88940 Federal Register / Vol. 89, No. 218 / Tuesday, November 12, 2024 / Proposed Rules 

APPENDIX C TO PART 4—ALPHABETICAL INDEX OF DISABILITIES—Continued 

Diagnostic code No. 

Seventh (facial) ......................................................................................................................................................... 8207 

Tenth (pneumogastric, vagus) .................................................................................................................................. 8210 

Twelfth (hypoglossal) ................................................................................................................................................ 8212 

Peripheral nerves: 

All radicular groups ................................................................................................................................................... 8513 

Axillary (circumflex) ................................................................................................................................................... 8518 

Common peroneal (external popliteal) ...................................................................................................................... 8521 

Deep peroneal (anterior tibial) .................................................................................................................................. 8523 

Femoral (anterior crural) ........................................................................................................................................... 8526 

Ilio-inguinal ................................................................................................................................................................ 8530 

Lateral cutaneous nerve of the thigh (external cutaneous) ...................................................................................... 8529 

Long thoracic ............................................................................................................................................................. 8519 

Lower radicular group ............................................................................................................................................... 8512 

Median ....................................................................................................................................................................... 8515 

Middle radicular group ............................................................................................................................................... 8511 

Musculocutaneous ..................................................................................................................................................... 8517 

Obturator ................................................................................................................................................................... 8528 

Posterior tibial ............................................................................................................................................................ 8525 

Radial (musculospiral) ............................................................................................................................................... 8514 

Saphenous (internal saphenous) .............................................................................................................................. 8527 

Sciatic ........................................................................................................................................................................ 8520 

Superficial peroneal (musculocutaneous) ................................................................................................................. 8522 

Tibial (internal popliteal) ............................................................................................................................................ 8524 

Ulnar .......................................................................................................................................................................... 8516 

Upper radicular group ............................................................................................................................................... 8510 

*******

Multiple sclerosis and other demyelinating diseases of the central nervous system ............................................................. 8018 

*******

Optic neuropathy ..................................................................................................................................................................... 6026 

*******

Paramyoclonus multiplex (convulsive state, myoclonic type) ................................................................................................. 8104 

*******

Parkinson’s disease (paralysis agitans) .................................................................................................................................. 8004 

Parkinson’s plus, or secondary parkinsonism syndromes ...................................................................................................... 8026 

*******

Primary lateral sclerosis .......................................................................................................................................................... 8036 

*******

Stroke (ischemic, hemorrhagic, or thrombotic), including cerebral infarction or cerebrovascular accident ........................... 8007 

*******

[FR Doc. 2024–25665 Filed 11–8–24; 8:45 am] 

BILLING CODE 8320–01–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 51 

[EPA–HQ–OAR–2023–0295; FRL–10823–01– 

OAR] 

RIN 2060–AW00 

Air Quality: Revision to the Regulatory 

Definition of Volatile Organic 

Compounds—Exclusion of (Z)-1- 

chloro-2,3,3,3-tetrafluoropropene 

(HCFO-1224yd(Z)) 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The U.S. Environmental 

Protection Agency (EPA) is proposing to 

revise the EPA’s regulatory definition of 

volatile organic compounds (VOC) 

under the Clean Air Act (CAA). This 

action proposes to add (Z)-1-chloro2,3,3,3-tetrafluoropropene (also known 

as HCFO-1224yd(Z); CAS number 

111512–60–8) to the list of compounds 

excluded from the regulatory definition 

on the basis that this compound makes 

a negligible contribution to tropospheric 

ozone (O3) formation. 

DATES: Comments must be received on 

or before January 13, 2025. 

ADDRESSES: You may send comments, 

identified by Docket ID No. EPA–HQ– 

OAR–2023–0295, by any of the 

following methods: 

• Federal eRulemaking Portal: 

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Mail: U.S. Environmental 

Protection Agency, EPA Docket Center, 

Docket No. EPA–HQ–OAR–2023–0295, 

Office of Air and Radiation Docket, Mail 

Code 28221T, 1200 Pennsylvania 

Avenue NW, Washington, DC 20460. 

• Hand Delivery or Courier: EPA 

Docket Center, WJC West Building, 

Room 3334, 1301 Constitution Avenue 

NW, Washington, DC 20004. The Docket 

Center’s hours of operations 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 


khammond on DSKJM1Z7X2PROD with PROPOSALS
Federal Register / Vol. 89, No. 218 / Tuesday, November 12, 2024 / Proposed Rules 88941 

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 

‘‘Public Participation’’ heading of the 

SUPPLEMENTARY INFORMATION section of 

this document. 

FOR FURTHER INFORMATION CONTACT: Dr. 

Souad Benromdhane, Office of Air 

Quality Planning and Standards, Health 

and Environmental Impacts Division, 

Mail Code C539–07, Environmental 

Protection Agency, P.O. Box 12055, 

Research Triangle Park, NC 27711; 

telephone: (919) 541–4359; email 

address: benromdhane.souad@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Public Participation 

Written comments: Submit your 

comments, identified by Docket ID No. 

EPA–HQ–OAR–2023–0295, at https://

www.regulations.gov (our preferred 

method), or the other methods 

identified in the ADDRESSES section. 

Once submitted, comments cannot be 

edited or removed from the docket. The 

EPA may publish any comment received 

to its public docket. Do not submit to 

EPA’s docket at https://

www.regulations.gov any information 

you consider to be Confidential 

Business Information (CBI), Proprietary 

Business Information (PBI), or other 

information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). Please visit 

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

commenting-epa-dockets for additional 

submission methods; the full EPA 

public comment policy; information 

about CBI, PBI, or multimedia 

submissions; and general guidance on 

making effective comments. 

Table of Contents 

I. Does this action apply to me? 

II. Background 

A. The EPA’s VOC Exemption Policy 

B. Petition To List HCFO-1224yd(Z) as an 

Exempt Compound 

III. The EPA’s Assessment of the Petition 

A. Contribution to Tropospheric Ozone 

Formation 

B. Potential Impacts on Other 

Environmental Endpoints 

1. Contribution to Stratospheric Ozone 

Depletion 

2. Toxicity 

3. Contribution to Climate Change 

C. Conclusions 

IV. Proposed Action 

V. 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 

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) 

J. Executie 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 

VI. References 

I. Does this action apply to me? 

Entities potentially affected by this 

proposed rule include, but are not 

necessarily limited to, the following: 

State and local air pollution control 

agencies that adopt and implement 

regulations to control air emissions of 

VOC; and industries manufacturing 

and/or using HCFO-1224yd(Z) for use in 

foam blowing, refrigeration, as well as 

applications in solvents and aerosol 

propellants, and other minor uses. 

