United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued October 21, 2014 Decided June 2, 2015

No. 12-1309

MISSISSIPPI COMMISSION ON ENVIRONMENTAL QUALITY,

PETITIONER

v.

ENVIRONMENTAL PROTECTION AGENCY AND GINA 

MCCARTHY,

RESPONDENTS

STATE OF CONNECTICUT, ET AL.,

INTERVENORS

Consolidated with 12-1310, 12-1312, 12-1313, 12-1315, 

12-1316, 12-1317, 12-1318, 12-1322, 12-1323, 12-1326, 

12-1328, 13-1030, 13-1032, 13-1046, 13-1050, 13-1051, 

13-1052, 13-1053, 13-1054

On Petitions for Review of Final Action of the 

United States Environmental Protection Agency

Valerie Satterfield Edge, Deputy Attorney General, Office 

of the Attorney General for the State of Delaware, argued the 

cause for the petitioners Delaware Department of Natural 

Resources and Environmental Control and the State of 

Connecticut. George Jepsen, Attorney General, and Kimberly 
2

P. Massicotte and Scott N. Koschwitz, Assistant Attorneys 

General, were with her on brief.

Robin L. Cooley and Robert Ukeiley argued the causes and 

filed the joint briefs for Environmental Petitioners. James J. 

Tutchton entered an appearance.

Donna J. Hodges and Reed D. Rubinstein argued the 

causes for State and County Petitioners. Gary C. Rikard and 

Mark L. Walters, Assistant Attorneys General, Office of the 

Attorney General for the State of Texas, were with them on the 

joint brief. Gregory W. Abbott, Attorney General, Office of the 

Attorney General for the State of Texas, and Jonathan K. 

Niermann, Assistant Attorney General, and Mary Ann Poirier

entered appearances. 

Timothy J. Junk, Deputy Attorney General, Office of the 

Attorney General for the State of Indiana, argued the cause for 

the petitioner State of Indiana. Gregory F. Zoeller, Attorney 

General, was with him on brief. 

Roger R. Martella Jr. argued the cause for the Industrial 

Petitioners. Timothy K. Webster, Ryan C. Morris, David C. 

Duggins, Matt Paulson, Howard Rubin, Glen Donath, 

Christopher D. Jackson, William L. Wehrum and Aaron M. 

Flynn were with him on brief.

Elizabeth B. Dawson and Jessica O’Donnell, Attorneys, 

United States Department of Justice, argued the causes for the 

respondent. Robert G. Dreher, Acting Assistant Attorney 

General, and Jan Tierney, Attorney, United States

Environmental Protection Agency, were with them on brief.
3

Sean D. Reyes, Attorney General, Office of the Attorney 

General for the State of Utah, Bridget Romano, Utah Solicitor 

General, Connie S. Nakahara, Assistant Utah Attorney 

General, Constance E. Brooks, David G. Scott and Bret A. 

Sumner were on the joint brief for the respondent-intervenors 

State of Utah, et al. Mark L. Shurtleff, former Attorney 

General, Office of the Attorney General for the State of Utah,

entered an appearance.

Tómas Carbonell and Peter Zalzal were on brief for the 

respondent-intervenor Environmental Defense Fund. Vickie 

L. Patton entered an appearance.

Before: GARLAND, Chief Judge, and HENDERSON and 

SRINIVASAN, Circuit Judges.

Opinion for the Court filed PER CURIAM.

PER CURIAM: The Congress enacted the Clean Air Act 

(the Act), 42 U.S.C. §§ 7401 et seq., “to protect and enhance 

the quality of the Nation’s air resources so as to promote the 

public health and welfare and the productive capacity of its 

population.” Id. § 7401(b)(1). At issue in this case is Title I 

of the Act, which requires the Environmental Protection 

Agency (EPA) to promulgate National Ambient Air Quality 

Standards (NAAQS), thus setting the maximum level of 

permissible pollutant concentration in the atmosphere. See id. 

§§ 7408(a)(1), 7409(a)–(b). After the EPA sets the NAAQS, 

it must determine whether each state is in compliance with 

these air-quality standards and, in the event of a NAAQS 

violation, how to establish the geographic boundaries around

the non-compliant area. See id. § 7407(d)(1).

In these consolidated petitions, several states, counties, 

industrial entities and environmental organizations challenge 
4

the EPA’s determination that certain geographic areas are, or 

are not, in “attainment” with the EPA’s ground-level ozone 

NAAQS. Id. Some argue that the Act, as applied to them, 

violates various Constitutional provisions; others argue that the 

EPA misconstrued the terms of the Act. Virtually every 

petitioner argues that, for one reason or another, the EPA acted 

arbitrarily and capriciously in making its final NAAQS 

designations. But because the EPA complied with the 

Constitution, reasonably interpreted the Act’s critical terms 

and wholly satisfied—indeed, in most instances, 

surpassed—its obligation to engage in reasoned 

decision-making, we deny the consolidated petitions for 

review in their entirety. 

I. BACKGROUND

The EPA began the odyssey resulting in these 

consolidated petitions nearly seven years ago. Along the way, 

it construed a variety of the Act’s provisions, promulgated 

regulations and issued informal guidance to assist in the 

collaborative area-designation effort between it and the states. 

Before discussing the substance of the issues, a brief overview 

of the Act and the underlying proceedings in this case is in 

order.

A. THE CLEAN AIR ACT

Under the Act, the EPA must promulgate NAAQS, which 

set the maximum ambient, or outdoor, air concentrations for 

six pollutants that “may reasonably be anticipated to endanger 

public health or welfare.” 42 U.S.C. § 7408(a)(1). Once it 

establishes a NAAQS, the EPA must designate each “area” in 

the United States as “attainment” or “nonattainment.” See id. 

§ 7407(d)(1)(A)(i)–(ii). Alternatively, the EPA may 

designate an area as “unclassifiable” if the area “permit[s] no 

determination given existing data.” Catawba Cnty., N.C. v. 
5

EPA, 571 F.3d 20, 26 (D.C. Cir. 2009) (citing 42 U.S.C. 

§ 7407(d)(1)(A)(i)–(iii)). The EPA treats an “unclassifiable” 

area as if it were in attainment. See 42 U.S.C. § 7471. 

Generally speaking, the EPA designates an area that meets 

the relevant NAAQS as in attainment, while areas that exceed 

the NAAQS receive a nonattainment designation. See 

Catawba Cnty., 571 F.3d at 26. But even if an area’s ambient 

air concentration complies with the relevant NAAQS, the EPA 

nonetheless designates it as nonattainment if it “contributes” to 

a NAAQS violation in a “nearby area.” See 42 U.S.C. 

§ 7407(d)(1)(A)(i). The Act does not define the terms 

“contributes,” “nearby” or “area.” 

The EPA works collaboratively with the states to 

determine the NAAQS-attainment status for all areas within a 

respective state’s borders. No later than one year after the 

EPA promulgates a new or revised NAAQS, each state must 

submit recommended “initial designations” to the EPA. Id.

§ 7407(d)(1)(A). A state’s initial designations must suggest 

both the appropriate geographic boundaries for each “area” and 

whether the EPA should classify the suggested area as 

attainment, nonattainment or unclassifiable. See id. 

§ 7407(d)(1)(A)–(B).

Once it receives a state’s initial designations, the EPA 

may either promulgate them as submitted or modify them as it 

“deems necessary.” Id. § 7407(d)(1)(B)(ii). The Act gives 

the EPA discretion to change a state’s recommended 

designation, to alter a state’s proposed geographic area or both. 

See id. Although the EPA “has no obligation to give any 

quantum of deference to a designation that it ‘deems 

necessary’ to change,” Catawba Cnty., 571 F.3d at 40, it must 

nonetheless notify the state of any intended change and provide 

the state with at least 120 days “to demonstrate why any 
6

proposed modification is inappropriate,” 42 U.S.C. 

§ 7407(d)(1)(B)(ii). These notifications are known as 

“120-day letters.” See Air Quality Designations for the 2008 

Ozone National Ambient Air Quality Standards, 77 Fed. Reg. 

30,088, 30,090 (May 21, 2012) [hereinafter 2008 Designations 

Rule].

While the EPA has ultimate authority to determine each 

area’s attainment status, each state has “primary 

responsibility” for ensuring that the geographic areas within its 

borders either maintain attainment or progress towards it. 42 

U.S.C. § 7407(a). Accordingly, once the EPA finalizes its 

designations, each state must submit to the EPA a State 

Implementation Plan (SIP) specifying how the NAAQS “will 

be achieved and maintained.” Id. For areas in attainment, 

the SIP must simply “contain emission limitations and such 

other measures as may be necessary . . . to prevent significant 

deterioration of air quality.” Id. § 7471. 

For a nonattainment area, however, the Act imposes more 

stringent requirements. A SIP from a state with a 

nonattainment area must demonstrate that the state intends to 

implement “all reasonably available control measures” and 

“reasonably available control technology” to bring the area 

into attainment. Id. § 7502(c)(1). The Act also imposes 

deadlines, or “attainment dates,” on an offending area. See id. 

§ 7502(a)(2)(A). For a violation of a primary1 NAAQS, the 

offending state must reach attainment “as expeditiously as 

practicable, but no later than 5 years from the date such area 

was designated nonattainment.” Id. The EPA “may extend 

the attainment date to the extent [it] determines appropriate” 

but only “for a period no greater than 10 years from the date of 

designation as nonattainment.” Id. Taken together, these 

 1 See infra n.2. 
7

two requirements often mean that a state with a nonattainment 

area must implement potentially expensive technology or 

expensive process changes to reduce pollution levels over a 

relatively short period of time. If a state fails to reach 

attainment timely and the failure is due to inadequate 

implementation efforts, sanctions can be imposed, including 

loss of federal highway funds and increasingly severe 

restrictions on emissions sources within the state. See id. 

§ 7509(a)–(b). 

B. THE 2008 OZONE NAAQS AND THE EPA’S 

2008 GUIDANCE

On March 12, 2008, the EPA promulgated new primary 

and secondary NAAQS for ambient ozone,2 a component of 

urban smog. See 2008 Designations Rule, 77 Fed. Reg. at 

30,089. Even though ozone is an “essential presence in the 

atmosphere’s stratospheric layer,” it becomes harmful at 

ground level and “can cause lung dysfunction, coughing, 

wheezing, shortness of breath, nausea, respiratory infection, 

and in some cases, permanent scarring of the lung tissue.” 

S. Coast Air Quality Mgmt. Dist. v. EPA, 472 F.3d 882, 887 

(D.C. Cir. 2006) (quoting Henry A. Waxman, An Overview of

the Clean Air Act Amendments of 1990, 21 ENVTL. L. 1721, 

1758 (1991)). It also “has a broad array of effects on trees, 

 2 “Primary” NAAQS exist to protect the “public health,” 40 

C.F.R. § 50.2(b), and they ensure the safety of “sensitive” 

populations such as asthmatics, children and the elderly. See

National Ambient Air Quality Standards (NAAQS), EPA, 

http://www.epa.gov/air/criteria.html (last updated Oct. 21, 2014). 

