agency may find, in a particular case, that a risk that includes an MIR less than the presumptively acceptable level is unacceptable in the light of other health risk factors.”

Id.

at 38045. In other words, risks that include an MIR above 100-in-1 million may be determined to be acceptable, and risks with an MIR below that level may be determined to be unacceptable, depending on all of the available health information. Similarly, with regard to the ample margin of safety analysis, the EPA stated in the Benzene NESHAP that: “EPA believes the relative weight of the many factors that can be considered in selecting an ample margin of safety can only be determined for each specific source category. This occurs mainly because technological and economic factors (along with the health-related factors) vary from source category to source category.”

Id.

at 38061. We also consider the uncertainties associated with the various risk analyses, as discussed earlier in this preamble, in our determinations of acceptability and ample margin of safety.

The EPA notes that it has not considered certain health information to date in making residual risk determinations. At this time, we do not attempt to quantify the HAP risk that may be associated with emissions from other facilities that do not include the source categories under review, mobile source emissions, natural source emissions, persistent environmental pollution, or atmospheric transformation in the vicinity of the sources in the categories.

The EPA understands the potential importance of considering an individual's total exposure to HAP in addition to considering exposure to HAP emissions from the source category and facility. We recognize that such consideration may be particularly important when assessing noncancer risk, where pollutant-specific exposure health reference levels (

e.g.,

reference concentrations (RfCs)) are based on the assumption that thresholds exist for adverse health effects. For example, the EPA recognizes that, although exposures attributable to emissions from a source category or facility alone may not indicate the potential for increased risk of adverse noncancer health effects in a population, the exposures resulting from emissions from the facility in combination with emissions from all of the other sources (

e.g.,

other facilities) to which an individual is exposed may be sufficient to result in an increased risk of adverse noncancer health effects. In May 2010, the Science Advisory Board (SAB) advised the EPA “that RTR assessments will be most useful to decision makers and communities if results are presented in the broader context of aggregate and cumulative risks, including background concentrations and contributions from other sources in the area.”

Recommendations of the SAB Risk and Technology Review Panel are provided in their report, which is available at:

https://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf

In response to the SAB recommendations, the EPA incorporates cumulative risk analyses into its RTR risk assessments, including those reflected in this proposal. The Agency (1) conducts facility-wide assessments, which include source category emission points, as well as other emission points within the facilities; (2) combines exposures from multiple sources in the same category that could affect the same individuals; and (3) for some persistent and bioaccumulative pollutants, analyzes the ingestion route of exposure. In addition, the RTR risk assessments consider aggregate cancer risk from all carcinogens and aggregated noncancer HQs for all noncarcinogens affecting the same target organ or target organ system.

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

B. How do we perform the technology review?

Our technology review focuses on the identification and evaluation of developments in practices, processes, and control technologies that have occurred since the MACT standards were promulgated. Where we identify such developments, we analyze their technical feasibility, estimated costs, energy implications, and non-air environmental impacts. We also consider the emission reductions associated with applying each development. This analysis informs our decision of whether it is “necessary” to revise the emissions standards. In addition, we consider the appropriateness of applying controls to new sources versus retrofitting existing sources. For this exercise, we consider any of the following to be a “development”:

• Any add-on control technology or other equipment that was not identified and considered during development of the original MACT standards;

• Any improvements in add-on control technology or other equipment (that were identified and considered during development of the original MACT standards) that could result in additional emissions reduction;

• Any work practice or operational procedure that was not identified or considered during development of the original MACT standards;

• 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

• 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 the NESHAP, we review a variety of data sources in our investigation of potential practices, processes, or controls to consider. See sections II.C and II.D of this preamble for information on the specific data sources that were reviewed as part of the technology review.

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

In this section, we provide a complete description of the types of analyses that we generally perform during the risk assessment process. In some cases, we do not perform a specific analysis because it is not relevant. For example, in the absence of emissions of HAP known to be persistent and bioaccumulative in the environment (PB-HAP), we would not perform a multipathway exposure assessment. Where we do not perform an analysis, we state that we do not and provide the reason. While we present all of our risk assessment methods, we only present risk assessment results for the analyses actually conducted (see section IV.A of this preamble).

The EPA conducts a risk assessment that provides estimates of the MIR for cancer posed by the HAP emissions from each source in the source category, the HI for chronic exposures to HAP with the potential to cause noncancer

health effects, and the HQ for acute exposures to HAP with the potential to cause noncancer health effects. The assessment also provides estimates of the distribution of cancer risk within the exposed populations, cancer incidence, and an evaluation of the potential for an adverse environmental effect. The seven sections that follow this paragraph describe how we estimated emissions and conducted the risk assessment. The docket for this rulemaking contains the following documents which provide more information on the risk assessment inputs and models:

Residual Risk Assessment for the Miscellaneous Viscose Processes Source Category in Support of the 2019 Risk and Technology Review Proposed Rule

and

Residual Risk Assessment for the Cellulose Ethers Production Source Category in Support of the 2019 Risk and Technology Review Proposed Rule

. The methods used to assess risk (as described in the eight primary steps below) are consistent with those described by the EPA in the document reviewed by a panel of the EPA's SAB in 2009;

and described in the SAB review report issued in 2010. They are also consistent with the key recommendations contained in that report.

U.S. EPA.

Risk and Technology Review (RTR) Risk Assessment Methodologies: For Review by the EPA's Science Advisory Board with Case Studies—MACT I Petroleum Refining Sources and Portland Cement Manufacturing,

June 2009. EPA-452/R-09-006.

https://www3.epa.gov/airtoxics/rrisk/rtrpg.html

1. How did we estimate actual emissions and identify the emissions release characteristics?

As discussed in section II.C of this preamble, we used data from Part 1 of the 2018 survey as the basis for the risk assessment for the MVP and CEP source categories. Part 1 of the survey, which concluded in August/September 2018, targeted facilities that are major sources of HAP emissions and involved an update of pre-populated National Emissions Inventory (NEI) data spreadsheets (or creation of new datasets). The NEI is a database that contains information about sources that emit criteria air pollutants, their precursors, and HAP. The NEI database includes estimates of actual annual air pollutant emissions from point and volume sources; emission release characteristic data such as emission release height, temperature, diameter, velocity, and flow rate; and locational latitude/longitude coordinates. We asked facilities subject to the Cellulose Products Manufacturing NESHAP to refine (or create new) inventories based on their NEI datasets for purposes of detailed residual risk modeling. Refinements included providing additional details for HAP emission sources, providing more specific information on the location and characteristics of emission points (

e.g.,

updating emission release coordinates and parameters), and adding or updating HAP emissions data for each emission release point. We compiled the updated datasets for each individual facility into MVP and CEP emissions databases to create the MACT source category residual risk modeling files.

The actual annual emissions data in the emissions databases include data from source tests, CEMS, material balances, emission factors, emission models, and engineering judgment provided by sources surveyed in Part 1 of the survey. We received a comprehensive set of emissions estimates that enabled us to conduct risk modeling of HAP emissions for all major source facilities in the MVP and CEP source categories.

We conducted substantial quality assurance (QA) efforts on the Part 1 data in order to create the modeling files needed for the 40 CFR part 63, subpart UUUU, residual risk assessment.

We first reviewed the Part 1 databases to remove non-applicable data (

e.g.,

data marked for deletion by survey respondents) unless we considered them to be source-category data, emission units identified as not subject to the Cellulose Products Manufacturing NESHAP, emission units identified as shut down, records with non-HAP data, and records with zero emissions. No duplicate emissions data were discovered during the QA.

These QA efforts are discussed in an April 15, 2019 memorandum in the docket titled

Preparation of the Residual Risk Modeling Input File for Subpart UUUU

We reviewed the databases to ensure that each record contained a facility identifier (ID), emission unit ID, and process ID. If an ID was missing, one was assigned using information provided by industry (

e.g.,

from EPA databases, from emission unit description or process description in the NEI). In some cases, emission unit IDs and process IDs were revised for consistency. Looking across the updated MVP and CEP inventories, we also reviewed whether there may be any referential integrity issues associated with these IDs (

e.g.,

having the same emission unit ID associated with multiple emission unit descriptions or having the same process ID associated with multiple process descriptions or multiple source classification codes (SCCs)). In those cases, we revised the appropriate ID to address the issue.

In addition, each record was checked to ensure it was labeled with a regulatory code, SCC, and emission process group. No regulatory codes or SCCs were found missing. The SCCs for some records were revised for consistency. Where information on emission process group was missing, the emission process group was determined based on information from SCCs, comments from survey respondents,

etc.

Next, the SCCs and emission process groups were compared and reviewed for consistency with each other; no issues were found.

We reviewed the pollutant codes in the source category risk modeling files to ensure the codes and descriptions matched the latest code lookup table used by the EPA for risk modeling files; the review found the records to be consistent.

We speciated data for chromium and mercury using default speciation criteria for those pollutants for the specific SCC. We speciated chromium emissions as hexavalent chromium (chromium VI) and trivalent chromium (chromium III). We speciated mercury emissions as particulate divalent mercury, gaseous divalent mercury, and gaseous elemental mercury. We were unable to speciate data for glycol ether for one facility because no information on the glycol ether compound(s) emitted was available from the facility in their Part 1 survey response or operating permit. For unspeciated emission inventories, it is the EPA's risk assessment policy to use the most potent noncancer health benchmark as the default emission compound; in this case, ethylene glycol methyl ether would be modeled.

We reviewed the emissions data by calculating the percent of facilities reporting each HAP, comparing emissions of a facility to category average emissions, calculating standard deviations, and identifying outliers. No pollutants in the MVP and CEP modeling files were found above or below the range for either category.

We reviewed the MVP and CEP risk modeling files to ensure that each record in these files contained an emission release point ID. If an ID was missing, one was assigned using information provided by industry (

e.g.,

from the emission unit ID or process ID). In some cases, emission release point IDs were revised for consistency. Looking across the updated MVP and CEP inventories, we also determined whether there may be any referential integrity issues associated with the emission release information. For each emission release point, each record

should have one set of coordinates (latitude and longitude) and one set of stack or fugitive parameters. All records were reviewed for consistency with respect to the emission release point. Where any such issues were identified, we revised the emission release point ID, stack/fugitive parameters, and/or coordinates to address the issue.

We reviewed emission points labeled as stacks to ensure no fugitive parameters were identified; any fugitive parameter values (usually zeroes) entered for these records were deleted. We reviewed stack parameters to ensure all were populated with reasonable values and made changes where necessary. We checked stack height data to ensure that they were greater than stack diameter. We checked exit gas flow rate data to determine whether they met the EPA's criteria that the flow rate must be within 10 percent of the calculated value (assuming a cylindrical stack). Where exit gas flow rate values did not meet the 10-percent criteria, we conducted a review to determine the source of the discrepancy (

e.g.,

the reported stack parameter was in the wrong units). We also checked for missing stack parameters and populated the missing data using values from other records for the same emission release point; if values from other records were not available, we calculated the missing value based on other related parameters for the same emission release point (

e.g.,

calculated exit gas velocity using available data for stack diameter and exit gas flow rate).

