105986 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 63 

[EPA–HQ–OAR–2023–0282; FRL–10854–01– 

OAR] 

RIN 2060–AW01 

Review of National Emission 

Standards for Hazardous Air Pollutants 

for Polyether Polyols Production 

Industry 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The U.S. Environmental 

Protection Agency (EPA) is proposing 

amendments to the National Emission 

Standards for Hazardous Air Pollutants 

(NESHAP) under the Clean Air Act 

(CAA) that apply to the Polyether 

Polyols (PEPO) Production industry 

(referred to as the PEPO NESHAP in this 

document). The EPA is proposing 

decisions resulting from the Agency’s 

technology review of the PEPO NESHAP 

and decisions based on its 

reconsideration of certain issues raised 

in an administrative petition for 

reconsideration. Furthermore, the EPA 

is proposing to strengthen the emission 

standards for ethylene oxide (EtO) 

emissions after considering the results 

of a risk assessment for the PEPO 

NESHAP. The EPA is also proposing to 

require performance testing once every 

5 years, to add work practice standards 

for certain activities where alternatives 

are appropriate, and to add provisions 

for electronic reporting. We estimate 

that the proposed amendments to the 

PEPO NESHAP, excluding the EtO 

emission standards, would reduce 

hazardous air pollutant (HAP) emissions 

from PEPO sources by approximately 

157 tons per year (tpy). Additionally, 

the proposed EtO emission standards 

are expected to reduce EtO emissions by 

approximately 14 tpy. We also estimate 

that these proposed amendments to the 

NESHAP will reduce excess emissions 

of HAP from flares in the PEPO 

Production source category by an 

additional 75 tpy. 

DATES: 

Comments. Comments must be 

received on or before February 25, 2025. 

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 January 27, 2025. 

Public hearing. If anyone contacts us 

requesting a public hearing on or before 

January 3, 2025, we will hold a virtual 

public hearing. See SUPPLEMENTARY

INFORMATION for information on 

requesting and registering for a public 

hearing. 

ADDRESSES: You may send comments, 

identified by Docket ID No. EPA–HQ– 

OAR–2023–0282, 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– 

2023–0282 in the subject line of the 

message. 

• Fax: 202–566–9744. Attention 

Docket ID No. EPA–HQ–OAR–2023– 

0282. 

• Mail: U.S. Environmental 

Protection Agency, EPA Docket Center, 

Docket ID No. EPA–HQ–OAR–2023– 

0282, 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 U.S. EPA, Attn: Ms. Johanna 

Klein, Mail Drop: E143–01, 109 T.W. 

Alexander Drive, P.O. Box 12055, 

Research Triangle Park, North Carolina 

27711; telephone number: (919) 541– 

2283; and email address: 

klein.johanna@epa.gov. For specific 

information regarding the risk modeling 

methodology, contact U.S. EPA, Attn: 

Ms. Dianna Francisco, Mail Drop: C539– 

02, 109 T.W. Alexander Drive, P.O. Box 

12055, Research Triangle Park, North 

Carolina 27711; telephone number: 

(919) 541–3182; and email address: 

francisco.dianna@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Participation in virtual public 

hearing. To request a virtual public 

hearing, contact the public hearing team 

at (888) 372–8699 or by email at 

SPPDpublichearing@epa.gov. If 

requested, the hearing will be held via 

virtual platform. The EPA will 

announce the date of the hearing and 

further details on the virtual public 

hearing at https://www.epa.gov/ 

stationary-sources-air-pollution/ 

polyether-polyols-production-nationalemission-standards-hazardous. The 

hearing will convene at 11:00 a.m. 

Eastern Time (ET) and will conclude at 

4:00 p.m. ET. The EPA may close a 

session 15 minutes after the last preregistered speaker has testified if there 

are not additional speakers. 

The EPA will begin pre-registering 

speakers for the hearing no later than 1 

business day after a request has been 

received. To register to speak at the 

virtual hearing, please use the online 

registration form available at https:// 

www.epa.gov/stationary-sources-airpollution/polyether-polyols-productionnational-emission-standards-hazardous 

or contact the public hearing team at 

(888) 372–8699 or by email at 

SPPDpublichearing@epa.gov. The last 

day to pre-register to speak at the 

hearing will be January 13, 2025. Prior 

to the hearing, the EPA will post a 

general agenda that will list preregistered speakers at: https:// 

www.epa.gov/stationary-sources-airpollution/polyether-polyols-productionnational-emission-standards-hazardous. 

The EPA will make every effort to 

follow the schedule as closely as 

possible on the day of the hearing; 

however, please plan for the hearings to 

run either ahead of schedule or behind 

schedule. 

Each commenter will have 4 minutes 

to provide oral testimony. The EPA 

encourages commenters to submit a 

copy of their oral testimony as written 

comments to the rulemaking docket. 

The EPA may ask clarifying questions 

during the oral presentations but will 

not respond to the presentations at that 

time. Written statements and supporting 

information submitted during the 

comment period will be considered 

with the same weight as oral testimony 

and supporting information presented at 

the public hearing. 

Please note that any updates made to 

any aspect of the hearing will be posted 

online at https://www.epa.gov/ 

stationary-sources-air-pollution/ 

polyether-polyols-production-nationalemission-standards-hazardous. While 

the EPA expects the hearing to go 

forward as set forth above, please 

monitor these websites or contact the 

public hearing team at (888) 372–8699 

or by email at 

SPPDpublichearing@epa.gov to 

determine if there are any updates. The 

EPA does not intend to publish a 

document in the Federal Register 

announcing updates. 


jspears on DSK121TN23PROD with PROPOSALS
Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 105987 

If you require the services of a 

translator or a special accommodation 

such as audio description, please preregister for the hearing with the public 

hearing team and describe your needs 

by January 7, 2025. The EPA may not be 

able to arrange accommodations without 

advance notice. 

Docket. The EPA has established a 

docket for this rulemaking under Docket 

ID No. EPA–HQ–OAR–2023–0282. All 

documents in the docket are listed in 

https://www.regulations.gov. Although 

listed, some information is not publicly 

available, e.g., Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the internet and will be publicly 

available only in hard copy. With the 

exception of such material, publicly 

available docket materials are available 

electronically in Regulations.gov. 

Instructions. Direct your comments to 

Docket ID No. EPA–HQ–OAR–2023– 

0282. The EPA’s policy is that all 

comments received will be included in 

the public docket without change and 

may be made available online at https:// 

www.regulations.gov, including any 

personal information provided, unless 

the comment includes information 

claimed to be CBI or other information 

whose disclosure is restricted by statute. 

Do not submit electronically to https:// 

www.regulations.gov any information 

that you consider to be CBI or other 

information whose disclosure is 

restricted by statue. This type of 

information should be submitted 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/. 

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, 

note the docket ID, mark the outside of 

the digital storage media as CBI, and 

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 and 

note the docket ID. 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. 

Our preferred method to receive CBI 

is for it to be transmitted electronically 

using email attachments, File Transfer 

Protocol (FTP), or other online file 

sharing services (e.g., Dropbox, 

OneDrive, Google Drive). Electronic 

submissions must be transmitted 

directly to the Office of Air Quality 

Planning and Standards (OAQPS) CBI 

Office at the email address 

oaqpscbi@epa.gov and, as described 

above, should include clear CBI 

markings and note the docket ID. If 

assistance is needed with submitting 

large electronic files that exceed the file 

size limit for email attachments, and if 

you do not have your own file sharing 

service, please email oaqpscbi@epa.gov 

to request a file transfer link. If sending 

CBI information through the postal 

service, please send it to the following 

address: U.S. EPA, Attn: OAQPS 

Document Control Officer, Mail Drop: 

C404–02, 109 T.W. Alexander Drive, 

P.O. Box 12055, Research Triangle Park, 

North Carolina 27711, Attention Docket 

ID No. EPA–HQ–OAR–2023–0282. The 

mailed CBI material should be double 

wrapped and clearly marked. Any CBI 

markings should not show through the 

outer envelope. 

Preamble acronyms and 

abbreviations. Throughout this 

preamble the use of ‘‘we,’’ ‘‘us,’’ or 

‘‘our’’ is intended to refer to the EPA. 

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: 

ACC American Chemistry Council 

ACS American Community Survey 

ADAF age-dependent adjustment factor 

AEGL acute exposure guideline levels 

AERMOD American Meteorological 

Society/EPA Regulatory Model dispersion 

modeling system 

AIHA American Industrial Hygiene 

Association 

ANSI American National Standards 

Institute 

APCD air pollution control device 

ASME American Society of Mechanical 

Engineers 

ATSDR Agency for Toxic Substances and 

Disease Registry 

1-BP 1-bromopropane 

BACT best available control technology 

BTU British thermal units 

CAA Clean Air Act 

CBI Confidential Business Information 

CDX Central Data Exchange 

CEDRI Compliance and Emissions Data 

Reporting Interface 

CFR Code of Federal Regulations 

CMAS Chemical Manufacturing Area 

Sources 

CMPU chemical manufacturing process 

unit 

CO carbon monoxide 

CO2 carbon dioxide 

DNA deoxyribonucleic acid 

EAV equivalent annualized value 

ECHO Enforcement and Compliance 

History Online 

ECO extended cookout 

EFR external floating roof 

EIA Economic Impact Analysis 

EJ environmental justice 

EMACT Ethylene Production MACT 

EPA Environmental Protection Agency 

ERPG emergency response planning 

guidelines 

ERT Electronic Reporting Tool 

EtO ethylene oxide 

FID flame ionization detector 

FTIR Fourier transform infrared 

spectrometry 

GACT generally available control 

technologies 


jspears on DSK121TN23PROD with PROPOSALS
105988 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

HAP hazardous air pollutant(s) 

HCl hydrochloric acid 

HEM Human Exposure Model 

HF hydrofluoric acid 

HON Hazardous Organic NESHAP 

HQ hazard quotient 

HRVOC highly reactive volatile organic 

compound 

ICR information collection request 

IFR internal floating roof 

IRIS Integrated Risk Information System 

ISA Integrated Science Assessment 

km kilometer 

kPa kilopascals 

LAER lowest achievable emission rate 

lb/hr pounds per hour 

LDAR leak detection and repair 

LEAN Louisiana Environmental Action 

Network 

LEL lower explosive limit 

MACT maximum achievable control 

technology 

MIR maximum individual lifetime [cancer] 

risk 

MON Miscellaneous Organic Chemical 

Manufacturing NESHAP 

MTVP maximum true vapor pressure 

NAAQS National Ambient Air Quality 

Standard 

NAICS North American Industry 

Classification System 

NEI National Emissions Inventory 

NESHAP national emission standards for 

hazardous air pollutants 

NHVcz net heating value in the combustion 

zone gas 

NHVdil net heating value dilution 

parameter 

NHVvg net heating value in the vent gas 

NOX nitrogen oxides 

NRDC Natural Resources Defense Council 

NSPS new source performance standards 

NTTAA National Technology Transfer and 

Advancement Act 

OAQPS Office of Air Quality Planning and 

Standards 

OAR Office of Air and Radiation 

OLD Organic Liquids Distribution 

OMB Office of Management and Budget 

P&R I Group I Polymers and Resins 

NESHAP 

PDF portable document format 

PEPO polyether polyol 

PMPU polyether polyol manufacturing 

process unit 

POM polycyclic organic matter 

ppmv parts per million by volume 

ppmw parts per million by weight 

PRA Paperwork Reduction Act 

psia pounds per square inch absolute 

psig pounds per square inch gauge 

PRD pressure relief devices 

PV present value 

RACT reasonably available control 

technology 

RDL representative detection limit 

REL Reference Exposure Level 

RFA Regulatory Flexibility Act 

RfC reference concentration 

RTR Risk and Technology Review 

SAB Science Advisory Board 

SCAQMD South Coast Air Quality 

Management District 

scmm standard cubic meters per minute 

scf standard cubic foot 

SOCMI Synthetic Organic Chemical 

Manufacturing Industry 

SO2 sulfur dioxide 

SSM startup, shutdown, and malfunction 

TCEQ Texas Commission on Environmental 

Quality 

THF tetrahydrofuran 

TOC total organic compound 

TOSHI target organ-specific hazard index 

tpy tons per year 

TRE total resource effectiveness 

TRIM Total Risk Integrated Methodology 

UF uncertainty factor 

UMRA Unfunded Mandates Reform Act 

URE unit risk estimate 

U.S. United States 

U.S.C. United States Code 

USGS U.S. Geological Survey 

VCS voluntary consensus standards 

VOC volatile organic compound(s) 

mg/m3 micrograms per cubic meter 

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 the source category and how do 

the current standards 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? 

E. What outreach was conducted? 

III. Analytical Procedures and DecisionMaking 

A. How do we consider risk in our 

decision-making? 

B. How do we estimate post-MACT risk 

posed by the source category? 

C. How do we perform the technology 

review? 

D. How do we determine a MACT floor and 

consider beyond-the-floor? 

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 actions are we taking pursuant to 

CAA sections 112(d)(2) and (3) and 

112(h)? 

E. What other actions are we proposing? 

F. What compliance dates are we 

proposing? 

V. Summary of Cost, Environmental, and 

Economic Impacts 

A. What are the affected sources? 

B. What are the air quality impacts? 

C. What are the cost impacts? 

D. What are the economic impacts? 

E. What are the benefits? 

F. What analysis of environmental justice 

did we conduct? 

G. What analysis of children’s 

environmental health did we conduct? 

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 14094: Modernizing Regulatory 

Review 

B. Paperwork Reduction Act (PRA) 

C. Regulatory Flexibility Act (RFA) 

D. Unfunded Mandates Reform Act 

(UMRA) 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer and 

Advancement Act (NTTAA) and 1 CFR 

Part 51 

J. Executive Order 12898: Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations and Executive Order 14096: 

Revitalizing Our Nation’s Commitment 

to Environmental Justice for All 

I. General Information 

A. Does this action apply to me? 

This action applies to the PEPO 

Production source category (and whose 

facilities, sources, and processes we 

often refer to as ‘‘PEPO’’ for purposes of 

the NESHAP). The PEPO NESHAP is 

codified at 40 CFR part 63, subpart PPP. 

The North American Industry 

Classification System (NAICS) code for 

PEPO facilities is 325199, although this 

is not intended to be exhaustive but 

rather to provide a guide for readers 

regarding the entities that this proposed 

action is likely to affect. The proposed 

standards, once promulgated, will be 

directly applicable to the affected 

sources. Federal, State, local, and Tribal 

government entities would not be 

affected by this proposed action. As 

defined in the Initial List of Categories 

of Sources Under Section 112(c)(1) of 

the Clean Air Act Amendments of 1990 

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

Documentation for Developing the 

Initial Source Category List, Final 

Report (see EPA–450/3–91–030, July 

1992), the PEPO Production source 

category is any facility which 

‘‘manufactures these polymers by 

starting with cyclic ethers (e.g., oxides, 

epoxides) and initiating polymerization 

by adding ethylene oxide, butylene 

oxide, propylene oxide or other 

chemicals which would result in the 

potential emission of HAPs. The 

reaction is base-catalyzed, with 

potassium hydroxide being the most 

commonly used catalyst. The physical 


jspears on DSK121TN23PROD with PROPOSALS
Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 105989 

1Although 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. 

properties of the polyols are influenced 

primarily by the functionality of the 

initiator molecules and by the type and 

quantity of alkylene oxide and hydroxyl 

groups present in the polyol.’’ In the 

development of NESHAP for this source 

category, the EPA considered emission 

sources associated with equipment leaks 

(including leaks from heat exchange 

systems), process vents, storage vessels, 

and wastewater collection and treatment 

systems. 

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. In 

accordance with 5 U.S.C. 553(b)(4), a 

brief summary of this rulemaking may 

be found at https://www.regulations.gov, 

Docket ID No. EPA–HQ–OAR–2023– 

0282. Following signature by the EPA 

Administrator, the EPA will post a copy 

of this proposed action at https:// 

www.epa.gov/stationary-sources-airpollution/polyether-polyols-productionnational-emission-standards-hazardous. 

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. 

A memorandum showing the edits 

that would be necessary to incorporate 

the changes to the PEPO NESHAP (40 

CFR part 63, subpart PPP) proposed in 

this action is available in the docket 

(Docket ID No. EPA–HQ–OAR–2023– 

0282). Following signature by the EPA 

Administrator, the EPA also will post a 

copy of this document to https:// 

www.epa.gov/stationary-sources-airpollution/polyether-polyols-productionnational-emission-standards-hazardous. 

II. Background 

A. What is the statutory authority for 

this action? 

1. NESHAP 

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 

and revise the standards as necessary 

taking into account any ‘‘developments 

in practices, processes, or control 

technologies.’’ This review is commonly 

referred to as the ‘‘technology review.’’ 

When the two reviews are combined 

into a single rulemaking, it is commonly 

referred to as the ‘‘risk and technology 

review.’’ The discussion that follows 

identifies the most relevant statutory 

sections and briefly explains the 

contours of the methodology used to 

implement these statutory requirements. 

A more comprehensive discussion 

appears in the document titled CAA 

Section 112 Risk and Technology 

Reviews: Statutory Authority and 

Methodology, in the docket for this 

rulemaking. 

In the first stage of the CAA section 

112 standard setting process, the EPA 

promulgates technology-based standards 

under CAA section 112(d) for categories 

of sources listed under section 112(c) 

and 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 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,’’ that the EPA must 

establish without consideration of costs. 

Under CAA section 112(d)(2), the EPA 

must also consider control options that 

are more stringent than the floor, taking 

into consideration costs, non-air quality 

health and environmental impacts, and 

energy requirements. Standards more 

stringent than the floor are commonly 

referred to as ‘‘beyond-the-floor’’ or 

‘‘BTF’’ standards. In certain instances, 

as provided in CAA section 112(h), the 

EPA may set work practice standards in 

lieu of numerical emission standards. 

For area sources, CAA section 112(d)(5) 

gives the EPA discretion to set standards 

based on generally available control 

technologies or management practices 

(GACT standards) in lieu of MACT 

standards. 

The second stage in standard-setting 

focuses on identifying and addressing 

any remaining (i.e., ‘‘residual’’) risk 

pursuant to CAA section 112(f). For 

source categories subject to MACT 

standards, section 112(f)(2) of the CAA 

requires the EPA to determine whether 

promulgation of additional standards is 

needed to provide an ample margin of 

safety to protect public health or to 

prevent an adverse environmental 

effect. Section 112(d)(5) of the CAA 

provides that this residual risk review is 

not required for categories of area 

sources subject to GACT standards. 

Section 112(f)(2)(B) of the CAA further 

expressly preserves the EPA’s use of the 

two-step approach for developing 

standards to address any residual risk 

and the Agency’s interpretation of 

‘‘ample margin of safety’’ developed in 

the National Emissions Standards for 

Hazardous Air Pollutants: Benzene 

Emissions from Maleic Anhydride 

Plants, Ethylbenzene/Styrene Plants, 

Benzene Storage Vessels, Benzene 

Equipment Leaks, and Coke By-Product 

Recovery Plants (Benzene NESHAP) (54 

FR 38044, September 14, 1989). The 

EPA notified Congress in the Residual 

Risk Report that the Agency intended to 

use the Benzene NESHAP approach in 

making CAA section 112(f) residual risk 

determinations (EPA–453/R–99–001, p. 

ES–11). The EPA subsequently adopted 

this approach in its residual risk 

determinations and the United States 

Court of Appeals for the District of 

Columbia Circuit affirmed that CAA 

section 112(f)(2) incorporates the 

approach established in the Benzene 

NESHAP. See Natural Resources 

Defense Council (NRDC) v. EPA, 529 

F.3d 1077, 1083 (D.C. Cir. 2008). 

The approach incorporated into the 

CAA and used by the EPA to evaluate 

residual risk and to develop standards 

under CAA section 112(f)(2) is a twostep approach. In the first step, the EPA 

determines whether risks are acceptable. 

This determination ‘‘considers all health 

information, including risk estimation 

uncertainty, and includes a presumptive 

limit on maximum individual lifetime 

[cancer] risk (MIR) 1 of approximately 1 

in 10 thousand.’’ (54 FR 38045). If risks 

are unacceptable, the EPA must 

determine the emissions standards 

necessary to reduce risk to an acceptable 

level without considering costs. In the 

second step of the approach, the EPA 


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105990 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

2U.S. EPA. Evaluation of the Inhalation 

Carcinogenicity of Ethylene Oxide (CASRN 75–21– 

8) In Support of Summary Information on the 

Integrated Risk Information System (IRIS). 

December 2016. EPA/635/R–16/350Fa. Available at: 

https://cfpub.epa.gov/ncea/iris/iris_documents/ 

documents/toxreviews/1025tr.pdf. See also, 87 FR 

77985 (Dec. 21, 2022), Reconsideration of the 2020 

National Emission Standards for Hazardous Air 

Pollutants: Miscellaneous Organic Chemical 

Manufacturing Residual Risk and Technology 

Review, Final action; reconsideration of the final 

rule. 

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. 

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 floors 

that were established during earlier 

rulemakings. NRDC v. EPA, 529 F.3d at 

1084 (D.C. Cir. 2008); Association of 

Battery Recyclers, Inc. v. EPA, 716 F.3d 

667 (D.C. Cir. 2013). The EPA may 

consider cost in deciding whether to 

revise the standards pursuant to CAA 

section 112(d)(6). The EPA is required 

to address regulatory gaps, such as 

missing MACT standards for listed air 

toxics known to be emitted from the 

source category. Louisiana 

Environmental Action Network (LEAN) 

v. EPA, 955 F.3d 1088 (D.C. Cir. 2020). 

The EPA conducted a residual risk 

and technology review (RTR) for the 

PEPO NESHAP in 2014, concluding that 

there was no need to revise the PEPO 

NESHAP under the provisions of either 

CAA sections 112(f) or (d)(6). However, 

the EPA did address emissions during 

periods of startup, shutdown, and 

malfunction (SSM), including from 

pressure relief devices (PRDs) in organic 

HAP service that release to the 

atmosphere, and also required 

electronic reporting of performance test 

results (see 79 FR 17340, March 27, 

2014). As part of the 2014 residual risk 

review, the EPA conducted a risk 

assessment, and based on the results of 

the risk assessment, determined that the 

then current level of control called for 

by the existing MACT standards both 

reduced HAP emissions to levels that 

presented an acceptable level of risk and 

provided an ample margin of safety to 

protect public health. 

This action constitutes another CAA 

section 112(d)(6) technology review for 

the PEPO NESHAP. This action also 

constitutes an updated CAA section 

112(f) risk review based on new 

information for the PEPO NESHAP. As 

noted above, CAA section 112(f)(2)(A) 

requires the EPA to promulgate 

standards that ‘‘provide an ample 

margin of safety to protect public 

health’’ and prevent ‘‘an adverse 

environmental effect.’’ While CAA 

section 112(f) does not require the EPA 

to periodically revisit a residual risk 

review, neither does it preclude the EPA 

from exercising its inherent authority to 

revisit a previous regulatory decision 

where new scientific, technical, or other 

relevant information indicates such 

action is warranted. Moreover, the Act 

does include a gap-filling provision that 

reinforces the authority for the EPA to 

do so. CAA section 301(a)(1) provides 

authority to the Administrator ‘‘to 

prescribe such regulations as are 

necessary to carry out his functions’’ 

under the CAA. Such authority extends 

to the EPA’s discretion to revisit its 

section 112(f) residual risk review 

where the Agency deems warranted. See 

NRDC v. EPA, 22 F.3d 1125, 1148 (D.C. 

Cir. 1994) (‘‘[Section 301] is sufficiently 

broad to allow the promulgation of rules 

that are necessary and reasonable to 

effect the purposes of the Act.’’). We 

note that although there is no statutory 

CAA obligation under CAA section 

112(f) for the EPA to conduct a second 

residual risk review of the PEPO 

NESHAP, the EPA retains discretion to 

revisit its residual risk reviews where 

the Agency deems that it is warranted. 

See, e.g., Fed. Commc’ns Comm’n v. Fox 

Television Stations, Inc., 556 U.S. 502, 

515 (2009); Motor Vehicle Mfrs. Ass’n v. 

State Farm Mut. Auto. Ins. Co., 463 U.S. 

29, 42 (1983); Ethylene Oxide Emissions 

Standards for Sterilization Facilities; 

Final Decision, 71 FR 17712, 17715 col. 

1 (April 7, 2006) (in the 2006 residual 

risk review of the EtO emissions 

standards for sterilization facilities, the 

EPA asserted its ‘‘authority to revisit 

(and revise, if necessary) any 

rulemaking if there is sufficient 

evidence that changes within the 

affected industry or significant 

improvements to science suggests the 

public is exposed to significant 

increases in risk as compared to the risk 

assessment prepared for the rulemaking 

(e.g., CAA section 301).’’). Here, the 

specific changes to health information 

related to a certain pollutant emitted by 

the PEPO Production source category 

led us to determine that it is 

appropriate, in this case, to conduct this 

second residual risk review under CAA 

section 112(f). In particular, the EPA is 

concerned about the cancer risks posed 

from the PEPO Production source 

category based on the EPA’s 2016 

updated Integrated Risk Information 

System (IRIS) inhalation unit risk 

estimate (URE) for EtO, which shows 

EtO to be significantly more toxic than 

previously known.2 The EPA’s 2014 

RTR could not have had the benefit of 

this updated URE at the time it was 

conducted, but if it had the RTR would 

have necessarily resulted in different 

conclusions about risk acceptability and 

the PEPO NESHAP’s provision of an 

ample margin of safety to protect public 

health. To ensure our standards provide 

an ample margin of safety to protect 

public health following the new IRIS 

inhalation URE for EtO, we are 

exercising our discretion and 

conducting a risk assessment in this 

action for PEPO Production sources. In 

sum, even though we do not have a 

mandatory duty to conduct repeated 

residual risk reviews under CAA 

sections 112(f)(2) and 301(a)(1), we have 

the authority to revisit any rulemaking 

if there is sufficient evidence of changes 

within the affected industry or 

significant new scientific information 

suggesting the public is exposed to 

higher risks than previously understood. 

Our conducting a discretionary second 

residual risk review for the PEPO 

Production source category to account 

for the new IRIS inhalation URE for EtO 

is consistent with recent similar actions 

regarding other source categories. See 89 

FR 24090, April 5, 2024, and 89 FR 

42932, May 16, 2024. 

2. Petition for Reconsideration 

In addition to the proposed action 

under sections 112 and 301 of the CAA 

described above, this action includes 

proposed amendments to the PEPO 

NESHAP based on the EPA’s 

reconsideration of certain aspects of the 

NESHAP that were raised in an 

administrative petition submitted 

pursuant to section 307(d)(7)(B) of the 

CAA. In May 2014, the EPA received 

one petition for reconsideration of the 

PEPO NESHAP (40 CFR part 63, subpart 


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3Although the issues identified in this paragraph 

(in addition to one other issue related to alternative 

compliance demonstration methods for periods of 

startup and shutdown) were also raised for 40 CFR 

part 63, subparts JJJ and MMM; this action does not 

respond to the reconsideration of these NESHAP, as 

the EPA is not reviewing these subparts in this 

action. 

4PEPO are compounds formed through the 

polymerization of EtO or propylene oxide or other 

cyclic ethers with compounds having one or more 

reactive hydrogens (i.e., a hydrogen atom bonded to 

nitrogen, oxygen, phosphorus, sulfur, etc.) to form 

polyethers (i.e., compounds with two or more ether 

bonds). This definition of PEPO excludes cellulose 

ethers (such as methyl cellulose, carboxymethyl 

cellulose, hydroxyethyl cellulose, hydroxy ethyl 

cellulose, and hydroxypropyl methyl cellulose) and 

materials regulated under the HON, such as glycols 

and glycol ethers. 

5A PMPU also includes flexible operation 

process units when an owner or operator cannot 

determine that a PEPO is not the primary product, 

and a PEPO is produced or anticipated to be 

produced during time spans described in 40 CFR 

63.1420(e)(2). 

PPP), Pesticide Active Ingredient 

Production NESHAP (40 CFR part 63, 

subpart MMM), and Group IV Polymers 

and Resins NESHAP (40 CFR part 63, 

subpart JJJ) pursuant to CAA section 

307(d)(7)(B) from the Louisiana 

Environmental Action Network, Ohio 

Valley Environmental Coalition, and 

Sierra Club. A copy of the petition and 

subsequent EPA correspondence 

granting reconsideration is provided in 

the docket for this rulemaking (see 

Docket No. EPA–HQ–OAR–2023–0282). 

For the PEPO NESHAP, the 

petitioners requested that the EPA: (1) 

remove the affirmative defense 

provisions from the rules in light of the 

court opinion in Natural Resources 

Defence Council v. EPA (D.C. Cir. April 

18, 2014); (2) provide adequate 

opportunity to comment on the 

requirements associated with emissions 

from PRDs (including associated 

compliance dates, the EPA’s decision to 

not specifically require electronic 

indicators and alarms to monitor PRD 

releases to the atmosphere, and the 

standard’s applicability to PRDs in 

organic HAP service versus PRDs in 

total HAP service); (3) redo the risk 

assessment using updated emission 

factors; (4) set additional monitoring 

requirements for flares to reduce flaring 

emissions; (5) set fenceline monitoring 

requirements; (6) reconsider its decision 

not to set standards that account for 

developments in leak detection and 

repair (LDAR); and (7) use existing 

regulatory authority to strengthen 

chemical facility safety and prevent 

accidents in accordance with the U.S. 

Chemical Safety and Hazard 

Investigation Board and Executive Order 

13650. On August 26, 2014, the EPA 

sent a letter to the petitioners informing 

them that the EPA was granting their 

request for reconsideration at least on 

issues (1) and (2) above. A copy of the 

August 26, 2014, letter is provided in 

the docket for this rulemaking (see 

Docket No. EPA–HQ–OAR–2023–0282). 

In the letter, the EPA also indicated that 

it would be initiating a notice and 

comment rulemaking on the issues for 

which we granted reconsideration; 

therefore, one purpose of this action is 

to formally respond to the issues raised 

in the petition with respect to the PEPO 

NESHAP.3

In a separate rulemaking (see 89 FR 

52425, June 24, 2024), the EPA is 

addressing issue (1), the affirmative 

defense against civil penalties for 

violations occurring during 

malfunctions. That separate rulemaking 

removes affirmative defense provisions 

from both NSPS and NESHAP rules, 

including the PEPO NESHAP. 

Therefore, this proposed action does not 

address removal of the affirmative 

defense provisions. 

This action presents the EPA’s 

proposed revisions to the PEPO 

NESHAP based on the EPA’s 

reconsideration of issue (2) in the 

petition (see section IV.E.1 of this 

preamble for details about these 

proposed amendments). Coincidentally, 

we also believe this action addresses 

issues (3), (4), (5), and (6) in our normal 

course of review of the PEPO NESHAP 

in accordance with sections 112 and 301 

of the CAA. See sections IV.A and IV.B 

of this preamble for our proposed 

decisions relvant to issue (3), section 

IV.D.1 of this preamble for our proposed 

decisions relevant to issue (4), section 

IV.C.6 of this preamble for our proposed 

decisions relevant to issue (5), and 

sections IV.B.2.b and IV.C.5 of this 

preamble for our proposed decisions 

relevant to issue (6). With regard to 

issue (7), the EPA’s authority to address 

catastrophic releases under the NESHAP 

program was viewed as limited under 

the pre-1990 CAA. Congress added CAA 

section 112(r) to address this gap. In 

light of the extensive history and efforts 

of the agency on inherently safer 

technology specifically and catastrophic 

accidents generally under the section 

112(r) program, and in light of the 

statutory structure of section 112, we 

view the request to enact such 

provisions in this rulemaking to be 

outside the scope of section 112(f)(2) 

and section 112(d)(6). We note that the 

EPA’s regulations on catastrophic 

releases appear in 40 CFR part 68. 

Prompted by Executive Order 13650, 

‘‘Improving Chemical Facility Safety 

and Security,’’ the Risk Management 

Program regulations were amended on 

January 13, 2017, to include new 

provisions on safer technology and 

alternatives analysis and other 

prevention program elements; most 

recently, the regulations were amended 

on March 11, 2024, to further enhance 

the accident prevention and emergency 

preparedness requirements (89 FR 

17622). 

B. What is the source category and how 

do the current standards regulate its 

HAP emissions? 

The source category that is the subject 

of this proposal is the PEPO Production 

source category subject to the PEPO 

NESHAP. The EPA promulgated the 

PEPO NESHAP on June 1, 1999 (64 FR 

29420), and codified the NESHAP at 40 

CFR part 63, subpart PPP. As 

promulgated in 1999, and further 

amended on July 1, 2004 (69 FR 39862) 

and March 27, 2014 (59 FR 17340), the 

PEPO NESHAP regulates HAP 

emissions from polyether polyol 

manufacturing process units (PMPUs) 

that produce PEPO as its primary 

product.4 5 A PMPU consists of 

purification systems, reactors and their 

associated product separators and 

recovery devices, distillation units and 

their associated distillate receivers and 

recovery devices, other associated unit 

operations, storage vessels, surge control 

vessels, bottoms receivers, product 

transfer racks, connected ducts and 

piping, combustion, recovery, or 

recapture devices or systems. A PMPU 

also includes pumps, compressors, 

agitators, PRDs, sampling connection 

systems, open-ended valves or lines, 

valves, connectors, and instrumentation 

systems. 

PEPO are used to make a variety of 

other products including lubricants, 

adhesives, sealants, cosmetics, 

pharmaceuticals, soaps, and a feedstock 

for polyurethanes production. Urethane 

grade PEPO (i.e., those that are free of 

water) are used as raw material in the 

production of polyurethanes, including 

slabstock and molded flexible foams, 

rigid foams and other polyurethanes, 

including microcellular products, 

surface coatings, elastomers, fibers, 

adhesives, and sealants. 

PEPO can be produced by either 

polymerization of epoxides (i.e., a threemembered cyclic ether, such as EtO or 

propylene oxide) or tetrahydrofuran 

(THF). The former process is usually 

conducted as a batch process, while 

production of polyols using THF is 

generally a continuous process. EtO and 

propylene oxide are both HAP, but THF 

is not. For the MACT regulation, the 

EPA created two subcategories of PEPO 

based on the use of either epoxides or 

THF in polymerization. 


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6https://www.epa.gov/hazardous-air-pollutantsethylene-oxide/inspector-general-follow-ethyleneoxide-0. 

The HAP emission sources at PEPO 

facilities include process vents, storage 

vessels, equipment leaks, and 

wastewater. Additionally, some 

facilities have cooling towers or other 

heat exchangers which could become 

HAP emission sources if process fluids 

leak into the heat exchange water. In the 

production of PEPO, HAP are used 

primarily as reactants or extraction 

solvents. HAP emitted from PEPO 

facilities include EtO, propylene oxide, 

toluene, methanol, and glycol ethers. 

The MACT standards for PEPO 

production include emission limits for 

process vents; a combination of 

equipment standards and work practices 

for storage vessels, wastewater, and 

equipment leaks; and work practice 

standards for cooling towers. 

As of March 1, 2024, the EPA 

identified 25 PEPO facilities in 

operation that are subject to the PEPO 

NESHAP. The list of facilities located in 

the United States that are part of the 

PEPO Production source category with 

processes subject to the PEPO NESHAP 

is presented in the document titled List 

of Facilities Subject to the PEPO 

NESHAP, which is available in the 

docket for this action (Docket ID No. 

EPA–HQ–OAR–2023–0282). 

C. What data collection activities were 

conducted to support this action? 

The EPA used several data sources to 

determine the facilities that are subject 

to the PEPO NESHAP discussed in 

section II.B of this preamble. We 

identified facilities in the 2017 National 

Emissions Inventory (NEI) and the 

Toxics Release Inventory system having 

a primary facility NAICS code beginning 

with 325, Chemical Manufacturing. We 

also used information from the 2014 

PEPO NESHAP RTR, other facility lists 

from the EPA’s recent chemical sector 

rulemakings (e.g., HON), and the Office 

of Enforcement and Compliance 

Assurance’s Enforcement and 

Compliance History Online (ECHO) tool 

(https://echo.epa.gov). To inform our 

reviews of the Agency’s emission 

standards, we reviewed the EPA’s 

Reasonably Available Control 

Technology (RACT)/Best Available 

Control Technology (BACT)/Lowest 

Achievable Emission Rate (LAER) 

Clearinghouse and regulatory 

development efforts for similar sources 

published after the PEPO NESHAP was 

developed. The EPA also reviewed air 

emissions permits issued by State 

regulatory agencies to determine 

facilities subject to the PEPO NESHAP. 

Additionally, we met with industry 

representatives from the American 

Chemistry Council (ACC) to collect data 

and discuss industry practices. 

In January 2022, the EPA issued 

requests, pursuant to CAA section 114, 

to collect information from synthetic 

organic chemical manufacturing 

industry (SOCMI) facilities subject to 

the hazardous organic NESHAP (HON) 

at 40 CFR part 63, subparts F, G, and H 

(nine facilities being also subject to the 

PEPO NESHAP) owned and operated by 

eight entities (i.e., corporations). Many 

of the entities chosen for the CAA 

section 114 request own or operate 

facilities that produce, use, and emit 

EtO, which is a pollutant with 

considerable concern for cancer risk for 

the PEPO Production source category. 

This CAA section 114 request focused 

on gathering comprehensive 

information about process equipment, 

control technologies, point and fugitive 

emissions, and other aspects of facility 

operations. Additionally, the EPA 

requested stack testing for certain 

emission sources (e.g., pollutants for 

vent streams associated with each EtO 

production line). Also, the EPA 

required, as part of the January 2022 

CAA section 114 request, that facilities 

conduct fugitive emission testing (i.e., 

fenceline monitoring) for any of six 

specific HAP they emit: benzene; 1,3- 

butadiene; chloroprene; EtO; ethylene 

dichloride; and vinyl chloride. 

Companies submitted responses (and 

follow-up responses) and testing results 

to the EPA during the summer and fall 

of 2022. The EPA used the collected 

information to fill data gaps, establish 

the baseline emissions and control 

levels for purposes of the regulatory 

reviews, identify the most effective 

control measures, and estimate the 

public health and environmental and 

cost impacts associated with the 

regulatory options considered and 

reflected in this proposed action. The 

information not claimed as CBI by 

respondents is available in the 

document titled Data Received from 

Information Collection Request for 

Chemical Manufacturers, in the docket 

for this action, Docket ID No. EPA–HQ– 

OAR–2023–0282. 

D. What other relevant background 

information and data are available? 

As mentioned above, this action 

includes proposed amendments to the 

current flare requirements in the PEPO 

NESHAP. In proposing these 

amendments, we relied on certain 

technical reports and memoranda that 

the EPA developed for flares used as air 

pollution control devices (APCDs) in the 

Petroleum Refinery Sector RTR and new 

source performance standards (NSPS) 

rulemaking (80 FR 75178, December 1, 

2015). The Petroleum Refinery Sector 

rulemaking docket is at Docket ID No. 

EPA–HQ–OAR–2010–0682. For 

completeness of the rulemaking record 

for this action and for ease of reference 

in finding these items in the publicly 

available Petroleum Refinery Sector 

rulemaking docket, we are including the 

most relevant flare-related technical 

support documents in the docket for 

this proposed action (Docket ID No. 

EPA–HQ–OAR–2023–0282) and 

including a list of all documents used to 

inform the 2015 flare provisions in the 

Petroleum Refinery Sector RTR and 

NSPS rulemaking in the document titled 

Control Option Impacts for Flares in the 

PEPO Production Source Category that 

Control Emissions from Processes 

Subject to the PEPO NESHAP, which is 

available in the docket for this 

rulemaking. 

We are also relying on data gathered 

to support the rulemakings for the 

EMACT standards, HON, and MON, as 

well as memoranda documenting the 

technology reviews for those processes. 

Many of the emission sources for 

ethylene production facilities, HON 

facilities, and MON facilities are similar 

to PEPO facilities, so the EPA analyzed 

several control options for the PEPO 

NESHAP that the Agency also analyzed 

for the rulemakings for the EMACT 

standards, HON, and MON. The 

memoranda and background technical 

information can be found in the 

Ethylene Production RTR rulemaking 

docket (Docket ID No. EPA–HQ–OAR– 

2017–0357), the HON rulemaking 

docket (Docket ID No. EPA–HQ–OAR– 

2022–0730), and the MON RTR 

rulemaking docket (Docket ID No. EPA– 

HQ–OAR–2018–0746). Additional 

information related to the promulgation 

and subsequent amendments of the 

PEPO NESHAP is available in Docket ID 

Nos. A–96–38, EPA–HQ–OAR–2004– 

0467, and EPA–HQ–OAR–2011–0435. 

E. What outreach was conducted? 

We conducted pre-proposal outreach 

by sharing an overview of the industry 

and planned rulemaking to the EPA’s 

national environmental justice (EJ) 

engagement call on August 20, 2024, 

and the EPA’s monthly call with the 

National Tribal Air Association on 

August 31, 2023, and August 29, 2024. 

We also met with members of the ACC 

on August 13, 2024. The EPA also 

previously engaged in outreach 

activities with communities we 

expected to be impacted by chemical 

plants emitting EtO in 2021.6


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7The 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 doseresponse value; the HI is the sum of HQs for HAP 

that affect the same target organ or organ system. 

8Recommendations of the SAB Risk and 

Technology Review Methods Panel are provided in 

their report, which is available at: https:// 

www.epa.gov/sites/default/files/2021-02/ 

documents/epa-sab-10-007-unsigned.pdf. 

III. Analytical Procedures and 

Decision-Making 

A. How do we consider risk in our 

decision-making? 

As discussed in section II.A of this 

preamble and in the Benzene NESHAP, 

in evaluating and developing standards 

under CAA section 112(f)(2), we apply 

a two-step approach to determine 

whether or not risks are acceptable and 

to determine if the standards provide an 

ample margin of safety to protect public 

health. As explained in the Benzene 

NESHAP, ‘‘the first step judgment on 

acceptability cannot be reduced to any 

single factor’’ and, thus, ‘‘[t]he 

Administrator believes that the 

acceptability of risk under section 112 is 

best judged on the basis of a broad set 

of health risk measures and 

information.’’ (54 FR 38046). Similarly, 

with regard to the ample margin of 

safety determination, ‘‘the Agency again 

considers all of the health risk and other 

health information considered in the 

first step. Beyond that information, 

additional factors relating to the 

appropriate level of control will also be 

considered, including cost and 

economic impacts of controls, 

technological feasibility, uncertainties, 

and any other relevant factors.’’ Id. 

The Benzene NESHAP approach 

provides flexibility regarding factors the 

EPA may consider in making 

determinations and how the EPA may 

weigh those factors for each source 

category. The EPA conducts a risk 

assessment that provides estimates of 

the MIR posed by emissions of HAP that 

are carcinogens from each source in the 

source category, the hazard index (HI) 

for chronic exposures to HAP with the 

potential to cause noncancer health 

effects, and the hazard quotient (HQ) for 

acute exposures to HAP with the 

potential to cause noncancer health 

effects.7 The assessment also provides 

estimates of the distribution of cancer 

risk within the exposed populations, 

cancer incidence, and an evaluation of 

the potential for an adverse 

environmental effect. The scope of the 

EPA’s risk analysis is consistent with 

the explanation in the EPA’s response to 

comments on our policy under the 1989 

Benzene NESHAP: 

The policy chosen by the Administrator 

permits consideration of multiple measures 

of health risk. Not only can the MIR figure 

be considered, but also incidence, the 

presence of non-cancer health effects, and the 

uncertainties of the risk estimates. In this 

way, the effect on the most exposed 

individuals can be reviewed as well as the 

impact on the general public. These factors 

can then be weighed in each individual case. 

This approach complies with the Vinyl 

Chloride mandate that the Administrator 

ascertain an acceptable level of risk to the 

public by employing his expertise to assess 

available data. It also complies with the 

Congressional intent behind the CAA, which 

did not exclude the use of any particular 

measure of public health risk from the EPA’s 

consideration with respect to CAA section 

112 regulations, and thereby implicitly 

permits consideration of any and all 

measures of health risk which the 

Administrator, in his judgment, believes are 

appropriate to determining what will 

‘‘protect the public health’’. 

(54 FR 38057). Thus, the level of the 

MIR is only one factor to be weighed in 

determining acceptability of risk. The 

Benzene NESHAP explained that ‘‘an 

MIR of approximately one in 10 

thousand should ordinarily be the upper 

end of the range of acceptability. As 

risks increase above this benchmark, 

they become presumptively less 

acceptable under CAA section 112, and 

would be weighed with the other health 

risk measures and information in 

making an overall judgment on 

acceptability. Or, the Agency may find, 

in a particular case, that a risk that 

includes an MIR less than the 

presumptively acceptable level is 

unacceptable in the light of other health 

risk factors.’’ Id. at 38045. In other 

words, risks that include an MIR above 

100-in-1 million (1-in-10 thousand) 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 1989 Benzene 

NESHAP that: ‘‘EPA believes the 

relative weight of the many factors that 

can be considered in selecting an ample 

margin of safety can only be determined 

for each specific source category. This 

occurs mainly because technological 

and economic factors (along with the 

health-related factors) vary from source 

category to source category.’’ Id. at 

38061. We also consider the 

uncertainties associated with the 

various risk analyses, as discussed 

earlier in this preamble, in our 

determinations of acceptability and 

ample margin of safety. 

The EPA notes that it has not 

considered certain health information to 

date in making residual risk 

determinations. At this time, we do not 

attempt to quantify the HAP risk that 

may be associated with emissions from 

other facilities that do not include the 

source category under review, mobile 

source emissions, natural source 

emissions, persistent environmental 

pollution, or atmospheric 

transformation in the vicinity of the 

sources in the category. 

The EPA understands the potential 

importance of considering an 

individual’s total exposure to HAP in 

addition to considering exposure to 

HAP emissions from the source category 

and facility. We recognize that such 

consideration may be particularly 

important when assessing noncancer 

risk, where pollutant-specific exposure 

health reference levels (e.g., reference 

concentrations (RfCs)) are based on the 

assumption that thresholds exist for 

adverse health effects. For example, the 

EPA recognizes that, although exposures 

attributable to emissions from a source 

category or facility alone may not 

indicate the potential for increased risk 

of adverse noncancer health effects in a 

population, the exposures resulting 

from emissions from the facility in 

combination with emissions from all of 

the other sources (e.g., other facilities) to 

which an individual is exposed may be 

sufficient to result in an increased risk 

of adverse noncancer health effects. In 

May 2010, the Science Advisory Board 

(SAB) advised the EPA ‘‘that RTR 

assessments will be most useful to 

decision makers and communities if 

results are presented in the broader 

context of aggregate and cumulative 

risks, including background 

concentrations and contributions from 

other sources in the area.’’ 8

In response to the SAB 

recommendations, the EPA incorporates 

cumulative risk analyses into its RTR 

risk assessments. The Agency: (1) 

conducts facility-wide assessments, 

which include source category emission 

points, as well as other emission points 

within the facilities; (2) combines 

exposures from multiple sources in the 

same category that could affect the same 

individuals; and (3) for some persistent 

and bioaccumulative pollutants, 

analyzes the ingestion route of 

exposure. In addition, the RTR risk 

assessments consider aggregate cancer 

risk from all carcinogens and aggregated 

noncancer HQs for all noncarcinogens 

affecting the same target organ or target 

organ system. 

Although we are interested in placing 

source category and facility-wide HAP 

risk in the context of total HAP risk 

from all sources combined in the 


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9U.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. 

10For more information about HEM–4, go to 

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

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. While we 

evaluated the risk from HAP emitted by 

all stationary point sources near 

facilities within this source category in 

the community-based risk assessment, 

that assessment is intended to provide 

additional context to the public and was 

not used for decision-making in this 

proposed rule. 

B. 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 nine 

sections that follow this paragraph 

describe how we estimated emissions 

and conducted the risk assessment. The 

docket for this rulemaking contains the 

following document which provides 

more information on the risk assessment 

inputs and models: Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule. The 

methods used to assess risk (as 

described in the nine 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; 9 and described in the SAB 

review report issued in 2010. They are 

also consistent with the key 

recommendations contained in that 

report. 

1. How did we estimate actual 

emissions and identify the emissions 

release characteristics? 

As previously discussed, we updated 

the risk assessment in this action for the 

PEPO Production source category 

because the source category has sources 

that emit EtO. The EPA developed the 

list of 25 facilities for the PEPO 

Production source category as described 

in section II.B of this preamble. We 

developed the emissions modeling 

input files using the EPA’s 2017 NEI. 

However, in a few instances where 

facility-specific data were not available 

or not reflective of current controls in 

the 2017 NEI, we obtained data from a 

more recent dataset (e.g., review of 

emissions inventory data from our CAA 

section 114 request, more recent 

inventories submitted to States, or 2018 

NEI). The EPA also used the NEI data to 

develop the other parameters needed to 

perform the risk modeling analysis 

including the emissions release 

characteristics, such as stack heights, 

stack diameters, volumetric flow rates, 

temperatures, and emission release 

point locations. For further details on 

the assumptions and methodologies 

used to estimate actual emissions, see 

appendix 1 of the document titled 

Residual Risk Assessment for the 

Polyether Polyols (PEPO) Production 

Source Category in Support of the 2024 

Risk and Technology Review Proposed 

Rule, which is available in the docket 

for this rulemaking. 

2. How did we estimate MACTallowable 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 2005 final RTR for Coke Oven 

Batteries (70 FR 19992, 19998–99, April 

15, 2005) and in the 2006 proposed and 

final RTR for the HON (71 FR 34421, 

34428, June 14, 2006, and 71 FR 76603, 

76609, December 21, 2006, 

respectively). In those actions, we noted 

that assessing the risk at the MACTallowable 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.) 

For this analysis, we have determined 

that the actual emissions data are 

reasonable estimates of the MACTallowable emissions levels for the PEPO 

Production source category, as we are 

not generally aware of any situations in 

which a facility is conducting additional 

work practices or operating a control 

device such that it achieves a far greater 

emission reduction than required by the 

NESHAP. However, in cases where we 

encountered a permit emissions limit 

that appeared to be higher than the 

reported emissions, we recorded that in 

the allowable emissions column of the 

modeling file to assess the risk of 

allowable emissions. For further details 

on the assumptions and methodologies 

used to estimate MACT-allowable 

emissions, see appendix 1 of the 

document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

3. How do we conduct dispersion 

modeling, determine inhalation 

exposures, and estimate individual and 

population inhalation risk? 

Both long-term and short-term 

inhalation exposure concentrations and 

health risk from the source category 

addressed in this proposal were 

estimated using the Human Exposure 

Model (HEM–4).10 The HEM–4 performs 

three primary risk assessment activities: 

(1) conducting dispersion modeling to 

estimate the concentrations of HAP in 

ambient air, (2) estimating long-term 

and short-term inhalation exposures to 

individuals residing within 50 

kilometers (km) of the modeled sources, 

and (3) estimating individual and 

population-level inhalation risk using 

the exposure estimates and quantitative 

dose-response information. 


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11U.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). 12A census block is the smallest geographic area 

for which census statistics are tabulated. 

13The 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 Nationalscale Air Toxics Assessment 1996 Data—an SAB 

Advisory, available at https://yosemite.epa.gov/sab/ 

sabproduct.nsf/214C6E915BB04E1485

2570CA007A682C/$File/ecadv02001.pdf. 

a. Dispersion Modeling 

The air dispersion model AERMOD 

(American Meteorological Society/EPA 

Regulatory Model dispersion modeling 

system), used by the HEM–4, is one of 

the EPA’s preferred models for assessing 

air pollutant concentrations from 

industrial facilities.11 To perform the 

dispersion modeling and to develop the 

preliminary risk estimates, HEM–4 

draws on three data libraries. The first 

is a library of meteorological data, 

which is used for dispersion 

calculations. This library includes 1 

year (2019) of hourly surface and upper 

air observations from over 800 

meteorological stations, selected to 

provide coverage of the United States 

and Puerto Rico. A second library of 

United States Census Bureau census 

block 12 internal point locations and 

populations provides the basis of 

human exposure calculations (U.S. 

Census, 2020). 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. 

b. Risk From Chronic Exposure to HAP 

In developing the risk assessment for 

chronic exposures, we use the estimated 

annual average ambient air 

concentrations of each HAP emitted by 

each source in the source category. The 

HAP air concentrations at each nearby 

census block centroid located within 50 

km of the facility are a surrogate for the 

chronic inhalation exposure 

concentration for all the people who 

reside in that census block. A distance 

of 50 km is consistent with both the 

analysis supporting the 1989 Benzene 

NESHAP (54 FR 38044) and the 

limitations of Gaussian dispersion 

models, including AERMOD. 

For each facility, we calculate the MIR 

as the cancer risk associated with a 

continuous lifetime (24 hours per day, 

7 days per week, 52 weeks per year, 70 

years) exposure to the maximum annual 

average 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 (mg/m3)) by its 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 mg/m3

of air. For residual risk assessments, we 

generally use UREs from the EPA’s 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 doseresponse values have been developed in 

a manner consistent with EPA 

guidelines and have undergone a peer 

review process similar to that used by 

the EPA, we may use such doseresponse 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-assessinghealth-risks-associated-exposurehazardous-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 13 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. 

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=&vocab

Name=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) Minimal 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-hotspots-program-guidance-manualpreparation-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-responseassessment-assessing-health-risksassociated-exposure-hazardous-airpollutants. 

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 health protective 


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14See, 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). 

15 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 categoryspecific factor or a default factor of 10) to account 

for variability. This is documented in Residual Risk 

Assessment for the Polyether Polyols (PEPO) 

Production Source Category in Support of the 2024 

Risk and Technology Review Proposed Rule, and in 

appendix 5 of the report: Technical Support 

Document for Acute Risk Screening Assessment. 

Both of these documents are available in the docket 

for this rulemaking. 

16CalEPA 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-acute8-hour-and-chronic-reference-exposure-level-relsummary. 

17National 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). 

assumptions about emission rates, 

meteorology, and exposure location. As 

part of our efforts to continually 

improve our methodologies to evaluate 

the risks that HAP emitted from 

categories of industrial sources pose to 

human health and the environment,14

we revised our treatment of 

meteorological data to use reasonable 

worst-case air dispersion conditions in 

our acute risk screening assessments 

instead of worst-case air dispersion 

conditions. This revised treatment of 

meteorological data and the supporting 

rationale are described in more detail in 

the document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule and 

in appendix 5 of the report Technical 

Support Document for Acute Risk 

Screening Assessment, which are 

available in the docket for this 

rulemaking. This revised approach has 

been used in this proposed rule and in 

all other RTR rulemakings proposed on 

or after June 3, 2019. 

To assess the potential acute risk to 

the maximally exposed individual, we 

use the peak hourly emission rate for 

each emission point,15 reasonable 

worst-case air dispersion conditions 

(i.e., 99th percentile), and the point of 

highest off-site exposure. Specifically, 

we assume that peak emissions from the 

source category and reasonable worstcase air dispersion conditions co-occur 

and that a person is present at the point 

of maximum exposure. 

To characterize the potential health 

risks associated with estimated acute 

inhalation exposures to a HAP, we 

generally use multiple acute doseresponse 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.’’ 16

Acute RELs are based on the most 

sensitive, relevant, adverse health effect 

reported in the peer-reviewed medical 

and toxicological literature. They are 

designed to protect the most sensitive 

individuals in the population through 

the inclusion of margins of safety. 

Because margins of safety are 

incorporated to address data gaps and 

uncertainties, exceeding the REL does 

not automatically indicate an adverse 

health impact. AEGLs represent 

threshold exposure limits for the general 

public and are applicable to emergency 

exposures ranging from 10 minutes to 8 

hours.17 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/m3 (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. 

ERPGs are developed, by the 

American Industrial Hygiene 

Association (AIHA), for emergency 

planning and are intended to be healthbased guideline concentrations for 

single exposures to chemicals. The 

ERPG–1 is the maximum airborne 

concentration, established by AIHA, 

below which it is believed that nearly 

all individuals could be exposed for up 

to 1 hour without experiencing other 

than mild transient adverse health 

effects or without perceiving a clearly 

defined, objectionable odor. Similarly, 

the ERPG–2 is the maximum airborne 

concentration, established by AIHA, 

below which it is believed that nearly 

all individuals could be exposed for up 

to 1 hour without experiencing or 

developing irreversible or other serious 

health effects or symptoms which could 

impair an individual’s ability to take 

protective action. 

