Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 70595 

1Hearn A.G. (1961). Absorption of ozone in ultraviolet and visible regions of spectrum, Proc. Phys. 

Soc. 78 932, DOI: 10.1088/0370–1328/78/5/340. 

2Hodges, J.T., Viallon, J., Brewer, P.J., Drouin, 

B.J., Gorshelev, V., Janssen, C., Lee, S., Possolo, A., 

Smith, M.A.H., Walden, and Wielgosz, R.I. (2019). 

Recommendation of a consensus value of the ozone 

absorption cross-section at 253.65 nm based on a 

literature review, Metrologia, 56, 034001. https://

doi.org/10.1088/1681-7575/ab0bdd. 

3https://www.bipm.org/en/committees/cc/ccqm/ 

wg/ccqm-gawg-ozone-tg. 

transiting through, anchoring in, or 

remaining within the regulated area 

unless authorized by the COTP San Juan 

or a designated representative. 

(2) Persons and vessels desiring to 

enter, transit through, anchor in, or 

remain within the regulated area may 

contact the COTP San Juan by telephone 

at (787) 289–2041, or a designated 

representative via VHF–FM radio on 

channel 16 to request authorization. If 

authorization is granted, all persons and 

vessels receiving such authorization 

must comply with the instructions of 

the COTP San Juan or a designated 

representative. 

(3) The Coast Guard will provide 

notice of the regulated area by Local 

Notice to Mariners, Broadcast Notice to 

Mariners via VHF–FM channel 16, or 

the COTP’s designated representative. 

(d) Enforcement period. This section 

will be enforced from 6 a.m. until 6 p.m. 

on October 6, 2023, through October 20, 

2023. 

Dated: October 6, 2023. 

Jose ́ E. Dı ́az, 

Captain, U.S. Coast Guard, Captain of the 

Port San Juan. 

[FR Doc. 2023–22595 Filed 10–11–23; 8:45 am] 

BILLING CODE 9110–04–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 50 

[EPA–HQ–OAR–2022–0007; FRL–9344–02– 

OAR] 

RIN 2060–AV63 

Reference Measurement Principle and 

Calibration Procedure for the 

Measurement of Ozone in the 

Atmosphere (Chemiluminescence 

Method) 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is finalizing an update to 

the current ozone absorption crosssection to the recommended consensusbased cross-section value of 

1.1329x10¥17 cm2 molecule¥1 or 304.39 

atm¥1 cm¥1, with an uncertainty of 

0.94 atm¥1 cm¥1. The new value is 

1.2% lower than the current value of 

308 atm¥1 cm¥1 and reduces the 

uncertainty in the value to 0.31%. The 

adoption of this updated ozone 

absorption cross-section could result in 

increases in measured ozone 

concentrations but given the existing 

sources of potential variability in 

monitoring data, it is unlikely that there 

will be any consistent measurable and 

predictable effect on reported data. The 

EPA is also updating the dates of 

publication for two references 

associated with the updated crosssection value, adding a new reference, 

and making a technical correction to 

move three figures inadvertently placed 

in section 6.0 References to a new 

section 7.0 Figures. 

DATES: This final rule is effective on 

November 13, 2023. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

No. EPA–HQ–OAR–2022–0007. All 

documents in the docket are listed on 

the https://www.regulations.gov 

website. Although listed in the index, 

some information is not publicly 

available, e.g., CBI or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the internet and will be publicly 

available only in hard copy form. 

Publicly available docket materials are 

available electronically through https:// 

www.regulations.gov. 

FOR FURTHER INFORMATION CONTACT: Ms. 

Joann Rice, Office of Air Quality 

Planning and Standards, Air Quality 

Assessment Division, Ambient Air 

Monitoring Group (C304–06), 

Environmental Protection Agency, 

Research Triangle Park, North Carolina 

27711; telephone number: (919) 541– 

3372; email address: rice.joann@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

Organization of this document. The 

information in this preamble is 

organized as follows: 

Table of Contents 

I. Background 

Comments on the Proposed Rule 

II. Statutory and Executive Orders 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) 

J. Executive Order 12898: Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations 

K. Congressional Review Act (CRA) 

I. Background 

In 1961, the ozone absorption crosssection was measured to be 1.1476 

x10¥17 cm2 molecule¥1 or 308.3 

atmosphere (atm)¥1 centimeter (cm)¥1

with a reported relative standard 

uncertainty of 1.4% (Hearn, 1961).1 In 

the 1980s, the National Institute of 

Standards and Technology (NIST), in 

collaboration with the EPA, developed 

the Standard Reference Photometer 

(SRP), which is the international 

standard for the measurement of ozone. 