“Secondary” NAAQS exist to protect the “public welfare,” 40 

C.F.R. § 50.2(b), and they prevent harms like decreased visibility 

and damage to animals, crops, vegetation and buildings. See

National Ambient Air Quality Standards (NAAQS), EPA, 

http://www.epa.gov/air/criteria.html (last updated Oct. 21, 2014). 
8

vegetation, and crops and can indirectly affect other ecosystem 

components such as soil, water, and wildlife.” Mississippi v. 

EPA, 744 F.3d 1334, 1340 (D.C. Cir. 2013). Because ozone 

forms at ground level when “ozone precursors”—specifically, 

nitrous oxides (NOx) and volatile organic compounds 

(VOCs)—react with sunlight, NAAQS compliance largely 

depends on reducing emissions from ozone-precursor 

producers like power plants, industrial compounds, motor 

vehicles and combustion engines. See 2008 Designations 

Rule, 77 Fed. Reg. at 30,089. Complicating this task is that 

ozone and ozone precursors travel easily through the 

atmosphere, which can result in NAAQS violations hundreds 

of miles away from the source of the ozone precursors. See id. 

Both the EPA’s 2008 primary and secondary ozone 

NAAQS reduced the maximum allowable daily average 

eight-hour level of ozone from 0.08 parts per million (ppm) to 

0.075 ppm. See National Ambient Air Quality Standards for 

Ozone, 73 Fed. Reg. 16,436, 16,436–37 (Mar. 27, 2008). By 

setting these new NAAQS, the EPA triggered the states’ 

responsibility to submit their initial designations. See 42 

U.S.C. § 7407(d)(1)(A). To assist this process, the EPA 

issued a guidance titled “Area Designations for the 2008 

Revised Ozone National Ambient Air Quality Standards” 

[hereinafter 2008 Guidance] on December 4, 2008, which 

included several matters relevant to the instant petitions. 

First, the 2008 Guidance instructed states on the quality of 

data it expected them to consider. Specifically, it 

recommended that the states “identify violating areas using the 

most recent three consecutive years of quality-assured, 

certified air quality data.” 2008 Guidance at 2. The 2008 

Guidance also informed the states that “[i]n general, [NAAQS] 

violations [will be] identified using data from . . . monitors that 
9

are sited and operated in accordance with [EPA regulations 

located at] 40 C.F.R. Part 58.” Id. 

Second, the 2008 Guidance provided instruction for 

establishing geographic boundaries around nonattainment 

areas, noting first that the “EPA believes it is important to 

examine ozone-contributing emissions across a relatively 

broad geographic area.” 2008 Guidance at 3. Accordingly, 

the 2008 Guidance recommended that if an air-quality monitor 

reports a NAAQS violation, the state should consider using the 

Core Based Statistical Area (CBSA) or Combined Statistical 

Area (CSA) in which the monitor is located as the 

“presumptive” boundary.3 Id. If the violating monitor is not 

in a CSA or CBSA, the 2008 Guidance recommended using the 

county in which the violating monitor is located as the 

presumptive boundary. Id. 

 3 A CBSA is defined by the Office of Management and Budget 

(OMB) as:

[A] statistical geographic entity consisting of the 

county or counties associated with at least one core 

(urbanized area or urban cluster) of at least 10,000 

population, plus adjacent counties having a high 

degree of social and economic integration with the 

core as measured through commuting ties with the 

counties containing the core.

See Standards for Defining Metropolitan and Micropolitan

Statistical Areas, 65 Fed. Reg. 82,228, 82,238 (Dec. 27, 2000). A 

CSA is formed by two or more adjacent CBSAs if there is sufficient 

“employment interchange” between them. Id. In other words, 

CSAs and CBSAs are both roughly equivalent to a “metropolitan” 

area. See generally id. at 82,235–36. Throughout this opinion, we 

use the term “metropolitan area” to refer to the CSA or CBSA, as 

defined in the 2008 Guidance. See 2008 Guidance at 3 & n.2. 
10

The 2008 Guidance made plain, however, that CSAs, 

CBSAs and county lines were merely presumptive boundaries, 

recognizing that “area-specific analyses . . . may support 

nonattainment area boundaries that are larger or smaller than 

the presumptive area starting point.” Id. Stressing that “each 

potential nonattainment area should be evaluated on a 

case-by-case basis,” the 2008 Guidance instructed the states to 

consider nine factors when determining a nonattainment area’s 

borders. See id. at 2, Attach. 2. These include (1) air-quality 

data; (2) emissions data (such as location of emissions sources 

and contribution to ozone concentrations); (3) population 

density and degree of urbanization (including commercial 

development); (4) traffic and commuting patterns; 

(5) population growth rates and patterns; (6) meteorology 

(such as weather and air-transport patterns); (7) geography and 

topography (such as mountain ranges or other air-basin 

boundaries that could affect ozone dispersion); 

(8) jurisdictional boundaries (such as counties, air districts, 

existing nonattainment area boundaries and regional planning 

authority boundaries) and (9) the level of control of emissions 

sources. See id. Attach. 2. The 2008 Guidance stated that the 

EPA planned to consider these same factors, “along with any 

other relevant information,” in determining whether to modify 

the states’ initial designations. Id. 

C. THE 2008 OZONE DESIGNATION PROCESS

By 2009, all states had submitted their initial designations 

to the EPA. Rather than immediately reviewing the initial 

designations, however, the EPA halted the designation process 

to consider whether to lower the ozone NAAQS even further. 

This delay prompted a lawsuit by WildEarth Guardians—an 

environmental-group petitioner in this case—that sought to 

compel the EPA to complete the stalled ozone NAAQS 
11

designation process. 4 The EPA and WildEarth Guardians 

eventually entered into a consent decree that required the EPA 

to finalize its designations no later than May 31, 2012. See

2008 Designations Rule, 77 Fed. Reg. at 30,091. 

The EPA notified the states in September 2011 that it 

intended to finalize the ozone NAAQS designations by the 

May 31, 2012 deadline set forth in the consent decree. In 

accordance with the 2008 Guidance’s instruction to “identify 

violating areas using the most recent three consecutive years of 

quality-assured, certified air quality data,” 2008 Guidance at 2, 

virtually every state had already submitted air-quality data 

from 2008 to 2010 by the time the EPA resumed the 

designation process. Although the EPA assured the states that 

it still planned to consider the recommended designations and 

ozone data they had submitted initially, it recognized that some 

states may have collected more recent air-quality data for their 

regions. For this reason, the EPA allowed the states to 

provide updated recommendations and analyses—so long as 

any updated air-quality data was certified for quality—but 

assured them that they were under no obligation to do so. In 

response to this invitation, several states updated their initial 

designations and some submitted air-quality data from 2009 to 

2011 to replace their older 2008 to 2010 data. The states 

seeking to use data from 2009 to 2011 agreed to certify their 

data for quality by February 29, 2012, so that the EPA had 

sufficient time to consider the more recent data in advance of 

its May 31, 2012 deadline to finalize the designations. 

The EPA then reviewed each state’s initial designations to 

determine whether to modify them. It first examined the 

air-quality submissions from the states to determine which 

 4 See WildEarth Guardians, et al. v. Jackson, 

No. 2:11-CV-01661 (D. Ariz. filed Aug. 24, 2011).
12

monitors reported ozone NAAQS violations. If a state 

certified its air-quality data from 2011 by the February 29, 

2012 deadline, the EPA generally considered its air-quality 

data from the years 2009 to 2011. For all other states, the 

EPA considered air-quality data from 2008 to 2010. 

After identifying NAAQS-violating monitors, the EPA 

decided whether to alter the states’ respective recommended 

nonattainment boundaries. To do so, the EPA used a 

multi-factor, weight-of-the-evidence test that tracked—but 

was not identical to—the nine-factor test in the 2008 Guidance. 

Specifically, the EPA collapsed the 2008 Guidance’s 

nine-factor test into a five-factor test, which examined (1) “Air 

Quality Data,” or whether an area’s monitor reported a 

NAAQS violation; (2) “Emissions Data,” including emissions 

levels and controls, population, population density, population 

growth, degree of urbanization and traffic and commuting 

patterns; (3) “Meteorology,” including wind speed and 

direction; (4) “Geography/Topography,” which examined the 

effect of physical land features on the distribution of ozone and 

(5) “Jurisdictional Boundaries,” which helped determine 

whether certain areas could effectively carry out air-quality 

planning and enforcement functions for nonattainment areas. 

Once attainment designations were made, the EPA 

notified the states of any proposed modifications it deemed 

necessary and invited them to submit any additional data or 

comments they wished to have the EPA consider. Although 

not required by statute, see 42 U.S.C. § 7407(d)(2)(B), the 

EPA also opened a 30-day public comment period on the 

proposed notifications. Several states, organizations and 

members of the public—including many of the petitioners in 

this case—submitted comments. The EPA considered the 

comments and then promulgated its final designations, which 

identified 48 nonattainment areas in 26 states, the District of 
13

Columbia and Indian country. The nonattainment areas 

included 192 counties in toto and 36 counties in part. The 

EPA published the majority of its final designations on May 

21, 2012, see 2008 Designations Rule, 77 Fed. Reg. at 30,088, 

and in the case of certain Chicago-area designations, on June 

11, 2012, see Air Quality Designations for the 2008 Ozone 

National Ambient Air Quality Standards for Several Counties 

in Illinois, Indiana, and Wisconsin; Corrections to Inadvertent 

Errors in Prior Designations, 77 Fed. Reg. 34,221, 34,221

(June 11, 2012). 

After the EPA received and denied 29 petitions for 

reconsideration, the parties in this consolidated case 5

petitioned this Court for review. We have jurisdiction under 

42 U.S.C. § 7607(b)(1). 

 5 See Del. Dep’t of Natural Res. & Envtl. Control v. EPA, 

No. 12-1310 (D.C. Cir.); Tex. Pipeline Ass’n v. EPA, No. 12-1312 

(D.C. Cir.); Wise Cnty., Tex. v. EPA, No. 12-1313 (D.C. Cir.); 

Indiana v. EPA, No. 12-1315 (D.C. Cir.); Texas v. EPA, 

No. 12-1316 (D.C. Cir.); Sierra Club v. EPA, No. 12-1317 (D.C. 

Cir.); Gas Processors Ass’n v. EPA, No. 12-1318 (D.C. Cir.); Devon 

Energy Corp. v. EPA, No. 12-1322 (D.C. Cir.); Targa Resources 

Corp. v. EPA, No. 12-1323 (D.C. Cir.); WildEarth Guardians v. 

EPA, No. 12-1326 (D.C. Cir.); DeSoto Cnty., Miss. v. EPA, 

No. 12-1328 (D.C. Cir.); Sierra Club v. EPA, No. 13-1030 (D.C. 