We checked fugitive parameters to ensure there was an associated length, width, and angle, and that no stack parameters for fugitive sources were erroneously populated, other than the required national defaults.

We checked coordinate values (latitude and longitude) to determine if there were any missing values and to ensure only one set of coordinates appeared for each emission release point. We populated the missing data using values from other records for the same emission release point, where possible. We revised coordinate values where necessary to ensure coordinates were consistent for the same emission point. We also checked coordinate values to ensure that all coordinates were on the facility property, by analyzing the distance between coordinates at individual facilities. Only one emission point, a wastewater treatment system emission unit, was found to be an outlier, and the coordinates of this emission point were checked and were found to lie on wastewater tanks near the boundary of the property.

We checked the source category risk modeling files for missing control measure information and filled gaps using control measure comments provided by respondents in their Part 1 survey responses or process diagrams provided by respondents in their Part 2 survey responses.

The emissions inventory for MVP sources identifies no emissions of PB-HAP. The emissions inventory for CEP sources identifies emissions of the following PB-HAP: Cadmium compounds, arsenic compounds, lead compounds, and mercury compounds. Risk-based screening levels are available for Tier 1 screening for all of the above PB-HAP except lead compounds, which are compared to the level of the current National Ambient Air Quality Standard (NAAQS) for lead.

Consistent with the EPA's standard practice in conducting risk assessments for source categories, we conducted a two-step process to determine: (1) Whether PB-HAP are being emitted; and (2) whether they are being released above screening levels. If these releases are significantly above the screening levels and the EPA has detailed information on the releases and the site, a complete multipathway analysis of the site is conducted to estimate pathway risks for the source category.

We considered actual emissions of the ecological HAP emitted from the CEP source category in the ecological HAP analysis. In addition to the PB-HAP emitted from the CEP source category, we considered hydrochloric acid (HCl) and hydrogen fluoride (HF) for ecological HAP modeling. The CEP source category, however, does not emit HF. Further information about the multipathway analysis performed for this category follows in section IV.A.2.c of this preamble.

2. How did we estimate MACT-allowable emissions?

The available emissions data in the RTR emissions dataset include estimates of the mass of HAP emitted during a specified annual time period. These “actual” emission levels are often lower than the emission levels allowed under the requirements of the current MACT standards. The emissions allowed under the MACT standards are referred to as the “MACT-allowable” emissions. We discussed the consideration of both MACT-allowable and actual emissions in the final Coke Oven Batteries RTR (70 FR 19998-19999, April 15, 2005) and in the proposed and final Hazardous Organic NESHAP RTR (71 FR 34428, June 14, 2006, and 71 FR 76609, December 21, 2006, respectively). In those actions, we noted that assessing the risk at the MACT-allowable level is inherently reasonable since that risk reflects the maximum level facilities could emit and still comply with national emission standards. We also explained that it is reasonable to consider actual emissions, where such data are available, in both steps of the risk analysis, in accordance with the Benzene NESHAP approach. (54 FR 38044, September 14, 1989.)

Actual emissions are sometimes less than allowable emissions due to a compliance margin, a more stringent state or local rule, or over-control due to the use of control technologies, equipment, or work practices that are significantly better than that required to meet 40 CFR part 63, subpart UUUU, emission limits. Consequently, as part of the Part 1 survey instructions, the EPA requested that facilities provide MACT-allowable emissions estimates.

Allowable emissions estimates were available for four of the five MVP facilities. Two MVP facilities provided their allowable emissions in their Part 1 survey spreadsheet. Two other MVP facilities provided their allowable emissions separately, in their Part 1 survey response letter. The latter two facilities stated that the stack parameters would be expected to be different if they were to emit at the allowable emissions levels because additional ductwork and ductwork modifications would be expected in order to route additional fumes to their biofilters if they increased capacity. While we do not intend MACT-allowable emissions in this risk modeling effort to represent the maximum potential-to-emit emission rate, we conservatively used this information for modeling because it was the only readily available information. We created new records in the MVP risk modeling file to include just these allowable emissions data and their associated stack parameters. To avoid any referential integrity issues, we assigned a different emission release point ID to these allowable emissions records.

The remaining MVP facility did not provide allowable emissions data in their survey spreadsheet. However, this facility is the only one in its subcategory, so the original MACT for the subcategory was based on their level of control. Consequently, we assumed that allowable emissions were equal to the reported actual emissions. So, for this facility, the allowable multiplier is 1.

There were some gaps in the allowable emissions estimates provided by the MVP facilities. Allowable emissions for carbonyl sulfide (COS) were not available for one MVP facility

for one of their processes because they report it as part of the hydrogen sulfide (H

S) limit in their title V permit. We created a new record in the MVP risk modeling file that calculated the COS allowable emissions for this process using the same multiplier as H

S (6.8). Allowable emissions for CS

were also not available for a second MVP facility for some of their processes. We calculated the allowable emissions for this facility using the median of the multipliers for those processes at the facility that had allowable emissions estimates. Using this approach, we estimated the median allowable multiplier for CS

for this facility to be approximately 2.4.

Allowable emissions estimates were available for 48 percent of the records in the CEP risk modeling file, and the remaining 52 percent of records had no allowable emissions estimates. Of that 52 percent of records, 33 percent were uncontrolled sources of organic HAP, and 19 percent were controlled sources of organic HAP.

For uncontrolled CEP sources without allowable emissions data (

e.g.,

fugitive emissions), we assumed that allowable emissions were equal to their reported actual emissions, since there is no additional control beyond current emissions. For controlled CEP sources without allowable emissions data, we reviewed Part 2 survey data on emission controls for these sources and found that all of these sources were already meeting the 99-percent control required under 40 CFR part 63, subpart UUUU, and based on the data reported, there is little if any additional control beyond current emissions. Consequently, allowable emissions are equal to actuals for controlled CEP sources.

3. How do we conduct dispersion modeling, determine inhalation exposures, and estimate individual and population inhalation risk?

Both long-term and short-term inhalation exposure concentrations and health risk from the source category addressed in this proposal were estimated using the Human Exposure Model (HEM-3).

The HEM-3 performs three primary risk assessment activities: (1) Conducting dispersion modeling to estimate the concentrations of HAP in ambient air, (2) estimating long-term and short-term inhalation exposures to individuals residing within 50 kilometers (km) of the modeled sources, and (3) estimating individual and population-level inhalation risk using the exposure estimates and quantitative dose-response information.

For more information about HEM-3, go to

https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem

a. Dispersion Modeling

The air dispersion model AERMOD, used by the HEM-3 model, is one of the EPA's preferred models for assessing air pollutant concentrations from industrial facilities.

To perform the dispersion modeling and to develop the preliminary risk estimates, HEM-3 draws on three data libraries. The first is a library of meteorological data, which is used for dispersion calculations. This library includes 1 year (2016) of hourly surface and upper air observations from 824 meteorological stations, selected to provide coverage of the United States and Puerto Rico. A second library of United States Census Bureau census block

internal point locations and populations provides the basis of human exposure calculations (U.S. Census, 2010). In addition, for each census block, the census library includes the elevation and controlling hill height, which are also used in dispersion calculations. A third library of pollutant-specific dose-response values is used to estimate health risk. These are discussed below.

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).

A census block is the smallest geographic area for which census statistics are tabulated.

b. Risk From Chronic Exposure to HAP

In developing the risk assessment for chronic exposures, we use the estimated annual average ambient air concentrations of each HAP emitted by each source in the source category. The HAP air concentrations at each nearby census block centroid located within 50 km of the facility are a surrogate for the chronic inhalation exposure concentration for all the people who reside in that census block. A distance of 50 km is consistent with both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044, September 14, 1989) and the limitations of Gaussian dispersion models, including AERMOD.

For each facility, we calculate the MIR as the cancer risk associated with a continuous lifetime (24 hours per day, 7 days per week, 52 weeks per year, 70 years) exposure to the maximum concentration at the centroid of each inhabited census block. We calculate individual cancer risk by multiplying the estimated lifetime exposure to the ambient concentration of each HAP (in micrograms per cubic meter (μg/m

)) by its unit risk estimate (URE). The URE is an upper-bound estimate of an individual's incremental risk of contracting cancer over a lifetime of exposure to a concentration of 1 microgram of the pollutant per cubic meter of air. For residual risk assessments, we generally use UREs from the EPA's Integrated Risk Information System (IRIS). For carcinogenic pollutants without IRIS values, we look to other reputable sources of cancer dose-response values, often using California EPA (CalEPA) UREs, where available. In cases where new, scientifically credible dose-response values have been developed in a manner consistent with 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 pollutant-specific dose-response values used to estimate health risk are available at

https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants

To estimate individual lifetime cancer risks associated with exposure to HAP emissions from each facility in the source category, we sum the risks for each of the carcinogenic HAP

emitted by the modeled facility. We estimate cancer risk at every census block within 50 km of every facility in the source category. The MIR is the highest individual lifetime cancer risk estimated for any of those census blocks. In addition to calculating the MIR, we estimate the distribution of individual cancer risks for the source category by summing the number of individuals within 50 km of the sources whose estimated risk falls within a specified risk range. We also estimate annual

cancer incidence by multiplying the estimated lifetime cancer risk at each census block by the number of people residing in that block, summing results for all of the census blocks, and then dividing this result by a 70-year lifetime.

The EPA's 2005

Guidelines for Carcinogen Risk Assessment

classifies carcinogens as: “carcinogenic to humans,” “likely to be carcinogenic to humans,” and “suggestive evidence of carcinogenic potential.” These classifications also coincide with the terms “known carcinogen, probable carcinogen, and possible carcinogen,” respectively, which are the terms advocated in the EPA's

Guidelines for Carcinogen Risk Assessment,

published in 1986 (51 FR 33992, September 24, 1986). In August 2000, the document,

Supplemental Guidance for Conducting Health Risk Assessment of Chemical Mixtures

(EPA/630/R-00/002), was published as a supplement to the 1986 document. Copies of both documents can be obtained from

https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944

. Summing the risk of these individual compounds to obtain the cumulative cancer risk is an approach that was recommended by the EPA's SAB in their 2002 peer review of the EPA's National Air Toxics Assessment (NATA) titled

NATA—Evaluating the National-scale Air Toxics Assessment 1996 Data—an SAB Advisory,

available at

https://yosemite.epa.gov/sab/sabproduct.nsf/214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf

To assess the risk of noncancer health effects from chronic exposure to HAP, we calculate either an HQ or a target organ-specific hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is emitted. Where more than one noncancer HAP is emitted, we sum the HQ for each of the HAP that affects a common target organ or target organ system to obtain a TOSHI. The HQ is the estimated exposure divided by the chronic noncancer dose-response value, which is a value selected from one of several sources. The preferred chronic noncancer dose-response value is the EPA RfC, defined as “an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime” (

https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary

). In cases where an RfC from the EPA's IRIS is not available or where the EPA determines that using a value other than the RfC is appropriate, the chronic noncancer dose-response value can be a value from the following prioritized sources, which define their dose-response values similarly to the EPA: (1) The Agency for Toxic Substances and Disease Registry (ATSDR) Minimum Risk Level (

https://www.atsdr.cdc.gov/mrls/index.asp

); (2) the CalEPA Chronic Reference Exposure Level (REL) (

https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0

); or (3) as noted above, a scientifically credible dose-response value that has been developed in a manner consistent with the EPA guidelines and has undergone a peer review process similar to that used by the EPA. The pollutant-specific dose-response values used to estimate health risks are available at

https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants

c. Risk From Acute Exposure to HAP That May Cause Health Effects Other Than Cancer

For each HAP for which appropriate acute inhalation dose-response values are available, the EPA also assesses the potential health risks due to acute exposure. For these assessments, the EPA makes conservative assumptions about emission rates, meteorology, and exposure location. In this proposed rulemaking, as part of our efforts to continually improve our methodologies to evaluate the risks that HAP emitted from categories of industrial sources pose to human health and the environment,

we are revising our treatment of meteorological data to use reasonable worst-case air dispersion conditions in our acute risk screening assessments instead of worst-case air dispersion conditions. This revised treatment of meteorological data and the supporting rationale are described in more detail in the

Residual Risk Assessment for the Miscellaneous Viscose Processes Source Category in Support of the 2019 Risk and Technology Review Proposed Rule

and in the

Residual Risk Assessment for the Cellulose Ethers Production Source Category in Support of the 2019 Risk and Technology Review Proposed Rule

and in Appendix 5 of both reports:

Technical Support Document for Acute Risk Screening Assessment

. We will be applying this revision in RTR rulemakings proposed on or after June 3, 2019.