The SRP is based on ultraviolet (UV) 

photometry and uses this cross-section 

value as the reference value for UV 

ozone measurements. To establish and 

maintain traceability, the readings of an 

ozone analyzer are compared to a NISTmade ozone SRP through a hierarchy of 

standards. Efforts to improve the 

accuracy of the ozone absorption crosssection have continued over several 

years during which rigorous assessment 

of the bias and uncertainty in the value 

became a high priority. 

The Gas Analysis Working Group of 

the Consultive Committee for Metrology 

in Chemistry and Biology (CCQM– 

GAWG) of the Bureau of Weights and 

Measures in France (BIPM) convened a 

task group in 2016 to review all 

published measurements of the ozone 

cross-section since 1950. This task 

group was also charged with 

recommending a consensus-based crosssection value and associated uncertainty 

for adoption in measurements of ozone 

concentrations by standard UV 

photometric instruments, including the 

SRP. (Hodges et al., 2019).2

After publication in Hodges et al., 

2019, the CCQM–GAWG 3 convened an 

international group of stakeholders in 

October 2020 to discuss adopting and 

implementing a globally coordinated 

change in the cross-section value for 

surface ozone monitoring. This group, 

representing several international and 

national metrology institutes, NIST, and 

environmental agencies including EPA, 

agreed to adopt and implement the new 

cross-section value as it represents a 

more accurate value with less 


ddrumheller on DSK120RN23PROD with RULES1
70596 Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 

4Quality Assurance Handbook for Air Pollution 

Measurement Systems, Volume II, EPA–454/B–17– 

001, Jan. 2017, available at: https://www.epa.gov/ 

sites/default/files/2020-10/documents/final_

handbook_document_1_17.pdf. 

5 Data obtained on 9/1/2022 from EPA’s Ozone 

Data Quality Dashboard: https://sti-rshiny.shinyapps.io/ozone_dashboard/. 

6Appendix D, Measurement Quality Objectives 

and Validation Templates: https://www.epa.gov/ 

sites/default/files/2020-10/documents/app_d_

validation_template_version_03_2017_for_amtic_

rev_1.pdf. 

uncertainty and is an advancement and 

improvement in the UV photometer 

measurement method. 

40 CFR part 50, appendix D, 

‘‘Reference Measurement Principle and 

Calibration Procedure for the 

Measurement of Ozone in the 

Atmosphere,’’ currently provides EPA’s 

ozone calibration procedure with a 

stated value of 308 ± 4 atm¥1 cm¥1. 

This final action updates the ozone 

absorption cross-section to align with 

the BIPM CCQM–GAWG’s updated 

international cross-section value of 

304.39 atm¥1 cm¥1 with an uncertainty 

of 0.94 atm¥1 cm¥1 at standard 

temperature and pressure of 0 °C and 1 

atmosphere. The EPA agrees that the 

new cross-section value results in an 

improvement in the accuracy of surface 

ozone monitoring measurements by 

reducing uncertainty and is finalizing 

the change in appendix D of part 50 to 

this more accurate consensus value. 

The updated value reduces the 

uncertainty to 0.31% from the current 

1.4%. The value is also 1.2% lower than 

the current value of 308 atmosphere 

atm¥1 cm¥1, a change that could result 

in increases in measured ozone 

concentrations. However, there are 

several factors that EPA believes make 

it unlikely that this change will have a 

measurable, predictable influence on 

any particular set of ozone monitoring 

data. 

Design values, the metric used to 

compare ambient ozone concentrations 

measured at a monitor to the National 

Ambient Air Quality Standard (NAAQS) 

to determine compliance, are 

determined using the data reporting, 

data handling, and computation 

procedures provided in 40 CFR part 50, 

appendix U, ‘‘Interpretation of the 

Primary and Secondary National 

Ambient Air Quality Standards for 

Ozone.’’ 