Cir.); WildEarth Guardians v. EPA, No. 13-1032 (D.C. Cir.); Wise 

Cnty., Tex. v. EPA, No. 13-1046 (D.C. Cir.); Devon Energy Corp. v. 

EPA, No. 13-1050 (D.C. Cir.); Tex. Pipeline Ass’n v. EPA, 

No. 13-1051 (D.C. Cir.); Gas Processors Ass’n v. EPA, No. 13-1052 

(D.C. Cir.); Texas v. EPA, No. 13-1053 (D.C. Cir.); Targa Res. 

Corp. v. EPA, No. 10-1054 (D.C. Cir.).
14

II. COMMON LEGAL PRINCIPLES

Before addressing the petitioners’ individual challenges, 

we think it helpful to discuss several principles that bear on 

most, if not all, of the issues the petitioners have raised.

First, we review the EPA’s NAAQS designations under 

the same standard we use in reviewing a challenge brought 

under the Administrative Procedure Act (APA). See Allied 

Local & Reg’l Mfrs. Caucus v. EPA, 215 F.3d 61, 68 (D.C. Cir. 

2000). Accordingly, we will set aside a NAAQS designation 

by the EPA only if it is “arbitrary, capricious, an abuse of 

discretion, or otherwise not in accordance with law.” 

Catawba Cnty., 571 F.3d at 41 (quoting 5 U.S.C. § 706(2)(A)). 

We must, however, give an “extreme degree of deference” to 

the EPA’s evaluation of “scientific data within its technical 

expertise,” City of Waukesha v. EPA, 320 F.3d 228, 247 (D.C. 

Cir. 2003), especially where, as here, we review the “EPA’s 

administration of the complicated provisions of the Clean Air 

Act.” Catawba Cnty., 571 F.3d at 41 (citing Nat’l Ass’n of 

Clean Air Agencies v. EPA, 489 F.3d 1221, 1229 (D.C. Cir. 

2007)). Because the EPA’s “basic obligation” is to conduct 

“reasoned decisionmaking,” id. at 25, we will uphold its action 

if the record shows that the EPA “considered all relevant 

factors and articulated a ‘rational connection between the facts 

found and the choice made,’ ” id. at 41 (quoting Burlington 

Truck Lines, Inc. v. United States, 371 U.S. 156, 168 (1962)).

Second, we have long since rejected the argument that the 

EPA violates the Act if it uses a holistic, multi-factor, 

weight-of-the-evidence test for determining whether a given 

area contributes to a NAAQS violation. See ATK Launch 

Sys., Inc. v. EPA, 669 F.3d 330, 336–37 (D.C. Cir. 2012) 

(challenge to 2006 fine particulate matter NAAQS 

designations); Catawba Cnty., 571 F.3d at 46 (challenge to 
15

1997 fine particulate matter NAAQS designations). Indeed, 

in Catawba County, we made explicit that the EPA does not 

violate the Act even if it fails to adopt “a bright-line, 

‘objective’ test” for determining contribution and we also held 

that the “EPA’s failure to quantify its analysis” does not render 

“its interpretation of ‘contribute’ arbitrary and capricious and 

therefore unreasonable.” 571 F.3d at 39. Rather, because 

“[a]n agency is free to adopt a totality-of-the-circumstances 

test to implement a statute that confers broad discretionary 

authority, even if that test lacks a definite ‘threshold’ or ‘clear 

line of demarcation to define an open-ended term,’ ” we have 

held that, “[t]o be reasonable, such an ‘all-things-considered 

standard’ must simply define and explain the criteria the 

agency is applying.” Id.

With this background in mind, we now turn to the 

petitioners’ challenges.

III. THE PETITIONERS’ CHALLENGES

A. DELAWARE & CONNECTICUT

We begin with a challenge to the EPA’s construction of 

the key statutory provision in this case. Petitioners Delaware 

and Connecticut challenge the EPA’s refusal to designate 

broad, multi-state nonattainment areas to address the issue of 

long-range ozone transport. According to the States, the 

EPA’s final designations are inconsistent with its statutory 

mandate to designate areas as nonattainment if they 

“contribute[] to ambient air quality in a nearby area that does 

not meet [the NAAQS].” 42 U.S.C. § 7407(d) (emphasis 

added). We conclude, to the contrary, that the designations 

are consistent with the EPA’s reasonable interpretation of the 

ambiguous statutory term “nearby.” 
16

After the EPA reopened the designation process in 2011, 

Delaware proposed a nonattainment area that would stretch 

across 16 upwind states and the District of Columbia—to states 

as far west as Missouri. Connecticut similarly proposed an 

18-state nonattainment area, also stretching west to Missouri. 

Both States argued for what Delaware described as a “more 

workable definition of ‘nearby’ ”—one that would ask 

“whether a source is ‘near enough to contribute’ to 

nonattainment or interfere with maintenance.” Letter from 

Del. Dep’t of Natural Res. & Envtl. Control to EPA 5 (Oct. 28, 

2011) [hereinafter Delaware Response]. 

The EPA, however, had taken a different approach in the 

2008 Guidance, instead interpreting “nearby” as presumptively 

including counties in the same metropolitan area as the 

violating county. 2008 Guidance at 3. In the Guidance, the 

EPA acknowledged that certain regions have ozone transport 

problems, but it concluded that the Act “does not require that 

all contributing areas be designated nonattainment, only the 

nearby areas.” Id. at 4. The agency explained that 

“[r]egional strategies, such as those employed in the Ozone 

Transport Region and EPA’s NOx SIP Call are needed to 

address the long-range transport component of ozone 

nonattainment.” Id. In keeping with this understanding of 

the statute, the EPA declined to designate “super-regional” 

nonattainment areas, see Responses to Significant Comments 

on the State and Tribal Designation Recommendations for the 

2008 Ozone NAAQS at 8–9 (Apr. 30, 2012) [hereinafter 

Response to Comments], and instead made more limited 

nonattainment designations in both Delaware and Connecticut, 

see Delaware Area Designations for the 2008 Ozone NAAQS 
17

2; Connecticut Area Designations for the 2008 Ozone NAAQS 

1.

6

We evaluate the EPA’s interpretation of a Clean Air Act 

provision under the familiar two-step Chevron framework. 

See Util. Air Regulatory Grp. v. EPA, 134 S. Ct. 2427, 2439 

(2014) (citing Chevron, U.S.A., Inc. v. Natural Res. Def. 

Council, Inc., 467 U.S. 837, 842–43 (1984)). The first 

question—“whether Congress has directly spoken to the 

precise question at issue,” Chevron, 467 U.S. at 842—has 

previously been resolved by this Court. In Pennsylvania 

Department of Environmental Protection v. EPA (PADEP), we 

held that the statutory term “nearby” in section 107(d) is 

ambiguous; indeed, we reached that conclusion in the course of 

addressing the precise argument that Delaware makes here. 

See 429 F.3d 1125, 1129–30 (D.C. Cir. 2005). In Catawba 

County, we reached the same conclusion. See 571 F.3d at 35 

(noting that section 107(d) does not define “nearby,” and that it 

is “the kind[] of word[] that suggest[s] a congressional intent to 

leave unanswered questions to an agency’s discretion and 

expertise”). 

Recognizing these precedents, Delaware and Connecticut 

conceded at oral argument that our analysis must be governed 

by Chevron’s second step, Oral Arg. Recording at 3:49–3:54, 

which requires us to ask only whether the EPA’s interpretation 

is reasonable, see, e.g., PADEP, 429 F.3d at 1130. But we 

have addressed that question once as well, also in PADEP, 

where we said that “Chevron requires that we defer to the 

agency’s reasonable interpretation of the term, and Delaware 

 6 Neither State challenges the designations of those areas as 

nonattainment, other than to contend that the designations should 

have covered much broader areas. 
18

has given us no reason to think that EPA’s interpretation is 

unreasonable.” Id. We reach the same conclusion here. 

First, the agency’s interpretation of “nearby”—as 

presumptively including counties within the same metropolitan 

area as the violating county—falls readily within the dictionary 

definition of “nearby” as “close at hand; not far off; adjacent; 

neighboring.” RANDOM HOUSE COLLEGE DICTIONARY 889 

(rev. ed. 1980). By contrast, neither the dictionary nor 

common parlance would regard Missouri as “nearby” to 

Connecticut or Delaware, as the petitioners’ proposals would 

require. 

Second, the EPA’s construction is consistent with the 

approach the agency has taken in prior designations 

proceedings—an approach that this Court has previously 

upheld as reasonable. See PADEP, 429 F.3d at 1127, 1129–

30; 2008 Guidance at 3.

Third, the EPA’s construction is consistent with the 

statutory scheme. The EPA selected the metropolitan area as 

the presumptive “nearby” area for its contribution analysis in 

part because the Congress itself chose the metropolitan area as 

the default boundary for ozone nonattainment areas classified 

as “serious,” “severe,” or “extreme.” See 42 U.S.C. 

§ 7407(d)(4)(A)(iv); 2008 Guidance at 3 n.5. The Congress’ 

choice is certainly evidence that the legislature envisioned 

broad but relatively local nonattainment areas.7

 

 7 At oral argument, the EPA made clear that it does not contend 

that its reading is the only permissible reading of the statute. Oral 

Arg. Recording at 30:01–30:59; see also 2008 Designations Rule, 77 

Fed. Reg. at 30,090 (discussing the agency’s “discretion” to interpret 

the term “nearby” in fixing the geographic scope of nonattainment 

areas).
19

As in PADEP, the petitioners argue that the EPA’s 

interpretation is unreasonable because it fails to appreciate the 

role of ozone transport, and consequently yields designations 

that fail to include the true contributors to their nonattainment 

status. See PADEP, 429 F.3d at 1129–30. Delaware notes, 

for example, that 84 to 94 per cent of its ozone results from the 

contributions of other states, including states as far west as 

Missouri. See Delaware Reply Br. 4. Without emissions 

reductions from those states, petitioners argue, they cannot 

meet the 0.075 ppm standard. Thus, by failing to address the 

principal sources of their ozone pollution, the EPA’s 

interpretation eliminates any possibility that they will attain the 

NAAQS.8

Although we are sympathetic to the petitioners’ concerns, 

our role is not to decide whether their proposed interpretation 

is reasonable. Instead, the sole question before us is whether 

the EPA interpreted the term reasonably and consistently with 

the statute. See PADEP, 429 F.3d at 1130 (noting that, 

although a broader “construction of ‘nearby’ may well be 

sensible, Chevron requires that we defer to the agency’s 

reasonable interpretation of the term”). Here, the EPA had 

already considered the problem the petitioners raised. Part of 

the rationale for using the metropolitan area as the starting 

point for the contribution analysis was to account for ozone 

transported from outside the violating county. See 2008 

 8 Delaware points to the isolated nonattainment zone of Sussex 

County as a particularly egregious example of the designations that 

the EPA’s interpretation produced. Delaware Br. 12. But even if 

over 90 per cent of Sussex County’s pollution comes from 

out-of-state sources, as Delaware asserts, the EPA found that no 

surrounding counties had the linkages necessary to justify a 

nonattainment designation under the agency’s five-factor analysis. 