An acute REL for 1-hour exposure 

durations is typically lower than its 

corresponding AEGL–1 and ERPG–1. 

Even though their definitions are 

slightly different, AEGL–1s are often the 

same as the corresponding ERPG–1s, 

and AEGL–2s are often equal to ERPG– 

2s. The maximum HQs from our acute 

inhalation screening risk assessment 

typically result when we use the acute 

REL for a HAP. In cases where the 

maximum acute HQ exceeds 1, we also 

report the HQ based on the next highest 

acute dose-response value (usually the 

AEGL–1 and/or the ERPG–1). 

For the PEPO Production source 

category, we did not use a default acute 

emissions multiplier of 10, but rather 

we used process level-specific acute 

emissions multipliers, generally ranging 

from a factor of 2 to 10 as was done in 

past chemical and petrochemical 

residual risk reviews such as for the 

2015 Petroleum Refinery Sector rule, 

2024 HON rulemaking, 2020 MON RTR, 

and 2020 EMACT standards RTR, where 

similar emission sources and standards 

exist. These refinements are discussed 

more fully in appendix 1 of the 

document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

In our acute inhalation screening risk 

assessment, acute impacts are deemed 

negligible for HAP for which acute HQs 

are less than or equal to 1, and no 

further analysis is performed for these 

HAP. In cases where an acute HQ from 

the screening step is greater than 1, we 

assess the site-specific data to ensure 


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18Burger, J. 2002. Daily consumption of wild fish 

and game: Exposures of high end recreationists. 

International Journal of Environmental Health 

Research, 12:343–354. 

19U.S. EPA. Exposure Factors Handbook 2011 

Edition (Final). U.S. Environmental Protection 

Agency, Washington, DC, EPA/600/R–09/052F, 

2011. 

20 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 

Continued 

that the acute HQ is at an off-site 

location. For the PEPO Production 

source category, the data refinements 

employed consisted of reviewing 

satellite imagery of the locations of the 

maximum acute HQ values to determine 

if the maximum was off facility 

property. For any maximum value that 

was determined to be on facility 

property, the next highest value that 

was off facility property was used. 

These refinements are discussed more 

fully in the document titled Residual 

Risk Assessment for the Polyether 

Polyols (PEPO) Production Source 

Category in Support of the 2024 Risk 

and Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

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 (e.g., ingestion). We first 

determine whether any sources in the 

source category emit any HAP known to 

be persistent and bioaccumulative in the 

environment, as identified in the EPA’s 

Air Toxics Risk Assessment Library (see 

Volume 1, appendix D, at https:// 

www.epa.gov/fera/risk-assessment-andmodeling-air-toxics-risk-assessmentreference-library). 

For the PEPO Production source 

category, we identified PB–HAP 

emissions of arsenic compounds, 

cadmium compounds, polycyclic 

organic matter (POM), and mercury, 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 POM. Based 

on the EPA estimates of toxicity and 

bioaccumulation potential, these 

pollutants represent a health protective 

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 upperbound ingestion rates. 

In the Tier 2 screening assessment, 

the location of each facility that exceeds 

a Tier 1 screening threshold emission 

rate is used to refine the assumptions 

associated with the Tier 1 fisher and 

farmer exposure scenarios at that 

facility. A key assumption in the Tier 1 

screening assessment is that a lake and/ 

or farm is located near the facility. As 

part of the Tier 2 screening assessment, 

we use a U.S. Geological Survey (USGS) 

database to identify actual waterbodies 

within 50 km of each facility and 

assume the fisher only consumes fish 

from lakes within that 50-km zone. We 

also examine the differences between 

local meteorology near the facility and 

the meteorology used in the Tier 1 

screening assessment. We then adjust 

the previously-developed Tier 1 

screening threshold emission rates for 

each PB–HAP for each facility based on 

an understanding of how exposure 

concentrations estimated for the 

screening scenario change with the use 

of local meteorology and the USGS lakes 

database. 

In the Tier 2 farmer scenario, we 

maintain an assumption that the farm is 

located within 0.5 km of the facility and 

that the farmer consumes meat, eggs, 

dairy, vegetables, and fruit produced 

near the facility. We may further refine 

the Tier 2 screening analysis by 

assessing a gardener scenario to 

characterize a range of exposures, with 

the gardener scenario being more 

plausible in RTR evaluations. Under the 

gardener scenario, we assume the 

gardener consumes home-produced 

eggs, vegetables, and fruit products at 

the same ingestion rate as the farmer. 

The Tier 2 screen continues to rely on 

the high-end food intake assumptions 

that were applied in Tier 1 for local fish 

(adult female angler at 99th percentile 

fish consumption 18) and locally grown 

or raised foods (90th percentile 

consumption of locally grown or raised 

foods for the farmer and gardener 

scenarios 19). 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. 

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 sitespecific 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.20 Values below the level of the 


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(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 1989 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. 

21We note that in many instances, we did not 

have sufficient information to parse out emissions 

from PEPO processes from facility-wide emissions 

inventories; thus, to avoid underestimating 

emissions from PEPO sources, we modeled most or 

all of certain facilities’ emissions records as if they 

all are from the PEPO Production source category. 

primary (health-based) lead NAAQS are 

considered to have a low potential for 

multipathway risk. 

For further information on the 

multipathway assessment approach, see 

the document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

5. How do we assess risks considering 

emissions control options? 

In addition to assessing baseline 

inhalation risks and screening for 

potential multipathway risks, we also 

estimate risks considering the potential 

emission reductions that would be 

achieved by the control options under 

consideration. In these cases, the 

expected emission reductions are 

applied to the specific HAP and 

emission points in the RTR emissions 

dataset to develop corresponding 

estimates of risk and incremental risk 

reductions. 

6. How do we conduct the 

environmental risk screening 

assessment? 

a. Adverse Environmental Effect, 

Environmental HAP, and Ecological 

Benchmarks 

The EPA conducts a screening 

assessment to examine the potential for 

an adverse environmental effect as 

required under section 112(f)(2)(A) of 

the CAA. Section 112(a)(7) of the CAA 

defines ‘‘adverse environmental effect’’ 

as ‘‘any significant and widespread 

adverse effect, which may reasonably be 

anticipated, to wildlife, aquatic life, or 

other natural resources, including 

adverse impacts on populations of 

endangered or threatened species or 

significant degradation of 

environmental quality over broad 

areas.’’ 

The EPA focuses on eight HAP, which 

are referred to as ‘‘environmental HAP,’’ 

in its screening assessment: six PB–HAP 

and two acid gases. The PB–HAP 

included in the screening assessment 

are arsenic compounds, cadmium 

compounds, dioxins/furans, POM, 

mercury (both inorganic mercury and 

methyl mercury), and lead compounds. 

The acid gases included in the screening 

assessment are hydrochloric acid (HCl) 

and hydrofluoric acid (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 watercolumn 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-adverseeffect level, and no-observed-adverseeffect 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 

document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

b. Environmental Risk Screening 

Methodology 

For the environmental risk screening 

assessment, the EPA first determined 

whether any facilities in the PEPO 

Production source category emitted any 

of the environmental HAP. For the 

PEPO Production source category, we 

identified emissions of arsenic 

compounds, cadmium compounds, 

POM, and mercury.21 Because one or 

more of the environmental HAP 

evaluated are emitted by at least one 

facility in the PEPO Production source 

category, we proceeded to the second 

step of the evaluation. 

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 backcalculate 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. If 

emissions from a facility do not exceed 

the Tier 2 screening threshold emission 

rate, the facility ‘‘passes’’ the screening 


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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–4) of lead 

around each facility in the source 

category to the level of the secondary 

NAAQS for lead. The secondary lead 

NAAQS is a reasonable means of 

evaluating environmental risk because it 

is set to provide substantial protection 

against adverse welfare effects which 

can include ‘‘effects on soils, water, 

crops, vegetation, man-made materials, 

animals, wildlife, weather, visibility and 

climate, damage to and deterioration of 

property, and hazards to transportation, 

as well as effects on economic values 

and on personal comfort and wellbeing.’’ 

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 singletier 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 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 document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

7. 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 

the PEPO Production source category, 

we conducted the facility-wide 

assessment using a dataset compiled 

from the 2017 NEI and other emissions 

information discussed in section II.C of 

this preamble. Once a quality assured 

source category dataset was available, it 

was placed back with the remaining 

records from the NEI for that facility 

(which in most instances was 2017 NEI 

data). 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 document titled 

Residual Risk Assessment for the 

Polyether Polyols (PEPO) Production 

Source Category in Support of the 2024 

Risk and Technology Review Proposed 

Rule, available through the docket for 

this rulemaking, provides the 

methodology and results of the facilitywide analyses, including all facilitywide risks and the percentage of source 

category contribution to facility-wide 

risks. 

8. How do we conduct communitybased risk assessments? 

In addition to the source category and 

facility-wide risk assessments, we also 

assessed the combined inhalation 

cancer risk from all local stationary 

sources of HAP for which we have 

emissions data. Specifically, we 

combined the modeled impacts from the 

facility-wide assessment (which 

includes category and non-category 

sources) with other nearby stationary 

point source model results. Section II.C 

of this preamble discusses the facilitywide emissions used in this assessment. 

For the other nearby point sources, we 

used AERMOD model results with 

emissions based primarily on the 2020 

NEI. After combining these model 

results, we assessed cancer risks due to 

the inhalation of all HAP emitted by 

point sources for the populations 

residing within 10 km (∼6.2 miles) of 

PEPO facilities. In the community-based 

risk assessment, we compared the 

modeled source category and facilitywide cancer risks to the cancer risks 

from other nearby point sources to 

determine the portion of the risks that 

could be attributed to the source 

category addressed in this proposal. The 

document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking, provides the methodology 

and results of the community-based 

risks analyses. 

9. 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 health protective tools and 

assumptions, ensures that our decisions 

are health and environmentally 

protective. A brief discussion of the 

uncertainties in the RTR emissions 

dataset, dispersion modeling, inhalation 

exposure estimates, and dose-response 

relationships follows below. Also 

included are those uncertainties specific 

to our acute screening assessments, 

multipathway screening assessments, 

and our environmental risk screening 

assessments. A more thorough 

discussion of these uncertainties is 

included in the document titled 

Residual Risk Assessment for the 

Polyether Polyols (PEPO) Production 


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22 IRIS glossary (https://ofmpub.epa.gov/ 

sor_internet/registry/termreg/searchandretrieve/ 

glossariesandkeywordlists/search.do?details=&

glossaryName=IRIS%20Glossary). 

23An 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. 

24See 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. 

Source Category in Support of the 2024 

Risk and Technology Review Proposed 

Rule, which is available in the docket 

for this rulemaking. If a multipathway 

site-specific assessment was performed 

for this source category, a full 

discussion of the uncertainties 

associated with that assessment can be 

found in appendix 11 of that document, 

Site-Specific Human Health 

Multipathway Residual Risk Assessment 

Report. 

a. Uncertainties in the RTR Emissions 

Dataset 

Although the development of the RTR 

emissions dataset involved quality 

assurance/quality control processes, the 

accuracy of emissions values will vary 

depending on the source of the data, the 

degree to which data are incomplete or 

missing, the degree to which 

assumptions made to complete the 

datasets are accurate, errors in emission 

estimates, and other factors. The 

emission estimates considered in this 

analysis generally are annual totals for 

certain years, and they do not reflect 

short-term fluctuations during the 

course of a year or variations from year 

to year. The estimates of peak hourly 

emission rates for the acute effects 

screening assessment were based on an 

emission adjustment factor applied to 

the average annual hourly emission 

rates, which are intended to account for 

emission fluctuations due to normal 

facility operations. 

b. Uncertainties in Dispersion Modeling 

We recognize there is uncertainty in 

ambient concentration estimates 

associated with any model, including 

the EPA’s recommended regulatory 

dispersion model, AERMOD. In using a 

model to estimate ambient pollutant 

concentrations, the user chooses certain 

options to apply. For RTR assessments, 

we select some model options that have 

the potential to overestimate ambient air 

concentrations (e.g., not including 

plume depletion or pollutant 

transformation). We select other model 

options that have the potential to 

underestimate ambient impacts (e.g., not 

including building downwash). Other 

options that we select have the potential 

to either under- or overestimate ambient 

levels (e.g., meteorology and receptor 

locations). On balance, considering the 

directional nature of the uncertainties 

commonly present in ambient 

concentrations estimated by dispersion 

models, the approach we apply in the 

RTR assessments should yield unbiased 

estimates of ambient HAP 

concentrations. We also note that the 

selection of meteorology dataset 

location could have an impact on the 

risk estimates. As we continue to update 

and expand our library of 

meteorological station data used in our 

risk assessments, we expect to reduce 

this variability. 

c. Uncertainties in Inhalation Exposure 

Assessment 

Although every effort is made to 

identify all of the relevant facilities and 

emission points, as well as to develop 

accurate estimates of the annual 

emission rates for all relevant HAP, the 

uncertainties in our emissions 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’’ 

(the EPA’s 2005 Guidelines for 

Carcinogen Risk Assessment, page 1–7). 

This is the approach followed here as 

summarized in the next paragraphs. 

Cancer UREs used in our risk 

assessments are those that have been 

developed to generally provide an upper 

bound estimate of risk.22 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.23 Chronic noncancer RfC and 

reference dose values represent chronic 

exposure levels that are intended to be 

health-protective levels. To derive doseresponse values that are intended to be 

‘‘without appreciable risk,’’ the 

methodology relies upon an uncertainty 

factor (UF) approach,24 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. 

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, 


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25 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. 

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 

source category are lacking doseresponse 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 a group of compounds that are 

unspeciated (e.g., groups of compounds 

that we do not know the exact 

composition of like 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) cooccur. We then include the additional 

assumption that a person is located at 

this point at the same time. Together, 

these assumptions represent a 

reasonable worst-case actual exposure 

scenario. In most cases, it is unlikely 

that a person would be located at the 

point of maximum exposure during the 

time when peak emissions and 

reasonable worst-case air dispersion 

conditions occur simultaneously. 

f. Uncertainties in the Multipathway 

and Environmental Risk Screening 

Assessments 

For each source category, we 

generally rely on site-specific levels of 

PB–HAP or environmental HAP 

emissions to determine whether a 

refined assessment of the impacts from 

multipathway exposures is necessary or 

whether it is necessary to perform an 

environmental screening assessment. 

This determination is based on the 

results of a three-tiered screening 

assessment that relies on the outputs 

from models—TRIM.FaTE and 

AERMOD—that estimate environmental 

pollutant concentrations and human 

exposures for five PB–HAP (dioxins, 

POM, mercury, cadmium, and arsenic) 

and two acid gases (HF and HCl). For 

lead, we use AERMOD to determine 

ambient air concentrations, which are 

then compared to the secondary 

NAAQS standard for lead. Two 

important types of uncertainty 

associated with the use of these models 

in RTR risk assessments and inherent to 

any assessment that relies on 

environmental modeling are model 

uncertainty and input uncertainty.25

Model uncertainty concerns whether 

the model adequately represents the 

actual processes (e.g., movement and 

accumulation) that might occur in the 

environment. For example, does the 

model adequately describe the 

movement of a pollutant through the 

soil? This type of uncertainty is difficult 

to quantify. However, based on feedback 

received from previous EPA SAB 

reviews and other reviews, we are 

confident that the models used in the 

screening assessments are appropriate 

and state-of-the-art for the multipathway 

and environmental screening risk 

assessments conducted in support of 

RTRs. 

Input uncertainty is concerned with 

how accurately the models have been 

configured and parameterized for the 

assessment at hand. For Tier 1 of the 

multipathway and environmental 

screening assessments, we configured 

the models to avoid underestimating 

exposure and risk. This was 

accomplished by selecting upper-end 

values from nationally representative 

datasets for the more influential 

parameters in the environmental model, 

including selection and spatial 

configuration of the area of interest, lake 

location and size, meteorology, surface 

water, soil characteristics, and structure 

of the aquatic food web. We also assume 

an ingestion exposure scenario and 

values for human exposure factors that 

represent reasonable maximum 

exposures. 

In Tier 2 of the multipathway and 

environmental screening assessments, 

we refine the model inputs to account 

for meteorological patterns in the 

vicinity of the facility versus using 

upper-end national values, and we 

identify the actual location of lakes near 

the facility rather than the default lake 

location that we apply in Tier 1. By 

refining the screening approach in Tier 

2 to account for local geographical and 

meteorological data, we decrease the 

likelihood that concentrations in 

environmental media are overestimated, 

thereby increasing the usefulness of the 

screening assessment. In Tier 3 of the 

screening assessments, we refine the 

model inputs again to account for hourby-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 


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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. 

C. How do we perform the technology 

review? 

Our technology review primarily 

focuses on the identification and 

evaluation of developments in practices, 

processes, and control technologies that 

have occurred since the previous PEPO 

NESHAP technology review was 

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 CAA section 112 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 (or last updated) 

the PEPO NESHAP, we review a variety 

of data sources in our investigation of 

potential practices, processes, or 

controls to consider. We also review the 

NESHAP and the available data to 

determine if there are any unregulated 

emissions of HAP within the source 

category, and evaluate these data for use 

in developing new emission standards. 

See sections II.C and II.D of this 

preamble for information on the specific 

data sources that were reviewed as part 

of the technology review. 

D. How do we determine a MACT floor 

and consider beyond-the-floor? 

MACT standards must reflect the 

maximum degree of emissions reduction 

achievable through the application of 

measures, processes, methods, systems 

or techniques, including, but not limited 

to, measures that (1) reduce the volume 

of or eliminate pollutants through 

process changes, substitution of 

materials or other modifications; (2) 

enclose systems or processes to 

eliminate emissions; (3) capture or treat 

pollutants when released from a 

process, stack, storage or fugitive 

emissions point; (4) are design, 

equipment, work practice or operational 

standards (including requirements for 

operator training or certification); or (5) 

are a combination of the above. CAA 

section 112(d)(2)(A)–(E). The MACT 

standards may take the form of design, 

equipment, work practice or operational 

standards where the EPA first 

determines either that (1) a pollutant 

cannot be emitted through a conveyance 

designed and constructed to emit or 

capture the pollutant, or that any 

requirement for, or use of, such a 

conveyance would be inconsistent with 

law; or (2) the application of 

measurement methodology to a 

particular class of sources is not 

practicable due to technological and 

economic limitations. CAA section 

112(h)(1)–(2). 

The MACT ‘‘floor’’ is the minimum 

control level allowed for MACT 

standards promulgated under CAA 

section 112(d)(3) and may not be based 

on cost considerations. For new sources 

located at facilities that are major 

sources of HAP, section 112 of the CAA 

requires the EPA to establish standards 

that are no less stringent than the 

emissions control that is achieved in 

practice by the best controlled similar 

source. The statute does not define 

‘‘achieved in practice’’ nor does it 

dictate the manner in which the agency 

determines which source is the best 

controlled similar source, instead 

leaving it to the agency’s discretion to 

make those determinations. For existing 

sources located at facilities that are 

major sources of HAP, standards must 

be no less stringent than the average 

emissions limitation achieved by the 

best performing sources for which the 

EPA has emissions information. Again, 

the CAA leaves to the EPA’s discretion 

the manner in which to calculate ‘‘the 

average emission limitation achieved’’ 

by the best performing sources. Under 

section 112, the CAA recognizes that 

source categories and subcategories 

have differing numbers of sources and 

provides category size-specific 

instructions on determining standard 

stringency for existing sources. 

Specifically, standards for categories or 

subcategories with fewer than 30 

sources must be based on the average 

emission limitation achieved by the best 

performing 5 sources, and standards for 

categories or subcategories with 30 or 

more sources must be based on the 

average emission limitation achieved by 

the best performing 12 percent of 

sources for which the EPA has 

emissions information. In developing 

MACT standards, the EPA must also 


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26U.S. EPA. Evaluation of the Inhalation 

Carcinogenicity of Ethylene Oxide (CASRN 75–21– 

8) In Support of Summary Information on the 

Integrated Risk Information System (IRIS). 

December 2016. EPA/635/R–16/350Fa. Available at: 

https://cfpub.epa.gov/ncea/iris/iris_documents/ 

documents/toxreviews/1025tr.pdf. 

27When considering all emissions reported by the 

facility for which we could not identify PEPO 

emissions records, we estimated a facility-wide 

maximum cancer risk of 70-in-1 million, so 

including this facility in the PEPO source category 

risk assessment would not have changed our 

decisions on standards to address unacceptable 

risk. 

consider control options that are more 

stringent than the floor (i.e., ‘‘beyondthe-floor’’ options) under CAA section 

112(d)(2). We may establish beyond-thefloor standards more stringent than the 

floor based on considerations of the cost 

of achieving the emission reductions, 

any non-air quality health and 

environmental impacts, and energy 

requirements. 

IV. Analytical Results and Proposed 

Decisions 

A. What are the results of the risk 

assessment and analyses? 

As previously discussed, we 

conducted a risk assessment for the 

PEPO Production source category. We 

previously identified EtO as a cancer 

risk driver from facilities with PEPO 

NESHAP-subject processes in the first 

risk assessment we conducted in 2014. 

However, the EPA’s IRIS inhalation URE 

for EtO was revised in 2016,26 based on 

new data, showing EtO to be more 

carcinogenic than previously 

understood (i.e., resulting in a URE 60 

times greater than the previous URE 

over a 70-year lifetime). We briefly 

present the results of the risk 

assessment below and in more detail in 

the document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

1. Chronic Inhalation Risk Assessment 

Results 

Out of the 25 facilities identified as 

subject to the PEPO NESHAP, two 

facilities do not have source category 

emissions included in our risk 

assessment. One facility has a PEPO 

source under construction while the 

other facility did not report records in 

its emissions inventory with names that 

that could be linked to its PEPO process 

and thus we did not have sufficient 

information to parse out the source 

category records.27 The results of the 

chronic baseline inhalation cancer risk 

assessment, which are estimated using 

modeling and is the case for all risk 

results presented here and in 

subsequent sections, indicate that, based 

on estimates of current actual emissions, 

the MIR posed by the source category is 

1,000-in-1 million, driven by EtO 

emissions from wastewater (77 percent) 

and equipment leaks (21 percent). The 

total estimated cancer incidence based 

on actual emission levels is 0.3 excess 

cancer cases per year (or 1 cancer case 

every 3.3 years). EtO emissions 

contribute 99.6 percent of the total 

cancer incidence. Within 50 km of 

PEPO NESHAP-subject facilities, the 

population exposed to cancer risk 

greater than 100-in-1 million for PEPO 

NESHAP actual emissions is 

approximately 3,300 people, and the 

population exposed to cancer risk 

greater than or equal to 1-in-1 million is 

approximately 3.8 million people. Of 

the 23 facilities that the EPA assessed 

for source category risk, 6 facilities have 

an estimated maximum cancer risk 

greater than 100-in-1 million. In 

addition, the maximum modeled 

chronic noncancer TOSHI for the source 

category based on actual emissions is 

estimated to be 0.1 (for respiratory 

effects). No populations are estimated to 

be exposed to a TOSHI greater than 1. 

Of the 23 facilities that the EPA 

assessed for the source category risk, 5 

facilities have allowable emissions that 

differ from the actual emissions (see 

section III.B.2 of this preamble). For the 

other 18 facilities, actual emissions 

equal allowable emissions, and 

therefore, actual risks equal allowable 

risks for these 18 facilities. Our risk 

assessment based on allowable 

emissions includes all 23 facilities. This 

assessment estimates the MIR posed by 

the source category is unchanged at 

1,000-in-1 million, driven by EtO 

emissions from wastewater (77 percent) 

and equipment leaks (21 percent). The 

total estimated cancer incidence is 0.4 

excess cancer cases per year (or 1 cancer 

case every 2.5 years). EtO emissions 

contribute 99.6 percent of the total 

cancer incidence. Within 50 km of 

PEPO NESHAP-subject facilities, the 

population exposed to cancer risk 

greater than 100-in-1 million for PEPO 

NESHAP allowable emissions is 

approximately 6,700 people, and the 

population exposed to cancer risk 

greater than or equal to 1-in-1 million is 

approximately 4.7 million people. Of 

the 23 facilities that the EPA assessed 

for source category risk, 8 facilities have 

an estimated maximum cancer risk 

greater than 100-in-1 million. In 

addition, the EPA estimated the 

maximum modeled chronic noncancer 

TOSHI for the source category based on 

allowable emissions to be less than 1. 

See table 1 of this preamble for a 

summary of the PEPO NESHAP 

inhalation risk assessment results. 

TABLE 1—PEPO PRODUCTION SOURCE CATEGORY INHALATION RISK ASSESSMENT RESULTS BASED ON ACTUAL AND

ALLOWABLE EMISSIONS 1

Risk assessment Number of 

facilities 2

Maximum 

individual 

cancer risk 

(-in-1 

million) 3

Estimated population at 

increased risk of cancer 

Estimated 

annual 

cancer 

incidence 

(cases per 

year) 

Maximum chronic noncancer TOSHI 

Refined 

maximum 

screening 

acute noncancer HQ 

≥1-in-1 

million 

>100-in-1 

million 

Baseline (Pre-control) Actual Emissions 

Source Category ................................ 23 1,000 3.8 3,300 0.3 0.1 (respiratory) ................................. 1 

Facility-wide 4 ..................................... 25 2,000 7.3 4,000 0.6 3 (respiratory).

Baseline (Pre-control) Allowable Emissions 

Source Category 1 ............................. 23 1,000 4.7 6,700 0.4 0.1 (respiratory).

1There are allowable emissions for 5 facilities. For the other 18 facilities, actual emissions equal allowable emissions. 

2There are 25 PEPO production facilities; however, only 23 of these facilities are included in the source category risk assessment based on available data. 3 Maximum individual excess lifetime cancer risk due to HAP emissions. 

4See ‘‘Facility-Wide Risk Results’’ in section IV.A.5 of this preamble for more details on this risk assessment. 


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28Note that while the multipathway risk 

screening results includes metals (e.g., arsenic, 

cadmium, mercury) and POM, the EPA used a 

health-protective approach and included emissions 

inventory records that were not clearly labeled (not 

easily categorized) in modeling of emissions from 

the PEPO Production source category. This means 

that emissions from other source categories were 

likely included for this analysis in certain 

instances. We have no information suggesting that 

metals or POM are emitted from PEPO processes. 

See appendix 1 of the document titled Residual 

Risk Assessment for the Polyether Polyols (PEPO) 

Production Source Category in Support of the 2024 

Risk and Technology Review Proposed Rule, which 

is available in the docket for this rulemaking, for 

more details about development of the risk 

modeling file. 

29Note that while the environmental risk 

screening results includes metals (e.g., arsenic, 

cadmium, lead, mercury), POM, and acid gases 

(e.g., HCl), the EPA used a health-protective 

approach and included emissions inventory records 

that were not clearly labeled (not easily categorized) 

in modeling of emissions from the PEPO Production 

source category to avoid underestimating emissions 

from PEPO sources. This means that emissions from 

other source categories were likely included for this 

analysis in certain instances. We have no 

information suggesting that metals, POM, or HCl are 

emitted from PEPO processes. See appendix 1 of the 

document titled Residual Risk Assessment for the 

Polyether Polyols (PEPO) Production Source 

Category in Support of the 2024 Risk and 

Technology Review Proposed Rule, which is 

available in the docket for this rulemaking, for more 

details about development of the risk modeling file. 

2. Screening Level Acute Risk 

Assessment Results 

As presented in table 1 of this 

preamble, the estimated worst-case offsite acute inhalation exposures to 

emissions from the PEPO Production 

source category result in a maximum 

modeled acute noncancer HQ equal to 1 

based on the REL for methoxytriglycol 

(a glycol ether). 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. The main body and 

appendix 10 of the document titled 

Residual Risk Assessment for the 

Polyether Polyols (PEPO) Production 

Source Category in Support of the 2024 

Risk and Technology Review Proposed 

Rule, which is available in the docket 

for this rulemaking, provides detailed 

information about the assessment, 

including evaluation of the screeninglevel acute risk assessment results. 

3. Multipathway Risk Screening Results 

For the PEPO Production source 

category, three facilities emitted at least 

1 PB–HAP, including arsenic, cadmium, 

mercury, and POM.28 Emissions of these 

PB–HAP from each facility were 

compared to the respective pollutantspecific Tier 1 screening emission 

thresholds. The Tier 1 screening 

analysis for PB–HAP (other than lead, 

which was evaluated differently), 

indicated no facilities exceeded the Tier 

1 emission threshold for arsenic, 

cadmium, mercury, or POM. 

In evaluating the potential for 

multipathway risk from emissions of 

lead, the modeled maximum annual 

ambient lead concentration (0.000002 

mg/m3) was compared to the NAAQS for 

lead (0.15 mg/m3, 3-month rolling 

average). We did not estimate any 

exceedance of the NAAQS for lead. The 

modeled maximum annual lead 

concentration is well below the NAAQS 

for lead, indicating low potential for 

multipathway risk of concern due to 

lead emissions. 

Detailed information about the 

assessment is provided in the document 

titled Residual Risk Assessment for the 

Polyether Polyols (PEPO) Production 

Source Category in Support of the 2024 

Risk and Technology Review Proposed 

Rule, which is available in the docket 

for this rulemaking. 

4. Environmental Risk Screening Results 

As described in section IV.A of this 

preamble, we conducted a screening 

assessment for adverse environmental 

effects for the PEPO Production source 

category. The environmental screening 

assessment included the following HAP: 

arsenic, cadmium, methyl mercury, 

divalent mercury, and POM.29

In the Tier 1 screening analysis for 

PB–HAP (other than lead, which was 

evaluated differently), none of the PB– 

HAP had exceedances for any ecological 

benchmark. 

In evaluating the potential adverse 

environmental risks associated with 

emissions of lead, the modeled 

maximum annual ambient lead 

concentration (0.000002 mg/m3) was 

compared to the NAAQS for lead (0.15 

mg/m3, 3-month rolling average). We did 

not estimate any exceedance of the 

NAAQS for lead. The modeled 

maximum annual lead concentration is 

well below the NAAQS for lead, 

indicating low potential for 

environmental risk of concern due to 

lead emissions. 

We also conducted an environmental 

risk screening assessment specifically 

for acid gases (i.e., HCl and HF) for the 

PEPO Production source category. There 

are no facilities with HF emissions. 

There are three facilities with HCl 

emissions. 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. 

Detailed information about the 

assessments is provided in the 

document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 

Technology Review Proposed Rule, 

which is available in the docket for this 

rulemaking. 

5. Facility-Wide Risk Results 

We assessed facility-wide risk, as 

described in section III.B.7 of this 

preamble, to characterize the source 

category risk in the context of ‘‘whole 

facility’’ risk using the NEI-based data 

described in section II.C of this 

preamble. Facility-wide risk was 

modeled using post-control emissions 

from the processes subject to the HON 

to reflect the emissions reductions 

expected from the HON rulemaking that 

was signed in early 2024 (89 FR 42932). 

The maximum lifetime individual 

cancer risk posed by the 25 modeled 

facilities based on facility-wide 

emissions is 2,000-in-1 million with EtO 

emissions from wastewater (72 percent) 

and equipment leaks (20 percent) from 

PEPO production source category 

emissions driving the risk. The total 

estimated cancer incidence based on 

facility-wide emission levels is 0.6 

excess cancer cases per year. EtO 

emissions contribute 94 percent of the 

total cancer incidence. Within 50 km of 

PEPO NESHAP-subject facilities, the 

population exposed to cancer risk 

greater than 100-in-1 million for PEPO 

facility-wide emissions is approximately 

4,000 people, and the population 

exposed to cancer risk greater than or 

equal to 1-in-1 million is approximately 

7.3 million people. The maximum 

chronic noncancer TOSHI due to 

facility-wide emissions is estimated to 

be 3 (for respiratory effects) due to 

emissions of chlorine from 1 facility. A 

different facility has a chronic 

noncancer TOSHI of 2 (for respiratory 

effects) due to facility-wide emissions of 

maleic anhydride. Approximately 60 

people are estimated to be exposed to a 

TOSHI greater than 1 due to facilitywide emissions. Of the approximately 

60 people, 44 people are exposed to a 

TOSHI of 3 due to emissions of chlorine 

and 16 people are exposed to a TOSHI 

of 2 due to emissions of maleic 

anhydride. 

After the controls proposed in this 

action are implemented for the PEPO 

Production source category (see section 

IV.B.2 of this preamble), the postVerDate Sep<11>2014 08:52 Dec 27, 2024 Jkt 265001 PO 00000 Frm 00020 Fmt 4701 Sfmt 4702 E:\FR\FM\27DEP2.SGM 27DEP2

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control facility-wide cancer risk remains 

greater than 100-in-1 million at two 

facilities. 

6. Community-Based Risk Assessment 

We also conducted a communitybased risk assessment for PEPO 

NESHAP-subject facilities. The goal of 

this assessment was to estimate cancer 

risk from HAP emitted from all local 

stationary point sources for which we 

have emissions data. We estimated the 

overall inhalation cancer risk due to 

emissions from all stationary point 

sources impacting census blocks within 

10 km of the 25 PEPO production 

facilities. Specifically, we combined the 

modeled impacts from category and 

non-category HAP sources at PEPO 

production facilities, as well as other 

stationary point source HAP emissions. 

Within 10 km of PEPO NESHAP-subject 

facilities, we identified 823 non-source 

category facilities that could potentially 

also contribute to HAP inhalation 

exposures. Similar to the facility-wide 

risk assessment, the community-based 

risk assessment uses post-control 

emissions from the processes subject to 

the HON to reflect the emissions 

reductions expected from the HON 

rulemaking that was signed in early 

2024 (89 FR 42932). 

We first looked at what the maximum 

cancer risk is for communities around 

PEPO production facilities. The results 

indicate that the community-level 

maximum individual cancer risk is the 

same as both the source category MIR 

and the maximum individual cancer 

risk for the facility-wide assessment, 

2,000-in-1 million. The communitybased risk assessment estimated that 

greater than 99 percent of the 

community-level maximum individual 

cancer risk is attributable to emissions 

from PEPO production facilities 

(including both source category and 

non-category emissions). We then 

looked at the risks to the communities 

from all emissions sources for which we 

had data. Within 10 km, the population 

exposed to cancer risks greater than 100- 

in-1 million from all nearby emissions 

is approximately 5,300. For comparison, 

approximately 3,300 people have cancer 

risks greater than 100-in-1 million due 

to PEPO production emissions and 

approximately 4,000 people have cancer 

risks greater than 100-in-1 million due 

to PEPO facility-wide emissions (see 

table 2 of this preamble). The overall 

cancer incidence for this exposed 

population (i.e., populations with risks 

greater than 100-in-1 million living 

within 10 km of PEPO production 

facilities) is 0.02, with 84 percent of the 

cancer incidence from PEPO production 

processes, 9 percent from non-PEPO 

processes at PEPO production facilities 

(a total of 93 percent from PEPO 

production facilities), and 7 percent 

from other nearby stationary point 

sources that are not PEPO production 

facilities. 

The population exposed to cancer 

risks greater than or equal to 1-in-1 

million in the community-based 

assessment is approximately 1.2 million 

people. For comparison, approximately 

830,000 people have cancer risks greater 

than or equal to 1-in-1 million due to 

PEPO production process emissions and 

approximately 1.1 million people have 

cancer risks greater than 1-in-1 million 

due to PEPO facility-wide emissions 

(see table 2 of this preamble). The 

overall cancer incidence for this 

exposed population (i.e., people with 

risks greater than or equal to 1-in-1 

million and living within 10 km of 

PEPO production facilities) is 0.4, with 

34 percent of the incidence due to 

emissions from PEPO production 

processes, 30 percent from emissions of 

non-PEPO processes at PEPO 

production facilities (that is, a total of 

64 percent from emissions from PEPO 

production facilities) and 36 percent 

from emissions from other nearby 

stationary sources that are not PEPO 

production facilities. 

After the controls proposed in this 

action are implemented for the PEPO 

Production source category (see section 

IV.B.2 of this preamble), the 

community-level maximum individual 

cancer risk will be reduced to the same 

as the facility-wide assessment, 300-in1 million. The assessment estimated 

that 51 percent of the MIR is attributable 

to emissions from non-PEPO processes 

at a PEPO production facility, 43 

percent from PEPO processes and 6 

percent from other nearby stationary 

point sources that are not PEPO 

production facilities. The population 

(within 10 km of PEPO facilities) 

exposed to cancer risks greater than 100- 

in-1 million from all nearby emissions 

will be significantly reduced from 5,300 

people to 500 people; a 91 percent 

reduction from the baseline. The 

populations exposed to cancer risks 

greater than 100-in-1 million from the 

PEPO Production source category and 

facility-wide emissions are similarly 

reduced, from 3,300 people to 0 for 

source category emissions and from 

4,000 to 200 for facility-wide emissions 

(see table 2 of this preamble). 

Furthermore, the overall cancer 

incidence for this exposed population is 

expected to be reduced from 0.02 to 

0.001. The percentage of cancer 

incidence due to emissions from PEPO 

processes is reduced from 84 percent to 

28 percent. The percentage of the cancer 

incidence due to emissions from nonPEPO processes at PEPO production 

facilities and emissions from other 

nearby stationary sources 

proportionately shifts to 46 percent and 

26 percent respectively. EtO emissions 

across these sources remain the largest 

source of incidence, accounting for 93 

percent of the overall cancer incidence 

for this exposed population. 

The post-control population exposed 

to cancer risks greater than or equal to 

1-in-1 million will be reduced from 1.2 

million to 1.1 million. In comparison, 

after the controls proposed in this 

action, the number of people with risks 

greater than or equal to 1-in-1 million 

due to source category emissions would 

reduce from 830,000 to 560,000 and due 

to facility-wide emissions from 1.1 

million to 1 million (see table 2 of this 

preamble). The overall cancer incidence 

for this exposed population is expected 

to be reduced from 0.4 to 0.3. The 

percentage of cancer incidence from 

PEPO processes is expected to decrease 

from 34 to 11 percent. The cancer 

incidence from non-PEPO processes at 

PEPO production facilities and from 

other nearby stationary sources are 

expected to proportionately shift to 40 

percent and 49 percent, respectively. 

More results from the communitybased assessment are provided in the 

document titled Analysis of 

Demographic Factors For Populations 

Living Near Polyether Polyols (PEPO) 

Production Facilities—CommunityBased Assessment, which is available in 

the docket for this rulemaking. 


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TABLE 2—INHALATION CANCER RISK ASSESSMENT RESULTS FOR COMMUNITIES LIVING WITHIN 10 km OF PEPO 

PRODUCTION FACILITIES

Risk assessment 

Maximum 

individual 

cancer risk 

(-in-1 million) 

Estimated population at 

increased risk of cancer 

>100-in-1 

million ≥1-in-1 million 

Baseline (Pre-control) 

PEPO Production Source Category ............................................................................................ 1,000 3,300 830,000 

Facility-wide ................................................................................................................................. 2,000 4,000 1.1 million 

Community-based ........................................................................................................................ 2,000 5,300 1.2 million 

After Implementation of Proposed Controls (Post-control) 

PEPO Production Source Category ............................................................................................ 100 0 560,000 

Facility-wide ................................................................................................................................. 300 200 1 million 

Community-based ........................................................................................................................ 300 500 1.1 million 

7. What demographic groups might 

benefit from this regulation? 

To examine the potential for EJ 

concerns, the EPA conducted three 

different demographic analyses: a 

proximity analysis, baseline cancer riskbased analysis (i.e., before 

implementation of any controls required 

by this proposed action), and postcontrol cancer risk-based analysis (i.e., 

after implementation of the controls 

required by this proposed action). The 

proximity demographic analysis is an 

assessment of individual demographic 

groups in the total population living 

within 10 km (∼6.2 miles) and 50 km 

(∼31 miles) of the facilities. The baseline 

risk-based demographic analysis is an 

assessment of risks to individual 

demographic groups in the population 

living within 10 km and 50 km of the 

facilities prior to the implementation of 

any controls required by this proposed 

action (‘‘baseline’’). The post-control 

risk-based demographic analysis is an 

assessment of risks to individual 

demographic groups in the population 

living within 10 km and 50 km of the 

facilities after implementation of the 

controls required by this proposed 

action (‘‘post-control’’). Each of these 

demographic analyses were performed 

for the following three different HAP 

emissions scenarios: PEPO category 

HAP emissions (10 km and 50 km), 

whole-facility HAP emissions (10 km 

and 50 km), and community HAP 

emissions (10 km only). Demographic 

groups included in the analyses are: 

White, Black, American Indian and 

Alaskan Native, other races and 

multiracial, Hispanic or Latino, children 

17 years of age and under, adults 18 to 

64 years of age, adults 65 years of age 

and over, adults over 25 without a high 

school diploma, people living below the 

poverty level, people living below two 

times the poverty level, and 

linguistically isolated people. For a 

detailed discussion of the types of EJ 

analyses performed for this proposal 

and their results see section V.F of this 

preamble, ‘‘What analysis of 

environmental justice did we conduct?’’ 

B. What are our proposed decisions 

regarding risk acceptability, ample 

margin of safety, and adverse 

environmental effect? 

1. Risk Acceptability Under the Current 

MACT Standards 

As noted in section III.A of this 

preamble, we weigh a wide range of 

health risk measures and factors in our 

risk acceptability determination, 

including the cancer MIR, the number of 

persons in various cancer and 

noncancer risk ranges, cancer incidence, 

the maximum noncancer TOSHI, the 

maximum acute noncancer HQ, the 

extent of noncancer risks, the 

distribution of cancer and noncancer 

risks in the exposed population, and 

risk estimation uncertainties (54 FR 

38044, September 14, 1989). 

Under the current MACT standards 

for the PEPO Production source 

category, the risk results indicate that 

the MIR is 1,000-in-1 million, driven by 

emissions of EtO, and well above 100- 

in-1 million, which is the presumptive 

limit of acceptability. The estimated 

incidence of cancer due to inhalation 

exposures is 0.3 excess cancer case per 

year. The population estimated to be 

exposed to cancer risks greater than 100- 

in-1 million is approximately 3,300, and 

the population estimated to be exposed 

to cancer risks greater than or equal to 

1-in-1 million is approximately 3.8 

million. The estimated maximum 

chronic noncancer TOSHI from 

inhalation exposure for this source 

category is 0.1 (for respiratory effects). 

The acute risk screening assessment of 

reasonable worst-case inhalation 

impacts indicates a maximum acute 

noncancer HQ of 1. 

Considering all of the health risk 

information and factors discussed 

above, particularly the high MIR for the 

PEPO Production source category, the 

EPA proposes that the risks for the 

source category are unacceptable. As 

noted in section II.A of this preamble, 

when risks are unacceptable, under the 

1989 Benzene NESHAP approach and 

CAA section 112(f)(2)(A), the EPA must 

first determine the emissions standards 

necessary to reduce risk to an acceptable 

level, and then determine whether 

further HAP emissions reductions are 

necessary to provide an ample margin of 

safety to protect public health or to 

prevent, taking into consideration costs, 

energy, safety, and other relevant 

factors, an adverse environmental effect. 

Therefore, pursuant to CAA section 

112(f)(2), we are proposing certain 

standards for emission sources of EtO in 

the PEPO Production source category 

that are more protective than the current 

PEPO NESHAP MACT standards. 

2. Proposed Controls To Address 

Unacceptable Risks 

As previously discussed, we 

conducted a risk assessment of the 

PEPO Production source category 

because the 2016 revision to the EPA’s 

IRIS inhalation URE for EtO showed 

that EtO is more toxic than previously 

known. 

For the PEPO Production source 

category, we identified EtO as the 

cancer risk driver from PEPO sources. 

We are aware of 20 PEPO facilities 

reporting EtO emissions in their 

emissions inventories from PEPO 

production processes. From our residual 

risk assessment, six facilities with 

emissions of EtO from process vents, 

storage vessels, equipment leaks, and 

wastewater have estimated cancer risks 


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30The HON requirements that were added in 

2024 (89 FR 42932, May 16, 2024) apply to only the 

SOCMI source category; therefore, those 2024 HON 

amendments are currently not applicable to the 

PEPO Production source category. In other words, 

when we discuss the current PEPO NESHAP 

requirements that refer to HON, we mean pre-2024 

HON requirements. 

greater than 100-in-1 million in nearby 

communities. Additionally, an 

allowable leak of EtO from a heat 

exchange system contributes to cancer 

risks greater than 100-in-1 million. 

Thus, to reduce emissions of EtO from 

PEPO processes, the EPA is proposing 

more stringent control requirements for 

process vents, storage vessels, 

equipment leaks, heat exchange 

systems, and wastewater that emit or 

have the potential to emit EtO. As 

discussed later in this preamble, we are 

proposing that these requirements will 

reduce risk to an acceptable level and 

provide an ample margin of safety to 

protect public health, and no additional 

requirements are needed to prevent an 

adverse environmental effect. 

We discuss the control options we 

evaluated for reducing EtO emissions 

from PEPO processes in sections 

IV.B.2.a through IV.B.2.e of this 

preamble. 

a. Process Vents and Storage Vessels 

Process vents that emit EtO are 

primarily associated with reactors (from 

batch unit operations and continuous 

unit operations) that produce PEPO 

products using epoxides as a reactant. 

Other unit operations within the PMPU 

may also have process vents that emit 

EtO, such as process vents on 

condensers and distillation units. 

The PEPO NESHAP (40 CFR 63.1425) 

specifies control requirements for 

process vents, based on the PEPO 

polymerization process (i.e., 

polymerization using epoxides versus 

using THF). For PEPO processes that 

use epoxides as the reactant, the PEPO 

NESHAP specifies emissions limits for: 

(1) epoxide emissions, (2) nonepoxide 

organic HAP emissions from processes 

that use nonepoxide HAP to make or 

modify the product, and (3) nonepoxide 

organic HAP emissions from catalyst 

extraction. For the epoxide standards, 

the PEPO NESHAP (40 CFR 63.1425(b)) 

requires owners or operators to either: 

(1) reduce emissions at existing sources 

by 98 percent and new sources by 99.9 

percent; (2) control emissions using a 

flare (existing sources only); (3) achieve 

an outlet concentration of 20 parts per 

million by volume (ppmv) or less; or (4) 

limit emissions to 1.69 × 10¥2 kilogram 

of epoxide per megagram of product at 

existing sources and 4.43 × 10¥3

kilogram of epoxide per megagram of 

product at new sources. We provide 

more details about process vents in our 

technology review discussion (see 

section IV.C.3 of this preamble) 

including specifics about the process 

vent standards for nonepoxide organic 

HAP emissions from processes that use 

nonepoxide HAP to make or modify the 

product, and for nonepoxide organic 

HAP emissions from catalyst extraction. 

PEPO facilities use storage vessels to 

hold liquid and gaseous feedstocks for 

use in a process, as well as to store 

liquid and gaseous products from a 

process. Facilities typically store EtO 

under pressure as a liquified gas, but 

EtO may also be found in small amounts 

in atmospheric storage vessels storing 

liquid products that use EtO as a 

reactant in their production. Typical 

emissions from atmospheric storage 

tanks occur from working and breathing 

losses, while pressure vessels are 

considered closed systems and, if 

properly maintained and operated, 

should have virtually no emissions. In 

some instances, there may be low levels 

of fugitive emissions from pressure 

vessels, and pressure vessels storing 

liquefied gases may be vented 

periodically to purge inerts. 

The PEPO NESHAP (40 CFR 63.1432) 

cites the control provisions specified in 

the HON (40 CFR 63.119 through 

63.123) which require owners or 

operators determine Group 1 or Group 

2 designations of affected storage 

vessels, based on the volume of the 

storage vessel and maximum true vapor 

pressure (MTVP) of the material stored. 

Group 1 storage vessels are those with 

capacities between 75 m3 (inclusive) 

and 151 m3 and a MTVP greater than or 

equal to 13.1 kilopascals (kPa), and 

those with capacities greater than or 

equal to 151 m3 and a MTVP greater 

than or equal to 5.2 kPa. The HON 

storage vessel standards that PEPO 

affected sources are currently subject 

to 30 require Group 1 storage vessels to 

reduce total HAP emissions by 95 

percent (or 90 percent if the storage 

vessel was installed on or before 

December 31, 1992) by venting 

emissions through a closed vent system 

to any combination of control devices or 

to vent emissions through a closed vent 

system to a flare. Owners and operators 

of Group 1 storage vessels storing a 

liquid with a MTVP of total organic 

HAP less than 76.6 kPa are also allowed 

to reduce organic HAP by utilizing an 

internal floating roof (IFR), an external 

floating roof (EFR), an EFR converted to 

an IFR, vapor balancing, or by routing 

the emissions to a process or a fuel gas 

system. For Group 1 storage vessels 

storing a liquid with a MTVP of total 

organic HAP greater than or equal to 

76.6 kPa, owners and operators can 

reduce organic HAP emissions by 95 

percent by venting emissions through a 

closed vent system to any combination 

of control devices, controlling emissions 

by routing them to a process or a fuel 

gas system, or by using vapor balancing. 

Pressure vessels (operating in excess of 

204.9 kPa without emissions to the 

atmosphere) may also store materials 

with EtO. For storage vessels, the PEPO 

NESHAP, by reference to the HON, 

allows use of a design evaluation 

instead of a performance test to 

determine the percent reduction of 

control devices for any quantity of total 

uncontrolled organic HAP emissions 

being sent to the control device. We 

provide more details about storage 

vessels in our technology review 

discussion (see section IV.C.2 of this 

preamble). 

Based on results from the risk 

assessment, we determined that the 

current MACT standards for PEPO 

process vents and storage vessels do not 

result in sufficient control of EtO 

emissions to prevent unacceptable risk. 

For example, emissions of EtO from 

PEPO process vents and storage vessels 

contribute to 72 percent of one facility’s 

maximum individual cancer risk of 500- 

in-1 million. Therefore, we evaluated 

available control technologies with a 

higher level of control, as discussed 

below. 

To lower the risk for PEPO facilities 

with EtO emissions, we analyzed a 

control option for process vents and 

storage vessels that are in EtO service 

which requires all process vents and 

storage vessels in EtO service to be 

controlled. This control option is based 

on requirements that were recently 

finalized in the MON and HON because 

of unacceptable risk (see 85 FR 49084, 

August 12, 2020, and 89 FR 42932, May 

16, 2024, respectively). The definitions 

of process vents and storage vessels ‘‘in 

ethylene oxide service’’ from the MON 

and HON are presented here: 

• For process vents, ‘‘in ethylene 

oxide service’’ means, when 

uncontrolled, each process vent 

contains a concentration of greater than 

or equal to 1 ppmv undiluted EtO, and 

when combined, the sum of all process 

vents within the process would emit 

uncontrolled EtO emissions greater than 

or equal to 5 lb/yr. 

• For storage vessels of any capacity 

and vapor pressure, ‘‘in ethylene oxide 

service’’ means that the concentration of 

EtO within the tank liquid is greater 

than or equal to 0.1 percent by weight. 

The MON and HON standards for 

process vents and storage vessels in EtO 

service, require owners and operators to 

route emissions through a closed vent 


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system to a: (1) control device that 

reduces EtO by at least 99.9 percent by 

weight or to a concentration less than 1 

ppmv for each process vent and storage 

vessel vent (or, for multiple process 

vents within a process, to less than 5 lb/ 

yr for all combined process vents), or (2) 

flare meeting certain flare operating and 

monitoring requirements. 

To ensure emissions from PEPO 

affected sources are controlled to an 

acceptable level of risk under the PEPO 

NESHAP, we are proposing to 

incorporate the same EtO emissions 

standards for process vents and storage 

vessels from the MON and HON into the 

PEPO NESHAP. Specifically, we are 

proposing at 40 CFR 63.1423(b) to refer 

to subpart F of the HON which defines 

the term ‘‘in ethylene oxide service’’ for 

process vents to mean each process vent 

in a process that, when uncontrolled, 

contains a concentration of greater than 

or equal to 1 ppmv undiluted EtO, and 

when combined, the sum of all these 

process vents within the process would 

emit uncontrolled EtO emissions greater 

than or equal to 5 pounds per year (lb/ 

yr) (2.27 kilograms per year, kg/yr). We 

are also proposing to update the 

definition of ‘‘process vent’’ at 40 CFR 

63.1423(b) to align with this proposed 

change. We are also proposing in the 

PEPO NESHAP at 40 CFR 63.1423(b) to 

refer to subpart F of the HON which 

defines the term ‘‘in ethylene oxide 

service’’ for storage vessels to mean that 

the concentration of EtO of the stored 

liquid is at least 0.1 percent by weight. 

We are also proposing that the 

exemption for ‘‘vessels and equipment 

storing and/or handling material that 

contains no organic HAP, or organic 

HAP as impurities only’’ listed in the 

definition of ‘‘storage vessel’’ at 40 CFR 

63.1423(b) does not apply for storage 

vessels in EtO service. We are proposing 

procedures for determining whether 

process vents and/or storage vessels are 

in EtO service within the proposed 

definition of the term ‘‘in ethylene oxide 

service’’ (by reference to 40 CFR 63.109 

for PEPO process vents and storage 

vessels in EtO service). We are 

proposing at 40 CFR 63.1425(g) that 

PEPO process vents in EtO service 

either reduce emissions of EtO by: (1) 

venting emissions through a closed vent 

system to a non-flare control device that 

reduces EtO by at least 99.9 percent by 

weight, or to a concentration less than 

1 ppmv for each process vent, or to less 

than 5 lb/yr for all combined process 

vents within the process; or (2) routing 

emissions through a closed vent system 

to a flare meeting the proposed flare 

operating requirements discussed in 

section IV.D.1 of this preamble (see 

proposed 40 CFR 63.1436). We are 

proposing at 40 CFR 63.1432(a) by 

reference to the HON (40 CFR 

63.119(a)(5)) that PEPO storage vessels 

in EtO service either reduce emissions 

of EtO by: (1) venting emissions through 

a closed vent system to a non-flare 

control device that reduces EtO by at 

least 99.9 percent by weight or to a 

concentration less than 1 ppmv for each 

storage tank vent; or (2) venting 

emissions through a closed vent system 

to a flare meeting the proposed flare 

operating requirements discussed in 

section IV.D.1 of this preamble (see 

proposed 40 CFR 63.1436). We are 

proposing procedures to determine 

compliance with these proposed EtO 

standards at 40 CFR 63.1426(g) (by 

reference to 40 CFR 63.124 for PEPO 

process vents in EtO service) and 40 

CFR 63.1432(v) (by reference to 40 CFR 

63.124 for PEPO storage vessels in EtO 

service). In section IV.D.1 of this 

preamble, we recognized flares cannot 

achieve 99.9 percent EtO reduction. We 

also noted that as part of the CAA 

section 114 request, five facilities 

measured EtO emissions from their EtO 

emission points and only one of these 

five facilities currently use a flare to 

control EtO emissions from process 

vents or storage vessels. Even so, our 

modeling file does include several other 

PEPO facilities that do use flares to 

control process vents and storage 

vessels that emit EtO. Therefore, we 

accounted for these flares operating at 

98 percent EtO reduction in our risk 

assessment and determined that it is not 

necessary for flares to achieve 99.9 

percent EtO reduction to reduce risk to 

an acceptable level and provide an 

ample margin of safety to protect public 

health (provided that owners and 

operators still comply with the entire 

suite of EtO control requirements that 

we are proposing in this action). 

Additionally, we propose removing 

the option to allow use of a design 

evaluation in lieu of performance testing 

to demonstrate compliance for storage 

vessels in EtO service to ensure that the 

required level of control is achieved (see 

proposed 40 CFR 63.1432(v) by 

reference to the HON (40 CFR 

63.124(a)(2)(i) and (b)(3))). We are also 

proposing that after promulgation of the 

rule, owners or operators that choose to 

control emissions with a non-flare 

control device conduct an initial 

performance test according to proposed 

40 CFR 63.1426(g) and 63.1432(v) by 

reference to the HON (40 CFR 63.124) 

on each existing control device in EtO 

service and on each newly installed 

control device in EtO service to verify 

performance at the required level of 

control. We are also proposing at 40 

CFR 63.1426(g) and 63.1432(v) by 

reference to the HON (40 CFR 63.124(b)) 

that owners or operators conduct 

periodic performance testing on nonflare control devices in EtO service 

every 5 years. 