Multiple factors can contribute to 

variability in monitoring data and 

ultimately design values, including, but 

not limited to, the precision of the 

monitoring method, the acceptance 

criteria for Standard Reference 

Photometer (SRP) calibration and 

verification, the acceptance criterion for 

bench and field standards used to 

calibrate ozone monitors in the field, 

how agencies perform calibration and 

adjust analyzer response, the precision 

and bias acceptance criteria in EPA’s 

Quality Assurance (QA) Handbook,4

data handling and computation 

procedures in Appendix U, and 

meteorology. 

The inherent precision (variability) of 

the measurements from analyzers used 

to measure ozone is about ±1 ppb, or 

±0.001 ppm. The variability in the 

measurement in either the positive or 

negative direction should be considered 

relative to the change in monitoring data 

due to the new cross-section value. 

When the new cross-section value is 

implemented, all SRPs maintained by 

BIPM, NIST, and the EPA will be 

updated to incorporate the new value. 

The update will be achieved through 

software/firmware modification and 

will not require any hardware changes. 

The EPA is planning to update all 

Agency’s SRPs simultaneously, instead 

of through a phased approach, to 

minimize disruption of the SRP 

network. To establish and maintain 

traceability, the readings of an ozone 

analyzer are compared through a 

hierarchy of standards to a NIST ozone 

SRP. The process of using NISTtraceable standards to verify the ozone 

concentrations is implemented for all 

regulatory network ozone analyzers 

used for comparison to the NAAQS. 

There are 12 SRPs within the EPA’s 

network: three at EPA’s Office of 

Research and Development (ORD) and 

nine at various EPA Regional offices and 

the California Air Resources Board 

(CARB). One of ORD’s SRPs is sent to 

NIST to be re-verified against the NIST 

SRP annually. That SRP serves as the 

reference for the two other ORD SRPs. 

Each SRP in the U.S. is re-verified 

against one of ORD’s three SRPs 

annually. Under normal verification 

operations, implementing the ozone 

standards traceability process for the 

entire SRP network could take 2 or more 

years starting from when the SRP 

software/firmware is updated. During 

this time, the implementation progress 

and monitoring data collected with the 

new cross-section will need to be 

tracked. 

The acceptance criteria used in 

comparing the SRPs (Level 1 standards) 

to each other is a slope of 1.00 ± 0.01 

(or 1%) and an intercept 0.00 ± 1 ppb. 

Field and bench standards (Level 2 

standard) used to calibrate ozone 

analyzers in the field have acceptance 

criteria for the slope of 1.00 ± 0.03 (or 

3%) and an intercept of 0 ± 3 ppb. The 

1.2% change in cross-section value is 

well within the 3% acceptance for Level 

2 standards. 

The goal for annual measurement 

uncertainty for ozone in 40 CFR part 58, 

‘‘Ambient Air Quality Surveillance,’’ is 

an upper 90 percent confidence limit for 

the coefficient of variation of 7% for 

precision and for bias an upper 95 

percent confidence limit of 7%. Bias 

and precision estimates are determined 

using data obtained from the 

comparison of the ozone analyzer 

response to one-point Quality Control 

(QC) checks using a Level 2 calibration 

standard. The 1.2% change in crosssection value is well within the bias and 

precision goal of 7%. Data reported to 

the EPA’s Air Quality System by state, 

local, and tribal monitoring agencies is 

used to assess bias and precision. The 

2021 national average precision for all 

ozone analyzers in the U.S. is 2.3% and 

the national average bias is 1.6%.5 The 

1.2% change is, therefore, within the 

national precision and less than the 

national bias. 

The QA Handbook, Volume II, 

Appendix D Validation Template 6 also 

specifies critical criteria for monitoring 

organizations to maintain the integrity 

and evaluate the quality of the data 

collected by the analyzer. The critical 

criteria are a one-point QC check (every 

14 days at a minimum) < ±7.1% 

difference or < ±1.5 ppb difference, 

whichever is greater; zero drift < ± 3.1 

ppb (over a 24-hour period) or < ±5.1 

ppb (>24 hours and up to 14 days); and 

span check drift over a 14-day period of 

< ±7.1%. Any change to monitoring data 

due to the new cross-section is also well 

within the 7.1% acceptance criteria. 