Potential entities that may be affected by 

this action include the following: 

TABLE 1—POTENTIALLY AFFECTED ENTITIES BY NORTH AMERICAN INDUSTRIAL CLASSIFICATION SYSTEM (NAICS) CODE

Category NAICS code Description of regulated entities 

Industry .............. 333415 Air-Conditioning and Warm Air Heating Equipment and Commercial and Industrial Refrigeration Equipment 

Manufacturing. 

Industry .............. 811310 Commercial and industrial machinery and equipment (except automotive and electronic) repair and maintenance. 

Industry .............. 221116 Geothermal Electric Power Generation. 

Industry .............. 221117 Biomass Electric Power Generation. 

Industry .............. 221118 Other Electric Power Generation. 

This table is not intended to be 

exhaustive but rather provides a guide 

for readers regarding entities that might 

be affected by this deregulatory action. 

This table lists the types of entities that 

the EPA is now aware of that could 

potentially be affected to some extent by 

this action. Other types of entities not 

listed in the table could also be affected 

to some extent. To determine whether 

your entity is directly or indirectly 

affected by this action, you should 

consult your State or local air pollution 

control and/or air quality management 

agencies. 

II. Background 

A. The EPA’s VOC Exemption Policy 

Tropospheric O3, commonly known 

as smog, is formed when VOC and 

nitrogen oxides (NOX) react in the 

atmosphere in the presence of sunlight. 

Because of the harmful health effects of 

O3, the EPA and State governments limit 

the amount of VOC that can be released 

into the atmosphere. VOC form O3

through atmospheric photochemical 

reactions, and different VOC have 

different levels of reactivity. That is, 

different VOC do not react to form O3

at the same speed or form different 

amounts of O3. Some VOC react more 

slowly or form less O3; therefore, 

changes in their emissions have limited 

effects on local or regional O3 pollution 

episodes. It has been the EPA’s policy 

since 1971 that certain organic 

compounds with a negligible level of 

reactivity should be excluded from the 

regulatory definition of VOC to focus 

VOC control efforts on compounds that 

significantly affect O3 concentrations. 

The EPA also believes that exempting 

such compounds creates an incentive 

for industry to use negligibly reactive 

compounds in place of more highly 

reactive compounds that are regulated 

as VOC. The EPA lists compounds that 


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88942 Federal Register / Vol. 89, No. 218 / Tuesday, November 12, 2024 / Proposed Rules 

1 Interim Guidance on Control of Volatile Organic 

Compounds in Ozone State Implementation Plans, 

2005, US Environmental Protection Agency, 

Document Number 05–18015 (70 FR 54046). And 

could be found at this link: https://

www.govinfo.gov/content/pkg/FR-2005-09-13/pdf/ 

05-18015.pdf. 

it has determined to be negligibly 

reactive in its regulations as being 

excluded from the regulatory definition 

of VOC (40 CFR 51.100(s)). 

The CAA requires the regulation of 

VOC for various purposes. Section 

302(s) of the CAA specifies that the EPA 

has the authority to define the meaning 

of ‘‘VOC’’ and, hence, what compounds 

shall be treated as VOC for regulatory 

purposes. The policy of excluding 

negligibly reactive compounds from the 

regulatory definition of VOC was first 

laid out in the ‘‘Recommended Policy 

on Control of Volatile Organic 

Compounds’’ (42 FR 35314, July 8, 

1977) (‘‘1977 Recommended Policy’’) 

and was supplemented subsequently 

with the ‘‘Interim Guidance on Control 

of Volatile Organic Compounds in 

Ozone State Implementation Plans’’ (70 

FR 54046, September 13, 2005) (‘‘2005 

Interim Guidance’’). The EPA uses the 

reactivity of ethane as the threshold for 

determining whether a compound has 

negligible reactivity. Compounds that 

are less reactive than, or equally reactive 

to, ethane under certain assumed 

conditions may be deemed negligibly 

reactive and, therefore, suitable for 

exemption from the regulatory 

definition of VOC. Compounds that are 

more reactive than ethane continue to 

be considered VOC for regulatory 

purposes and, therefore, are subject to 

control requirements. The selection of 

ethane as the threshold compound was 

based on a series of smog chamber 

experiments that underlay the 1977 

Recommended Policy. 

The EPA has used three different 

metrics to compare the reactivity of a 

specific compound to that of ethane: (i) 

the rate constant for reaction with the 

hydroxyl radical (OH) (known as kOH); 

(ii) the maximum incremental reactivity 

(MIR) on a reactivity per unit mass 

basis; and (iii) the MIR expressed on a 

reactivity per mole basis. Differences 

between these three metrics are 

discussed below. 

The kOH is the rate constant of the 

reaction of the compound with the OH 

radical in the air. This reaction is often, 

but not always, the first and ratelimiting step in a series of chemical 

reactions by which a compound breaks 

down in the air and contributes to O3

formation. If this step is slow, the 

compound will likely not form O3 at a 

very fast rate. The kOH values have long 

been used by the EPA as metrics of 

photochemical reactivity and O3- 

forming activity, and they were the basis 

for most of the EPA’s early exemptions 

of negligibly reactive compounds from 

the regulatory definition of VOC. The 

kOH metric is inherently a molar-based 

comparison, i.e., it measures the rate at 

which molecules react. 

The MIR, both by mole and by mass, 

is a more updated metric of 

photochemical reactivity derived from a 

computer-based photochemical model, 

and it has been used as a metric of 

reactivity since 1995. This metric 

considers the complete O3-forming 

activity of a compound over multiple 

hours and through multiple reaction 

pathways, not merely the first reaction 

step with OH. Further explanation of 

the MIR metric can be found in Carter 

(1994). 

The EPA has considered the choice 

between MIRs with a molar or mass 

basis for the comparison to ethane in 

past rulemakings and guidance. In the 

2005 Interim Guidance, the EPA stated 

that a comparison to ethane’s MIR on 

the mass basis strikes the right balance 

between a threshold that is low enough 

to capture chemicals that significantly 

affect ozone formation and a threshold 

that is high enough to allow for the 

exemption of some other chemicals that 

may usefully substitute for more 

reactive compounds. The guidance also 

stated that EPA will continue to 

compare chemicals to ethane using kOH

expressed on a molar basis and MIR 

values expressed on a mass basis during 

the review of suggested chemicals for 

VOC-exempt status.1 The 2005 Interim 

Guidance notes that the EPA will 

consider a compound to be negligibly 

reactive if it is equally reactive as or less 

reactive than ethane based on either kOH

expressed on a molar basis or MIR 

values expressed on a mass basis (70 FR 

54046). 