See,

e.g.,

U.S. EPA.

Screening Methodologies to Support Risk and Technology Reviews (RTR): A Case Study Analysis

(Draft Report, May 2017.

https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html

To assess the potential acute risk to the maximally exposed individual, we use the peak hourly emission rate for each emission point,

reasonable worst-case air dispersion conditions (

i.e.,

99th percentile), and the point of highest off-site exposure. Specifically, we assume that peak emissions from the source category and reasonable worst-case air dispersion conditions co-occur and that a person is present at the point of maximum exposure.

In the absence of hourly emission data, we develop estimates of maximum hourly emission rates by multiplying the average actual annual emissions rates by a factor (either a category-specific factor or a default factor of 10) to account for variability. This is documented in

Residual Risk Assessment for the Miscellaneous Viscose Processes Source Category in Support of the 2019 Risk and Technology Review Proposed Rule, Residual Risk Assessment for the Cellulose Ethers Production Source Category in Support of the 2019 Risk and Technology Review Proposed Rule,

and in Appendix 5 of the reports:

Technical Support Document for Acute Risk Screening Assessment,

both are available in the docket for this rulemaking.

To characterize the potential health risks associated with estimated acute inhalation exposures to a HAP, we generally use multiple acute dose-response values, including acute RELs, acute exposure guideline levels (AEGLs), and emergency response planning guidelines (ERPG) for 1-hour exposure durations), if available, to calculate acute HQs. The acute HQ is calculated by dividing the estimated acute exposure concentration by the acute dose-response value. For each HAP for which acute dose-response values are available, the EPA calculates acute HQs.

An acute REL is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration.”

Acute RELs are based on the most sensitive, relevant, adverse health effect reported in the peer-reviewed medical and toxicological literature. They are designed to protect the most sensitive individuals in the population through the inclusion of margins of safety. Because margins of safety are incorporated to address data gaps and uncertainties, exceeding the REL does not automatically indicate an adverse health impact. AEGLs repr esent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to 8 hours.

They are guideline levels for “once-in-a-lifetime, short-term exposures to airborne concentrations of acutely toxic, high-priority chemicals.”

Id.

at 21. The AEGL-1 is specifically defined as “the airborne concentration (expressed as ppm (parts per million) or mg/m

(milligrams per cubic meter)) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.” The document also notes that “Airborne concentrations below AEGL-1 represent exposure levels that can produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain

asymptomatic, nonsensory effects.”

Id.

AEGL-2 are defined as “the airborne concentration (expressed as parts per million or milligrams per cubic meter) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.”

Id.

CalEPA issues acute RELs as part of its Air Toxics Hot Spots Program, and the 1-hour and 8-hour values are documented in

Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The Determination of Acute Reference Exposure Levels for Airborne Toxicants,

which is available at

https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary

National Academy of Sciences, 2001.

Standing Operating Procedures for Developing Acute Exposure Levels for Hazardous Chemicals,

page 2. Available at

https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf

. Note that the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances ended in October 2011, but the AEGL program continues to operate at the EPA and works with the National Academies to publish final AEGLs (

https://www.epa.gov/aegl

ERPGs are “developed for emergency planning and are intended as health-based guideline concentrations for single exposures to chemicals.”

Id.

at 1. The ERPG-1 is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient adverse health effects or without perceiving a clearly defined, objectionable odor.”

Id.

at 2. Similarly, the ERPG-2 is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.”

Id.

at 1.

ERPGS Procedures and Responsibilities

. March 2014. American Industrial Hygiene Association. Available at:

https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf

An acute REL for 1-hour exposure durations is typically lower than its corresponding AEGL-1 and ERPG-1. Even though their definitions are slightly different, AEGL-1s are often the same as the corresponding ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from our acute inhalation screening risk assessment typically result when we use the acute REL for a HAP. In cases where the maximum acute HQ exceeds 1, we also report the HQ based on the next highest acute dose-response value (usually the AEGL-1 and/or the ERPG-1).

As part of the Part 1 survey instructions, the EPA requested that facilities provide acute emissions estimates. For the MVP source category, acute emissions estimates were available for four of the five facilities. One of the four facilities was missing an acute emission estimate for COS for one process, but we were able to calculate an estimate for COS by applying the same acute multiplier for CS

for the same process at this facility. We developed separate acute multipliers for MVP process operations and MVP storage tanks to estimate acute emissions for the fifth facility. We estimated the average acute multipliers for MVP process operations and MVP storage tanks to be approximately 1.9 and 1.1, respectively.

For the CEP source category, acute emissions estimates were available for 38 percent of the records in the CEP risk modeling file. The remaining 62 percent of records had no acute emissions estimates. For CEP sources without acute emissions data, we reviewed permits and extracted maximum hourly rate data if available, and assumed the acute multiplier would be 10 if no data were available.

A further discussion of why these factors were chosen can be found in the memorandum,

Preparation of the Residual Risk Modeling Input File for Subpart UUUU,

available in the docket for this rulemaking.

In our acute inhalation screening risk assessment, acute impacts are deemed negligible for HAP for which acute HQs are less than or equal to 1, and no further analysis is performed for these HAP. This was the case for the CEP source category. In cases where an acute HQ from the screening step is greater than 1, we assess the site-specific data to ensure that the acute HQ is at an off-site location. This was required for the MVP source category, in which the data refinements employed consisted of ensuring that the locations where the maximum HQ occurred were off facility property and where the public could potentially be exposed. These refinements are discussed more fully in the

Residual Risk Assessment for the Miscellaneous Viscose Processes Source Category in Support of the 2019 Risk and Technology Review Proposed Rule

which is available in the docket for this source category.

4. How do we conduct the multipathway exposure and risk screening assessment?

The EPA conducts a tiered screening assessment examining the potential for significant human health risks due to exposures via routes other than inhalation (

i.e.,

ingestion). We first determine whether any sources in the source categories emit any HAP known to be persistent and bioaccumulative in the environment, as identified in the EPA's Air Toxics Risk Assessment Library (see Volume 1, Appendix D, at

https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library

For the MVP source category, we did not identify emissions of any PB-HAP or lead compounds. Because we did not identify PB-HAP emissions, no further evaluation of multipathway risk was conducted for this source category.

For the CEP source category, we identified PB-HAP emissions of cadmium compounds, arsenic compounds, lead compounds, and mercury compounds, so we proceeded to the next step of the evaluation. Except for lead, the human health risk screening assessment for PB-HAP consists of three progressive tiers. In a Tier 1 screening assessment, we determine whether the magnitude of the facility-specific emissions of PB-HAP warrants further evaluation to characterize human health risk through ingestion exposure. To facilitate this step, we evaluate emissions against previously developed screening threshold emission rates for several PB-HAP that are based on a hypothetical upper-end screening exposure scenario developed for use in conjunction with the EPA's Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure (TRIM.FaTE) model. The PB-HAP with screening threshold emission rates are arsenic compounds, cadmium compounds, chlorinated dibenzodioxins and furans, mercury compounds, and polycyclic organic matter (POM). Based on the EPA estimates of toxicity and bioaccumulation potential, these pollutants represent a conservative list for inclusion in multipathway risk assessments for RTR rules. (See Volume 1, Appendix D at

https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf

.) In this assessment, we compare the facility-specific emission rates of these PB-HAP to the screening threshold emission rates for each PB-HAP to assess the potential for significant human health risks via the ingestion pathway. We call this application of the TRIM.FaTE model the Tier 1 screening assessment. The ratio of a facility's actual emission rate to the Tier 1 screening threshold emission rate is a “screening value.”

We derive the Tier 1 screening threshold emission rates for these PB-HAP (other than lead compounds) to correspond to a maximum excess lifetime cancer risk of 1-in-1 million (

i.e.,

for arsenic compounds, polychlorinated dibenzodioxins and furans and POM) or, for HAP that cause noncancer health effects (

i.e.,

cadmium compounds and mercury compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP or combination of carcinogenic PB-HAP in the Tier 1 screening assessment exceeds the Tier 1 screening threshold emission rate for any facility (

i.e.,

the screening value is greater than 1), we conduct a second

screening assessment, which we call the Tier 2 screening assessment. The Tier 2 screening assessment separates the Tier 1 combined fisher and farmer exposure scenario into fisher, farmer, and gardener scenarios that retain upper-bound ingestion rates.

In the Tier 2 screening assessment, the location of each facility that exceeds a Tier 1 screening threshold emission rate is used to refine the assumptions associated with the Tier 1 fisher and farmer exposure scenarios at that facility. A key assumption in the Tier 1 screening assessment is that a lake and/or farm is located near the facility. As part of the Tier 2 screening assessment, we use a U.S. Geological Survey (USGS) database to identify actual waterbodies within 50 km of each facility and assume the fisher only consumes fish from lakes within that 50 km zone. We also examine the differences between local meteorology near the facility and the meteorology used in the Tier 1 screening assessment. We then adjust the previously-developed Tier 1 screening threshold emission rates for each PB-HAP for each facility based on an understanding of how exposure concentrations estimated for the screening scenario change with the use of local meteorology and USGS lakes database.

In the Tier 2 farmer scenario, we maintain an assumption that the farm is located within 0.5 km of the facility and that the farmer consumes meat, eggs, dairy, vegetables, and fruit produced near the facility. We may further refine the Tier 2 screening analysis by assessing a gardener scenario to characterize a range of exposures, with the gardener scenario being more plausible in RTR evaluations. Under the gardener scenario, we assume the gardener consumes home-produced eggs, vegetables, and fruit products at the same ingestion rate as the farmer. The Tier 2 screen continues to rely on the high-end food intake assumptions that were applied in Tier 1 for local fish (adult female angler at 99th percentile fish consumption of fish

) and locally grown or raised foods (90th percentile consumption of locally grown or raised foods for the farmer and gardener scenarios

). If PB-HAP emission rates do not result in a Tier 2 screening value greater than 1, we consider those PB-HAP emissions to pose risks below a level of concern. If the PB-HAP emission rates for a facility exceed the Tier 2 screening threshold emission rates, we may conduct a Tier 3 screening assessment.