Monitoring organizations may manually 

adjust the analyzer response while 

others may institute automated 

adjustment through use of a data 

acquisition or data handling system. 

Automated adjustments to the ozone 

analyzer data are not recommended 

because the monitoring agency may not 

know if the standard being used for 

monitor comparison, or the analyzer, 

has degraded or drifted. 

Ozone analyzers are calibrated or 

verified every 182 days if one-point zero 

and span checks are performed every 14 

days, and every 365 days if one-point 

zero and span checks are done daily. 

The acceptance criteria for multi-point 

calibration are all points < ±2.1% or 

≤ ±1.5 ppb difference of the best fit 

straight line, whichever is greater, and 

a slope of 1 ± 0.05 or 5%. The 1.2% 

change is also well within this 

acceptance criteria for ozone monitor 

calibration. 

Ozone design values are computed as 

the 3-year average of the annual 4th 

highest daily maximum 8-hour value 


ddrumheller on DSK120RN23PROD with RULES1
Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 70597 

7See QA Handbook, Vol. II, App. D, 

Measurement Quality Objectives and Validation 

Templates, available at https://www.epa.gov/sites/ 

default/files/2020-10/documents/app_d_

validation_template_version_03_2017_for_amtic_

rev_1.pdf. 

measured at each monitoring site. 

Appendix U provides for three levels of 

truncation for the hourly, daily 8-hour 

maximum, and design value 

calculations. Hourly averaged ozone 

monitoring data are to be reported in 

ppm to the third decimal place, with 

additional digits to the right truncated 

(e.g., 0.070 ppm). In assessing how and 

if the updated cross-section value may 

affect ozone design values, it is 

important to note that other factors, 

including meteorology, can also 

influence design values. The effects of 

meteorology on hourly ozone 

concentrations can contribute to an 

increase or decrease in design values for 

a site because formation of ozone is 

heavily dependent on meteorological 

conditions. Interannual meteorological 

variations are known to affect daily and 

seasonal average ozone concentrations. 

Therefore, while we do not have reason 

to believe this proposal will 

significantly increase design values, 

meteorology would be a confounding 

factor in determining the effect on 3- 

year design values. 

Taking these factors into 

consideration, the EPA believes it is 

unlikely that the cross-section change 

will have a measurable, predictable 

influence on any given ozone design 

value or monitoring data set. 

Because the EPA believes that 

adoption of the new cross-section will 

improve the accuracy of measured 

ozone values and is unlikely to have a 

measurable, predictable influence on 

any given monitor or design value, the 

EPA is finalizing its proposal to revise 

the current ozone absorption crosssection to the recommended 

international consensus-based crosssection value of 304.39 atm¥1 cm¥1, 

with an uncertainty of 0.94 atm¥1

cm¥1. 

Ozone analyzers are traceable to a 

NIST standard reference UV-based 

photometer with a specified ozone UV 

absorption cross-section value. The 

absorption cross-section value stated 

this appendix (304.39 atm¥1 cm¥1 ± 

0.94 atm¥1 cm¥1) will be implemented 

January 1, 2025, with an additional year 

for state, local, and tribal monitoring 

agencies to complete implementation, to 

January 1, 2026. Until January 1, 2025, 

the previous ozone absorption crosssection value (308 ± 4 atm¥1 cm¥1) will 

be used. After January 1, 2025, both 

cross-section values, 304.39 ± 0.94 

atm¥1 cm¥1 and 308 ± 4 atm¥1 cm¥1, 

may be used. After January 1, 2026, only 

the cross-section value of 304.39 ± 0.94 

atm¥1 cm¥1 may be used. EPA 

recognizes the challenges, complexity, 

and time it will take to develop 

guidance and complete implementation 

of the updated cross-section value and 

is, therefore, delaying the proposed 

implementation start date of January 1, 

2024, until January 1, 2025, with an 

additional year (to January 1, 2026) to 

complete implementation. 