Finally, we are proposing at 40 CFR 

63.1427(a) that owners and operators 

may not use the extended cookout 

(ECO) pollution prevention technique to 

show compliance with the proposed 

standard for PEPO process vents in EtO 

service. The PEPO NESHAP at 40 CFR 

63.1427(a) allows the use of ECO as a 

means of reducing epoxide emissions by 

the required percentage (98 or 99.9 

percent) or complying with the 

production-based limit (≤1.69 × 10¥2 or 

4.43 × 10¥3 kilograms of epoxide 

emissions per megagram of product 

made). This pollution prevention 

technique reduces emissions by 

extending the time of reaction, thus 

leaving less unreacted epoxides to be 

emitted downstream. To demonstrate a 

percent efficiency, it is necessary to 

designate the basis, or the 

‘‘uncontrolled’’ emissions, for assessing 

the percent reduction. The point where 

uncontrolled emissions are to be 

assessed, called the ‘‘onset’’ of the ECO, 

is defined in the PEPO NESHAP at 40 

CFR 63.1427(c) as the point when the 

epoxide concentration in the reactor 

liquid is equal to 25 percent of the 

concentration of epoxide in the liquid at 

the end of the epoxide feed. Procedures 

to calculate epoxide emissions at the 

end of ECO are provided in 40 CFR 

63.1427(d). The EPA determined the 

default onset of ECO based on CBI from 

the Society of the Plastics Industry, 

which indicated the economic 

breakpoint for when a cookout is no 

longer economically advantageous (see 

62 FR 46804, September 4, 1997). 

However, new economic conditions 

suggest the ECO compliance option may 

no longer be viable. For instance, one 

facility reported, in response to the 

EPA’s CAA section 114 request, that 

their customers require less than 1 ppm 

residual EtO, i.e., it is economically 

advantageous to continue the reaction 

until 1 ppm is reached. It is impractical 

to achieve a 99.9 percent reduction from 

an onset of 1 ppm. Additionally, using 

the current definition of onset, ECO 

could lead to high EtO emissions 

relative to the starting amount of 

epoxide used. Therefore, we believe it is 

not appropriate to continue allowing the 

ECO pollution prevention technique to 

demonstrate compliance with the 

proposed EtO emissions standards (i.e., 

reduce EtO by at least 99.9 percent by 

weight) that are intended to control 


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Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 106009 

31Although the original proposal for the PEPO 

NESHAP (62 FR 46804, September 4, 1997) 

mentions that the method for determining these 

emission factors is detailed in the Supplementary 

Information Document, we could not locate this 

derivation in the document titled Hazardous Air 

Pollutant Emissions from the Production of 

Polyether Polyols—Supplementary Information 

Document for Proposed Standards. 

emissions from process vents and 

storage vessels to an acceptable risk 

level. We are also proposing that it is 

not appropriate to continue to allow the 

existing production-based limits (i.e., 

≤1.69 × 10¥2 or 4.43 × 10¥3 kilograms 

of epoxide emissions per megagram of 

product made) in place of the new EtO 

emissions standards. The 1.69 × 10¥3

production-based limit is an alternative 

to the 98 percent emission reduction 

standard for existing affected sources 

which is not as stringent as the 

proposed 99.9 percent emission 

reduction standard for EtO. While the 

4.43 × 10¥3 production-based limit is an 

alternative to the 99.9 percent emission 

reduction standard for new affected 

sources, it is related to the aggregate 

reduction of total epoxide emissions 

and not specifically to EtO emissions. 

Additionally, it is not clear how these 

production-based limits (also referred to 

‘‘as emission factors’’) were derived 31

and we do not have enough information 

to set a new production-based limit that 

would be equivalent to the proposed 

EtO emissions standards. 

See the document titled Analysis of 

Control Options for Process Vents and 

Storage Vessels to Reduce Residual Risk 

of Ethylene Oxide in the PEPO 

Production Source Category, which is 

available in the docket for this action, 

for more information on the control 

option the EPA evaluated to reduce EtO 

risk from PEPO process vents and 

storage vessels. 

b. Equipment Leaks 

Emissions of EtO from equipment 

leaks occur in the form of gases or 

liquids that escape to the atmosphere 

through connection points (e.g., 

threaded fittings) or through the moving 

parts of valves, pumps, compressors, 

PRDs, and certain types of process 

equipment. The PEPO NESHAP defines 

equipment leaks as ‘‘emissions of 

organic HAP from a connector, pump, 

compressor, agitator, pressure relief 

device, sampling connection system, 

open-ended valve or line, valve, surge 

control vessel, bottoms receiver, or 

instrumentation system in organic HAP 

service.’’ The equipment leak 

requirements apply to equipment that 

contain or contact material that are 5 

percent by weight or more of organic 

HAP, operate 300 hours per year or 

more, and are not in vacuum service. 

The PEPO NESHAP requirements for 

equipment leaks directly reference the 

provisions in 40 CFR part 63, subpart H 

(which is part of the HON). The HON 

equipment leak requirements vary by 

equipment component type, but require 

LDAR using monitoring with EPA 

Method 21 of appendix A–7 to 40 CFR 

part 60 at certain frequencies (e.g., 

monthly, quarterly, every 2 quarters, 

annually) and varying leak definitions 

(e.g., 500 ppmv; 1,000 ppmv; 10,000 

ppmv) depending on the type of service 

(e.g., gas and vapor service or in light 

liquid service). The LDAR requirements 

for components in heavy liquid service 

include sensory monitoring and the use 

of EPA Method 21 monitoring if a leak 

is identified. We provide more details 

about equipment leaks in our 

technology review discussion (see 

section IV.C.5 of this preamble). 

Results from our risk assessment 

indicate that, for the source category 

MIR of 1,000-in-1 million, more than 20 

percent is from emissions of EtO related 

to PEPO equipment leaks. We also note 

that the risk from EtO from PEPO 

equipment leaks at three facilities 

(including the facility driving the MIR) 

is ≥100-in-1 million. To help reduce the 

risk associated with EtO emissions from 

equipment leaks in the PEPO 

Production source category, we 

performed a review of available 

measures for reducing EtO emissions 

from components that are most likely to 

be in EtO service, which include 

connectors (in gas and vapor service or 

light liquid service), pumps (in light 

liquid service), and valves (in gas or 

light liquid service). We identified 

options for further strengthening LDAR 

practices to find and repair equipment 

leaks from these three pieces of 

equipment more quickly, including 

lowering the leak definitions and/or 

requiring more frequent monitoring 

with EPA Method 21 of appendix A–7 

to 40 CFR part 60, which align with the 

recently finalized EtO standards for 

equipment leaks in the HON (89 FR 

42932, May 16, 2024). 

For gas/vapor and light liquid 

connectors in EtO service, we identified 

two options: (1) require connector 

monitoring at a leak definition of 500 

ppmv with annual monitoring and no 

reduction in monitoring frequency (i.e., 

no skip periods), and (2) require 

connector monitoring at a leak 

definition of 100 ppmv with annual 

monitoring and no reduction in 

monitoring frequency. 

For light liquid pumps in EtO service, 

we identified three options: (1) lower 

the leak definition from 1,000 ppmv to 

500 ppmv with monthly monitoring, (2) 

lower the leak definition from 1,000 

ppmv to 100 ppmv with monthly 

monitoring, or (3) require the use of 

leakless pumps (i.e., canned pumps, 

magnetic drive pumps, diaphragm 

pumps, pumps with tandem mechanical 

seals, pumps with double mechanical 

seals) with annual monitoring and a 

leak defined as any reading above 

background concentration levels. 

For gas/vapor and light liquid valves 

in EtO service, we identified two 

options: (1) require a leak definition of 

500 ppmv with monthly monitoring and 

no reduction in monitoring frequency, 

and (2) lower the leak definition from 

500 ppmv to 100 ppmv with monthly 

monitoring and no reduction in 

monitoring frequency. 

Due to the high residual risk for some 

of the facilities from equipment leaks of 

EtO and the potential need for greater 

emission reduction to meet an 

acceptable level of risk for the PEPO 

Production source category, we also 

evaluated a more stringent combined 

option which requires monthly 

monitoring for valves (in gas/vapor and 

light liquid service), connectors (in gas/ 

vapor and light liquid service), and 

pumps (light liquid service) in EtO 

service at a leak definition of 100 ppmv 

for valves and connectors and 500 ppmv 

for light liquid pumps using EPA 

Method 21 of appendix A–7 to 40 CFR 

part 60. This combined option also does 

not allow equipment in EtO service to 

be monitored less frequently with skip 

periods, nor does the option allow 

facilities to take advantage of the delay 

of repair provisions. We analyzed 

increasing the monitoring frequency to 

monthly for connectors because they are 

the most numerous equipment 

components at chemical facilities, and 

they are the most significant 

contribution to the baseline emissions 

from leaking equipment at the EtOemitting facilities. 

For the component-specific control 

options, we calculated the EtO baseline 

emissions and emissions after 

implementation of controls for each 

facility using average volatile organic 

compound (VOC) emission rates for 

each component, and the component 

counts and the EtO weight percent of 

the process from the responses to the 

EPA’s CAA section 114 request. For the 

combined option of monthly monitoring 

of gas and light liquid valves and 

connectors at 100 ppmv and light liquid 

pumps at 500 ppmv, we do not have 

emission factors to estimate reductions 

for increased monitoring frequencies for 

connectors. Where a simplified 

emission factor method for determining 

the potential reductions of applying the 


jspears on DSK121TN23PROD with PROPOSALS
106010 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

32 Gas Plant Equipment Leak Monte Carlo Model 

Code and Instructions. October 21, 2021. EPA 

Docket No. EPA–HQ–OAR–2021–0317. Control 

Options for Equipment Leaks at Gasoline 

Distribution Facilities. October 20, 2021. EPA 

Docket No. EPA–HQ–OAR–2020–0371. 

33See 40 CFR 63.101. 

34See appendix B in the document titled: The Air 

Stripping Method (Modified El Paso Method) for 

Determination of Volatile Organic Compound 

(VOC) Emissions from Water Sources, which is 

included in the docket for this rulemaking. 

option did not exist, we estimated 

emissions reductions based on the 

approach used in other rules,32 where 

detailed leak data or an assumed leak 

distribution were available. The 

equipment leaks model uses a Monte 

Carlo analysis to estimate emissions 

from EtO facility equipment leaks. The 

memorandum Analysis of Control 

Options for Equipment Leaks to Reduce 

Residual Risk of Ethylene Oxide in the 

PEPO Production Source Category, 

which is available in the docket for this 

action, provides a detailed discussion of 

the model. 

In this action, we are also proposing 

the same definition for the term ‘‘in 

ethylene oxide service’’ for equipment 

as used in the final amendments to the 

HON (89 FR 42932, May 16, 2024).33

For equipment leaks, we are proposing 

to define ‘‘in ethylene oxide service’’ in 

the PEPO NESHAP at 40 CFR 63.1423(b) 

(by reference to 40 CFR 63.101) to mean 

any equipment that contains or contacts 

a fluid (liquid or gas) that is at least 0.1 

percent by weight of EtO. We are 

proposing procedures for determining 

whether equipment is in EtO service 

within the proposed definition of the 

term ‘‘in ethylene oxide service’’ (by 

reference to 40 CFR 63.109 for PEPO 

equipment in EtO service). We are 

proposing that any piece of equipment 

that is in ethylene oxide service is also 

in organic HAP service. For PEPO 

equipment in EtO service, to achieve 

greater emissions reductions to help 

meet an acceptable level of risk for the 

PEPO Production source category, we 

are proposing the following combined 

requirements: monitoring of connectors 

in gas/vapor and light liquid service at 

a leak definition of 100 ppmv on a 

monthly basis with no reduction in 

monitoring frequency or delay of repair; 

monthly monitoring of light liquid 

pumps at a leak definition of 500 ppmv; 

and monthly monitoring of gas/vapor 

and light liquid valves at a leak 

definition of 100 ppmv with no 

reduction in monitoring frequency or 

delay of repair (see proposed 40 CFR 

63.1434(a) by reference to the HON). 

The document titled Analysis of Control 

Options for Equipment Leaks to Reduce 

Residual Risk of Ethylene Oxide in the 

PEPO Production Source Category, 

which is available in the docket for this 

action, provides additional information 

on all evaluated control options to 

reduce EtO risk from PEPO equipment 

leaks. 

c. Heat Exchange Systems 

Emissions of EtO from heat exchange 

systems occur due to corrosion or cracks 

in internal tubing materials, which 

allows some process fluids to mix or 

become entrained with the cooling 

water. Pollutants (e.g., EtO) in the 

process fluids may subsequently be 

released from the cooling water into the 

atmosphere when the water is exposed 

to air (e.g., in a cooling tower for closedloop systems or trenches/ponds in a 

once-through system). The HON heat 

exchange system standards that PEPO 

affected sources are currently subject to 

require owners or operators to monitor 

heat exchange systems for leaks of 

process fluids into cooling water and 

take actions to repair leaks within 45 

days if they are detected (facilities may 

delay the repair of leaks if they meet 

certain criteria). To comply with the 

provisions, owners or operators can use 

any method listed in 40 CFR part 136 

to sample cooling water for leaks for the 

HAP listed in table 4 to subpart F 

(recirculating systems) and table 9 to 

subpart G (once-through systems) (and 

other representative substances such as 

total organic compounds (TOC) or VOC 

that can indicate the presence of a leak 

can also be used). In addition, owners 

or operators can monitor for leaks using 

a surrogate indicator (e.g., ion specific 

electrode monitoring, pH, conductivity), 

provided that they meet certain criteria 

in 40 CFR 63.104(c). We provide more 

details about heat exchange systems in 

our technology review discussion (see 

section IV.C.1 of this preamble). 

For heat exchange systems, we found 

that, while we did not identify a report 

of EtO emissions from a PEPO heat 

exchange system leak, a model using 

representative leaks (and the current 

standards for monitoring and repair) 

indicated that a potential leak currently 

allowed by the PEPO NESHAP 

containing EtO from a facility’s cooling 

tower could significantly contribute to 

unacceptable risk. Thus, we are 

proposing to use the same definition of 

the term ‘‘in ethylene oxide service’’ as 

used in the final amendments to the 

HON (89 FR 42932, May 16, 2024). We 

are proposing in the PEPO NESHAP at 

40 CFR 63.1423 to refer to subpart F of 

the HON which defines the term ‘‘in 

ethylene oxide service’’ for heat 

exchange systems to mean any heat 

exchange system in a process that cools 

process fluids (liquid or gas) that are 0.1 

percent or greater by weight of EtO. We 

are proposing procedures for 

determining whether heat exchange 

systems are in EtO service within the 

proposed definition of the term ‘‘in 

ethylene oxide service’’ (by reference to 

40 CFR 63.109 for PEPO heat exchange 

systems in EtO service). We are 

proposing that any heat exchange 

system that is in ethylene oxide service 

is also in organic HAP service. To 

address risk from EtO allowable 

emissions due to PEPO heat exchange 

system leaks, we evaluated the 

following option for PEPO heat 

exchange systems ‘‘in ethylene oxide 

service’’ which: (1) requires use of the 

Modified El Paso Method (see section 

IV.C.1 of this preamble), (2) requires 

quarterly monitoring using the Modified 

El Paso Method, (3) reduces the allowed 

amount of repair time from 45 days after 

finding a leak to 15 days from the 

sampling date, and (4) prohibits delay of 

repair. We also evaluated this same 

option except with varying monitoring 

frequencies (i.e., monthly and weekly) 

instead of quarterly. Using equation 7– 

2 from appendix P of the Texas 

Commission on Environmental 

Quality’s (TCEQ) Sampling Procedures 

Manual,34 model leak distributions and 

concentrations, and other model input 

parameters, we anticipate the quarterly 

option would reduce EtO emissions 

from leaking PEPO heat exchange 

systems by 54 percent because owners 

or operators would identify and repair 

leaks more quickly, which is needed to 

help reduce potential unacceptable risk 

from the PEPO Production source 

category. See section IV.B.4 of this 

preamble for an analysis of the monthly 

and weekly options to provide an ample 

margin of safety. We are proposing 

weekly monitoring at 40 CFR 63.1435(a) 

by reference to the HON (40 CFR 

63.104(g)(6)) based on that ample 

margin of safety analysis. The document 

titled Analysis of Control Options for 

Heat Exchange Systems to Reduce 

Residual Risk of Ethylene Oxide in the 

PEPO Production Source Category, 

which is available in the docket for this 

action, provides additional information 

on this evaluated control option to 

reduce EtO risk from PEPO heat 

exchange systems. 

d. Wastewater 

EtO is emitted from wastewater 

collection, storage, and treatment 

systems that are uncovered or open to 

the atmosphere through volatilization of 

the compound at the liquid surface. 

Emissions occur by diffusive or 

convective means, or both. Diffusion 

occurs when organic pollutant 


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35The Fr is the fraction of a HAP that is stripped 

from wastewater and is an indicator of the extent 

to which a HAP is effectively removed during the 

steam stripping process, which for EtO is 98 

percent. 

concentrations at the water surface are 

much higher than ambient 

concentrations. The organic pollutants 

volatilize, or diffuse into the air, to 

reach equilibrium between the aqueous 

and vapor phases. Convection occurs 

when air flows over the water surface, 

sweeping organic vapors from the water 

surface into the air. The rate of 

volatilization is related directly to the 

speed of the air flow over the water 

surface. 

The HON wastewater standards that 

PEPO affected sources are currently 

subject to (40 CFR 63.1433 cites the 

control provisions specified in the HON 

at 40 CFR 63.132 through 63.147) divide 

wastewater streams into Group 1 

wastewater streams, which require 

controls, and Group 2 wastewater 

streams, which generally do not require 

controls provided they do not exceed 

Group 1 thresholds. The Group 1 and 

Group 2 designations for wastewater 

streams are based on volumetric flow 

rate and total annual average organic 

HAP concentration. The HON specifies 

performance standards for treating 

Group 1 wastewater streams using open 

or closed biological treatment systems 

or using a design steam stripper with 

vent control. For APCDs (e.g., thermal 

oxidizers) used to control emissions 

from collection system components, 

steam strippers, or closed biological 

treatment, the HON provides owners or 

operators several compliance options 

including achieving a 95-percent 

destruction efficiency, achieving a 20- 

ppmv outlet concentration, or 

implementing design specifications for 

temperature and residence time. We 

provide more details about wastewater 

streams in our technology review 

discussion (see section IV.C.4 of this 

preamble). 

The results from our risk assessment 

show that EtO emissions from 

wastewater contribute 77 percent of the 

source category MIR (the MIR is 1,000- 

in-1-million), thus wastewater is one of 

the EtO emission sources contributing to 

the EPA’s finding of unacceptable risk 

for the PEPO Production source 

category. To lower the risk for the PEPO 

facilities with EtO emissions, we are 

proposing at 40 CFR 63.1423(b) to use 

the same definition of the term ‘‘in 

ethylene oxide service’’ for wastewater 

as used in the recently amended HON 

(89 FR 42932, May 16, 2024) which 

means any wastewater stream that 

contains total annual average 

concentration of EtO greater than or 

equal to 1 part per million by weight 

(ppmw) at any flow rate. We are 

proposing procedures for determining 

whether a wastewater stream is in EtO 

service within the proposed definition 

of the term ‘‘in ethylene oxide service’’ 

(by reference to 40 CFR 63.109 for PEPO 

wastewater streams in EtO service). We 

are also proposing, by reference to the 

amended HON, that a wastewater 

stream in EtO service would be 

considered a Group 1 wastewater stream 

(see 40 CFR 63.1433(a)(23) and (27) and 

63.132(c)(1)(iii) and (d)(1)(ii)). In 

addition, we are proposing to update the 

definition of ‘‘wastewater’’ at 40 CFR 

63.1423(b) to align with these proposed 

changes. As part of the management and 

treatment requirements for Group 1 

wastewater streams, owners and 

operators would be required at 40 CFR 

63.138(b)(3) and (c)(3) to reduce, by 

removal or destruction, the 

concentration of EtO to a level less than 

1 ppmw. We anticipate that owners and 

operators will use stream stripping to 

comply with this proposed requirement. 

While we acknowledge EtO can be 

biodegraded, the compound is not on 

table 37 to subpart G of the HON, 

suggesting that it is not a readily 

biodegradable compound when using a 

biological treatment method, and EtO 

would need to be stripped out of the 

wastewater to meet the standard at 40 

CFR 63.138(b)(3) and (c)(3). Therefore, 

we evaluated Control Option 1 using a 

steam stripper achieving a 98 percent 

reduction of EtO emissions (based on 

the fraction removed (Fr) value of EtO 35

in table 9 to subpart G of the HON). 

Additionally, we are aware that some 

chemical manufacturing facilities 

dispose of certain wastewater streams 

that contain EtO by adding those 

wastewaters to the cooling water of their 

heat exchange systems, rather than 

considering those EtO-containing 

streams to be potential sources of 

wastewater. To help reduce risk from 

the PEPO Production source category by 

eliminating these types of EtO emissions 

from wastewater being injected into heat 

exchange systems, we are also 

proposing to prohibit owners and 

operators from injecting water into or 

disposing of water through any heat 

exchange system in a PMPU meeting the 

conditions of 40 CFR 63.1420 if the 

water contains any amount of EtO, has 

been in contact with any process stream 

containing EtO, or the water is 

considered wastewater as defined in 40 

CFR 63.1423 (see 40 CFR 63.1435(i). 

The document titled Analysis of Control 

Options for Wastewater Streams to 

Reduce Residual Risk of Ethylene Oxide 

in the PEPO Production Source 

Category, which is available in the 

docket for this action, provides 

additional information on this evaluated 

control option to reduce EtO risk from 

PEPO wastewater streams. 

e. Summary 

For process vents, storage vessels, 

equipment leaks, heat exchange 

systems, and wastewater, we considered 

the control options described above for 

reducing EtO risk from the PEPO 

Production source category that are 

associated with processes subject to the 

PEPO NESHAP. To reduce risk from the 

source category to an acceptable level, 

we propose to require control of EtO 

emissions from: (1) process vents, (2) 

storage vessels, (3) equipment leaks, (4) 

heat exchange systems, and (5) 

wastewater in EtO service, as defined in 

this proposal. For process vents and 

storage vessels in EtO service, we are 

proposing owners and operators reduce 

emissions of EtO by either: (1) venting 

emissions through a closed vent system 

to a non-flare control device that 

reduces EtO by greater than or equal to 

99.9 percent by weight or to a 

concentration less than 1 ppmv for each 

process vent and storage vessel, or (2) 

venting emissions through a closed vent 

system to a flare meeting the proposed 

operating and monitoring requirements 

for flares (see section IV.D.1 of this 

preamble). For process vents, we are 

also proposing an annual limit of 5 lb/ 

yr or less for all combined process vents 

as an alternative to the percent control 

and concentration options. For 

equipment leaks in EtO service, we are 

proposing the following combined 

requirements: monitoring of connectors 

in gas/vapor and light liquid service at 

a leak definition of 100 ppmv on a 

monthly basis with no reduction in 

monitoring frequency and no delay of 

repair; monthly monitoring of light 

liquid pumps at a leak definition of 500 

ppmv; and monthly monitoring of gas/ 

vapor and light liquid valves at a leak 

definition of 100 ppmv with no 

reduction in monitoring frequency and 

no delay of repair. For heat exchange 

systems in EtO service, we are 

proposing to require owners or 

operators to conduct more frequent leak 

monitoring (weekly instead of quarterly) 

and to repair leaks within 15 days from 

the sampling date (in lieu of the current 

45-day repair requirement after 

receiving results of monitoring 

indicating a leak), and to not allow 

owners or operators to delay repairs. For 

wastewater in EtO service, we are 

proposing to revise the Group 1 

wastewater stream threshold for sources 

to include wastewater streams in EtO 

service, and to prohibit owners and 


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1Owners or operators can also use a flare that 

meets the proposed requirements at 40 CFR 63.1436 

discussed in section IV.D.1 of this preamble). 

2Quarterly monitoring of heat exchange systems 

addresses the source category’s unacceptable risk, 

but the EPA is proposing to require weekly 

monitoring to provide an ample margin of safety. 

operators from injecting wastewater in 

EtO service into or disposing of water 

through any heat exchange system in a 

PMPU. 

In all cases, we are proposing that, if 

information exists that suggests EtO 

could be present in these processes, 

then the emission source is considered 

to be in EtO service unless the owner or 

operator conducts the procedures 

specified in 40 CFR 63.109 to 

demonstrate that the emission source 

does not meet the definition of being in 

EtO service (see proposed definition of 

the term ‘‘in ethylene oxide service’’ at 

40 CFR 63.1423(b) (by reference to 40 

CFR 63.101) and proposed 40 CFR 

63.1425(g) for process vents, 40 CFR 

63.1432(v) for storage vessels, 40 CFR 

63.1433(a)(27) for wastewater, 40 CFR 

63.1434(a)(6) for equipment leaks, and 

40 CFR 63.1435(j) for heat exchange 

systems). Examples of information that 

could suggest EtO is present in a process 

stream include calculations based on 

safety data sheets, material balances, 

process stoichiometry, or previous test 

results provided the results are still 

relevant to the current operating 

conditions. 

Based on the proposed applicability 

thresholds, we expect that up to 21 

PEPO facilities will be affected by one 

or more of the proposed EtO-specific 

standards; and we anticipate that all of 

these facilities will be subject to the 

process vent, storage vessel, equipment 

leak, heat exchange system, and 

wastewater EtO-specific provisions. 

3. Determination of Risk Acceptability 

After Proposed Emission Reductions 

As noted in sections II.A.1 and III.A 

of this preamble and in the 1989 

Benzene NESHAP, the EPA sets 

standards under CAA section 112(f)(2) 

using a two-step approach, with an 

analytical first step to determine 

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 38044, 38045/ 

col. 1, September 14, 1989). In the 1989 

Benzene NESHAP, the EPA explained 

that ‘‘[i]n establishing a presumption for 

MIR, rather than a rigid line for 

acceptability, the Agency intends to 

weigh it with a series of other health 

measures and factors’’ (Id., at 38045/col. 

3). ‘‘As risks increase above this 

benchmark, they become presumptively 

less acceptable under section 112, and 

would be weighed with the other health 

risk measures and information in 

making an overall judgement on 

acceptability’’ (Id.). 

Table 3 of this preamble presents the 

levels of emissions control proposed to 

address unacceptable risks for the PEPO 

Production source category, which 

includes reducing emissions of EtO for 

PEPO processes and requiring more 

stringent controls for process vents, 

storage vessels, equipment leaks, heat 

exchange systems, and wastewater 

without considering costs. 

TABLE 3—ETO RISK CONTROL OPTIONS FOR THE PEPO PRODUCTION SOURCE CATEGORY

Emission source 

(in EtO service) Description of proposed control option 

Percent 

reduction of 

EtO 

emissions 

Process Vent .............................. Route emissions through a closed vent system to a non-flare control device 1 that reduces 

EtO by greater than or equal to 99.9 percent by weight, to a concentration less than or 

equal to 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process 

vents 

99.9 

Storage Vessel ........................... Route emissions through a closed vent system to a non-flare control device 1 that reduces 

EtO by greater than or equal to 99.9 percent by weight or to a concentration less than or 

equal to 1 ppmv 

99.9 

Equipment Leaks ........................ For equipment components that are in EtO service, monthly monitoring using EPA Method 

21 of connectors in gas/vapor and light liquid service at a leak definition of 100 ppmv with 

no reduction in monitoring frequency and no repair delays; monthly monitoring of light liquid pumps at a leak definition of 500 ppmv; and monthly monitoring of gas/vapor and light 

liquid valves at a leak definition of 100 ppmv with no reduction in monitoring frequency 

and no delay of repair 

70 

Heat Exchange Systems ............ Quarterly 2 monitoring for leaks using the Modified El Paso Method and repair of leaks required no later than 15 days after the date sampling occurs. 54 

Wastewater ................................. Control all wastewater with a total annual average concentration of EtO greater than or 

equal to 1 ppmw at any flow rate as if it were a Group 1 wastewater 

98 

For the PEPO Production source 

category, after implementation of the 

proposed controls to address 

unacceptable risks, the MIR is reduced 

to 100-in-1 million (down from 1,000- 

in-1 million) with no facilities or 

populations exposed to risk levels 

greater than 100-in-1 million. The 

population exposed to risk levels greater 

than or equal to 1-in-1 million living 

within 50 km of affected facilities would 

be reduced from 3.8 million people to 

1.7 million people. The total estimated 

cancer incidence for the source category 

of 0.3 (pre-control) is reduced to 0.08 

(post-control) excess cancer cases per 

year. The maximum modeled chronic 

noncancer TOSHI for the source 

category remains unchanged. It is 

estimated to be 0.1 (for respiratory 

effects) with no populations estimated 

to be exposed to a TOSHI greater than 

1. The estimated worst-case off-site 

acute exposures to emissions from the 

PEPO Production source category also 

remain unchanged, with a maximum 

modeled acute noncancer HQ of 1 based 

on the REL for methoxytriglycol (a 

glycol ether). Acute impacts are deemed 

negligible for HAP for which acute HQs 

are less than or equal to 1. Table 4 of 

this preamble summarizes the reduction 

in cancer risks associated with the 

source category based on the proposed 

controls. More detail is available in the 

document titled Residual Risk 

Assessment for the Polyether Polyols 

(PEPO) Production Source Category in 

Support of the 2024 Risk and 


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Technology Review Proposed Rule, which is available in the docket for this 

rulemaking. 

TABLE 4—CANCER RISKS AFTER IMPLEMENTATION OF PROPOSED CONTROL FOR THE PEPO PRODUCTION SOURCE

CATEGORY

Control scenario MIR 

(x-in-1 million) 

Population 

(≥1-in-1 

million) 

Population 

(>100-in-1 

million) 

Cancer 

incidence 

Pre-Control Baseline ........................................................................................ 1,000 3,800,000 3,300 0.3 

Post-Control ..................................................................................................... 100 1,700,000 0 0.08 

As noted earlier in this section, the 

EPA considers an MIR of 

‘‘approximately 1-in-10 thousand’’ (i.e., 

100-in-1 million) to be the presumptive 

limit of acceptability (54 FR 38045, 

September 14, 1989) and the proposed 

controls lower the MIR of the PEPO 

Production source category to 100-in-1 

million. This is a significant reduction 

from the pre-control MIR of 1,000-in-1 

million. For noncancer effects, the EPA 

has not established under section 112 of 

the CAA a numerical range for risk 

acceptability as it has with carcinogens, 

nor has it determined that there is a 

bright line above which acceptability is 

denied. However, the Agency has 

established that, as exposure increases 

above a reference level (as indicated by 

a HQ or TOSHI greater than 1), 

confidence that the public will not 

experience adverse health effects 

decreases and the likelihood that an 

effect will occur increases. 

Therefore, considering all health 

information, including risk estimation 

uncertainty, the EPA proposes that the 

resulting risks after implementation of 

the proposed controls for the PEPO 

Production source category detailed in 

section IV.B.2 would be acceptable. We 

solicit comments on all the proposed 

control requirements to reduce risk to 

an acceptable level for the PEPO 

Production source category. 

4. Ample Margin of Safety Analysis 

The second step in the residual risk 

decision framework is a determination 

of whether the emission standards 

proposed to achieve an acceptable risk 

level provide an ample margin of safety 

to protect public health, or whether 

more stringent emission standards 

would be required for this purpose. In 

making this determination, we 

considered the health risk and other 

health information considered in our 

acceptability determination, along with 

additional factors not considered in the 

risk acceptability step, including costs 

and economic impacts of controls, 

technological feasibility, uncertainties, 

and other relevant factors, consistent 

with the approach of the 1989 Benzene 

NESHAP. Table 5 of this preamble 

summarizes the costs and EtO emission 

reductions we estimated for the 

proposed control requirements to 

reduce the risks to an acceptable level 

for the PEPO Production source 

category. For details on the assumptions 

and methodologies used in the costs and 

impacts analyses, see the technical 

documents titled, Analysis of Control 

Options for Process Vents and Storage 

Vessels to Reduce Residual Risk of 

Ethylene Oxide in the PEPO Production 

Source Category; Analysis of Control 

Options for Equipment Leaks to Reduce 

Residual Risk of Ethylene Oxide in the 

PEPO Production Source Category; 

Analysis of Control Options for Heat 

Exchange Systems to Reduce Residual 

Risk of Ethylene Oxide in the PEPO 

Production Source Category; and 

Analysis of Control Options for 

Wastewater Streams to Reduce Residual 

Risk of Ethylene Oxide in the PEPO 

Production Source Category, which are 

available in the docket for this 

rulemaking. We note that for three 

fugitive EtO emission sources (i.e., 

equipment leaks, heat exchange 

systems, and wastewater), the emission 

reductions (and subsequent cost 

effectiveness values for EtO) differ from 

reductions expected to occur from 

reported emissions inventories due to 

use of model plants, engineering 

assumptions made to estimate baseline 

emissions, and uncertainties in how 

fugitive emissions may have been 

calculated for reported inventories 

compared to our model plants analyses 

(see the aforementioned technical 

documents). 

TABLE 5—NATIONWIDE ETO EMISSION REDUCTIONS AND COST IMPACTS FOR CONTROL OPTIONS CONSIDERED FOR

PEPO PROCESSES

Control option 

Total capital 

investment 

(MM$) 

Total 

annualized 

costs 

(MM$/yr) 

EtO emission 

reductions 

(tpy) 

Cost-effectiveness 

($/ton EtO) 

A—Process Vent & Storage Vessel Controls .......................................... 2.55 2.91 10.8 269,400 

B—Equipment Leak Controls .................................................................. 0.06 1.23 20.3 60,600 

C—Heat Exchange System Controls ...................................................... 0.21 0.36 12.1 29,800 

D—Wastewater Controls ......................................................................... 14.4 5.75 312 18,400 

Total (A + B + C + D) ....................................................................... 17.2 10.2 355 28,700 

For the ample margin of safety 

analyses, we evaluated the cost and 

feasibility of available control 

technologies that could be applied to 

PEPO processes to reduce risks further, 

considering all of the health risks and 

other health information evaluated in 

the risk acceptability determination 

described above and the additional 

information that we can consider only 

in the ample margin of safety analysis 

(i.e., costs and economic impacts of 

controls, technological feasibility, 

uncertainties, and other relevant 

factors). We note that the EPA 

previously determined that the 

standards for the PEPO Production 

source category provide an ample 


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36See 89 FR 24110, April 5, 2024. 

margin of safety to protect public health 

(79 FR 17340, March 27, 2014), and that 

the most significant change since that 

determination was the revised 2016 IRIS 

inhalation URE for EtO. As such, we 

focused our ample margin of safety 

analysis on cancer risk for EtO since, 

even after application of controls 

needed to get risks to an acceptable 

level, EtO drives cancer risk and cancer 

incidence (i.e., 98 percent of remaining 

cancer incidence of 0.08 is from EtO) for 

the PEPO Production source category. 

For process vents, storage vessels, 

equipment leaks, and wastewater in the 

PEPO Production source category, we 

did not identify any other control 

options for EtO emissions beyond those 

proposed in this action to reduce risks 

to an acceptable level. Furthermore, the 

proposed EtO controls for process vents, 

storage vessels, equipment leaks, and 

wastewater to reduce risks to an 

acceptable level are far more stringent 

than other options we identified to 

control HAP generally (i.e., see sections 

IV.D and IV.C of this preamble). 

Therefore, we conclude that these 

controls to reduce EtO emissions from 

PEPO processes to reduce risks to an 

acceptable level would also provide an 

ample margin of safety to protect public 

health. 

For EtO emissions from leaks in heat 

exchangers, we found that weekly 

monitoring is a cost-effective option to 

provide an ample margin of safety. 

Considering the incremental cost 

effectiveness from quarterly to monthly 

($197,200 per ton of EtO emissions 

reductions) and from monthly to weekly 

($1,734,200 per ton of EtO emissions 

reductions) are within the range of 

accepted values of cost effectiveness for 

EtO reductions,36 we find it appropriate 

to propose the weekly option (which is 

required by the HON) to provide an 

ample margin of safety. For this reason, 

we are proposing weekly monitoring for 

leaks for heat exchange systems in EtO 

service using the Modified El Paso 

Method (see 40 CFR 63.1435(a) by 

reference to the HON (40 CFR 

63.104(g)(6)). If the owner or operator 

finds a leak, we are proposing to require 

repair of the leak to reduce the 

concentration or mass emissions rate 

below the applicable leak action level as 

soon as practicable, but no later than 15 

days after collecting the sample with no 

delay of repair allowed (see 40 CFR 

63.1435(a) by reference to the HON (40 

CFR 63.104(h)(6)). The document titled 

Analysis of Control Options for Heat 

Exchange Systems to Reduce Residual 

Risk of Ethylene Oxide in the PEPO 

Production Source Category, which is 

available in the docket for this action, 

provides additional information on this 

evaluated control option to reduce EtO 

risk from PEPO heat exchange systems. 

We solicit comments on the proposed 

control requirements to provide an 

ample margin of safety for the PEPO 

Production source category. 

5. Adverse Environmental Effects 

Based on our screening assessment of 

environmental risk presented in section 

IV.A.4 of this preamble, we did not 

identify any areas of concern with 

respect to environmental risk. 

Therefore, we have determined that 

HAP emissions from the PEPO 

Production source category do not result 

in an adverse environmental effect, and 

we are proposing that it is not necessary 

to set a more stringent standard to 

prevent, taking into consideration costs, 

energy, safety, and other relevant 

factors, an adverse environmental effect. 

C. What are the results and proposed 

decisions based on our technology 

review? 

In addition to the proposed EtOspecific requirements discussed in 

section IV.B.2 of this preamble, under 

CAA section 112(d)(6) we also evaluated 

developments in practices, processes, 

and control technologies for reducing 

HAP emissions from heat exchange 

systems, storage vessels, process vents, 

wastewater, and equipment leaks for 

processes subject to the PEPO NESHAP 

(see sections IV.C.1 through IV.C.5 of 

this preamble, respectively). We 

analyzed costs and emissions reductions 

for each emission source (e.g., process 

vents) and determined cost effectiveness 

(annualized cost/Mg or ton of emissions 

reduction) on a HAP basis. We also 

evaluated fenceline monitoring as a 

development in practices considered 

under CAA section 112(d)(6) for the 

purposes of managing fugitive emissions 

from sources subject to the PEPO 

NESHAP (see section IV.C.6 of this 

preamble). 

1. Standards for Heat Exchange Systems 

Heat exchangers are devices or 

collections of devices used to transfer 

heat from process fluids to another 

process fluid (typically water) without 

intentional direct contact of the process 

fluid with the cooling fluid (i.e., noncontact heat exchanger). There are two 

types of heat exchange systems: closedloop recirculation systems and oncethrough systems. Closed-loop 

recirculation systems use a cooling 

tower to cool the heated water leaving 

the heat exchanger and then return the 

newly cooled water to the heat 

exchanger for reuse. Once-through 

systems typically use surface freshwater 

(e.g., from a nearby river) as the influent 

cooling fluid to the heat exchangers, and 

the heated water leaving the system is 

then discharged from the facility. At 

times, the internal tubing material of a 

heat exchanger can corrode or crack, 

allowing some process fluids to mix or 

become entrained with the cooling 

water. Pollutants in the process fluids 

may subsequently be released from the 

cooling water into the atmosphere when 

the water is exposed to air (e.g., in a 

cooling tower for closed-loop systems or 

trenches/ponds in a once-through 

system). 

The PEPO NESHAP at 40 CFR 

63.1423 currently refers to the HON (40 

CFR 63.101) to define a heat exchange 

system as ‘‘a device or collection of 

devices used to transfer heat from 

process fluids to water without 

intentional direct contact of the process 

fluid with the water (i.e., non-contact 

heat exchanger) and to transport and/or 

cool the water in a closed-loop 

recirculation system (cooling tower 

system) or a once-through system (e.g., 

river or pond water).’’ We are proposing 

to delete the reference to the HON 

definition and instead define a heat 

exchange system in the PEPO NESHAP 

so it refers to a PMPU (see section IV.E.4 

of this preamble). The definition also 

clarifies that: (1) for closed-loop 

recirculation systems, the heat exchange 

system consists of a cooling tower, all 

PMPU heat exchangers that are in 

organic HAP service serviced by that 

cooling tower, and all water lines to and 

from these process unit heat exchangers; 

(2) for once-through systems, the heat 

exchange system consists of all heat 

exchangers that are in organic HAP 

service, servicing an individual PMPU 

and all water lines to and from these 

heat exchangers; (3) sample coolers or 

pump seal coolers are not considered 

heat exchangers for the purpose of this 

proposed definition and are not part of 

the heat exchange system; and (4) 

intentional direct contact with process 

fluids results in the formation of a 

wastewater. This definition also applies 

to heat exchange systems in EtO service 

as described in section IV.B.2.c of this 

preamble. 

The PEPO NESHAP requirements for 

heat exchange systems at 40 CFR 

63.1435, by reference to the HON (40 

CFR 63.104), includes an LDAR program 

for owners or operators of certain heat 

exchange systems that do not meet one 

or more of the conditions in 40 CFR 

63.104(a). The LDAR program specifies 

that owners or operators must monitor 

heat exchange systems for leaks of 

process fluids into cooling water and 

take actions to repair detected leaks 


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37The Modified El Paso Method uses a dynamic 

or flow-through system for air stripping a sample of 

the water and analyzing the resultant off-gases for 

VOC using a flame ionization detector (FID) 

analyzer. The method is described in detail in 

appendix P of the TCEQ’s Sampling Procedures 

Manual: The Air Stripping Method (Modified El 

Paso Method) for Determination of Volatile Organic 

Compound (VOC) Emissions from Water Sources. 

Appendix P is included in the docket for this 

rulemaking. 

within 45 days. Owners or operators 

may delay the repair of leaks if they 

meet the applicable criteria in 40 CFR 

63.104. The PEPO NESHAP allows 

owners or operators to use any method 

listed in 40 CFR part 136 to sample 

cooling water for leaks for the HAP 

listed in table 4 to 40 CFR part 63, 

subpart F (for HON) that is also listed 

in table 4 to 40 CFR part 63, subpart PPP 

(recirculating systems) and table 9 to 40 

CFR part 63, subpart G (for HON) that 

is also listed in table 4 to 40 CFR part 

63, subpart PPP (once-through systems) 

(and other representative substances 

such as TOC or VOC that can indicate 

the presence of a leak can also be used). 

A leak in the heat exchange system is 

detected if the exit mean concentration 

of HAP (or other representative 

substance) in the cooling water is at 

least 1 ppmw or 10 percent greater than 

(using a one-sided statistical procedure 

at the 0.05 level of significance) the 

entrance mean concentration of HAP (or 

other representative substance) in the 

cooling water. Furthermore, the PEPO 

NESHAP allows owners or operators to 

monitor for leaks using a surrogate 

indicator (e.g., ion-specific electrode 

monitoring, pH, conductivity), provided 

that certain criteria in 40 CFR 63.104(c) 

are met. The PEPO NESHAP initially 

requires 6 months of monthly 

monitoring for existing heat exchange 

systems. Thereafter, the frequency can 

be reduced to quarterly. The leak 

monitoring frequencies are the same 

whether the owner or operator uses 

water sampling and analysis or 

surrogate monitoring to identify leaks. 

As part of our technology review, we 

reviewed the criteria in 40 CFR 63.104 

that exempt certain heat exchange 

systems from the LDAR requirements in 

the PEPO NESHAP to see if the 

exemptions were still reasonable to 

maintain. We identified two criteria in 

40 CFR 63.104 dealing with oncethrough heat exchange systems meeting 

certain National Pollution Discharge 

Elimination System (NPDES) permit 

conditions (i.e., 40 CFR 63.104(a)(3) and 

(4)) that warranted further assessment. 

Once-through heat exchange systems 

typically have systems open to the air 

(e.g., open sewer lines, trenches, and 

ponds) that are utilized to transport 

used cooling water to a discharge point 

(e.g., an outfall) of a facility. This 

cooling water can also be mixed with 

other sources of water (e.g., cooling 

water used in once-through heat 

exchange systems in non-PEPO 

processes, stormwater, treated 

wastewater, etc.) in sewers, trenches, 

and ponds prior to discharge from the 

plant. If this point of discharge from the 

plant is into a ‘‘water of the United 

States,’’ the facility is required to have 

a NPDES permit and to meet certain 

pollutant discharge limits. In reviewing 

the requirements of 40 CFR 63.104(a)(3), 

we find that there is a clear disconnect 

between having a NPDES permit that 

meets certain allowable discharge limits 

(i.e., 1 part per million by volume 

(ppmv) or less above influent 

concentration, or 10 percent or less 

above influent concentration, whichever 

is greater) at the discharge point of a 

facility (e.g., outfall) versus being able to 

adequately identify a leak from a oncethrough heat exchange system, given 

that these systems are open to the 

atmosphere prior to this discharge point 

and, therefore, any volatile HAP leaking 

from a once-through heat exchange 

system would likely be emitted to the 

atmosphere prior to the NPDES outfall. 

Similarly, while the requirements of 40 

CFR 63.104(a)(4) allow facilities with 

once-through heat exchange systems 

that have certain requirements (i.e., the 

requirements of 40 CFR 63.104(a)(3) and 

(4)) incorporated into their NPDES 

permit to not comply with the 

requirements of 40 CFR 63.104(b) and 

63.104(c), we find this exemption to be 

problematic. Specifically, the NPDES 

requirements at 40 CFR 63.104(a)(4) lack 

the specificity of where a sample must 

be taken to adequately find and quantify 

a leak from a once-through heat 

exchange system (e.g., just prior to the 

outfall from the plant versus from the 

exit of the once-through heat exchange 

system prior to being open to 

atmosphere), what concentration and/or 

mass emissions rate constitutes a leak 

that must be fixed, how quickly a leak 

must be fixed, what pollutants must be 

adequately accounted for, and what test 

method(s)/surrogates facilities are 

allowed. As such, we find 40 CFR 

63.104(a)(4) to be inadequate in terms of 

being able to detect and repair leaks that 

are at least as equivalent to those that 

would be identified if once-through heat 

exchange systems were complying with 

40 CFR 63.104(b) or (c) instead. 

Therefore, for purposes of 

demonstrating continuous compliance 

with the underlying MACT standard, we 

are proposing at 40 CFR 63.1435(a), by 

reference to 40 CFR 63.104(a)(4)(v), to 

remove the exemptions for once-through 

heat exchange systems meeting certain 

NPDES permit conditions at 40 CFR 

63.104(a)(3) and (4) and instead to 

require that facilities comply with the 

requirements of 40 CFR 63.104(b) and 

63.104(c). 

Our technology review identified one 

development in LDAR practices and 

processes for heat exchange systems 

(i.e., broader than our review of heat 

exchange systems in EtO service 

discussed in section IV.B.2.c of this 

preamble): the use of the Modified El 

Paso Method 37 to monitor for leaks. The 

Modified El Paso Method is included in 

the HON, MON, EMACT standards, the 

Petroleum Refinery Sector rule, and in 

the RACT/BACT/LAER clearinghouse 

database. TCEQ also requires the 

method for facilities complying with 

TCEQ’s highly reactive volatile organic 

compound (HRVOC) rule (i.e., 30 Texas 

Administrative Code Chapter 115, 

Subchapter H, Division 3). The 

Modified El Paso Method measures a 

larger number of compounds than the 

current methods required in the PEPO 

NESHAP and is more effective in 

identifying leaks. For LDAR programs 

applied to heat exchange systems, the 

compliance monitoring option, leak 

definition, and frequency of monitoring 

for leaks are all important 

considerations affecting emission 

reductions because they identify when 

there is a leak and when to take 

corrective actions to repair the leak. 

Therefore, we evaluated the Modified El 

Paso Method for use at PEPO facilities, 

including an assessment of appropriate 

leak definitions and monitoring 

frequencies. 

To identify an appropriate Modified 

El Paso Method leak definition for 

facilities subject to the PEPO NESHAP, 

we identified five rules (i.e., TCEQ 

HRVOC rule, the HON, the MON, the 

EMACT standards, and the Petroleum 

Refinery Sector rule) that incorporate 

this monitoring method and have leak 

definitions corresponding to the use of 

this methodology. We also reviewed 

data submitted in response to a CAA 

section 114 request for PEPO production 

facilities. The TCEQ HRVOC rule, the 

HON, the MON, EMACT standards, and 

the Petroleum Refinery Sector rule have 

leak definitions of total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas ranging from 3.1 

ppmv to 6.2 ppmv. In addition, sources 

subject to the HON, the MON, EMACT 

standards, or the Petroleum Refinery 

Sector rule must repair a leak no later 

than 45 days after first identifying the 

leak and cannot delay the repair of leaks 

for more than 30 days where, during 

subsequent monitoring, owners or 


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38We note that while there are 25 PEPO facilities, 

one PEPO facility is currently co-located with a 

HON facility. This facility is a small business that 

only receives and treats wastewater. Therefore, we 

do not expect this facility to have heat exchange 

systems on site. 

39We note that each of the HON citations 

mentioned in this paragraph of this preamble are 

also applicable to PEPO facilities pursuant to 40 

CFR 63.1435. For these HON citations to properly 

apply to PEPO facilities, we are proposing 

substitution rule text at 40 CFR 63.1435(f) and (g). 

operators find a total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas of 62 ppmv or 

higher. Taking into account the range of 

actionable leak definitions in use by 

other rules that require use of the 

Modified El Paso Method currently (i.e., 

3.1 ppmv to 6.2 ppmv of total strippable 

hydrocarbon (as methane) in the 

stripping gas), we chose to evaluate a 

leak definition at the upper end of 

identified actionable leak definitions in 

our analysis. Thus, we evaluated the 

Modified El Paso Method leak definition 

of 6.2 ppmv of total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas for both new and 

existing heat exchange systems, along 

with not allowing delay of repair of 

leaks for more than 30 days where, 

during subsequent monitoring, a total 

strippable hydrocarbon concentration 

(as methane) in the stripping gas of 62 

ppmv or higher is found. 

We also considered more stringent 

monitoring frequencies. Both the 

Petroleum Refinery Sector rule, which 

includes monthly monitoring for 

existing sources under certain 

circumstances, and the TCEQ HRVOC 

rule, which includes continuous 

monitoring provisions for existing and 

new sources, have more stringent 

monitoring frequencies. However, the 

petroleum refinery rule analysis found 

the incremental HAP cost effectiveness 

to change from quarterly to monthly 

monitoring and monthly to continuous 

monitoring (at the same leak definition) 

of refinery heat exchange systems to be 

$40,000/ton and $500,000/ton, 

respectively. We conclude that these 

costs are not reasonable for PEPO 

facilities. Thus, we chose to evaluate 

quarterly monitoring for existing and 

new heat exchange systems (i.e., the 

base monitoring frequency currently in 

the rule). We also evaluated monthly 

monitoring to confirm the anticipated 

higher incremental HAP cost 

effectiveness. 

Based on this technology review, we 

identified the following control options 

for heat exchange systems as a 

development in practice that can be 

implemented at a reasonable cost: (1) 

quarterly monitoring for existing and 

new heat exchange systems (after an 

initial 6 months of monthly monitoring) 

with the Modified El Paso Method and 

a leak definition of 6.2 ppmv of total 

strippable hydrocarbon concentration 

(as methane) in the stripping gas, and 

(2) same as Control Option 1, except 

monthly monitoring with the Modified 

El Paso Method instead of quarterly 

monitoring. 

We then estimated the impacts of 

these control options assuming 24 PEPO 

facilities 38 would be affected by 

requiring the use of the Modified El 

Paso Method. As part of our analysis, 

we assumed owners or operators 

conducting monitoring for three or more 

heat exchange systems would elect to 

purchase a stripping column and FID 

analyzer and perform in-house Modified 

El Paso monitoring because the total 

annualized costs for in-house Modified 

El Paso monitoring are less than the 

costs for contracted services. In 

addition, we assumed that owners or 

operators could repair leaks by plugging 

a specific heat exchanger tube, and if a 

heat exchanger is leaking to the extent 

that it needs to be replaced, then it is 

effectively at the end of its useful life. 

Therefore, we determined that the cost 

of replacing a heat exchanger is an 

operational cost that would be incurred 

by the facility as a result of routine 

maintenance and equipment 

replacement, and it is not attributable to 

the control option. 

Table 6 of this preamble presents the 

nationwide impacts for requiring 

owners or operators at PEPO facilities to 

use the Modified El Paso Method 

quarterly or monthly (Control Options 1 

and 2), and repair leaks of total 

strippable hydrocarbon concentration 

(as methane) in the stripping gas of 6.2 

ppmv or greater. See the document 

titled Clean Air Act Section 112(d)(6) 

Technology Review for Heat Exchange 

Systems Located in the PEPO 

Production Source Category that are 

Associated with Processes Subject to the 

PEPO NESHAP, which is available in 

the docket for this rulemaking, for 

details on the assumptions and 

methodologies used in this analysis. 

TABLE 6—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTIONS CONSIDERED FOR HEAT

EXCHANGE SYSTEMS AT PEPO FACILITIES

Control option 

Total 

capital 

investment 

($) 

Total 

annualized 

costs w/o 

credits 

($/yr) 

Total 

annualized 

costs 

w/credits 

($/yr) 

Total HAP 

emission 

reductions 

(tpy) 

Average 

HAP costeffectiveness 

w/credits 

($/ton) 

Average 

HAP costeffectiveness 

w/o credits 

($/ton) 

Average 

incremental 

HAP costeffectiveness 

w/credits 

($/ton) 

1 ................................................................................................ 54,700 30,700 10,400 17.4 600 1,800 ....................

2 ................................................................................................ 492,400 82,200 61,200 18.0 3,400 4,500 80,400 

Based on the costs and emission 

reductions for the identified control 

options, we are proposing Control 

Option 1 to revise the PEPO NESHAP 

for heat exchange systems pursuant to 

CAA section 112(d)(6). We are not 

proposing Control Option 2 because it is 

not cost-effective given the high 

incremental total HAP cost effectiveness 

(i.e., $80,400/ton HAP) from Control 

Option 1. We are proposing Control 

Option 1 at 40 CFR 63.1435, by 

reference to the HON (40 CFR 

63.104(g)(4)),39 to specify quarterly 

monitoring for existing and new heat 

exchange systems (after an initial 6 

months of monthly monitoring) using 

the Modified El Paso Method and a leak 

definition of 6.2 ppmv of total 

strippable hydrocarbon concentration 

(as methane) in the stripping gas. We are 

proposing to require owners and 

operators to repair the leak to reduce the 

concentration or mass emissions rate to 

below the leak action level as soon as 

practicable, but no later than 45 days 

after identifying the leak. We are also 

proposing, by reference to 40 CFR 

63.104(j)(3), a delay of repair action 

level of total strippable hydrocarbon 

concentration (as methane) in the 

stripping gas of 62 ppmv, that if 

exceeded during leak monitoring, would 

require immediate repair (i.e., the leak 

found cannot be put on delay of repair 

and would be required to be repaired 

within 30 days of the monitoring event). 

This would apply to both monitoring 

heat exchange systems and individual 


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40 In May 2021, EPA Region 4 received a request 

from Eastman Chemical Company to perform an 

alternative method instead of the Modified El Paso 

Method to monitor for leaks in Eastman’s Tennessee 

Operations heat exchange systems, which primarily 

have cooling water containing soluble HAP with a 

high boiling point. Eastman specifically identified 

two HAP (1,4-dioxane and methanol), which do not 

readily strip out of water using the Modified El Paso 

Method. Eastman’s application for alternative 

monitoring included experimental data showing 

that the Modified El Paso Method would likely not 

identify a leak of these HAP in heat exchange 

system cooling water. Eastman conducted Modified 

El Paso Method monitoring under controlled 

scenarios to determine how much methanol and 

1,4-dioxane would be detected. The scenarios 

included solutions of water and either methanol or 

1,4-dioxane at concentrations of 1 ppmw, 20 ppmw, 

and 100 ppmw (as measured using water sampling 

methods allowed previously in the MON). The 

Modified El Paso Method did not detect any 

methanol or 1,4-dioxane from the 1 ppmw and 20 

ppmw solutions (i.e., methanol and 1,4-dioxane did 

not strip out of the water in detectable amounts). 

