AQ-2024-006-RULE510 REPORTTOBOS.PDF

Air Quality Department 
301 W. Jefferson St., Suite 410  
Phoenix, Arizona 85003 
 
P: 602-506-6010 
E: AQMail@maricopa.gov 
 
 
 
 
 
 
 
 
 
Executive Summary of the Report to the Board of Supervisors 
Prepared by Maricopa County Air Quality Department 
 
Board Hearing Date: 
November 6, 2024 
 
Case Number/Title:  
AQ-2024-006-Rule 510 (Air Quality Standards) 
 
Agenda Item:  
(Pending) 
 
Supervisor Districts:  
All Districts 
 
The Maricopa County Air Quality Department (MCAQD) complied with all statutory and county 
policies throughout this rulemaking process. Per the Enhanced Regulatory Outreach Program 
(EROP) Policy: “In addition to the required staff report, an executive summary of the report 
including an overview of stakeholder input and staff responses will be provided to the Board of 
Supervisors at least one week prior to any Board of Supervisors’ public hearing.” 
 
Overview of the Report to the Board of Supervisors: 
 
On February 7, 2024, the U.S. Environmental Protection Agency (EPA) revised the 
primary annual PM2.5 National Ambient Air Quality Standard (PM2.5 NAAQS) from 12 
micrograms per cubic meter (µg/m3) to 9.0 µg/m3. In response to the primary annual PM2.5 
NAAQS revision, MCAQD is proposing to revise Rule 510 (Air Quality Standards) to incorporate 
the new standard of 9.0 µg/m3. 
 
The purpose of Rule 510 is to establish ambient air quality standards per § 110(a) of the 
Clean Air Act (CAA), which are necessary to protect human health and public welfare. 
The standards implemented in Rule 510 incorporate the NAAQS as codified in 40 CFR 50 
“National Primary and Secondary Ambient Air Quality Standards”. 
 
States are required to submit an infrastructure state implementation plan (SIP) under 
Section 110(a) of the CAA that implements, maintains, and enforces new or revised NAAQS 
within three years of the EPA issuing the standard. Rule 510 supports the 
Maricopa County portion of Arizona’s infrastructure SIP.  
 
After the revised PM2.5 standard is incorporated into Rule 510, MCAQD will submit the rule as a 
revision to the Arizona SIP. 
 
Overview of Stakeholder Input and Staff Responses: 
 
No written comments were received regarding this rulemaking.

Maricopa County 
Air Quality Department 
Planning and Analysis Division 
Report to the 
Board of 
Supervisors 
 
Rule 510 (Air Quality 
Standards) 
November 2024

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
page 3 of 15 
Board Hearing Date: 
November 6, 2024  
Case Number/Title:  
AQ-2024-006-Rule 510 (Air Quality Standards) 
Agenda Item: 
(Pending) 
Supervisor Districts: 
All Districts 
Applicant:  
Staff 
Request: 
Approve the incorporation of the recently revised primary 
annual PM2.5 National Ambient Air Quality Standard (PM2.5 
NAAQS) into Rule 510 (Air Quality Standards) and approve 
submission of the revised rule as a revision to the Arizona 
State Implementation Plan (SIP).  
On February 7, 2024, the U.S. Environmental Protection 
Agency (EPA) revised the primary annual PM2.5 NAAQS from 
12 micrograms per cubic meter (µg/m3) to 9.0 µg/m3. In 
response to the primary annual PM2.5 NAAQS revision, 
MCAQD is proposing to revise Rule 510 to incorporate the 
new standard of 9.0 µg/m3. 
The purpose of Rule 510 is to establish ambient air quality 
standards per § 110(a) of the Clean Air Act (CAA), which are 
necessary to protect human health and public welfare. The 
standards implemented in Rule 510 incorporate the NAAQS 
as codified in 40 CFR 50 “National Primary and Secondary 
Ambient Air Quality Standards”.  
States are required to submit an infrastructure SIP under 
Section 110(a) of the CAA that implements, maintains, and 
enforces new or revised NAAQS within three years of the 
EPA issuing the standard. Rule 510 supports the Maricopa 
County portion of Arizona’s infrastructure SIP.  
After the revised PM2.5 standard is incorporated into Rule 
510, MCAQD will submit the rule as a revision to the Arizona 
SIP. 
Support/Opposition: 
No written comments were received regarding this 
rulemaking. 
Staff 
Recommendation:  
 
Approve 
 
Board of Health 
Recommendation: 
This regulatory change is following the Enhanced Regulatory 
Outreach Program (EROP) Policy as an Incorporation by 
Reference rulemaking. As such, it was not required to be 
reviewed by the Board of Health.