The molar comparison of MIR is more 

consistent with the original smog 

chamber experiments, which compared 

equal molar concentrations of 

individual VOC, supporting the 

selection of ethane as the threshold, 

while the mass-based comparison of 

MIR is consistent with how MIR values 

and other reactivity metrics are applied 

in reactivity-based emission limits. It is, 

however, important to note that the 

mass-based comparison is less 

restrictive than the molar-based 

comparison in that more compounds 

would qualify as negligibly reactive. 

Given the two goals of the exemption 

policy articulated in the 2005 Interim 

Guidance, the EPA believes that ethane 

continues to be an appropriate threshold 

for defining negligible reactivity. And, 

to encourage the use of environmentally 

beneficial substitutions, the EPA 

continues to believe that a comparison 

to ethane on a mass basis strikes the 

right balance between a threshold that is 

low enough to capture compounds that 

significantly affect O3 concentrations 

and a threshold that is high enough to 

exempt some compounds that may 

usefully substitute for more highly 

reactive compounds. 

The 2005 Interim Guidance also noted 

that concerns have sometimes been 

raised about the potential impact of a 

VOC exemption on environmental 

endpoints other than O3 concentrations, 

including fine particle formation, air 

toxics exposures, stratospheric O3

depletion, and climate change. The EPA 

has recognized, however, that there are 

existing regulatory or non-regulatory 

programs that are specifically designed 

to address these issues, and the EPA 

continues to believe in general that the 

impacts of VOC exemptions on 

environmental endpoints other than O3

formation can be adequately addressed 

by these programs. The VOC exemption 

policy is intended to facilitate 

attainment of the O3 National Ambient 

Air Quality Standards (NAAQS), and 

VOC exemption decisions will continue 

to be based primarily on consideration 

of a compound’s contribution to O3

formation. However, if the EPA 

determines that a particular VOC 

exemption is likely to result in a 

significant increase in the use of a 

compound and that the increased use 

would pose a significant risk to human 

health or the environment that would 

not be addressed adequately by existing 

programs or policies, then the EPA may 

exercise its judgment accordingly in 

deciding whether to grant an exemption. 

The EPA has provided the foregoing 

discussion of its VOC exemption 

policies as background for its 

assessment of the petition to list HCFO1224yd(z) as an exempt compound and 

its proposed action to grant the petition. 

However, the EPA is not reopening the 

2005 Interim Guidance or other aspects 

of its VOC exemption policy in this 

proposed rule and is not seeking 

comment on these issues. 

B. Petition To List HCFO-1224yd(Z) as 

an Exempt Compound 

The AGC Chemicals Americas, Inc. 

(‘‘AGC’’) submitted a petition to the EPA 

on July 29, 2020, requesting that (Z)-1- 

chloro-2,3,3,3-tetrafluoropropene (also 

known as HCFO-1224yd(Z); CAS 

number 111512–60–8) be exempted 

from the regulatory definition of VOC. 

The petition stated that HCFO1224yd(Z) has low reactivity (i.e., 0.052 

± 0.011g of O3/g of HCFO-1224yd(Z)) 


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Federal Register / Vol. 89, No. 218 / Tuesday, November 12, 2024 / Proposed Rules 88943 

2 84 FR 64765 (Nov. 25, 2019): https://

www.federalregister.gov/documents/2019/11/25/ 

2019-25412/protection-of-stratospheric-ozonedetermination-35-for-significant-new-alternativespolicy-program. 

3Carter, W. P. L. 2020. Estimation of the groundlevel atmospheric ozone formation potential of 

isomers of 1-chloro-2,3,3,3-tetrafluoro-1-propene, 

HFCO-1224YD(Z), Report to AGC Chemicals 

Americas Company, Exton, PA, USA. 4Supporting memo is included in the docket. 

compared to the MIR of ethane (0.28 g 

O3/g). The petitioner indicated that 

HCFO-1224yd(Z) may be used in 

refrigeration which uses a turbo-type 

refrigerator, a binary generator, a heat 

recovery heat pump, etc. As a 

refrigerant, this compound will not be 

generally emitted into the atmosphere 

on a continuous basis in significant 

amounts. Refrigerators will be initially 

charged and then serviced with HCFO1224yd(Z) with minimal losses of 

refrigerant to the atmosphere over time, 

and they will be subject to EPA’s 

regulations related to servicing and 

‘‘venting.’’ HCFO-1224yd(Z) has been 

approved by EPA through its Significant 

New Alternatives Policy (SNAP) 

program as an acceptable substitute for 

use in new and retrofitted centrifugal 

chillers, positive displacement chillers 

and industrial process refrigeration.2

AGC has developed HCFO-1224yd(Z) 

to support reductions in emissions of 

greenhouse gases (GHGs). The global 

warming potential (GWP) for HCFO1224yd(Z) is 0.88 for a time horizon of 

100 years. HCFO-1224yd(Z) is relatively 

short-lived in the atmosphere, with a 

lifetime of approximately 20 days. 

HCFO-1224yd(Z)’s ODP is almost zero 

(0.00023) and, leading to an 

environmental impact that is estimated 

to be low especially when compared to 

the existing alternatives (Tokuhashi et 

al., 2018). Hence, HCFO-1224yd(Z) can 

serve as a replacement for compounds 

in several centrifugal and positive 

displacement chillers such as ammonia 

absorption, carbon dioxide, and HFO1336mzz(Z) among others with GWP 

ranging between zero and 630. For 

industrial process refrigeration, HCFO1224yd(Z) has a GWP lower than or 

comparable to that of acceptable 

existing substitutes for new or retrofit 

equipment with GWP ranging between 

zero and 14,800. 

Toxicity of HCFO-1224yd(Z) is 

comparable to or lower than that of 

other available substitutes in the same 

end uses. The toxicity risks are 

evaluated through the SNAP program 

but can also be minimized through the 

application of recommended guidance 

in the Occupational Alliance for Risk 

Science’s Workplace Environmental 

Exposure Level (OARS WEEL), the 

American Society of Heating, 

Refrigerating and Air-Conditioning 

Engineers safety standards 15 (ASHARE 

15) and other industry standards, as 

well as the safety data sheet (SDS) and 

other safety precautions related to 

refrigeration and air conditioning 

industry. 