The EPA is including an additional 

published reference for the research 

done to support the cross-section 

change in 40 CFR part 50, appendix D, 

section 6.0 References: Hodges, J.T., 

Viallon, J., Brewer, P.J., Drouin, B.J., 

Gorshelev, V., Janssen, C., Lee, S., 

Possolo, A., Smith, M.A.H., Walden, 

and Wielgosz, R.I., ‘‘Recommendation of 

a consensus value of the ozone 

absorption cross-section at 253.65 nm 

based on a literature review,’’ 

Metrologia, 56 (2019) 034001, https://

doi.org/10.1088/1681-7575/ab0bdd. The 

EPA is also changing the publication 

dates of two existing references 

associated with the updated crosssection value in 40 CFR part 50, 

appendix D, section 6.0 References. 

Comments on the Proposed Rule 

On February 24, 2023, the EPA 

proposed to update the current ozone 

absorption cross-section (88 FR 11835) 

and solicited comment on the proposed 

update. The EPA received two 

comments by the close of the public 

comment period on March 27, 2023. 

One commenter expressed concern that 

the proposed target date of January 1, 

2024, provides insufficient time to 

implement the new cross-section value 

and noted that monitoring equipment 

that is no longer supported by 

manufacturers would require 

monitoring agencies to purchase new 

ozone monitoring equipment. 

In further consideration of global 

implementation of the updated crosssection value, the international task 

group leading implementation and the 

EPA recognize the challenges, 

complexity, and time it will take to 

implement the updated value and are 

accordingly delaying the 

implementation start date from January 

2024 until January 2025 with an 

additional year (to January 2026) to 

complete implementation. Regarding 

the assertion that some monitoring 

agencies will be required to purchase 

new equipment, existing equipment will 

be adjusted by firmware updates if 

available. Where firmware updates are 

not available for certain monitors, those 

monitors may instead be calibrated 

against ozone transfer standards, which 

are calibrated directly back to a 

Standard Reference Photometer (SRP) 

using the updated cross-section value. 

Therefore, the purchase of new 

equipment should not be required. 

A second comment on the proposed 

cross-section value assumed that the 

percentage increase in monitoring data 

would be 0.00086 ppm at the current 

level of the standard (0.070 ppm). The 

commenter noted that, if that increase 

had been applied to the health studies 

upon which the current NAAQS is 

based, ‘‘a NAAQS closer to 71 ppb very 

well could have been chosen based on 

the monitoring data.’’ The commenter 

also noted that under the current ozone 

reconsideration, the Clean Air Science 

Advisory Committee (CASAC) and EPA 

‘‘must’’ consider the ozone cross-section 

change on monitoring data and health 

effect studies and, if not considered, the 

NAAQS may be ‘‘artificially lowered’’ or 

more stringent. 

The EPA disagrees that this change 

will make the NAAQS ozone standard 

more stringent. As described in the 

proposed action, at the current level of 

the standard (0.070 ppm), 0.00086 ppm 

is within the current precision of the 

measurement method which is +/- 0.001 

ppm. Moreover, when viewed in 

conjunction with the current monitor 

calibration acceptance criteria 7, the use 

of truncation conventions for the ozone 

hourly, daily 8-hour maximum, and 

design value calculations, and other 

unpredictable factors, EPA disagrees 

with the commenter’s suggestion that 

the change will result in any consistent 

measurable and predictable effect on 

reported data. This inherent 

measurement variability is already 

included in the measurements that have 

been and are being used in health effects 

research studies related to the ozone 

NAAQS. The CASAC is aware of this 

action, which is required to bring the 

U.S. into alignment with international 

monitoring standards. 

No other comments were received. 

The EPA is finalizing this action as 

proposed. 

II. Statutory and Executive Orders 

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 by 

Executive Order 12866, as amended by 


ddrumheller on DSK120RN23PROD with RULES1
70598 Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 

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. This action revises the ozone 

absorption cross-section and revise and 

amend relevant references. It does not 

contain any information collection 

activities. 