The Modified El Paso Method detected very little 

HAP from the 100-ppmw solutions, with a 

maximum of only 0.17 percent of the 1,4-dioxane 

stripping out and being detected. 

41Require all openings in an IFR (except those for 

automatic bleeder vents (vacuum breaker vents), 

rim space vents, leg sleeves, and deck drains) be 

equipped with a deck cover; and require the deck 

cover to be equipped with a gasket between the 

cover and the deck. 

heat exchangers by replacing the use of 

any 40 CFR part 136 water sampling 

method with the Modified El Paso 

Method and removing the option that 

allows for use of a surrogate indicator of 

leaks. We are also proposing, by 

reference to 40 CFR 63.104(h) and (i), 

that repair include re-monitoring at the 

monitoring location where a leak is 

identified to ensure that any leaks found 

are fixed. We are proposing that none of 

these requirements would apply to heat 

exchange systems that have a maximum 

cooling water flow rate of 10 gallons per 

minute or less because owners and 

operators of smaller heat exchange 

systems would be disproportionately 

affected and forced to repair leaks with 

a much lower potential HAP emissions 

rate than owners and operators of heat 

exchange systems with larger 

recirculation rate systems. Finally, we 

are proposing by reference to 40 CFR 

63.104(l) that the leak monitoring 

requirements for heat exchange systems 

at 40 CFR 63.104(b) may be used in 

limited instances, instead of using the 

Modified El Paso Method, to monitor for 

leaks. We continue to maintain that the 

Modified El Paso Method is the 

preferred method to monitor for leaks in 

heat exchange systems and we are 

proposing that the requirements of 40 

CFR 63.104(b) may only be used if 99 

percent by weight or more of all the 

organic compounds that could 

potentially leak into the cooling water 

have a Henry’s Law Constant less than 

5.0E–6 atmospheres per mole per cubic 

meter (atm-m3/mol) at 25° Celsius. As 

noted in the proposal for the HON 

amendments (88 FR 25080), we selected 

this threshold based on a review of 

Henry’s Law Constants for the HAP 

listed in table 4 to 40 CFR part 63, 

subpart F, as well as the water-soluble 

organic compounds listed in a recent 

alternative monitoring request from a 

MON facility.40 Henry’s Law Constants 

are available from the EPA at https:// 

comptox.epa.gov/dashboard/. Examples 

of HAP that have a Henry’s Law 

Constant less than 5.0E–6 atm-m3/mol 

at 25° Celsius are: aniline; 2- 

chloroacetophenone; diethylene glycol 

diethyl ether; diethylene glycol 

dimethyl ether; dimethyl sulfate; 2,4- 

dinitrotoluene; 1,4-dioxane; ethylene 

glycol monoethyl ether acetate; ethylene 

glycol monomethyl ether acetate; 

methanol; and toluidine. Many of these 

HAP also have very high boiling points, 

with most above 300 °F, which means 

they will generally stay in the cooling 

water and not be emitted to the 

atmosphere. We solicit comments on the 

proposed requirements related to heat 

exchange systems. 

2. Standards for Storage Vessels 

Storage vessels are used to store 

liquid and gaseous feedstocks for use in 

a process, as well as to store liquid and 

gaseous products from a process. Most 

PEPO storage vessels are designed for 

operation at atmospheric or near 

atmospheric pressures; pressure vessels 

are used to store compressed gases and 

liquefied gases. Atmospheric storage 

vessels are typically cylindrical with a 

vertical orientation, and they are 

constructed with either a fixed roof or 

a floating roof. Some, generally small, 

atmospheric storage vessels are oriented 

horizontally. Pressure vessels are either 

spherical or horizontal cylinders. 

The HON storage vessel standards 

that PEPO affected sources are currently 

subject to, by reference to NESHAP 

subpart G at 40 CFR 63.119 through 

63.123, require that owners and 

operators control emissions from storage 

vessels with capacities between 75 m3

(inclusive) and 151 m3 and a MTVP 

greater than or equal to 13.1 kPa, and 

storage vessels with capacities greater 

than or equal to 151 m3 and a MTVP 

greater than or equal to 5.2 kPa. Storage 

vessels meeting these capacity and size 

criteria capacity are considered Group 1 

storage vessels. Generally, the standards 

in the PEPO NESHAP for storage vessels 

refer to the provisions in the HON. As 

such, owners and operators of PEPO 

Group 1 storage vessels storing a liquid 

with a MTVP of total organic HAP less 

than 76.6 kPa must reduce emissions of 

organic HAP by 95 percent (or 90 

percent if the storage vessel was 

installed on or before September 4, 

1997) using a closed vent system and 

control device, or reduce organic HAP 

emissions either by utilizing an IFR or 

EFR, routing the emissions to a process 

or a fuel gas system, or through vapor 

balancing. Owners and operators of 

PEPO Group 1 storage vessels 

containing a liquid with a MTVP of total 

organic HAP greater than or equal to 

76.6 kPa must reduce emissions of 

organic HAP by 95 percent (or 90 

percent if the storage vessel was 

installed on or before September 4, 

1997) utilizing a closed vent system and 

control device, or reduce organic HAP 

emissions by routing the emissions to a 

process or a fuel gas system, or using 

vapor balancing. In general, PEPO 

storage vessels that do not meet the 

MTVP and capacity thresholds 

described above are considered Group 2 

storage vessels and owners or operators 

are not required to apply any additional 

emission controls provided they remain 

under Group 1 thresholds; however, 

Group 2 storage vessels are subject to 

certain monitoring, reporting, and 

recordkeeping requirements to ensure 

that they were correctly determined to 

be Group 2 storage vessels and that they 

remain in Group 2. 

As part of our technology review for 

PEPO storage vessels (i.e., broader than 

our review of storage vessels in EtO 

service discussed in section IV.B.2.a of 

this preamble), we identified the 

following emission reduction options: 

(1) revising the capacity and MTVP 

thresholds of the PEPO NESHAP to 

reflect the HON existing source 

threshold which requires existing 

storage vessels between 38 m3

(inclusive) and 151 m3 with an MTVP 

greater than or equal to 6.9 kPa to 

reduce emissions of organic HAP by 95 

percent utilizing a closed vent system 

and control device, or reduce organic 

HAP emissions either by utilizing an 

IFR, an EFR, by routing the emissions to 

a process or a fuel gas system, or using 

vapor balancing; (2) same as Control 

Option 1 plus requiring upgraded deck 

fittings 41 and controls for guidepoles for 

all storage vessels equipped with an IFR 

as already required in 40 CR 63, subpart 

WW (NESHAP for Storage Vessels— 

Control Level (2); and (3) in addition to 

requirements specified in Control 

Options 1 and 2, requiring the 

conversion of EFRs to IFRs through use 

of geodesic domes and upgrades to deck 

fittings and guidepoles. 

We identified Control Option 1 as a 

technologically feasible development in 

practices, processes, and control 


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technologies for storage vessels used at 

PEPO facilities because it reflects 

requirements for similar storage vessels 

that are located at chemical 

manufacturing facilities subject to the 

HON. Control Option 2 is an 

improvement in practices because these 

upgraded deck fittings and guidepole 

controls have been required by other 

regulatory agencies and other EPA 

regulatory action (e.g., Petroleum 

Refinery Sector rulemaking) since 

promulgation of the PEPO NESHAP. 

Finally, we consider Control Option 3 to 

be a development in control technology 

because we found that some storage 

vessels with EFRs have installed 

geodesic domes since promulgation of 

the PEPO NESHAP. 

We used information about storage 

vessel capacity, design, and stored 

materials that industry provided to the 

EPA in response to our CAA section 114 

request (see section II.C of this 

preamble) to evaluate the impacts of all 

three of the options presented. We did 

not identify any PEPO storage vessels 

from our CAA section 114 request that 

would be impacted by Control Option 1. 

Given that materials used in PEPO 

production have very low vapor 

pressures, the majority of PEPO Group 

2 storage vessels do not meet the vapor 

pressure portion of the revised Control 

Option 1 applicability. Furthermore, our 

CAA section 114 request data shows 

zero Group 2 storage vessels fitted with 

an IFR or EFR, meaning no additional 

storage vessels would be affected by 

Control Option 2 or 3. To verify these 

findings, we conducted an air permit 

review alongside analysis of our CAA 

section 114 request data to identify any 

additional Group 2 storage vessels at 

PEPO facilities outside of the CAA 

section 114 respondents. We reviewed 

title V permits for the remaining 16 

facilities subject to the PEPO NESHAP 

and determined that no additional 

Group 2 storage vessels would be 

affected by any of the aforementioned 

options. Based on these analyses, we 

estimate that applying any of the 

aforementioned options to the PEPO 

NESHAP would not result in cost 

impacts or emission reductions for 

PEPO facilities. See the document titled 

Clean Air Act Section 112(d)(6) 

Technology Review for Storage Vessels 

Located in the PEPO Production Source 

Category that are Associated with 

Processes Subject to the PEPO NESHAP, 

which is available in the docket for this 

rulemaking, for details on the 

assumptions and methodologies used in 

this analysis. 

We are proposing storage vessel 

Control Option 2 (which includes 

Control Option 1), pursuant to CAA 

section 112(d)(6), to revise the Group 1 

storage capacity criterion for PEPO 

storage vessels at new and existing 

sources from between 75 m3 (inclusive) 

and 151 m3 to between 38 m3 (inclusive) 

and 151 m3 (see proposed table 3 to 40 

CFR part 63, subpart PPP), and to 

require upgraded deck fittings and 

controls for guidepoles for all storage 

vessels equipped with an IFR as already 

required in 40 CFR part 63, subpart WW 

(see proposed 40 CFR 63.1432 which 

refers to the HON including 40 CFR 

63.119(b)(5)(ix), (x), (xi), and (xii)). We 

note that the EPA recently finalized 

these same options for the HON, finding 

them to be cost effective for HON 

storage vessels (see 89 FR 42932, May 

16, 2024). Given that the PEPO NESHAP 

directly references the HON storage 

vessel provisions (40 CFR part 63, 

subpart G), we believe it is reasonable 

for PEPO facilities to comply with these 

same final HON provisions. Although 

we did not find any PEPO storage 

vessels that would be affected by these 

proposed provisions, we believe it 

would be unnecessarily cumbersome to 

exclude these vessels by caveat in the 

storage vessel provisions of the PEPO 

NESHAP. Also, given that the EPA 

determined that Control Option 3 was 

not cost effective and did not propose 

this option for HON storage vessels, we 

are not proposing to revise the PEPO 

NESHAP to reflect the requirements of 

Control Option 3 pursuant to CAA 

section 112(d)(6). Materials used in 

PEPO production have very low vapor 

pressures so we anticipate that the cost 

effectiveness of Control Option 3 would 

be worse for PEPO storage vessels. We 

also anticipate that EFR storage vessels 

would not be considered for any new 

PEPO affected sources given we did not 

identify any existing EFR storage vessels 

subject to the PEPO NESHAP. We solicit 

comments on the proposed revisions for 

storage vessels. 

3. Standards for Process Vents 

A process vent is a gas stream that is 

discharged during the operation of a 

particular unit operation (e.g., 

separation processes, purification 

processes, mixing processes, reaction 

processes). The gas stream(s) may be 

routed to other unit operations for 

additional processing (e.g., a gas stream 

from a reactor that is routed to a 

distillation column for separation of 

products), sent to one or more recovery 

devices, sent to a process vent header 

collection system (e.g., blowdown 

system) and APCD (e.g., flare, thermal 

oxidizer, carbon adsorber), and/or 

vented to the atmosphere. Process vents 

may be generated from continuous and/ 

or batch operations, as well as from 

other intermittent types of operations 

(e.g., maintenance operations). If 

process vents are required to be 

controlled prior to discharge to the 

atmosphere to meet an applicable 

emissions standard, then they are 

typically collected and routed to an 

APCD through a closed vent system. 

The PEPO NESHAP specifies process 

vent control provisions for affected 

sources depending on the type of PEPO 

production process used: (1) 

polymerization of epoxides, or (2) 

polymerization of THF. Typically, PEPO 

processes that use epoxide reactants are 

batch processes, although some epoxide 

reactions are continuous, while 

production processes that use THF are 

continuous. For the PEPO production 

processes that use epoxides as a 

reactant, the NESHAP groups the 

process vent control provisions based 

on the function of the organic HAP in 

the production process and the resulting 

HAP emissions. Table 7 of this preamble 

shows the process vent emission 

standards of the PEPO NESHAP for each 

of these groups for existing and new 

affected sources. 

TABLE 7—PROCESS VENT EMISSION STANDARDS IN THE PEPO NESHAP FOR AFFECTED SOURCES THAT PRODUCE

PEPO USING EPOXIDE REACTANTS

Process vent 

group 

Process vent standards for existing 

affected sources 

Process vent standards for new 

affected sources 

Epoxides emissions ................... • 98-percent aggregate reduction of total epoxide emissions; 1

• flare total epoxide emissions; 

• maintain an outlet concentration of ≤20 ppmv of total 

epoxides or TOC; or 

• maintain ≤1.69 × 10¥2 kilograms of epoxide emissions per 

megagram of product made 

• 99.9 percent aggregate reduction of total epoxide emissions; 1

• maintain an outlet concentration ≤20 ppmv of total epoxides 

or TOC; or 

• maintain ≤4.43 × 10¥3 kilograms of epoxide emissions per 

megagram of product made. 


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TABLE 7—PROCESS VENT EMISSION STANDARDS IN THE PEPO NESHAP FOR AFFECTED SOURCES THAT PRODUCE

PEPO USING EPOXIDE REACTANTS—Continued 

Process vent 

group 

Process vent standards for existing 

affected sources 

Process vent standards for new 

affected sources 

Nonepoxide organic HAP emissions from making or modifying the product.

Group 1 combination of process vents from batch unit operations: 

• 90-percent aggregate emission reduction; or 

• flare emissions from all vents 

Same as existing affected sources. 

Group 1 process vents from continuous unit operations: 

• 98-percent aggregate emission reduction; or 

• flare emissions 

Nonepoxide organic HAP emissions from catalyst extraction.• 90-percent aggregate emission reduction; or 

• flare emissions from all vents 

Same as existing affected sources. 

1The PEPO NESHAP allows the use of ECO as a means of reducing emissions by the required percentage (98 or 99.9 percent) or complying with the productionbased limits (1.69 × 10¥2 or 4.43 × 10¥3). This pollution prevention technique reduces emissions by extending the time of reaction, thus leaving less unreacted 

epoxides to be emitted downstream. To demonstrate a percent efficiency, it is necessary to designate the basis, or the ‘‘uncontrolled’’ emissions, for assessing the 

percent reduction. The point where uncontrolled emissions are to be assessed, called the ‘‘onset’’ of the ECO, is defined in the PEPO NESHAP as the point when the 

epoxide concentration in the reactor liquid is equal to 25 percent of the concentration of epoxide in the liquid at the end of the epoxide feed. 

For the control requirements for 

nonepoxide organic HAP from making 

or modifying the product specified in 

table 7 of this preamble, owners or 

operators must determine whether the 

process vent is a Group 1 or Group 2 

process vent. The PEPO NESHAP 

defines a ‘‘Group 1 combination of batch 

process vents’’ as a collection of process 

vents in a PMPU from batch unit 

operations that are associated with the 

use of a nonepoxide organic HAP to 

make or modify the product that has: (1) 

annual nonepoxide organic HAP 

emissions of 11,800 kg/yr 

(approximately 26,014 lb/yr) or greater, 

and (2) a cutoff flow rate that is greater 

than or equal to the annual average flow 

rate. The PEPO NESHAP defines a 

‘‘Group 1 continuous process vent’’ as a 

process vent from a continuous unit 

operation that is associated with the use 

of a nonepoxide organic HAP to make 

or modify the product and that has: (1) 

a flow rate greater than or equal to 0.005 

standard cubic meters per minute 

(scmm), (2) a total organic HAP 

concentration greater than or equal to 50 

ppmv, and (3) a total resource 

effectiveness (TRE) index value less 

than or equal to 1.0. As discussed 

further below, the TRE index value is a 

measure of the supplemental total 

resource requirement per unit VOC (or 

HAP) reduction. The PEPO NESHAP 

defines a Group 2 process vent as a 

process vent that is associated with the 

use of a nonepoxide organic HAP to 

make or modify the product that is not 

classified as either a Group 1 

combination of batch process vents or a 

Group 1 continuous process vent. In 

general, Group 2 process vents are not 

required to apply any additional 

emission controls; however, they are 

subject to certain monitoring, reporting, 

and recordkeeping requirements to 

ensure that they were correctly 

determined to be Group 2 and that they 

remain Group 2. 

The HON process vent standards that 

certain PEPO affected sources (i.e., those 

that produce PEPO using THF) are 

currently subject to require a Group 1/ 

Group 2 determination: 

• A Group 1 process vent associated 

with a PMPU using THF is a process 

vent for which the vent stream flow rate 

is greater than or equal to 0.005 scmm, 

the total organic HAP concentration is 

greater than or equal to 50 ppmv, and 

the TRE index value is less than or 

equal to 1.0. Owners or operators of 

Group 1 process vents at PEPO 

processes that use THF are required to 

either: reduce emissions of organic HAP 

using a flare meeting 40 CFR 63.11(b); 

reduce emissions of total organic HAP 

or TOC by 98 weight percent or to an 

exit concentration of 20 ppmv, 

whichever is less stringent; or achieve 

and maintain a TRE index value greater 

than 1.0. 

• A Group 2 process vent associated 

with a PMPU using THF is process vent 

for which the vent stream flow rate is 

less than 0.005 scmm, the total organic 

HAP concentration is less than 50 

ppmv, or the TRE index value is greater 

than 1.0. 

As previously mentioned in this 

section of the preamble, the PEPO 

NESHAP contains a TRE index value 

threshold of 1.0 as part of the criteria 

used to determine whether owners or 

operators must control continuous 

process vents associated with 

nonepoxide organic HAP from making 

or modifying product and process vents 

associated with affected sources that 

produce PEPO using THF. In both of 

these process vent scenarios, the PEPO 

NESHAP requires owners or operators 

to calculate the TRE index using the 

procedures in the HON. The TRE index 

value accounts for all the resources 

which are expected to be used in VOC 

(or HAP) control by thermal oxidation 

and provides a dimensionless measure 

of resource burden based on cost 

effectiveness. Resources include 

supplemental natural gas, labor, and 

electricity. Additionally, if the off-gas 

contains halogenated compounds, 

resources will also include caustic and 

scrubbing and quench makeup water. 

For the PEPO NESHAP, owners or 

operators derive the TRE index value 

from the cost effectiveness associated 

with HAP control by a flare or thermal 

oxidation, and is a function of vent 

stream flowrate, vent stream net heating 

value, hourly emissions, and a set of 

coefficients. The EPA first introduced 

the TRE index value in an Agency 

document titled: Guideline Series for 

Control of Volatile Organic Compound 

(VOC) Emissions from Air Oxidation 

Processes in Synthetic Organic 

Chemical Manufacturing Industry 

(SOCMI) (see EPA–450/3–84–015, 

December 1984). The EPA incorporated 

the TRE concept into the original HON 

(see 59 FR 19468, April 22, 1994) and 

the original PEPO NESHAP rulemaking 

(see 64 FR 29420, June 1, 1999). The 

PEPO NESHAP uses the TRE index 

value as an alternative mode of 

compliance for process vent regulations. 

The TRE index value can also trigger 

monitoring, recordkeeping, and 

reporting requirements. For additional 

details regarding the TRE index value 

(including the equation and coefficients 

used to calculate the TRE index value 

for the PEPO NESHAP), see the 

document titled Clean Air Act Section 

112(d)(6) Technology Review for Batch 

and Continuous Process Vents in the 

PEPO Production Source Category that 

are Associated with Processes Subject to 

the PEPO NESHAP, which is available 

in the docket for this rulemaking. 

Our technology review for PEPO 

process vents (i.e., broader than our 

review of process vents in EtO service 

discussed in section IV.B.2.a of this 

preamble) did not identify any control 

options associated with: (1) epoxide 

(i.e., EtO, propylene oxide, and 


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42The EPA recently removed the TRE index value 

from the HON (see 89 FR 42932, May 16, 2024). The 

EMACT standards never used the TRE index value. 

43None of the nine PEPO facilities that received 

our CAA section 114 request reported having any 

Group 2 continuous process vents associated with 

processes subject to the PEPO NESHAP; and only 

one of these facilities designated eight of their 

process vents as Group 1 continuous process vents 

subject to the PEPO NESHAP. We note that 

facilities can voluntarily designate a Group 2 

process vent as a Group 1 process vent and control 

it according to Group 1 requirements. In these 

instances, the owner or operator is not required to 

keep calculations supporting a TRE index value. 

Therefore, it is possible that some of these Group 

1 process vents are Group 2 process vents 

designated as Group 1 process vents. 

44See Illinois Title 35: Subtitle B: Chapter I: 

Subchapter C: Parts 218 and 219 (i.e., Organic 

Material Emission Standards And Limitations For 

The Chicago Area Subpart V: Batch Operations And 

Air Oxidation Processes; and Organic Material 

Emission Standards And Limitations For The Metro 

East Area Subpart V: Batch Operations And Air 

Oxidation Processes). However, it is unlikely to be 

applicable to process vents in the PEPO Production 

source category because it applies specifically to air 

oxidation processes, which are not typically used 

in PEPO production. 

epichlorohydrin) emissions resulting 

from the use of these chemicals as 

reactants, or (2) emissions of 

nonepoxide organic HAP resulting from 

their use in catalyst extraction. 

However, we identified the following 

emission reduction options as part of 

our technology review for continuous 

process vents associated with 

nonepoxide organic HAP from making 

or modifying product and process vents 

associated with affected sources that 

produce PEPO using THF: (1) remove 

the TRE concept in its entirety, remove 

the 50-ppmv and 0.005-scmm Group 1 

process vent thresholds, and redefine a 

Group 1 process vent as any process 

vent that emits greater than or equal to 

1.0 pound per hour (lb/hr) of total 

organic HAP; (2) the same requirements 

specified in Control Option 1, but 

redefine a Group 1 process vent as any 

process vent that emits greater than or 

equal to 0.10 lb/hr of total organic HAP; 

and (3) retain the TRE concept and the 

50-ppmv and 0.005-scmm Group 1 

process vent thresholds, but increase the 

TRE index value threshold from 1.0 to 

5.0. 

We identified Control Options 1 and 

2 as developments in practices, 

processes, and control technologies for 

multiple reasons. First, we identified at 

least two chemical manufacturing 

NESHAP (i.e., EMACT standards and 

the HON) that do not use the TRE index 

value as criteria for determining 

whether a process vent should be 

controlled.42 Second, based on the 

responses to our CAA section 114 

request (see section II.C of this 

preamble), we observed that some 

facilities are voluntarily controlling 

continuous process vents that are not 

required to be controlled per the results 

of the TRE index value calculation. Of 

the 13 HON facilities that received the 

CAA section 114 request, at least three 

facilities confirmed they were 

voluntarily controlling some of their 

Group 2 process vents. We expect PEPO 

facilities will also voluntarily control 

some of their Group 2 process vents, 

because facilities responded in the CAA 

section 114 request that, pursuant to 40 

CFR 63.113(h), many of their process 

vents are voluntarily designated as 

Group 1 process vents ‘‘so that TRE 

calculations are not required.’’ In other 

words, some facilities are likely electing 

to control certain process vents that 

have TRE index values greater than 

1.0.43 Third, based on the responses to 

our CAA section 114 request, we 

observed that facilities are routing 

multiple continuous process vents to a 

single APCD. This practice is significant 

because the current use of the TRE 

index value is only based on controlling 

a single process vent with a single 

APCD, which is an unrealistic scenario 

when compared to how chemical 

manufacturing facilities actually control 

their process vents. We believe that it is 

much more likely that a facility routes 

numerous process vents to the same 

APCD. Finally, we concluded that the 

TRE index is difficult to enforce because 

it is largely a theoretical 

characterization tool that incorporates 

numerous input values provided by 

owners or operators, and verifying the 

inputs without site-specific process 

knowledge can be problematic. We 

based our conclusion on a response to 

the CAA section 114 request received 

from one facility that provided over 300 

pages of modeled runs that the facility 

used to help determine certain 

characteristics of their continuous 

process vents for use as inputs to TRE 

index value calculations (the facility 

had originally included these modeled 

runs with their Notification of 

Compliance Status report for the HON). 

Our review of this information 

identified numerous instances where 

the facility noted difficulties or 

uncertainties associated with modeling 

the process vent characteristics. 

We identified Control Option 3 as a 

development in practices, processes, 

and control technologies because we 

determined that another chemical 

manufacturing NESHAP (i.e., the MON) 

contains a TRE index value threshold 

criteria (i.e., less than or equal to 1.9) 

that is more stringent than the PEPO 

NESHAP TRE index value threshold 

criteria (i.e., less than or equal to 1.0). 

Additionally, we identified one State 

regulatory agency rule that uses a more 

stringent TRE index value threshold 

than the value specified in the PEPO 

NESHAP.44

To evaluate impacts of the three 

control options presented above, we 

used information for approximately 50 

continuous process vents designated as 

Group 2 that was provided by nine of 

the 13 HON facilities that received the 

CAA section 114 request. We 

determined it was reasonable to use the 

CAA section 114 response data for HON 

Group 2 process vents to extrapolate 

impacts for certain continuous Group 2 

process vents subject to the PEPO 

NESHAP given that PMPU sources 

subject to the PEPO NESHAP are similar 

to CMPU (chemical manufacturing 

process unit) sources that are subject to 

the HON. Additionally, there are 15 

PEPO facilities co-located with HON 

facilities; therefore, we believe it is 

reasonable to assume that developments 

in practices, processes, and control 

technologies would be implemented 

across the entire facility, given the 

similarities between HON and PEPO 

process units. We also reviewed several 

air emissions permits issued by State 

regulatory agencies to validate our 

assumptions and estimates of the 

number of Group 2 process vents 

located at PEPO facilities. Although we 

were unable to determine the exact 

number of Group 2 process vents (both 

continuous and batch) that are located 

at each PEPO facility, we believe that, 

based on our air permit review, our 

Group 2 process vent estimates are 

reasonable. It is evident from our air 

permit review that some PEPO facilities 

have between one and six Group 2 

process vents. 

We estimated that process vent 

Control Option 1 would impact four 

PEPO facilities; one facility would need 

to install a thermal oxidizer and three 

facilities would either use existing 

controls or are already voluntarily 

controlling their Group 2 process vents. 

We estimated that process vent Control 

Option 2 would impact eight PEPO 

facilities; five facilities would need to 

install a thermal oxidizer and three 

facilities would either use existing 

controls or are already voluntarily 

controlling their Group 2 process vents. 

For process vent Control Option 3, we 

estimated that four PEPO facilities 

would be impacted by this option with 

one PEPO facility needing to install a 

thermal oxidizer and three facilities 

using either existing controls or are 

already voluntarily controlling their 

Group 2 process vents (i.e., the same 

impacts as estimated for process vent 


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45EPA, 2002. EPA Control Cost Manual, Sixth 

Edition. January 2002. Publication Number EPA/ 

452/B–02–001. 

46See 74 FR 56008, October 29, 2009. 

Control Option 1). We then used 

information about the composition of 

process vent streams, net heating value, 

and volumetric and mass flow rate that 

industry provided to the EPA in 

response to the CAA section 114 request 

for HON Group 2 process vents to 

estimate the total capital investment and 

total annual cost of: (1) installing 

thermal oxidizers for reducing HAP 

emissions from certain PEPO Group 2 

process vents, or (2) installing ductwork 

and a blower to route certain PEPO 

Group 2 process vents to an existing 

control device. For facilities that would 

need to install a thermal oxidizer, we 

used a total capital investment of 

$1,000,000 provided by commenters in 

the HON rulemaking (see 89 FR 42932, 

May 16, 2024). For total annual cost, we 

used the value the Agency determined 

for the HON rulemaking ($377,000 after 

adjusting for a higher interest rate and 

year 2022 dollars) for installing a new 

recuperative thermal oxidizer with 70- 

percent energy recovery following the 

procedures contained in the EPA 

Control Cost Manual.45 For facilities 

that would not need to install a thermal 

oxidizer and would instead route Group 

2 process vent emissions to an existing 

control device at the facility, we also 

estimated the average total capital 

investment and total annual cost values 

and emission reductions to install 

ductwork and a blower using the EPA 

Control Cost Manual. 

Table 8 of this preamble presents the 

nationwide impacts for the three 

options considered for continuous 

process vents associated with 

nonepoxide organic HAP (from making 

or modifying product) and process vents 

associated with affected sources that 

produce PEPO using THF. We 

determined that Control Option 1 is cost 

effective; therefore, we are proposing, 

pursuant to CAA section 112(d)(6), to 

remove the TRE concept in its entirety 

from the PEPO NESHAP (see proposed 

40 CFR 63.1425(c)(4) and (f)(7), 

63.1428(h) and (i), 63.1429(b)(2), and 

63.1430(e)(2), (f)(2) through (f)(5), and 

(j)). We are also proposing, pursuant to 

CAA section 112(d)(6), to remove the 

50-ppmv and 0.005-scmm thresholds 

from the Group 1 definition for 

continuous process vents at 40 CFR 

63.1423(b) associated with nonepoxide 

organic HAP and the Group 1 process 

vent applicability associated with a 

PMPU using THF, and instead require 

owners and operators of these process 

vents that emit greater than or equal to 

1.0 lb/hr of total organic HAP to meet 

the current control standards in the 

PEPO NESHAP. We are also proposing 

to revise 40 CFR 63.1430(g)(3) to align 

to the proposed 1.0 lb/hr threshold. In 

this action, we are not proposing to 

revise the PEPO NESHAP to reflect the 

requirements of process vent Control 

Options 2 and 3 pursuant to CAA 

section 112(d)(6). We determined that 

process vent Control Option 2 is not 

cost effective, and while we believe 

Control Option 3 is cost effective, it 

would require retaining the TRE 

concept in the rule which, for the 

reasons explained above, we believe is 

not desirable. We solicit comments on 

the proposed revisions to the process 

vent requirements for the PEPO 

NESHAP. 

TABLE 8—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTIONS CONSIDERED FOR CERTAIN

PROCESS VENTS 1 AT PEPO FACILITIES

Control option 

Total capital 

investment 

($) 

Total 

annualized 

costs 

($/yr) 

VOC 

emission 

reductions 

(tpy) 

HAP 

emission 

reductions 

(tpy) 

HAP costeffectiveness 

($/ton) 

1 ........................................................................................... 1,023,000 380,000 45 45 $8,500 

2 ........................................................................................... 3,040,000 1,135,000 34 21 53,700 

3 ........................................................................................... 1,023,000 380,000 37 37 10,200 

1For continuous process vents associated with nonepoxide organic HAP (from making or modifying product) and process vents associated 

with affected sources that produce PEPO using THF. 

As part of our technology review for 

the combination of batch process vents 

that are associated with the use of a 

nonepoxide organic HAP to make or 

modify the product, we identified the 

following emission reduction option: 

revise the PEPO NESHAP control 

threshold from 26,014 lb/yr to 10,000 

lb/yr and remove the associated flow 

rate applicability threshold. We 

identified this option as a development 

in practices, processes, and control 

technologies based on our comparison 

of the batch process vent requirements 

in the NESHAP for Chemical 

Manufacturing Area Sources (CMAS) to 

those specified in the PEPO NESHAP. 

Also, as part of a recent technology 

review, the EPA updated the Group I 

Polymers and Resins (P&R I) NESHAP 

(see 89 FR 42932, May 16, 2024) to 

reflect the applicability threshold used 

in the CMAS NESHAP. We note that the 

CMAS NESHAP regulates batch process 

vents from nine area source categories 

in the chemical manufacturing sector. 

Owners and operators of a CMAS CMPU 

with collective uncontrolled organic 

HAP emissions greater than or equal to 

10,000 lb/yr from all batch process vents 

associated with an affected CMPU must 

meet emission limits for organic HAP 

emissions. The CMAS NESHAP defines 

GACT for batch process vents as 85- 

percent control for existing batch 

process units (and 90-percent control for 

new units) that have uncontrolled 

organic HAP emissions equal to or 

greater than 10,000 lb/yr. As discussed 

in the CMAS NESHAP rulemaking,46

the EPA also used the applicability 

threshold of 10,000 lb/yr per batch 

process in the MON and this threshold 

indicates the size of a CMPU because 

the MON applies to major sources of 

HAP. The EPA used information from 

the baseline facility MON database and 

determined that costs to meet an 85- 

percent control requirement for existing 

CMAS CMPUs with uncontrolled 

organic HAP emissions equal to or 

greater than 10,000 lb/yr were 

reasonable ($8,700/ton). We note that 

the applicability threshold for 

uncontrolled organic HAP emissions of 

10,000 lb/yr used in the CMAS NESHAP 

is more stringent than the applicability 

threshold of 26,014 lb/yr specified in 

the PEPO NESHAP for nonepoxide 

organic HAP emitted from Group 1 

combination of batch process vents that 

are associated with the use of a 

nonepoxide organic HAP to make or 

modify the product. 

To evaluate impacts of the option 

presented for the combination of batch 


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47RTI, 2009. Revised Impacts Analysis for Batch 

Process Vents Chemical Manufacturing Area Source 

NESHAP. October 14, 2009. EPA Docket No. EPA– 

HQ–OAR–2008–0334–0075. 

48None of the nine PEPO facilities reported 

having any Group 2 combinations of batch process 

vents associated with processes subject to the PEPO 

NESHAP; however, five of the nine facilities 

reported having several Group 1 combinations of 

batch process vents subject to the PEPO NESHAP. 

We note that facilities can voluntarily designate a 

Group 2 process vent a Group 1 process vent and 

control it according to Group 1 requirements. In 

these instances, the owner or operator is not 

required to keep calculations supporting a TRE 

index value. Therefore, it is possible that some of 

these Group 1 process vents are Group 2 process 

vents designated as Group 1 process vents. 

process vents that are associated with 

the use of a nonepoxide organic HAP to 

make or modify the product, we used 

information from the batch process vent 

impacts analysis for the CMAS final 

rule.47 We selected the model plant for 

the 90-percent control option shown in 

table 3 of the CMAS NESHAP impacts 

analysis memorandum for sources 

subject to the PEPO NESHAP (instead of 

the 85-percent control option model 

plant shown in table 2 of the impacts 

analysis memorandum) to prevent 

backsliding of the current PEPO 

NESHAP requirements, which reflect 

MACT instead of the GACT standards of 

the CMAS NESHAP. We assumed that 

all facilities subject to the PEPO 

NESHAP, except for the nine that 

received our CAA section 114 request,48

have batch process vents that would 

require control under the option 

evaluated (i.e., under the option to 

change the Group 1 combination of 

batch process vents threshold to 10,000 

lb/yr). Additionally, we determined that 

one facility is a small business that is 

co-located with a HON facility, and 

already accounted for under the recent 

HON rulemaking (see 89 FR 42932, May 

16, 2024). As a result, we estimated 

impacts to the remaining 15 PEPO 

facilities. 

Table 9 of this preamble presents the 

nationwide impacts for the option 

considered for the combination of batch 

process vents that are associated with 

the use of a nonepoxide organic HAP to 

make or modify the product at PEPO 

facilities. We determined that this 

option is cost effective, and we are 

proposing, pursuant to CAA section 

112(d)(6), to remove the Group 1 

process vent thresholds of annual 

organic HAP emissions mass flow rate, 

cutoff flow rate, and the annual average 

batch vent flow rate from the definition 

of ‘‘Group 1 combination of batch 

process vents’’ specified in the PEPO 

NESHAP at 40 CFR 63.1423(b). We are 

also proposing to remove rule text 

associated with these process vent 

thresholds at 40 CFR 63.1428(c), (d), 

and (e). Instead, using the procedures 

specified in 40 CFR 63.1428(b), owners 

and operators of Group 1 combination of 

batch process vents that release a total 

of annual nonepoxide organic HAP 

emissions greater than or equal to 4,536 

kg/yr (10,000 lb/yr) would be required 

at 40 CFR 63.1425(c) to reduce 

emissions of nonepoxide organic HAP 

from these process vents using a flare 

meeting the proposed operating and 

monitoring requirements for flares (see 

section IV.D.1 of this preamble); or 

reduce emissions of nonepoxide organic 

HAP by 90 percent by weight. We are 

also proposing to revise 40 CFR 

63.1430(e)(1)(vii) to align to the 

proposed 4,536 kg/yr threshold. We 

solicit comments on the proposed 

revisions to the PEPO NESHAP for the 

combination of batch process vents that 

are associated with the use of a 

nonepoxide organic HAP to make or 

modify the product. 

TABLE 9—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF THE CONTROL OPTION CONSIDERED FOR THE

COMBINATION OF BATCH PROCESS VENTS (THAT ARE ASSOCIATED WITH THE USE OF A NONEPOXIDE ORGANIC HAP 

TO MAKE OR MODIFY THE PRODUCT) AT PEPO FACILITIES

Control option 

Total 

capital 

investment 

($) 

Total 

annualized 

costs 

($/yr) 

VOC 

emission 

reductions 

(tpy) 

Organic HAP 

emission 

reductions 

(tpy) 

Organic 

HAP costeffectiveness 

($/ton) 

1 ........................................................................................... 778,950 625,050 87.8 87.8 7,120 

For further details on our assumptions 

and methodologies used in these 

analyses, see the document titled Clean 

Air Act Section 112(d)(6) Technology 

Review for Batch and Continuous 

Process Vents in the PEPO Production 

Source Category that are Associated 

with Processes Subject to the PEPO 

NESHAP, which is available in the 

docket for this rulemaking. 

4. Standards for Wastewater 

As previously mentioned in this 

preamble, HAP are emitted from 

wastewater collection, storage, and 

treatment systems that are uncovered or 

open to the atmosphere through 

volatilization of organic compounds at 

the liquid surface. Emissions occur by 

diffusive or convective means, or both. 

Diffusion occurs when organic 

concentrations at the water surface are 

much higher than ambient 

concentrations. The organics volatilize, 

or diffuse into the air, to reach 

equilibrium between aqueous and vapor 

phases. Convection occurs when air 

flows over the water surface, which 

reduces the concentration at the 

boundary layer between the liquid and 

air, thereby sweeping organic vapors 

from the water surface into the air. The 

rate of volatilization is related directly 

to the speed of the air flow over the 

water surface. 

The PEPO NESHAP defines 

wastewater to mean water that contains 

either: (1) an annual average 

concentration of compounds specified 

in table 4 to 40 CFR part 63, subpart 

PPP, of at least 5 ppmw and has an 

annual average flow rate of 0.02 liters 

per minute (lpm) or greater, or (2) an 

annual average concentration of 

compounds specified in table 4 to 40 

CFR part 63, subpart PPP, of at least 

10,000 ppmw at any flow rate. The 

PEPO NESHAP definition of wastewater 

also includes water discarded from a 

PMPU that is part of an affected source 

(see 40 CFR 63.1420(a) for the definition 

of an affected source). Wastewater can 

be process wastewater or maintenance 

wastewater. For process and 

maintenance wastewaters, and certain 

liquid streams in open systems within a 

PMPU, the PEPO NESHAP defines 

Group 1 wastewater streams at existing 

and new sources as having a total 

annual average concentration of 

compounds specified in table 4 to 40 

CFR part 63, subpart PPP, that are also 

in table 9 to 40 CFR part 63, subpart G, 

greater than or equal to 10,000 ppmw at 

any flow rate, or greater than or equal 

to 1,000 ppmw with an annual average 

flow rate greater than or equal to 10 

liters per minute. The HON wastewater 

standards that PEPO sources are 

currently subject to directly reference 

(with differences specified in 40 CFR 

63.1433(a)) NESHAP subpart G at 40 


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49 30 TAC 115, subchapters D and H, Division 3. 

50Hancy. 2011. Memorandum from Hancy, C., 

RTI International, to Howard, J., EPA/OAQPS. 

Analysis of Emissions Reduction Techniques for 

Equipment Leaks. December 21, 2011. EPA Docket 

ID No. EPA–HQ–OAR–2010–0869. 

CFR 63.132 through 63.147, which 

provide owners and operators several 

control options for wastewater tanks, 

surface impoundments, containers, 

individual drain systems, and oil-water 

separators. NESHAP subpart G also 

specifies performance standards for 

treating wastewater streams using open 

or closed biological treatment systems 

or using a design steam stripper with 

vent control. For APCDs (e.g., thermal 

oxidizers) used to control emissions 

from collection system components, 

steam strippers, or closed biological 

treatment systems, NESHAP subpart G 

provides owners or operators several 

compliance options, including 95- 

percent destruction efficiency, a 20- 

ppmv outlet concentration, or 

temperature and residence time design 

specifications for enclosed combustion 

devices. 

The HON maintenance wastewater 

standards that PEPO sources are 

currently subject to directly reference 

(with exceptions specified in 40 CFR 

63.1433(b)) NESHAP subpart F at 40 

CFR 63.105, which requires owners or 

operators to prepare a description of the 

maintenance procedures for managing 

wastewaters generated from the 

emptying and purging of equipment 

during shutdowns, maintenance, and 

repair. For certain liquid streams in 

open systems within a PMPU, NESHAP 

subpart G requires drain, manhole, lift 

station, and trench components to be 

equipped with a tightly fitting solid 

cover, a cover with vent control, or 

water seals; pipes to have no visible 

gaps or other emissions interfaces; oil/ 

water separators to be equipped with a 

fixed roof with vent control or a floating 

roof; and tanks to have a fixed roof (with 

vent control if the tank contents are 

sparged, are heated, or are treated using 

an exothermic reaction). 

As part of our CAA section 112(d)(6) 

technology review for PEPO wastewater 

streams (i.e., broader than our review of 

wastewater streams in EtO service 

discussed in section IV.B.2.d of this 

preamble), we evaluated tightening the 

PEPO wastewater Group 1 applicability 

thresholds. Specifically, we evaluated 

the option to require owners and 

operators to manage and treat existing 

wastewater streams with total annual 

average concentration of compounds 

specified in table 4 to 40 CFR part 63, 

subpart PPP (that are also in table 9 to 

NESHAP subpart G) greater than or 

equal to 1,000 ppmw at any flow rate, 

or greater than or equal to 10 ppmw at 

a flow rate of 10 lpm or greater. 

Table 10 of this preamble presents the 

nationwide costs and impacts for the 

wastewater stream control option 

considered for PEPO facilities. For 

details on the assumptions and 

methodologies used in this analysis, see 

the document titled Clean Air Act 

Section 112(d)(6) Technology Review for 

Wastewater Streams Located in the 

PEPO Production Source Category that 

are Associated with Processes Subject to 

the PEPO NESHAP, which is available 

in the docket for this rulemaking. 

TABLE 10—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF THE CONTROL OPTION CONSIDERED FOR

WASTEWATER STREAMS AT PEPO FACILITIES

Control option 

Total 

capital 

investment 

($) 

Total 

annualized 

costs 

($/yr) 

VOC 

emission 

reductions 

(tpy) 

Organic 

HAP 

emission 

reductions 

(tpy) 

Organic 

HAP cost 

effectiveness 

($/ton) 

1 ........................................................................................... 57,128,000 22,600,000 693 693 32,600 

We determined that the option to 

revise wastewater stream Group 1 

threshold applicability in the PEPO 

NESHAP (i.e., to require control of 

existing wastewater streams with total 

annual average concentration of table 4 

to subpart PPP compounds (that are also 

in table 9 to NESHAP subpart G) greater 

than or equal to 1,000 ppmw at any flow 

rate, or greater than or equal to 10 

ppmw at a flow rate of 10 lpm or 

greater) is not cost effective based on the 

costs and emission reductions 

presented. Therefore, we are not 

proposing to revise the PEPO NESHAP 

to reflect the requirements of this option 

pursuant to CAA section 112(d)(6). 

5. Standards for Equipment Leaks 

As previously mentioned in this 

preamble, emissions of VOC and HAP 

from equipment leaks occur in the form 

of gases or liquids that escape to the 

atmosphere through many types of 

connection points (e.g., threaded 

fittings) or through the moving parts of 

certain types of process equipment 

during normal operation. Equipment 

regulated by the PEPO NESHAP 

includes agitators, compressors, 

connectors, instrumentation systems, 

OEL, PRDs, pumps, sampling collection 

systems, and valves that contain or 

contact material having 5 percent by 

weight or more of organic HAP, operate 

300 hours per year or more, and are not 

in vacuum service. 

The equipment leak standards that 

PEPO sources are currently subject to 

directly reference the provisions in the 

HON at 40 CFR part 63, subpart H, 

which require LDAR using monitoring 

with EPA Method 21 of appendix A–7 

to 40 CFR part 60 at certain frequencies 

(e.g., monthly, quarterly, every 2 

quarters, annually) and varying leak 

definitions (e.g., 500 ppmv; 1,000 ppmv; 

10,000 ppmv) depending on the type of 

component and service (e.g., in gas and 

vapor service or in light liquid service). 

The LDAR requirements for components 

in heavy liquid service include sensory 

monitoring (e.g., visual, audible, 

olfactory). 

The practices, processes, and control 

technologies we considered during 

MACT development for equipment 

leaks at PEPO facilities included LDAR 

and equipment standards. To identify 

developments for the technology 

review, we evaluated responses to our 

CAA section 114 request, the RACT/ 

BACT/LAER database, and other 

Federal regulations (i.e., the Petroleum 

Refinery Sector rule, HON, MON, and 

NSPS subpart VVb) and State 

regulations (i.e., the Texas fugitive 

emissions rules 49 applicable to 

petrochemical processes). Also, the EPA 

conducted a general analysis in a 2011 

equipment leaks study 50 to identify the 

latest developments in practices, 

processes, and control technologies for 

equipment leaks at chemical 

manufacturing facilities and petroleum 

refineries, and to estimate the impacts of 

applying those practices, processes, and 

control technologies to model facilities. 

We used this 2011 equipment leaks 

analysis as a reference for conducting 

the technology review for equipment 

leaks at PEPO facilities. 

Our technology review for equipment 

leaks of HAP (i.e., broader than the EtO 


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51We note that while other technologies such as 

optical gas imaging and sensor networks may be 

considered developments in monitoring for 

equipment leaks, the EPA did not evaluate those 

options further as we have insufficient information 

on how use of such monitoring technology 

compares to current EPA Method 21 practices for 

chemical sector sources. 

52We used data provided to the EPA in response 

to our CAA section 114 request to estimate an 

average of two PMPUs per facility for the 16 PEPO 

facilities that did not receive the CAA section 114 

request. Including the estimate for the 16 PEPO 

facilities that did not receive the CAA section 114 

request with the 18 PMPUs that were reported in 

the CAA section 114 request, we estimate 50 

PMPUs nationwide. 

emissions discussed in section IV.B.2.b 

of this preamble) did not find any new 

control technologies for equipment leak 

emissions to evaluate. However, we did 

identify developments in LDAR 

practices and processes (i.e., lower leak 

definitions) for valves in gas and vapor 

service or in light liquid service, and 

pumps in light liquid service. We 

evaluated three control options to 

reduce HAP emissions from equipment 

leaks: (Control Option 1) lowering the 

leak definition for valves in light liquid 

service from 500 ppmv to 100 ppmv, 

(Control Option 2) same as Control 

Option 1, plus lowering the leak 

definition for valves in gas and vapor 

service from 500 ppmv to 100 ppmv, 

and (Control Option 3) same as Control 

Option 2, plus lowering the leak 

definition for pumps in light liquid 

service from 1,000 ppmv to 500 ppmv. 

For all other component and service 

types, we did not identify developments 

in LDAR practices and processes in the 

chemical sector.51

The EPA estimated emission 

reductions for the developments that we 

identified using component counts and 

emission factors. We derived the 

component counts using data provided 

to the EPA in response to our CAA 

section 114 request (see section II.C of 

this preamble) and we developed model 

component counts for 25 PEPO 

facilities. We then multiplied the 

number of nationwide PEPO 

processes 52 by the model component 

counts to estimate the nationwide 

component counts. Subsequently, we 

calculated baseline emissions and 

emissions after implementation of the 

proposed controls for each component 

using these nationwide component 

counts and emission factors and leak 

frequencies for the chemical 

manufacturing industry obtained from 

the 2011 equipment leaks study. 

The EPA then calculated the costs for 

the baseline and control options, which 

reflect the cost to implement an LDAR 

program for each component. Note that 

the difference between the costs for the 

baseline and control options is the 

incremental cost to comply with the 

control requirements. Furthermore, 

because the control options result in 

chemicals in process lines not leaking 

(i.e., not being lost), we present costs 

both with and without this 

consideration. To estimate savings in 

chemicals not being emitted (i.e., lost) 

due to the equipment leak control 

options, we applied a recovery credit of 

$900 per ton of VOC to the emission 

reductions in the analyses. 

We calculated the VOC and HAP cost 

effectiveness by dividing the 

incremental annual costs by the 

emissions reductions. Table 11 of this 

preamble presents the nationwide costs 

and impacts for the suite of equipment 

leak control options considered for 

PEPO facilities. For details on the 

assumptions and methodologies used in 

this analysis, see the document titled 

Clean Air Act Section 112(d)(6) 

Technology Review for Equipment Leaks 

Located in the PEPO Production Source 

Category that are Associated with 

Processes Subject to the PEPO NESHAP, 

which is available in the docket for this 

rulemaking. 

TABLE 11—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTIONS CONSIDERED FOR PEPO 

EQUIPMENT

Control option 

Total 

capital 

investment 

($) 

Total 

annualized 

costs w/o 

credits 

($/yr) 

Total 

annualized 

costs 

w/credits 

($/yr) 

Total HAP 

emission 

reductions 

(tpy) 

Average 

HAP cost 

effectiveness 

w/credits 

($/ton) 

Average 

HAP cost 

effectiveness 

w/o credits 

($/ton) 

Average 

incremental 

HAP cost 

effectiveness 

w/credits 

($/ton) 

1 .................................................................................... 42,300 11,700 9,200 2.20 4,200 5,300 

2 .................................................................................... 72,700 18,800 15,300 2.99 5,100 6,300 7,700 

3 .................................................................................... 99,000 28,100 24,200 3.29 7,400 8,500 30,500 

Based on the costs and emission 

reductions for each of the options, we 

determined that Control Option 2 

(which includes Control Option 1) is 

cost effective. Therefore, we are 

proposing, pursuant to CAA section 

112(d)(6), to revise the PEPO NESHAP 

at 40 CFR 63.1434(a)(7) to use a leak 

definition of 100 ppmv for valves that 

are in either gas/vapor service or light 

liquid service. In this action, we are not 

proposing to revise the PEPO NESHAP 

to reflect the requirements of Control 

Option 3 pursuant to CAA section 

112(d)(6), because we determined that 

Control Option 3 is not cost effective 

due to its high incremental HAP cost 

effectiveness (i.e., $30,500/ton of HAP) 

from Control Option 2. We solicit 

comments on the proposed revisions to 

the equipment leak requirements for the 

PEPO NESHAP. 

6. Standards for Fenceline Monitoring 

Fenceline monitoring refers to the 

placement of monitors along the 

perimeter of a facility to measure 

pollutant concentrations. Coupled with 

requirements for root cause analysis and 

corrective action upon triggering an 

actionable level, this work practice 

standard is a development in practices 

considered under CAA section 112(d)(6) 

for the purposes of managing fugitive 

emissions. The measurement of 

pollutant concentrations and 

comparison to concentrations estimated 

from mass emissions via dispersion 

modeling is used to verify emission 

estimates from a facility’s emissions 

inventory. If concentrations at the 

fenceline are greater than expected, 

potential causes may include 

underreported or unknown emissions, 

leaking equipment, or other issues, 

usually related to ground-level fugitive 

emissions. Fenceline monitoring also 

provides information on the location of 

these potential emissions sources 

because it provides complete spatial 

coverage of a facility. Further, when 

used with a mitigation strategy, such as 

root cause analysis and corrective action 

upon exceedance of an action level, 

fenceline monitoring can be effective in 

reducing emissions and reducing the 

uncertainty associated with emissions 

estimation and characterization. Finally, 

public reporting of fenceline monitoring 

data provides public transparency and 

greater visibility, leading to more focus 

and effort in reducing emissions. 


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53 40 CFR 63.658(f) through (h). 

54Quarterly fenceline monitoring reports are 

available through the EPA’s WebFIRE database at 

https://cfpub.epa.gov/webfire/. The EPA has also 

developed a dashboard to improve public access to 

this data. The dashboard is available at https:// 

awsedap.epa.gov/public/extensions/ 

Fenceline_Monitoring/Fenceline_Monitoring.html?

sheet=MonitoringDashboard. 

55 In the same action (see 89 FR 42932, May 16, 

2024), the EPA also finalized EPA Method 327 of 

40 CFR part 63, appendix A, as a canister sampling 

and analysis method that provides procedures for 

measuring trace levels of targeted VOC (including 

organic HAP) in ambient air. 

56See appendix 1 of the document titled Residual 

Risk Assessment for the Polyether Polyols (PEPO) 

Production Source Category in Support of the 2024 

Risk and Technology Review Proposed Rule, which 

is available in the docket for this rulemaking, for 

more details about development of the risk 

modeling file. 

57https://www.epa.gov/sites/default/files/2019- 

12/documents/to-15a_vocs.pdf. 

The EPA has successfully applied 

fenceline monitoring to the petroleum 

refineries source category as a technique 

to manage and reduce benzene 

emissions from fugitive emissions 

sources such as storage vessels, 

wastewater treatment systems, and 

leaking equipment. In 2015, the EPA 

promulgated the RTR for the petroleum 

refineries source category and required 

that refineries install and operate 

fenceline monitors following EPA 

Methods 325A/B to monitor benzene 

emissions. Additionally, the 2015 rule 

required that refineries conduct a root 

cause analysis to identify sources of 

high fenceline monitoring readings (i.e., 

above an annual action level) and then 

develop a corrective action plan to 

address the sources and reduce 

emissions to a level that will bring 

fenceline monitoring concentrations 

below the action level.53 To date, the 

EPA has received fenceline monitoring 

data for more than 5 years.54 These data 

show that petroleum refinery fenceline 

concentrations have dropped by an 

average of 30 percent since the 

inception of the monitoring program 

requirements and illustrate that 

fenceline monitoring is an effective tool 

in reducing emissions and preserving 

emission reductions on an ongoing basis 

for these sources. 

Additionally, in 2024, the EPA 

promulgated amendments to the HON 

(40 CFR part 63, subpart G) and the P&R 

I NESHAP (40 CFR part 63, subpart U) 

that included work practice standards 

requiring owners and operators to 

conduct fenceline monitoring for any of 

six specific HAP (i.e., benzene; 1,3- 

butadiene; ethylene dichloride; vinyl 

chloride; EtO; and chloroprene) if their 

affected source uses, produces, stores, or 

emits any of them, and conduct root 

cause analysis and corrective action 

upon exceeding annual average 

concentration action levels established 

for each HAP. The final HON and P&R 

I NESHAP amendments require owners 

and operators to conduct passive 

diffusive tube fenceline monitoring for 

benzene, 1,3-butadiene, chloroprene, 

and ethylene dichloride in accordance 

with EPA Methods 325A/B of 40 CFR 

part 63, appendix A, and to use canister 

sampling in accordance with EPA 

Method 327 of 40 CFR part 63, appendix 

A, for EtO and vinyl chloride.55

Given the similarities between PMPUs 

subject to the PEPO NESHAP and 

CMPU sources that are subject to the 

HON, we evaluated the application of 

fenceline monitoring at PEPO facilities 

as a development in practices, 

processes, and control technologies 

pursuant to CAA section 112(d)(6). Like 

some CMPUs, PMPUs can be a 

significant source of EtO emissions from 

ground-level or near ground level 

fugitive sources such as storage vessels, 

wastewater treatment systems, and 

leaking equipment. On the other hand, 

we determined that PMPUs are not 

significant sources of emissions of 

benzene, 1,3-butadiene, chloroprene, 

ethylene dichloride, and vinyl chloride. 