Burger, J. 2002. Daily consumption of wild fish and game: Exposures of high end recreationists.

International Journal of Environmental Health Research

12:343-354.

U.S. EPA.

Exposure Factors Handbook 2011 Edition (Final)

. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/052F, 2011.

There are several analyses that can be included in a Tier 3 screening assessment, depending upon the extent of refinement warranted, including validating that the lakes are fishable, locating residential/garden locations for urban and/or rural settings, considering plume-rise to estimate emissions lost above the mixing layer, and considering hourly effects of meteorology and plume rise on chemical fate and transport (a time-series analysis). If necessary, the EPA may further refine the screening assessment through a site-specific assessment.

In evaluating the potential multipathway risk from emissions of lead compounds, rather than developing a screening threshold emission rate, we compare maximum estimated chronic inhalation exposure concentrations to the level of the current National Ambient Air Quality Standard (NAAQS) for lead.

Values below the level of the primary (health-based) lead NAAQS are considered to have a low potential for multipathway risk.

In doing so, the EPA notes that the legal standard for a primary NAAQS—that a standard is requisite to protect public health and provide an adequate margin of safety (CAA section 109(b))—differs from the CAA section 112(f) standard (requiring, among other things, that the standard provide an “ample margin of safety to protect public health”). However, the primary lead NAAQS is a reasonable measure of determining risk acceptability (

i.e.,

the first step of the Benzene NESHAP analysis) since it is designed to protect the most susceptible group in the human population—children, including children living near major lead emitting sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, applying the level of the primary lead NAAQS at the risk acceptability step is conservative, since that primary lead NAAQS reflects an adequate margin of safety.

For further information on the multipathway assessment for CEP, see the

Residual Risk Assessment for the Cellulose Ethers Production Source Category in Support of the Risk and Technology Review 2019 Proposed Rule,

which is available in the docket for this action.

5. How do we conduct the environmental risk screening assessment?

a. Adverse Environmental Effect, Environmental HAP, and Ecological Benchmarks

The EPA conducts a screening assessment to examine the potential for an adverse environmental effect as required under section 112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines “adverse environmental effect” as “any significant and widespread adverse effect, which may reasonably be anticipated, to wildlife, aquatic life, or other natural resources, including adverse impacts on populations of endangered or threatened species or significant degradation of environmental quality over broad areas.”

The EPA focuses on eight HAP, which are referred to as “environmental HAP,” in its screening assessment: Six PB-HAP and two acid gases. The PB-HAP included in the screening assessment are arsenic compounds, cadmium compounds, dioxins/furans, POM, mercury (both inorganic mercury and methyl mercury), and lead compounds. The acid gases included in the screening assessment are HCl and HF.

HAP that persist and bioaccumulate are of particular environmental concern because they accumulate in the soil, sediment, and water. The acid gases, HCl and HF, are included due to their well-documented potential to cause direct damage to terrestrial plants. In the environmental risk screening assessment, we evaluate the following four exposure media: Terrestrial soils, surface water bodies (includes water-column and benthic sediments), fish consumed by wildlife, and air. Within these four exposure media, we evaluate nine ecological assessment endpoints, which are defined by the ecological entity and its attributes. For PB-HAP (other than lead), both community-level and population-level endpoints are included. For acid gases, the ecological assessment evaluated is terrestrial plant communities.

An ecological benchmark represents a concentration of HAP that has been linked to a particular environmental effect level. For each environmental HAP, we identified the available ecological benchmarks for each assessment endpoint. We identified, where possible, ecological benchmarks at the following effect levels: Probable effect levels, lowest-observed-adverse-effect level, and no-observed-adverse-effect level. In cases where multiple effect levels were available for a particular PB-HAP and assessment endpoint, we use all of the available effect levels to help us to determine whether ecological risks exist and, if so, whether the risks could be considered significant and widespread.

For further information on how the environmental risk screening assessment was conducted, including a discussion of the risk metrics used, how the environmental HAP were identified, and how the ecological benchmarks were selected, see Appendix 9 of the

Residual Risk Assessment for the

Cellulose Ethers Production Source Category in Support of the Risk and Technology Review 2019 Proposed Rule,

which is available in the docket for this action.

b. Environmental Risk Screening Methodology

For the environmental risk screening assessment, the EPA first determined whether any facilities in the MVP and CEP source categories emitted any of the environmental HAP. For the CEP source category, we identified emissions of cadmium compounds, arsenic compounds, lead compounds, mercury compounds, and HCl. Because one or more of the environmental HAP evaluated are emitted by at least one facility in the source category, we proceeded to the second step of the evaluation. For the MVP source category, we did not identify emissions of any of the eight environmental HAP included in the screen. Because we did not identify environmental HAP emissions from the MVP source category, no further evaluation of environmental risk was conducted for that category.

c. PB-HAP Methodology

The environmental screening assessment includes six PB-HAP, arsenic compounds, cadmium compounds, dioxins/furans, POM, mercury (both inorganic mercury and methyl mercury), and lead compounds. With the exception of lead, the environmental risk screening assessment for PB-HAP consists of three tiers. The first tier of the environmental risk screening assessment uses the same health-protective conceptual model that is used for the Tier 1 human health screening assessment. TRIM.FaTE model simulations were used to back-calculate Tier 1 screening threshold emission rates. The screening threshold emission rates represent the emission rate in tons of pollutant per year that results in media concentrations at the facility that equal the relevant ecological benchmark. To assess emissions from each facility in the category, the reported emission rate for each PB-HAP was compared to the Tier 1 screening threshold emission rate for that PB-HAP for each assessment endpoint and effect level. If emissions from a facility do not exceed the Tier 1 screening threshold emission rate, the facility “passes” the screening assessment, and, therefore, is not evaluated further under the screening approach. If emissions from a facility exceed the Tier 1 screening threshold emission rate, we evaluate the facility further in Tier 2.

In Tier 2 of the environmental screening assessment, the screening threshold emission rates are adjusted to account for local meteorology and the actual location of lakes in the vicinity of facilities that did not pass the Tier 1 screening assessment. For soils, we evaluate the average soil concentration for all soil parcels within a 7.5-km radius for each facility and PB-HAP. For the water, sediment, and fish tissue concentrations, the highest value for each facility for each pollutant is used. If emission concentrations from a facility do not exceed the Tier 2 screening threshold emission rate, the facility “passes” the screening assessment and typically is not evaluated further. If emissions from a facility exceed the Tier 2 screening threshold emission rate, we evaluate the facility further in Tier 3.

As in the multipathway human health risk assessment, in Tier 3 of the environmental screening assessment, we examine the suitability of the lakes around the facilities to support life and remove those that are not suitable (

e.g.,

lakes that have been filled in or are industrial ponds), adjust emissions for plume-rise, and conduct hour-by-hour time-series assessments. If these Tier 3 adjustments to the screening threshold emission rates still indicate the potential for an adverse environmental effect (

i.e.,

facility emission rate exceeds the screening threshold emission rate), we may elect to conduct a more refined assessment using more site-specific information. If, after additional refinement, the facility emission rate still exceeds the screening threshold emission rate, the facility may have the potential to cause an adverse environmental effect.

To evaluate the potential for an adverse environmental effect from lead, we compared the average modeled air concentrations (from HEM-3) of lead around each facility in the source category to the level of the secondary NAAQS for lead. The secondary lead NAAQS is a reasonable means of evaluating environmental risk because it is set to provide substantial protection against adverse welfare effects which can include “effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility and climate, damage to and deterioration of property, and hazards to transportation, as well as effects on economic values and on personal comfort and well-being.”

d. Acid Gas Environmental Risk Methodology

The environmental screening assessment for acid gases evaluates the potential phytotoxicity and reduced productivity of plants due to chronic exposure to HF and HCl. The environmental risk screening methodology for acid gases is a single-tier screening assessment that compares modeled ambient air concentrations (from AERMOD) to the ecological benchmarks for each acid gas. To identify a potential adverse environmental effect (as defined in section 112(a)(7) of the CAA) from emissions of HF and HCl, we evaluate the following metrics: The size of the modeled area around each facility that exceeds the ecological benchmark for each acid gas, in acres and square kilometers (km

); the percentage of the modeled area around each facility that exceeds the ecological benchmark for each acid gas; and the area-weighted average screening value around each facility (calculated by dividing the area-weighted average concentration over the 50-km modeling domain by the ecological benchmark for each acid gas). For further information on the environmental screening assessment approach, see Appendix 9 of the

Residual Risk Assessment for the Cellulose Ethers Production Source Category in Support of the Risk and Technology Review 2019 Proposed Rule,

which is available in the docket for this action.

6. How do we conduct facility-wide assessments?

To put the source category risks in context, we typically examine the risks from the entire “facility,” where the facility includes all HAP-emitting operations within a contiguous area and under common control. In other words, we examine the HAP emissions not only from the source category emission points of interest, but also emissions of HAP from all other emission sources at the facility for which we have data. For this source category, we conducted the facility-wide assessment using a dataset compiled from the 2014 NEI. The source category records of that NEI dataset were removed, evaluated, and updated as described in section II.C of this preamble: What data collection activities were conducted to support this action? Once a quality assured source category dataset was available, it was placed back with the remaining records from the NEI for that facility. The facility-wide file was then used to analyze risks due to the inhalation of HAP that are emitted “facility-wide” for the populations residing within 50 km of each facility, consistent with the methods used for the source category analysis described above. For these facility-wide risk analyses, the modeled

source category risks were compared to the facility-wide risks to determine the portion of the facility-wide risks that could be attributed to the source category addressed in this proposal. We also specifically examined the facility that was associated with the highest estimate of risk and determined the percentage of that risk attributable to the source category of interest. The

Residual Risk Assessment for the Miscellaneous Viscose Processes Source Category in Support of the Risk and Technology Review 2019 Proposed Rule and the Residual Risk Assessment for the Cellulose Ethers Production Source Category in Support of the Risk and Technology Review 2019 Proposed Rule,

available through the docket for this action, provides the methodology and results of the facility-wide analyses, including all facility-wide risks and the percentage of source category contribution to facility-wide risks.