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
page 4 of 15 
Additional Comments: 
The Maricopa County Manager was briefed on this 
rulemaking on June 13, 2024. A Notice of Expedited 
Rulemaking was posted to EROP on July 24, 2024. A 
newspaper notice of the Board of Supervisors public hearing 
will be published in the Arizona Business Gazette on 
September 26, 2024, and on October 3, 2024. This regulatory 
change will take effect immediately upon approval by the 
Board of Supervisors. 
Presented By: 
Philip A. McNeely, R.G., Director 
Prepared By: 
Planning and Analysis Division 
Attachments: 
Preamble required by Arizona Revised Statutes 
(A.R.S.) § 49-471.08 (See the Draft Notice of Final 
Rulemaking) 
Summary of the proposed regulatory change (See 
Item #4 of the Draft Notice of Final Rulemaking) 
 
Analysis of input received during the process and 
how that input was responded to (See Item #9 of the 
Draft Notice of Final Rulemaking) 
 
Language of proposed regulatory change or 
amendment (See the Draft Notice of Final 
Rulemaking)  
 
Copies of all written and electronic Stakeholder 
input (no comments were received for this 
rulemaking)

Maricopa County 
Air Quality Department 
Planning and Analysis Division 
Draft Notice of 
Final 
Rulemaking 
 