In the risk modeling file, which uses 

data from the 2017 NEI,56 we did not 

attribute any records of vinyl chloride or 

chloroprene emissions to PEPO 

processes, and only small amounts of 

1,3-butadiene, benzene, and ethylene 

dichloride emissions are attributed to 

PEPO processes (none of these 

emissions is clearly from a PMPU). Any 

significant emissions of these HAP from 

PEPO facilities are attributed to nonsource category emission sources from 

facilities that are subject to the HON 

fenceline monitoring requirements. 

Considering the available information, 

we conclude that, for the PEPO 

NESHAP, a fenceline monitoring 

requirement for EtO is appropriate, but 

a fenceline monitoring requirement for 

benzene, 1,3-butadiene, chloroprene, 

ethylene dichloride, and vinyl chloride 

would not lead to an appreciable 

reduction in emissions. 

Based on this information, the EPA is 

proposing in this action to implement a 

fenceline monitoring program under 

CAA section 112(d)(6) to limit fugitive 

emissions of EtO. We are proposing at 

40 CFR 63.1434(i), by reference to 40 

CFR 63.184, to require fenceline 

monitoring at facilities in the PEPO 

Production source category that use, 

produce, store, or emit EtO. A brief 

summary of the proposed fenceline 

sampling requirements and our 

rationale for selecting the corrective 

action concentration levels are provided 

as follows. We solicit comments on the 

proposed standards for fenceline 

monitoring. 

a. Developments in Monitoring 

Technology and Practices 

In developing the fenceline 

monitoring requirements for the 

Petroleum Refinery NESHAP, the HON, 

and the P&R I NESHAP, the EPA 

identified two different methods for 

monitoring fugitive emissions: (1) 

passive diffusive tube monitoring 

networks, and (2) canister monitoring 

networks. Given the similarities 

between PMPUs subject to the PEPO 

NESHAP and CMPU sources that are 

subject to the HON, and the extent of colocation between PEPO and HON 

facilities (15 of the 25 PEPO facilities 

are co-located with HON facilities), we 

considered these monitoring methods as 

developments in practices under CAA 

section 112(d)(6) for purposes of 

managing fugitive EtO emission sources 

at PEPO production facilities. 

In the promulgated amendments to 

the HON, the EPA finalized a new EPA 

method (EPA Method 327 of 40 CFR 

part 63, appendix A) to monitor the 

concentration of EtO at facility fenceline 

locations. EPA Method 327 provides 

procedures for canister sampling and 

analysis for measuring trace levels of 

targeted VOC (including organic HAP) 

in air. The method draws upon the 

guidance in Method TO–15A 57 for 

canister sampling and further develops 

this guidance into a robust method 

specific to fenceline monitoring, 

defining required data quality 

objectives, and incorporating existing 

best practices into the method. EPA 

Method 327 collects ambient air 

samples using specially prepared and 

pre-cleaned evacuated stainless-steel 

canisters. For analysis, the method 

specifies procedures for concentrating 

the target VOC (i.e., EtO) in a known 

volume of air drawn from the canister, 

desorbing the target VOC from the 

preconcentrator, and determining the 

concentration of the target VOC using a 

gas chromatograph–mass spectrometer 

(GC–MS). The EPA continues to 

investigate cost-effective monitoring 

methods and technologies that could 

offer improved sensitivity, improved 

time resolution, or increased time 

integration. 

In this action, the EPA is proposing at 

40 CFR 63.1434(i), by reference to 40 

CFR 63.184(b)(2), to require fenceline 

monitoring of EtO concentrations for 

one 24-hour period every 5 days using 

canister sampling in accordance with 


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58Calculated every 5 days for EtO. 

EPA Method 327 of 40 CFR part 63, 

appendix A. This monitoring frequency 

is necessary to ensure that all onsite 

processes are monitored regularly while 

maintaining the cost effectiveness of 

implementing a canister monitoring 

network. A sampling frequency of every 

5 days also ensures that the annual 

average concentration derived from the 

fenceline data are indicative of the 

actual average emissions from the site 

by reducing the possibility that 

sampling occurs only during emission 

spikes. Additionally, to accommodate 

continued advancements and 

improvements in monitoring 

technology, we are also proposing to 

amend the entry for 40 CFR 63.7(f) of 

table 1 to the PEPO NESHAP 

(applicability of the NESHAP general 

provisions) to clarify that an owner or 

operator can request to use another type 

of monitoring network to demonstrate 

compliance with the fenceline 

standards, provided they achieve 

adequate coverage and detection 

capabilities. 

b. Siting, Design, and Sampling 

Requirements for Fenceline Monitors 

The EPA is proposing at 40 CFR 

63.1434(i), by reference to 40 CFR 

63.184(b)(3), that owners or operators 

deploy monitors to measure fenceline 

concentrations of EtO at facilities 

subject to the PEPO NESHAP. A 

primary requirement for a fenceline 

monitoring system is that it provides 

adequate spatial coverage for 

determination of representative 

pollutant concentrations at the 

boundary of the facility. In an ideal 

scenario, owners or operators would 

place fenceline monitors so that any 

fugitive plume originating within the 

facility would have a high probability of 

intersecting one or more monitors, 

regardless of wind direction. Therefore, 

we are proposing that each facility 

would place eight canisters evenly 

spaced on the monitoring perimeter. 

The monitoring perimeter may be the 

facility fenceline or may be inside the 

facility fenceline, provided all sources 

of EtO are contained within the 

perimeter. The EPA is also proposing to 

require that facilities move the canister 

sampling locations with alternating 

sampling periods to ensure complete 

spatial coverage of the facility. For 

facilities with perimeters less than or 

equal to 5,000 meters, all eight sampling 

points would be monitored during each 

sampling period. For facilities with 

perimeters greater than 5,000 meters but 

less than or equal to 10,000 meters, 16 

sampling points would be required; for 

facilities with perimeters greater than 

10,000 meters, 24 sampling points 

would be required. For facilities with 

EtO emission sources that are not 

contained within one contiguous area, 

the EPA is proposing monitoring of 

these secondary areas as well, with the 

size of the secondary area dictating the 

number of canisters. While we recognize 

that EPA Method 325A contains an 

option for siting passive tubes by 

determining the geographic center of the 

facility and spacing the tubes based on 

measured angles from the center point, 

the EPA is not providing a similar 

approach to simplify the siting of the 

canisters. 

The EPA is proposing at 40 CFR 

63.1434(i), by reference to 40 CFR 

63.184(d), that for each 24-hour 

sampling period, the facility would 

determine a ‘‘delta c,’’ calculated as the 

lowest sample value for EtO subtracted 

from the highest sample value for EtO. 

This approach subtracts the estimated 

contribution from background emissions 

that do not originate from the facility. 

The owner or operator would average 

the delta c for the most recent year of 

samples (73 sampling periods) to 

calculate an annual average delta c on 

a rolling basis (i.e., calculate a new 

annual average delta c every 5 days 

using data from the most recent 73 

sampling periods). The owner or 

operator would compare this rolling 

annual average delta c against the 

concentration action level for EtO. 

c. Action Levels and Rationale 

As mentioned earlier in this 

preamble, the EPA is proposing to 

require facilities subject to the PEPO 

NESHAP to take corrective action to 

reduce fugitive emissions if monitored 

fenceline concentrations exceed the 

concentration action level on a rolling 

annual average basis.58

Due to current limitations in method 

detection limits for EtO, we selected the 

proposed fenceline action level to be 

equal to three times the representative 

detection limit (RDL) for EtO, as this is 

the minimum concentration that can be 

measured with reasonable certainty. The 

RDL is based on the results of the best 

performing testing companies and 

laboratories using the most sensitive 

analytical procedures. The EPA used a 

multiplication factor of three to reduce 

the imprecision of the method until the 

imprecision in the sampling and 

analysis is similar to the precision of 

other EPA methods. For the 2024 final 

amendments to the HON and P&R I 

NESHAP, the EPA determined an EtO 

RDL of 0.07 mg/m3, which resulted in an 

EtO action level of 0.2 mg/m3. Therefore, 

in this action the EPA is similarly 

proposing at 40 CFR 63.1434(i), by 

reference to 40 CFR 63.184(d)(3)(iv), an 

action level of 0.2 mg/m3 for EtO. If the 

reported inventories are accurate, and 

considering the anticipated emissions 

reductions from controls we are 

proposing, our modeling of fenceline 

EtO concentrations indicates that all 

facilities should be able to meet the 

fenceline concentration action level. For 

further details of the analysis, see the 

document titled Clean Air Act Section 

112(d)(6) Technology Review for 

Fenceline Monitoring Located at 

Facilities with PEPO Production 

Processes Subject to the PEPO NESHAP, 

which is available in the docket for this 

rulemaking. 

d. Non-Source Category Emissions 

This proposed approach also 

considers the possibility that offsite 

sources could contribute to modeled 

concentrations at a facility’s fenceline. 

Additionally, non-PEPO sources could 

be located within facility property 

boundaries that also contribute to 

monitor readings. In this proposal, we 

are allowing the subtraction of offsite 

interfering sources (as they are not 

within the control of the owner or 

operator) through site-specific 

monitoring plans, but we are not 

providing this option for onsite, nonsource category emissions. We based the 

action level on facility-wide emissions; 

therefore, we considered these nonsource category sources in its 

development. Applying the fenceline 

standard to the whole facility will also 

limit emissions of EtO from all sources 

and provide more certainty in decisions 

being made as to whether the entire 

facility emissions align with what is 

expected from the EPA’s analysis. It will 

also provide assurance to fenceline 

communities that emission reductions 

are achieved and maintained. This is 

important in the chemical sector, where 

there could be numerous source 

categories that can be co-located within 

a larger facility and have common tank 

farms, wastewater systems, heat 

exchangers, APCDs, fuel gas systems, 

etc., that may be assigned or 

apportioned to various source 

categories. 

e. Corrective Action Requirements 

The proposed fenceline monitoring 

provisions would require the initiation 

of root cause analysis upon the facility’s 

annual average concentration exceeding 

the action level, as determined on a 

rolling average every sampling period. 

The root cause analysis is an assessment 

conducted through a process of 

investigation to determine the primary 

underlying cause and other contributing 


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59The EPA is proposing that three sample periods 

must remain below the action level for samples 

taken by EPA Method 327 because this ensures that 

a sample will have been taken at every monitoring 

location at the site following the completion of the 

corrective action. 

causes of an exceedance of the action 

level. The proposed provisions at 40 

CFR 63.1434(i), by reference to 40 CFR 

63.184(e)(1), would require an owner or 

operator to initiate a root cause analysis 

within 5 days of determining that an 

updated annual average concentration 

for EtO exceeds the action level. Owners 

or operators must conduct a root cause 

analysis following each sampling period 

in which the annual average EtO 

concentration remain above the action 

level, to determine whether the 

monitoring results and associated data 

indicate additional sources of emissions 

contributing to concentrations 

remaining above the action level. If the 

owner or operator cannot determine the 

root cause of the exceedance within 30 

days of determining that there was an 

exceedance of an action level, the 

proposed revisions require use of realtime sampling techniques (e.g., mobile 

gas chromatographs) to determine the 

root cause of the exceedance. 

If the underlying causes of the action 

level exceedance are deemed to be from 

sources under the control of the owner 

or operator, we are proposing that the 

owner or operator take corrective action 

to address the underlying cause of the 

exceedance and to reduce 

concentrations below the action level as 

expeditiously as possible. We are 

proposing that owners or operators 

complete the root cause analysis and 

initial corrective action within 45 days 

after determining that there was an 

exceedance of the action level. If the 

owner or operator requires longer than 

45 days to implement the corrective 

actions identified by the root cause 

analysis, the owner or operator would 

be required to submit a corrective action 

plan no later than 60 days after 

completion of the root cause analysis. 

After completion of the initial 

corrective action, if the delta c for each 

of the next three sampling periods for 

samples collected by EPA Method 327 59

is below the action level, then the 

corrective action is assumed to have 

fixed the problem, and the owner and/ 

or operator would have no obligation for 

additional corrective action. However, if 

the delta c for any of the three 

subsequent sampling periods after 

initial corrective action is over the 

action level, then the owner or operator 

would have to submit a corrective 

action plan and schedule for 

implementing design, operation, and 

maintenance changes to eliminate as 

quickly as possible and prevent 

recurrence of the primary cause and 

other contributing causes to the 

exceedance of the action level, to reduce 

annual average concentrations below 

the action level. The proposed 

provisions would require the owner or 

operator to include the implementation 

of real-time sampling techniques to 

locate the primary and other 

contributing causes of the exceedance in 

the corrective action plan. While the 

action level is based on annual average 

concentrations, once the action level is 

exceeded, each sampling period that 

exceeds the action level contributes to 

the delta c remaining above the action 

level. Following these high biweekly 

periods, owners or operators must 

investigate to determine the root cause 

and, if appropriate, to correct the root 

cause expeditiously to reduce the 

annual average delta c below the action 

level. 

f. Costs Associated With Fenceline 

Monitoring Requirements 

Our cost estimate for implementing 

the same EtO fenceline monitoring work 

practice standard that is in the HON for 

the PEPO NESHAP follows the cost 

analysis already discussed in the 

document titled Clean Air Act Section 

112(d)(6) Technology Review for 

Fenceline Monitoring located in the 

SOCMI Source Category that are 

Associated with Processes Subject to 

HON and for Fenceline Monitoring that 

are Associated with Processes Subject to 

Group I Polymers and Resins NESHAP 

(Docket Item No. EPA–HQ–OAR–2022– 

0730–0091). We estimated fenceline 

monitoring costs for eight canisters 

around the fenceline every 5 days. Table 

12 of this preamble provides the 

estimated nationwide costs for fenceline 

monitoring as applied to facilities 

subject to the PEPO NESHAP. Note that 

12 of the impacted facilities covered 

under the analysis have co-located 

sources subject to both the HON and the 

PEPO NESHAP and require EtO 

fenceline monitoring under both rules. 

For the purposes of this analysis, costs 

for these co-located facilities are 

included under the SOCMI source 

category for impacts to prevent costs 

being double counted. For further 

information, see the document titled 

Clean Air Act Section 112(d)(6) 

Technology Review for Fenceline 

Monitoring Located at Facilities with 

PEPO Production Processes Subject to 

the PEPO NESHAP, which is available 

in the docket for this rulemaking. 

TABLE 12—NATIONWIDE COST IMPACTS OF FENCELINE MONITORING FOR THE PEPO NESHAP 

No. of 

facilities 

impacted 

Monitoring description 

Total capital 

investment 

($) 

Total 

annualized 

costs 

($/yr) 

10 ................. Canisters only ................................................................................................................................ 88,720 4,453,600 

g. Additional Requirements of the 

Fenceline Monitoring Program 

The EPA is proposing, by reference to 

the HON at 40 CFR 63.182(e), that 

owners or operators report fenceline 

data on a quarterly basis. Each report 

would contain the results for each 

sample where the field portion of 

sampling is completed by the end of the 

quarter, as well as for associated field 

and method blanks (i.e., each report 

would contain data for at 18 canister 

sampling periods). Owners or operators 

would report these data electronically to 

the EPA within 45 days after the end of 

each quarterly period. See section IV.E.2 

of this preamble for further discussion 

on electronic reporting and section IV.F 

of this preamble for further discussion 

on the compliance dates we are 

proposing. 

D. What actions are we taking pursuant 

to CAA sections 112(d)(2) and (3) and 

112(h)? 

In addition to the proposed actions 

discussed in section IV.B of this 

preamble to reduce risk from EtO 

emission sources (from PEPO processes) 

and our proposed actions discussed in 

section IV.C of this preamble based on 

our on technology review, we are 

proposing other requirements for the 

PEPO NESHAP, based on analyses 


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60The EPA has authority under CAA section 

112(d)(2) and (3) to set MACT standards for 

previously unregulated emission points. The EPA 

also retains the discretion to revise a MACT 

standard under the authority of CAA section 

112(d)(2) and (3) (see Portland Cement Ass’n v. 

EPA, 665 F.3d 177, 189 (D.C. Cir. 2011)), such as 

when it identifies an error in the original standard. 

See also Medical Waste Inst. v. EPA, 645 F.3d 420, 

426 (D.C. Cir. 2011) (upholding the EPA action 

establishing MACT floors, based on postcompliance data, when originally-established floors 

were improperly established). 

61The PEPO NESHAP requires that emission 

limits apply at all times (see 40 CFR 63.1420(h)). 

62For a list of studies, refer to the technical report 

titled Parameters for Properly Designed and 

Operated Flares, in Docket Item No. EPA–HQ– 

OAR–2010–0682–0191. 

63See 40 CFR 63.670 and 63.671 (originally 

finalized in 80 FR 75178 on December 1, 2015; and 

amended at 81 FR 45232 on July 13, 2016, 83 FR 

60696 on November 26, 2018, 85 FR 6064 on 

February 4, 2020, and 89 FR 23860 on April 4, 

2024). 

64See section II.D. of this preamble, which 

addresses the incorporation by reference of certain 

docket files such as this one into the docket for this 

rulemaking. 

65These documents can be found at https:// 

www.epa.gov/stationary-sources-air-pollution/ 

review-peer-review-parameters-properly-designedand-operated-flares. 

66See the document titled Flare Performance 

Data: Summary of Peer Review Comments and 

Additional Data Analysis for Steam-Assisted Flares 

in Docket Item No. EPA–HQ–OAR–2010–0682– 

0200 for a more detailed discussion of the data 

quality and analysis; the document titled Petroleum 

performed pursuant to CAA sections 

112(d)(2) and (3) and 112(h).60 61 We are 

proposing to: (1) add new monitoring 

and operational requirements for flares 

used to reduce emissions from PEPO 

production processes, (2) clarify 

regulatory provisions for vent control 

bypasses for closed vent systems 

containing bypass lines, (3) add work 

practice standards for startup and 

shutdown periods for maintenance 

vents and planned routine maintenance 

of storage vessels, (4) add new 

monitoring requirements for PEPO 

pressure vessels, (5) add new emission 

standards for PEPO surge control vessels 

and bottoms receivers, (6) add new 

emission standards for PEPO transfer 

operations, (7) add butylene oxide to the 

list of HAP presented in table 4 to 

subpart PPP, and (8) remove the 40 CFR 

63.1420(d)(3) exemption for certain 

processes currently excluded from the 

affected source. See the following 

subsections for specific details regarding 

these proposed actions. 

1. Flares 

The EPA is proposing under CAA 

section 112(d)(2) and (3) to amend the 

operating and monitoring requirements 

for flares, which are commonly used as 

APCDs in the PEPO Production source 

category, because we have determined 

that the current requirements for flares 

are not adequate to ensure the level of 

destruction efficiency needed to comply 

with the process vent, storage vessel, 

wastewater stream, and equipment leak 

MACT standards in the PEPO NESHAP. 

The requirements applicable to flares, 

which are used to control emissions 

from various emission sources, are set 

forth in the general provisions of 40 CFR 

part 63 and are cross-referenced in the 

PEPO NESHAP. 

The general provisions of 40 CFR 

63.11(b) specify that flares be: (1) steamassisted, air-assisted, or non-assisted; (2) 

operated at all times when emissions 

may be vented to them; (3) designed for 

and operated with no visible emissions 

(except for periods not to exceed a total 

of 5 minutes during any 2 consecutive 

hours); and (4) operated with the 

presence of a pilot flame at all times. 

These general provisions also specify 

both the minimum heat content of gas 

combusted in the flare and the 

maximum exit velocity at the flare tip. 

The general provisions specify 

monitoring for the presence of the pilot 

flame and the operation of a flare with 

no visible emissions. 

In general, flares used as APCDs are 

expected to achieve 98-percent HAP 

destruction efficiencies when designed 

and operated according to the 

requirements in the general provisions. 

Studies on flare performance,62

however, indicate that these general 

provision requirements are inadequate 

to ensure proper performance of flares at 

refineries and other petrochemical 

facilities, particularly when the flares 

are either steam- or air-assisted. In 

addition, over the last decade, flare 

minimization efforts at these facilities 

have led to an increasing number of 

flares operating at well below their 

design capacity, and while these efforts 

have resulted in reduced flaring of 

gases, situations of over-assisting with 

either steam or air have become 

exacerbated, leading to the degradation 

of flare combustion efficiency. Many 

PEPO facilities operate directly 

downstream from refineries and other 

petrochemical plants (e.g., ethylene and 

EtO production plants) and, 

consequently, they likely flare waste gas 

constituents that are similar to those of 

a refinery or petrochemical plant. Given 

that the flare dataset that formed the 

underlying basis of the new standards 

for refinery flares also included flares at 

petrochemical plants, we are proposing 

at 40 CFR 63.1426(a) and (e)(2)(i), 

63.1429(a)(8), 63.1430(b)(1), and 

63.1437(c), each by reference to 

proposed 40 CFR 63.1436, to apply the 

finalized suite of operational and 

monitoring requirements for refinery 

flares 63 to those flares in the PEPO 

Production source category that control 

emissions from PEPO processes. 

Therefore, these proposed amendments 

at 40 CFR 63.1436 will ensure that 

continuous compliance with the CAA 

section 112(d)(2) and (3) standards is 

achieved for PEPO facilities that use 

flares as APCDs to meet the MACT 

standards at all times when controlling 

HAP emissions. We are also proposing 

to revise the entry for 40 CFR 63.11 of 

table 1 to the PEPO NESHAP to show 

that the provisions at 40 CFR 63.11(b) 

do not apply to flares because we are 

proposing to replace these provisions 

with new standards for flares used to 

comply with the MACT standards in the 

PEPO NESHAP. 

In 2012, the EPA compiled 

information and test data collected on 

flares and summarized its preliminary 

findings on operating parameters that 

affect flare combustion efficiency in a 

technical report titled Parameters for 

Properly Designed and Operated Flares, 

available in Docket Item No. EPA–HQ– 

OAR–2010–0682–0191.64 The EPA 

submitted this report, along with a 

charge statement and a set of charge 

questions, to an external peer review 

panel.65 The panel, consisting of 

individuals representing a variety of 

backgrounds and perspectives (i.e., 

industry, academia, environmental 

experts, and industrial flare 

consultants), concurred with the EPA’s 

assessment that the following three 

primary factors affect flare performance: 

(1) the flow of the vent gas to the flare; 

(2) the amount of assist media (e.g., 

steam or air) added to the flare; and (3) 

the combustibility of the vent gas/assist 

media mixture in the combustion zone 

(i.e., the net heating value, lower 

flammability, and/or combustibles 

concentration) at the flare tip. In 

response to peer review comments, the 

EPA performed a validation and 

usability analysis on all available test 

data as well as a failure analysis on 

potential parameters discussed in the 

technical report as indicators of flare 

performance. The document titled Peer 

Review of Parameters for Properly 

Designed and Operated Flares, which is 

available in Docket Item No. EPA–HQ– 

OAR–2010–0682–0193, contains the 

peer review comments, and we have 

incorporated that document into the 

docket for this rulemaking. These 

analyses resulted in a change to the 

population of test data that the EPA 

evaluated, and they helped form the 

basis for the flare operating limits 

promulgated in the 2015 Petroleum 

Refinery Sector final rule at 40 CFR part 

63, subpart CC (80 FR 75178).66 In this 


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Refinery Sector Rule: Operating Limits for Flares in 

Docket Item No. EPA–HQ–OAR–2010–0682–0206 

for a more detailed discussion of the failure 

analysis, and the document titled Flare Control 

Option Impacts for Final Refinery Sector Rule in 

Docket Item No. EPA–HQ–OAR–2010–0682–0748 

for additional analyses on flare performance 

standards based on public comments received on 

the proposed Petroleum Refinery Sector rule. 

67Refer to proposed 40 CFR 63.1436(a)(1) through 

(25) for a list of provisions that would no longer 

apply. 

action, we are also relying on the flare 

analyses discussed earlier in this 

preamble and proposing to apply the 

operating limits contained in the final 

rule for petroleum refineries to the flares 

used as APCDs in the PEPO Production 

source category (hereafter referred to as 

‘‘PEPO flares’’). The Agency believes, 

given the results from the various data 

analyses conducted for the Petroleum 

Refinery Sector rule, that the operating 

limits promulgated for flares used in the 

petroleum refinery sector are also 

appropriate and reasonable for PEPO 

flares to ensure that these flares meet 

the HAP destruction and removal 

efficiency at all times, consistent with 

the MACT standards established in the 

PEPO NESHAP in 1999 (64 FR 29420). 

Therefore, we are proposing at 40 CFR 

63.1436 to replace all flare requirements 

throughout the PEPO NESHAP 67 with 

the Petroleum Refinery Sector rule flare 

definitions and requirements in 40 CFR 

part 63, subpart CC, with certain 

clarifications and exemptions discussed 

in this section of the preamble, 

including, but not limited to, specifying 

that several definitions in 40 CFR part 

63, subpart CC, that apply to petroleum 

refinery flares also apply to flares in the 

PEPO Production source category, 

adding a definition and requirements for 

pressure-assisted multi-point flares, and 

specifying additional requirements for 

when an owner or operator uses a gas 

chromatograph or mass spectrometer for 

compositional analysis. 

The remainder of this section of the 

preamble includes a discussion of 

requirements that we are proposing for 

PEPO flares, along with impacts and 

costs associated with these proposed 

revisions. Specifically, this action 

proposes to require that PEPO flares 

operate pilot flame systems 

continuously and that flares operate 

with no visible emissions (except for 

periods not to exceed a total of 5 

minutes during any 2 consecutive 

hours) when the flare vent gas flow rate 

is below the smokeless capacity of the 

flare. In addition, this action proposes to 

consolidate measures related to flare tip 

velocity and proposes new operational 

and monitoring requirements related to 

the combustion zone gas. Further, this 

action proposes a work practice 

standard related to the visible emissions 

during periods when the flare is 

operated above its smokeless capacity 

(e.g., periods of emergency flaring). 

Currently, the MACT standards in the 

PEPO NESHAP cross-reference the 

general provisions at 40 CFR 63.11(b) 

for the operational requirements for 

flares used as APCD. This proposal 

eliminates cross-references to the 

general provisions and instead specifies 

all new operational and monitoring 

requirements that are intended to apply 

to flares used as APCDs in the PEPO 

NESHAP. 

a. Pilot Flames 

The PEPO NESHAP references the 

flare requirements in 40 CFR 63.11(b), 

which specify that a flare used as an 

APCD should operate with a pilot flame 

present at all times. The provisions at 40 

CFR 63.1429(a)(2) also require a device 

(including but not limited to a 

thermocouple, ultraviolet beam sensor, 

or infrared sensor) capable of 

continuously detecting the presence of a 

pilot flame. Pilot flames are proven to 

improve flare flame stability, and even 

short durations of an extinguished flame 

could cause a significant reduction in 

flare destruction efficiency. In this 

proposal, we are proposing to remove 

the cross-reference to the general 

provisions for PEPO flares and the 

requirement at 40 CFR 63.1429(a)(2), 

and instead cross-reference 40 CFR part 

63, subpart CC, to include in the PEPO 

NESHAP the existing provisions 

requiring that flares operate with a pilot 

flame at all times and that owners or 

operators continuously monitor for a 

pilot flame using a thermocouple or any 

other equivalent device. We are also 

proposing to add a continuous 

compliance provision that would 

consider each 15-minute block where 

there is at least 1 minute without a pilot 

flame present when regulated material 

is routed to the flare as a violation of the 

standard. Refer to 40 CFR 63.1436 and 

63.670(b) and (g) for these proposed 

requirements. See section IV.D.1.e of 

this preamble for our rationale for 

proposing to use a 15-minute block 

averaging period for determining 

continuous compliance. We solicit 

comments on the proposed revisions for 

flare pilot flames. 

b. Visible Emissions 

The PEPO NESHAP references 40 CFR 

63.11(b), which specifies that a flare 

used as an APCD should operate with 

visible emissions for no more than 5 

minutes in a 2-hour period. Owners or 

operators of these flares are required to 

conduct an initial performance 

demonstration for visible emissions 

using EPA Method 22 of appendix A– 

7 to 40 CFR part 60. We are proposing 

to remove the cross-reference to the 

general provisions for PEPO flares and 

instead cross-reference 40 CFR part 63, 

subpart CC, to include this same 

limitation on visible emissions. We are 

also proposing to clarify that owners or 

operators should conduct an initial 2- 

hour visible emissions demonstration 

the first time that regulated materials are 

routed to the flare. 

With regard to continuous compliance 

with the visible emissions limitation, 

we are proposing daily visible emissions 

monitoring for PEPO flares whenever 

regulated material is routed to the flare 

and also visible emissions monitoring 

whenever owners or operators observe 

visible emissions from the flare. On 

days that the flare receives regulated 

material, we are proposing that owners 

or operators of PEPO flares monitor 

visible emissions at a minimum of once 

per day while the flare is receiving 

regulated material using an observation 

period of 5 minutes and EPA Method 

22. Additionally, whenever regulated 

material is routed to a flare and there are 

visual emissions from the flare, we are 

proposing that owners or operators 

perform another 5-minute visible 

emissions observation using EPA 

Method 22, even if they have already 

performed the minimum required daily 

visible emission monitoring. For 

example, if an employee observes 

visible emissions, the owner or operator 

of the flare would perform a 5-minute 

EPA Method 22 observation to check for 

compliance upon initial observation or 

notification of such event. In addition, 

in lieu of daily visible emissions 

observations performed using EPA 

Method 22, we are proposing that 

owners and operators be allowed to use 

video surveillance cameras. We believe 

that video surveillance cameras would 

be at least as effective for the PEPO 

flares as the proposed daily 5-minute 

visible emissions observations using 

EPA Method 22. 

We are also proposing to extend the 

observation period for a PEPO flare to 2 

hours whenever visible emissions are 

observed for greater than 1 continuous 

minute during any of the 5-minute 

observation periods. Refer to 40 CFR 

63.1436 and 63.670(c) and (h) for these 

proposed requirements. We 

acknowledge that operating a flare near 

the incipient smoke point (the point at 

which black smoke begins to form 

within the flame) results in good 

combustion at the flare tip; however, 

smoking flares can contribute 

significantly to emissions of particulate 

matter that is 2.5 micrometers in 

diameter or smaller. Thus, while 


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68See EPA–HQ–OAR–2010–0682–0793, EPA– 

HQ–OAR–2010–0682–0794, and EPA–HQ–OAR– 

2017–0357–0017. 

increasing the allowable period for 

visible emissions may be useful from an 

operational perspective, we do not 

believe the allowable period for visible 

emissions should be increased to more 

than 5 minutes in any 2-hour period. 

We solicit comments on the proposed 

allowable period for visible emissions 

from flares. 

As discussed later in this section, we 

are proposing additional operational 

and monitoring requirements for PEPO 

flares that we expect will result in 

owners or operators of PMPUs installing 

equipment that can be used to fine-tune 

and control the amount of assist steam 

or air introduced at the flare tip, thereby 

maximizing the flare combustion 

efficiency. These monitoring and 

control systems will assist flare owners 

or operators in operating near the 

incipient smoke point without 

exceeding the visible emissions limit. 

While combustion efficiency may be 

highest at the incipient smoke point, it 

is not significantly higher than the 

combustion efficiency achieved by the 

proposed operating limits discussed in 

section IV.D.1.d of this preamble. As 

seen in the performance curves for 

flares, there is very limited 

improvement in flare performance 

beyond the performance achieved at the 

proposed operating limits (see 

document titled Petroleum Refinery 

Sector Rule: Operating Limits for Flares, 

available in Docket Item No. EPA–HQ– 

OAR–2010–0682–0206, which we have 

incorporated into the docket for this 

rulemaking). We solicit comments and 

data on appropriate periods of visible 

emissions that would encourage flare 

operation at the incipient smoke point. 

In addition, we are proposing that the 

owner or operator establish the 

smokeless capacity of each PEPO flare 

based on design specification of the 

flare and that the visible emissions 

limitation only apply when the flare 

vent gas flow rate is below its smokeless 

capacity. We are proposing a work 

practice standard that applies during 

emergency releases when the flow to a 

flare exceeds the smokeless capacity of 

the flare, based on comments the EPA 

received on the proposed Petroleum 

Refinery Sector rule. Refer to 40 CFR 

63.1436 and 63.670(o) for these 

proposed provisions. In the Petroleum 

Refinery Sector final rule, the EPA 

explained that numerous comments on 

the proposal suggested that flares are 

not designed to meet the visible 

emissions requirements when operated 

beyond their smokeless capacity (80 FR 

75178). According to commenters, flares 

are typically designed to operate in a 

smokeless manner at 20- to 30-percent 

of full hydraulic load. Thus, they 

claimed, flares have two different design 

capacities: (1) a ‘‘smokeless capacity’’ to 

handle normal operations and typical 

process variations, and (2) a ‘‘hydraulic 

load capacity’’ to handle very large 

volumes of gases discharged to the flare 

as a result of an emergency shutdown. 

According to commenters, these 

capacity considerations are inherent in 

all flare designs, and the issue of flares 

not meeting visible emissions 

requirements when beyond their 

smokeless capacity has not previously 

been an issue because flare operating 

limits did not apply during malfunction 

events. 

For this proposed work practice 

standard, the NESHAP would require 

owners or operators to develop a flare 

management plan for PEPO flares that 

identifies procedures for limiting 

discharges to the flare as a result of 

process upsets or malfunctions that 

cause the flare to exceed its smokeless 

capacity. In addition, for any flare that 

exceeds both the smokeless design 

capacity and visible emissions limit, we 

are proposing that owners or operators 

conduct a specific root cause analysis 

and take corrective action to prevent the 

recurrence of a similarly caused event. 

We are proposing that if the root cause 

analysis indicates that the exceedance of 

the visible emissions limit is caused by 

operator error or poor maintenance, 

then the exceedance would be 

considered a violation of the work 

practice standard. We are also proposing 

that a second event that occurs within 

a rolling 3-year period from the same 

root cause on the same equipment 

would be considered a violation of the 

standard. Finally, we are proposing that 

a third visible emissions limit 

exceedance occurring from the same 

flare in a rolling 3-year period would be 

a violation of the work practice 

standard, regardless of the cause. 

In several of the EPA’s previous 

impact analyses (for petroleum refinery 

flares and ethylene production flares),68

the EPA established the number of 

events in a given time period that would 

be the ‘‘backstop’’ (i.e., a violation of the 

standard). In each of these analyses, the 

EPA evaluated four different timing 

alternatives (two events in 5 years; two 

events in 3 years; two events in 5 years; 

and three events in 3 years) based on the 

number of existing flares evaluated over 

a 20-year period, and ultimately 

concluded that three events in 3 years 

would be ‘‘achievable’’ for the average 

of the best performing flares. We see no 

reason why this would be any different 

for PEPO flares. Even if a bestperforming flare ‘‘typically’’ only has 

one event every 7 years, the fact that 

these events are random by nature 

(unpredictable, not under the direct 

control of the owner or operator) makes 

it difficult to use a 5-year time span. 

Based on this analysis, three events in 

3 years would appear to be ‘‘achievable’’ 

for the average of the best performing 

flares. 

c. Flare Tip Velocity 

This proposed action consolidates 

provisions related to flare tip velocity 

for PEPO flares. The PEPO NESHAP 

references the flare provisions in 40 CFR 

63.11(b), which specify maximum flare 

tip velocities based on flare type (nonassisted, steam-assisted, or air-assisted) 

and the net heating value of the flare 

vent gas. Based on data provided to the 

EPA in response to our CAA section 114 

request (see section II.C of this 

preamble), four of the nine flares that 

PEPO facilities reported using as APCDs 

are either steam- or air-assisted (see the 

document titled Control Option Impacts 

for Flares in the PEPO Production 

Source Category that Control Emissions 

from Processes Subject to the PEPO 

NESHAP, which is available in the 

docket for this rulemaking). Maximum 

flare tip velocities are required to ensure 

that the flame does not ‘‘lift off’’ the 

flare (i.e., a condition where a flame 

separates from the tip of the flare and 

there is space between the flare tip and 

the bottom of the flame), which could 

cause flame instability and/or 

potentially result in a portion of the 

flare gas being released without proper 

combustion. We are proposing to 

remove the cross-reference to the 

general provisions for PEPO flares and 

instead to cross-reference 40 CFR part 

63, subpart CC, to consolidate the 

provisions for maximum flare tip 

velocity into the PEPO NESHAP as a 

single equation, irrespective of flare 

type (i.e., steam-assisted, air-assisted, or 

non-assisted). Refer to 40 CFR 63.1436 

and 63.670(d), (i), and (k) for these 

proposed provisions. 

Based on analysis conducted for the 

Petroleum Refinery Sector rule, the EPA 

identified test runs of air-assisted flares 

with high tip velocities that had high 

combustion efficiencies (see the 

document titled Petroleum Refinery 

Sector Rule: Evaluation of Flare Tip 

Velocity Requirements in Docket Item 

No. EPA–HQ–OAR–2010–0682–0212). 

These test runs exceeded the maximum 

flare tip velocity limits for air-assisted 

flares using the linear equation in 40 

CFR 63.11(b)(8). When the EPA 

compared these test runs to the test runs 

for non-assisted and steam-assisted 


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flares, we determined that air-assisted 

flares appeared to have the same 

operating envelope as the non-assisted 

and steam-assisted flares. Therefore, for 

air-assisted PEPO flares, we are 

proposing the use of the same equation 

that non-assisted and steam-assisted 

flares currently use to establish the flare 

tip velocity operating limit. We are also 

proposing that the owner or operator 

determine the flare tip velocity on a 15- 

minute block average basis. See section 

IV.D.1.e of this preamble for our 

rationale for proposing to use a 15- 

minute block averaging period for 

determining continuous compliance. 

Finally, we are proposing to exclude 

the provision for the special flare tip 

velocity equation in the general 

provisions at 40 CFR 63.11(b)(6)(i)(A) 

for non-assisted PEPO flares used to 

control gases with hydrogen content 

greater than 8 percent. This equation, 

which was developed based on limited 

data from a chemical manufacturer, has 

very limited applicability for flares used 

as APCDs in the PEPO Production 

source category because it only provides 

an alternative for non-assisted flares that 

are used to control gases with large 

quantities of hydrogen. Available data 

indicates that there are 18 flares in the 

PEPO Production source category; 

approximately 45 percent of these flares 

are either steam-assisted or air-assisted 

and 55 percent are non-assisted flares. 

Instead, we are proposing compliance 

alternatives that we believe provide a 

better way for PEPO flares combusting 

gases with high hydrogen content to 

comply with the rule while ensuring 

proper destruction performance of the 

flare (see section IV.D.1.d of this 

preamble for the proposed compliance 

alternatives). Therefore, for non-assisted 

PEPO flares used as APCDs for gases 

with hydrogen content greater than 8 

percent, we are proposing to exclude 

this special flare tip velocity equation as 

a compliance alternative. We request 

comment on the need to include this 

equation in the PEPO NESHAP. 

d. Net Heating Value of the Combustion 

Zone Gas 

The current provisions for flares in 40 

CFR 63.11(b) specify that the flare vent 

gas meet a minimum net heating value 

of 200 British thermal units per 

standard cubic foot (Btu/scf) for nonassisted flares and 300 Btu/scf for airand steam-assisted flares. The PEPO 

NESHAP references these provisions, 

but neither the general provisions nor 

the PEPO NESHAP includes specific 

requirements for monitoring the net 

heating value of the flare vent gas. 

Moreover, recent flare testing results 

indicate that meeting a minimum net 

heating value limit alone does not 

address instances when the flare may be 

over-assisted because it only considers 

the net heating value of the gas being 

combusted in the flare and does not 

consider other parameters (e.g., absence 

of assist media). However, many 

industrial flares use steam or air as an 

assist medium to protect the flare tip, 

promote turbulence for the mixing, 

induce air into the flame, and operate 

with no visible emissions. Using 

excessive steam or air results in dilution 

and cooling of flared gases and can lead 

to operating a flare outside its stable 

flame envelope, reducing the 

destruction efficiency of the flare. In 

extreme cases, over-steaming or excess 

aeration can snuff out a flame and allow 

regulated material to be released into 

the atmosphere without complete 

combustion. As previously noted in 

section IV.D.1.c of this preamble, 

because available data indicate that 

about half of all PEPO flares are either 

steam- or air-assisted, it is critical that 

we ensure that the determination of 

flare combustion efficiency account for 

assist media in some form. Recent flare 

test data have shown that the best way 

to account for situations of overassisting is to consider the gas mixture 

properties at the flare tip in the 

combustion zone when evaluating the 

ability to combust efficiently. As 

discussed in the introduction to this 

preamble section, the external peer 

review panel concurred with our 

assessment that the combustion zone 

properties at the flare tip are critical 

parameters to know in determining 

whether a flare will achieve good 

combustion. The general provisions, 

however, solely rely on the net heating 

value of the flare vent gas, and we have 

determined that that information is not 

sufficient for determining flare 

combustion efficiency of PEPO flares. 

In this proposal, in lieu of requiring 

compliance with the operating limits for 

net heating value of the flare vent gas 

specified in the general provisions, we 

are proposing to cross-reference 40 CFR 

part 63, subpart CC, to include in the 

PEPO NESHAP a single minimum 

operating limit for the net heating value 

in the combustion zone gas (NHVcz) of 

270 Btu/scf during any 15-minute 

period for steam-assisted, air-assisted, 

and non-assisted PEPO flares. Refer to 

40 CFR 63.1436 and 63.670(l) and (m) 

for these proposed provisions. The 

Agency believes, given the results from 

the various data analyses conducted for 

the Petroleum Refinery Sector rule, that 

this NHVcz operating limit promulgated 

for flares in the Petroleum Refinery 

Sector source category is also 

appropriate and reasonable and will 

ensure PEPO flares meet the HAP 

destruction efficiencies in the standard 

at all times when operated in concert 

with the other proposed flare provisions 

such as the pilot flame, visible 

emissions, and flare tip velocity 

requirements. See the documents titled 

Petroleum Refinery Sector Rule: 

Operating Limits for Flares and Flare 

Control Option Impacts for Final 

Refinery Sector Rule in Docket Item 

Nos. EPA–HQ–OAR–2010–0682–0206 

and EPA–HQ–OAR–2010–0682–0748, 

respectively). In addition, we are 

proposing that owners or operators may 

use a corrected heat content of 1,212 

Btu/scf for hydrogen, instead of 274 

Btu/scf, to demonstrate compliance with 

the NHVcz operating limit for PEPO 

flares; however, owners or operators 

who intend to use the corrected 

hydrogen heat content must have a 

system capable of monitoring for the 

hydrogen content in the flare vent gas. 

The EPA determined the 1,212 Btu/scf 

value based on a comparison between 

the lower flammability limit and net 

heating value of hydrogen compared to 

light organic compounds and we have 

used this value in several consent 

decrees issued by the EPA. Based on 

analyses conducted for the Petroleum 

Refinery Sector rule (see the document 

titled Flare Control Option Impacts for 

Final Refinery Sector in Docket Item No. 

EPA–HQ–OAR–2010–0682–0748), the 

EPA determined that using a 1,212 Btu/ 

scf value for hydrogen greatly improves 

the correlation between combustion 

efficiency and the combustion zone net 

heating value over the entire array of 

data. 

Furthermore, in addition to the 

NHVcz operating limit, we are 

proposing a net heating value dilution 

parameter (NHVdil) for certain PEPO 

flares that operate with perimeter assist 

air. Refer to 40 CFR 63.1436 and 

63.670(f) and (n) for these proposed 

provisions. For air-assisted flares, use of 

too much perimeter assist air can lead 

to poor flare performance. Furthermore, 

based on our analysis of the air-assisted 

flare datasets (see the document titled 

Petroleum Refinery Sector Rule: 

Operating Limits for Flares in Docket 

Item No. EPA–HQ–OAR–2010–0682– 

0206), we determined that a NHVdil of 

22 Btu/scf is necessary to ensure that 

there is enough combustible material 

available to adequately burn the gas and 

pass through the flammability region 

and also ensure that degradation of flare 

performance from excess aeration does 

not occur. We found that including the 

flow rate of perimeter assist air in the 

calculation of the NHVcz does not 


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identify all instances of excess aeration 

and could (in some instances) even 

allow facilities to send very dilute vent 

gases to the flare that would not 

combust (i.e., vent gases below their 

lower flammability limit could be sent 

to flare). Instead, the data suggest that 

the diameter of the flare tip, in concert 

with the amount of perimeter assist air 

(and other parameters used to determine 

NHVcz), provide the inputs necessary to 

calculate whether this type of flare is 

over-assisted. This dilution parameter is 

consistent with the combustion theory 

that the more time the gas spends in the 

flammability region above the flare tip, 

the more likely it will combust. Also, 

because both the volume of the 

combustion zone (represented by the 

diameter) and how quickly this gas is 

diluted to a point below the 

flammability region (represented by 

perimeter assist air flow rate) 

characterize this time duration, it is 

logical that we propose such a 

parameter. 

We also found that some assist steam 

lines are purposely designed to entrain 

air into the lower or upper steam at the 

flare tip; and for flare tips with an 

effective tip diameter of 9 inches or 

more, there are no flare tip steam 

induction designs that can entrain 

enough assist air to cause a flare 

operator to have a deviation from the 

NHVdil operating limit without first 

deviating from the NHVcz operating 

limit. Therefore, we are proposing to 

allow owners or operators of PEPO 

flares that only use perimeter assist air 

entrained in lower and upper steam at 

the flare tip and that have a flare tip 

diameter of 9 inches or greater to 

comply only with the NHVcz operating 

limit. Steam-assisted flares with 

perimeter assist air and an effective tip 

diameter of less than 9 inches would 

remain subject to the requirement to 

account for the amount of assist air 

intentionally entrained within the 

calculation of NHVdil. However, we 

recognize that owners or operators 

cannot directly measure this assist air, 

but the quantity of air entrained is 

dependent on the assist steam rate and 

the design of the steam tube’s air 

entrainment system. Therefore, we are 

proposing provisions to specify that 

owners or operators of these smaller 

diameter steam-assisted PEPO flares use 

the steam flow rate and the maximum 

design air-to-steam ratio of the steam 

tube’s air entrainment system for 

determining the flow rate of this assist 

air. Using the maximum design ratio 

will tend to over-estimate the assist air 

flow rate, which is conservative with 

respect to ensuring compliance with the 

NHVdil operating limit. 

Finally, we are proposing that owners 

or operators record and calculate 15- 

minute block average values for these 

parameters. Section IV.D.1.e of this 

preamble provides our rationale for 

selecting a 15-minute block averaging 

period. We solicit comments on the 

proposed revisions related to NHVcz. 

e. Data Averaging Periods for Flare Gas 

Operating Limits 

Except for the visible emissions 

operating limits described in section 

IV.D.1.b of this preamble, we are 

proposing to use a 15-minute block 

averaging period for each proposed flare 

operating parameter (i.e., presence of a 

pilot flame, flare tip velocity, and 

NHVcz) to ensure that PEPO flares 

operate within the appropriate operating 

conditions. We consider a 15-minute 

averaging time to be the most 

appropriate for assessing proper flare 

performance because flare vent gas flow 

rates and composition can change 

significantly over short periods of time. 

Furthermore, because destruction 

efficiency can fall precipitously when a 

flare is controlling vent gases below (or 

outside) the proposed operating limits, 

short time periods where the operating 

limits are not met could seriously 

decrease the overall performance of the 

flare. Refer to the Petroleum Refinery 

Sector rule preambles (79 FR 36880 and 

80 FR 75178) for further details 

supporting why we believe a 15-minute 

averaging period is appropriate. 

Given the short averaging times for 

the operating limits, we are proposing 

calculation methodologies to enable 

owners or operators to use ‘‘feed 

forward’’ calculations to ensure 

compliance with the operating limits on 

a 15-minute block average for PEPO 

flares. Specifically, we propose using 

the results of the compositional analysis 

determined just prior to a 15-minute 

block period for the next 15-minute 

block average. Owners or operators of 

PEPO flares will then know the vent gas 

properties for the upcoming 15-minute 

block period and can adjust assist gas 

flow rates relative to vent gas flow rates 

to comply with the proposed operating 

limits. In other words, ‘‘feed forward’’ 

means that owners or operators would 

use the net heating value in the vent gas 

(NHVvg) going into the flare in one 15- 

minute period to adjust the assist media 

(i.e., steam or air) and/or the 

supplemental gas in the next 15-minute 

period, as necessary, to calculate an 

NHVcz limit of 270 Btu/scf or greater 

using the proposed equation. We 

recognize that when a subsequent 

measurement value is determined, the 

instantaneous NHVcz based on that 

compositional analysis and the flow 

rates that exist at the time may not be 

above 270 Btu/scf. We are proposing 

that this is not a violation of the 

operating limit. Rather, we are 

proposing that the owner or operator is 

only required to make operational 

adjustments based on that information 

to achieve, at a minimum, the net 

heating value limit for the subsequent 

15-minute block average. We are, 

however, proposing that failure to adjust 

the assist media or supplemental natural 

gas using the NHVvg from the previous 

period in the equation provided for 

calculating an NHVcz limit of 270 Btu/ 

scf would be a violation of the operating 

limit. Alternatively, because the owner 

or operator could directly measure the 

NHVvg on a more frequent basis, such 

as with a calorimeter (and optional 

hydrogen analyzer), the process control 

system is able to adjust more quickly, 

and the owner or operator can adjust the 

assist media or supplemental natural gas 

more quickly. In this manner, the owner 

or operator is not limited by relying on 

NHVvg data that may not represent the 

current conditions. We are, therefore, 

also proposing that the owner or 

operator may opt to use the NHVvg in 

such instances from the same period to 

comply with the operating limit. For 

examples of ‘‘feed forward’’ 

calculations, see attachment 3 of the 

document titled Flare Control Option 

Impacts for Final Refinery Sector Rule 

in Docket Item No. EPA–HQ–OAR– 

2010–0682–0748. 

We are also proposing to clarify that 

when determining compliance with the 

flare tip velocity and combustion zone 

operating limits specified in 40 CFR 

63.670(d) and (e), the initial 15-minute 

block period starts with the 15-minute 

block that includes a full 15 minutes of 

the flaring event. In other words, we are 

proposing to clarify that the owner or 

operator demonstrate compliance with 

the velocity and NHVcz requirements 

starting with the block that contains the 

fifteenth minute of a flaring event; and 

the owner or operator is not required to 

demonstrate compliance for the 

previous 15-minute block in which the 

event started and contained only a 

fraction of flow. We solicit comments on 

these proposed revisions. 

f. Flares in Dedicated Service 

In lieu of the requirement that owners 

or operators continuously monitor the 

composition of the vent gas and the 

NHVvg, we are proposing an alternative 

monitoring approach for PEPO flares in 

dedicated service where the flare vent 

gas has consistent composition and 

flow. We believe that these flares do not 


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need to have the same type of ongoing 

monitoring requirements as those with 

more variable waste streams. Thus, we 

are proposing an option that owners or 

operators can use to demonstrate 

compliance with the operating 

requirements for PEPO flares that are in 

dedicated service to a specific emission 

source, such as a transfer rack operation 

consistently loading the same material. 

We are proposing that owners or 

operators submit an application to the 

Administrator to allow the use of this 

alternative compliance option. We are 

proposing that the application include a 

description of the system, 

characterization of the vent gases that 

could be routed to the flare based on a 

minimum of 7 grab samples (14 daily 

grab samples for continuously operated 

flares), and specification of the net 

heating value that will be used for all 

flaring events (based on the minimum 

net heating value of the grab samples). 

In other words, for PEPO flares that are 

in dedicated service, we are proposing 

that owners or operators could use the 

minimum NHVvg determined from the 

grab samples in the equation at 40 CFR 

63.670(m)(1) for all flaring events to 

determine NHVcz. We are also 

proposing to allow engineering 

estimates to characterize the amount of 

gas flared and the amount of assist gas 

introduced into the system. For 

example, we believe that the use of fan 

curves to estimate air assist rates would 

be acceptable. We propose that flare 

owners or operators would use the net 

heating value determined from the 

initial sampling phase and measured or 

estimated flare vent gas and assist gas 

flow rates, if applicable, to demonstrate 

compliance with the standards. Refer to 

40 CFR 63.1436 and 63.670(j)(6) for 

these proposed provisions. Finally, for 

owners and operators that must comply 

with the continuous monitoring 

requirements, we are proposing 

additional clarifications and 

requirements at 40 CFR 63.1436 when 

using a gas chromatograph or mass 

spectrometer for compositional analysis. 

We solicit comments on the proposed 

revisions related to flares in dedicated 

service. 

g. Impacts of the Proposed Flare 

Operating and Monitoring Requirements 

The EPA expects that the 

requirements for flares used as APCDs 

in the PEPO Production source category 

discussed in this section will affect all 

flares at PEPO processes. As previously 

mentioned, based on facility responses 

to our CAA section 114 request (see 

section II.C of this preamble), we 

estimate that there are 18 flares of 

traditional elevated flare tip designs 

(e.g., steam-assisted, air-assisted, and 

non-assisted flare tips). The EPA 

estimated the costs for each flare for a 

given facility, considering current 

monitoring systems already installed on 

each individual flare. Given that the 

same type of equipment is used for 

flares in the PEPO Production source 

category and for the petroleum refinery 

sector, we estimated the costs for any 

additional monitoring systems needed 

based on installed costs received from 

petroleum refineries and, if installed 

costs were unavailable, we based the 

cost estimates on vendor-purchased 

equipment. The EPA estimated the 

baseline emissions and the emission 

reductions achieved by the proposed 

rule based on current vent gas and 

steam flow data submitted by industry 

representatives. We note that the 

requirements for PEPO flares that we are 

proposing will ensure compliance with 

the MACT standards in the PEPO 

NESHAP when flares are used as an 

APCD. Because we are not changing the 

underlying MACT standards in the 

PEPO NESHAP, we did not include any 

of the estimated excess emissions from 

flares in the summary of total estimated 

emissions reductions for this action. 

However, we estimate that the proposed 

operational and monitoring 

requirements have the potential to 

reduce excess emissions from PEPO 

flares by approximately 75 tpy of HAP 

and 281 tpy of VOC (i.e., non-methane, 

non-ethane total hydrocarbons). 

According to the emissions inventory 

file we used to assess residual risk (see 

section IV.C.1 of this preamble), there 

are 10 individual HAP compounds 

included in the emissions inventory for 

PEPO flares, including propylene oxide, 

EtO, toluene, glycol ethers, and hexane. 

For more detail on the impact estimates, 

see the document titled Control Option 

Impacts for Flares in the PEPO 

Production Source Category that Control 

Emissions from Processes Subject to the 

PEPO NESHAP, which is available in 

the docket for this rulemaking. 

2. Closed Vent System Containing 

Bypass Lines 

For a closed vent system containing 

bypass lines that can divert the stream 

away from the APCD to the atmosphere, 

the PEPO NESHAP requires the owner 

or operator to either: (1) install, 

maintain, and operate a continuous 

parametric monitoring system for flow 

on the bypass line that is capable of 

detecting whether a vent stream flow is 

present at least once every 15 minutes, 

or (2) secure the bypass line valve in the 

non-diverting position with a car-seal or 

a lock-and-key type configuration. 

Under option 2, the PEPO NESHAP also 

requires owners or operators to inspect 

the seal or closure mechanism at least 

once per month to verify the valve is 

maintained in the non-diverting 

position (see 40 CFR 63.1429(c)(2) for 

more details). To expressly prohibit 

bypassing an APCD at affected sources, 

as implied by option 2, we are 

proposing that an owner or operator 

may not bypass the APCD at any time 

and that a bypass is a violation (see 

proposed 40 CFR 63.1429(c)(3)), and 

owners and operators must estimate, 

maintain records, and report the 

quantity of organic HAP released (see 

proposed 40 CFR 63.1430(d)(6) and 

(h)(7)). These proposed requirements are 

also being proposed at 40 CFR 

63.1425(f), by reference to 40 CFR 

63.114(d)(2) and (3) and 63.118(a)(5) 

and (f)(7), for process vents in a PMPU 

that use THF to produce one or more 

PEPO products. We are proposing these 

revisions to ensure continuous 

compliance with the MACT standards, 

consistent with Sierra Club v. EPA, 551 

F.3d 1019 (D.C. Cir. 2008) (where the 

Court determined that standards under 

CAA section 112(d) must provide for 

compliance at all times), because 

bypassing an APCD could result in a 

release of regulated organic HAP to the 

atmosphere that would be required to be 

controlled under the existing MACT 

standards in the PEPO NESHAP. We are 

also proposing that the use of a cap, 

blind flange, plug, or second valve on 

open-ended valves or lines (following 

the requirements specified in 40 CFR 

60.482–6(a)(2), (b), and (c) or following 

requirements codified in another 

regulation that are the same as 40 CFR 

60.482–6(a)(2), (b), and (c)) is sufficient 

to prevent a bypass. We solicit 

comments on these proposed revisions. 