See Delaware Area Designations at 37–49. 
20

Guidance at 3–4. Although this approach does not fully 

account for longer-range, interstate transport, the EPA has 

addressed that problem in regulations promulgated under other 

provisions of the Act. See, e.g., Federal Implementation 

Plans: Interstate Transport of Fine Particulate Matter and 

Ozone and Correction of SIP Approvals, 76 Fed. Reg. 48,208 

(Aug. 8, 2011) (promulgating the Cross State Air Pollution 

Rule, commonly referred to as the Transport Rule). 9

 

Although the petitioners recognize the EPA’s reliance on those 

other regulatory options, they maintain that they “have been 

less than successful” up to this point. Delaware Br. 6; see also 

id. at 9. We, however, must defer to the EPA’s reasonable 

judgment that regional strategies adopted pursuant to other 

statutory provisions specific to long-range ozone transport 

remain the appropriate means for addressing this problem. 

See 2008 Guidance at 4.

The petitioners note that our decision in PADEP rested in 

part upon the fact that there, Delaware had “offered no 

evidence that ‘in practice’ EPA will not enlarge a 

nonattainment area in response to [its then] eleven-factor 

analysis.” 429 F.3d at 1130. Indeed, in PADEP, Delaware 

had failed altogether “to produce an eleven-factor analysis.” 

Id. But we did not mean by this to suggest that, had Delaware 

produced the appropriate factor analysis, the EPA would have 

 9 The EPA promulgated the Transport Rule under 42 U.S.C. 

§ 7410(a)(2)(D), which requires SIPs to prohibit air pollution that 

will “contribute significantly to nonattainment in, or interfere with 

maintenance [of the NAAQS] by, any other State.” Other 

provisions of the Act also address interstate transport. See id. 

§ 7506a (providing for interstate transport commissions); id. § 7511c 

(establishing ozone transport region consisting of 11 states and the 

District of Columbia, which must comply with additional control 

measures). 
21

been required to adopt an interpretation of “nearby” that 

included states as far away as those within the petitioners’ 

proposed nonattainment areas. The points discussed 

above—including the dictionary definition of “nearby” and the 

consistency of the EPA’s interpretation with the statute and its 

prior practice—strongly suggest that the EPA’s narrower 

interpretation would still be reasonable. 

Nonetheless, if the petitioners had submitted a persuasive 

five-factor analysis establishing contributions from 

farther-away states, that would be relevant to our assessment of 

the reasonableness of the EPA’s refusal to enlarge the 

nonattainment area beyond its presumptive scope. In this 

case, however, although the petitioning States did submit 

technical analyses, they failed to demonstrate the requisite 

linkages under the EPA’s 2008 Guidance. See, e.g., Delaware 

Response Attach. 2 at 5–7, 11–13 (disputing relevance of 

factors related to urbanization, traffic, and economic growth); 

id. at 14–15 (with respect to meteorology factor, describing 

long-range transport without describing weather patterns 

within the proposed 16-state nonattainment area). Hence, the 

petitioners did not show that the agency “will not enlarge a 

nonattainment area in response to” the (current) five-factor 

analysis, PADEP, 429 F.3d at 1130. Rather, the States’ 

analyses were simply insufficient to overcome the agency’s 

definitional presumption.

In sum, we conclude that the EPA’s final designations of 

Delaware and Connecticut counties are consistent with a 

reasonable interpretation of the Clean Air Act.10 

 10 Delaware also argues that the EPA acted inconsistently with 

the statute by only designating as nonattainment nearby areas that 

are “contributing to a violation,” rather than those that “contribute[] 

to ambient air quality” in a violating area, 42 U.S.C. 
22

B. UINTA BASIN

Petitioner WildEarth Guardians (WildEarth) challenges 

the EPA’s designation of Uinta Basin, Utah, as 

“unclassifiable.” We find the EPA’s designation rational and 

in accordance with the Clean Air Act, and we therefore deny 

WildEarth’s petition.

1. Uinta Basin Background

The EPA requires every state to establish a network of 

regulatory monitoring stations to collect ozone air-quality data. 

See 40 C.F.R. pt. 58. The number of regulatory monitors 

required in an area depends, in part, on the area’s population. 

See id. app. D. tbl.D-2. Areas with populations below 50,000 

and many areas with fewer than 350,000 inhabitants require no 

regulatory monitors. Id. Many rural areas therefore lack 

monitors. 

Uinta Basin, Utah, had no regulatory monitoring until 

April 2011. The pre-2011 absence of regulatory-air-quality 

monitors in Uinta Basin meant that, when the EPA in 2013 

conducted the designation process for the 2008 NAAQS, the 

agency had regulatory data for Uinta Basin for only two 

years—2011 and 2012. The 2008 ozone NAAQS, however, 

reflect three-year averages of ozone levels. See 2008 

Designations Rule, 77 Fed. Reg. at 30,089. Noting that “there 

are not yet three consecutive years of certified ozone 

monitoring data available [from Uinta Basin] that can be used 

 

§ 7407(d)(1)(A)(i). Delaware Br. 12–13. As the EPA explained, 

however, its use of the phrase was simply shorthand for its 

contribution analysis; it did not represent a heightened standard. Cf. 

ATK Launch Sys., 669 F.3d at 338–39 (rejecting the argument that 

the EPA applied a dissimilar standard when it variously used the 

terms “significant contribution” and “contribution”). 
23

to determine the area’s attainment status,” id., the EPA 

designated the area as “unclassifiable,” which the Clean Air 

Act defines as an area that “cannot be classified on the basis of 

available information as meeting or not meeting” the NAAQS, 

42 U.S.C. § 7407(d)(1)(A)(iii).

Although no regulatory data exist for Uinta Basin prior to 

2011, private companies working under consent decrees have 

been required to operate ozone air-quality monitors in Uinta 

Basin since 2009. See Letter from Robin Cooley, Counsel, 

WildEarth Guardians to Lisa P. Jackson, Adm’r, EPA 3 (July 

19, 2012). Under the terms of those consent decrees, the 

private monitors must comply with many of the same 

requirements as regulatory monitors. See Consent Decree 

¶¶ 80–81, United States v. Kerr-McGee Corp., 

No. 1:07-cv-01034 (D. Colo. May 17, 2007). From 2009 to 

2011, the private monitors provided raw data showing ozone 

levels significantly exceeding the 2008 ozone NAAQS. The 

EPA found the 2009 to 2011 private data insufficient to support 

a nonattainment designation. 

2. The Private Monitoring Data Challenge

WildEarth argues that, in light of the private data, the EPA 

contravened the Act’s requirements when it designated Uinta 

Basin as unclassifiable rather than nonattainment. We 

disagree.

The Act calls for the EPA to make designations “on the 

basis of available information.” 42 U.S.C. § 7407(d)(1)(iii). 

We have repeatedly found similar language to be ambiguous 

when assessing whether to defer to an agency’s construction. 

See Catawba Cnty., 571 F.3d at 35, 38 (finding the phrase 

“based on air quality monitoring data” to be ambiguous); 

Sierra Club v. EPA, 356 F.3d 296, 305–06 (D.C. Cir. 2004) 

(finding the phrase “based on photochemical grid modeling” to 
24

be ambiguous). The EPA therefore may interpret the 

statutory language as it sees fit, as long as its interpretation is 

reasonable. Chevron, 467 U.S. at 845. And even assuming 

the Act obligates the EPA to consider certain types of data, 

there would be no obligation for the agency to base its 

designations on data it reasonably considers to be unsound, at 

least if it “adequately explain[s] its reasons for 

rejecting . . . data” on which it declines to rely. City of 

Waukesha, 320 F.3d at 248. We evaluate the EPA’s reasons 

cognizant of the “extreme degree of deference” we owe an 

agency “when it is evaluating scientific data within its 

technical expertise.” Catawba Cnty., 571 F.3d at 41. 

The EPA reasonably explained that the private monitoring 

data afforded an insufficient basis for a nonattainment 

designation because the agency was unable to perform 

post-collection quality assurance checks on the data. In 

particular, the EPA lacked quality assurance data needed to 

verify and audit the private data. As the agency explained:

Quality assurance data consist, primarily, of 

biweekly single point quality control (QC) 

checks, used to assess the precision and bias a 

given instrument is displaying in its day-to-day 

measurements, and annual independent 

performance evaluations (audits) of 

equipment, which rely on independent staff 

and measuring systems to confirm that the 

monitors are operating as expected and 

required.

Letter from Lisa P. Jackson, Adm’r, EPA to Robin Cooley, 

Counsel, WildEarth Guardians 5 (Dec. 14, 2012) (denying 

reconsideration of Uinta Basin designation). The agency 

determined that, without audits or quality control checks, it 
25

could not adequately verify the quality of the private data. 

That explanation comports with common sense and falls within 

the substantial deference accorded the EPA in evaluating the 

soundness of data available to it.

WildEarth presses several counterarguments, none of 

which we find persuasive. First, WildEarth observes that the 

consent decrees required the private monitors to operate in 

“substantial compliance” with 40 C.F.R. Part 58, the quality 

assurance requirements under which regulatory monitors 

operate. But “substantial compliance” is not “full 

compliance,” and the EPA could reasonably draw a distinction 

between the two. Moreover, data from regulatory 

monitors—which must be collected in compliance with 40 

C.F.R. Part 58—undergo post-collection auditing and 

verification processes. See, e.g., 40 C.F.R. pt. 58, app. A, § 3. 

Those post-collection processes could not be conducted for the 

private monitor data. Accepting WildEarth’s argument would 

require us to conclude that the EPA must apply less stringent

post-collection validation requirements to data collected from 

private monitors in “substantial compliance” with the agency’s 

data-collection regulations than the agency applies to data 

collected from regulatory monitors in actual compliance with 

those regulations. We see no reason to embrace that 

counterintuitive result.

Second, WildEarth points out that the EPA has 

encouraged other federal entities to take notice of the private 

monitoring data. The EPA acknowledges that it argued, in a 

judicial proceeding supporting entry of the same consent 

decrees mandating the private monitoring, that the private 

monitors would provide data that would be “reliable and of 

good quality” and “useful in assisting regulators.” Resp’t’s

Br. 57. And indeed the data have proven helpful to the EPA in 

other regulatory contexts. On the basis of the private data, for 
26

example, the EPA informed the Forest Service that Uinta Basin 

ozone concentrations “exceed the NAAQS” and are a “serious 

problem.” Supp. JA 387. 

We agree with WildEarth that an agency may be required 

to articulate why data are sufficiently reliable for one purpose 

but not for another. See Cnty. of L.A. v. Shalala, 192 F.3d 

1005, 1022 (D.C. Cir. 1999). But the EPA has done so here. 