7. How do we consider uncertainties in risk assessment?

Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for this proposal. Although uncertainty exists, we believe that our approach, which used conservative tools and assumptions, ensures that our decisions are health and environmentally protective. A brief discussion of the uncertainties in the RTR emissions datasets, dispersion modeling, inhalation exposure estimates, and dose-response relationships follows below. Also included are those uncertainties specific to our acute screening assessments, multipathway screening assessments, and our environmental risk screening assessments. A more thorough discussion of these uncertainties is included in the

Residual Risk Assessment for the Miscellaneous Viscose Processes Source Category in Support of the Risk and Technology Review 2019 Proposed Rule

and the

Residual Risk Assessment for the Cellulose Ethers Production Source Category in Support of the Risk and Technology Review 2019 Proposed Rule,

which are available in the docket for this action. If a multipathway site-specific assessment was performed for this source category, a full discussion of the uncertainties associated with that assessment can be found in Appendix 11 of that document,

Site-Specific Human Health Multipathway Residual Risk Assessment Report

a. Uncertainties in the RTR Emissions Datasets

Although the development of the RTR emissions datasets 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. Some of the emission estimates considered in this analysis are annual totals for certain years, and they do not reflect short-term fluctuations during the course of a year or variations from year to year. The estimates of peak hourly emission rates for the acute effects screening assessment were based on an emission adjustment factor applied to the average annual hourly emission rates, which are intended to account for emission fluctuations due to normal facility operations.

b. Uncertainties in Dispersion Modeling

We recognize there is uncertainty in ambient concentration estimates associated with any model, including the EPA's recommended regulatory dispersion model, AERMOD. In using a model to estimate ambient pollutant concentrations, the user chooses certain options to apply. For RTR assessments, we select some model options that have the potential to overestimate ambient air concentrations (

e.g.,

not including plume depletion or pollutant transformation). We select other model options that have the potential to underestimate ambient impacts (

e.g.,

not including building downwash). Other options that we select have the potential to either under- or overestimate ambient levels (

e.g.,

meteorology and receptor locations). On balance, considering the directional nature of the uncertainties commonly present in ambient concentrations estimated by dispersion models, the approach we apply in the RTR assessments should yield unbiased estimates of ambient HAP concentrations. We also note that the selection of meteorology dataset location could have an impact on the risk estimates. As we continue to update and expand our library of meteorological station data used in our risk assessments, we expect to reduce this variability.

c. Uncertainties in Inhalation Exposure Assessment

Although every effort is made to identify all of the relevant facilities and emission points, as well as to develop accurate estimates of the annual emission rates for all relevant HAP, the uncertainties in our emission inventory likely dominate the uncertainties in the exposure assessment. Some uncertainties in our exposure assessment include human mobility, using the centroid of each census block, assuming lifetime exposure, and assuming only outdoor exposures. For most of these factors, there is neither an under nor overestimate when looking at the maximum individual risk or the incidence, but the shape of the distribution of risks may be affected. With respect to outdoor exposures, actual exposures may not be as high if people spend time indoors, especially for very reactive pollutants or larger particles. For all factors, we reduce uncertainty when possible. For example, with respect to census-block centroids, we analyze large blocks using aerial imagery and adjust locations of the block centroids to better represent the population in the blocks. We also add additional receptor locations where the population of a block is not well represented by a single location.

d. Uncertainties in Dose-Response Relationships

There are uncertainties inherent in the development of the dose-response values used in our risk assessments for cancer effects from chronic exposures and noncancer effects from both chronic and acute exposures. Some uncertainties are generally expressed quantitatively, and others are generally expressed in qualitative terms. We note, as a preface to this discussion, a point on dose-response uncertainty that is stated in the EPA's

2005 Guidelines for Carcinogen Risk Assessment;

namely, that “the primary goal of EPA actions is protection of human health; accordingly, as an Agency policy, risk assessment procedures, including default options that are used in the absence of scientific data to the contrary, should be health protective” (EPA's

2005 Guidelines for Carcinogen Risk Assessment,

page 1-7). This is the approach followed here as summarized in the next paragraphs.

Cancer UREs used in our risk assessments are those that have been developed to generally provide an upper bound estimate of risk.

That is, they represent a “plausible upper limit to the true value of a quantity” (although this is usually not a true statistical confidence limit). In some circumstances, the true risk could be as

low as zero; however, in other circumstances the risk could be greater.

Chronic noncancer RfC and reference dose (RfD) values represent chronic exposure levels that are intended to be health-protective levels. To derive dose-response values that are intended to be “without appreciable risk,” the methodology relies upon an uncertainty factor (UF) approach,

which considers uncertainty, variability, and gaps in the available data. The UFs are applied to derive dose-response values that are intended to protect against appreciable risk of deleterious effects.

IRIS glossary (

https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary

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.

See

A Review of the Reference Dose and Reference Concentration Processes,

U.S. EPA, December 2002, and

Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry,

U.S. EPA, 1994.

Many of the UFs used to account for variability and uncertainty in the development of acute dose-response values are quite similar to those developed for chronic durations. Additional adjustments are often applied to account for uncertainty in extrapolation from observations at one exposure duration (

e.g.,

4 hours) to derive an acute dose-response value at another exposure duration (

e.g.,

1 hour). Not all acute dose-response values are developed for the same purpose, and care must be taken when interpreting the results of an acute assessment of human health effects relative to the dose-response value or values being exceeded. Where relevant to the estimated exposures, the lack of acute dose-response values at different levels of severity should be factored into the risk characterization as potential uncertainties.

Uncertainty also exists in the selection of ecological benchmarks for the environmental risk screening assessment. We established a hierarchy of preferred benchmark sources to allow selection of benchmarks for each environmental HAP at each ecological assessment endpoint. We searched for benchmarks for three effect levels (

i.e.,

no-effects level, threshold-effect level, and probable effect level), but not all combinations of ecological assessment/environmental HAP had benchmarks for all three effect levels. Where multiple effect levels were available for a particular HAP and assessment endpoint, we used all of the available effect levels to help us determine whether risk exists and whether the risk could be considered significant and widespread.

Although we make every effort to identify appropriate human health effect dose-response values for all pollutants emitted by the sources in this risk assessment, some HAP emitted by the CEP 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 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 an IRIS assessment for 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 consideration of HAP reductions achieved by various control options. For the MVP source category, we have identified appropriate human health effect dose-response values for all pollutants.

For a group of compounds that are unspeciated (

e.g.,

glycol ethers), we conservatively use the most protective dose-response value of an individual compound in that group to estimate risk. Similarly, for an individual compound in a group (

e.g.,

ethylene glycol diethyl ether) that does not have a specified dose-response value, we also apply the most protective dose-response value from the other compounds in the group to estimate risk.

e. Uncertainties in Acute Inhalation Screening Assessments

In addition to the uncertainties highlighted above, there are several factors specific to the acute exposure assessment that the EPA conducts as part of the risk review under section 112 of the CAA. The accuracy of an acute inhalation exposure assessment depends on the simultaneous occurrence of independent factors that may vary greatly, such as hourly emissions rates, meteorology, and the presence of a person. In the acute screening assessment that we conduct under the RTR program, we assume that peak emissions from the source category and reasonable worst-case air dispersion conditions (

i.e.,

99th percentile) co-occur. We then include the additional assumption that a person is located at this point at the same time. Together, these assumptions represent a reasonable worst-case exposure scenario. In most cases, it is unlikely that a person would be located at the point of maximum exposure during the time when peak emissions and reasonable worst-case air dispersion conditions occur simultaneously.

f. Uncertainties in the Multipathway and Environmental Risk Screening Assessments

For each source category, we generally rely on site-specific levels of PB-HAP or environmental HAP emissions to determine whether a refined assessment of the impacts from multipathway exposures is necessary or whether it is necessary to perform an environmental screening assessment. This determination is based on the results of a three-tiered screening assessment that relies on the outputs from models—TRIM.FaTE and AERMOD—that estimate environmental pollutant concentrations and human exposures for five PB-HAP (dioxins, POM, mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For lead, we use AERMOD to determine ambient air concentrations, which are then compared to the secondary NAAQS standard for lead. Two important types of uncertainty associated with the use of these models in RTR risk assessments and inherent to any assessment that relies on environmental modeling are model uncertainty and input uncertainty.

In the context of this discussion, the term “uncertainty” as it pertains to exposure and risk encompasses both

variability

in the range of expected inputs and screening results due to existing spatial, temporal, and other factors, as well as

uncertainty

in being able to accurately estimate the true result.

Model uncertainty concerns whether the model adequately represents the actual processes (

e.g.,

movement and accumulation) that might occur in the environment. For example, does the model adequately describe the movement of a pollutant through the soil? This type of uncertainty is difficult to quantify. However, based on feedback received from previous EPA SAB reviews and other reviews, we are confident that the models used in the screening assessments are appropriate and state-of-the-art for the multipathway and environmental screening risk assessments conducted in support of 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 and environmental screening assessments, we configured the models to avoid underestimating exposure and risk. This was accomplished by selecting upper-end values from nationally representative datasets for the more influential parameters in the environmental model, including selection and spatial configuration of the area of interest, lake location and size, meteorology, surface water, soil characteristics, and structure of the aquatic food web. We also assume an ingestion exposure scenario and values for human exposure factors that represent reasonable maximum exposures.

In Tier 2 of the multipathway and environmental screening assessments, we refine the model inputs to account for meteorological patterns in the vicinity of the facility versus using upper-end national values, and we identify the actual location of lakes near the facility rather than the default lake location that we apply in Tier 1. By refining the screening approach in Tier 2 to account for local geographical and meteorological data, we decrease the likelihood that concentrations in environmental media are overestimated, thereby increasing the usefulness of the screening assessment. In Tier 3 of the screening assessments, we refine the model inputs again to account for hour-by-hour plume rise and the height of the mixing layer. We can also use those hour-by-hour meteorological data in a TRIM.FaTE run using the screening configuration corresponding to the lake location. These refinements produce a more accurate estimate of chemical concentrations in the media of interest, thereby reducing the uncertainty with those estimates. The assumptions and the associated uncertainties regarding the selected ingestion exposure scenario are the same for all three tiers.

For the environmental screening assessment for acid gases, we employ a single-tiered approach. We use the modeled air concentrations and compare those with ecological benchmarks.

For all tiers of the multipathway and environmental screening assessments, our approach to addressing model input uncertainty is generally cautious. We choose model inputs from the upper end of the range of possible values for the influential parameters used in the models, and we assume that the exposed individual exhibits ingestion behavior that would lead to a high total exposure. This approach reduces the likelihood of not identifying high risks for adverse impacts.

Despite the uncertainties, when individual pollutants or facilities do not exceed screening threshold emission rates (

i.e.,

screen out), we are confident that the potential for adverse multipathway impacts on human health is very low. On the other hand, when individual pollutants or facilities do exceed screening threshold emission rates, it does not mean that impacts are significant, only that we cannot rule out that possibility and that a refined assessment for the site might be necessary to obtain a more accurate risk characterization for the source category.

The EPA evaluates the following HAP in the multipathway and/or environmental risk screening assessments, where applicable: Arsenic, cadmium, dioxins/furans, lead, mercury (both inorganic and methyl mercury), POM, HCl, and HF. These HAP represent pollutants that can cause adverse impacts either through direct exposure to HAP in the air or through exposure to HAP that are deposited from the air onto soils and surface waters and then through the environment into the food web. These HAP represent those HAP for which we can conduct a meaningful multipathway or environmental screening risk assessment. For other HAP not included in our screening assessments, the model has not been parameterized such that it can be used for that purpose. In some cases, depending on the HAP, we may not have appropriate multipathway models that allow us to predict the concentration of that pollutant. The EPA acknowledges that other HAP beyond these that we are evaluating may have the potential to cause adverse effects and, therefore, the EPA may evaluate other relevant HAP in the future, as modeling science and resources allow.