Rule 510 
(Air Quality 
Standards) 
November 2024

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
page 6 of 15 
Draft Notice of Final Rulemaking 
Maricopa County Air Pollution Control Regulations 
Regulation V – Air Quality Standards and Area Classification 
Rule 510 (Air Quality Standards) 
The Maricopa County Air Quality Department (MCAQD) is proposing to incorporate the recently 
revised primary annual PM2.5 National Ambient Air Quality Standard (PM2.5 NAAQS) into Rule 510 
(Air Quality Standards). The Control Officer is posting this Draft Notice of Final Rulemaking on 
the Maricopa County Enhanced Regulatory Outreach Program (EROP) website as part of the 
Report to the Board of Supervisors, in accordance with the Maricopa County EROP Policy. This 
notice contains a preamble as prescribed in the Arizona Revised Statutes (A.R.S.) § 49-471.05, 
the written findings required by A.R.S. § 49-471.08.A.2, and the full text of the rule, including the 
intended action to amend sections of the rule. This notice also includes a list of all previous 
notices posted on the Maricopa County EROP website addressing the proposed rule and the 
concise explanatory statement prescribed in A.R.S. § 49-471.07(B). 
Preamble 
1.
Statutory authority for the rulemaking (A.R.S. § 49-471.05(1)):
A.R.S. §§ 49-112, 49-471.08, 49-474, 49-479, and 49-480
2.
Name and address of department personnel with whom persons may communicate
regarding the rulemaking (A.R.S. § 49-471.05(2)):
Name:
Hannah Luke or Kimberly Butler 
Maricopa County Air Quality Department 
Planning and Analysis Division 
Address: 
301 W. Jefferson St., Suite 410 
Phoenix, AZ 85003 
Telephone: 
602-506-6010 
Fax: 
602-506-6179 
Email: 
AQPlanning@maricopa.gov 
Online: 
Submit a Comment 
3.
Rulemaking process (A.R.S. § 49-471.05(3)):
This rulemaking is following the rulemaking requirements pursuant to A.R.S. § 49-
471.08 and the Maricopa County EROP Policy, incorporation by reference process.
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Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
page 7 of 15 
County Manager Briefing:  
June 13, 2024 
Notice of Expedited Rulemaking: 
July 24, 2024 
Board of Supervisors Formal Meeting to Set the Public Hearing: 
September 25, 2024 
Board of Supervisors Public Hearing: 
November 6, 2024 
4.
Explanation of the rule, including the control officer's reasons for initiating the
rulemaking (A.R.S. § 49-471.05(4)):
On February 7, 2024, the U.S. Environmental Protection Agency (EPA) revised the
primary annual PM2.5 NAAQS from 12 micrograms per cubic meter (µg/m3) to 9.0 µg/m3.
In response to the primary annual PM2.5 NAAQS revision, MCAQD is proposing to revise
Rule 510 (Air Quality Standards) to incorporate the new standard of 9.0 µg/m3.
The purpose of Rule 510 is to establish ambient air quality standards per § 110(a) of the
Clean Air Act (CAA), which are necessary to protect human health and public welfare.
The standards implemented in Rule 510 incorporate the NAAQS as codified in 40 CFR
50 “National Primary and Secondary Ambient Air Quality Standards”.
States are required to submit an infrastructure state implementation plan (SIP) under
Section 110(a) of the CAA that implements, maintains, and enforces new or revised
NAAQS within three years of the EPA issuing the standard. Rule 510 supports the
Maricopa County portion of Arizona’s infrastructure SIP.
After the revised PM2.5 standard is incorporated into Rule 510, MCAQD will submit the
rule as a revision to the Arizona SIP.
5.
Studies relied on in the control officer's evaluation of or justification for the rule and
where the public may obtain or review the studies, all data underlying the studies, any
analysis of the studies and other supporting material (A.R.S. § 49-471.05(5)).
MCAQD did not conduct or review any studies related to this expedited rulemaking
action. Any study, data, analysis, or other review of supporting material occurred during
the development of the federal standard is noted in the federal register notices.
6.
An economic, small business and consumer impact statement (A.R.S. § 49-
471.05(6)):
MCAQD is not required to prepare an economic, small business, and consumer impact
statement for an expedited rulemaking pursuant to A.R.S. § 41-1055(D)(2).
7.
The proposed effective date of the rule (A.R.S. § 49-471.05(7)):
The proposed effective date of this rulemaking is November 6, 2024.
8.
Such other matters as are prescribed by statute and that are applicable to the county
or to any specific rule or class of rules (A.R.S. § 49-471.05(8)):
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Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
page 8 of 15 
A.R.S. § 49-471.08(A)(2): 
Written finding by the Control Officer setting forth the reasons why the rule or ordinance 
making is necessary and does not alter the sense, meaning, or effect of the federal or 
state rule or law from which it is derived. 
This rulemaking is required as part of the State’s duty to submit an infrastructure SIP 
under Section 110(a) of the CAA that implements, maintains, and enforces new or 
revised NAAQS within three years of the EPA issuing the standard. Rule 510 supports 
the Maricopa County portion of Arizona’s infrastructure SIP. 
9.
List of all previous notices posted to the Maricopa County EROP website addressing
the proposed rule and a concise explanatory statement, as prescribed by A.R.S. § 49-
471.07(B):
(a) List of all previous notices posted to the Maricopa County EROP website 
addressing the proposed rule: 
Briefing Notification to County Manager:  
 
July 22, 2024 
Notice of Expedited Rulemaking:  
 