That the data may be sufficiently reliable to warrant identifying 

ozone as a serious issue for a Forest Service analysis under one 

statutory provision does not necessarily mean that the data are 

reliable enough to compel a nonattainment designation under a 

different statutory regime. To hold otherwise would require 

the EPA wholly to blind itself to potentially useful private data 

for any purpose if it were to consider that data insufficiently 

reliable for one purpose. There is no basis for constraining the 

agency in that way.

That the EPA partially relied on the private data in the 

course of this very designation process does not undercut that 

conclusion. While “unclassifiable” represents a single 

statutory designation, see 42 U.S.C. § 7407(d)(1)(A)(i)–(iii), 

the EPA further divided that classification into two

sub-categories: “unclassifiable/attainment” and 

“unclassifiable.” See 2008 Designations Rule, 77 Fed. Reg. at 

30,089. “Historically for ozone,” the EPA designates as 

“ ‘unclassifiable/attainment’ ” those areas for which “air 

quality information is not available because the areas are not 

monitored.” Id. at 30,090. But in Uinta Basin, the EPA 

instead designated the area “unclassifiable” after determining 

that the private monitoring “detected levels of ozone that 

exceed the NAAQS.” Id. at 30,089.

There is no arbitrariness in the EPA’s choice 

partially—but not fully—to rely on the private data. At the 
27

outset, we note that the parties point us to no material 

differences between an “unclassifiable/attainment” and an 

“unclassifiable” designation, and we are aware of none. See 

40 C.F.R. § 51.1100(g) (“Attainment area means, unless 

otherwise indicated, an area designated as either attainment, 

unclassifiable, or attainment/unclassifiable.”); cf. 42 U.S.C. 

§ 7471 (instructing the EPA to give the same treatment to 

“unclassifiable” and “attainment” areas for SIP purposes). 

But given the EPA’s decision to create two different 

unclassifiable designations, we will assume arguendo that 

materially different regulatory burdens attend each 

designation. Even then, however, we agree with the EPA that 

it was reasonable to conclude that it would be inappropriate to 

label the Uinta Basin area “unclassifiable/attainment”: the 

private data, even if unverified, at least implied that a NAAQS 

violation was possible, even if not conclusively proven to the 

agency’s satisfaction. WildEarth, moreover, points to no 

other area for which private—but not regulatory—monitoring 

suggested a NAAQS violation. It thus appears that Uinta 

Basin differed from all other areas meriting an 

“unclassifiable/attainment” designation. We conclude that 

the EPA’s conclusion partially—but not fully—to credit the 

private data was reasonable and non-arbitrary, particularly in 

light of the “extreme deference” we owe the agency. See 

Catawba Cnty., 571 F.3d at 41.

In sum, the EPA reasonably declined to rely on data that it 

considered of insufficient quality for designations purposes. 

With that conclusion, and having reviewed the remainder of 

WildEarth’s challenges and determined that they lack merit, 

we deny the group’s petition for review. See Catawba Cnty., 

571 F.3d at 52.
28

C. SIERRA CLUB

Petitioner Sierra Club challenges the EPA’s refusal to use 

uncertified 2011 air-quality data during the designation

process, a decision that resulted in 15 counties avoiding 

nonattainment designations. Finding the EPA’s actions 

rational and in accordance with the Clean Air Act, we deny 

Sierra Club’s petition.

1. Sierra Club Background

In furtherance of the Clean Air Act’s “ ‘core principle’ of 

cooperative federalism,” EPA v. EME Homer City Generation, 

L.P., 134 S. Ct. 1584, 1602 n.14 (2014), states take the lead in 

the collection of air-quality data. In doing so, states operate 

regulatory monitors under an array of “[e]xhaustive technical 

specifications” promulgated by the EPA. Catawba Cnty., 571 

F.3d at 30; see 40 C.F.R. pt. 58. States “edit[]” and 

“validate[]” the collected data pursuant to the EPA-mandated 

procedures and report it to the EPA according to a prescribed 

schedule. See 40 C.F.R. § 58.16(b)–(c). Data collected in 

each quarter must be “edited, validated and entered” into the 

EPA’s system within ninety days of the end of the quarter. Id. 

“For example, the data for the reporting period January 1–

March 31 are due on or before June 30 of that year.” Id. 

§ 58.16(b). Post-auditing, the data are still considered 

“uncertified” when submitted to the EPA.

While uncertified data from the first quarter (i.e., January 

1 to March 31) become available to the EPA as of June 30, 

those data remain subject to continuing audits and edits by 

states. The data collection process reaches completion only 

when a state provides final certification that the necessary 

“ambient concentration and quality assurance data are 

completely submitted . . . and . . . are accurate.” Id. 

§ 58.15(a). The EPA requires certification by May 1 of the 
29

following calendar year for all data collected in the previous 

year. Id. § 58.15(a)(2). States therefore had to certify their 

2011 data by May 1, 2012. 

As explained, because the 2008 ozone NAAQS represent 

a three-year average, the EPA needs air-quality data from three 

sequential calendar years to classify an area as attainment or 

nonattainment (as opposed to unclassifiable). See 2008 

Designations Rule, 77 Fed. Reg. at 30,089. In the designation

process for the 2008 NAAQS, the EPA gave each state a 

choice between two options: (i) early-certify 2011 data by 

February 29, 2012, in which event the EPA would consider 

2009 to 2011 data for the designation process for that state 

(Option One); or (ii) decline to early-certify (and stick to the 

normal May 1 certification deadline), in which event the EPA 

would use 2008 to 2010 data for designations in that state 

(Option Two). See id. at 30,091.

At least eight states selected Option Two. Sierra Club 

identifies over one dozen counties within those eight states for 

which the choice between Option One and Option Two (i.e., 

the choice between designations based on 2008 to 2010 data 

versus 2009 to 2011 data) allegedly meant that those counties 

avoided nonattainment designations. See Letter from Robert 

Ukeiley, Counsel, Sierra Club to EPA, Re: Designations for the

2008 Ozone NAAQS Docket ID 

No. EPA-HQ-OAR-2008-0476 at 3 tbl.1 (Feb. 3, 2012). 

Sierra Club contends that the EPA was compelled to use 2009 

to 2011 data for those areas. We disagree and conclude that 

the EPA’s actions were non-arbitrary.

2. Uncertified Data Challenge

Sierra Club first notes that, at the time of the designation

process, the EPA possessed uncertified 2011 data for all areas. 

Because the agency’s regulations require the submission of 
30

uncertified data within ninety days of the end of the quarterly 

reporting period, see 40 C.F.R. § 58.16(b), the EPA had all 

2011 uncertified data in its possession by the end of March. It 

should have used that data, Sierra Club argues, 

notwithstanding the lack of certification. We are 

unpersuaded.

While the uncertified data must undergo preliminary 

auditing and quality checks before submission to the EPA, see 

id. § 58.16(c), those preliminary quality control measures are 

just that—preliminary. As the EPA explains, the data remain 

subject to continuing checks and revisions by the states until 

final certification. Resp’t’s Br. 66. Accordingly, the EPA 

reasonably “does not presume that data [validation and 

auditing] processes are complete and accurate until” the final 

data certification. Id. at 46. Mindful of the significant 

deference we owe the EPA in matters concerning data quality 

or sufficiency, see Catawba Cnty., 571 F.3d at 41, we see no 

basis for second-guessing the EPA’s considered judgment on 

the issue.

Sierra Club next argues that, even if the agency acted 

reasonably in refusing to rely on uncertified data, it acted 

arbitrarily in declining to delay the designation process until all 

states had certified their 2011 data by the standard May 1 

deadline. After all, Sierra Club notes, the consent decree 

under which the EPA conducted the designation process 

allowed the agency until May 31, 2012, to promulgate the final 

designations. 2008 Designations Rule, 77 Fed. Reg. at 

30,091.

Sierra Club, however, identifies no authority obligating 

the EPA to wait until the last possible minute to promulgate its 

designations. And in this case, doing so would have made 

little sense. The EPA entered into the consent decree 
31

precisely to settle allegations that it had already missed the 

Act’s statutory deadlines for promulgating the 2008 ozone 

NAAQS designations. See id. Accepting Sierra Club’s 

position would effectively call for the EPA to infringe the 

Act’s deadlines still further. In any event, as the EPA 

explained in denying Sierra Club’s petition for reconsideration 

of the designations after the May 1, 2012, certification deadline 

passed and 2009 to 2011 data were fully certified and available 

to the EPA, “[n]ew technical data become available on a 

regular basis.” Letter from Lisa P. Jackson, Adm’r, EPA to 

Robert Ukeiley, Counsel, Sierra Club enclosure p.2 (Dec. 14, 

2012). The EPA reasonably concluded that delay “to consider 

such new information would result in a never-ending process 

in which designations are never finalized.” Id. Indeed, 

Sierra Club itself has already filed a petition for 

reconsideration based on 2010 to 2012 data. See Sierra Club 

Reply Br. 8. The EPA could reasonably conclude that the 

process must end at some point. We conclude that the agency 

did not act arbitrarily in ending it here. Cf. Catawba Cnty., 

571 F.3d at 51 (“New York’s underlying complaint is that the 

iterations should have continued, perhaps ad infinitum. But 

such a process is inconsistent with the CAA: Congress 

imposed deadlines on EPA and thus clearly envisioned an end 

to the designations process.”). 

With that conclusion, and having reviewed the remainder 

of Sierra Club’s challenges and determined that they lack 

merit, we deny the group’s petition for review. See Catawba 

Cnty., 571 F.3d at 52.

D. MISSISSIPPI 

The State of Mississippi challenges the EPA’s use of 2008 

to 2010 data to classify the counties within the Memphis, 

Tennessee area, an analysis that resulted in a nonattainment 
32

designation for part of DeSoto County, Mississippi. Because 

we conclude that the EPA’s actions were rational and in 

accordance with the Clean Air Act, we deny Mississippi’s 

petition for review.

1. Mississippi Background

In Mississippi and elsewhere, the EPA conducted the 

designations for metropolitan areas through a two-step process. 

First, the EPA examined air-quality data from all regulatory 

monitors in a metropolitan area. If no monitors in the area 

showed a NAAQS violation, no county in the area would be 

designated nonattainment. In that event, there would be no 

second step. But if a single monitor from the area showed a 

NAAQS violation, the county housing the violating monitor 

would be designated nonattainment. See 2008 Guidance at 3–

4. In that case, the EPA would proceed to the second step for 

that metropolitan area.

The second step took account of the fact that the Act 

mandates nonattainment designations not only for areas 

themselves exceeding the relevant NAAQS, but also for all 

areas that “contribute[]” to a NAAQS violation in a “nearby 

area,” even if the “contributing” area’s air quality—considered 

alone—meets the NAAQS. See 42 U.S.C. § 7407(d)(1)(A)(i); 

2008 Guidance at 3–4. In the second step, the EPA assessed 

each county in a metropolitan area with a violating monitor on 

a case-by-case basis to determine if the county contributed to 

the identified violation. If, on the basis of a multi-factor test, 

the EPA determined that a county “contributed” to the NAAQS 

exceedance at the violating monitor in another county, the EPA 

also designated the contributing county as nonattainment. We 

have repeatedly upheld multi-factor contribution analyses as 

consistent with the Act’s designation process under section 

107—a conclusion that Mississippi does not challenge here. 
33

See, e.g., ATK Launch Sys., 669 F.3d 330; Catawba Cnty., 571 

F.3d 20. See generally supra § II.