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. In making this 

determination, the EPA concludes that 

the impact of concern for this rule is any 

significant adverse economic impact on 

small entities and that the agency is 

certifying that this rule will not have a 

significant economic impact on a 

substantial number of small entities if 

the rule has no net burden on the small 

entities subject to the rule. This action 

updates the ozone absorption crosssection value for surface ozone 

monitoring under 40 CFR part 50, and 

we anticipate that there will be minimal 

costs associated with this change. We 

have, therefore, concluded that this 

action will have no net regulatory 

burden for all directly regulated small 

entities. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain any 

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 action updates a 

reference measurement principle and 

calibration procedure for the 

measurement of ambient ozone under 

40 CFR part 50. Thus, Executive Order 

13175 does not apply to this action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

The EPA interprets Executive Order 

13045 as applying only to those 

regulatory actions that concern 

environmental health or safety risks that 

the EPA has reason to believe may 

disproportionately affect children, per 

the definition of ‘‘covered regulatory 

action’’ in section 2–202 of the 

Executive Order. This action is not 

subject to Executive Order 13045 

because it does not concern an 

environmental health risk or safety risk. 

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 involves technical 

standards. The EPA used voluntary 

consensus standards in the preparation 

of this measurement principle and 

procedure; it is the benchmark against 

which all ambient ozone monitoring 

methods are compared. This action is 

simply updating the reference 

measurement principle in light of 

updated information. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

Executive Order 12898 (59 FR 7629, 

Feb.16, 1994) directs Federal agencies, 

to the greatest extent practicable and 

permitted by law, to make 

environmental justice part of their 

mission by identifying and addressing, 

as appropriate, disproportionately high 

and adverse human health or 

environmental effects of their programs, 

policies, and activities on minority 

populations (people of color) and lowincome populations. 

The EPA believes that this type of 

action does not concern human health 

or environmental conditions and, 

therefore, cannot be evaluated with 

respect to potentially disproportionate 

and adverse effects on people of color, 

low-income populations and/or 

indigenous peoples. This regulatory 

action is an update to a previously 

promulgated analytical method and 

does not have any impact on human 

health or the environment. 

K. Congressional Review Act (CRA) 

This action is subject to the CRA, and 

the EPA will submit a rule report to 

each house of the Congress and to the 

Comptroller General of the United 

States. This action is not a ‘‘major rule’’ 

as defined by 5 U.S.C. 804(2). 

List of Subjects in 40 CFR Part 50 

Environmental protection, Air 

pollution control, Ozone. 

Michael S. Regan, 

Administrator. 

For the reasons set forth in the 

preamble, the EPA amends title 40, 

chapter I of the Code of Federal 

Regulations as follows: 

PART 50—NATIONAL PRIMARY AND 

SECONDARY AMBIENT AIR QUALITY 

STANDARDS 

■ 1. The authority citation for part 50 

continues to read as follows: 

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

■ 2. Amend appendix D to part 50 by: 

■ a. Revising sections 2.2, 4.1 and 

4.5.3.10; 

■ b. Revising references 13. and 14. in 

section 6.0; 

■ c. Removing figures 1., 2., and 3. in 

section 6.0; 

■ d. Adding reference 15 in section 6.0; 

and 

■ e. Adding section ‘‘7.0 Figures.’’. 

The revisions and addition read as 

follows: 

Appendix D to Part 50—Reference 

Measurement Principle and Calibration 

Procedure for the Measurement of 

Ozone in the Atmosphere 

(Chemiluminescence Method) 

* * * * * 

2.0 Measurement Principle. 

* * * * * 

2.2 The measurement system is 

calibrated by referencing the 

instrumental chemiluminescence 

measurements to certified O3 standard 

concentrations generated in a dynamic 

flow system and assayed by ultraviolet 

(UV) photometry to be traceable to a 

National Institute of Standards and 

Technology (NIST) standard reference 

photometer for O3 (see section 4, 

Calibration Procedure, below) with a 

specified ozone absorption cross-section 

value. The absorption cross-section 

value stated in section 4.1 and section 

4.5.3.10 of this appendix (304.39 atm¥1

cm¥1 ± 0.94 atm¥1 cm¥1) will be 

implemented January 1, 2025, with an 

additional year to complete 

implementation (January 1, 2026). Until 

January 1, 2025, the previous ozone 

absorption cross-section value, 308 ± 4 


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Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 70599 

atm¥1 cm¥1, will be used. After January 

1, 2025, both cross-section values, 

304.39 ± 0.94 atm¥1 cm¥1 and 308 ± 4 

atm¥1 cm¥1, may be used. After January 

1, 2026, only the cross-section value of 

304.39 ± 0.94 atm¥1 cm¥1 may be used. 