3. Maintenance Activities 

In the 2014 final rule (79 FR 17340, 

March 27, 2014), we removed the 

exemption from emissions standards for 

periods of SSM in accordance with a 

decision of the United States Court of 

Appeals for the District of Columbia 

Circuit, Sierra Club v. EPA, 551 F.3d 

1019 (D.C. Cir. 2008), cert. denied, 130 

S. Ct. 1735 (U.S. 2010). This decision 

stated that the EPA must have standards 

in place at all times, even during 

periods of SSM. As a result, the process 

vent and storage vessel provisions (as 

well as other provisions) in the PEPO 

NESHAP apply at all times. Although 

the EPA eliminated the SSM exemption 

from the PEPO NESHAP in 2014, we 

recognize that owners or operators 

periodically discharge vent streams 

during certain maintenance activities, 

such as those that require equipment 

openings, and we consider maintenance 


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activities a separate class of startup and 

shutdown emissions because there must 

be a point in time when the equipment 

can be opened, and any remaining 

emissions vented to the atmosphere. We 

also acknowledge that it would require 

a significant effort to identify and 

characterize each of these potential 

release points (e.g., for permitting 

purposes). Therefore, we are proposing 

to establish MACT standards for 

maintenance activities (i.e., equipment 

openings, storage vessel degassing, and 

periods of planned routine maintenance 

of the emission control system for the 

vent on a fixed roof tank at a new or 

existing affected source). CAA section 

112(h)(1) states that the Administrator 

may prescribe a work practice standard 

or other requirements, consistent with 

the provisions of CAA section 112(d) or 

(f), in those cases where, in the 

judgment of the Administrator, it is not 

feasible to enforce an emission standard. 

We are proposing work practices instead 

of numeric emission limits for 

maintenance activities because it is ‘‘not 

feasible to prescribe or enforce an 

emission standard’’ for these emissions. 

Emissions from maintenance activities 

are not ‘‘emitted through a conveyance 

designed and constructed to emit or 

capture such pollutant’’ (see CAA 

section 112(h)(2)(A)) and it is not 

possible to characterize each of these 

potential release points. 

a. Equipment Openings (Excluding 

Storage Vessel Degassing) 

To determine what MACT standards 

should be established for equipment 

openings, we reviewed State permit 

conditions and determined that the air 

emissions permits for the best 

performers specify that owners or 

operators meet certain conditions before 

they open equipment to the atmosphere. 

The conditions include thresholds 

regarding the lower explosive limit 

(LEL) and the amount of gas that may be 

emitted. Based on our review of these 

permits, we have determined that a 

work practice standard that allows 

opening process equipment to the 

atmosphere during maintenance events 

only after meeting certain conditions (as 

specified in this section IV.D.3.a of the 

preamble) represents the MACT floor 

level of control for equipment openings 

at new and existing affected sources. 

Therefore, we are proposing a work 

practice standard at 40 CFR 

63.1425(h)(1)(i) to specify that, prior to 

opening process equipment to the 

atmosphere during maintenance events, 

owners or operators must first drain the 

equipment before purging to a closed 

vent system so that the concentration of 

the vapor in the equipment served by 

the maintenance vent is less than or 

equal to 10 percent of the LEL. For those 

situations where owners or operators 

cannot demonstrate 10-percent LEL, we 

are proposing at 40 CFR 

63.1425(h)(1)(ii) that owners or 

operators may open and vent the 

equipment to the atmosphere if the 

pressure is less than or equal to 5 

pounds per square inch gauge (psig), 

provided that owners or operators do 

not actively purge the equipment to the 

atmosphere until meeting the LEL 

criterion. We are proposing this 5-psig 

threshold to acknowledge that a certain 

minimum pressure must exist for the 

flare header system (or other similar 

control system) to operate properly. We 

are also proposing at 40 CFR 

63.1425(h)(1)(iii) that owners or 

operators can open equipment when the 

amount of VOC contained in the 

equipment is less than 50 pounds. 

These proposed work practice standards 

are also being proposed at 40 CFR 

63.1425(f), by reference to 40 CFR 

63.113(k), for maintenance vents in a 

PMPU that use THF to produce one or 

more PEPO products. 

We acknowledge that installing a 

blind flange to prepare equipment for 

maintenance may be necessary and that 

by doing so, the owner or operator may 

not be able to meet the proposed 

maintenance vent conditions mentioned 

earlier in this section (e.g., a valve used 

to isolate the equipment will not seat 

fully, so organic material may 

continually leak into the isolated 

equipment). To limit the emissions 

during the blind flange installation, we 

are proposing at 40 CFR 

63.1425(h)(1)(iv) depressurizing the 

equipment to 2 psig or less prior to 

equipment opening and maintaining 

pressure of the equipment where purge 

gas enters the equipment at or below 2 

psig during the blind flange installation. 

The low allowable pressure limit will 

reduce the amount of process gas 

released during the initial equipment 

opening, and the ongoing 2 psig 

pressure requirement will limit the 

purge gas rate. Together, these proposed 

provisions will limit the emissions 

during blind flange installation and will 

result in comparable emissions allowed 

under the proposed maintenance vent 

conditions mentioned earlier in this 

section. We expect these situations to be 

rare and expect that the owner or 

operator would remedy the situation as 

soon as practical (e.g., replace the 

isolation valve or valve seat during the 

next turnaround in the example 

provided earlier in this paragraph). 

Therefore, we are only proposing that 

owners or operators use this alternative 

maintenance vent limit under those 

situations where the proposed primary 

limits (i.e., the concentration of the 

vapor in the equipment served by the 

maintenance vent is less than or equal 

to 10 percent of the LEL, pressure is less 

than or equal to 5 psig, or VOC is less 

than 50 pounds) are not achievable and 

blinding of the equipment is necessary. 

We did not identify any additional 

options beyond those identified here 

(i.e., beyond-the-floor options) for 

controlling emissions from equipment 

openings. 

To demonstrate compliance with the 

proposed equipment opening work 

practice standards, we are proposing at 

40 CFR 63.1430(a) that owners and 

operators must keep standard site 

procedures used to deinventory 

equipment for safety purposes (e.g., hot 

work or vessel entry procedures), as 

well the following additional records (as 

applicable): 

• The concentration of the vapor at 

the time of the vessel opening exceeds 

10 percent of its LEL, identification of 

the maintenance vent, the process units 

or equipment associated with the 

maintenance vent, the date of 

maintenance vent opening, and the 

concentration of the vapor at the time of 

the vessel opening; 

• Either the vessel pressure at the 

time of the vessel opening exceeds 5 

psig or the concentration of the vapor at 

the time of the active purging was 

initiated exceeds 10 percent of its LEL, 

identification of the maintenance vent, 

the process units or equipment 

associated with the maintenance vent, 

the date of maintenance vent opening, 

the pressure of the vessel or equipment 

at the time of discharge to the 

atmosphere and, if applicable, the 

concentration of the vapors in the 

equipment when active purging was 

initiated; 

• Records of the estimating 

procedures used to determine the total 

quantity of VOC in the equipment and 

the type and size limits of equipment 

that contain less than 50 pounds of VOC 

at the time of maintenance vent 

opening; 

• For each maintenance vent opening 

that contains greater than 50 pounds of 

VOC for which the deinventory 

procedures are not followed or for 

which the equipment opened exceeds 

the type and size limits established in 

the records, records that identify the 

maintenance vent, the process units or 

equipment associated with the 

maintenance vent, the date of 

maintenance vent opening, and records 

used to estimate the total quantity of 

VOC in the equipment at the time the 


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Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 106035 

69See 30 Texas Administrative Code Chapter 115, 

Subchapter F, Division 3, available at https:// 

texreg.sos.state.tx.us/public/ 

readtac%24ext.ViewTAC?tac_view=5&

ti=30&pt=1&ch=115&sch=F&div=3&rl=Y. 

70See https://www.tceq.texas.gov/assets/public/ 

permitting/air/Guidance/NewSourceReview/mss/ 

chem-mssdraftconditions.pdf. 

71See http://www.aqmd.gov/docs/default-source/ 

rule-book/reg-xi/rule-1149.pdf. 

maintenance vent was opened to the 

atmosphere; and 

• Identification of the maintenance 

vent, the process units or equipment 

associated with the maintenance vent, 

records documenting actions taken to 

comply with other applicable 

alternatives and why utilization of this 

alternative was required, the date of 

maintenance vent opening, the 

equipment pressure and concentration 

of the vapors in the equipment at the 

time of discharge, an indication of 

whether active purging was performed 

and the pressure of the equipment 

during the installation or removal of the 

blind if active purging was used, the 

duration the maintenance vent was 

open during the blind installation or 

removal process, and records used to 

estimate the total quantity of VOC in the 

equipment at the time the maintenance 

vent was opened to the atmosphere for 

each applicable maintenance vent 

opening. 

For any maintenance vent release 

exceeding the proposed applicable 

limits (e.g., the maintenance vent 

release is greater than 10 percent of the 

LEL), we are proposing that the owner 

or operator include in the next periodic 

report: (1) identification of the 

maintenance vent and the equipment 

served by the maintenance vent; (2) the 

date and time the maintenance vent was 

opened to the atmosphere; (3) the LEL 

in percent, vessel pressure in psig, or 

mass in pounds of VOC in the 

equipment, as applicable, at the start of 

atmospheric venting, and if the 5 psig 

vessel pressure option was used and 

active purging was initiated while the 

concentration of the vapor was 10 

percent or greater of its LEL, also 

include the concentration of the vapors 

at the time active purging was initiated; 

and (4) an estimate of the mass in 

pounds of organic HAP released during 

the entire atmospheric venting event. 

We solicit comments on the proposed 

revisions related to maintenance 

activities. For additional details and 

discussion, see the document titled 

Review of Regulatory Alternatives for 

Certain Vent Streams in the PEPO 

Production Source Category that are 

Associated with Processes Subject to the 

PEPO NESHAP, which is available in 

the docket for this rulemaking. 

b. Storage Vessel Degassing 

The PEPO NESHAP does not 

currently contain a standard specific to 

storage vessel degassing when storage 

vessels are using control devices to 

comply with the requirements in 40 

CFR 63.119(a)(2) (via reference by 40 

CFR 63.1432). We acknowledge that 

storage vessel degassing is similar to 

maintenance vents (e.g., equipment 

openings) and that there must be a point 

in time when the owner or operator can 

open the storage vessel and vent any 

remaining gas into the atmosphere. 

Therefore, to determine what MACT 

standards should be established for 

storage vessel degassing operations, we 

reviewed available data to determine 

how the best performers are controlling 

storage vessel degassing emissions. 

We identified three regulations that 

address emissions from storage vessel 

degassing: two in Texas and one in 

California. The Texas Administrative 

Code 69 specifies degassing provisions 

and TCEQ implements those provisions 

through operating permit conditions.70

In California, the South Coast Air 

Quality Management District 

(SCAQMD) specifies degassing 

requirements in their Rule 1149.71

The Texas Administrative Code 

requirements are the least stringent and 

require control of degassing emissions 

until the vapor space concentration is 

less than 35,000 ppmv as methane or 50 

percent of the LEL. The TCEQ permit 

conditions require control of degassing 

emissions until the vapor space 

concentration is less than 10 percent of 

the LEL or until the VOC concentration 

is less than 10,000 ppmv, and SCAQMD 

Rule 1149 requires control of degassing 

emissions until the vapor space 

concentration is less than 5,000 ppmv as 

methane. The EPA considers the TCEQ 

permit conditions to be equivalent to 

SCAQMD Rule 1149 control 

requirements because 5,000 ppmv as 

methane equals 10 percent of the LEL 

for methane. 

Currently, 8 of the 25 existing PEPO 

facilities are located in Texas and 

subject to the TCEQ permit conditions; 

however, no PEPO facilities are located 

in California and subject to the 

SCAQMD rule. Therefore, the TCEQ 

permit conditions relying on storage 

vessel degassing until 10 percent of the 

LEL is achieved reflect what the best 

performers have implemented for 

storage vessel degassing. 

We reviewed TCEQ operating permit 

condition 6 (applicable to floating roof 

storage vessels) and permit condition 7 

(applicable to fixed roof storage vessels) 

for key information that we could 

implement to form the basis of a 

standard for storage vessel degassing. 

The TCEQ operating permit conditions 

require control of degassing emissions 

for floating roof and fixed roof storage 

vessels until the vapor space 

concentration is less than 10 percent of 

the LEL and the owner or operator has 

removed all the standing liquid from the 

vessel to the extent practicable. The 

permit conditions also specify that 

facilities have the option of degassing a 

storage vessel until reaching a VOC 

concentration of 10,000 ppmv. 

We do not consider the 10,000 ppmv 

concentration cutoff option in the TCEQ 

permit conditions to be equivalent to or 

as stringent as the compliance option to 

meet 10 percent of the LEL. Therefore, 

we are not proposing the 10,000 ppmv 

concentration as a compliance option. 

We also do not expect that the best 

performers would use this concentration 

for compliance because the TCEQ 

permit conditions allow facilities to 

calibrate their LEL monitor using 

methane. 

Based on review of this information, 

we are proposing that the TCEQ 

requirements to reduce the vapor space 

concentration to less than 10 percent of 

the LEL and to remove all the standing 

liquid from the vessel to the extent 

practicable reflect the MACT floor for 

both new and existing PEPO sources. 

We did not identify any additional 

options beyond this (i.e., beyond-thefloor options) for controlling emissions 

from storage vessel degassing. 

Therefore, we are proposing these 

requirements at 40 CFR 63.1432(a) by 

reference to 40 CFR 63.119(a)(6). 

However, because we recognize that in 

some cases (e.g., use of an inert blanket) 

the storage vessel atmosphere would not 

have an LEL, the EPA is also proposing 

an organic HAP concentration cutoff of 

5,000 ppmv (measured as methane) as 

an equivalent alternative to reducing the 

vapor space concentration to less than 

10 percent of the LEL. These are 

considered equivalent because 5,000 

ppmv as methane equals 10 percent of 

the LEL for methane. 

Additionally, in petitions for 

reconsideration that the EPA recently 

received on the MON, EMACT 

standards, Petroleum Refinery Sector 

rule, and OLD NESHAP, petitioners 

asserted that it is necessary to make 

connections to a temporary control 

device to control the degassing 

emissions from floating roof storage 

vessels, which may require opening the 

storage vessel to make these 

connections. Therefore, we are 

proposing that owners or operators may 

open a floating roof storage vessel prior 

to degassing to set up equipment (i.e., 

make connections to a temporary 


jspears on DSK121TN23PROD with PROPOSALS
106036 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

72Compilation of Air Pollutant Emission Factors. 

Volume 1: Stationary Point and Area Sources. AP– 

42, Fifth Edition. Chapter 7: Liquid Storage Tanks. 

OAQPS, Research Triangle Park, NC. 

control device), but owners or operators 

must use this approach in a limited 

manner and must not actively purge the 

storage vessel while making 

connections. 

We estimated the emissions 

reductions that would result from this 

proposed change to the PEPO NESHAP 

by evaluating the population of storage 

vessels that are subject to control under 

40 CFR 63.119(a)(2) (by reference in 40 

CFR 63.1432) and not located in Texas. 

Storage vessels regulated by the PEPO 

NESHAP in Texas are already subject to 

the degassing requirements; therefore, 

those PEPO facilities would not achieve 

additional emissions reductions. 

Additionally, the PEPO facility that is 

owned by a small business also has 

processes subject to the HON, and the 

impacts of such degassing requirements 

on the facility were already accounted 

for under the recent HON rulemaking 

(see 89 FR 42932). Based on a review of 

facility responses to our CAA section 

114 request (see section II.C of this 

preamble), owners or operators degas 

most storage vessels an average of once 

every 11 years. Using this average, and 

the population of PEPO storage vessels 

that are not in Texas (15 vessels) based 

on the assumption of one Group 1 

storage vessel per non-Texas facility, we 

estimated that one storage vessel 

degassing event would be newly subject 

to control each year. Controlling PEPO 

storage vessel degassing would reduce 

HAP emissions by 0.87 tpy. See the 

document titled Degassing Cost and 

Emissions Impacts for Storage Vessels 

Located in the PEPO Production Source 

Category that are Associated with 

Processes Subject to the PEPO NESHAP, 

which is available in the docket for this 

rulemaking, for details on the 

assumptions and methodologies used in 

this analysis. 

c. Planned Routine Maintenance for 

Storage Vessel Control Devices 

Although the PEPO NESHAP 

currently allows owners and operators 

to disconnect the fixed roof storage 

vessel vent from the closed vent system 

and control device, fuel gas system, or 

process equipment for up to 240 hours 

per year during planned, routine 

maintenance (see 40 CFR 63.119(e)(3) 

through (5) (by reference in 40 CFR 

63.1432)), we are proposing at 40 CFR 

64.1432(a) by reference to 40 CFR 

63.119(e)(7) that owners and operators 

would not be allowed to fill the storage 

vessel during these periods (such that 

the vessel would emit HAP to the 

atmosphere for a limited amount of time 

due to breathing losses only). Our 

proposal is based on our review of other 

chemical sector NESHAP (HON, P&R I 

NESHAP, and Group II Polymers and 

Resins (P&R II) NESHAP (89 FR 42932, 

May 16, 2024)) where we have 

determined that a work practice 

standard that allows owners and 

operators up to 240 hours per year 

during planned routine maintenance of 

the emission control system, provided 

that there are no working losses from 

the vessel, represents the MACT floor 

level of control for fixed roof storage 

vessel vents at new and existing affected 

sources. We expect PEPO sources are 

using these same types of practices to 

limit emissions, so we are proposing 

that this work practice represents the 

MACT floor level of control for fixed 

roof storage vessel vents at new and 

existing sources. However, if these 

processes are currently uncontrolled, 

the cost effectiveness of this work 

practice ($2,250 per ton of HAP 

reduced), minimal energy requirements, 

and limited non-air quality health and 

environmental impacts would likely 

result in the EPA establishing beyondthe-floor requirements based on the 

same practice. These proposed 

requirements ensure that a CAA section 

112 standard is in place at all times, 

given that all working loss emissions 

from fixed roof storage vessels would be 

controlled during these periods of 

planned routine maintenance of the 

emission control system, thus satisfying 

Sierra Club v. EPA, 551 F.3d 1019 (D.C. 

Cir. 2008). 

We estimated the emissions 

reductions that would result from this 

proposed change to the PEPO NESHAP. 

We assumed that owners and operators 

would install a secondary control device 

system (to control emissions from 

vessels during periods of planned 

routine maintenance of the primary 

control device) and that owners and 

operators would choose activated 

carbon canisters as the method of 

control. Based on the facility responses 

to our CAA section 114 request (see 

section II.C of this preamble), we 

identified one facility that operates one 

Group 1 fixed roof storage vessel subject 

to controls according to table 3 to the 

PEPO NESHAP. We were also able to 

determine from an air permit review 

that another PEPO facility (i.e., one that 

did not receive our CAA section 114 

request) does not have any Group 1 

storage vessels subject to controls 

according to table 3 to the PEPO 

NESHAP. Furthermore, we determined 

that one facility is a small business that 

is co-located with a HON facility, and 

already accounted for under the recent 

HON rulemaking (see 89 FR 42932). 

Using all of this information, we then 

extrapolated and estimated that the total 

number of Group 1 fixed roof storage 

vessels subject to the PEPO NESHAP 

nationwide is 15, assuming one vessel 

per facility. We then estimated that the 

highest amount of HAP emissions that 

would be expected to occur from a 

PEPO fixed roof storage vessel during 

the 240 hours of planned routine 

maintenance would be 262 pounds, if 

the emissions are not controlled. This 

emissions estimate includes 19.3 

pounds of breathing losses and 243 

pounds of working losses. We based 

these emissions on the average vessel 

capacity and average vapor pressure 

material stored in a vessel reported (for 

all HON and PEPO fixed roof storage 

vessels) in response to our CAA section 

114 request, and we estimated using the 

emission estimation procedures from 

chapter 7 of the EPA’s Compilation of 

Air Pollutant Emission Factors.72 We 

assumed that activated carbon canisters 

would achieve a 95 percent reduction in 

HAP emissions, which would reduce 

emissions per vessel by 230 pounds of 

HAP per year of working loss emissions. 

As a beyond-the-floor control option, 

we considered requiring owners and 

operators to also control breathing 

losses from storage vessels during 

periods of planned routine maintenance 

of the emission control system. 

However, we concluded that this option 

would not be cost effective because we 

estimated it would cost $28,360 per ton 

of HAP reduced. 

See the document titled Cost and 

Emissions Impacts for 240-Hour 

Planned Routine Maintenance Work 

Practice Standard on Storage Vessels 

Located in the PEPO Production Source 

Category that are Associated with 

Processes Subject to the PEPO NESHAP, 

which is available in the docket for this 

rulemaking, for details on the 

assumptions and methodologies used in 

this analysis. 

4. Pressure Vessels 

We are proposing to establish separate 

MACT standards for pressure vessels 

that are associated with processes 

subject to the PEPO NESHAP. The rule 

does not currently regulate HAP 

emissions from pressure vessels. The 

EPA is proposing to define ‘‘pressure 

vessel’’ at 40 CFR 63.1423(a) (by 

reference to 40 CFR 63.101) to mean ‘‘a 

storage vessel that is used to store 

liquids or gases and is designed not to 

vent to the atmosphere as a result of 

compression of the vapor headspace in 

the pressure vessel during filling of the 


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Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 106037 

73Except for connectors in EtO service, gas/vapor 

or light liquid valves in EtO service, light liquid 

pumps in EtO service, and except for equipment 

that meet the unsafe-to-monitor or difficult-tomonitor criteria specified in 40 CFR 63.168(h) and 

(i) (for valves in gas/vapor service and in light 

liquid service) and in 40 CFR 63.174(f) and (h) (for 

connectors in gas/vapor service and in light liquid 

service). 

74Randall, 2012. Memorandum from Randall, D., 

RTI International, to Parsons, N., EPA/OAQPS. 

Survey of Control Technology for Storage Vessels 

and Analysis of Impacts for Storage Vessel Control 

Options. January 20, 2012. EPA Docket No. EPA– 

HQ–OAR–2010–0871. 

pressure vessel to its design capacity.’’ 

To eliminate any ambiguity in 

applicability or control requirements, 

the EPA is also proposing at 40 CFR 

63.1423(b) to remove the exemption for 

‘‘pressure vessels designed to operate in 

excess of 204.9 kilopascals and without 

emissions to the atmosphere’’ from the 

definition of storage vessel. This 

longstanding exemption is ambiguous 

with respect to what ‘‘without emissions 

to the atmosphere’’ means. For example, 

most pressure vessels have relief 

devices that allow for venting when 

pressure exceeds setpoints. In many 

cases, these vents are routed to control 

devices; however, control devices are 

not completely effective (e.g., they may 

achieve only 98-percent control), and 

therefore pressure vessels are sources of 

emissions to the atmosphere, even if 

they are controlled. There are also 

instances where other components in 

pressure systems may allow for fugitive 

releases because of leaks from fittings or 

cooling systems. All of these events 

arguably are ‘‘emissions to the 

atmosphere,’’ and it is likely that even 

if the PEPO NESHAP maintained this 

exemption, owners and operators of 

pressure vessels would still have 

uncertainty regarding whether or not 

they were subject to substantive 

requirements. Therefore, the proposed 

revisions remove the ambiguity 

associated with the exemption and set 

new MACT standards intended to limit 

emissions to the atmosphere from 

pressure vessels at new and existing 

affected sources. We are also clarifying 

in the definition of PMPU at 40 CFR 

63.1423(b) that the collection of 

equipment that is part of a PMPU 

includes pressure vessels. 

We are proposing LDAR requirements 

at 40 CFR 63.1432(a) by reference to 40 

CFR 63.119(a)(7) that are based on 

similar no-detectable emission 

requirements required for closed vent 

systems in most chemical sector 

NESHAP. These proposed requirements, 

which apply to each point on the 

pressure vessel through which total 

organic HAP could potentially be 

emitted,73 are consistent with CAA 

section 112(d) controls and reflect the 

MACT floor at new and existing affected 

sources. We did not identify any 

additional options beyond this (i.e., 

beyond-the-floor options) for controlling 

emissions from pressure vessels. As 

such, these proposed requirements 

impose a standard that requires no 

detectable emissions at all times (i.e., 

the proposed standard would require 

owners and operators to meet a leak 

definition of 500 ppmv at each point on 

the pressure vessel where total organic 

HAP could potentially be emitted); 

require initial and annual leak 

monitoring using EPA Method 21 of 40 

CFR part 60, appendix A–7; and require 

routing organic HAP through a closed 

vent system to a control device (i.e., no 

releases to the atmosphere through any 

points on the pressure vessel). These 

proposed LDAR requirements exclude 

connectors in EtO service, gas/vapor or 

light liquid valves in EtO service, and 

light liquid pumps in EtO service 

because those would be subject to more 

stringent LDAR requirements under the 

proposed EtO equipment leak standards. 

We estimated the emissions 

reductions that would result from this 

proposed change to the PEPO NESHAP. 

Based on facility responses to our CAA 

section 114 request (see section II.C of 

this preamble) and an air permit review 

of PEPO facilities, we estimated that 

there are 15 pressure vessels located at 

PEPO facilities. Using information from 

a 2012 analysis that identified 

developments for storage vessels at 

chemical manufacturing facilities and 

petroleum refineries,74 we estimate a 

total HAP emission reduction of 1.5 tpy 

for all affected pressure vessels 

associated with processes subject to the 

PEPO NESHAP. See the document titled 

Cost and Emissions Impacts for Pressure 

Vessels Located in the PEPO Production 

Source Category that are Associated 

with Processes Subject to the PEPO 

NESHAP, which is available in the 

docket for this rulemaking, for details 

on the assumptions and methodologies 

used in this analysis. We solicit 

comments on the proposed revisions for 

pressure vessels. 

5. Surge Control Vessels and Bottoms 

Receivers 

The PEPO NESHAP, via reference to 

40 CFR part 63, subpart H, defines a 

surge control vessel to mean feed 

drums, recycle drums, and intermediate 

vessels. PMPUs use surge control 

vessels when in-process storage, mixing, 

or management of flow rates or volumes 

is needed to assist in manufacturing of 

a product. The PEPO NESHAP defines 

a bottoms receiver, via reference to 40 

CFR part 63, subpart H, as a tank that 

collects distillation bottoms before the 

stream is sent to storage or for further 

downstream processing. 

The PEPO NESHAP does not consider 

surge control vessels and bottoms 

receivers to be storage vessels because 

they are covered by the equipment leak 

provisions. Although these emissions 

sources are regulated under the 

equipment leak provisions (i.e., 40 CFR 

63.1434 by reference to NESHAP 

subpart H), the equipment leak 

requirements refer to the storage vessel 

requirements in NESHAP subpart G. 

Owners and operators of surge control 

vessels and bottoms receivers are 

required to comply with the HON 

storage vessel requirements in 40 CFR 

part 63, subpart G (i.e., use a floating 

roof or route emissions to a closed vent 

system and control to achieve 95- 

percent control), provided the surge 

control vessel or bottoms receiver meets 

certain capacity and vapor pressure 

requirements. For PEPO surge control 

vessels and bottoms receivers at existing 

sources, storage vessel control 

requirements apply if the capacity is 

between 75 m3 (inclusive) and 151 m3

and the MTVP is greater than or equal 

to 13.1 kPa, or the capacity is greater 

than or equal to 151 m3 and the MTVP 

is greater than or equal to 5.2 kPa. For 

PEPO surge control vessels and bottoms 

receivers at new sources, storage vessel 

control requirements apply if the 

capacity is between 38 m3 (inclusive) 

and 151 m3 and the MTVP is greater 

than or equal to 13.1 kPa, or the 

capacity is greater than or equal to 151 

m3 and the MTVP is greater than or 

equal to 0.7 kPa. The PEPO NESHAP 

excludes all other surge control vessels 

and bottoms receivers from emissions 

control requirements. 

We are proposing at 40 CFR 

63.1423(b) to remove surge control 

vessels and bottoms receivers from the 

list of equipment included in the 

definition of equipment leak, and we are 

proposing at 40 CFR 63.1434(a)(8) to 

require that owners and operators of all 

surge control vessels and bottoms 

receivers shall reduce emissions of 

organic HAP consistent with the process 

vent control requirements at 40 CFR 

63.1425 through 63.1431, as applicable. 

The proposed requirements for surge 

control vessels and bottoms receivers 

also represent the level of control found 

to be cost-effective for process vents 

under the technology review in section 

IV.C.3 of this preamble and, therefore, 

the level of control we are proposing for 

process vents. Emissions from surge 

control vessels and bottoms receivers 

are characteristic of process vents, not 

emissions from storage vessels. These 


jspears on DSK121TN23PROD with PROPOSALS
106038 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

75As of March 1, 2024, there were 25 facilities 

that are major sources of HAP emissions in 

operation that are subject to the PEPO NESHAP. 

The list of facilities located in the United States that 

are part of the PEPO Production source category 

with processes subject to the PEPO NESHAP is 

presented in the document titled List of Facilities 

Subject to the PEPO NESHAP, which is available in 

the docket for this action. 

76See 30 Texas Administrative Code Chapter 115, 

Subchapter C, Division 1, available at https:// 

www.tceq.texas.gov/permitting/air/rules/state/115/ 

r5211hp.html. 

77See Louisiana Administrative Code 33:III.2107, 

Chapter 21, available at https:// 

www.deq.louisiana.gov/resources/category/ 

regulations-lac-title-33. 

vessels operate at process temperatures, 

rather than ambient storage 

temperatures; typically do not undergo 

level changes that larger storage vessels 

undergo; and are most often operated 

under pressure with and without intake 

or discharge of non-condensable gases. 

The size of these vessels is also typically 

not correlated with emissions, as are 

storage vessels. We solicit comments on 

the proposed revisions for surge control 

vessels and bottoms receivers. 

6. Transfer Racks 

We are proposing to establish MACT 

standards for transfer racks that are 

associated with processes subject to the 

PEPO NESHAP. The EPA considers 

transfer racks to be part of the collection 

of equipment that comprise a PMPU, as 

defined in the PEPO NESHAP; however, 

the rule does not currently regulate HAP 

emissions from transfer racks. 

Because the equipment used in 

transfer racks at PEPO production 

facilities is similar to the equipment 

used at HON facilities, we are proposing 

to define a ‘‘transfer rack’’ based on a 

similar definition used in the HON (40 

CFR 63.101). We are proposing to define 

‘‘transfer rack’’ at 40 CFR 63.1423(b) to 

mean the collection of loading arms and 

loading hoses, at a single loading rack, 

that are assigned to a PMPU according 

to the procedures specified in 40 CFR 

63.1420(f)(1) through (5) (where the 

term ‘‘transfer rack’’ is substituted for 

‘‘storage vessel’’) and are used to fill 

tank trucks and/or railcars with organic 

liquids that contain one or more organic 

HAP. A transfer rack also includes the 

associated pumps, meters, shutoff 

valves, relief valves, and other piping 

and valves. We are also proposing at 40 

CFR 63.1423(a) (by reference to 40 CFR 

63.101) to define a ‘‘loading rack’’ to 

mean ‘‘a single system used to fill tank 

trucks and railcars at a single geographic 

site. Loading equipment and operations 

that are physically separate (i.e., do not 

share common piping, valves, and other 

equipment) are considered to be 

separate loading racks.’’ The HON 

definition of transfer rack explicitly 

excludes racks, arms, or hoses that only 

transfer liquids containing organic HAP 

as impurities or that use vapor 

balancing during all loading operations. 

We note that the PEPO NESHAP already 

provides these exclusions at 40 CFR 

63.1420(c)(10) and (11). 

Loading losses are the primary source 

of evaporative emissions from rail tank 

car or tank truck operations. Loading 

losses occur as the liquid entering the 

tank during loading displaces the 

organic vapors from the tank headspace 

into the atmosphere. These organic 

vapors are a combination of vapors: (1) 

formed in the empty tank by 

evaporation of residual product from 

previous loads, (2) transferred to the 

tank by vapor balance systems during 

product unloading, and (3) generated in 

the tank during loading of new product. 

Based on data provided to the EPA in 

response to our CAA section 114 request 

(see section II.C of this preamble), we 

identified 17 transfer racks located at 6 

of the 25 PEPO facilities.75 We also 

identified another transfer rack at a 

seventh facility based on our review of 

the facility operating permit. One of the 

25 PEPO facilities is a small business 

and is only subject to the PEPO 

NESHAP because it receives and treats 

wastewater from another PEPO facility; 

therefore, we do not expect this small 

business facility to have a transfer rack 

on site that would be associated with a 

PMPU. For the remaining 17 facilities, 

we used CAA section 114 request data 

to estimate averages of 2 PMPUs per 

facility and 1 transfer rack per PMPU. 

Based on these assumptions, we 

estimated that there are 34 transfer racks 

associated with the 17 facilities (17 

facilities × 2 PMPUs/facility × 1 transfer 

rack/PMPU = 34 transfer racks). 

Therefore, we estimated a nationwide 

total of 52 transfer racks in the PEPO 

Production source category that are 

associated with processes subject to the 

PEPO NESHAP. 

We reviewed available data to 

determine how the best performers are 

controlling emissions from PEPO 

transfer racks. Given that 14 of the 25 

PEPO facilities are located in either 

Louisiana or Texas, we evaluated the 

transfer rack provisions contained in the 

administrative code for these two States. 

The Texas provisions 76 for transfer 

racks provisions apply to materials 

containing VOC having a true vapor 

pressure greater than or equal to 0.5 

pounds per square inch absolute (psia) 

(3.45 kPa) under actual storage 

conditions, and the Louisiana 

provisions 77 apply to materials 

containing VOC with a true vapor 

pressure of 1.5 psia (10.3 kPa) or greater 

at loading conditions. In each of these 

rules, owners and operators are required 

to use a vapor balance system or reduce 

emissions by 90 percent during loading 

operations (at a transfer rack). We also 

reviewed the transfer rack requirements 

in the HON because one PEPO facility 

said (in response to our CAA section 

114 request) that they voluntarily 

comply with the HON for their PEPO 

transfer racks. The HON regulates 

transfer operations at 40 CFR 63.126 

through 63.130. The HON requires 

owners and operators of each HON 

transfer rack that annually loads greater 

than or equal to 0.65 million liters of 

liquid products that contain organic 

HAP with a rack weighted average vapor 

pressure greater than or equal to 10.3 

kPa to equip each transfer rack with a 

vapor collection system and control 

device to reduce total organic HAP 

emissions by 98 percent by weight or to 

an exit concentration of 20 ppmv. The 

HON also allows multiple other options 

to control emissions from applicable 

transfer racks, including use of a flare or 

collecting emissions for use in the 

process, a fuel gas system, or a vapor 

balance system. 

For the purpose of addressing 

regulatory gaps, we are proposing in this 

action that the requirements to use a 

vapor balance system or reduce 

emissions by 90 percent during loading 

operations (at a transfer rack) are 

consistent with CAA section 112(d) 

controls and reflect the MACT floor for 

transfer racks at existing PEPO sources. 

We also propose that the transfer rack 

requirements in the HON (i.e., reduce 

emissions by 98 percent by weight or to 

an exit concentration of 20 ppmv during 

loading operations at a transfer rack) are 

consistent with CAA section 112(d) 

controls and reflect the MACT floor for 

transfer racks at new PEPO sources and 

beyond-the-floor control for transfer 

racks at existing PEPO sources. 

We consider the vapor pressure 

applicability threshold in the Texas 

transfer rack provisions to be more 

stringent than the vapor pressure 

applicability thresholds contained in 

the HON and the Louisiana provisions. 

Therefore, we are proposing the vapor 

pressure applicability threshold 

specified in the Texas transfer rack 

provisions in addition to the HON 

transfer rack requirements. In summary, 

we are proposing at 40 CFR 63.1434(j), 

by reference to 40 CFR 63.126 through 

63.130, that owners and operators of 

PEPO transfer racks that load materials 

with an MTVP greater than or equal to 

0.5 psia (3.45 kPa) under actual storage 

conditions (i.e., Group 1 transfer racks 

as defined in 40 CFR 63.1423(b)) must 

comply with the HON requirements at 

40 CFR 63.126 through 63.130, if the 


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78For example, a facility reports EtO emissions 

from a dryer and a solids handling system that are 

not considered part of the affected source subject 

to the PEPO NESHAP because they occur after 

epoxide polymerization and catalyst removal steps. 

79For example, the facility reporting EtO 

emissions from a dryer and a solids handling 

system has used a flare to control emissions from 

the dryer and a baghouse to control emissions from 

the vent collection system associated with the 

solids handling system. 

material contains organic HAP as 

defined by 40 CFR 63.1423(b). To 

accommodate these proposed 

requirements, we are also proposing to 

remove the exemption of the terms 

‘‘transfer’’ and ‘‘transferred’’ in the 

definition of ‘‘maximum true vapor 

pressure’’ at 40 CFR 63.1423(b). We 

anticipate that these proposed 

requirements achieve any additional 

emission reductions because we believe 

that transfer racks operating at PEPO 

sources load materials with very low 

true vapor pressures (i.e., less than 0.3 

psia based on data provided to the EPA 

in response to our CAA section 114 

request) or are using vapor balancing as 

a control option. As a beyond-the-floor 

control option, we explored controlling 

the organic HAP emissions from PEPO 

transfer racks with add-on controls (i.e., 

thermal oxidizers) and we determined 

that, although feasible, such add-on 

controls were unreasonably expensive, 

given that organic HAP emissions from 

PEPO transfer racks are expected to be 

small due to their low true vapor 

pressures (e.g., all but one of the PEPO 

transfer racks in the modeling file are 

reported as each emitting less than 

about 380 pounds of organic HAP per 

year). Therefore, we concluded that the 

control of organic HAP using a thermal 

oxidizer would not be reasonable. For 

example, the EPA estimated a cost of 

approximately $1,700,000 per ton of 

HAP emissions reduced for use of a 

thermal oxidizer. We solicit comments 

on the proposed standards for transfer 

racks. 

7. Butylene Oxide 

In this action, we are proposing to add 

butylene oxide (also known as 1,2- 

epoxybutane) to the definition of 

‘‘epoxide’’ in 40 CFR 63.1423(b) and to 

the list of HAP presented in table 4 to 

the PEPO NESHAP. In a 1997 document 

supporting the establishment of the 

PEPO Production source category titled 

Polyether Polyols Production Industry 

Characterization, which is available in 

the docket for this action (Docket ID No. 

EPA–HQ–OAR–2023–0282), the EPA 

established two subcategories for the 

purpose of analyzing MACT floors and 

regulatory alternatives: (1) PEPO made 

from polymerization of epoxides (i.e., 

EtO, propylene oxide, butylene oxide), 

and (2) PEPO made from the 

polymerization of THF. While the EPA 

recognized in this supporting 

documentation that butylene oxide is an 

epoxide used as a reactant to make 

PEPO, the EPA incorrectly stated that 

butylene oxide was not a HAP; 

therefore, the EPA did not include this 

compound in the epoxide definition or 

table 4 to subpart PPP. 

Because most PEPO process units 

make a variety of products, including 

copolymers made from more than one 

type of epoxide, we have determined 

that any process unit using butylene 

oxide is likely to also use other epoxides 

(i.e., EtO or propylene oxide); as such, 

gas streams from the process are already 

required to be monitored and controlled 

according to the PEPO NESHAP. For 

example, one facility reports EtO, 

propylene oxide, and 1,2-epoxybutane 

from the same PEPO reactor in the 2017 

NEI. Therefore, we conclude that this 

proposed action will not result in the 

control of processes that are not already 

subject to the epoxide emissions 

standards specified in the PEPO 

NESHAP and that impacts will be 

minimal. We solicit comments on the 

proposed inclusion of butylene oxide. 

8. 40 CFR 63.1420(d)(3) Exemption 

The PEPO NESHAP (40 CFR 

63.1420(d)(3)) exempts from the 

definition of affected source reactions or 

processing that occur after completion 

of epoxide polymerization and all 

catalyst removal steps, if any. In this 

action, the EPA is proposing at 40 CFR 

63.1420(d)(4) to remove the exemption 

in 40 CFR 63.1420(d)(3) and to require 

capture and control of emissions from 

these currently unregulated steps in the 

PEPO production process (which may 

include, but are not limited to, solvent 

removal, purification, drying, and solids 

handling operations). 

The reactions or processing that occur 

after completion of epoxide 

polymerization and catalyst removal 

steps are included in the PEPO 

Production source category. The EPA is 

proposing to expand the definition of 

the affected source because HAP 

emissions are possible from these 

steps 78 and are thus a regulatory gap 

that the EPA is required to address. 

Additionally, because the EPA 

concludes that the current MACT 

standards for process vents are 

appropriate for sources associated with 

reactions or processing that occur after 

completion of epoxide polymerization 

and catalyst removal steps,79 the EPA is 

proposing that it is not necessary to 

evaluate alternative MACT limits for 

these currently unregulated steps 

beyond subjecting them to the 

previously established MACT limits for 

process vents. We solicit comments on 

the proposed removal of the exemption 

in 40 CFR 63.1420(d)(3). 

E. What other actions are we proposing? 

In addition to the proposed actions 

related to CAA sections 112(d)(2), (3), 

and (6), 112(h), and 112(f) discussed in 

sections IV.B through IV.D of this 

preamble, we are proposing to address 

selected issues raised in the petition for 

reconsideration (see section II.A.2 of 

this preamble). In addition, we are 

proposing changes to the PEPO 

NESHAP recordkeeping and reporting 

requirements to require the use of 

electronic reporting of certain reports, 

and we are proposing other technical 

amendments and definition revisions to 

improve the clarity and enforceability of 

certain provisions in the PEPO 

NESHAP. Our rationale and proposed 

changes related to all these issues are 

discussed as follows. 

1. Reconsideration Issues 

The EPA discusses certain issues 

raised in the petition for reconsideration 

(see section II.A.2 of this preamble) 

related to affirmative defense and PRDs 

as described in this section IV.E.1 of the 

preamble. 

a. Affirmative Defense 

As part of the 2014 PEPO NESHAP 

RTR rulemaking (see 59 FR 17340, 

March 27, 2014), the EPA included the 

ability to assert an affirmative defense to 

civil penalties for violations caused by 

malfunctions (see 40 CFR 63.1420(i)) to 

create a system that incorporated some 

flexibility, recognizing that there is a 

tension inherent in many types of air 

regulations to ensure adequate 

compliance while simultaneously 

recognizing that, despite the most 

diligent of efforts, owners or operators 

may violate emission standards under 

circumstances entirely beyond the 

control of the source. Although the EPA 

recognized that its case-by-case 

enforcement discretion provides 

sufficient flexibility in these 

circumstances, we included the 

affirmative defense provision to provide 

a more formalized approach and more 

regulatory clarity. See Weyerhaeuser Co. 

v. Costle, 590 F.2d 1011, 1057–58 (D.C. 

Cir. 1978) (holding that an informal 

case-by-case enforcement discretion 

approach is adequate); but see Marathon 

Oil Co. v. EPA, 564 F.2d 1253, 1272–73 

(9th Cir. 1977) (requiring a more 

formalized approach to consideration of 

‘‘upsets beyond the control of the permit 

holder.’’). Under the EPA’s regulatory 

affirmative defense provisions, if a 

source could demonstrate in a judicial 


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80The court’s reasoning in NRDC focuses on civil 

judicial actions. The court noted that ‘‘EPA’s ability 

to determine whether penalties should be assessed 

for CAA violations extends only to administrative 

penalties, not to civil penalties imposed by a 

court.’’ Id. 

81https://www.epa.gov/electronic-reporting-airemissions/electronic-reporting-tool-ert. 

or administrative proceeding that it had 

met the requirements of the affirmative 

defense in the regulation, civil penalties 

would not be assessed. However, the 

petitioners argued that the EPA should 

remove the affirmative defense 

provisions in the PEPO NESHAP 

because the court vacated the 

affirmative defense in one of the EPA’s 

other CAA section 112 regulations. 

NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 

2014) (vacating affirmative defense 

provisions in the CAA section 112 rule 

establishing emission standards for 

Portland cement kilns). The court found 

that the EPA lacked authority to 

establish an affirmative defense for 

private civil suits and held that under 

the CAA, the authority to determine 

civil penalty amounts in such cases lies 

exclusively with the courts, not the 

EPA. Specifically, the court found: ‘‘As 

the language of the statute makes clear, 

the courts determine, on a case-by-case 

basis, whether civil penalties are 

‘appropriate.’ ’’ See NRDC, 749 F.3d at 

1063 (‘‘[U]nder this statute, deciding 

whether penalties are ‘appropriate’ in a 

given private civil suit is a job for the 

courts, not EPA.’’).80

In light of NRDC (and as requested by 

the petitioners), the EPA published a 

separate proposal (89 FR 52425, June 24, 

2024) to remove regulatory affirmative 

defense provisions from three NSPS and 

15 NESHAP (including the PEPO 

NESHAP). The public comment period 

for that proposal closed on August 8, 

2024, and in this proposal, the EPA is 

not reopening the comment period or 

otherwise seeking additional public 

comments on this issue. The EPA will 

take separate final action on this issue, 

including responding to public 

comments submitted on the June 24, 

2024, proposal. That final action will 

constitute the EPA’s response to the 

petition for reconsideration on the 

affirmative defense provision 

promulgated in the 2014 final rule (79 

FR 17340, March 27, 2014). 

Consequently, it is not necessary for the 

EPA to further address this issue in this 

proposed rulemaking. 

b. PRDs 

The petitioners stated that, although 

the PEPO NESHAP RTR proposal (77 FR 

1268, January 9, 2012) required facilities 

to install electronic indicators and 

alarms to ensure compliance with the 

proposed prohibition of pressure 

releases to the atmosphere from PRDs in 

organic HAP service, the EPA made 

these types of equipment optional in the 

final rule (79 FR 17340, March 27, 

2014), allowing sources to use ‘‘a device 

or system that is capable of identifying 

and recording the time and duration of 

each pressure release (e.g., rupture disk 

indicators, magnetic sensors, motion 

detectors on the pressure relief valve 

stem, flow monitors, and pressure 

monitors) in lieu of prescribing that 

PRDs be equipped with release 

indicators and alarms.’’ The petitioners 

contended that it was not feasible to 

comment on the EPA’s change to allow 

other indicators of atmospheric releases 

from PRDs. Additionally, the petitioners 

argued that the EPA did not provide the 

public an opportunity to comment when 

it narrowed the applicability of the PRD 

release prohibition in the final rule to 

PRDs ‘‘in organic HAP service,’’ and 

that, at a minimum, the EPA must 

narrow the applicability to only PRDs 

‘‘in HAP service’’ to affect all HAP. 

Finally, the petitioners asserted that the 

EPA did not adequately justify giving 

PEPO facilities 3 years to comply with 

the PRD requirements in the PEPO 

NESHAP. 

The PEPO NESHAP codifies the PRD 

requirements at 40 CFR 63.1434(c). We 

are not proposing to make any changes 

to the PRD requirements at 40 CFR 

63.1434(c) as we believe the 2014 final 

rule (79 FR 17340, March 27, 2014) 

reached appropriate conclusions 

regarding each of these issues; however, 

we request comment on these 

requirements. We note that neither the 

proposed nor final rule was specific to 

a particular type of release indicator, 

and both the proposed and final rules 

anticipated use of a device capable of 

immediately notifying the facility of a 

release. Additionally, both the proposal 

and the final rule specified 

requirements for PRDs ‘‘in organic HAP 

service,’’ and we disagree with the 

petitioners that we should expand the 

scope of the PRD requirements because 

the PEPO production process includes 

reacting organic chemicals together to 

make an organic chemical product. 

Also, we believe other changes we made 

to the PRD requirements between 

proposal and final were for clarification 

and were a reasonable outgrowth of 

public comments. Finally, we stated in 

the preamble to the final rule (see 79 FR 

17345) that time to comply with the 

PRD requirements is needed for 

facilities to ‘‘research equipment and 

vendors, purchase, install, test and 

properly operate any necessary 

equipment.’’ Even so, the petitioners’ 

argument that the EPA did not 

adequately justify giving PEPO facilities 

3 years to comply with the PRD 

requirements is no longer relevant, 

given that all new and existing sources 

have been complying with the PRD 

requirements for over 7 years (i.e., since 

March 27, 2017). 

2. Electronic Reporting 

As part of the 2014 PEPO NESHAP 

RTR rulemaking (see 59 FR 17340, 

March 27, 2014), the EPA began 

requiring owners or operators of PEPO 

facilities to submit electronic copies of 

certain required performance test 

reports. The proposed rule amendments 

in this action would require owners and 

operators of PEPO processes to submit 

electronic copies of required 

performance test reports using new 

procedures. In lieu of requiring owners 

and operators to submit the results of 

performance tests ‘‘by direct computerto-computer electronic transfer via EPAprovided software’’ (see 40 CFR 

63.1439(e)(9)(i)), we are proposing at 40 

CFR 63.1426(b)(6) and 63.1439(e)(9)(iii) 

that owners and operators must submit 

the results of the performance test 

following the procedures specified in 40 

CFR 63.9(k), which requires use of the 

EPA’s Central Data Exchange (CDX) 

using the Compliance and Emissions 

Data Reporting Interface (CEDRI). The 

proposed rule amendments would also 

require owners or operators to submit 

flare management plans and periodic 

reports (including fenceline monitoring 

reports) through the EPA’s CDX using 

CEDRI (see proposed 40 CFR 63.1436(b), 

63.1439(e)(6), and 63.1434(i)). A 

description of the electronic data 

submission process is provided in the 

document titled Electronic Reporting 

Requirements for New Source 

Performance Standards (NSPS) and 

National Emission Standards for 

Hazardous Air Pollutants (NESHAP) 

Rules, available in the docket for this 

action. 

The proposed rule would require that 

performance test results collected using 

test methods that are supported by the 

EPA’s Electronic Reporting Tool (ERT) 

as listed on the ERT website 81 at the 

time of the test be submitted in the 

format generated through the use of the 

ERT or an electronic file consistent with 

the XML schema on the ERT website, 

and other performance test results be 

submitted in portable document format 

(PDF) using the attachment module of 

the ERT. Flare management plans would 

be uploaded as a PDF file. 

For periodic reports (including 

fenceline monitoring reports), the 

proposed rule would require that 


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82See 

Part_63_Subpart_PPP_63.1439(e)(6) 

_Periodic_Report.xlsx, which is available in the 

docket for this action. 

83We are proposing at 40 CFR 63.1421(c)(5) that 

the approval to an alternative to any electronic 

reporting to the EPA proposed for the PEPO 

NESHAP cannot be delegated to State, local, or 

Tribal agencies. 

84EPA’s Final Plan for Periodic Retrospective 

Reviews, August 2011. Available at: https:// 

www.regulations.gov/document?D=EPA-HQ-OA2011-0156-0154. 

85E-Reporting Policy Statement for EPA 

Regulations, September 2013. Available at: https:// 

www.epa.gov/sites/production/files/2016-03/ 

documents/epa-ereporting-policy-statement-2013- 

09-30.pdf. 

86 Digital Government: Building a 21st Century 

Platform to Better Serve the American People, May 

2012. Available at: https:// 

obamawhitehouse.archives.gov/sites/default/files/ 

omb/egov/digital-government/digitalgovernment.html. 

owners and operators use an 

appropriate spreadsheet template to 

submit information to CEDRI. A draft 

version of the proposed templates for 

these reports is included in the docket 

for this action.82 The EPA specifically 

requests comment on the content, 

layout, and overall design of the 

templates. We are proposing that 

owners and operators begin using the 

templates for periodic reports other than 

fenceline reports 3 years after the final 

rule is published in the Federal 

Register, or after the reporting template 

for the subpart has been available on the 

CEDRI website for 1 year, whichever 

date is later. Owners and operators 

would begin using the templates for 

fenceline monitoring reports starting 

when the first fenceline monitoring 

report is due. 

Additionally, the EPA has identified 

two broad circumstances in which 

electronic reporting extensions may be 

provided. These circumstances are: (1) 

outages of the EPA’s CDX or CEDRI 

which preclude an owner or operator 

from accessing the system and 

submitting required reports, and (2) 

force majeure events, which are defined 

as events that will be or have been 

caused by circumstances beyond the 

control of the affected facility, its 

contractors, or any entity controlled by 

the affected facility that prevent an 

owner or operator from complying with 

the requirement to submit a report 

electronically. Examples of force 

majeure events are acts of nature, acts of 

war or terrorism, or equipment failure or 

safety hazards beyond the control of the 

facility. The EPA is providing these 

potential extensions for submitting 

electronic copies of required 

performance test reports, flare 

management plans, and periodic reports 

(including fenceline monitoring reports) 

to protect owners and operators from 

noncompliance in cases where they 

cannot successfully submit a report by 

the reporting deadline for reasons 

outside of their control. In both 

circumstances, the decision to accept 

the claim of needing additional time to 

report is within the discretion of the 

Administrator, and reporting should 

occur as soon as possible. These 

potential extensions were recently 

added to 40 CFR part 63, subpart A, 

General Provisions at 40 CFR 63.9(k) 

and we are proposing to amend the 

entry for 40 CFR 63.9(k) of table 1 to the 

PEPO NESHAP (Applicability of 

General Provisions to Subpart PPP 

Affected Sources) to remove the 

constraint that 40 CFR 63.9(k) applies 

‘‘only as specified in Sec. 63.9(j)’’ such 

that 40 CFR 63.9(k) would apply for any 

notifications or reports required by the 

PEPO NESHAP to be submitted 

electronically. 

The electronic submittal of the reports 

addressed in this proposed rulemaking 

will increase the usefulness of the data 

contained in those reports, is in keeping 

with current trends in data availability 

and transparency, will further assist in 

the protection of public health and the 

environment, will improve compliance 

by facilitating the ability of regulated 

facilities to demonstrate compliance 

with requirements and by facilitating 

the ability of delegated State, local, 

Tribal, and territorial air agencies and 

the EPA to assess and determine 

compliance, and will ultimately reduce 

burden on regulated facilities, delegated 

air agencies, and the EPA.83 Electronic 

reporting also eliminates paper-based, 

manual processes, thereby saving time 

and resources, simplifying data entry, 

eliminating redundancies, minimizing 

data reporting errors, and providing data 

quickly and accurately to the affected 

facilities, air agencies, the EPA, and the 

public. Moreover, electronic reporting is 

consistent with the EPA’s plan 84 to 

implement Executive Order 13563 and 

is in keeping with the EPA’s Agencywide policy 85 developed in response to 

the White House’s Digital Government 

Strategy.86 For more information on the 

benefits of electronic reporting, see the 

document titled Electronic Reporting 

Requirements for New Source 

Performance Standards (NSPS) and 

National Emission Standards for 

Hazardous Air Pollutants (NESHAP) 

Rules, referenced earlier in this section. 

3. Performance Testing 

The EPA is proposing at 40 CFR 

63.1437(a) performance testing once 

every 5 years to demonstrate 

compliance with emission limits for 

certain process vents (if you route 

emissions to a control device other than 

a flare). We determined that periodic 

emission testing should be required to 

help ensure continuous compliance. 