To support its petition, AGC provided 

a document on ground-level 

atmospheric ozone formation potential 

from the reactivity of HCFO-1224yd(Z) 

with the hydroxyl OH based on 

calculations using SARPC-11 

atmospheric chemical mechanism.3

AGC’s supplemental technical report 

supplied a MIR of HCFO-1224yd(Z) of 

0.052 ± 0.011 g O3/g HCFO-1224yd(Z) 

on the mass-based MIR scale. This 

reactivity is significantly lower than that 

of ethane (0.29 ± 0.07 g O3/g ethane). 

The report also addressed uncertainties 

around the MIR value calculated and 

stipulated that the relative impact on 

ozone formation will be small when 

compared to variability in atmospheric 

conditions. The report raised a warning 

around the chemical mechanism used to 

predict ozone formation potential to 

caution about the need to test whether 

the predicted value can be observed in 

an environmental chamber experiment. 

The petition did not include a value for 

the rate constant kOH for the gas-phase 

reaction with OH radicals. 

To address the potential for 

stratospheric O3 impacts, the petitioner 

specified that, because the atmospheric 

lifetime of HCFO-1224yd(Z) due to loss 

by OH reaction was estimated to be 

relatively short, even though HCFO1224yd(Z) contains chlorine, it is not 

expected to contribute to the depletion 

of the stratospheric O3 layer more than 

other alternatives listed acceptable by 

EPA’s SNAP program (USEPA, 2019). 

III. The EPA’s Assessment of the 

Petition 

The EPA is proposing to respond to 

the petition to revise the EPA’s 

regulatory definition of VOC for 

exemption of HCFO-1224yd(Z). This 

action is based on consideration of the 

compound’s low contribution to 

tropospheric O3 and the low likelihood 

of risk to human health or the 

environment, including stratospheric O3

depletion, toxicity, and climate change. 

Additional information on these topics 

is provided in the following sections. 

A. Contribution to Tropospheric Ozone 

Formation 

The rate constant kOH for the gasphase reaction with OH radicals is 

measured to be (5.84 ± 0.030) 10¥13

cm3/molecule-sec at ∼298 degrees 

Kelvin (K) (Tokuhashi et al., 2018). This 

kOH is more than twice the kOH of ethane 

(2.4 × 10¥13 cm3/molecule-sec at ∼298 

K; Atkinson et al., 2006) even when 

uncertainty is considered and, therefore, 

suggests that it is more reactive than 

ethane. In most cases, chemicals with 

high kOH values also have high MIR 

values, but the products that are formed 

here in subsequent reactions are 

expected to be polyfluorinated 

compounds, which do not contribute to 

O3 formation (Osterstrom et al., 2017). 

In the case of HCFO-1224yd(Z), while 

the kOH is relatively high, the calculated 

maximum incremental reactivity MIR is 

very low when compared to that of 

ethane based on Carter (2020), provided 

by the petitioner, and reviewed by EPA. 

Carter (2020) estimates that HCFO1224yd(Z) has a MIR value of 0.052 ± 

0.011 g O3/g VOC versus 0.29 ± 0.07 g 

O3/g VOC for ethane. Therefore, the EPA 

considers HCFO-1224yd(Z) to be 

negligibly reactive and eligible for VOCexempt status following the Agency’s 

long-standing policy that compounds 

should so qualify where either reactivity 

metric (kOH expressed on a molar basis 

or MIR expressed on a mass basis) 

indicates that the compound is less 

reactive than ethane. While the overall 

atmospheric reactivity of HCFO1224yd(Z) was not studied in an 

experimental smog chamber, the 

chemical mechanism derived from other 

chamber studies (Carter, 2011) was used 

to model the complete formation of O3

for an entire single day under realistic 

atmospheric conditions by Carter 

(2020). The EPA has assessed the Carter 

study provided by the petitioner and 

believes the calculated MIR value is 

reliable.4

Table 2 presents three reactivity 

metrics for HCFO-1224yd(Z) as they 

compare to ethane. 


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5Occupational Alliance for Risk Science (OARS– 

WEELs)– HCFO-1224yd(Z)), 2017: https://

www.tera.org/OARS/PDF_documents/09_hcfo1224yd(z)-weel-document-final-2017.pdf. 

6 (‘‘(Z)-I-Chloro-2,3,3,3-tetrafluoropropene 

(HCFO-1224yd(Z)) (2017). (2019). Toxicology and 

Industrial Health, 36(5), 305–309. https://doi.org/ 

10.1177/0748233720930548. 

TABLE 2—REACTIVITIES OF ETHANE AND HCFO-1224yd(Z) 

Compound kOH

(cm3/molecule-sec) 

Maximum 

incremental 

reactivity (MIR) 

(g O3/mole VOC) 

Maximum 

incremental 

reactivity (MIR) 

(g O3/g VOC) 

Ethane .................................................................. 2.4 × 10¥13 .......................................................... 8.4 0.28 ± 0.07 

HCFO-1224yd(Z) .................................................. (5.84 ± 0.030) × 10¥13 ......................................... 7.7 0.052 ± 0.011 

Notes: 

kOH value at 298 K for ethane is from Atkinson et al. (2006; page 3626). 

kOH value at 300 K for HCFO-1224yd(Z) is from Tokuhashi et al., 2018 (table 1). 

Mass-based MIR value (g O3/g VOC) of ethane is from Carter (2011). 

Mass-based MIR value (g O3/g VOC) of HCFO-1224yd(Z) is from Carter 2020. 

Molar-based MIR (g O3/mole VOC) values were calculated from the mass-based MIR (g O3/g VOC) values using the number of moles per 

gram of the relevant organic compound. 

The reaction rate of HCFO-1224yd(Z) 

with the OH radical (kOH) has been 

measured to be (5.84 ± 0.030) × 10¥13

cm3/molecule-sec (Tokuhashi et al., 

2018); other reactions with O3 and the 

nitrate radical were negligibly small. 

The corresponding reaction rate of 

ethane with OH is 2.4 × 10¥13 cm3/ 

molecule-sec (Atkinson et al., 2006). 

The data in table 2 show that HCFO1224yd(Z) has a higher kOH value than 

ethane, meaning that it initially reacts 

more than twice as fast in the 

atmosphere as ethane. However, the 

resulting unsaturated fluorinated 

compounds in the atmosphere are short 

lived and react more slowly to form O3

(Baasandorj et al., 2011). The modeled 

reactivity based on the mechanism 

considered by Carter resulted in a very 

low maximum incremental reactivity on 

a mass basis. When compared to ethane, 

HCFO-1224yd(Z) has a MIR of 0.052 ± 

0.011 g O3/g VOC. Hence HCFO1224yd(Z)’s MIR is less than the fifth of 

that of ethane at 0.28 ± 0.07 g O3/g 

ethane. As shown in table 2, HCFO1224yd(Z)’s MIR on a molar basis is also 

somewhat lower than that of ethane. 