* * * * * 

4.0 Calibration Procedure. 

4.1 Principle. The calibration 

procedure is based on the photometric 

assay of O3 concentrations in a dynamic 

flow system. The concentration of O3 in 

an absorption cell is determined from a 

measurement of the amount of 254 nm 

light absorbed by the sample. This 

determination requires knowledge of (1) 

the absorption coefficient (a) of O3 at 

254 nm, (2) the optical path length (l) 

through the sample, (3) the 

transmittance of the sample at a 

nominal wavelength of 254 nm, and (4) 

the temperature (T) and pressure (P) of 

the sample. The transmittance is 

defined as the ratio I/I0, where I is the 

intensity of light which passes through 

the cell and is sensed by the detector 

when the cell contains an O3 sample, 

and I0 is the intensity of light which 

passes through the cell and is sensed by 

the detector when the cell contains zero 

air. It is assumed that all conditions of 

the system, except for the contents of 

the absorption cell, are identical during 

measurement of I and I0. The quantities 

defined above are related by the BeerLambert absorption law, 

BILLING CODE 6560–50–P 

Where: 

a = absorption coefficient of O3 at 254 nm = 

304.39 atm¥1 cm¥1, with an uncertainty 

of 0.94 atm¥1 cm¥1 at 0 °C and 1 atm. 1, 2, 3, 4, 5, 6, 7, 15

c = O3 concentration in atmospheres, and 

l = optical path length in cm. 

A stable O3 generator is used to 

produce O3 concentrations over the 

required calibration concentration 

range. Each O3 concentration is 

determined from the measurement of 

the transmittance (I/I0) of the sample at 

254 nm with a photometer of path 

length l and calculated from the 

equation, 

The calculated O3 concentrations 

must be corrected for O3 losses, which 

may occur in the photometer, and for 

the temperature and pressure of the 

sample. 

* * * * * 

4.5 Procedure. 

* * * * * 

4.5.3.10. Calculate the O3

concentration from equation 4. An 

average of several determinations will 

provide better precision. 

Where: 

[O3]OUT = O3 concentration, ppm 

a = absorption coefficient of O3 at 254 nm = 

304.39 atm¥1 cm¥1 at 0 °C and 1 atm 

l = optical path length, cm 

T = sample temperature, K 

P = sample pressure, torr 

L = correction factor for O3 losses from 

4.5.2.5 = (1¥fraction of O3 lost). 

Note: Some commercial photometers may 

automatically evaluate all or part of equation 

4. It is the operator’s responsibility to verify 

that all of the information required for 

equation 4 is obtained, either automatically 

by the photometer or manually. For 

‘‘automatic’’ photometers which evaluate the 

first term of equation 4 based on a linear 

approximation, a manual correction may be 

required, particularly at higher O3 levels. See 

the photometer instruction manual and 

Reference 13 for guidance. 

* * * * * 

6.0 References. 

* * * * * 

13. Technical Assistance Document 

for the Calibration of Ambient Ozone 

Monitors, EPA publication number 

EPA–454/B–22–003, January 2023. 

14. QA Handbook for Air Pollution 

Measurement Systems—Volume II. 

Ambient Air Quality Monitoring 

Program. EPA–454/B–17–001, January 

2017. 


ddrumheller on DSK120RN23PROD with RULES1ER12OC23.000</GPH> ER12OC23.001</GPH> ER12OC23.002</GPH>

Transmitance = ..!.. = e -acl 

Io 

c(atm) = - 2:. (in..!..) al I0 

or 

106 ( I) c(ppm) = -- In- . al I0 

( -1 I) ( T ) (760) 106 [03]ouT = -In- - - x- al 10 273 P L 

(1) 

(2a) 

(2b) 

(4) 
70600 Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 

15. Hodges, J.T., Viallon, J., Brewer, 

P.J., Drouin, B.J., Gorshelev, V., Janssen, 

C., Lee, S., Possolo, A., Smith, M.A.H., 

Walden, and Wielgosz, R.I., 

Recommendation of a consensus value 

of the ozone absorption cross-section at 

253.65 nm based on a literature review, 

Metrologia, 56 (2019) 034001. [Available 

at https://doi.org/10.1088/1681-7575/ 

ab0bdd.] 