 
July 24, 2024 
(b) The following discussion addresses each of the elements required for a 
concise explanatory statement, as prescribed by A.R.S. § 49-471.07(B): 
No changes to the rule were made after the Notice of Expedited Rulemaking was 
posted on July 24, 2024. MCAQD did not receive any written comments from 
stakeholders. 
Exact Wording of the Rule 
MARICOPA COUNTY AIR POLLUTION CONTROL REGULATIONS 
REGULATION V – AIR QUALITY STANDARDS AND AREA 
CLASSIFICATION 
RULE 510 (AIR QUALITY STANDARDS) 
INDEX 
SECTION 100 – GENERAL 
101 
PURPOSE 
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Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
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102 
AVAILABILITY OF INFORMATION 
SECTION 200 – DEFINITIONS 
201 
PRIMARY AMBIENT AIR QUALITY STANDARDS 
202 
SECONDARY AMBIENT AIR QUALITY STANDARDS 
SECTION 300 – STANDARDS 
301 
PARTICULATE MATTER - 2.5 MICRONS OR LESS (PM2.5) 
302 
PARTICULATE MATTER - 10 MICRONS OR LESS (PM10) 
303 
SULFUR OXIDES (SULFUR DIOXIDE) 
304 
OZONE 
305 
CARBON MONOXIDE 
306 
NITROGEN OXIDES (NITROGEN DIOXIDE) 
307 
LEAD 
308 
POLLUTANT CONCENTRATION DETERMINATIONS 
309 
ADDITIONAL REQUIREMENTS 
310 
INCORPORATIONS BY REFERENCE 
SECTION 400 – ADMINISTRATIVE REQUIREMENTS 
401 
REPORTING OF AMBIENT AIR QUALITY MONITORING DATA 
SECTION 500 – MONITORING AND RECORDS (NOT APPLICABLE)

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
page 10 of 15 
Revised 07/13/1988; Revised 11/01/2006; Revised 02/03/2016; Revised 12/11/2019; and 
Revised MM/DD/YYYY 
MARICOPA COUNTY AIR POLLUTION CONTROL REGULATIONS 
REGULATION V – AIR QUALITY STANDARDS AND AREA 
CLASSIFICATION 
RULE 510 (AIR QUALITY STANDARDS) 
SECTION 100 – GENERAL 
101 
PURPOSE: To establish ambient air quality standards which are necessary to protect 
human health and public welfare. 
102 
AVAILABILITY OF INFORMATION: Copies of materials referenced in Sections 310, 
401.1, and 401.2 of this rule are available electronically at www.ecfr.gov; or at the 
Maricopa County Air Quality Department. 
SECTION 200 – DEFINITIONS: For the purpose of this rule, the following definitions 
shall apply, in addition to those definitions found in Rule 100 (General Provisions and 
Definitions) of these rules. In the event of any inconsistency between any of the Maricopa 
County Air Pollution Control rules, the definitions in this rule take precedence.   
201 
PRIMARY AMBIENT AIR QUALITY STANDARDS: The ambient air quality standards 
which define levels of air quality necessary, with an adequate margin of safety, to 
protect the public health, as determined by the Arizona Department of Environmental 
Quality and United States Environmental Protection Agency, and specified in this rule. 
202 
SECONDARY AMBIENT AIR QUALITY STANDARDS: The ambient air quality standards 
which define levels of air quality necessary to protect the public welfare from any known 
or anticipated adverse effects of a pollutant, as determined by the Arizona Department 
of Environmental Quality and United States Environmental Protection Agency, and 
specified in this rule. 
SECTION 300 – STANDARDS: The following are established as the primary and 
secondary ambient air quality standards for Maricopa County:   
301 
PARTICULATE MATTER - 2.5 MICRONS OR LESS (PM2.5): 
301.1 Primary Ambient Air Quality Standards for PM2.5: The primary ambient air 
quality standards for PM2.5 shall be 12.0 9.0 micrograms per cubic meter (µg/m3) 
annual arithmetic mean concentration and 35 µg/m3 24-hour average 
concentration. The primary annual PM2.5 standard shall be considered attained 
when the annual arithmetic mean concentration, as determined in accordance