In 2011 and 2012, the EPA conducted that two-step 

designation process for the Memphis CBSA. The Memphis 

CBSA consists of several counties in Tennessee (Shelby, 

Tipton, and Fayette), Mississippi (DeSoto, Marshall, Tate, and 

Tunica), and Arkansas (Crittenden). See Office of Mgmt. & 

Budget, OMB Bulletin No. 10-02, Update of Statistical Area 

Definitions and Guidance on Their Uses 40 (Dec. 1, 2009). 

At the first step, the EPA evaluated 2008 to 2010 certified 

air-quality data and detected a NAAQS violation at the monitor 

in Shelby County, Tennessee. Proceeding to the second step, 

the EPA conducted the multi-factor analysis and determined 

that part of DeSoto County, Mississippi, contributed to the 

Shelby County violation. 

On December 9, 2011, the EPA notified Mississippi that it 

planned to designate part of DeSoto County as nonattainment 

when it promulgated the final designations in 2012. The EPA 

invited Mississippi (and all other states) to provide to the

agency by February 29, 2012, any additional information for 

consideration in the final designation process—including any 

early-certified 2011 data. See Memphis, TN-MS-AR Area 

Designations for the 2008 Ozone NAAQS 3–4 [hereinafter 

Memphis Area Designations]. Mississippi responded to the 

EPA’s multi-factor analysis with its own multi-factor analysis, 

disputing the EPA’s conclusion that DeSoto County 

contributed to any violation in Shelby County. Additionally, 

Mississippi and Tennessee—two of the three states in the 

Memphis CBSA—early-certified their 2011 data before the 

February 29, 2012, deadline. Arkansas—the third state in the 

Memphis CBSA—declined to early-certify any 2011 data. 
34

On May 21, 2012, the EPA published its final designations 

for the Memphis CBSA. At the first step of the two-step 

designation process, the agency used 2008 to 2010 data and 

again identified a violation at the Shelby County monitor. 

The EPA then moved to the second step and, after considering 

Mississippi’s multi-factor analysis and updating its own 

analysis accordingly, reiterated its original conclusion that part 

of DeSoto County contributed to the Shelby County violation. 

The agency therefore designated part of DeSoto County as 

nonattainment. See Memphis Area Designations at 16. 

Mississippi claims that designation was arbitrary and 

capricious. We disagree.

2. Challenge to the First Step of the 

Designation Process

First, Mississippi argues that the EPA acted arbitrarily in 

using 2008 to 2010 data for the first step of the two-step 

designation process (i.e., identifying violating monitors within 

a CBSA) even though the EPA possessed early-certified 2011 

data from Tennessee. The 2009 to 2011 data showed no 

NAAQS violation at the Shelby County monitor. 

Accordingly, Mississippi argues, no violation should have 

been identified at the first step of the two-step designation

process. But the EPA declined to evaluate Shelby County 

using the early-certified 2009 to 2011 data, instead using the 

2008 to 2010 data. True, the EPA must adequately explain why 

it declined to rely on the early-certified 2011 data. See City of 

Waukesha, 320 F.3d at 248. But the agency did so.

At the time of the final designations, the EPA had in its 

possession early-certified data from Mississippi and 

Tennessee, but not from Arkansas. In the first step of its 

two-step designation process, the EPA evaluates all air-quality 

monitors in a metropolitan area. Without 2011 Arkansas data, 
35

the EPA did not have a full set of 2011 data for the Memphis 

CBSA. The EPA only had data from different time 

horizons—2008 to 2010 data for the Arkansas portion of the 

Memphis CBSA, and 2009 to 2011 data for the Tennessee and 

Mississippi portions of that same CBSA. The agency 

declined to rely on this mismatched dataset. Instead, the EPA 

opted to rely on the most recent matched dataset in its 

possession: the complete set of 2008 to 2010 data. We see 

no reason—and Mississippi provides none—to declare 

irrational the EPA’s conclusion that comparing data from the 

same time period would be more appropriate than analyzing 

data from different time periods in the same evaluation

process. Cognizant of the substantial deference we owe the 

EPA in that highly technical evaluation, see Catawba Cnty., 

571 F.3d at 41, we find the EPA was entitled to rely on a 

matched dataset instead of a mismatched one.

Even assuming the EPA’s choice to rely only on matched 

datasets for the Memphis CBSA was reasonable (as we 

conclude it to be), Mississippi argues that the EPA’s approach 

nonetheless was arbitrary because the agency required a 

matched dataset for Memphis-area designations but allegedly 

relied on a mismatched dataset for Chicago-area designations. 

“[I]nconsistent treatment,” we have found, is a “hallmark of 

arbitrary agency action.” Id. at 51. There was no 

inconsistent treatment here, however. In both Chicago and 

Memphis, the EPA relied only on matched datasets in the 

designation process.

With regard to the Chicago metropolitan area, Illinois 

early-certified its 2011 data. Wisconsin and 

Indiana—portions of which also lie in the Chicago 

metropolitan area—did not early-certify. Illinois’s

early-certified data showed a violating monitor in the Chicago 

area. At the first step of the Chicago-area designation
36

process, the EPA relied on Illinois’s early-certified data, noted 

the violation, and thus proceeded to the second step’s 

multi-factor contribution analysis for all Chicago-area 

counties. 

Mississippi argues that, because the EPA only possessed 

early-certified data from Illinois, it used a mismatched dataset 

for Chicago’s designations. Consequently, Mississippi claims 

that the EPA took different approaches to dataset selection 

between Memphis and Chicago. Mississippi’s argument rests 

on a flawed understanding of the EPA’s designation process. 

At the first step of the process, a single violating monitor 

suffices to conclude the analysis and move to the second step. 

Though only Illinois had early-certified its data, that data 

showed a violating monitor. That was enough to terminate the 

first step of the process and move to the second step. It thus 

became irrelevant whether Wisconsin or Indiana data showed 

any violations: the EPA would proceed to the second step of 

the analysis regardless, based on the Illinois violation alone. 

The EPA therefore had a sufficient matched dataset of 2009 to 

2011 data (albeit data from only one state, Illinois) to proceed 

to the second step of the designation process using 2009 to 

2011 data alone. By contrast, the EPA had no matched dataset 

of 2009 to 2011 data in the Memphis area sufficient to 

complete the first step of the two-step process using that data 

alone. While data showing a single violating monitor are 

enough to end the first step and proceed to the second step, data 

showing all monitors in compliance would be needed to avoid

proceeding to the second step’s multi-factor analysis—i.e., to 

terminate the two-step process at the first step.

As a result, when Arkansas declined to early-certify its 

2011 data, the EPA could not determine if the entire Memphis 

CBSA showed NAAQS compliance at all monitors for the 
37

2009 to 2011 period; the agency lacked a sufficient 2009 to 

2011 matched dataset with which to do so. The EPA then 

relied on the most recent matched dataset sufficient to 

complete the first-step analysis (the 2008 to 2010 data), just as 

the EPA selected the most recent matched dataset sufficient for 

the first-step analysis of the Chicago area. The EPA therefore 

acted in a consistent manner in both areas, each time using the 

most recent matched datasets sufficient to complete the first 

step of the two-step designation process.

3. Challenge to the Second Step of the 

Designation Process

Mississippi also challenges the EPA’s application of the

second step of the designation process. The EPA acted 

arbitrarily, the state argues, in applying the multi-factor test 

and concluding that DeSoto County contributed to the Shelby 

County violation. We find no reason to disturb the EPA’s 

analysis.

First, Mississippi challenges the EPA’s differing 

articulations of the multi-factor test. As pronounced in the 

2008 Guidance, the EPA originally conceived of that test as 

consisting of nine factors. In making the final designations, 

the EPA applied a five-factor test. See supra § I.B–C, The 

state argues that the EPA’s “consolidat[ion]” of the test from 

nine to five factors was arbitrary and capricious. State & 

County Br. 15. We disagree. 

At the outset, we do not necessarily agree that the EPA 

was required to adhere to the 2008 Guidance. The 2008 

Guidance did not purport to be a legislative rule, and it 

explicitly provided that it was “not binding on states, tribes, the 

public or the EPA.” 2008 Guidance at 4; cf. Catawba Cnty., 

571 F.3d at 33–34 (materially similar guidance for PM2.5
38

NAAQS designations did not “create or modify legally binding 

rights”).

But even if we assume that the 2008 Guidance was

binding, the EPA did not deviate from it in the final 

designations. The “consolidation” of the factors was just 

that—a consolidation. It effected no deletion. During the 

final designation process, the agency simply grouped several 

of the 2008 Guidance factors into a single factor, the 

consideration of which necessarily entailed consideration of 

the multiple 2008 Guidance factors now residing within it. 

We find no examples of a final designation that failed to 

consider a factor identified in the 2008 Guidance. With “no 

bright line for any of the factors,” and with each factor 

“weighted considering the unique circumstances of each 

nonattainment area,” Response to Comments at 61, the 

consolidation worked no substantive change and thus affords 

no basis for setting aside the EPA’s analysis.

Second, Mississippi challenges the EPA’s specific 

application of the multi-factor test to DeSoto County. We 

accord the EPA “extreme deference” in applying that test, and 

will overturn the EPA’s designations only if the agency applied 

the test “so erroneously in a particular case that it could not 

have reasonably concluded that a county was contributing to 

nearby violations.” Catawba Cnty., 571 F.3d at 40–41. This 

is not such a case. The agency provided data showing that 

DeSoto County’s NOx and SO2 (ozone precursors) emissions 

were the second-highest in the Memphis CBSA. Memphis 

Area Designations at 8. The county also had the second 

highest number of workers commuting to counties with 

violating monitors, the second highest number of vehicle miles 

traveled in the CBSA, and the highest percentage population 

growth over the last decade. Those factors led the EPA to 

conclude that DeSoto County was integrated with Shelby 
39

County in a way that indicated ozone contribution. Id. at 9–

10. Additionally, meteorological analysis at the Shelby 

County monitor showed weather patterns characterized in part 

by winds blowing in from DeSoto County. Id. at 12. On 

those bases, the EPA reasonably concluded that DeSoto 

County contributed to the Shelby County violation. 

Mississippi principally argues that significant “commerce 

activity” occurring outside of DeSoto County (including 

interstate highway traffic, rail and barge transportation, diesel 

fuel sales, and air traffic) means that other counties contribute 

to the Shelby County violation more than DeSoto County 

does—and that, because some of those counties avoided 

nonattainment designations, DeSoto County should, too. 