7.0 Figures. 

Figure 1. Gas-phase chemiluminescence 

analyzer schematic diagram, where 

PMT means photomultiplier tube. 


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Pump 

Exhaust 

.. •! 

s:. iil .a 

2 K 0 w II) 

J 

Reaction Cell 

PMT 

NO or Ethylene 

Flow 

Sensor 

NO 

or Ethylene 

Pressure 

Regulator 

Nitric Oxide 

or Ethylene Gas 

Cylinder 
Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 70601 

Figure 2. Schematic diagram of a typical 

UV photometric calibration system. 


ddrumheller on DSK120RN23PROD with RULES1ER12OC23.004</GPH>

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70602 Federal Register / Vol. 88, No. 196 / Thursday, October 12, 2023 / Rules and Regulations 

1North American Industry Classification System. 

Figure 3. Schematic diagram of a typical 

UV photometric calibration system 

(Option 1). 

[FR Doc. 2023–22531 Filed 10–11–23; 8:45 am] 

BILLING CODE 6560–50–C 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 1090 

[EPA–HQ–OAR–2023–0289; FRL 10290–01– 

OAR] 

RIN 2060–AV87 

Reformulated Gasoline Covered Areas 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: In this final action, the 

Environmental Protection Agency (EPA) 

is amending its reformulated gasoline 

(RFG) regulations to reflect the 

reclassification of several ozone 

nonattainment areas as Severe for the 

2008 ozone national ambient air quality 

standard (NAAQS). The subject areas 

are the Dallas-Fort Worth, TX area 

(Dallas), the Denver-Boulder-GreeleyFort Collins-Loveland, CO area 

(Denver), and the Eastern Kern County, 

CA area (Eastern Kern). The 

reclassification of the Dallas and Denver 

areas as Severe for the 2008 ozone 

NAAQS was effective on November 7, 

2022, and results in the prohibition of 

the sale of conventional gasoline 

throughout the entire nonattainment 

area under the Clean Air Act (CAA) eon 

November 7, 2023. Similarly, the 

reclassification of the Eastern Kern area 

was effective on July 7, 2021, and the 

Federal RFG requirement applied to the 

area on July 7, 2022. 

DATES: This final rule is effective 

November 13, 2023. 

FOR FURTHER INFORMATION CONTACT: 

Mark Coryell, Office of Transportation 

and Air Quality, U.S. Environmental 

Protection Agency, 2000 Traverwood, 

Ann Arbor, MI 48105; email address: 

coryell.mark@epa.gov or Rudy 

Kapichak, Office of Transportation and 

Air Quality, U.S. Environmental 

Protection Agency, 2000 Traverwood, 

Ann Arbor, MI 48105; email address: 

kapichak.rudolph@epa.gov. 

SUPPLEMENTARY INFORMATION: The 

contents of this preamble are listed in 

the following outline: 

I. General Information 

II. Action 

III. Background 

IV. Public Participation 

V. Statutory and Executive Order Reviews 

VI. Legal Authority and Statutory Provisions 

I. General Information 

A. Does this action apply to me? 

Entities potentially affected by this 

final action are fuel producers and 

distributors who do business in the 

Dallas-Fort Worth, TX area, the DenverBoulder-Greeley-Fort Collins-Loveland, 

CO area, and the Eastern Kern County, 

CA area. 

Examples of potentially 

regulated entities 

NAICS1

codes 

Petroleum refineries ....................... 324110 

424710 

Gasoline Marketers and Distributors .............................................. 424720 

Gasoline Retail Stations ................. 457110 

457120 


ddrumheller on DSK120RN23PROD with RULES1ER12OC23.005</GPH>

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