Repeat performance tests are already 

required by permitting authorities for 

some facilities. Further, requiring 

periodic repeat performance tests will 

help to ensure that control systems are 

properly maintained over time, thereby 

reducing the potential for acute 

emissions episodes. Currently, facilities 

conduct a one-time performance test or 

design evaluation and then monitor 

operating parameters. A design 

evaluation (in lieu of performance 

testing) is currently allowed for control 

techniques that receive less than 10 tpy 

of uncontrolled organic HAP emissions 

from one or more PMPU. However, we 

are proposing to remove the design 

evaluation option at 40 CFR 

63.1426(b)(6) and (7) and (f), and require 

ongoing performance tests for owners 

and operators using a combustion, 

recovery, or recapture device to comply 

with an epoxide or organic HAP percent 

reduction efficiency requirement in 40 

CFR 63.1425(b)(1)(i), (b)(2)(ii), (c)(1)(ii), 

(c)(3)(ii), or (d)(2); an epoxide 

concentration limitation in 40 CFR 

63.1425(b)(1)(ii) or (b)(2)(iii); or an 

annual epoxide emission limitation in 

40 CFR 63.1425(b)(1)(iii) or (b)(2)(iv). 

We are proposing that the ongoing 

performance tests be conducted at a 

minimum frequency of once every 5 

years to supplement the parameter 

monitoring and to ensure that emission 

controls continue to operate as 

demonstrated during the initial 

performance test. Currently 40 CFR 

63.1437(a) also requires the owner or 

operator to record the necessary process 

information to document operating 

conditions during the test. We are 

proposing to clarify that this includes an 

explanation to support that the 

operating conditions during each test 

represent the entire range of normal 

operation, including conditions for 

maximum emissions, even if such 

emissions are not expected during 

maximum production. 

In addition, we are proposing to 

eliminate the option in 40 CFR 

63.1427(a)(2)(ii) that exempts owners or 

operators using ECO as a control 

technique from directly measuring the 

concentration of unreacted epoxide 

when determining the batch cycle 

percent epoxide emission reduction. 

Currently, the rule requires comparing 

the epoxide concentration obtained 

through direct measurement for one 

product from each product class with 

the concentration determined using 


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87We are proposing to define the term 

‘‘breakthrough’’ at 40 CFR 63.1423(a) (by reference 

to 40 CFR 63.101) to mean the time when the level 

of HAP or TOC detected is at the highest 

concentration allowed to be discharged from an 

adsorber system. 

process knowledge, reaction kinetics, 

and engineering knowledge. Owners 

and operators are exempt at 40 CFR 

63.1427(a)(2)(ii) from this direct 

measurement comparison if 

uncontrolled epoxide emissions before 

the end of the ECO are less than 10 tpy. 

However, we are proposing to remove 

this exemption and to require that 

owners and operators conduct the 

comparison of epoxide concentration 

using direct measurement for one 

product from each product class even if 

uncontrolled epoxide emissions before 

the end of the ECO are less than 10 tpy. 

We solicit comments on the proposed 

revisions to the performance testing and 

ECO direct measurement requirements. 

4. Certain Definitions That Refer to the 

HON 

We note that in an effort to remove 

redundancy and improve consistency, 

the EPA recently finalized moving all of 

the definitions from NESHAP subparts 

G and H (i.e., 40 CFR 63.111 and 40 CFR 

63.161, respectively) into the definition 

section of NESHAP subpart F (i.e., 40 

CFR 63.101) (see 89 FR 42932, May 16, 

2024). Given that the PEPO NESHAP 

directly references these provisions for 

certain definitions (see 40 CFR 63.1423), 

we are proposing to revise the phrasing 

used in 40 CFR 63.1423(a) to refer to 

NESHAP subpart F in instances where 

a definition in the PEPO NESHAP 

points to either NESHAP subpart G or 

H. 

We are also proposing editorial 

changes that clarify references in the 

PEPO NESHAP definitions at 40 CFR 

63.1423(b) to properly reference the 

correct HON citation for ‘‘continuous 

recorder,’’ ‘‘maximum true vapor 

pressure,’’ ‘‘residual,’’ and ‘‘waste 

management unit.’’ 

We are proposing to delete ‘‘heat 

exchange system’’ from the list of terms 

in 40 CFR 63.1423(a) that refer to 

subpart F for their definition. We are 

proposing to define ‘‘heat exchange 

system’’ at 40 CFR 63.1423(b) so the 

definition refers to PMPUs instead of 

CMPUs. We are proposing ‘‘heat 

exchange system’’ to mean a device or 

collection of devices used to transfer 

heat from process fluids to water 

without intentional direct contact of the 

process fluid with the water (i.e., noncontact heat exchanger) and to transport 

and/or cool the water in a closed-loop 

recirculation system (cooling tower 

system) or a once-through system (e.g., 

river or pond water). For closed-loop 

recirculation systems, the heat exchange 

system consists of a cooling tower, all 

PMPU heat exchangers that are in 

organic HAP service and serviced by 

that cooling tower, and all water lines 

to and from these process unit heat 

exchangers. For once-through systems, 

the heat exchange system consists of all 

heat exchangers that are in organic HAP 

service servicing an individual PMPU 

and all water lines to and from these 

heat exchangers. Sample coolers or 

pump seal coolers are not considered 

heat exchangers for the purpose of this 

definition and are not part of the heat 

exchange system. Intentional direct 

contact with process fluids results in the 

formation of a wastewater. We are also 

proposing to revise the definition of ‘‘in 

organic HAP service’’ to include a heat 

exchange system, to be consistent with 

the use of ‘‘in organic HAP service’’ in 

the definition of ‘‘heat exchange 

system.’’ 

5. Monitoring for Adsorbers That 

Cannot Be Regenerated and 

Regenerative Adsorbers That Are 

Regenerated Offsite 

We are proposing to add monitoring 

requirements at 40 CFR 63.1429(a)(9) for 

adsorbers that cannot be regenerated 

and regenerative adsorbers that are 

regenerated offsite because the PEPO 

NESHAP does not currently include 

specific monitoring requirements for 

this type of APCD and it is possible that 

owners and operators may use this type 

of APCD to control emissions from 

PEPO sources. We are proposing that 

owners and operators of this type of 

APCD use dual adsorbent beds in series. 

We are proposing to prescribe a dualbed system because the use of a single 

bed does not ensure continuous 

compliance unless the bed is replaced 

significantly before breakthrough.87 The 

proposed monitoring requirements for 

non-regenerative adsorbers fulfill the 

EPA’s obligation to establish monitoring 

requirements to ensure continuous 

compliance with the emission limits 

(e.g., 98-percent control or a 20-ppmv 

TOC outlet concentration) when owners 

or operators are using these types of 

control devices to comply with the 

standards. A dual-bed system will allow 

one bed to be saturated before it is 

replaced and, therefore, makes efficient 

use of the adsorber bed without 

exceeding the emission limits. 

Similar to regenerative adsorbers, to 

monitor performance deterioration, we 

are proposing measurements of HAP or 

TOC using a portable analyzer or 

chromatographic analysis for nonregenerative absorbers. We are 

proposing that owners or operators 

obtain these measurements at the outlet 

of the first adsorber bed in series using 

a sampling port, and that they obtain 

measurements monthly (if the bed has at 

least 2 months of the bed design life 

remaining), weekly (if the bed has 

between 2 months and 2 weeks of bed 

design life remaining), or daily (when 

the bed has less than 2 weeks of bed 

design life remaining). Also, we propose 

to require that owners and operators 

establish an average adsorber bed life 

from a design evaluation as well as 

conduct monitoring no later than 3 days 

after a bed is put into service as the first 

bed in series to confirm that it is 

functioning properly. 

We did not identify any carbon 

adsorbers in the risk modeling file. To 

validate this finding, we conducted an 

air permit review alongside analysis of 

our CAA section 114 request data and 

confirmed that PEPO facilities do not 

currently use carbon adsorbers to 

control HAP emissions from PEPO 

sources. Therefore, we do not anticipate 

any cost associated with adding these 

proposed monitoring and operation 

requirements to the PEPO NESHAP for 

non-regenerative adsorbers and 

adsorbers with beds that are regenerated 

off-site. Additionally, the EPA 

acknowledges that these proposed 

requirements could be considered under 

CAA section 112(d)(6) because of the 

specification to have two adsorber beds 

in series, instead of as a proposed 

change to the monitoring requirements. 

However, our rationale for why a second 

bed is needed would not be any 

different if we described these proposed 

changes under CAA section 112(d)(6) 

instead of as a monitoring change. As 

previously mentioned, we are proposing 

these changes because the current PEPO 

NESHAP does not contain monitoring 

requirements for non-regenerative 

adsorbers, and it is possible that owners 

and operators may use this type of 

APCD to control emissions from PEPO 

sources. 

6. Listing of 1-Bromopropane (1–BP) as 

a HAP 

On January 5, 2022, the EPA 

published in the Federal Register (87 

FR 393) a final rule amending the list of 

HAP under the CAA to add 1- 

bromopropane in response to public 

petitions previously granted by the EPA. 

For the PEPO Production source 

category, we conclude that the inclusion 

of 1–BP as an organic HAP will not have 

any effect on the MACT standards. First, 

1–BP is not an epoxide, nor is it THF. 

Furthermore, we have no information 

showing that 1–BP is used, produced, or 

emitted to make or modify the PEPO 

product. Accordingly, we are proposing 


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that no further action is required related 

to 1–BP. We solicit comments on this 

approach, and should new information 

submitted to the EPA show that 1–BP is 

emitted from this source category, the 

EPA will consider this information in 

the context of developing any MACT 

standards that may be needed to address 

emissions of 1–BP. We also note that in 

several instances in the PEPO NESHAP, 

facilities can comply with a TOC 

concentration standard (e.g., 20 ppmv), 

which could adequately regulate 

emissions of 1–BP if it is emitted from 

this source category. 

7. Other Editorial Changes 

The EPA is proposing additional 

changes that address technical and 

editorial corrections for the PEPO 

NESHAP and overlap with the P&R I 

NESHAP as detailed here: 

• The EPA is proposing to replace 

‘‘elastomer’’ with ‘‘polyether polyol’’ in 

40 CFR 63.1420(e)(3) to correct a 

typographical error, given that the PEPO 

NESHAP applies to PMPUs and does 

not use the term ‘‘elastomer’’ anywhere 

else in the rule. 

• The EPA is proposing to delete 

‘‘parts per million by volume’’ in 40 

CFR 63.1425(f)(7)(iv) because ‘‘ppmv’’ is 

defined previously in the rule. 

• The EPA is proposing at 40 CFR 

63.1426(b)(4) and (5) to allow owners 

and operators of emission sources 

controlled by a boiler or process heater 

burning hazardous waste to comply 

with the provisions of 40 CFR part 63, 

subpart EEE, rather than complying 

with the performance test provisions in 

the PEPO NESHAP. 

• The EPA is proposing to clarify at 

40 CFR 63.1426(c)(2) that performance 

tests and compliance determinations 

must be conducted according to the 

schedule and procedures in 40 CFR 

63.1437. 

• The EPA is proposing to remove the 

exemption at 40 CFR 63.1426(d)(1) that 

allows owners and operators to be 

exempt from determining uncontrolled 

organic HAP emissions for process vents 

in a PMPU if all process vents subject 

to the emission reduction requirements 

of 40 CFR 63.1425(b), (c)(1), or (d)(2) are 

controlled at all times using a 

combustion, recovery, or recapture 

device, or ECO. Based on our review of 

historical documents, it is not clear why 

this exemption is needed. Instead, we 

are proposing that owners and operators 

must determine uncontrolled emissions 

for each process vent at a PMPU that is 

complying with the process vent control 

requirements in 40 CFR 63.1425(b)(1)(i), 

(b)(1)(iii), (b)(2)(ii), (b)(2)(iv), (c)(1)(ii), 

or (d)(2) using a combustion, recovery, 

recapture device, or ECO. 

• The EPA is proposing to correct a 

reference error in 40 CFR 63.1430(c), 

(d)(1), (d)(1)(i), and (k) such that the 

paragraphs point to not only table 5 to 

40 CFR part 63, subpart PPP, but also 

table 6 to 40 CFR part 63, subpart PPP. 

• The EPA is proposing to add at 40 

CFR 63.1439(d)(11) requirements to 

maintain records of excursions. The 

EPA is proposing to require that sources 

keep records of this information to 

ensure that there is adequate 

information to allow the EPA to 

determine the severity of any failure to 

meet a standard, and to provide data 

that may document how the source met 

the general duty to minimize emissions 

when the source has failed to meet an 

applicable standard. 

• The EPA is proposing to clarify at 

40 CFR 63.1439(e)(6)(i) that all Periodic 

Reports must contain the company 

name and address (including county), as 

well as the beginning and ending dates 

of the reporting period. 

• The EPA is proposing to clarify at 

40 CFR 63.1439(e)(6)(iii)(B) that for each 

excursion reported in a Periodic Report, 

the owner or operator must include the 

start date and time, duration, cause, a 

list of the affected sources or equipment, 

an estimate of the quantity of each 

regulated pollutant emitted over any 

emission limit, a description of the 

method used to estimate the emissions, 

actions taken to minimize emissions, 

and any corrective action taken. 

• The EPA is proposing to clarify at 

40 CFR 63.1439(e)(6)(iii)(C) that for 

periods when monitoring data were not 

collected, the Periodic Report must 

include start date, start time, and 

duration of each period when 

monitoring data were not collected. 

• The EPA is proposing to clarify at 

40 CFR 63.1439(e)(6)(ix)(C)(2) that for 

PRDs in organic HAP service, Periodic 

Reports must include ‘‘start date, start 

time, and duration in minutes of the 

pressure release’’ instead of ‘‘date, time, 

and duration of the pressure release.’’ 

• The EPA is proposing to insert the 

missing word ‘‘releases’’ at 40 CFR 

63.1439(e)(6)(ix)(C)(5) to clarify that we 

mean ‘‘pressure releases,’’ not 

‘‘pressure.’’ 

• The EPA is proposing to remove the 

entry for 40 CFR 63.6(e) of table 1 to the 

PEPO NESHAP because it is 

unnecessary given that there are already 

entries in the table for all subparagraphs 

associated with 40 CFR 63.6(e). We are 

also proposing to change ‘‘yes’’ to ‘‘no’’ 

for the entry for 40 CFR 63.6(e)(2) 

because this provision has no 

requirement and is ‘‘[Reserved].’’ 

• The EPA is proposing to add an 

entry for 40 CFR 63.7(a)(4) into table 1 

to the PEPO NESHAP because it is 

missing and is applicable. 

• The EPA is proposing to revise the 

entries for 40 CFR 63.10(b)(2) and (d)(5) 

of table 1 to the PEPO NESHAP to 

specify where the recordkeeping and 

reporting requirements are in the PEPO 

NESHAP. 

• The EPA is proposing to edit the 

title of table 2 to the PEPO NESHAP to 

include ‘‘and Group 1 Polymers and 

Resins’’ because the content in the table 

contains provisions related the P&R I 

NESHAP. 

• The EPA is proposing to correct 

several explanations in table 2 to the 

PEPO NESHAP to refer to the correct 

paragraph(s) for certain requirements 

being proposed in this action. 

• In reviewing cross-references 

between the PEPO NESHAP and P&R I 

NESHAP, the EPA noticed that, even 

though the rule text exists, the EPA 

inadvertently removed the ‘‘(iii)’’ for 

paragraph 40 CFR 63.506(e)(6)(iii) in its 

recent final rulemaking (see 89 FR 

42932, May 16, 2024) and is proposing 

to correct this typographical error by 

adding the ‘‘(iii)’’ back into the P&R I 

NESHAP. This proposed edit does not 

change any rule text within 40 CFR 

63.506(e)(6)(iii). 

F. What compliance dates are we 

proposing? 

The proposed amendments in this 

rulemaking for adoption under CAA 

sections 112(d)(2) and (3) and 112(h) 

(see section IV.D of this preamble) and 

CAA section 112(d)(6) (see section IV.C 

of this preamble) are subject to the 

compliance deadlines outlined in the 

CAA under section 112(i). The proposed 

amendments in this rulemaking for 

adoption under CAA section 112(f) (see 

section IV.B of this preamble) are 

subject to the compliance deadlines 

outlined in the CAA under section 

112(f)(4). 

For all the requirements we are 

proposing under CAA sections 

112(d)(2), (3), and (6), and 112(h) 

(except for the fenceline monitoring 

requirements), we are proposing at 40 

CFR 63.1422(h) that existing affected 

sources and affected sources that were 

new sources under the current PEPO 

NESHAP (i.e., they commenced 

construction or reconstruction after 

September 4, 1997, and on or before 

December 27, 2024 must comply with 

all of the amendments no later than 3 

years after the effective date of the final 

rule or upon startup, whichever is later. 

For existing sources, CAA section 112(i) 

provides that the compliance date shall 

be as expeditious as practicable, but no 

later than 3 years after the effective date 

of the standard. (‘‘Section 112(i)(3)’s 


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three-year maximum compliance period 

applies generally to any emission 

standard . . . promulgated under 

[section 112].’’ Association of Battery 

Recyclers v. EPA, 716 F.3d 667, 672 

(D.C. Cir. 2013)). In determining what 

compliance period is as expeditious as 

practicable, we consider the amount of 

time needed to plan and construct 

projects and to change operating 

procedures. As provided in CAA section 

112(i) and 5 U.S.C. 801(3), all new 

affected sources that commenced 

construction or reconstruction after 

December 27, 2024 would be required to 

comply with these requirements upon 

the effective date of the final rule or 

upon startup, whichever is later. The 

EPA anticipates that the effective date of 

the final rule will be the publication 

date of the final rule. 

For fenceline monitoring, we are 

proposing at 40 CFR 63.1422(n) that 

owners and operators of all existing 

affected sources and all affected sources 

that were new under the current rule 

(i.e., sources that commenced 

construction or reconstruction after 

September 4, 1997, and on or before 

December 27, 2024) must begin 

fenceline monitoring 2 years after the 

effective date of the final rule and, 

starting 3 years after the effective date 

of the final rule, must perform root 

cause analysis and apply corrective 

action requirements upon exceedance of 

the annual average concentration action 

level. 

For all of the requirements we are 

proposing under CAA section 112(f), we 

are proposing at 40 CFR 63.1422(m) a 

compliance date of 2 years after the 

effective date of the final rule or upon 

startup, whichever is later, for all 

existing affected sources and for all 

affected sources that were new sources 

under the current PEPO NESHAP (i.e., 

they commenced construction or 

reconstruction after September 4, 1997, 

and on or before December 27, 2024), to 

comply with the proposed EtO 

requirements. For all new affected 

sources that commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with the EtO 

requirements upon the effective date of 

the final rule or upon startup, 

whichever is later. 

1. Rationale for Proposed Compliance 

Dates of Proposed CAA Sections 

112(d)(2) and (3) and 112(h) 

Amendments 

We are proposing new operating and 

monitoring requirements under CAA 

sections 112(d)(2) and (3) for PEPO 

flares. We anticipate that these 

provisions would require the 

installation of new flare monitoring 

equipment, and we project that most 

PMPUs would install new control 

systems to monitor and adjust assist gas 

(air or steam) addition rates. Similar to 

the addition of new control equipment, 

these new monitoring requirements for 

flares would require engineering 

evaluations, solicitation and review of 

vendor quotes, contracting and 

installation of the equipment, and 

operator training. Installation of new 

monitoring and control equipment on 

flares will require the flare to be taken 

out of service. Depending on the 

configuration of the flares and flare 

header system, taking the flare out of 

service may also require a significant 

portion of the PMPU to be shut down. 

Therefore, for all existing affected 

sources, and all new affected sources 

under the current PEPO NESHAP that 

commenced construction or 

reconstruction after September 4, 1997, 

and on or before December 27, 2024, we 

are proposing that it is necessary to 

provide 3 years after the effective date 

of the final rule (or upon startup, 

whichever is later) for owners or 

operators to comply with the new 

operating and monitoring requirements 

for flares. For all new affected sources 

that commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with the new 

operating and monitoring requirements 

for flares upon the effective date of the 

final rule or upon startup, whichever is 

later. 

Under CAA sections 112(d)(2) and (3), 

we are proposing new vent control 

requirements for bypasses. These 

requirements would typically require 

the addition of piping and potentially 

new control requirements. As owners or 

operators would most likely route these 

bypass emissions to a flare, we are 

proposing for all existing affected 

sources, and new affected sources under 

the current PEPO NESHAP that 

commenced construction or 

reconstruction after September 4, 1997, 

and on or before December 27, 2024, to 

provide 3 years after the effective date 

of the final rule (or upon startup, 

whichever is later) to allow for owners 

or operators to coordinate these bypass 

modifications with the installation of 

the new monitoring equipment for the 

flares. For all new affected sources that 

commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with the new vent 

control requirements for bypasses upon 

the effective date of the final rule or 

upon startup, whichever is later. 

We are also proposing to establish 

work practice standards in the PEPO 

NESHAP for maintenance activities. We 

anticipate that sources will need time 

to: review and update their standard 

operating procedures for maintenance 

activities; identify the most appropriate 

preventive measures or control 

approaches; design, install, and test the 

control systems; and install necessary 

process instrumentation and safety 

systems if so required. Therefore, for all 

existing affected sources, and all new 

affected sources under the current PEPO 

NESHAP that commenced construction 

or reconstruction after September 4, 

1997, and on or before December 27, 

2024, we are proposing a compliance 

date of 3 years after the effective date of 

the final rule (or upon startup, 

whichever is later) for owners or 

operators to comply with the work 

practice standards for maintenance 

activities. For all new affected sources 

that commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with the work practice 

standards for maintenance activities 

upon the effective date of the final rule 

or upon startup, whichever is later. 

Other amendments we are proposing 

under CAA sections 112(d)(2) and (3) 

include LDAR requirements for pressure 

vessels, process vent control 

requirements for certain surge control 

vessels and bottoms receivers, control 

requirements for certain transfer racks, 

the addition of butylene oxide to the 

definition of ‘‘epoxide’’ in 40 CFR 

63.1423(b) and to the list of HAP 

presented in table 4 to the PEPO 

NESHAP, and the removal of the 

exemption in 40 CFR 63.1420(d)(3) for 

reactions or processing that occur after 

completion of epoxide polymerization 

and all catalyst removal steps. We 

anticipate that any of these proposed 

provisions may require additional time 

to plan, purchase, and install equipment 

for emissions control; however, even if 

additional time is not needed, the EPA 

recognizes the confusion that multiple 

different compliance dates for 

individual requirements would create 

and the additional burden such an 

assortment of dates would impose. 

Therefore, for all existing affected 

sources, and all new affected sources 

under the current rules that commenced 

construction or reconstruction after 

September 4, 1997, and on or before 

December 27, 2024, we are proposing a 

compliance date of 3 years after the 

effective date of the final rule (or upon 

startup, whichever is later) for owners 

or operators to comply with these other 

proposed amendments. For all new 


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affected sources that commence 

construction or reconstruction after 

December 27, 2024, we are proposing 

that owners or operators comply with 

these other proposed amendments upon 

the effective date of the final rule or 

upon startup, whichever is later. 

2. Rationale for Proposed Compliance 

Dates of Proposed CAA Section 

112(d)(6) Amendments 

As a result of our technology review 

for PEPO heat exchange systems, we are 

proposing to replace the existing leak 

definition and monitoring method with 

a new leak definition and monitoring 

method. We project that some owners 

and operators would require 

engineering evaluations, solicitation and 

review of vendor quotes, contracting 

and installation of monitoring 

equipment, and operator training. In 

addition, facilities will need time to 

read and understand the amended rule 

requirements and to update standard 

operating procedures. Therefore, we are 

proposing that all existing affected 

sources, and all new affected sources 

under the current rule that commenced 

construction or reconstruction after 

September 4, 1997, and on or before 

December 27, 2024, must comply with 

the new monitoring requirements for 

heat exchange systems no later than 3 

years after the effective date of the final 

rule (or upon startup, whichever is 

later). For all new affected sources that 

commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with the new 

monitoring requirements for heat 

exchange systems upon the effective 

date of the final rule or upon startup, 

whichever is later. 

Under our technology review for 

PEPO storage vessels under CAA section 

112(d)(6), we are revising the PEPO 

NESHAP to reflect more stringent 

storage vessel capacity and MTVP 

thresholds. Although we did not find 

any PEPO storage vessels that would be 

affected by these proposed provisions, 

we believe it would be unnecessarily 

cumbersome to impose different 

compliance dates for these new storage 

vessel requirements. The EPA 

recognizes the confusion that multiple 

different compliance dates for 

individual requirements would create 

and the additional burden that such an 

assortment of dates would impose. 

Therefore, we are proposing that all 

existing affected sources, and all new 

affected sources under the current rules 

that commenced construction or 

reconstruction after September 4, 1997, 

and on or before December 27, 2024, 

must comply with the new storage 

vessel requirements no later than 3 

years after the effective date of the final 

rule (or upon startup, whichever is 

later). For all new affected sources that 

commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with the new storage 

vessel requirements upon the effective 

date of the final rule or upon startup, 

whichever is later. 

We are also proposing, pursuant to 

CAA section 112(d)(6), to remove the 

50-ppmv and 0.005-scmm Group 1 

process vent thresholds from the 

definition of ‘‘Group 1 continuous 

process vent’’ for continuous process 

vents associated with nonepoxide 

organic HAP and the Group 1 process 

vent applicability associated with a 

PMPU using THF, and to instead require 

owners and operators of these process 

vents that emit greater than or equal to 

1.0 lb/hr of total organic HAP to meet 

the current control standards in the 

PEPO NESHAP. Additionally, as a result 

of our technology review for PEPO 

Group 1 combination of batch process 

vents, we are proposing that owners and 

operators of batch process vents that 

release a total of annual organic HAP 

emissions greater than or equal to 4,536 

kg/yr (10,000 lb/yr) from all batch 

process vents combined reduce 

emissions of organic HAP from these 

process vents using a flare meeting the 

proposed operating and monitoring 

requirements for flares; or reduce 

emissions of organic HAP or TOC by 90- 

percent by weight. We project that some 

owners and operators will need to 

install new control equipment and/or 

new hard-piping or ductwork for certain 

process vents because of the proposed 

applicability revisions. The addition of 

new control equipment would require 

engineering design, solicitation, and 

review of vendor quotes, and 

contracting and installation of the 

equipment, which would need to be 

timed with process unit outage and 

operator training. Therefore, we are 

proposing that all existing affected 

sources, and all new affected sources 

under the current rules that commenced 

construction or reconstruction after 

September 4, 1997, and on or before 

December 27, 2024, must comply with 

the new process vent requirements no 

later than 3 years after the effective date 

of the final rule (or upon startup, 

whichever is later). For all new affected 

sources that commence construction or 

reconstruction after December 27, 2024 

we are proposing that owners or 

operators comply with the new process 

vent requirements upon the effective 

date of the final rule or upon startup, 

whichever is later. 

Compliance dates for the fenceline 

monitoring provisions proposed under 

CAA section 112(d)(6) consider the 

amount of time that it will take owners 

and operators to develop their siting 

plans and secure the capabilities to 

conduct the monitoring and analyze the 

results. For fenceline monitoring, the 

compliance timeline also must consider 

the timeline for controls addressing EtO 

emissions to be installed and 

operational before monitoring can begin 

to develop the annual average 

concentration baseline. After a year, if 

the annual average concentration 

exceeds the action level, root cause 

analysis and application of corrective 

measures can take place. Therefore, we 

are proposing that owners and operators 

of all existing sources and all new 

affected sources under the current rule 

that commenced construction or 

reconstruction after September 4, 1997, 

and on or before December 27, 2024 

must begin fenceline monitoring 2 years 

after the effective date of the final rule. 

The 2-year period provides owners and 

operators with time to: read and assess 

the new fenceline monitoring 

requirements; prepare sampling and 

analysis plans; develop and submit sitespecific monitoring plans; identify 

representative, accessible, and secure 

monitoring locations for offsite monitors 

and obtain permission from the property 

owner to both place and routinely 

access the monitors; make any necessary 

physical improvements to fenceline 

areas to accommodate site monitors, 

including construction of access roads, 

physical fencing, and potential drainage 

improvements; and obtain approval of 

any necessary capital expenditures. We 

are also proposing that owners and 

operators of such sources perform root 

cause analysis and apply corrective 

action requirements upon exceedance of 

an annual average concentration action 

level starting 3 years after the effective 

date of the final rule. 

For all new affected sources that 

commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators begin fenceline monitoring 

upon the effective date of the final rule 

or upon startup, whichever is later. We 

are also proposing to require quarterly 

reporting of fenceline results beginning 

1 year after monitoring begins for such 

sources. 

3. Rationale for Proposed Compliance 

Dates of Proposed CAA Section 112(f) 

Amendments 

As previously mentioned in this 

preamble, we are proposing, under CAA 


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section 112(f), new provisions 

considering results of the risk 

assessments to address emissions of EtO 

from equipment leaks, heat exchange 

systems, process vents, storage vessels, 

and wastewater at PEPO processes. CAA 

section 112(f)(4) prescribes the 

compliance date for emission standards 

issued under CAA section 112(f). Ass’n 

of Battery Recyclers v. EPA, 716 F.3d 

667, 672 (D.C. Cir. 2013) (‘‘[S]ection 

112(f)(4)’s two-year maximum applies 

more specifically to standards ‘under 

this subsection,’ i.e., section 112(f).’’). 

For existing sources, the earliest 

compliance date for CAA section 112(f) 

standards is 90 days after the effective 

date. However, the compliance period 

can be extended up to 2 years after the 

effective date if the EPA finds that more 

time is needed for the installation of 

controls and that steps will be taken 

during the period of the waiver to assure 

that the health of persons will be 

protected from imminent endangerment. 

42 U.S.C. 7412(f)(4)(B). The EPA 

anticipates that the proposed provisions 

will require additional time to plan, 

purchase, and install equipment for EtO 

control. For example, for PEPO process 

vents in EtO service, if the affected 

source cannot demonstrate 99.9-percent 

control of EtO emissions, or reduce EtO 

emissions to less than 1 ppmv (from 

each process vent) or 5 lb/yr (for all 

combined process vents), then the 

owner or operator would need to install 

a new control system, such as a scrubber 

with piping, ductwork, feed tanks, etc. 

Similarly, this same scenario (i.e., 

installation of a new control system) 

may be necessary for storage vessels in 

order to reduce EtO emissions by greater 

than or equal to 99.9 percent by weight 

or to a concentration of less than 1 

ppmv. Likewise, a new steam stripper 

may be needed to control wastewater 

with a total annual average 

concentration of EtO greater than or 

equal to 1 ppmw. Additional permits 

may be required for this new emission 

control equipment (e.g., New Source 

Review and/or title V permit 

modifications). In other words, the EPA 

anticipates that facilities will need 

sufficient time to properly engineer the 

project, obtain capital authorization and 

funding, procure the equipment, obtain 

permits, and construct and start up the 

equipment. Therefore, in the absence of 

any determination by the EPA that a 

PEPO affected source is presenting 

imminent endangerment, we are 

proposing a compliance date of 2 years 

after the effective date of the final rule 

or upon startup, whichever is later, for 

all existing affected sources, and all new 

affected sources under the current rule 

that commenced construction or 

reconstruction after September 4, 1997, 

and on or before December 27, 2024 to 

comply with the proposed EtO 

requirements. For all new affected 

sources that commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with the EtO 

requirements upon the effective date of 

the final rule or upon startup, 

whichever is later. 

4. Rationale for Proposed Compliance 

Dates of Other Proposed Amendments 

We are proposing electronic reporting 

requirements (see section IV.E.2 of this 

preamble) and we anticipate that 

facilities would need some time to 

successfully accomplish these reporting 

revisions, including time to read and 

understand the amended rule 

requirements, to make any necessary 

adjustments (including adjusting 

standard operating procedures), and to 

convert reporting mechanisms and 

install necessary hardware and software. 

We are also proposing to add control 

device operational and monitoring 

requirements for adsorbers that cannot 

be regenerated and regenerative 

adsorbers that are regenerated offsite 

(including a requirement to use dual 

adsorbent beds in series) (see section 

IV.E.5. of this preamble). We anticipate 

that facilities would need some time to 

purchase and install a second adsorber 

bed. As previously mentioned, the EPA 

recognizes the confusion that multiple 

different compliance dates for 

individual requirements would create 

and the additional burden that such an 

assortment of dates would impose. From 

our assessment of the timeframe needed 

for compliance with both the new 

proposed electronic reporting 

requirements for flare management 

plans, compliance reports, and 

performance evaluation reports, and the 

new proposed adsorber requirements, 

the EPA considers a period of 3 years 

after the effective date of the final rule 

to be the most expeditious compliance 

period practicable. Thus, we are 

proposing that all existing affected 

sources, and all new affected sources 

under the current rule that commenced 

construction or reconstruction after 

September 4, 1997, and on or before 

December 27, 2024 be in compliance 

with these revised requirements upon 

initial startup or within 3 years of the 

effective date of the final rule, 

whichever is later. For all new affected 

sources that commence construction or 

reconstruction after December 27, 2024, 

we are proposing that owners or 

operators comply with these revised 

requirements upon the effective date of 

the final rule or upon startup, 

whichever is later. However, we are 

proposing to provide 60 days after the 

effective date of the final rule (or upon 

startup, whichever is later) for owners 

or operators of all affected sources to 

comply with the requirement to submit 

performance test reports electronically 

according to the proposed procedures 

specified in 40 CFR 63.1439(e)(9)(iii). 

V. Summary of Cost, Environmental, 

and Economic Impacts 

A. What are the affected sources? 

There are 25 facilities subject to the 

PEPO NESHAP. The list of facilities is 

available in the document titled List of 

Facilities Subject to the PEPO NESHAP, 

which is available in the docket for this 

rulemaking. 

B. What are the air quality impacts? 

This proposed action would reduce 

HAP and VOC emissions from PEPO 

emission sources. We estimate that the 

proposed amendments to the NESHAP, 

excluding the proposed EtO emission 

standards, would reduce overall VOC 

and HAP emissions from the PEPO 

Production source category by 

approximately 164 and 157 tpy, 

respectively. Additionally, the proposed 

EtO emission standards are expected to 

reduce EtO emissions by approximately 

14 tpy. We note that these emissions 

reductions do not consider the potential 

excess emissions reductions from flares 

that could result from the proposed 

monitoring requirements; we estimate 

flare excess emissions reductions of 75 

tpy HAP and 281 tpy VOC. 

Considering secondary impacts (e.g., 

emission increases associated with 

supplemental fuel or additional 

electricity), the EPA estimates that the 

proposed action would result in 

additional emissions of 155 tpy of 

carbon monoxide (CO), 242,000 tpy of 

carbon dioxide (CO2), 188 tpy of 

nitrogen oxides (NOX) (including 4 tpy 

of nitrous oxide), 14 tpy of particulate 

matter, 1.0 tpy of sulfur dioxide (SO2), 

and a reduction of 996 tpy of methane 

emissions. More information about the 

estimated emission reductions and 

secondary impacts of this proposed 

action for the PEPO NESHAP can be 

found in the Economic Impact Analysis 

(EIA) accompanying this proposal and 

in documents referenced in sections 

IV.B through IV.D of this preamble. 

C. What are the cost impacts? 

The EPA estimates that this proposed 

action would cumulatively cost (in 2022 

dollars) approximately $31.0 million in 

total capital costs and $18.7 million per 

year in total annualized costs (including 


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88EPA Air Pollution Control Cost Manual— 

Section 3: VOC Controls; Section 3.1: VOC 

Recapture Controls, Carbon Adsorbers Calculation 

Spreadsheet. Retrieved from https://www.epa.gov/ 

economic-and-cost-analysis-air-pollutionregulations/cost-reports-and-guidance-air-pollution. 

October 2018. 

product recovery), based on our analysis 

of the proposed action described in 

sections IV.B through IV.D of this 

preamble. The present value (PV) of the 

estimated costs of this proposed rule, 

discounted at a 2 percent rate over the 

2026 to 2040 period, is estimated at 

$236 million with an estimated 

equivalent annualized value (EAV) of 

$18.4 million without product recovery. 

With product recovery, the PV is 

estimated at $235 million with an 

estimated EAV of $18.3 million. The 

overall difference caused by product 

recovery is relatively minor, at less than 

a 0.43 percent decrease in both the PV 

and EAV. 

Although the EPA does not factor in 

cost when setting a MACT floor level of 

control, we estimated the cost of the 

standards proposed pursuant to CAA 

sections 112(d)(2) and (3) and 112(h) to 

include in the cumulative costs of the 

proposed action. 

Table 13 of this preamble summarizes 

the results of the impact estimates for 

flares in the PEPO Production source 

category that control emissions from 

PEPO processes. 

TABLE 13—NATIONWIDE COST IMPACTS FOR FLARES IN THE PEPO PRODUCTION SOURCE CATEGORY THAT CONTROL

EMISSIONS FROM PEPO PROCESSES

Control description 

Total capital 

investment 

(million $) 

Total 

annualized 

costs 

(million $/yr) 

Flare Operational and Monitoring Requirements .................................................................................................... 11.5 2.82 

Work Practice Standards for Flares Operating Above Their Smokeless Capacity ................................................ 0.20 0.05 

Total .................................................................................................................................................................. 11.7 2.88 

For the proposed equipment opening 

work practice standard, discussed in 

section IV.D.3.a, we expect that all 

PEPO facilities already have standard 

procedures in place when performing 

equipment openings (at the very least 

for safety reasons), with the exception of 

one facility, which is a small business 

that is co-located with a HON facility 

and is already accounted for under the 

recent HON rulemaking (see 89 FR 

42932). As such, the only costs incurred 

are for recordkeeping after each nonconforming event. We estimated the 

annual costs to be $11,000 per year. 

We estimated the annual cost of the 

proposed storage vessel degassing work 

practice standard, discussed in section 

IV.D.3.b, to be $7,100. 

For the proposed requirement to 

control working emissions from storage 

vessels during routine maintenance, 

discussed in section IV.D.3.c, we 

determined that the total capital cost of 

a 55-gallon activated carbon drum with 

two connections, including piping and 

ductwork, is approximately $1,500, 

based on vendor quotes. Following the 

guidelines of the EPA Control Cost 

Manual,88 we estimated that the annual 

cost per PMPU is $259. Thus, we 

estimated the nationwide capital cost 

for removal of the 240-hour exemption 

provisions (except for vessel breathing 

losses) for the PEPO NESHAP would be 

$22,500 and the annualized costs would 

be $3,900. 

We estimate that the nationwide 

capital cost for the proposed pressure 

vessel LDAR requirements discussed in 

section IV.D.4 would be about $3,800 

and the annualized capital costs would 

be $3,500. 

We anticipate that the following 

proposed changes would impose 

minimal costs: prohibiting bypasses of 

the APCD (discussed in section IV.D.2); 

setting MACT standards for transfer 

racks (discussed in section IV.D.6); 

inclusion of butylene oxide in the 

definition of epoxide and the list of 

HAP in table 4 to the PEPO NESHAP 

(discussed in section IV.D.7). 

D. What are the economic impacts? 

The EPA conducted an EIA for this 

proposal, in a document titled 

Economic Impact Analysis, which is 

available in the docket for this action. 

The EIA contains two parts. The EPA 

calculated the economic impacts of the 

proposal on small entities as the 

percentage of total annualized costs 

incurred by affected ultimate parent 

owners to their revenues. This ratio 

provides a measure of the direct 

economic impact to ultimate parent 

owners of PEPO facilities while 

presuming no impact on consumers. We 

estimate that the only small business 

impacted by the proposal will incur 

total annualized costs of 0.68 percent of 

its revenue both with and without 

product recovery. The Regulatory 

Flexibility Act (RFA) section later in 

this preamble and the EIA for this 

proposed rulemaking provide more 

explanation of these economic impacts. 

E. What are the benefits? 

The emissions controls required by 

these rules are expected to reduce 

emissions of a number of HAP. The 

proposed amendments to the PEPO 

NESHAP, excluding the EtO emission 

standards and the new flare 

requirements, would reduce HAP 

emissions from PEPO sources by 

approximately 157 tpy. The proposed 

EtO emission standards are projected to 

reduce EtO emissions from PEPO 

processes by approximately 14 tpy. We 

also estimate that the proposed 

amendments to the NESHAP will 

reduce excess emissions of HAP from 

flares in the PEPO Production source 

category by an additional 75 tpy. 

Quantifying and monetizing the 

economic value of reducing the risk of 

cancer and non-cancer effects is made 

difficult by the lack of a central estimate 

of cancer and non-cancer risk and the 

lack of estimates of the value of an 

avoided case of cancer (fatal and nonfatal) and morbidity effects. Due to 

methodology and data limitations, we 

did not attempt to monetize the health 

benefits of reductions in HAP emissions 

in this analysis. With regard to 

emissions changes, the EPA is unable to 

assess the total costs, benefits, and 

distributional consequences of these 

actions at the community/neighborhood 

level. 

EtO is used in the production of 

PEPO. Health effects from acute (shortterm) exposure to EtO in humans 

consist mainly of central nervous 

system depression and irritation of the 

eyes and mucous membranes. Chronic 

(long-term) exposure to EtO in humans 

can cause irritation of the eyes, skin, 

nose, throat, and lungs, and damage to 

the brain and nervous system. There is 

also some evidence linking EtO 


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89ATSDR. Toxicological Profile for Ethylene 

Oxide. U.S. Department of Health and Human 

Services. 2022. Available at https:// 

www.atsdr.cdc.gov/toxprofiles/tp137.pdf. 

90 International Agency for Research on Cancer. 

Chemical Agents and Related Occupations. Volume 

100F, A Review of Human Carcinogens. 2012. 

Available at https://publications.iarc.fr/Book-AndReport-Series/Iarc-Monographs-On-TheIdentification-Of-Carcinogenic-Hazards-ToHumans/Chemical-Agents-And-RelatedOccupations-2012. 

91U.S. EPA. Guidelines for Carcinogen Risk 

Assessment. 2005. Available at https:// 

www.epa.gov/risk/guidelines-carcinogen-riskassessment. 

92U.S. EPA. Evaluation of the Inhalation 

Carcinogenicity of Ethylene Oxide. Integrated Risk 

Information System (IRIS) on Ethylene Oxide. 

National Center for Environmental Assessment, 

Washington DC. 2016. 

93U.S. EPA (2020). Integrated Science 

Assessment for Ozone and Related Photochemical 

Oxidants. U.S. EPA. Washington, DC. Office of 

Research and Development. EPA/600/R–20/012. 

Available at: https://www.epa.gov/isa/integratedscience-assessment-isa-ozone-and-relatedphotochemical-oxidants. 

94U.S. EPA. 2021. Technical Support Document 

(TSD) for the Final Revised Cross-State Air 

Pollution Rule Update for the 2008 Ozone Season 

NAAQS Estimating PM2.5- and Ozone-Attributable 

Health Benefits. https://www.epa.gov/sites/default/ 

files/2021-03/documents/estimating_pm2.5- 

_and_ozone-attributable_health_benefits_tsd.pdf. 

95Technical Guidance for Assessing 

Environmental Justice in Regulatory Analysis, U.S. 

EPA, June 2016. Quote is from Section 3—Key 

Analytic Considerations, page 11. 

96Note that there are 25 facilities identified as 

subject to the PEPO NESHAP. However, one of 

these facilities has a PEPO source still under 

construction and another facility did not have 

sufficient information to parse out the source 

category records. Therefore, only 23 facilities were 

included for the PEPO Production source category 

analyses. 

exposure to reproductive effects.89 The 

International Agency for Research on 

Cancer has classified EtO as a known 

human carcinogen.90 The EPA’s IRIS 

characterized EtO as ‘‘carcinogenic to 

humans’’ by the inhalation route of 

exposure based on the total weight of 

evidence (U.S. EPA, 2016), in 

accordance with the EPA’s Guidelines 

for Carcinogen Risk Assessment.91 The 

EPA concluded that there was strong, 

but less than conclusive on its own, 

epidemiological evidence of 

lymphohematopoietic cancers and 

breast cancer in EtO-exposed workers 

(U.S. EPA, 2016). People living near 

PEPO production facilities that emit EtO 

may have an increased risk of 

developing lymphoid cancers and, for 

females, breast cancer.92 We conclude 

that reducing EtO emissions from PEPO 

production facilities will significantly 

reduce the cancer risk for exposed 

populations (see sections IV.A.1 and 

IV.B.3 of this preamble). 

The emission controls installed to 

comply with these proposed rules are 

also expected to reduce VOC emissions 

which, in conjunction with NOX and in 

the presence of sunlight, form groundlevel ozone (O3). To assess O3-related 

human health impacts, the EPA consults 

the Integrated Science Assessment for 

Ozone (Ozone ISA) 93 as summarized in 

the Technical Support Document for the 

Final Revised Cross State Air Pollution 

Rule Update.94 In brief, the Ozone ISA 

found short-term (less than 1 month) 

exposures to ozone to be causally 

related to respiratory effects, a ‘‘likely to 

be causal’’ relationship with metabolic 

effects, and a ‘‘suggestive of, but not 

sufficient to infer, a causal relationship’’ 

for central nervous system effects, 

cardiovascular effects, and total 

mortality. The Ozone ISA reported that 

long-term exposures (1 month or longer) 

to ozone are ‘‘likely to be causal’’ for 

respiratory effects including respiratory 

mortality, and a ‘‘suggestive of, but not 

sufficient to infer, a causal relationship’’ 

for cardiovascular effects, reproductive 

effects, central nervous system effects, 

metabolic effects, and total mortality. 

F. What analysis of environmental 

justice did we conduct? 

For purposes of analyzing regulatory 

impacts, the EPA relies upon its June 

2016 Technical Guidance for Assessing 

Environmental Justice in Regulatory 

Analysis, which provides 

recommendations that encourage 

analysts to conduct the highest quality 

analysis feasible, recognizing that data 

limitations, time, resource constraints, 

and analytical challenges will vary by 

media and circumstance. The Technical 

Guidance states that a regulatory action 

may involve potential EJ concerns if it 

could: (1) create new disproportionate 

impacts on communities with EJ 

concerns; (2) exacerbate existing 

disproportionate impacts on 

communities with EJ concerns; or (3) 

present opportunities to address 

existing disproportionate impacts on 

communities with EJ concerns through 

this action under development. 

The EPA’s EJ technical guidance 

states that ‘‘[t]he analysis of potential EJ 

concerns for regulatory actions should 

address three questions: (A) Are there 

potential EJ concerns associated with 

environmental stressors affected by the 

regulatory action for population groups 

of concern in the baseline? (B) Are there 

potential EJ concerns associated with 

environmental stressors affected by the 

regulatory action for population groups 

of concern for the regulatory option(s) 

under consideration? (C) For the 

regulatory option(s) under 

consideration, are potential EJ concerns 

created or mitigated compared to the 

baseline?’’ 95

The EJ analysis is presented for the 

purpose of providing the public with as 

full as possible an understanding of the 

potential impacts of this proposed 

action. The EPA notes that analysis of 

such impacts is distinct from the 

determinations proposed in this action 

under CAA section 112, which are 

based solely on the statutory factors the 

EPA is required to consider under that 

section. 

1. PEPO Production Source Category 

Demographics 

For the PEPO Production source 

category, the EPA examined the 

potential for the 23 PEPO facilities (for 

which the EPA had HAP emissions 

inventories for emissions from the PEPO 

category) 96 to pose concerns to 

communities living in proximity to 

facilities, both in the baseline and under 

the control option proposed in this 

proposed action. Specifically, to 

examine the potential for EJ concerns, 

the EPA conducted three different 

demographic analyses of the 

populations living within 10 km and 50 

km of the PEPO facilities: a proximity 

analysis; a baseline cancer risk-based 

analysis (i.e., before implementation of 

any controls required by this proposed 

action); and a post-control cancer riskbased analysis (i.e., after 

implementation of the controls 

proposed to be required by this 

proposed action). In this preamble, we 

focus on the results from the 

demographic analyses using a 10 km 

radius because this area captures the 

majority of the population with higher 

cancer risks due to HAP emissions from 

PEPO facilities. Specifically, 100 

percent of the population with baseline 

cancer risks greater than or equal to 50- 

in-1 million from PEPO Production 

source category emissions lives within 

10 km of the PEPO facilities. The 

methodology and detailed results of the 

demographic analyses, including the 

demographic analyses for populations 

living within 50 km of facilities, are 

presented in the document titled 

Analysis of Demographic Factors for 

Populations Living Near Polyether 

Polyols (PEPO) Production Facilities— 

Source Category Analysis of Proposed 

Amendments, which is available in the 

docket for this rulemaking. 

For all three demographic analyses, 

the affected populations (i.e., those 

living within 10 km of the facilities) are 

compared to the national population. 

The total population, population 

percentages, and population count for 

each demographic group for the entire 

U.S. population are shown in the 

column titled ‘‘Nationwide Average for 


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Reference’’ in tables 14 through 16 of 

this preamble. These national data are 

provided as a frame of reference to 

compare the results of the proximity 

analysis, the baseline cancer risk-based 

analysis, and the post-control cancer 

risk-based analysis. 

Detailed results of the PEPO 

Production source category 

demographic analyses are located in 

subsections a (proximity analysis), b 

(baseline risk-based analysis), and c 

(post-control risk-based analysis) of this 

section V.F.1 of the preamble. The 

following paragraphs briefly summarize 

the results of these demographic 

analyses. 

The results of the proximity analysis 

indicate that a total of 1.4 million 

people live within 10 km of the 23 

PEPO facilities analyzed. The percent of 

the population living within 10 km of 

the PEPO facilities is above the 

corresponding national average for the 

following demographic groups: Black, 

Hispanic or Latino, people living below 

the poverty level, people living below 

two times the poverty level, people over 

the age of 25 without a high school 

diploma, and people that are age 0 to 17. 

The results of the proximity analysis 

indicate that the proportion of other 

demographic groups living within 10 

km of PEPO facilities is similar to or 

below the national average. The baseline 

cancer risk-based demographic analysis, 

which focuses on populations that have 

higher cancer risks, suggests that 

disparities exist for the same 

demographic groups as seen in the 

proximity analysis. 

The post-control risk-based 

demographic analysis shows that the 

controls proposed to be required by this 

proposed action would notably reduce 

the number of people who are exposed 

to cancer risks resulting from PEPO 

Production source category emissions at 

all risk levels. At greater than or equal 

to a cancer risk of 1-in-1 million, the 

number of individuals exposed would 

decrease from 834,000 to 592,000. The 

demographic composition of those 

individuals exposed to cancer risk 

greater than or equal to 1-in-1 million 

post-control is similar to the 

demographic composition of the 

individuals exposed to a cancer risk of 

1-in-1 million at baseline. At greater 

than or equal to a cancer risk of 50-in1 million, the number of individuals 

exposed would decrease from 28,000 to 

1,600. The demographic composition of 

those individuals exposed to cancer risk 

greater than or equal to 50-in-1 million 

post-control is above the corresponding 

national average for the following 

demographic groups: Black, Hispanic or 

Latino, age 0–17, people living below 

the poverty level, people living below 

two times the poverty level, and those 

over 25 without a high school 

education. After control is 

implemented, the number of people 

who are exposed to cancer risks greater 

than 100-in-1 million resulting from 

PEPO Production source category 

emissions would decrease from 3,300 to 

zero. Therefore, there are no disparities 

among demographic groups at this risk 

level. The actions of this proposed 

rulemaking would improve human 

health of current and future populations 

that live near these facilities. For more 

details see the remainder of this section 

V.F of the preamble. 

a. Proximity Analysis 

The column titled ‘‘Proximity 

Analysis for Population Living Within 

10 km of PEPO Facilities’’ in tables 14 

through 16 of this preamble shows the 

share and count of people for each of 

the demographic categories for the total 

population living within 10 km (∼6.2 

miles) of PEPO facilities. These are the 

results of the proximity analysis and are 

repeated in tables 14 through 16 of this 

preamble for easy comparison to the 

risk-based analyses discussed later in 

this preamble. 

Approximately 1.4 million people live 

within 10 km of the 23 PEPO facilities 

assessed. The results of the proximity 

demographic analysis indicate that the 

percentages of the population that is 

Black (13 percent, 192,000 people), 

Hispanic or Latino (22 percent, 320,000 

people) are higher than the national 

average (12 percent and 19 percent, 

respectively). The percentages of people 

living below the poverty level (14 

percent, 196,000 people) and below 2 

times the poverty level (31 percent, 

446,000 people) are also higher than the 

national average (14 percent and 31 

percent, respectively). In addition, the 

percentage of people over the age of 25 

without a high school diploma (14 

percent, 197,000 people) is higher than 

the national average (12 percent). The 

proximity analysis indicates that the 

proportion of other demographic groups 

living within 10 km of PEPO facilities 

is similar to or below the national 

average. 

b. Baseline Risk-Based Demographics 

The baseline risk-based demographic 

analysis results are shown in the 

‘‘baseline’’ column of tables 14 through 

16 of this preamble. This analysis 

focused on the populations living 

within 10 km (∼6.2 miles) of the PEPO 

facilities with estimated cancer risks 

greater than or equal to 1-in-1 million 

resulting from PEPO Production source 

category emissions (table 14 of this 

preamble), greater than or equal to 50- 

in-1 million (table 15 of this preamble), 

and greater than 100-in-1 million (table 

16 of this preamble). The risk analysis 

indicated that emissions from the source 

category, prior to the controls proposed 

to be required in this action, expose 

834,000 people living near 18 facilities 

to a cancer risk greater than or equal to 

1-in-1 million, 28,000 people living near 

10 facilities to a cancer risk greater than 

or equal to 50-in-1 million, and 3,300 

people living near 6 facilities to a cancer 

risk greater than 100-in-1 million. 

In the baseline, there are 834,000 

people living around 18 PEPO facilities 

with a cancer risk greater than or equal 

to 1-in-1 million resulting from PEPO 

Production source category emissions. 

The 18 PEPO facilities are located across 

7 States, but more than two-thirds (14 

facilities) of the facilities are located in 

Texas, West Virginia, and Louisiana. 

Ninety-seven percent of the people with 

risks greater than or equal to 1-in-1 

million live around these 14 PEPO 

facilities in Texas, West Virginia, and 

Louisiana. The overall percent of the 

baseline population with estimated 

cancer risks greater than or equal to 1- 

in-1 million who are Black (15 percent, 

129,000 people) is above the average 

percentage of the national population 

that is Black (12 percent). Around five 

PEPO facilities located in Louisiana, the 

percent of the population with cancer 

risks greater than or equal to 1-in-1 

million resulting from PEPO baseline 

source category emissions that is Black 

is more than two times the national 

average (greater than 24 percent). These 

five PEPO facilities account for about 

half of the Black population living 

within 10 km of PEPO facilities with 

risks greater than or equal to 1-in-1 

million resulting from PEPO Production 

source category baseline emissions. 

The overall percent of the population 

with cancer risks greater than or equal 

to 1-in-1 million resulting from PEPO 

Production source category baseline 

emissions that is Hispanic or Latino (26 

percent, 218,000 people) is higher than 

that in the baseline proximity analysis 

(22 percent, 320,000 people) and well 

above the national average (19 percent). 

Around three PEPO facilities located in 

Texas, the percent of the population that 

is Hispanic or Latino with cancer risks 

greater than or equal to 1-in-1 million 

resulting from PEPO baseline source 

category emissions is more than two 

times the national average. These three 

PEPO facilities account for over half of 

the Hispanic or Latino population living 

within 10 km of PEPO facilities with 

risks greater than or equal to 1-in-1 

million resulting from PEPO Production 

source category baseline emissions. The 


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percent of the population that is 

linguistically isolated with baseline 

cancer risks greater than or equal to 1- 

in-1 million is more than twice the 

national average for one of these three 

Texas facilities. The percent of the 

population that is American Indian or 

Alaskan Native or Other and Multiracial 

with risks greater than or equal to 1-in1 million resulting from PEPO 

Production source category baseline 

emissions is below the national average 

for all facilities. 

The percent of the population living 

below the poverty level and below two 

times the poverty level with cancer risks 

greater than or equal to 1-in-1 million 

resulting from PEPO baseline source 

category emissions (15 percent and 34 

percent, respectively) is above the 

national average (13 percent and 30 

percent, respectively). Around three 

facilities located in West Virginia, the 

percent of the population living below 

the poverty level and below two times 

the poverty level within 10 km of PEPO 

facilities with risks greater than or equal 

to 1-in-1 million resulting from PEPO 

Production source category baseline 

emissions is about 10 percent higher 

than the national average. The percent 

of the population over 25 years old 

without a high school diploma with 

cancer risks greater than or equal to 1- 

in-1 million resulting from PEPO 

Production source category baseline 

emissions (15 percent, 128,000 people) 

is greater than the national average (12 

percent). 