Considering the uncertainty and 

variability in the MIR modeling, as 

described by Carter (2020), we are 

confident that the MIR of HCFO1224yd(Z) is less than that of ethane. 

A molecule of HCFO-1224yd(Z) is 

considerably less reactive than a 

molecule of ethane in terms of complete 

O3-forming activity, as shown by the 

molar-based MIR (g O3/mole VOC) 

values. Likewise, one gram of HCFO1224yd(Z) has a lower capacity than one 

gram of ethane to form O3 in terms of 

a mass-based MIR. Thus, following the 

2005 Interim Guidance, the EPA finds 

HCFO-1224yd(Z) to be eligible for 

exemption from the regulatory 

definition of VOC based on both the 

molar- and mass-based MIR. 

B. Potential Impacts on Other 

Environmental Endpoints 

The EPA’s decision to exempt HCFO1224yd(Z) from the regulatory definition 

of VOC is based on our findings above. 

However, as noted in the 2005 Interim 

Guidance, the EPA reserves the right to 

exercise its judgment in certain cases 

where an exemption is likely to result 

in a significant increase in the use of a 

compound and a subsequent 

significantly increased risk to human 

health or the environment. In this case, 

the EPA does not find that exemption of 

HCFO-1224yd(Z) would result in an 

increase of risk to human health or the 

environment, regarding stratospheric O3

depletion, toxicity, and climate change. 

More information on these topics is 

provided in the following sections. 

1. Contribution to Stratospheric Ozone 

Depletion 

The SNAP program is the EPA’s 

program to evaluate and regulate 

substitutes for end-uses historically 

using O3-depleting chemicals. Under 

section 612(c) of the CAA, the EPA is 

required to identify and publish lists of 

acceptable and unacceptable substitutes 

for class I or class II O3-depleting 

substances. Per the SNAP program 

findings, the ODP of HCFO-1224yd(Z) is 

zero, which is significantly less than the 

ODPs for the [ozone depleting 

substances] ODS subject to the phase 

out of production and consumption 

under regulations issued under sections 

601–607 of the CAA and consistent with 

the Montreal Protocol on Substances 

that Deplete the Ozone Layer. The 

SNAP program has listed HCFO1224yd(Z) as an acceptable substitute 

for chillers and other industrial process 

refrigeration end-uses provided in 84 FR 

64765, November 25, 2019 (USEPA, 

2019). 

HCFO-1224yd(Z) is unlikely to 

contribute to the depletion of the 

stratospheric O3 layer. The O3 depletion 

potential (ODP) of HCFO-1224yd(Z) is 

expected to be negligible based on 

several lines of evidence (Tokuhashi et 

al., 2018; Guo et al., 2019). Because 

HCFO-1224yd(Z)’s atmospheric lifetime 

is short (20 days according to Tokuhashi 

et al., 2018) compared to the timescale 

for mixing within the troposphere, it 

will decay before it has a chance to 

reach the stratosphere and, thus, will 

not participate in O3 destruction (Guo et 

al., 2019). 

2. Toxicity 

Based on screening assessments of the 

health and environmental risks of 

HCFO-1224yd(Z), the SNAP program 

expected that users will be able to use 

the compound without significantly 

greater health risks than presented using 

other available substitutes for the same 

end uses (USEPA, 2019). 

The EPA anticipates that HCFO1224yd(Z) will be used consistent with 

the recommendations specified in the 

manufacturer’s SDS (AGC, 2017). 

According to the SDS, potential health 

effects from inhalation of HCFO1224yd(Z) include drowsiness or 

dizziness, irritation of the skin or eyes, 

or frostbite. These potential health 

effects are common to many refrigerants. 

However, HCFO-1224yd(Z) could cause 

asphyxiation if air is displaced by 

vapors in a confined space. The 

Workplace Environmental Exposure 

Limit (WEEL) committee of the 

Occupational Alliance for Risk Science 

(OARS) reviewed available animal 

toxicity data and recommends a WEEL 

for the workplace of 1000 parts per 

million (ppm) (6700 mg/m3) 5 timeweighted average (TWA) for an 8-hour 

workday, as later published in 2019 in 

Toxicology and Industrial Health (‘‘(Z)- 

I-Chloro-2,3,3,3-tetrafluoropropene,’’ 

2020).6 This WEEL was derived based 


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7 Interim Guidance on Control of Volatile Organic 

Compounds in Ozone State Implementation Plans, 

2005, US Environmental Protection Agency, 

Document Number 05–18015 (70 FR 54046). And 

could be found at this link: https://

www.govinfo.gov/content/pkg/FR-2005-09-13/pdf/ 

05-18015.pdf. 

8 IPCC, 2013: Climate Change 2013: Chapter 8, 

Myhre, G., D. Shindell, F.-M. Bre ́on, W. Collins, J. 

Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. 

Lee, B. Mendoza, T. Nakajima, A. Robock, G. 

Stephens, T. Takemura and H. Zhang, 2013: 

Anthropogenic and Natural Radiative Forcing. In: 

Climate Change 2013: The Physical Science Basis. 

Contribution of Working Group I to the Fifth 

Assessment Report of the Intergovernmental Panel 

on Climate Change [Stocker, T.F., D. Qin, G.-K. 

Plattner, M. Tignor, S.K. Allen, J. Boschung, A. 

Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. 

Cambridge University Press, Cambridge, United 

Kingdom and New York, NY, USA. https://

www.ipcc.ch/site/assets/uploads/2018/02/ 

WG1AR5_Chapter08_FINAL.pdf. 

9Lifetimes, direct and indirect radiative forcing, 

and global warming potentials of ethane (C2H6), 

propane (C3H8), and butane (C4H10): https://

rmets.onlinelibrary.wiley.com/doi/full/10.1002/ 

asl.804. 

on a 4-week, GLP-compliant inhalation 

toxicity study in rats (AGC, 2016), based 

on the point of departure a NOAEL of 

40,000 ppm. This was also the NOAEL 

for the developmental toxicity study 

where developmental effects were only 

observed in female rats. The EPA 

expects that users will be able to meet 

the WEEL and address potential health 

risks by following requirements and 

recommendations in the SDS and other 

safety precautions common to the 

refrigeration and air conditioning 

industry. 

HCFO-1224yd(Z) is not regulated as a 

hazardous air pollutant (HAP) under 

title I of the CAA. Also, it is not listed 

as a toxic chemical under section 313 of 

the Emergency Planning and 

Community Right-to-Know Act 

(EPCRA). 