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
page 11 of 15 
with 40 CFR 50, Appendix N, is less than or equal to 12.0 9.0 µg/m3. The primary 
24-hour PM2.5 standard shall be considered attained when the 98th percentile 24-
hour concentration, as determined in accordance with 40 CFR 50, Appendix N, is 
less than or equal to 35 µg/m3. 
301.2 Secondary Ambient Air Quality Standards for PM2.5: The secondary ambient air 
quality standard for PM2.5 shall be 15.0 µg/m3 annual arithmetic mean 
concentration and 35 µg/m3 24-hour average concentration. The secondary 
annual standard shall be considered attained when the annual arithmetic mean 
concentration, as determined in accordance with 40 CFR 50, Appendix N, is less 
than or equal to 15.0 µg/m3. The secondary 24-hour PM2.5 standard shall be 
considered attained when the 98th percentile 24-hour concentration, as 
determined in accordance with 40 CFR 50, Appendix N, is less than or equal to 35 
µg/m3. 
302 
PARTICULATE MATTER - 10 MICRONS OR LESS (PM10): Primary and Secondary 
Ambient Air Quality Standard for PM10: The primary and secondary ambient air quality 
standards for PM10 shall be 150 µg/m3 24-hour average concentration. The standards 
shall be considered attained when the expected number of days per calendar year with 
a 24-hour average concentration above 150 µg/m3, as determined in accordance with 
40 CFR 50, Appendix K, is less than or equal to one. 
303 
SULFUR OXIDES (SULFUR DIOXIDE): 
303.1 Primary Ambient Air Quality Standards for Sulfur Oxides: The primary ambient 
air quality standard for sulfur oxides (measured as sulfur dioxide) shall be 75 
parts per billion (ppb) 1-hour average concentration. The standard shall be 
considered attained when the three-year average of the annual 99th percentile of 
the daily maximum 1-hour average concentrations is less than or equal to 75 ppb, 
as determined in accordance with 40 CFR 50, Appendix T. 
303.2 Secondary Ambient Air Quality Standard for Sulfur Oxides: The secondary 
ambient air quality standard for sulfur oxides (measured as sulfur dioxide) shall 
be 0.5 ppm (1300 g/m3) 3-hour average. The standard shall be considered 
attained when the second-highest valid 3-hour average concentration, as 
determined in accordance with 40 CFR 50.5, is less than 0.5 ppm. 
304 
OZONE: Primary and Secondary Ambient Air Quality Standards for Ozone Eight-hour 
Average Concentration: The primary and secondary ambient air quality standards for 
ozone shall be 0.070 ppm, daily maximum 8-hour average. The standards shall be 
considered attained at an ambient air quality monitoring site when the three-year 
average of the annual fourth-highest daily maximum eight-hour average ozone 
concentration, as determined in accordance with 40 CFR 50, Appendix U, is less than or 
equal to 0.070 ppm. 
305 
CARBON MONOXIDE:

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
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305.1 Primary Ambient Air Quality Standards for Carbon Monoxide: The primary 
ambient air quality standards for carbon monoxide shall be: 
a. One-hour Average Concentration: 35 ppm (40 mg/m3). This maximum one-
hour average concentration, as determined in accordance with 40 CFR 50.8, 
shall not be exceeded more than once per year at any one location. 
b. Eight-hour Average Concentration: 9 ppm (10 mg/m3). This maximum eight-
hour average concentration, as determined in accordance with 40 CFR 50.8, 
shall not be exceeded more than once per year at any one location. 
306 
NITROGEN OXIDES (NITROGEN DIOXIDE): 
306.1 Primary Ambient Air Quality Standards for Nitrogen Oxides: The primary 
ambient air quality standards for oxides of nitrogen, measured in the ambient air 
as nitrogen dioxide, are: 
a. Annual Average Concentration: 53 ppb. The annual primary standard is met 
when the annual average concentration in a calendar year is less than or 
equal to 53 ppb, as determined in accordance with 40 CFR 50, Appendix S. 
b. One Hour Average Concentration: 100 ppb. The one-hour primary standard is 
met when the three-year average of the annual 98th percentile of the daily 
maximum one-hour average concentration is less than or equal to 100 ppb, as 
determined in accordance with 40 CFR 50, Appendix S. 
306.2 Secondary Ambient Air Quality Standards for Nitrogen Oxides: The secondary 
ambient air quality standard for oxides of nitrogen, measured as nitrogen dioxide, 
is 0.053 parts per million (ppm) (100 µg/m3), annual arithmetic mean. The 
standard shall be considered attained when the annual arithmetic mean 
concentration in a calendar year, as determined in accordance with 40 CFR 
50.11, is less than or equal to 0.053 ppm 
307 
LEAD: Primary and Secondary Ambient Air Quality Standards for Lead: The primary 
and secondary ambient air quality standards for lead and its compounds shall be 0.15 
µg/m3. The standards shall be considered attained when the maximum arithmetic three-
month mean concentration for a 3-year period, as determined in accordance with 40 
CFR 50, Appendix R, is less than or equal to 0.15 µg/m3. 
308 
POLLUTANT CONCENTRATION DETERMINATIONS: Pollutant concentrations shall be 
measured by the following methods: 
308.1 Reference Methods: 
a. The concentration of PM2.5 in the ambient air shall be measured by a 
reference method based on 40 CFR 50, Appendix L. 
b. The concentration of PM10 in the ambient air shall be measured by a 
reference method based on 40 CFR 50, Appendix J.