In the baseline, there are about 28,000 

people living around 10 PEPO facilities 

with a cancer risk greater than or equal 

to 50-in-1 million resulting from PEPO 

Production source category baseline 

emissions. These 10 PEPO facilities are 

located across 4 States (Louisiana, 

Texas, West Virginia, and Kentucky). 

Sixty percent of the people with risks 

greater than or equal to 50-in-1 million 

resulting from PEPO Production source 

category baseline emissions live within 

10 km of one facility, which is located 

in Louisiana. The overall percent of the 

population that is Black with baseline 

cancer risk greater than or equal to 50- 

in-1 million resulting from PEPO 

Production source category emissions 

(10 percent, 2,800 people) is below the 

national average (12 percent). However, 

around four PEPO facilities located in 

Louisiana and West Virginia, the 

percent of the population with cancer 

risks greater than or equal to 50-in-1 

million resulting from PEPO baseline 

source category emissions that is Black 

is more than two times the national 

average (greater than 24 percent). 

The overall percent of the population 

that is Hispanic or Latino with baseline 

cancer risk greater than or equal to 50- 

in-1 million resulting from PEPO 

Production source category emissions 

(10 percent, 2,700 people) is below the 

national average (19 percent). However, 

around two PEPO facilities located in 

Texas, the percent of the population 

with cancer risks greater than or equal 

to 50-in-1 million resulting from PEPO 

baseline source category emissions that 

is Hispanic or Latino is more than two 

times the national average (i.e., greater 

than 38 percent). The population near 

these two facilities in Texas accounts for 

about 77 percent of the number of 

Latino/Hispanic people with risks 

greater than or equal to 50-in-1 million 

resulting from the PEPO Production 

source category emissions. The percent 

of the population that is American 

Indian or Alaskan Native with risks 

greater than or equal to 50-in-1 million 

resulting from PEPO Production source 

category baseline emissions is below the 

national average for all facilities. The 

percent of the population that is Other 

or Multiracial with risks greater than or 

equal to 50-in-1 million resulting from 

PEPO Production source category 

baseline emissions is below the national 

average for all but one facility located in 

West Virginia. 

The percentage of the population with 

cancer risks resulting from PEPO 

Production source category baseline 

emissions greater than or equal to 50-in1 million that are below the poverty 

level (14 percent), below two times the 

poverty level (35 percent), and over 25 

years old without a high school diploma 

(16 percent) are above the respective 

national averages. Around four facilities 

located in West Virginia, the 

percentages of the population living 

below the poverty level and below two 

times the poverty level within 10 km of 

PEPO facilities with risks greater than or 

equal to 50-in-1 million resulting from 

PEPO Production source category 

baseline emissions are about 10 percent 

higher than the national average. 

In the baseline, there are 3,300 people 

living around 6 PEPO facilities with a 

cancer risk resulting from PEPO 

Production source category baseline 

emissions greater than 100-in-1 million. 

These six PEPO facilities are located in 

Texas, West Virginia and Louisiana. The 

percent of the population that is Black 

with cancer risk greater than 100-in-1 

million resulting from PEPO Production 

source category baseline emissions (14 

percent, 500 people) is above the 

national average (12 percent). Around 

two facilities in West Virginia, the 

percentage of the Black population with 

cancer risks greater than 100-in-1 

million resulting from PEPO Production 

source category emissions is over two 

times the national average. 

The percentage of the population that 

is Hispanic/Latino with risks greater 

than 100-in-1 million resulting from 

PEPO Production source category 

emissions (21 percent, 700 people) is 

above the national average (19 percent). 

The share of the Hispanic and Latino 

population with cancer risks greater 

than 100-in-1 million resulting from 

PEPO Production source category 

emissions is driven by one facility in 

Texas where the percent of the 

population that is Hispanic/Latino is 

over three times the national average. 

The percent of the population that is 

American Indian or Alaskan Native with 

risks greater than 100-in-1 million 

resulting from PEPO Production source 

category baseline emissions is well 

below the national average for all 

facilities. 

The percentages of the population 

with cancer risks greater than 100-in-1 

million resulting from PEPO Production 

source category baseline emissions that 

are below the poverty level (26 percent, 

900 people), below 2 times the poverty 

level (46 percent, 1,500 people), and 

over 25 without a high school diploma 

(30 percent, 1,000 people) are above the 

respective national averages. 

Around four facilities located in West 

Virginia and Louisiana, the percent of 

the population with cancer risks greater 

than 100-in-1 million resulting from 

PEPO Production source category 

baseline emissions that are below the 

poverty level is two to four times the 

national average. In addition, for two of 

these facilities located in West Virginia, 

the population with cancer risks greater 

than 100-in-1 million resulting from 

PEPO Production source category 

baseline emissions that are below two 

times the poverty level is two times the 

national average. 

In summary, the baseline risk-based 

demographic analysis, which focuses on 

populations that are expected to have 

higher cancer risks resulting from PEPO 

Production source category emissions, 

suggests that Blacks and Hispanic or 

Latino individuals are 

disproportionately overrepresented at 

cancer risk levels of greater than or 

equal to 1-in-1 million and greater than 

100-in-1 million. In addition, the 

baseline risk-based demographic 

analysis suggests that populations living 

below the poverty level and living 

below two times the poverty level are 

disproportionately overrepresented at 

all cancer risk levels. This 

disproportionate overrepresentation is 

the greatest in the population with 

cancer risks greater than 100-in-1 

million. 


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Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 106051 

c. Post-Control Risk-Based 

Demographics 

This analysis focused on the 

populations living within 10 km (∼6.2 

miles) of the facilities with estimated 

cancer risks greater than or equal to 1- 

in-1 million (table 14 of this preamble), 

greater than or equal to 50-in-1 million 

(table 15 of this preamble), and greater 

than 100-in-1 million (table 16 of this 

preamble) resulting from PEPO 

Production source category emissions 

after implementation of the proposed 

controls (‘‘post-control’’). The results of 

the post-control risk-based 

demographics analysis are in the 

column titled ‘‘Post-Control’’ of tables 

14 through 16 of this preamble. In this 

analysis, we evaluated how the 

projected EtO emission reductions of 

the proposed standards for PEPO 

processes described in this action affect 

the distribution of risks. This evaluation 

makes it possible to characterize the 

post-control risks and to evaluate 

whether the proposed action would 

create or mitigate potential EJ concerns 

as compared to the baseline. 

The risk analysis indicated that the 

number of people within 10 km of a 

facility exposed to risks greater than or 

equal to 1-in-1 million resulting from 

PEPO Production source category 

emissions (table 14 of this preamble) 

would be reduced from approximately 

834,000 people in the baseline to 

592,000 people after implementation of 

the PEPO controls in this proposal. The 

populations with a cancer risk greater 

than or equal to 1-in-1 million resulting 

from PEPO Production source category 

emissions are located around 18 

facilities in the baseline and 16 facilities 

for post-control. 

The post-control population living 

within 10 km of a facility with 

estimated cancer risks greater than or 

equal to 1-in-1 million resulting from 

PEPO Production source category 

emissions (table 14 of this preamble) has 

similar demographic percentages to the 

baseline population with risks greater 

than or equal to 1-in-1 million. 

However, the number of individuals 

with risks greater than or equal to 1-in1 million resulting from PEPO 

Production source category emissions 

would be reduced in each demographic. 

The percentage of the population with 

risks greater than or equal to 1-in-1 

million resulting from PEPO Production 

source category emissions that is Black 

is 3 percent higher in the post-control 

population (18 percent) than in the 

baseline population (15 percent). 

However, the number of Black 

individuals with risks at or above 1-in1 million would be reduced by almost 

25,000 people from 129,000 in the 

baseline to 105,000 in the post-control 

scenario. 

Similarly, the percentage of the 

population with risks greater than or 

equal to 1-in-1 million resulting from 

PEPO Production source category postcontrol emissions that is Hispanic/ 

Latino would still be above the national 

average (25 percent versus 19 percent), 

but the number of Hispanic/Latino 

individuals with risks at or above 1-in1 million would be reduced by about 

70,000 people from 218,000 in the 

baseline to 148,000 in the post-control 

scenario. 

The percent of the population that is 

American Indian or Alaskan Native with 

risks greater than or equal to 1-in-1 

million resulting from PEPO Production 

source category emissions (0.2 percent) 

is below the national average (0.6 

percent) in the post-control analysis and 

populations around all facilities are 

below the national average. The number 

of American Indians or Alaskan Natives 

with risks greater than or equal to 1-in1 million resulting from PEPO 

Production source category emissions 

would be reduced from 2,100 in the 

baseline to 1,200 in the post-control 

scenario. 

The percentages of the population 

with risks greater than or equal to 1-in1 million resulting from PEPO 

Production source category emissions 

below the poverty level (15 percent) and 

below two times the poverty level (34 

percent) are the same in the post-control 

scenario as in the baseline. However, 

the number of individuals with risks 

greater than or equal to 1-in-1 million 

resulting from PEPO Production source 

category emissions that are below the 

poverty level would be reduced by 

about 35,000 (from 125,000 to 91,000) 

and those below 2 times the poverty 

level is reduced by about 78,000 (from 

281,000 to 203,000). The percent of 

individuals over 25 years old without a 

high school diploma is 1 percent higher 

in the post-control scenario (16 percent) 

than in the baseline (15 percent), but the 

number of individuals with risks greater 

than or equal to 1-in-1 million resulting 

from PEPO Production source category 

emissions would be reduced by almost 

35,000, from 128,000 to 93,000. The 

percentage of the population that is in 

linguistic isolation with risks greater 

than or equal to 1-in-1 million resulting 

from PEPO Production source category 

emissions is the same in the postcontrol scenario (5 percent), but the 

number of individuals would be 

reduced by almost 11,000 compared to 

the baseline, from 38,000 to 27,000. 

The risk analysis indicated that the 

number of people living within 10 km 

of a facility and exposed to risks greater 

than or equal to 50-in-1 million 

resulting from PEPO Production source 

category emissions (table 15 of this 

preamble) would be reduced 

significantly, from 28,000 people in the 

baseline to 1,600 people after 

implementation of the controls in this 

proposal. This represents more than a 

90 percent reduction in the number of 

individuals with risk greater than or 

equal to 50-in-1 million when compared 

to the baseline. The populations living 

within 10 km of a facility and with a 

cancer risk greater than or equal to 50- 

in-1 million resulting from PEPO 

Production source category emissions 

are located around four facilities in the 

post-control scenario, six fewer facilities 

than in the baseline. These four 

facilities are located in Louisiana, 

Texas, and West Virginia (two facilities). 

The communities within 10 km of two 

of those facilities (in Louisiana and 

Texas) comprise over 80 percent of the 

population with risks greater than or 

equal to 50-in-1 million resulting from 

PEPO Production source category postcontrol emissions. 

The number of individuals with risks 

greater than or equal to 50-in-1 million 

would be reduced significantly for each 

demographic category in the postcontrol scenario. The percentage of the 

population with risks greater than or 

equal to 50-in-1 million resulting from 

PEPO Production source category 

emissions that is Black would increase 

from 10 percent in the baseline to 17 

percent in the post-control scenario, 

which is above the national average (12 

percent). However, the number of Black 

individuals with risks at or above 50-in1 million would be reduced from 2,800 

in the baseline to 300 post-control. 

Similarly, the percentage of the 

population with risks greater than or 

equal to 50-in-1 million resulting from 

PEPO Production source category 

emissions that is Hispanic/Latino would 

increase from 10 percent in the baseline 

to 25 percent post-control, but the 

number of Hispanic/Latino individuals 

with risks at or above 50-in-1 million 

would be reduced from 2,700 in the 

baseline to 400 post-control. The 

number of American Indians or Alaskan 

Natives with risks greater than or equal 

to 50-in-1 million resulting from PEPO 

Production source category emissions 

would be reduced from about 100 in the 

baseline to zero post-control. 

The percentages of the population 

with risks greater than or equal to 50- 

in-1 million resulting from PEPO 

Production source category post-control 

emissions whose income is below the 

poverty level (22 percent) and below 

two times the poverty level (42 percent) 


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106052 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

would be higher than from the baseline 

(14 percent and 35 percent, 

respectively). However, the number of 

individuals with risks greater than or 

equal to 50-in-1 million resulting from 

PEPO Production source category 

emissions that are below the poverty 

level would be reduced from by about 

3,700 people (from 4,100 to 400) and 

those below two times the poverty level 

would be reduced by about 9,200 people 

(from 9,900 to 700). The number of 

individuals with risks greater than or 

equal to 50-in-1 million resulting from 

PEPO Production source category 

emissions that are over 25 years old 

without a high school diploma or are 

linguistically isolated would also be 

greatly reduced post-control. 

The risk analysis indicated that the 

number of people living within 10 km 

of a facility with risks greater than 100- 

in-1 million resulting from PEPO 

Production source category emissions 

(table 16 of this preamble) would be 

reduced from 3,300 individuals in the 

baseline to zero individuals after 

application of the PEPO controls in this 

proposal. Therefore, for the post-control 

risk-based demographic results, there 

would be no ‘‘greater than 100-in-1 

million’’ demographic results to discuss. 

In summary, as shown in the postcontrol risk-based demographic 

analysis, the controls proposed to be 

required by this proposal would 

significantly reduce the number of 

people expected to have cancer risks 

greater than or equal to 1-in-1 million, 

greater than or equal to 50-in-1 million, 

and greater than 100-in-1 million 

resulting from PEPO Production source 

category emissions. Although the 

number of individuals with risks greater 

than or equal to 1-in-1 million would be 

reduced in the post-control scenario 

(reduced from 834,000 people to 

592,000 people), populations of Black 

individuals, Hispanic/Latino 

individuals, those living below the 

poverty level and two times the poverty 

level, and those over 25 without a high 

school diploma would remain 

disproportionately represented. 

Similarly, the number of individuals 

with risks greater than or equal to 50- 

in-1 million would be reduced 

significantly in the post-control scenario 

(reduced from 28,000 to 1,600), but the 

population of Black individuals, 

Hispanic/Latino individuals, those 

living below the poverty level and two 

times the poverty level, and those over 

25 without a high school diploma 

would remain disproportionately 

represented. Post-control, there would 

be no individuals with risks greater than 

100-in-1 million resulting from PEPO 

Production source category emissions 

(reduced from 3,300 people to 0 people). 

TABLE 14—SOURCE CATEGORY: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS WITH

CANCER RISK GREATER THAN OR EQUAL TO 1-IN-1 MILLION RESULTING FROM PEPO NESHAP SOURCE CATEGORY

EMISSIONS LIVING WITHIN 10 km OF FACILITIES TO THE NATIONAL AVERAGE AND PROXIMITY DEMOGRAPHICS

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis for 

total population living 

within 10 km of PEPO 

facilities 

Cancer risk ≥1-in-1 

million within 10 km of 

PEPO facilities 

Baseline Post-control 

Total Population ............................................................................................... 330M 1.4M 834K 592K 

Number of Facilities ......................................................................................... .................... 23 18 16 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

59% 

[847K] 

54% 

[450K] 

53% 

[313K] 

Black ................................................................................................................ 12% 

[40M] 

13% 

[192K] 

15% 

[129K] 

18% 

[105K] 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[3.3K] 

0.3% 

[2.1K] 

0.2% 

[1.2K] 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

22% 

[320K] 

26% 

[218K] 

25% 

[148K] 

Other and Multiracial ....................................................................................... 9% 

[29M] 

5% 

[68K] 

4% 

[34K] 

4% 

[26K] 

Age by Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

24% 

[345K] 

24% 

[204K] 

25% 

[147K] 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

61% 

[876K] 

61% 

[511K] 

61% 

[363K] 

Age ≥65 years ................................................................................................. 16% 

[53M] 

15% 

[210K] 

14% 

[118K] 

14% 

[83K] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

14% 

[196K] 

15% 

[125K] 

15% 

[91K] 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

31% 

[446K] 

34% 

[281K] 

34% 

[203K] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

14% 

[197K] 

15% 

[128K] 

16% 

[93K] 


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Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 106053 

TABLE 14—SOURCE CATEGORY: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS WITH

CANCER RISK GREATER THAN OR EQUAL TO 1-IN-1 MILLION RESULTING FROM PEPO NESHAP SOURCE CATEGORY

EMISSIONS LIVING WITHIN 10 km OF FACILITIES TO THE NATIONAL AVERAGE AND PROXIMITY DEMOGRAPHICS—Continued 

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis for 

total population living 

within 10 km of PEPO 

facilities 

Cancer risk ≥1-in-1 

million within 10 km of 

PEPO facilities 

Baseline Post-control 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

4% 

[59K] 

5% 

[38K] 

5% 

[27K] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 American Community Survey (ACS) 5-year block 

group averages. Total population count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 

TABLE 15—SOURCE CATEGORY: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS WITH

CANCER RISK GREATER THAN OR EQUAL TO 50-IN-1 MILLION RESULTING FROM PEPO NESHAP SOURCE CATEGORY EMISSIONS LIVING WITHIN 10 km OF FACILITIES TO THE NATIONAL AVERAGE AND PROXIMITY DEMOGRAPHICS

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis for 

total population living 

within 10 km of PEPO 

facilities 

Cancer risk ≥50-in-1 

million within 10 km of 

PEPO facilities 

Baseline Post-control 

Total Population ............................................................................................... 330M 1.4M 28K 1.6K 

Number of Facilities ......................................................................................... .................... 23 10 4 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

59% 

[847K] 

77% 

[22K] 

56% 

[900] 

Black ................................................................................................................ 12% 

[40M] 

13% 

[192K] 

10% 

[2.8K] 

17% 

[300] 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[3.3K] 

0.3% 

[<100] 

0.0% 

[0] 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

22% 

[320K] 

10% 

[2.7K] 

25% 

[400] 

Other and Multiracial ....................................................................................... 9% 

[29M] 

5% 

[68K] 

3% 

[900] 

3% 

[<100] 

Age by Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

24% 

[345K] 

23% 

[6.4K] 

29% 

[500] 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

61% 

[876K] 

57% 

[16.3K] 

57% 

[900] 

Age ≥65 years ................................................................................................. 16% 

[53M] 

15% 

[210K] 

20% 

[5.7K] 

15% 

[200] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

14% 

[196K] 

14% 

[4.1K] 

22% 

[300] 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

31% 

[446K] 

35% 

[9.9K] 

42% 

[700] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

14% 

[197K] 

16% 

[4.4K] 

32% 

[500] 


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106054 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 

TABLE 15—SOURCE CATEGORY: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS WITH

CANCER RISK GREATER THAN OR EQUAL TO 50-IN-1 MILLION RESULTING FROM PEPO NESHAP SOURCE CATEGORY EMISSIONS LIVING WITHIN 10 km OF FACILITIES TO THE NATIONAL AVERAGE AND PROXIMITY DEMOGRAPHICS—Continued 

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis for 

total population living 

within 10 km of PEPO 

facilities 

Cancer risk ≥50-in-1 

million within 10 km of 

PEPO facilities 

Baseline Post-control 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

4% 

[59K] 

2% 

[500] 

1% 

[<100] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 

• When the population being characterized is very small, the demographic distributions provided by the Census can be subject to a high level 

of uncertainty. To avoid implying a level of precision that is not supported by the data, when the population of an individual demographic is less 

than 100, we have indicated it on the demographic tables as <100. 

TABLE 16—SOURCE CATEGORY: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS WITH

CANCER RISK GREATER THAN 100-IN-1 MILLION RESULTING FROM PEPO NESHAP SOURCE CATEGORY EMISSIONS

LIVING WITHIN 10 KM OF FACILITIES TO THE NATIONAL AVERAGE AND PROXIMITY DEMOGRAPHICS

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis for 

total population living 

within 10 km of PEPO 

facilities 

Cancer risk >100-in-1 

million within 10 km of 

PEPO facilities 

Baseline Post-control 

Total Population ............................................................................................... 330M 1.4M 3.3K 0

Number of Facilities ......................................................................................... .................... 23 6 0 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

59% 

[847K] 

61% 

[2K] 

100% 

[0] 

Black ................................................................................................................ 12% 

[40M] 

13% 

[192K] 

14% 

[500] 

0% 

[0] 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[3.3K] 

0.0% 

[0] 

0.0% 

[0] 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

22% 

[320K] 

21% 

[700] 

0% 

[0] 

Other and Multiracial ....................................................................................... 9% 

[29M] 

5% 

[68K] 

5% 

[100] 

0% 

[0] 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

24% 

[345K] 

25% 

[800] 

0% 

[0] 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

61% 

[876K] 

58% 

[1.9K] 

0% 

[0] 

Age ≥65 years ................................................................................................. 16% 

[53M] 

15% 

[210K] 

17% 

[600] 

0% 

[0] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

14% 

[196K] 

26% 

[900] 

0% 

[0] 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

31% 

[446K] 

46% 

[1.5k] 

0% 

[0] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

14% 

[197K] 

30% 

[1k] 

0% 

[0] 


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Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 106055 

TABLE 16—SOURCE CATEGORY: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS WITH

CANCER RISK GREATER THAN 100-IN-1 MILLION RESULTING FROM PEPO NESHAP SOURCE CATEGORY EMISSIONS

LIVING WITHIN 10 KM OF FACILITIES TO THE NATIONAL AVERAGE AND PROXIMITY DEMOGRAPHICS—Continued 

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis for 

total population living 

within 10 km of PEPO 

facilities 

Cancer risk >100-in-1 

million within 10 km of 

PEPO facilities 

Baseline Post-control 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

4% 

[59K] 

1% 

[<100] 

0% 

[0] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 

2. PEPO Production Whole-Facility 

Demographics 

As described in section III.B.7 of this 

preamble, we assessed the facility-wide 

(or ‘‘whole-facility’’) risks for 25 PEPO 

facilities in order to compare the PEPO 

Production source category risk to the 

whole-facility risks, accounting for HAP 

emissions from the entire major source 

and not just those resulting from PEPO 

Production source category emissions at 

the major source as discussed in the 

previous section (V.F.1). The wholefacility risk analysis includes all sources 

of HAP emissions at each facility as 

reported in the NEI (described in section 

III.B of this preamble). Since PEPO 

facilities tend to include HAP emissions 

sources from many source categories, 

the EPA conducted a whole-facility 

demographic analysis focused on postcontrol risks. This whole-facility 

demographic analysis characterizes the 

remaining risks that communities would 

face after implementation of the controls 

proposed to be required in this proposal 

(i.e., post-control). 

The whole-facility demographic 

analysis is an assessment of individual 

demographic groups in the total 

population living within 10 km (∼6.2 

miles) and 50 km (∼31 miles) of the 

facilities. In this preamble, we focus on 

the results from the demographic 

analyses using a 10 km radius because 

this area captures the majority of the 

population with higher cancer risks due 

to HAP emissions from PEPO facilities. 

Specifically, 100 percent of the 

population with baseline cancer risks 

greater than or equal to 50-in-1 million 

from PEPO Production source category 

emissions lives within 10 km of the 

PEPO facilities. The results of the 

whole-facility demographic analysis for 

populations living within 50 km are 

included in the document titled 

Analysis of Demographic Factors for 

Populations Living Near Polyether 

Polyols (PEPO) Production Facilities— 

Whole Facility Analysis of Proposed 

Amendments, which is available in the 

docket for this rulemaking. 

The whole-facility demographic 

analysis post-control results are shown 

in table 17 of this preamble. This 

analysis focused on the populations 

living within 10 km of the PEPO 

facilities with estimated whole-facility 

post-control cancer risks greater than or 

equal to 1-in-1 million, greater than or 

equal to 50-in-1 million, and greater 

than 100-in-1 million. The risk analysis 

indicated that all emissions from the 

PEPO facilities, after the reductions 

proposed to be imposed by the proposed 

rule, would expose a total of about 1 

million people living around 22 

facilities to a cancer risk greater than or 

equal to 1-in-1 million, 13,000 people 

living around 12 facilities to a cancer 

risk greater than or equal to 50-in-1 

million, and about 200 people living 

around 1 facility to a cancer risk greater 

than 100-in-1 million. 

When the PEPO whole-facility 

populations are compared to the PEPO 

Production source category populations 

in the post-control scenarios, we see 

400,000 additional people with risks 

greater than or equal to 1-in-1 million, 

11,000 additional people with risks 

greater than or equal to 50-in-1 million, 

and 200 additional people with risks 

greater than 100-in-1 million. 

The demographic distribution of the 

whole-facility population with postcontrol cancer risks greater than or 

equal to 1-in-1 million is similar to the 

distribution of the source category 

population with post-control cancer 

risks greater than or equal to 1-in-1 

million. Therefore, the whole-facility 

population with post-control cancer 

risks greater than or equal to 1-in-1 

million has disproportionately high 

representation from Blacks, Hispanics 

and Latinos, people living below the 

poverty level, people living below two 

times the poverty level, and those over 

25 without a high school education. 

The population with post-control 

cancer risks greater than or equal to 50- 

in-1 million in the whole-facility 

analysis has a much different 

demographic distribution than the 

source category population with postcontrol cancer risks greater than or 

equal to 50-in-1 million. The percent of 

the population that is Black with risks 

greater than or equal to 50-in-1 million 

is lower for the whole-facility postcontrol analysis (9 percent) versus the 

category post-control analysis (17 

percent) and is therefore below the 

national average (12 percent). The lower 

representation of the Black population 

is reflected in slightly higher (1 to 2 

percent) greater representation of the 

other races/ethnicities. As such, the 

Hispanic and Latino population is still 

disproportionately represented at 27 

percent, which is well above the 

national average of 19 percent. The 

percentage of the population with risks 

greater than or equal to 50-in-1 million 

that is below the poverty level (8 

percent) and below two times the 

poverty level (21 percent) is about half 

that for the whole-facility post-control 

population than for the category postcontrol population. This means that the 

whole-facility population is below the 

national average for both poverty 

demographics. 

Based on results from the wholefacility emissions analysis, there would 

be about 200 people with post-control 

risks greater than 100-in-1 million. 

Earlier in this preamble, we showed that 


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the PEPO Production source category 

emissions analysis indicated that there 

would be no people with post-control 

risks greater than 100-in-1 million. The 

increased cancer risk for most of these 

200 people is driven by EtO emissions 

from non-PEPO processes (HON, MON, 

and R&D Testing) co-located at PEPO 

facilities. 

The percent of the population in the 

whole-facility analysis with post-control 

risks greater than 100-in-1 million that 

is Black (26 percent, <100 people) is 

more than double the national average 

(12 percent). In addition, the 

percentages of the population in the 

whole-facility analysis with a postcontrol risk greater than 100-in-1 

million that are below the poverty level 

(21 percent, <100 people), below 2 times 

the poverty level (44 percent, <100 

people), and over 25 years old without 

a high school diploma (25 percent, <100 

people) are all above the national 

average (13 percent, 30 percent and 12 

percent, respectively). 

TABLE 17—WHOLE FACILITY: WHOLE-FACILITY POST-CONTROL DEMOGRAPHICS FOR PEPO PRODUCTION FACILITIES BY

RISK LEVEL FOR POPULATIONS LIVING WITHIN 10 km OF FACILITIES

Demographic group Nationwide 

Post-control cancer risk for populations within 

10 km of PEPO facilities 

≥1-in-1 

million 

≥50-in-1 

million 

>100-in-1 

million 

Total Population ............................................................................................... 329,824,950 1M 13K 200 

Number of Facilities ......................................................................................... ........................ 22 12 1 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

52% 

[520K] 

59% 

[7.6K] 

61% 

[<100] 

Black ................................................................................................................ 12% 

[40M] 

15% 

[149K] 

9% 

[1.2K] 

26% 

[<100] 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[2K] 

0.6% 

[<100] 

0.0% 

[0] 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

28% 

[282K] 

27% 

[3.5K] 

10% 

[<100] 

Other and Multiracial ....................................................................................... 9% 

[29M] 

5% 

[49K] 

4% 

[500] 

3% 

[<100] 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

25% 

[249K] 

21% 

[2.7K] 

13% 

[<100] 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

62% 

[616K] 

62% 

[7.9K] 

58% 

[<100] 

Age ≥65 years .................................................................................................. 16% 

[53M] 

14% 

[135K] 

17% 

[2.2K] 

29% 

[<100] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

14% 

[144K] 

8% 

[1.1K] 

21% 

[<100] 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

32% 

[320K] 

21% 

[2.7K] 

44% 

[<100] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

15% 

[150K] 

16% 

[2K] 

25% 

[<100] 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

5% 

[53K] 

2% 

[300] 

2% 

[<100] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. 

• As indicated in the table there is only one facility with an MIR above 100-in-1 million in the whole-facility post-control analysis (75 people). 

However, emissions of two other facilities (located next to each other) impact one census block and yield additional population above 100-in-1 

million (78 people). Thus, 75 + 78 = 153 people with risks greater than 100-in-1 million. In addition, not shown in the table, is a facility where the 

MIR was located at a cluster of residences with a user assigned receptor and was not located at a census block centroid. Population data are 

only provided by the Census Bureau at census blocks, therefore, the number of people living at the households was estimated manually and demographic data were not available. We estimate that there are an additional 60 people exposed to risks greater than 100-in-1 million living 

around this facility, bringing the total to about 200 people for whole-facility risks. 


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• When the population being characterized is very small, the demographic distributions provided by the Census can be subject to a high level 

of uncertainty. To avoid implying a level of precision that is not supported by the data, when the population of an individual demographic is less 

than 100, we have indicated it on the demographic tables as <100. 

3. PEPO Production Community 

Demographics 

As described in section III.B.8 of this 

preamble, we assessed the communitybased risks for 25 PEPO facilities in 

order to compare the PEPO Production 

source category risk to the community 

risks. The community risks include 

HAP emissions from all major stationary 

sources within 10 km of the PEPO 

facilities as reported in the NEI 

(described in section III.B of this 

preamble). The discussion of the 

community risk analysis is focused on 

post-control risks. This community 

demographic analysis characterizes the 

remaining risks that communities would 

face after implementation of the controls 

proposed to be required in this 

proposal. 

The community demographic analysis 

is an assessment of individual 

demographic groups in the total 

population living within 10 km (∼6.2 

miles) of the PEPO facilities. The 

community risk assessment and 

demographics were only conducted at 

the 10 km radius because, based on 

PEPO category emissions, this distance 

includes 100 percent of the population 

with cancer risks greater than or equal 

to 50-in-1 million. The full results of the 

community demographic analysis are in 

the document titled Analysis of 

Demographic Factors for Populations 

Living Near Polyether Polyols (PEPO) 

Production Facilities—CommunityBased Assessment, which is available in 

the docket for this rulemaking. 

The community demographic analysis 

post-control results are shown in table 

18 of this preamble. This analysis 

focused on the populations living 

within 10 km of the PEPO facilities with 

estimated community post-control 

cancer risks greater than or equal to 1- 

in-1 million, greater than or equal to 50- 

in-1 million, and greater than 100-in-1 

million. The risk analysis indicated that 

all emissions from all facilities within 

10 km of the PEPO facilities, after the 

reductions proposed to be imposed by 

the proposed rule, would expose a total 

of about 1.1 million people living 

around 25 facilities to a cancer risk 

greater than or equal to 1-in-1 million, 

66,000 people living around 20 facilities 

to a cancer risk greater than or equal to 

50-in-1 million, and about 500 people 

living around 8 facilities to a cancer risk 

greater than 100-in-1 million. 

When the PEPO community 

populations are compared to the PEPO 

Production source category populations 

in the post-control scenarios, we see 

500,000 additional people with risks 

greater than or equal to 1-in-1 million, 

64,000 additional people with risks 

greater than or equal to 50-in-1 million, 

and 500 additional people with risks 

greater than 100-in-1 million. 

The demographic distribution of the 

community population with cancer 

risks greater than or equal to 1-in-1 

million is very similar to the category 

population and the whole-facility 

population with cancer risks greater 

than or equal to 1-in-1 million in the 

post-control scenario. Therefore, the 

community population with postcontrol cancer risks greater than or 

equal to 1-in-1 million has 

disproportionately high representation 

from Blacks, Hispanics and Latinos, 

people living below the poverty level, 

people living below two times the 

poverty level, and those over 25 without 

a high school education. 

The population with cancer risks 

greater than or equal to 50-in-1 million 

in the community analysis has a much 

different demographic distribution than 

the source category population with 

cancer risks greater than or equal to 50- 

in-1 million in the post-control scenario. 

The percent of the population that is 

Black with risks greater than or equal to 

50-in-1 million is lower for the 

community post-control analysis (7 

percent) versus the category post-control 

analysis (17 percent). The lower 

representation of the Black population 

is reflected in greater representation of 

the other races/ethnicities. In particular, 

the percent of the population that is 

Hispanic or Latino is considerably 

disproportionately represented at 33 

percent, which is significantly above the 

national average of 19 percent. The 

percentage of the population with risks 

greater than or equal to 50-in-1 million 

that is below the poverty level, below 

two times the poverty level, or over 25 

years old without a high school diploma 

is about half that for the community 

post-control population than for the 

category post-control population. 

Based on results from the community 

emissions analysis, there are about 500 

people with post-control risks greater 

than 100-in-1 million. The PEPO 

Production source category emissions 

analysis indicated that there are no 

people with post-control risks greater 

than 100-in-1 million. The increased 

cancer risk for most of these 500 people 

is driven largely by EtO emissions from 

non-PEPO processes (HON, MON, and 

R&D Testing) at PEPO facilities and 

other facilities within 10 km of PEPO 

facilities. 

The percent of the population in the 

community analysis with post-control 

risks greater than 100-in-1 million that 

is Black (16 percent, <100 people) is 

above the national average (12 percent). 

The percent of the population in the 

community analysis with a post-control 

risk greater than 100-in-1 million that is 

below the poverty level (12 percent, 

<100 people) and below 2 times the 

poverty level (26 percent, 100 people) is 

below the national average (13 percent 

and 30 percent, respectively). The 

percent of the population in the 

community analysis with a post-control 

risk greater than 100-in-1 million that is 

over 25 years old without a high school 

diploma (16 percent, <100 people) is 

above the national average (12 percent). 

TABLE 18—COMMUNITY: COMMUNITY POST-CONTROL DEMOGRAPHICS FOR PEPO FACILITIES BY RISK LEVEL FOR

POPULATIONS LIVING WITHIN 10 KM OF FACILITIES

Demographic group Nationwide 

Post-control cancer risk for populations within 

10 km of PEPO facilities 

≥1-in-1 

million 

≥50-in-1 

million 

>100-in-1 

million 

Total Population ............................................................................................... 329,824,950 1.1M 66K 500 

Number of Facilities ......................................................................................... ........................ 25 20 8 


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97Children’s Health Policy. Available at: https:// 

www.epa.gov/children/childrens-health-policy-andplan. 

98U.S. EPA. 2005. Supplemental Guidance for 

Assessing Susceptibility from Early-Life Exposure to 

Carcinogens. U.S. EPA, Washington, DC, EPA/630/ 

R–03/003F. https://www.epa.gov/sites/default/files/ 

2013-09/documents/ 

childrens_supplement_final.pdf. 

TABLE 18—COMMUNITY: COMMUNITY POST-CONTROL DEMOGRAPHICS FOR PEPO FACILITIES BY RISK LEVEL FOR

POPULATIONS LIVING WITHIN 10 KM OF FACILITIES—Continued 

Demographic group Nationwide 

Post-control cancer risk for populations within 

10 km of PEPO facilities 

≥1-in-1 

million 

≥50-in-1 

million 

>100-in-1 

million 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

53% 

[611K] 

53% 

[35K] 

64% 

[300] 

Black ................................................................................................................ 12% 

[40M] 

15% 

[169K] 

7% 

[4.8K] 

16% 

[<100] 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[2.6K] 

0.3% 

[200] 

0.0% 

[0] 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

27% 

[306K] 

33% 

[22K] 

19% 

[<100] 

Other and Multiracial ....................................................................................... 9% 

[29M] 

5% 

[55K] 

6% 

[4.2K] 

2% 

[<100] 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

25% 

[283K] 

25% 

[16K] 

22% 

[100] 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

62% 

[705K] 

61% 

[41K] 

57% 

[300] 

Age ≥65 years .................................................................................................. 16% 

[53M] 

14% 

[156K] 

14% 

[9.4K] 

21% 

[100] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

15% 

[175K] 

10% 

[6.3K] 

12% 

[<100] 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

34% 

[384K] 

23% 

[15K] 

26% 

[100] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

16% 

[183K] 

14% 

[9K] 

16% 

[100] 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

5% 

[57K] 

4% 

[2.7K] 

1% 

[<100] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. 

• Not shown in the table is a facility where the MIR was located at a cluster of residences with a user assigned receptor and was not located 

at a census block centroid. Population data are only provided by the Census Bureau at census blocks, therefore, the number of people living at 

the households was estimated manually and demographic data were not available. We estimate that there are an additional 60 people exposed 

to risks greater than 100-in-1 million living around this facility, bringing the total to about 600 people for Community risks.

• When the population being characterized is very small, the demographic distributions provided by the Census can be subject to a high level 

of uncertainty. To avoid implying a level of precision that is not supported by the data, when the population of an individual demographic is less 

than 100, we have indicated it on the demographic tables as <100. 

G. What analysis of children’s 

environmental health did we conduct? 

This action proposes to address risk 

from EtO. In addition, the EPA’s Policy 

on Children’s Health 97 also applies to 

this action. Accordingly, we have 

evaluated the environmental health or 

safety effects of EtO emissions and 

exposures on children. 

Because EtO is mutagenic (i.e., it can 

damage deoxyribonucleic acid, DNA), 

children are expected to be more 

susceptible to its harmful effects. To 

take this into account, as part of the risk 

assessment in support of this 

rulemaking, the EPA followed its 

guidelines 98 and applied age-dependent 

adjustment factors (ADAF) for 

childhood exposures (from birth up to 

16 years of age). With the ADAF applied 

to account for greater susceptibility of 

children, the adjusted EtO inhalation 


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URE is 5 × 10¥3 per mg/m3. We note 

that, because EtO is mutagenic, 

emission reductions proposed in this 

action would be particularly beneficial 

to children. The results of the risk 

assessment are contained in sections 

IV.A and IV.B of this preamble and 

further documented in the risk report, 

Residual Risk Assessment for the 

Polyether Polyols (PEPO) Production 

Source Category in Support of the 2024 

Risk and Technology Review Proposed 

Rule, which is available in the docket 

for this rulemaking. 

VI. Request for Comments 

We solicit comments on this proposed 

action. In addition to general comments 

on this proposed action, we are also 

interested in additional data that may 

improve the risk assessments and other 

analyses. We are specifically interested 

in receiving any information regarding 

developments in practices, processes, 

and control technologies that reduce 

emissions. We are also interested in 

receiving information on costs, 

emissions, and product recovery, and 

we request comment on how to address 

the non-monetized costs and benefits of 

the proposed rule. We request comment 

on data and approaches to monetize the 

health benefits of reducing exposure to 

EtO and other HAP emitted from PEPO 

sources. 

VII. Submitting Data Corrections 

The site-specific emissions profiles 

used in the source category risk and 

demographic analyses and instructions 

are available for download on the 

project website at https://www.epa.gov/ 

stationary-sources-air-pollution/ 

polyether-polyols-production-nationalemission-standards-hazardous. The 

data files include detailed information 

for each HAP emissions release point for 

the facilities in the source category. 

If you believe that the data are not 

representative or are inaccurate, please 

identify the data in question, provide 

your reason for concern, and provide 

any ‘‘improved’’ data that you have, if 

available. When you submit data, we 

request that you provide documentation 

of the basis for the revised values to 

support your suggested changes. To 

submit comments on the data 

downloaded from the project website, 

complete the following steps: 

1. Within this downloaded file, enter 

suggested revisions to the data fields 

appropriate for that information. 

2. Gather documentation for any 

suggested emissions revisions (e.g., 

performance test reports, material 

balance calculations). 

3. Send the entire downloaded file 

with suggested revisions and all 

accompanying documentation to Docket 

ID No. EPA–HQ–OAR–2023–0282 

(through the method described in the 

ADDRESSES section of this preamble). 

5. If you are providing comments on 

a single facility or multiple facilities, 

you need only submit one file for all 

facilities. The file should contain all 

suggested changes for all sources at that 

facility (or facilities). 

VIII. Statutory and Executive Order 

Reviews 

Additional information about these 

statutes and Executive orders can be 

found at https://www.epa.gov/lawsregulations/laws-and-executive-orders. 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 14094: Modernizing Regulatory 

Review 

This action is not a significant 

regulatory action as defined in 

Executive Order 12866, as amended by 

Executive Order 14094, and was 

therefore not subject to a requirement 

for Executive Order 12866 review. 

B. Paperwork Reduction Act (PRA) 

The information collection activities 

in this proposed rule have been 

submitted for approval to the OMB 

under the PRA. The information 

collection request (ICR) document that 

the EPA prepared has been assigned 

EPA ICR number 1811.13. You can find 

a copy of the ICR in the docket for this 

rulemaking, and it is briefly 

summarized here. 

In this action, the EPA is proposing to 

add new monitoring and operational 

requirements for flares, add work 

practice standards for startup and 

shutdown periods for maintenance 

vents and planned routine maintenance 

of storage vessels, clarify regulatory 

provisions for vent control bypasses, 

add new monitoring requirements for 

PEPO pressure vessels, add new 

emission standards for PEPO surge 

control vessels and bottoms receivers, 

and add new emission standards for 

PEPO transfer operations. The EPA is 

also proposing to require control of EtO 

emissions from process vents, storage 

vessels, equipment leaks, heat exchange 

systems, and wastewater in EtO service. 

In addition, the EPA is proposing 

amendments to the PEPO NESHAP that 

add requirements for electronic 

reporting of periodic reports and 

performance test results, add 

requirements for fenceline monitoring, 

and make other minor clarifications and 

corrections. This information will be 

collected to ensure compliance with the 

PEPO NESHAP. 

Respondents/affected entities: 

Owners or operators of PEPO 

production facilities. 

Respondent’s obligation to respond: 

Mandatory (40 CFR part 63, subpart 

PPP). 

Estimated number of respondents: 27 

(assumes 2 new respondents over the 

next 3 years). 

Frequency of response: Initially, 

semiannually, and annually. 

Total estimated burden: 12,000 hours 

(per year). Burden is defined at 5 CFR 

1320.3(b). 

Total estimated cost: Average annual 

cost is $12,800,000 (per year) which 

includes $11,600,000 annualized capital 

or operation & maintenance costs. 

An agency may not conduct or 

sponsor, and a person is not required to 

respond to, a collection of information 

unless it displays a currently valid OMB 

control number. The OMB control 

numbers for the EPA’s regulations in 40 

CFR are listed in 40 CFR part 9. 

Submit your comments on the 

Agency’s need for this information, the 

accuracy of the provided burden 

estimates, and any suggested methods 

for minimizing respondent burden to 

the EPA using the docket identified at 

the beginning of this rulemaking. The 

EPA will respond to any ICR-related 

comments in the final rule. You may 

also send your ICR-related comments to 

OMB’s Office of Information and 

Regulatory Affairs using the interface at 

https://www.reginfo.gov/public/do/ 

PRAMain. Find this particular 

information collection by selecting 

‘‘Currently under Review—Open for 

Public Comments’’ or by using the 

search function. OMB must receive 

comments no later than January 27, 

2025. 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the RFA. We identified that one 

of the 25 facilities in the PEPO 

Production source category affected by 

this proposed action is a small business. 

This facility is subject to the PEPO 

NESHAP because it receives and treats 

wastewater from a PEPO production 

facility. The EIA conducted for this 

proposal (see Economic Impact 

Analysis, which is available in the 

docket for this action) showed that this 

small business will not incur total 

annualized costs greater than one 

percent of its revenue. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain an 

unfunded mandate of $100 million or 


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more (adjusted for inflation) as 

described in UMRA, 2 U.S.C. 1531– 

1538, and does not significantly or 

uniquely affect small governments. The 

costs involved in this action are 

estimated not to exceed $176 million in 

2022$ ($100 million in 1995$ adjusted 

for inflation using the gross domestic 

product implicit price deflator) or more 

in any one year. 

E. Executive Order 13132: Federalism 

This action does not have federalism 

implications. It will not have substantial 

direct effects on the States, on the 

relationship between the National 

Government and the Sstates, or on the 

distribution of power and 

responsibilities among the various 

levels of government. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have Tribal 

implications as specified in Executive 

Order 13175. None of the facilities that 

have been identified as being affected by 

this action are owned or operated by 

Tribal governments or are located 

within Tribal lands. Thus, Executive 

Order 13175 does not apply to this 

action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

Executive Order 13045 directs Federal 

agencies to include an evaluation of the 

health and safety effects of the planned 

regulation on children in Federal health 

and safety standards and explain why 

the regulation is preferable to 

potentially effective and reasonably 

feasible alternatives. While the 

environmental health or safety risks 

addressed by this action present a 

disproportionate risk to children 

because EtO is mutagenic (i.e., EtO can 

damage DNA), this action is not subject 

to Executive Order 13045 because it is 

not a significant regulatory action under 

section 3(f)(1) of Executive Order 12866. 

However, the EPA’s Policy on Children’s 

Health applies to this action. 

Information on how the Policy was 

applied is available in section V.G of 

this preamble. 

H. Executive Order 13211: Actions 

Concerning Regulations that 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not subject to Executive 

Order 13211, because it is not a 

significant regulatory action under 

Executive Order 12866. 

I. National Technology Transfer and 

Advancement Act (NTTAA) and 1 CFR 

Part 51 

This proposed action involves 

technical standards. Therefore, the EPA 

conducted searches for the PEPO 

NESHAP through the Enhanced 

National Standards Systems Network 

Database managed by the American 

National Standards Institute (ANSI). We 

also conducted a review of voluntary 

consensus standards (VCS) 

organizations and accessed and 

searched their databases. We conducted 

searches for EPA Methods 1, 1A, 2, 2A, 

2C, 2D, 2F, 2G, 3B, 4, 18, 21, 22, and 

25A of 40 CFR part 60, appendix A, and 

EPA Methods 301 and 320 of 40 CFR 

part 63, appendix A. During the EPA’s 

VCS search, if the title or abstract (if 

provided) of the VCS described 

technical sampling and analytical 

procedures that are similar to the EPA’s 

reference method, the EPA ordered a 

copy of the standard and reviewed it as 

a potential equivalent method. We 

reviewed all potential standards to 

determine the practicality of the VCS for 

this rulemaking. This review requires 

significant method validation data that 

meet the requirements of EPA Method 

301 for accepting alternative methods or 

scientific, engineering, and policy 

equivalence to procedures in the EPA 

reference methods. The EPA may 

reconsider determinations of 

impracticality when additional 

information is available for particular 

VCS. 

We did not identify any applicable 

VCS for EPA Methods 1A, 2A, 2D, 2F, 

2G, 21, and 22. However, the EPA is 

proposing amendments to 40 CFR 63.14 

to incorporate by reference the 

following three VCS: ANSI/ASME PTC 

19.10–1981—Part 10, ‘‘Flue and Exhaust 

Gas Analyses’’ as an acceptable 

alternative to EPA Method 3B (manual 

portion only); ASTM D6420–18, 

‘‘Standard Test Method for 

Determination of Gaseous Organic 

Compounds by Direct Interface Gas 

Chromatography-Mass Spectrometry’’ as 

an acceptable alternative to EPA Method 

18; and ASTM D6348–12e1, 

‘‘Determination of Gaseous Compounds 

by Extractive Direct Interface Fourier 

Transform (FTIR) Spectroscopy’’ as an 

acceptable alternative to EPA Method 

320. 

ANSI/ASME PTC 19.10–1981—Part 

10, ‘‘Flue and Exhaust Gas Analyses’’ 

quantitatively determines the gaseous 

constituents of exhausts including 

oxygen, CO2, CO, nitrogen, SO2, sulfur 

trioxide, nitric oxide, nitrogen dioxide, 

hydrogen sulfide, and hydrocarbons. 

This method incorporates both manual 

and instrumental methodologies for the 

determination of oxygen content. The 

manual method segment of the oxygen 

determination is performed through the 

absorption of oxygen. This method is 

available at the ANSI, 1899 L Street NW, 

11th Floor, Washington, DC 20036 and 

the American Society of Mechanical 

Engineers (ASME), Three Park Avenue, 

New York, NY 10016–5990; telephone 

number: 1–800–843–5990; and email 

address: customercare@asme.org. See 

https://wwww.ansi.org and https:// 

www.asme.org. The standard is 

available to everyone at a cost 

determined by ANSI/ASME ($88). 

ANSI/ASME also offer memberships or 

subscriptions for reduced costs. The 

cost of obtaining these methods is not a 

significant financial burden, making the 

methods reasonably available. 

ASTM D6420–18, ‘‘Standard Test 

Method for Determination of Gaseous 

Organic Compounds by Direct Interface 

Gas Chromatography-Mass 

Spectrometry’’ uses a direct interface 

gas chromatograph/mass spectrometer 

to measure 36 VOC and provide an onsite analysis of extracted, 

unconditioned, and unsaturated (at the 

instrument) gas samples from stationary 

sources. In this action, the EPA is 

proposing ASTM D6420–18 as an 

alternative to EPA Method 18 with the 

following caveats: 

• The target compounds are known 

and are listed in ASTM D6420–18 as 

measurable. 

• ASTM D6420–18 is not used for 

methane and ethane because the atomic 

mass is less than 35. 

• ASTM D6420–18 is never specified 

as a total VOC method. 

ASTM D6348–12e1, ‘‘Standard Test 

Method for Determination of Gaseous 

Compounds by Extractive Direct 

Interface Fourier Transform (FTIR) 

Spectroscopy’’ is an extractive FTIR 

spectroscopy-based field test method 

and is used to quantify gas phase 

concentrations of multiple target 

compounds in emissions streams from 

stationary sources. When using ASTM 

D6348–12e1, the EPA proposes the 

following conditions: (1) The test plan 

preparation and implementation in the 

Annexes to ASTM D6348–03 sections 

Al through A8 are mandatory; and (2) in 

Annex A5 (Analyte Spiking Technique) 

to ASTM D6348–103, the owner or 

operator must determine the percent 

(%) R for each target analyte (Equation 

A5.5). For the test data to be acceptable 

for a compound, %R must be 70% ≥ R 

≤ 130%. If the %R value does not meet 

this criterion for a target compound, the 

test data is not acceptable for that 

compound and the owner or operator 

must repeat the test for that analyte (i.e., 


jspears on DSK121TN23PROD with PROPOSALS
Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Proposed Rules 106061 

the sampling and/or analytical 

procedure should be adjusted before a 

retest). We are proposing that owners or 

operators must report the %R value for 

each compound in the test report, and 

all field measurements must be 

corrected with the calculated %R value 

for that compound by using the 

following equation: 

Reported Results = Measured 

Concentration in Stack/%R × 100. 

ASTM D6420–18 and ASTM D6348– 

12e1 are available at ASTM 

International, 1850 M Street NW, Suite 

1030, Washington, DC 20036. See 

https://www.astm.org/. These standards 

are available to everyone at a cost 

determined by the ASTM ($63 and $83, 

respectively). The ASTM also offers 

memberships or subscriptions that 

allow unlimited access to their methods. 

The cost of obtaining these methods is 

not a significant financial burden, 

making the methods reasonably 

available to stakeholders. 

The search identified 11 VCS that 

were potentially applicable for this 

rulemaking in lieu of EPA reference 

methods. After reviewing the available 

standards, the EPA determined that the 

11 candidate VCS (ASTM D3154–00 

(2006), ASTM D3464–96 (2007), ASTM 

3796–90 (2004), ISO 10780:1994, ASME 

B133.9–1994 (2001), ANSI/ASME PTC 

19–10–198-Part 10, NIOSH Method 

2010 ‘‘Amines, Aliphatic,’’ ASTM 

D6060–96 (2009), ISO 14965:2000(E), 

EN 12619 (1999), ASTM D4855–97 

(2002)) identified for measuring 

emissions of pollutants or their 

surrogates subject to emission standards 

in the rule would not be practical due 

to lack of equivalency, documentation, 

and validation data, and due to other 

important technical and policy 

considerations. The EPA documented 

the search and review results in the 

memorandum, Voluntary Consensus 

Standard Results for National Emission 

Standards for Hazardous Air Pollutants: 

Polyether Polyols Production Industry 

Residual Risk and Technology Review, 

which is available in the docket for this 

action. The EPA welcomes comments 

on this aspect of the proposed 

rulemaking and, specifically, invites the 

public to identify potentially applicable 

VCS and to explain why such standards 

should be used in this regulation. 

Under 40 CFR 63.7(f) and 63.8(f), 

subpart A—General Provisions, a source 

may apply to the EPA for permission to 

use alternative test methods or 

alternative monitoring requirements in 

place of any required testing methods, 

performance specifications, or 

procedures in the final rule or any 

amendments. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations and Executive 

Order 14096: Revitalizing Our Nation’s 

Commitment to Environmental Justice 

for All 

The EPA believes that the human 

health or environmental conditions that 

exist prior to this action result in or 

have the potential to result in 

disproportionate and adverse human 

health or environmental effects on 

communities with EJ concerns. For the 

PEPO NESHAP, a total of approximately 

1.5 million people live within 10 km of 

the 25 PEPO facilities that were assessed 

for risk. Based on the whole-facility 

proximity analysis summarized in 

section V.F of this preamble, the 

percentages of the population that are 

Black (13 percent versus 12 percent) and 

Hispanic or Latino (22 percent versus 19 

percent) are higher than the national 

averages. In addition, the percentages of 

the population that are below the 

poverty level (14 percent versus 12 

percent), below two times the poverty 

level (32 percent versus 30 percent), and 

over 25 years of age without a high 

school diploma (14 percent versus 12 

percent) are higher than the national 

averages. The proportions of other 

demographic groups living within 10 

km of PEPO facilities are lower than the 

national average. The EPA also 

conducted a risk assessment of possible 

cancer risks and other adverse health 

effects and found that prior to this 

proposed regulation, cancer risks for the 

PEPO Production source category were 

above acceptable levels for a number of 

areas in which these demographic 

groups live. See section V.F of this 

preamble for an analysis that 

characterizes populations living in 

proximity to facilities and risks prior to 

the proposed regulation. 

The EPA believes that this proposed 

action is likely to reduce existing 

disproportionate and adverse effects on 

communities with EJ concerns. This 

action would establish standards for EtO 

emission sources at PEPO processes 

(i.e., process vents, storage vessels, heat 

exchange systems, equipment leaks, and 

wastewater). This action proposes to 

require fenceline monitoring for EtO, 

which drives cancer risks for PEPO 

production sources, and proposes to 

address flare combustion efficiency. The 

EPA is also proposing that fenceline 

monitoring data be reported 

electronically to the EPA so that it can 

be made public and provide fenceline 

communities with greater access to 

information about potential emissions 

impacts. 

As a result of these proposed changes, 

we expect zero people to be exposed to 

risk levels above 100-in-1 million due to 

emissions from the source category. See 

sections IV.A and IV.B of this preamble 

for more information about the control 

requirements of the regulation and the 

resulting reduction in cancer risks. Also, 

see section V.F of this preamble for an 

analysis that characterizes populations 

living in proximity to facilities after 

implementation of the proposed 

regulation (post-control). 

The information supporting this 

Executive order review is contained in 

section V.F of this preamble, as well as 

in the technical reports, Analysis of 

Demographic Factors for Populations 

Living Near Polyether Polyols (PEPO) 

Production Facilities—Source Category 

Analysis of Proposed Amendments, 

Analysis of Demographic Factors for 

Populations Living Near Polyether 

Polyols (PEPO) Production Facilities— 

Whole Facility Analysis of Proposed 

Amendments, and Analysis of 

Demographic Factors for Populations 

Living Near Polyether Polyols (PEPO) 

Production Facilities—CommunityBased Assessment, which are available 

in the docket for this action. 

List of Subjects in 40 CFR Part 63 

Environmental protection, 

Administrative practice and procedures, 

Air pollution control, Hazardous 

substances, Incorporation by reference, 

Intergovernmental relations, Reporting 

and recordkeeping requirements. 

Michael S. Regan, 

Administrator. 

[FR Doc. 2024–29466 Filed 12–26–24; 8:45 am] 

BILLING CODE 6560–50–P 


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