The Toxic Substances Control Act 

(TSCA) gives the EPA authority, among 

other things, to evaluate and, if 

necessary, address risks of injury to 

health or the environment from new 

chemical substances before such 

substances may be manufactured 

(including imported). Section 5 of TSCA 

requires manufacturers and importers to 

notify the EPA before manufacturing a 

new chemical substance or 

manufacturing or processing any 

chemical substance for a use which the 

Administrator has determined is a 

significant new use. When EPA receives 

such notice, it assesses whether 

sufficient information is available to 

permit a reasoned evaluation of the 

health and environmental effects of the 

substance or use and whether 

manufacturing, processing, distribution 

in commerce, use, or disposal of the 

substance (or any combination of such 

activities) presents, may present, or is 

not likely to present an unreasonable 

risk. Based on its review of a 

premanufacture notice (PMN) for HCFO1224yd(Z), the EPA signed a consent 

order under TSCA section 5(e) to protect 

against an unreasonable risk of injury to 

health or the environment. EPA also 

subsequently issued a Significant New 

Use Rule (SNUR) under TSCA that 

requires submission of a Significant 

New Use Notice (SNUN) to the EPA at 

least 90 days before manufacturing or 

processing of HCFO-1224yd(Z) for any 

significant new use. The required 

notification will provide the EPA with 

the opportunity to evaluate any 

intended significant new use before it 

occurs and, if necessary, to issue orders 

to address any potential unreasonable 

risk to human health or the 

environment. 

HCFO-1224yd(Z) is one of the class of 

substances generally referred to as perand polyfluoroalkyl substances (PFAS). 

Many PFAS compounds represent a 

public health concern due to their 

toxicity and persistence in the 

environment. As a class, they are also 

highly varied, and variations in 

structure may result in (yet unknown) 

differences in environmental mobility 

and toxicity. The agency’s ongoing work 

addressing PFAS does not currently 

address HCFO-1224yd(Z) specifically; 

however, the exposure limits and SNAP 

screening assessment noted above give 

us confidence that the use of this 

compound will not pose an 

unreasonable risk to human health. EPA 

also believes that the impacts of PFAS 

will be adequately addressed by 

regulatory and non-regulatory programs 

specifically designed to address those 

impacts.7

3. Contribution to Climate Change 

The Intergovernmental Panel on 

Climate Change (IPCC) Fifth Assessment 

Report (IPCC AR5) does not provide an 

estimate for HCFO-1224yd(Z)’s global 

warming potential (GWP).8 The HCFO1224yd(Z) GWP on a 100-year time 

horizon was calculated to be 5.4 in one 

study by Tokuhashi et al. (2018), but the 

same study reported an experimental 

chamber value of 0.88 and a lifetime of 

20 days. This is consistent with the 

Scientific Assessment of Ozone 

Depletion by the chemical sciences 

laboratory (NOAA, 2022) where the 

GWP was found to be smaller than one 

under all reactivity efficiencies and 

recommended adjustments. These 

authors also calculated an inflated 

radiation or IR spectrum from a 

theoretical model using density 

functional theory (DFT) for HCFO1224yd(Z). That calculation gives a 

GWP of 5.4. While the theoretical value 

differs substantially on a percentage 

basis from the measured value, the GWP 

based on the experimental measurement 

is expected to be the more accurate 

given the large uncertainties in the 

calculated molecular model which tend 

to be unknown and high. Either value is 

1–2 orders of magnitude lower than the 

GWP for the refrigerant(s) that HCFO1224yd(Z) is designed to replace. HCFO1224yd(Z) has a GWP below one 

indicating that it has less radiating 

impact than that of CO2 over a 100-year 

time period (GWP100). Species with 

double bonds assembled in the 

Intergovernmental Panel on Climate 

Change Fifth Assessment Report (table 

8.A.1) show lower GWP than species 

without a double bond. According to the 

SNAP rule, HCFO-1224yd(Z)’s GWP is 

smaller than one and is comparable to 

or lower than those of some of the 

substitutes such as used in new chillers, 

ammonia absorption, carbon dioxide 

(CO2), and hydro-fluoro-olefin (HFO– 

1336mzz(Z)), and for new and retrofit 

chillers with GWPs ranging from 0 to 

630. (USEPA, 2019). Both the calculated 

and the observed values of HCFO1224yd(Z)’s GWP are lower than that of 

ethane determined to be 10.2.9

C. Conclusions 

The EPA finds that HCFO-1224yd(Z) 

is negligibly reactive with respect to its 

contribution to tropospheric O3

formation and, thus, may be exempted 

from the EPA’s definition of VOC in 40 

CFR 51.100(s). HCFO-1224yd(Z) has 

been listed as acceptable for use in new 

and retrofitted centrifugal chillers, 

positive displacement chillers and 

industrial process refrigeration under 

the SNAP program (USEPA, 2019). The 

EPA has also determined that 

exemption of HCFO-1224yd(Z) from the 

regulatory definition of VOC will not 

result in an increase of risk to human 

health and the environment, and, to the 

extent that use of this compound does 

have impacts on other environmental 

endpoints, those impacts are adequately 

managed by existing programs. For 

example, HCFO-1224yd(Z) has a similar 

or lower stratospheric O3 depletion 

potential than available substitutes in 

those end-uses, and the toxicity risk 

from using HCFO-1224yd(Z) is not 

significantly greater than the risk from 

using other available alternatives for the 

same uses. The EPA has concluded that 

non-tropospheric O3-related risks 

associated with potential increased use 

of HCFO-1224yd(Z) are adequately 

managed by SNAP. The EPA does not 

expect significant use of HCFO1224yd(Z) in applications not covered 

by the SNAP program. To the extent that 


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88946 Federal Register / Vol. 89, No. 218 / Tuesday, November 12, 2024 / Proposed Rules 

the compound is used in other 

applications not already reviewed under 

SNAP or under the New Chemicals 

Program under TSCA, the SNUR in 

place under TSCA requires that any 

significant new use of a chemical be 

reported to the EPA using a SNUN. Any 

significant new use of HCFO-1224yd(Z) 

would, thus, need to be evaluated by the 

EPA, and the EPA will continually 

review the availability of acceptable 

substitute chemicals under the SNAP 

program. 