Miss. Dep’t of Envtl. Quality, Air Div., 2008 Ozone Standard 

Designation Recommendation for DeSoto County, Mississippi 

8–12 (Feb. 2012). But the EPA considered that argument and 

determined in a well-reasoned analysis that the data from 

Mississippi was only one consideration in the designation

process. See Response to Comments at 97; see also Memphis 

Area Designations 1–31. The EPA concluded that DeSoto 

County did contribute to Shelby County’s violation in light of 

the many other factors the agency considered. Memphis Area 

Designations at 16.

Looking at the same data, Mississippi would simply reach 

a different conclusion. We, however, do not sit to 

second-guess the EPA’s conclusions in an area identified by 

the Congress as within the agency’s technical expertise. We 

only ask if the EPA “considered all relevant factors and 

articulated a rational connection between the facts found and 

the choice made.” ATK Launch Sys., 669 F.3d at 336 (internal 

quotation marks omitted). We conclude that it did.
40

With that conclusion, and having considered Mississippi’s 

other challenges and determined that they lack merit, we deny 

the state’s petition for review. See Catawba Cnty., 571 F.3d at 

52.

E. LAKE & PORTER COUNTIES, INDIANA

Petitioner Indiana challenges the designation of two of its 

counties as nonattainment. According to Illinois’s certified 

2009 to 2011 data, the monitoring site at Zion, Illinois 

exceeded the NAAQS by 1 part per billion (ppb). See 

Chicago-Naperville, Illinois-Indiana-Wisconsin Area 

Designations for the 2008 Ozone NAAQS at 7–8 [hereinafter 

Chicago Area Designations]. Zion is about sixty miles from 

the Indiana border and, like the Indiana counties at issue here, 

belongs to the Chicago-Naperville-Michigan City CSA. 

Following the 2008 Guidance, the EPA presumed that all 

counties in this CSA should be designated as nonattainment 

areas due to the Zion violation, and then conducted its 

five-factor analysis. The agency preliminarily concluded that 

three Indiana counties—Lake, Porter, and Jasper—should be 

included in the nonattainment area. 

In response to the EPA’s 120-day letter, Indiana pointed to 

multiple asserted flaws in the EPA’s analysis. Most relevant 

here, it said that the agency had failed to account for the impact 

of a recent statutory change to Illinois’s vehicle emissions 

testing program. It also maintained that the agency’s 

meteorological analysis suffered from multiple weaknesses 

and inconsistencies.

The EPA ultimately reversed its designation of Jasper 

County, but finalized the nonattainment designations of Lake 

and Porter Counties. Chicago Area Designations at 21. 
41

Indiana now challenges those nonattainment designations as 

arbitrary and capricious. 

1. Challenge Regarding Illinois’s Vehicle 

Inspection Change

First, Indiana challenges the EPA’s position regarding 

Illinois’s statutory change. After a prior nonattainment 

designation, Illinois had established a vehicle inspection and 

maintenance program that covered all model years beginning 

in 1968.11 In 2006, however, Illinois exempted vehicles with 

model years between 1968 and 1995 from the testing 

requirements. See 625 Ill. Comp. Stat. 5/13C-15(a)(6)(L) 

(2012). Indiana maintains that it was the increase in vehicle 

emissions accompanying this exemption that directly caused 

the violation at the Zion monitor. Moreover, it contends that 

this legislative change amounted to an intentional violation of 

Illinois’s SIP. 

As the EPA points out, we made clear in Catawba County 

that a “contributing” county need not be the but-for cause of a 

violation in order to warrant a nonattainment designation. 

Resp’t’s Br. 94; see Catawba Cnty., 571 F.3d at 39 (“[E]ven 

were we to think that ‘contribute’ unambiguously means 

‘significantly contribute,’ we still disagree that ‘significantly 

contribute’ unambiguously means ‘strictly cause.’ ”). And 

here, regardless of Illinois’s statutory change, the EPA’s 

five-factor analysis demonstrated that both Lake and Porter 

 11 See Approval and Promulgation of Air Quality 

Implementation Plans; Illinois; Motor Vehicle Inspection and 

Maintenance, 64 Fed. Reg. 8,517, 8,519 (Feb. 22, 1999); Approval 

and Promulgation of Air Quality Plans; Illinois; Post-1996 Rate of 

Progress Plan for the Chicago Ozone Nonattainment Area, 65 Fed. 

Reg. 78,961, 78,967–68 (Dec. 18, 2000). 
42

Counties contributed to the Zion monitor. Chicago Area 

Designations at 6–21.

12 

The alleged illegality of Illinois’s statutory change does 

not affect our conclusion. The Clean Air Act offers other 

avenues for addressing a State’s failure to comply with its SIP. 

In particular, the EPA Administrator can call for a SIP revision 

after “find[ing] that the applicable implementation plan for any 

area is substantially inadequate” to comply with the NAAQS. 

42 U.S.C. § 7410(k)(5). The EPA declined to do so here and, 

instead, recently approved the Illinois change.13 Indiana has 

since petitioned the Seventh Circuit to review the EPA’s 

approval. See EPA 28(j) Letter (Oct. 22, 2014). That is the 

appropriate forum for challenging the Illinois change, which in 

no way diminished the contribution of the Indiana counties.

 12 Indiana protests that there likely would have been no violation 

at all at the Zion monitor if it were not for the emissions resulting 

from the statutory change. That argument is merely a rephrasing of 

the but-for causation rule that we rejected in Catawba County. In 

any event, the argument is not supported by the Indiana modeling 

analyses upon which it is based. See Letter from Ind. Dep’t of 

Envtl. Mgmt. to EPA, Enclosure 1 at 27–30 (Apr. 13, 2012). The 

first analysis concluded only that the change in Illinois’s program 

contributed 0.2 ppb to the Zion violation—not enough to account for 

the 2009 to 2011 exceedance of 1 ppb. The second analysis rested 

on a factual premise that the State never adequately explained: that 

the statutory change caused the emission reduction benefits of 

Illinois’s vehicle emissions testing program to decrease by 35 per 

cent. 

13 See Approval and Promulgation of Air Quality 

Implementation Plans; Illinois; Amendments to Vehicle Inspection 

and Maintenance Program for Illinois, 79 Fed. Reg. 47,377 (Aug. 13, 

2014). 
43

2. Challenge to the EPA’s Response to Comments

Next, Indiana argues that the EPA failed to adequately 

respond to its comments about the impact of Milwaukee, 

Wisconsin’s emissions on the violation at the Zion monitor. 

According to the source apportionment modeling submitted by 

Indiana, the Milwaukee area contributed over 5 ppb to the Zion 

violation, while Lake, Porter, and Jasper Counties contributed 

4 ppb, 2 ppb, and 0.5 ppb, respectively. See Letter from Ind. 

Dep’t of Envtl. Mgmt. to EPA, Enclosure 1 at 13–14 (Apr. 13, 

2012). This, Indiana maintains, produced the “inconsistent 

and unfounded” result of nonattainment designations for the 

Indiana counties but an attainment designation for the 

Milwaukee area. Id. at 14. 

As an initial matter, we note that, because the Milwaukee 

area is not a single county but rather is a metropolitan area 

made up of five counties, Indiana’s argument is premised on an 

apples-to-oranges comparison. More important, we have no 

basis for finding the EPA’s designations inconsistent given that 

Indiana’s modeling—which was limited to meteorological 

linkages and therefore fell short of a full analysis—did not 

establish that Milwaukee “contributed to” the Zion violation 

under the agency’s five-factor analysis. By contrast, after 

conducting its full five-factor analysis, the EPA found that 

Lake and Porter Counties did contribute. Accordingly, the 

EPA’s determination regarding the Milwaukee metropolitan 

area was neither unreasonable nor inconsistent with its 

determination regarding the Indiana counties.

We also find that the EPA did adequately respond to 

Indiana’s comments about its modeling results, although 

without mentioning Milwaukee specifically. Indeed, the 

modeling was one of the factors that led the EPA to reconsider 

its designation of Jasper County. See Chicago Area 
44

Designations at 21 (describing Jasper County’s 0.5 ppb 

contribution as “not significant”). But the EPA simply 

disagreed with Indiana’s premise that 2 ppb and 4 ppb were 

insufficient contributions when considered as part of the 

five-factor test, for reasons that were reasonable and well 

explained. See id. at 18 (“In keeping with EPA’s ozone 

contribution levels used to select states that should be covered 

in regional emission control programs, 2 ppb to 4 ppb ozone 

concentration contributions are considered to be significant 

ozone contributions.”). 

3. The Remaining Challenges

Finally, we briefly consider Indiana’s remaining 

arguments. First, the record does not support Indiana’s claim 

that the EPA improperly relied on late-submitted data from 

Wisconsin’s Chiwaukee Prairie monitor, rather than relying 

solely on the Zion monitor data, in making the contribution 

determinations regarding the Indiana counties. See Chicago 

Area Designations at 8 (noting that the EPA considered the 

Wisconsin data in determining whether Kenosha County, 

Wisconsin (and not the Indiana counties) should be included in 

the Chicago nonattainment area); id. at 21–22 (describing 

bases for Lake, Porter, and Kenosha County designations). 

Second, the EPA did not fail to adequately explain why it used 

some 2006 to 2008 weather data in conducting the contribution 

analysis. The agency explained that historical data provided a 

“general conceptual model to explain the development and 

transport of high ozone levels in this area.” Addendum to 

Response to Comments at 7 (May 31, 2012); see also EPA 

Response to Indiana Pet. for Reconsideration 3. That 

explanation is deserving of the deference that we give to the 

EPA’s “evaluati[on] [of] scientific data within its technical 

expertise,” Catawba Cnty., 571 F.3d at 41 (quoting City of 

Waukesha, 320 F.3d at 247). 
45

In sum, we reject Indiana’s contention that the EPA’s 

designations of Lake and Porter Counties are arbitrary or 

capricious.

F. WISE COUNTY, TEXAS

Petitioners State of Texas; Wise County, Texas; Texas 

Commission on Environmental Quality; Devon Energy 

Corporation; Targa Resources Corporation; the Texas Pipeline 

Association; and the Gas Processors Association (collectively, 

Texas Petitioners) challenge the EPA’s designation of Wise 

County as nonattainment. They make several claims, 

including that the EPA subjected Wise County to arbitrarily 

disparate treatment, violated the U.S. Constitution and acted 

beyond its authority under the Clean Air Act. For the reasons 

discussed below, however, we do not disturb Wise County’s 

nonattainment designation.

1. Wise County Background 

Wise County is one of 22 counties in and around the 

Dallas–Fort Worth metropolitan area, which reports some of 

the most severe NAAQS violations in the country. Although 

Wise County has no monitor of its own, it borders several 

counties with a total of seven violating monitors, the closest of 

which reports ambient ozone levels that exceed the 2008 

NAAQS by 0.010 ppm. Moreover, because Wise County 

falls within the CSA of Dallas–Fort Worth, it is presumptively 

included within the nonattainment area.