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
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c. The concentration of sulfur oxides (measured as sulfur dioxide) in the 
ambient air shall be measured by a reference method based on 40 CFR 50, 
Appendix A-1 or A-2. 
d. The concentration of ozone in the ambient air shall be measured in 
accordance with 40 CFR 50, Appendix D. 
e. The concentration of carbon monoxide in the ambient air shall be measured 
in accordance with 40 CFR 50, Appendix C. 
f. The concentration of nitrogen dioxide in the ambient air shall be measured in 
accordance with 40 CFR 50, Appendix F. 
g. The concentration of lead in the ambient air shall be measured in accordance 
with 40 CFR 50, Appendix G. 
308.2 Equivalent Methods and Approved Regional Methods: Pollutant concentrations 
may also be measured by: 
a. An equivalent method designated by the Administrator in accordance with 40 
CFR 53; or 
b. An approved regional method of measurement that, though not designated as 
a reference or equivalent method, has been approved for use by the 
Administrator acting pursuant to 40 CFR 58, Appendix C. Such method shall 
be subject to any restrictions placed on its use by the Administrator. 
308.3 Method Withdrawal: The cancellation or supersession of designation of a 
reference or equivalent method by the Administrator acting pursuant to 40 CFR 
53.11 or 53.16 shall also amount to a withdrawal of the authorization for use of 
that method for purposes of this rule. 
309 
ADDITIONAL REQUIREMENTS: 
309.1 Quality assurance, monitor siting, and sample probe installation procedures shall 
be in accordance with the procedures described in the Appendices to 40 CFR 58. 
309.2 Unless otherwise specified, interpretation of all ambient air quality standards 
contained in this rule shall be in accordance with 40 CFR 50. 
309.3 The evaluation of air quality data in terms of procedure, methodology, and 
concept is to be consistent with methods described in 40 CFR 50. 
310 
INCORPORATIONS BY REFERENCE: The CFR references listed below are incorporated 
by reference in Appendix G of these rules: 
310.1 40 CFR 50 – National Primary and Secondary Ambient Air Quality Standards; 
310.2 40 CFR 53 – Ambient Air Monitoring Reference and Equivalent Methods; and

Maricopa County • Air Quality Department • Planning and Analysis Division • November 2024 
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310.3 40 CFR 58 – Ambient Air Quality Surveillance. 
SECTION 400 – ADMINISTRATIVE REQUIREMENTS 
401 
REPORTING OF AMBIENT AIR QUALITY MONITORING DATA: 
401.1 Annual Air Quality Monitoring Network Plan: The Control Officer shall submit to 
the Administrator an annual monitoring network plan that at a minimum meets 
the requirements of 40 CFR 58.10. The annual report will be made available to 
the public at the Maricopa County Air Quality Department at least 30 days prior to 
submission to the Administrator. 
401.2 Daily Air Quality Index (AQI) Report: The Control Officer shall report to the public 
on a daily basis an AQI that at a minimum meets the requirements of 40 CFR 
58.50 and 40 CFR 58, Appendix G. The AQI will also be made available to the 
public at the Maricopa County Air Quality Department. 
SECTION 500 – MONITORING AND RECORDS (NOT APPLICABLE)

Maricopa County 
Air Quality Department 
Planning and Analysis Division 
Maricopa.gov/AQ