IV. Proposed Action 

The EPA is responding to the petition 

by proposing to revise its regulatory 

definition of VOC at 40 CFR 51.100(s) to 

add HCFO-1224yd(Z) to the list of 

compounds that are exempt from the 

regulatory definition of VOC because it 

is less reactive than ethane based on a 

comparison of mass-based MIR and 

molar-based MIR metrics and is, 

therefore, considered negligibly 

reactive. As a result of this action, if an 

entity uses or produces this compound 

and is subject to the EPA regulations 

limiting the use of VOC in a product, 

limiting the VOC emissions from a 

facility, or otherwise controlling the use 

of VOC for purposes related to attaining 

the O3 NAAQS, this compound will not 

be counted as a VOC in determining 

whether these regulatory obligations 

have been met. This action would affect 

whether this compound is considered a 

VOC for State regulatory purposes to 

reduce O3 formation, if a State relies on 

the EPA’s regulatory definition of VOC. 

States are not bound to exclude from 

control as a VOC those compounds that 

the EPA has found to be negligibly 

reactive. However, no State may take 

credit for controlling this compound in 

its O3 control strategy. Consequently, 

reductions in emissions for this 

compound will not be considered or 

counted in determining whether States 

have met the rate of progress 

requirements for VOC in State 

Implementation Plans or in 

demonstrating attainment of the O3

NAAQS. 

V. 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) 

This action does not impose an 

information collection burden under the 

PRA. It does not contain any 

recordkeeping or reporting 

requirements. 

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. This action will not 

impose any requirements on small 

entities. This action removes HCFO1224yd(Z) from the regulatory definition 

of VOC and, thereby, relieves 

manufacturers, distributers, and users of 

the compound from tropospheric O3

requirements to control emissions of the 

compound. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain an 

unfunded mandate as described in 

UMRA, 2 U.S.C. 1531–1538, and does 

not significantly or uniquely affect small 

governments. This action imposes no 

enforceable duty on any State, local or 

Tribal governments, or the private 

sector. 

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 States, 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. This proposed rule 

removes HCFO-1224yd(Z) from the 

regulatory definition of VOC and, 

thereby, relieves manufacturers, 

distributers, and users from 

tropospheric O3 requirements to control 

emissions of the compound. Thus, 

Executive Order 13175 does not apply 

to this action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

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. This action is not 

subject to Executive Order 13045, 

because it is not economically 

significant as defined in Executive 

Order 12866, and because the EPA does 

not believe the environmental health or 

safety risks addressed by this action 

present a disproportionate risk to 

children. Our assessment is consistent 

with the SNAP finding that the 

conditional use of this chemical will 

guarantee the reduction of exposure 

risks to the general population 

particularly the most sensitive 

population (e.g., children). Since HCFO1224yd(Z) is utilized in specific 

industrial applications where children 

are not present and dissipates quickly 

(e.g., lifetime of 22 days) with shortlived end products, there is no exposure 

or disproportionate risk to children. 

This action removes HCFO-1224yd(Z) 

from the regulatory definition of VOC 

and, thereby, relieves manufacturers, 

distributers, and users from 

tropospheric O3 requirements to control 

emissions of the compound. 

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) 

This rulemaking does not involve 

technical standards. 

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 and environmental conditions 

that exist prior to this action do not 

result in disproportionate and adverse 

effects on communities with EJ 

concerns. As we found no data available 

to support the opposite, we addressed 

the human health and environmental 

risks by this proposed action to the 

greatest ability feasible. This action was 

developed in accordance with agency 

guidance on environmental justice. 

The EPA believes that this action in 

not likely to result in new 

disproportionate and adverse effects on 

communities with environmental justice 

concerns. This action removes HCFO1224yd(Z) from the regulatory definition 


khammond on DSKJM1Z7X2PROD with PROPOSALS
Federal Register / Vol. 89, No. 218 / Tuesday, November 12, 2024 / Proposed Rules 88947 

of VOC and, thereby, relieves 

manufacturers, distributers, and users of 

the compound from tropospheric O3

requirements to control emissions of the 

compound. It will in fact help States 

focus on more photochemically reactive 

chemicals preventing more formation of 

Ozone and consequently more adverse 

related health and environmental 

effects. 

K. Judicial Review 

Under section 307(b)(1) of the CAA, 

petitions for judicial review of this 

action must be filed in the United States 

Court of Appeals for the District of 

Columbia Circuit Court within 60 days 

from the date the proposed action is 

published in the Federal Register. 

Filing a petition for review by the 

Administrator of this proposed action 

does not affect the finality of this action 

for the purposes of judicial review nor 

does it extend the time within which a 

petition for judicial review must be filed 

and shall not postpone the effectiveness 

of such action. Thus, any petitions for 

review of this action related to the 

exemption of HCFO-1224yd(Z) from the 

regulatory definition of VOC must be 

filed in the Court of Appeals for the 

District of Columbia Circuit within 60 

days from the date proposed action is 

published in the Federal Register. 

VII. References 

AGC. (2016) (Z)-1-Chloro-2,3,3,3- 

tetrafluoropropene Refrigerant Gas Safety 

Data Sheet. ASAHI GLASS CO., LTD. 

Tokyo 100–8405, Japan August 2016. 

AGC Chemicals. (2017). AMOLEA® 1224yd, 

Technical Information, ASAHI Glass Co., 

Ltd. (pp. 1–18). 

Atkinson, R., Baulch, D.L., Cox, R.A., 

Crowley, J.N., Hampson, Jr., R.F., Hynes, 

R.G., Jenkin, M.E., Kerr, J.A., Rossi, M.J., 

and Troe, J. (2006) Evaluated kinetic and 

photochemical data for atmospheric 

chemistry: Volume II—gas phase 

reactions of organic species. Atmos. 

Chem. Phys. 6: 3625–4055. 

Baasandorj, M., Ravishankara, A.R., 

Burkholder, J.B. (2011) Atmospheric 

chemistry of (Z)-CF3CH=CHCF3: OH 

radical reaction rate coefficient and 

global warming potential. J Phys Chem 

A. 2011 Sep 29;115(38):10539–49. doi: 

10.1021/jp206195g. 

Carter, W.P.L. (1994) Development of ozone 

reactivity scales for volatile organic 

compounds. J. Air Waste Manage, 44: 

881–899. 

Carter, W.P.L. (2011) SAPRC Atmospheric 

Chemical Mechanisms and VOC 

Reactivity Scales, at https://

www.engr.ucr.edu/∼carter/SAPRC/. Last 

updated in Sept. 14, 2013. Tables of 

Maximum Incremental Reactivity (MIR) 

Values available at https://

www.arb.ca.gov/regact/2009/mir2009/ 

mir2009.htm. May 11, 2011. 

Osterstrom, F.F., Andersen, S.T., S<lling, T.I., 

Nielsena, OJ., and Andersen, M.P.S. 

(2017) Atmospheric chemistry of Z- and 

E-CF3CH--CHCF3: 

Phys.Chem.Chem.Phys., 2017, 19, 735. 