IV. Analytical Results and Proposed Decisions

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

1. MVP Source Category

a. Chronic Inhalation Risk Assessment Results

Table 2 of this preamble provides an overall summary of the inhalation risk results of the MVP source category. 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 source category was estimated to be less than 1-in-1 million. The risk driver is acetaldehyde emissions from viscose process equipment. The total estimated cancer incidence from MVP emission sources based on actual and allowable emission levels is 0.000006 excess cancer cases per year, or one case in every 167,000 years. Emissions of acetaldehyde contributed 100 percent to this cancer incidence. Based upon actual or allowable emissions, no people were exposed to cancer risks greater than or equal to 1-in-1 million.

The maximum chronic noncancer HI (TOSHI) values for the MVP source category, based on actual and allowable emissions, were estimated to be less than 1. Based upon actual and allowable emissions, respiratory risks were driven by CS

emissions from viscose process equipment.

Table 2—MVP Inhalation Risk Assessment Results

Risk assessment

Number of

facilities

Maximum

individual

cancer risk

(in 1 million)

Estimated

population

at increased

risk of

cancer ≥1-

in-1 million

Estimated

annual cancer

incidence

(cases per year)

Maximum

chronic

noncancer

TOSHI

Maximum

refined acute

noncancer HQ

Baseline Actual Emissions

Source Category

0.000006

0.05

0.4

Facility-Wide

0.00006

0.05

Baseline Allowable Emissions

Source Category

0.000006

0.05

Based on actual, allowable, and facility-wide emissions.

Maximum individual excess lifetime cancer risk due to HAP emissions from the source category and facility-wide.

Maximum TOSHI. The target organ with the highest TOSHI for the MVP source category is the respiratory system.

The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values shown use the lowest available acute threshold value, which in most cases is the REL. When an HQ exceeds 1, we also show the HQ using the next lowest available acute dose-response value. The HQ of 0.4 is based upon an acute ERPG-1.

b. Screening Level Acute Risk Assessment Results

emissions (based on the acute (1-hour) ERPG-1 for CS

). It is also important to note that the highest HQ is based on hourly emissions multiplier for each emission process group ranging from 1 to 37 times the annual emissions rate. Acute HQs are not calculated for allowable or whole facility emissions.

c. Multipathway Risk Screening Results

The five facilities modeled in the MVP source category did not report any emissions of lead compounds, carcinogenic PB-HAP (arsenic, dioxin/furans, and POM compounds) or any noncarcinogenic PB-HAP (cadmium and mercury). Since, there are no PB-HAP or lead compounds identified in the emissions inventory for this source category, no further assessment of multipathway risk was conducted.

d. Environmental Risk Screening Results

The five facilities modeled in the MVP source category did not report any emissions of lead compounds, PB-HAP, or any acid gases (HCl or HF). Since there are no ecological HAP identified in the emissions inventory for this source category, no further assessment of ecological risk was conducted.

e. Facility-Wide Risk Results

Results of the assessment of facility-wide emissions indicate that none of the five facilities have a facility-wide MIR cancer risk greater than 1-in-1 million (refer to Table 2). The maximum facility-wide cancer risk is 1-in-1 million, driven by formaldehyde, cadmium compounds, and nickel compounds from a non-category fugitive area source. The total estimated cancer incidence from the whole facility is 0.00006 excess cancer cases per year, or one case in every 16,700 years, with zero people estimated to have cancer risks greater than 1-in-1 million. The maximum facility-wide chronic noncancer TOSHI is estimated to be less than 1, driven by source category emissions of CS

from viscose process equipment.

2. CEP Source Category

a. Chronic Inhalation Risk Assessment Results

Table 3 of this preamble provides an overall summary of the inhalation risk results of the CEP source category. 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 source category was estimated to be 80-in-1 million. The risk driver is from emissions of ethylene oxide from cellulose ether process equipment used to produce hydroxyethyl cellulose (HEC). The total estimated cancer incidence from CEP emission sources based on actual and allowable emission levels is 0.01 excess cancer cases per year, or one case in every 100 years. Emissions of ethylene oxide contributed 99 percent to this cancer incidence based upon actual emissions. Based upon actual or allowable emissions, 105,000 people were exposed to cancer risks greater than or equal to 1-in-1 million. The maximum chronic noncancer HI (TOSHI) values for the source category, based on actual and allowable emissions, were estimated to be less than 1. Based upon actual and allowable emissions, respiratory risks were driven by chlorine emissions from cellulose ether process equipment.

Table 3—CEP Inhalation Risk Assessment Results

Risk assessment

Number of

facilities

Maximum

individual

cancer risk

(in 1 million)

Estimated

population

at increased

risk of

cancer

≥1-in-1 million

Estimated

annual cancer

incidence

(cases per year)

Maximum

chronic

noncancer

TOSHI

Maximum

screening

acute

noncancer HQ

Baseline Actual Emissions

Source Category

105,000

0.01

0.06

0.1

Facility-Wide

500

570,000

0.04

Baseline Allowable Emissions

Source Category

112,000

0.01

0.2

Based on actual, allowable, and whole facility emissions.

Maximum individual excess lifetime cancer risk due to ethylene oxide emissions from outside of the source category identified as releases from holding ponds, storage tanks, tank truck unloading, and equipment/vent releases.

Maximum TOSHI. The target organ with the highest TOSHI for the CEP source category is the respiratory system.

Maximum TOSHI from whole facility are from chlorine emissions from non-category sources (classified as other). The target organ with the highest TOSHI is the respiratory system.

b. Screening Level Acute Risk Assessment Results

Worst-case acute HQs were calculated for every HAP for which there is an acute health benchmark using actual emissions. The maximum refined off-site acute noncancer HQ value for the source category was less than 1 from methanol emissions from cellulose ether process equipment (based on the acute (1-hour) REL for methanol). It is also important to note that the highest HQ is based on an hourly emissions multiplier of 10 times the annual emissions rate. Acute HQs are not calculated for allowable or whole facility emissions.

c. Multipathway Risk Screening Results

One facility within the CEP source category reported emissions of multipathway pollutants of lead compounds, carcinogenic PB-HAP (arsenic), and noncarcinogenic PB-HAP (cadmium and mercury). Results of the worst-case Tier 1 screening analysis indicate that PB-HAP emissions (based on estimates of actual emissions) emitted from the facility exceeded the screening values for the carcinogenic PB-HAP (arsenic compounds) by a factor of 2 and for the noncarcinogenic PB-HAP (cadmium and mercury) was equal to the Tier 1 screening value of 1. Based on this Tier 1 screening assessment for carcinogens, the arsenic, cadmium, and mercury emission rates for the single facility were below our level of concern. In evaluating the potential for multipathway effects from emissions of lead, we compared modeled annual lead concentrations to the secondary NAAQS for lead (0.15 μg/m

). The highest annual average lead concentration of 0.00001 µg/m

is well below the NAAQS for lead, indicating a low potential for multipathway impacts of concern due to lead.

d. Environmental Risk Screening Results

As described in section III.A of this preamble, we conducted an environmental risk screening assessment for the CEP source category. The three facilities modeled in the source category reported emissions of lead compounds and the above PB-HAP, as well as an acid gas (HCl). In the Tier 1 screening analysis for PB-HAP, we did not find any exceedances of the ecological benchmarks evaluated. 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.

e. Facility-Wide Risk Results

Results of the assessment of facility-wide emissions indicate that all three facilities modeled have a facility-wide MIR cancer risk greater than 1-in-1 million (refer to Table 3). The maximum facility-wide cancer risk is 500-in-1 million, mainly driven by ethylene oxide from sources outside the source category, including holding ponds, storage tanks, tank truck unloading, and equipment/vent releases. The next highest cancer risk was 80-in-1 million, based on whole facility emissions of ethylene oxide. The total estimated cancer incidence from the whole facility is 0.04 excess cancer cases per year, or one case in every 25 years, with 570,000 people estimated to have cancer risks greater than 1-in-1 million and 2,000 people with risks greater than 100-in-1 million. The maximum facility-wide chronic noncancer TOSHI is estimated to be equal to 4, driven by emissions of chlorine from non-category sources.

3. What demographic groups might benefit from this regulation?

To examine the potential for any environmental justice issues that might be associated with the MVP and CEP source categories, we performed a demographic analysis, which is an assessment of risks to individual demographic groups of the populations living within 5 km and within 50 km of the facilities. In the analysis, we evaluated the distribution of HAP-related cancer and noncancer risks from the MVP and CEP source categories across different demographic groups within the populations living near facilities.

For the MVP source category demographic analysis, the results for various demographic groups are based on the estimated risk from actual emissions levels for the population living within 50 km of the facilities. When examining the risk levels of those exposed to emissions from MVP facilities, we find that no one is exposed to a cancer risk at or above 1-in-1 million or to a chronic noncancer TOSHI greater than 1. The methodology and the results of the MVP demographic analysis are presented in a technical report,

Risk and Technology Review—Analysis of Demographic Factors for Populations Living Near Miscellaneous Viscose Processes Facilities,

available in the docket for this action.

The results of the CEP demographic analysis are summarized in Table 4 below. These results, for various demographic groups, are based on the

estimated risk from actual emissions levels for the population living within 50 km of the CEP facilities.

Table 4—CEP Demographic Risk Analysis Results

[CEP Source Category Demographic Assessment Results—50 km Study Area Radius]

Population with cancer risk greater than or equal to 1-in-1

million

Population with hazard index greater than 1

Nationwide

Source Category

Total Population

317,746,049

104,572

White and Minority by Percent

White

Minority

Minority by Percent

African American

Native American

0.8

0.3

Hispanic or Latino (includes white and nonwhite)

Other and Multiracial

Income by Percent

Below Poverty Level

Above Poverty Level

Education by Percent

Over 25 and without a High School Diploma

Over 25 and with a High School Diploma

Linguistically Isolated by Percent

Linguistically Isolated

The results of the CEP source category demographic analysis indicate that emissions from the source category expose approximately 104,572 people to a cancer risk at or above 1-in-1 million and approximately zero people to a chronic noncancer TOSHI greater than 1. The percentages of the at-risk population in three demographic groups (African American, above poverty level, and over 25 without highs school diploma) are greater than their respective nationwide percentages. The methodology and the results of the CEP demographic analysis are presented in the technical report,

Risk and Technology Review—Analysis of Demographic Factors for Populations Living Near Cellulose Ethers Production Facilities,

available in the docket for this action.

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

1. Risk Acceptability

As noted in section II.A 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 MIR of approximately 1-in-10 thousand.” (54 FR 38045, September 14, 1989).

In this proposal, the EPA estimated risks based on actual and allowable emissions from the MVP and CEP source categories. In determining whether risks are acceptable, the EPA considered all available health information and risk estimation uncertainty, as described above. The results for the MVP and CEP source categories indicate that both the actual and allowable inhalation cancer risks to the individual most exposed are below the presumptive limit of acceptability of 100-in-1 million.

The results for the MVP source category indicate that both the actual and allowable inhalation cancer risks to the individual most exposed are less than 1-in-1 million, well below the presumptive limit of acceptability of 100-in-1 million. The MVP source category also has chronic noncancer inhalation exposures to HAP with health benchmarks with TOSHI values less than 1 (0.05), 20 times below an exposure that the EPA has determined is without appreciable risk of adverse health effects. Exposures to HAP associated with acute noncancer health effects also are below levels of health concern with no HAP exposures resulting in an HQ greater than 1 (0.4) based upon the 1-hour REL.

The results for the CEP source category indicate that both the actual and allowable inhalation cancer risks to the individual most exposed are less or equal to 80-in-1 million, below the presumptive limit of acceptability of

100-in-1 million. EPA estimates emissions from the 3 facilities in the source category would result in a cancer incidence of 0.01 excess cancer cases per year, or one case every 100 years based upon actual emissions from the source category. This incidence rate is solely from 1 facility emitting ethylene oxide. We estimate 105,000 individuals are exposed to an inhalation cancer risk equal to or greater than 1-in-1 million from this one facility. Inhalation exposures to HAP associated with chronic noncancer health effects result in a TOSHI of 0.06 based on actual emissions, 16 times below an exposure that the EPA has determined is without appreciable risk of adverse health effects. Exposures to HAP associated with acute noncancer health effects also are below levels of health concern with no HAP exposures resulting in an HQ greater than 1 (0.1) based upon the 1-hour REL.

Multipathway screen values for the CEP source category are below a level of concern for both carcinogenic and non-carcinogenic PB-HAP as well as emissions of lead compounds. Maximum cancer and noncancer risk due to ingestion exposures estimated using Tier 1 health-protective risk screening assumptions are below 2-in-1 million for cancer and equal to 1 based upon Tier 1 noncancer screen values for mercury.

Taking into account this information, the EPA proposes that the risks remaining after implementation of the existing MACT standards for the CEP and MVP source categories are acceptable.

2. Ample Margin of Safety Analysis

The inhalation cancer risk from the MVP source category is less than 1-in-1 million and the chronic noncancer TOSHI due to inhalation exposures is less than 1. Additionally, the results of the MVP acute screening analysis showed that risks were below a level of concern. Because we are proposing that risks from the MVP source category are acceptable and below the thresholds of concern, we are proposing that the current MACT standards applicable to the MVP source category provide an ample margin of safety to protect public health.

Although we are proposing that the risks from the three modeled facilities within the CEP source category are acceptable, the MIR for actual and allowable emissions are 80-in-1 million caused by ethylene oxide emissions from the HEC process. We considered whether the MACT standards applicable to these emission points in particular, as well as all the current MACT standards applicable to this source category, provide an ample margin of safety to protect public health. As directed by CAA section 112(f)(2), we conducted an analysis to determine if the current emission standards provide an ample margin of safety to protect public health. Under the ample margin of safety analysis, we evaluated the cost and feasibility of available control technologies and other measures (including those considered under the technology review) that could be applied to the CEP source category to further reduce the risks (or potential risks) due to emissions of HAP identified in the risk assessment.

The HEC production process utilizes purified wood pulp or cotton linters to produce alkali cellulose by adding a caustic solution. The alkali cellulose is then reacted with ethylene oxide to produce HEC, which is a thickening agent used in cosmetics, cleaning solutions, and other household products. This process utilizes extended cook-out procedures to reduce the amount of ethylene oxide not consumed during the HEC reaction in conjunction with an add-on control device. This process is subject to standard 3 in Table 1 to Subpart UUUU of Part 63—Emission Limits and Work Practice Standards, which requires a 99-percent reduction in HAP emissions.

As discussed in section IV.C below and in the memo titled

Technology Review for the Cellulose Products Manufacturing Industry—Proposed Rule

in the docket for this rulemaking, we did not identify any developments in processes, practices, or controls for the CEP source category during our analysis for this proposal. CEP facilities use scrubbers to control emissions of ethylene oxide, as well as other HAP, and these devices are capable of achieving high levels of emission reductions. We did not identify additional technologies capable of further reducing emissions, or improvements to existing technologies that would result in further reduction of emissions. Given that we did not identify any developments in practices, processes, or control technologies and the acceptable risks remaining after implementation of the NESHAP, we are proposing that the existing standards for the CEP source category provide an ample margin of safety to protect public health, and revision of the standards is not required.

Lastly, regarding the facility-wide risks due to ethylene oxide (described above), which are due primarily to emission sources that are not part of the CEP source category, we intend to evaluate these facility-wide estimated emissions and risks further and may address them in a separate future action, as appropriate. In particular, the EPA is addressing ethylene oxide in response to the results of the latest National Air Toxics Assessment (NATA) released in August 2018, which identified the chemical as a potential concern in several areas across the country. (NATA is the Agency's nationwide air toxics screening tool, designed to help the EPA and state, local, and tribal air agencies identify areas, pollutants, or types of sources for further examination.) The latest NATA estimates that ethylene oxide significantly contributes to potential elevated cancer risks in some census tracts across the U.S. (less than 1 percent of the total number of tracts). These elevated risks are largely driven by an EPA risk value that was updated in late 2016. The EPA will work with industry and state, local, and tribal air agencies as the EPA takes a two-pronged approach to address ethylene oxide emissions: (1) Reviewing and, as appropriate, revising CAA regulations for facilities that emit ethylene oxide—starting with air toxics emissions standards for miscellaneous organic chemical manufacturing facilities and commercial sterilizers; and (2) conducting site-specific risk assessments and, as necessary, implementing emission control strategies for targeted high-risk facilities. The EPA will post updates on its work to address ethylene oxide on its website at:

https://www.epa.gov/ethylene-oxide

3. Adverse Environmental Effect

For the MVP source category, we did not identify emissions of any environmental HAP. Because we did not identify any environmental HAP emissions, we expect no adverse environmental effects and are proposing that more stringent standards are not necessary to prevent an adverse environmental effect.

For the CEP source category, our analyses showed no exceedances of ecological benchmarks and, therefore, we do not expect there to be an adverse environmental effect as a result of HAP emissions from this source category. We are proposing that it is not necessary to set a more stringent standard to prevent an adverse environmental effect.

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

As described in section III.B of this preamble, our technology review focused on identifying developments in practices, processes, and control technologies for control of HAP emissions from CEP and MVP facilities.

In conducting the technology review, we reviewed sources of information on practices, processes, and control technologies that were not considered during the development of the Cellulose Products Manufacturing NESHAP, as well as looked for information on improvements in practices, processes, and control technologies that have occurred since the development of the NESHAP. The review included reviewing the industry responses to Part 2 of the sector survey, a search of the RBLC database and the EPA's ADI, reviews of air permits, and a review of relevant literature. After reviewing the information from the aforementioned sources, we did not identify any developments in practices, processes, or control technologies to reduce HAP emissions from the CEP and MVP source categories. Therefore, we are proposing that revisions to the NESHAP are not necessary based on our review under CAA section 112(d)(6).

While these searches did not result in a finding of any new technologies, the results of the ADI search suggest that the EPA could add biofilter effluent conductivity operating limits and parameter monitoring as an alternative to biofilter pH operating limits and monitoring. This is discussed in section IV.D below. Additional details of our technology review can be found in the memorandum titled

Technology Review for the Cellulose Products Manufacturing Industry—Proposed Rule,

which is available in the docket for this action.

D. What other actions are we proposing?

In addition to the proposed actions described above, we are proposing additional revisions to the NESHAP. We are proposing revisions to the SSM provisions of the MACT rule in order to ensure that they are consistent with the Court decision in

Sierra Club

EPA,

551 F. 3d 1019 (D.C. Cir. 2008), which vacated two provisions that exempted sources from the requirement to comply with otherwise applicable CAA section 112(d) emission standards during periods of SSM. We also are proposing various other changes, including electronic submittal of notifications, compliance reports, and performance test reports; addition of periodic emissions testing requirements and incorporation by reference (IBR) of three test methods (listed in section IV.D.5 below); and various technical and editorial changes. Our analyses and proposed changes related to these issues are discussed below.

1. SSM

In its 2008 decision in

Sierra Club

EPA,

551 F.3d 1019 (D.C. Cir. 2008), the Court vacated portions of two provisions in the EPA's CAA section 112 regulations governing the emissions of HAP during periods of SSM. Specifically, the Court vacated the SSM exemption contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), holding that under section 302(k) of the CAA, emissions standards or limitations must be continuous in nature and that the SSM exemption violates the CAA's requirement that some section 112 standards apply continuously.

We are proposing the elimination of the SSM exemption in this rule which appears at 40 CFR 63.5515 and Table 10 to Subpart UUUU of Part 63 (Applicability of General Provisions to Subpart UUUU). Consistent with

Sierra Club

EPA,

we are proposing standards in this rule that apply at all times. We are also proposing several revisions to Table 10 (the General Provisions Applicability Table) as is explained in more detail below. For example, we are proposing to eliminate the incorporation of the General Provisions' requirement that the source develop an SSM plan. We also are proposing to eliminate and revise certain recordkeeping and reporting requirements related to the SSM exemption as further described below.

The EPA has attempted to ensure that the provisions we are proposing to eliminate are inappropriate, unnecessary, or redundant in the absence of the SSM exemption. We are specifically seeking comment on whether we have successfully done so.

In proposing the standards in this rule, the EPA has taken into account startup and shutdown periods and, for the reasons explained below, has not proposed alternate emission standards for those periods. However, the EPA is proposing alternative operating limits for periods of startup and shutdown for thermal oxidizers and scrubbers to address issues with parameter monitoring during these periods.

As discussed in the memorandum titled

Summary of the Startup and Shutdown Data for Cellulose Products Manufacturing,

we requested data regarding periods of startup and shutdown as part of the 2018 survey. Facilities did not indicate difficulty meeting the emission standards as a result of startup or shutdown events. However, facilities did indicate difficulty meeting thermal oxidizer and scrubber operating parameters during these periods. This is not unexpected because these periods reflect non-steady state operations and production. For sources equipped with thermal oxidizers, survey responses indicated that they could not meet the setpoint temperature during periods of startup. This is likely due to a temperature drop when the HAP-laden air stream is initially added to the oxidizer. Survey responses indicated that, for sources equipped with scrubbers (wet, water, and caustic), pressure drop, liquid-to-gas ratios, and scrubber liquid flow rate parameter limits could not be met during startup and shutdown. This is not unexpected since pluggage can occur during non-stable conditions, limiting the liquid flow rate and subsequently reducing the pressure drop across the scrubber due to the lack of liquid flow. Consequently, the EPA is proposing the following alternative operating parameter options to demonstrate continuous compliance and ensure proper control device operations during periods of startup and shutdown:

• Wet or caustic scrubber: As an alternative to pressure drop, liquid flow rate, or liquid-to-gas ratio, confirm that the scrubber is operating properly prior to emission unit startup and continue operation until emission unit shutdown is complete. Appropriate startup and shutdown operating parameters may be based on equipment design, manufacturer's recommendations, or other site-specific operating values established for normal operating periods. Do not include these parameters when determining the daily average.