Tokuhashi, K., Uchimaru, T., Takizawa, K., & 

Kondo, S. (2018). Rate Constants for the 

Reactions of OH Radical with the (E)/(Z) 

Isomers of CF3CF=CHCl and 

CHF2CF=CHCl. The Journal of Physical 

Chemistry A, 122(12), 3120–3127. 

https://doi.org/10.1021/ 

acs.jpca.7b11923. 

USEPA, 2019. Protection of Stratospheric 

Ozone: Determination 35 for Significant 

New Alternatives Policy Program 

November 25, 2019. 84 FR 64765. 

Available online at: https://

www.govinfo.gov/content/pkg/FR-2019- 

11-25/pdf/2019-25412.pdf. 

List of Subjects in 40 CFR Part 51 

Environmental protection, 

Administrative practice and procedure, 

Air pollution control, Ozone, Reporting 

and recordkeeping requirements, 

Volatile organic compounds. 

Michael S. Regan, 

Administrator. 

For reasons stated in the preamble, 

title 40, chapter I of the Code of Federal 

Regulations is proposed to be amended 

as follows: 

PART 51—REQUIREMENTS FOR 

PREPARATION, ADOPTION, AND 

SUBMITTAL OF IMPLEMENTATION 

PLANS 

■ 1. The authority citation for part 51 

continues to read as follows: 

Authority: 23 U.S.C. 101; 42 U.S.C. 7401– 

7671q. 

Subpart F—Procedural Requirements 

■ 2. Section 51.100 is amended by 

revising paragraph (s)(1) introductory 

text to read as follows: 

§ 51.100 Definitions. 

* * * * * 

(s) * * * 

(1) This includes any such organic 

compound other than the following, 

which have been determined to have 

negligible photochemical reactivity: 

methane; ethane; methylene chloride 

(dichloromethane); 1,1,1-trichloroethane 

(methyl chloroform); 1,1,2-trichloro1,2,2-trifluoroethane (CFC–113); 

trichlorofluoromethane (CFC–11); 

dichlorodifluoromethane (CFC–12); 

chlorodifluoromethane (HCFC–22); 

trifluoromethane (HFC–23); 1,2-dichloro 

1,1,2,2-tetrafluoroethane (CFC–114); 

chloropentafluoroethane (CFC–115); 

1,1,1-trifluoro 2,2-dichloroethane 

(HCFC–123); 1,1,1,2-tetrafluoroethane 

(HFC–134a); 1,1-dichloro 1-fluoroethane 

(HCFC–141b); 1-chloro 1,1- 

difluoroethane (HCFC–142b); 2-chloro1,1,1,2-tetrafluoroethane (HCFC–124); 

pentafluoroethane (HFC–125); 1,1,2,2- 

tetrafluoroethane (HFC–134); 1,1,1- 

trifluoroethane (HFC–143a); 1,1- 

difluoroethane (HFC–152a); 

parachlorobenzotrifluoride (PCBTF); 

cyclic, branched, or linear completely 

methylated siloxanes; acetone; 

perchloroethylene (tetrachloroethylene); 

3,3-dichloro-1,1,1,2,2- 

pentafluoropropane (HCFC–225ca); 1,3- 

dichloro-1,1,2,2,3-pentafluoropropane 

(HCFC–225cb); 1,1,1,2,3,4,4,5,5,5- 

decafluoropentane (HFC 43–10mee); 

difluoromethane (HFC–32); 

ethylfluoride (HFC–161); 1,1,1,3,3,3- 

hexafluoropropane (HFC–236fa); 

1,1,2,2,3-pentafluoropropane (HFC– 

245ca); 1,1,2,3,3-pentafluoropropane 

(HFC–245ea); 1,1,1,2,3- 

pentafluoropropane (HFC–245eb); 

1,1,1,3,3-pentafluoropropane (HFC– 

245fa); 1,1,1,2,3,3-hexafluoropropane 

(HFC–236ea); 1,1,1,3,3- 

pentafluorobutane (HFC–365mfc); 

chlorofluoromethane (HCFC–31); 1 

chloro-1-fluoroethane (HCFC–151a); 1,2- 

dichloro-1,1,2-trifluoroethane (HCFC– 

123a); 1,1,1,2,2,3,3,4,4-nonafluoro-4- 

methoxy-butane (C4F9OCH3 or HFE– 

7100); 2-(difluoromethoxymethyl)- 

1,1,1,2,3,3,3-heptafluoropropane 

((CF3)2CFCF2OCH3); 1-ethoxy1,1,2,2,3,3,4,4,4-nonafluorobutane 

(C4F9OC2H5 or HFE–7200); 2- 

(ethoxydifluoromethyl)-1,1,1,2,3,3,3- 

heptafluoropropane 

((CF3)2CFCF2OC2H5); methyl acetate; 

1,1,1,2,2,3,3-heptafluoro-3-methoxypropane (n-C3F7OCH3, HFE–7000); 3- 

ethoxy- 1,1,1,2,3,4,4,5,5,6,6,6- 

dodecafluoro-2-(trifluoromethyl) hexane 

(HFE–7500); 1,1,1,2,3,3,3- 

heptafluoropropane (HFC 227ea); 

methyl formate (HCOOCH3); 

1,1,1,2,2,3,4,5,5,5-decafluoro-3- 

methoxy-4-trifluoromethyl-pentane 

(HFE–7300); propylene carbonate; 

dimethyl carbonate; trans-1,3,3,3- 

tetrafluoropropene; HCF2OCF2H (HFE– 

134); HCF2OCF2OCF2H (HFE–236cal2); 

HCF2OCF2CF2OCF2H (HFE–338pcc13); 

HCF2OCF2OCF2CF2OCF2H (H-Galden 

1040x or H-Galden ZT 130 (or 150 or 

180)); trans 1-chloro-3,3,3-trifluoroprop1-ene; 2,3,3,3-tetrafluoropropene; 2- 

amino-2-methyl-1-propanol; t-butyl 

acetate; 1,1,2,2- Tetrafluoro -1-(2,2,2- 

trifluoroethoxy) ethane; cis-1,1,1,4,4,4- 

hexafluorobut-2-ene (HFO–1336mzz-Z); 

(Z)-1-chloro-2,3,3,3-tetrafluoropropene 

(HCFO-1224yd(Z)); and perfluorocarbon 

compounds which fall into these 

classes: 

* * * * * 

[FR Doc. 2024–25971 Filed 11–8–24; 8:45 am] 

BILLING CODE 6560–50–P 


khammond on DSKJM1Z7X2PROD with PROPOSALS