• Thermal oxidizer: As an alternative to the minimum firebox temperature, confirm that the oxidizer is operating properly prior to emission unit startup (

e.g.,

firebox temperature has reached the setpoint temperature established in the most recent stack test). Do not include these parameters when determining the daily average.

The survey responses for other control devices did not indicate any issues meeting operating parameters during periods of startup and shutdown. One additional survey response requested the addition of a shutdown work practice for process lines and equipment venting. This response suggested that, in the event of a shutdown, it would be appropriate to purge the process gas and/or liquid to an emission control device, recovery device, or return to the process. Additionally, the response suggested that gas streams may be emitted if they contain less than 50 pounds of volatile organic compounds (VOC) or the lower explosive limit is less than 10 percent. The Agency is requesting comment to determine if this

would be an appropriate work practice. Emissions from venting due to shutdown should be accounted for in the compliance demonstration in the semiannual compliance report.

Periods of startup, normal operations, and shutdown are all predictable and routine aspects of a source's operations. Malfunctions, in contrast, are neither predictable nor routine. Instead they are, by definition, sudden, infrequent, and not reasonably preventable failures of emissions control, process, or monitoring equipment. (40 CFR 63.2) (Definition of malfunction). The EPA interprets CAA section 112 as not requiring emissions that occur during periods of malfunction to be factored into development of CAA section 112 standards and this reading has been upheld as reasonable by the Court in

U.S. Sugar Corp.

EPA,

830 F.3d 579, 606-610 (2016). Under CAA section 112, emissions standards for new sources must be no less stringent than the level “achieved” by the best controlled similar source and for existing sources generally must be no less stringent than the average emission limitation “achieved” by the best performing 12 percent of sources in the category. There is nothing in CAA section 112 that directs the Agency to consider malfunctions in determining the level “achieved” by the best performing sources when setting emission standards. As the Court has recognized, the phrase “average emissions limitation achieved by the best performing 12 percent of” sources “says nothing about how the performance of the best units is to be calculated.”

Nat'l Ass'n of Clean Water Agencies

EPA,

734 F.3d 1115, 1141 (D.C. Cir. 2013). While the EPA accounts for variability in setting emissions standards, nothing in CAA section 112 requires the Agency to consider malfunctions as part of that analysis. The EPA is not required to treat a malfunction in the same manner as the type of variation in performance that occurs during routine operations of a source. A malfunction is a failure of the source to perform in a “normal or usual manner” and no statutory language compels the EPA to consider such events in setting CAA section 112 standards.

As the Court recognized in

U.S. Sugar Corp,

accounting for malfunctions in setting standards would be difficult, if not impossible, given the myriad different types of malfunctions that can occur across all sources in the category and given the difficulties associated with predicting or accounting for the frequency, degree, and duration of various malfunctions that might occur.

Id.

at 608 (“the EPA would have to conceive of a standard that could apply equally to the wide range of possible boiler malfunctions, ranging from an explosion to minor mechanical defects. Any possible standard is likely to be hopelessly generic to govern such a wide array of circumstances.”) As such, the performance of units that are malfunctioning is not “reasonably” foreseeable. See,

e.g., Sierra Club

EPA,

167 F.3d 658, 662 (D.C. Cir. 1999) (“The EPA typically has wide latitude in determining the extent of data-gathering necessary to solve a problem. We generally defer to an agency's decision to proceed on the basis of imperfect scientific information, rather than to `invest the resources to conduct the perfect study.' ”) See also,

Weyerhaeuser

Costle,

590 F.2d 1011, 1058 (D.C. Cir. 1978) (“In the nature of things, no general limit, individual permit, or even any upset provision can anticipate all upset situations. After a certain point, the transgression of regulatory limits caused by `uncontrollable acts of third parties,' such as strikes, sabotage, operator intoxication or insanity, and a variety of other eventualities, must be a matter for the administrative exercise of case-by-case enforcement discretion, not for specification in advance by regulation.”). In addition, emissions during a malfunction event can be significantly higher than emissions at any other time of source operation. For example, if an air pollution control device with 99-percent removal goes off-line as a result of a malfunction (as might happen if, for example, the bags in a baghouse catch fire) and the emission unit is a steady state type unit that would take days to shut down, the source would go from 99-percent control to zero control until the control device was repaired. The source's emissions during the malfunction would be 100 times higher than during normal operations. As such, the emissions over a 4-day malfunction period would exceed the annual emissions of the source during normal operations. As this example illustrates, accounting for malfunctions could lead to standards that are not reflective of (and significantly less stringent than) levels that are achieved by a well-performing non-malfunctioning source. It is reasonable to interpret CAA section 112 to avoid such a result. The EPA's approach to malfunctions is consistent with CAA section 112 and is a reasonable interpretation of the statute.

Although no statutory language compels the EPA to set standards for malfunctions, the EPA has the discretion to do so where feasible. For example, in the Petroleum Refinery Sector RTR, the EPA established a work practice standard for unique types of malfunction that result in releases from pressure relief devices or emergency flaring events because the EPA had information to determine that such work practices reflected the level of control that applies to the best performers. 80 FR 75178, 75211-14 (December 1, 2015). The EPA will consider whether circumstances warrant setting standards for a particular type of malfunction and, if so, whether the EPA has sufficient information to identify the relevant best performing sources and establish a standard for such malfunctions. We also encourage commenters to provide any such information.

The EPA anticipates that it is unlikely that a malfunction will result in a violation of the standard for this source category. For example, facilities using thermal oxidizers as pollution control equipment indicated in the 2018 survey that interlocks would shut down the process if an oxidizer malfunction occurred, and facilities may also have back-up oxidizers that could be used to treat the emissions. The MACT standards are based on a percent reduction of HAP over a 6-month rolling period per group of equipment. Therefore, the malfunction of a singular piece of equipment in a single month over this period is unlikely to result in an exceedance of the standard. The EPA is soliciting information on the type of events that constitute a malfunction event, and best practices and best level of emission control during malfunction events. The EPA is also soliciting information on the cost savings associated with these practices. In addition, the EPA is soliciting specific supporting data on HAP emissions during malfunction events for the MVP and CEP source categories, including the cause of malfunctions, the frequency of malfunctions, the duration of malfunctions, and the estimate of HAP emitted during each malfunction.

In the unlikely event that a source fails to comply with the applicable CAA section 112(d) standards as a result of a malfunction event, the EPA would determine an appropriate response based on, among other things, the good faith efforts of the source to minimize emissions during malfunction periods, including preventative and corrective actions, as well as root cause analyses to ascertain and rectify excess emissions. The EPA would also consider whether the source's failure to comply with the CAA section 112(d) standard was, in fact, sudden, infrequent, not reasonably preventable

and was not instead caused in part by poor maintenance or careless operation. 40 CFR 63.2 (definition of malfunction).

If the EPA determines in a particular case that an enforcement action against a source for violation of an emission standard is warranted, the source can raise any and all defenses in that enforcement action and the federal district court will determine what, if any, relief is appropriate. The same is true for citizen enforcement actions. Similarly, the presiding officer in an administrative proceeding can consider any defense raised and determine whether administrative penalties are appropriate.

In summary, the EPA interpretation of the CAA and, in particular, section 112, is reasonable and encourages practices that will avoid malfunctions. Administrative and judicial procedures for addressing exceedances of the standards fully recognize that violations may occur despite good faith efforts to comply and can accommodate those situations.

U.S. Sugar Corp.

EPA,

830 F.3d 579, 606-610 (2016).

a. General Duty

We are proposing to revise the General Provisions table (Table 10) entry for 40 CFR 63.6(e)(1) and (2) by redesignating it as 40 CFR 63.6(e)(1)(i) and changing the “yes” in column 4 to a “no.” Section 63.6(e)(1)(i) describes the general duty to minimize emissions. Some of the language in that section is no longer necessary or appropriate in light of the elimination of the SSM exemption. We are proposing instead to add general duty regulatory text at 40 CFR 63.5515 that reflects the general duty to minimize emissions while eliminating the reference to periods covered by an SSM exemption. The current language in 40 CFR 63.6(e)(1)(i) characterizes what the general duty entails during periods of SSM. With the elimination of the SSM exemption, there is no need to differentiate between normal operations, startup and shutdown, and malfunction events in describing the general duty. Therefore, the language the EPA is proposing for 40 CFR 63.5515 does not include that language from 40 CFR 63.6(e)(1).

We are also proposing to revise the General Provisions table (Table 10) by adding an entry for 40 CFR 63.6(e)(1)(ii) and including a “no” in column 4. Section 63.6(e)(1)(ii) imposes requirements that are not necessary with the elimination of the SSM exemption or are redundant with the general duty requirement being added at 40 CFR 63.5515.

b. SSM Plan

We are proposing to revise the General Provisions table (Table 10) entry for 40 CFR 63.6(e)(3) by changing the “yes” in column 4 to a “no.” Generally, the paragraphs under 40 CFR 63.6(e)(3) require development of an SSM plan and specify SSM recordkeeping and reporting requirements related to the SSM plan. As noted, the EPA is proposing to remove the SSM exemptions. Therefore, affected units will be subject to an emission standard during such events. The applicability of a standard during such events will ensure that sources have ample incentive to plan for and achieve compliance and, thus, the SSM plan requirements are no longer necessary.

c. Compliance With Standards

We are proposing to revise the General Provisions table (Table 10) entry for 40 CFR 63.6(f)(1) by changing the “yes” in column 4 to a “no.” The current language of 40 CFR 63.6(f)(1) exempts sources from non-opacity standards during periods of SSM. As discussed above, the Court in

Sierra Club

vacated the exemptions contained in this provision and held that the CAA requires that some CAA section 112 standard apply continuously. Consistent with

Sierra Club,

the EPA is proposing to revise standards in this rule to apply at all times.

We are proposing to revise the General Provisions table (Table 10) entry for 40 CFR 63.6(h) by redesignating it as 40 CFR 63.6(h)(1) and changing the “yes” in column 4 to a “no.” The current language of 40 CFR 63.6(h)(1) exempts sources from opacity standards during periods of SSM. As discussed above, the Court in

Sierra Club

vacated the exemptions contained in this provision and held that the CAA requires that some CAA section 112 standard apply continuously. Consistent with

Sierra Club,

the EPA is proposing to revise standards in this rule to apply at all times.

d. Performance Testing

We are proposing to revise the General Provisions table (Table 10) entry for 40 CFR 63.7(e)(1) by changing the “yes” in column 4 to a “no.” Section 63.7(e)(1) describes performance testing requirements. The EPA is instead proposing to add a performance testing requirement at 40 CFR 63.5535. The performance testing requirements we are proposing to add differ from the General Provisions performance testing provisions in several respects. The regulatory text does not include the language in 40 CFR 63.7(e)(1) that restated the SSM exemption and language that precluded startup and shutdown periods from being considered “representative” for purposes of performance testing. The proposed performance testing provisions do not allow performance testing during startup or shutdown. As in 40 CFR 63.7(e)(1), performance tests conducted under this subpart should not b

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