Despite Wise County’s presumptive inclusion in the 

Dallas–Fort Worth nonattainment area, the EPA designated it 

as attainment when it updated the ozone NAAQS in 1997. 

For this reason, Texas did not include Wise County among the 

nine Dallas–Fort Worth counties it recommended for 

nonattainment status when it submitted its initial designations 
46

to the EPA in March 2009.14 On December 9, 2011, the EPA 

informed Texas that it planned to include Wise County in the 

Dallas–Fort Worth nonattainment area due to its 

“comparatively high emissions” and “close proximity . . . to 

violating monitors.” See Texas Area Designations for the 

2008 Ozone NAAQS at 13 [hereinafter Preliminary Dallas–

Fort Worth Area Designations].

The EPA redesignated Wise County based on the five-part 

“weight of the evidence analysis” articulated in the 2008 

Guidance. 15 See id. at 1–2. The second and third 

factors—emissions data and meteorology—factored 

prominently in the EPA’s decision. See id. at 13. As for 

emissions, the EPA concluded that oil-and-gas collection and 

production in the Barnett Shale reservoir—a gas-rich 

geological formation covering a significant portion of Wise 

County—resulted in Wise County’s inclusion among the eight 

highest emissions-producing counties in the Dallas–Fort 

Worth area.16

As for meteorology, although historic wind patterns in the 

Dallas–Fort Worth area suggest that air does not normally 

move from Wise County to counties with monitors registering 

 14 Initially, Texas based its recommended designations on 

air-quality data from 2005 to 2007. On October 31, 2011, Texas 

updated its initial designations with certified air-quality data from 

2008 to 2010.

15 As noted above, see supra § I.B–C, the 2008 Guidance 

initially established a nine-part test but the EPA subsequently 

collapsed those nine factors into five.

16 Specifically, Wise County had the fourth highest level of 

VOC emissions among nineteen counties in the Dallas–Fort Worth 

area and the sixth highest level of NOx emissions. Preliminary 

Dallas–Fort Worth Area Designations at 6 tbl.3.
47

NAAQS violations, the EPA concluded that Wise County was 

upwind of the monitors on days when ozone levels at the 

monitors peaked. See Preliminary Dallas–Fort Worth Area 

Designations at 10. In reaching this conclusion, the EPA used 

the National Oceanic and Atmospheric Administration’s 

Hybrid Single Particle Lagranian Integrated Trajectory

(HYSPLIT) model instead of relying solely on historic wind 

patterns in the Dallas–Fort Worth area. See id. HYSPLIT 

charts the path, or “back trajectory,” that air takes before it 

collects in a certain area. See id. According to the EPA, 

HYSPLIT modeling “is specifically designed to give an 

estimate of the probable path a parcel of air travels in reaching 

a given location at a given time” and is particularly 

illuminating for an area like Wise County, which has “light and 

variable” wind patterns. Response to Comments at 59–60.

After the EPA notified Texas that it planned to include 

Wise County in the Dallas–Fort Worth nonattainment area, 

numerous individuals and organizations submitted comments 

urging the EPA to reconsider its Wise County designation. 

One commenter insisted that other Texas counties were more 

responsible than Wise County for the NAAQS violations in the 

Dallas–Fort Worth area. Others argued that the EPA’s use of 

HYSPLIT modeling was arbitrary and capricious because, 

when designating other areas of the country, the EPA relied 

solely on historic wind patterns. According to these 

commenters, if the EPA had done the same with Wise County, 

it would not have designated Wise County as nonattainment 

because, according to historical wind patterns in the 

Dallas-Fort Worth area, Wise County was downwind of 

violating monitors more than 95 per cent of the time.

For its part, Petitioner Texas Commission on 

Environmental Quality (Texas Commission) submitted its own 

data based on photochemical grid source apportionment 
48

modeling. Source-apportionment modeling helps determine 

the potential future impact of an emissions source area (such as 

Wise County) on downwind monitors by “keep[ing] track of 

the origin of the [ozone] precursors creating the ozone.” 

Industrial Br. 7. It does so by combining “the 

meteorology/transport of air parcels during high ozone days 

with the emissions of [a] specific area[],” (here, Wise County),

“to evaluate potential impact on ozone levels.” Dallas-Fort 

Worth, Texas Final Area Designations for the 2008 Ozone 

NAAQS at 16 [hereinafter Final Dallas–Fort Worth Area 

Designations]. Although the EPA does not typically perform 

source-apportionment modeling during the NAAQS 

designation process, it “has used it in the past for large-scale 

rulemakings, such as the Clean Air Interstate Rule and Cross 

State Air Pollution Rule” and it considers 

source-apportionment modeling data if a state submits it. See 

Resp’t’s Br. 126. According to the Texas Petitioners, 

source-apportionment modeling suggests that Wise County 

emissions had only a negligible impact on the monitors 

registering NAAQS violations in the Dallas–Fort Worth area.

On April 30, 2012, the EPA issued its omnibus Response 

to Comments, many of which addressed the objections to the 

Wise County designation. The EPA defended HYSPLIT 

modeling as an “excellent tool[]” that it generally “prefer[s] 

over more basic assessments of wind speed and direction.” 

Response to Comments at 59. The EPA found HYSPLIT 

modeling to be a more precise measure of wind patterns than 

historic data, which data, according to the agency, is 

“potentially misleading in cases where wind speeds are light 

and variable, or vary substantially across the location of the 

meteorological observation and the monitored high ozone 

concentrations.” Id. These conditions existed in the Dallas–
49

Fort Worth area.17 Although the EPA acknowledged it could 

not always use HYSPLIT modeling, it nonetheless declined to 

ignore HYSPLIT data “where the information is available, 

even if the information is not available in all areas.” Response

to Comments at 59.

Along with its omnibus responses, the EPA issued its 

Final Dallas–Fort Worth Area Designations, which again 

applied the five-factor test. In that document, the EPA 

addressed the source-apportionment modeling submitted by 

the Texas Commission. The EPA took issue with the model’s 

methodology and made several amendments to it.

First, the EPA faulted the Texas Commission for not using 

data from an entire ozone season in its model. To account for 

this omission, the EPA examined not only the average (i.e., 

relative) impact of Wise County emissions on Dallas–Fort 

Worth monitors but also the absolute (i.e., maximum) impact 

of the emissions. See Final Dallas–Fort Worth Area 

Designations at 17. The average/relative approach advocated 

by the Texas Commission averaged the impact that Wise 

County emissions might have on the monitors on all days when 

the monitors were expected to exceed the ozone NAAQS. As 

a practical matter, averaging the impact of Wise County 

emissions meant that the Texas Commission’s model 

accounted for days on which wind patterns were not expected 

to move air pollutants from Wise County to the violating 

monitors. According to the EPA, the Texas Commission’s 

average approach had “the effect of masking the impacts that 

 17 See Final Dallas–Fort Worth Area Designations at 14 

(emphasizing that HYSPLIT modeling is especially appropriate for 

Wise County because Dallas–Fort Worth area “is generally 

characterized as having ozone exceedances with lower wind speeds 

and winds from many directions”).
50

occur on days when the wind does flow from Wise County to 

violating monitors,” an imprecision that was aggravated by the 

model’s limited dataset. See Resp’t’s Br. 136 (emphasis 

added). To account for this imprecision, EPA chose to look at 

the “direct,” or “absolute,” predicted effect that Wise County 

emissions would have on violating monitors rather than the 

average effect they were expected to have.

Second, the EPA noted that the Texas Commission’s 

source-apportionment model under-predicted peak ozone 

levels in the Dallas–Fort Worth area by a range of 0.005 to 

0.020 ppm. As a practical matter, the under-prediction meant 

that the Texas Commission’s model underestimated the 

number of days that Wise County contributed to NAAQS 

violations. To compensate therefor, the EPA examined the 

impact of Wise County emissions not only on days when the 

monitors exceeded the ozone NAAQS threshold of 0.075 ppm, 

but also on days when the monitors reported ozone levels in 

excess of 0.070 ppm.

After making these adjustments, the EPA reinterpreted the 

data from the Texas Commission’s source-apportionment 

model and concluded that it in fact supported including Wise 

County in the Dallas–Fort Worth nonattainment area. See 

Final Dallas–Fort Worth Area Designations at 20. 

Specifically, the EPA concluded that Wise County emissions 

(1) “resulted in 6 occurrences (over 4 days) of an impact of 

more than 0.75 ppb days” on Dallas–Fort Worth area monitors; 

(2) “had even larger impacts of up to 5 ppb on the Eagle 

Mountain Lake monitor,” a monitor one-half mile from the 

Wise County border that reported particularly severe NAAQS 

violations; and (3) “resulted in 9 occurrences (over 5 days) 

[causing] impacts of more than 0.75 ppb [to] occur[] at” 

Dallas–Fort Worth monitors. See id. For these reasons, the 
51

EPA maintained its inclusion of Wise County in the Dallas–

Fort Worth nonattainment area.

Dozens of individuals and organizations filed petitions for 

reconsideration of the EPA’s Wise County nonattainment 

designation, including the Texas Commission and the other 

Texas Petitioners. On December 14, 2012, the EPA denied 

each petition for reconsideration. Before us, the Texas 

Petitioners’ challenges to the EPA’s Wise County designation 

are grouped as follows: (1) The EPA’s use of HYSPLIT 

Modeling and its re-evaluation of the Texas Commission’s 

source-apportionment modeling were arbitrary and capricious; 

(2) the EPA’s designation of Wise County as nonattainment 

violated the Commerce Clause, U.S. CONST. art. I, § 8, cl. 3, 

the Tenth Amendment, id. amend. X, and the Due Process 

Clause, id. amend. V; and (3) the EPA violated at least one of 

several statutory provisions, including provisions of the Clean 

Air Act. We address each argument in turn.

2. The Arbitrary & Capricious Challenges

The Texas Petitioners’ primary arguments are that the 

EPA erred when it (i) used HYSPLIT modeling rather than 

prevailing wind patterns 18 and (ii) adjusted the Texas 

Commission’s source-apportionment modeling.19 To prevail 

on either argument, the Texas Petitioners must demonstrate 

that the EPA acted arbitrarily and capriciously and, to do that, 

they must show that the EPA either failed to consider “all 

relevant factors” or to articulate a “rational connection between 

the facts found and the choice made.” ATK Launch Sys., 669 

F.3d at 336. Mindful of the “extreme degree of deference” we 

owe to the EPA “when it is evaluating scientific data within its 

 18 See State & County Br. 45–46; Industrial Br. 14–26.

19 See State & County Br. 39–44; Industrial Br. 26–30. 
52

technical expertise,” Catawba Cnty., 571 F.3d at 41, and for 

the reasons stated below, we conclude that neither argument 

has merit.

i. HYSPLIT Modeling

The Texas Petitioners challenge the EPA’s use of 

HYSPLIT modeling on three fronts. First, they argue that the 

EPA could not legitimately use HYSPLIT modeling at all 

because HYSPLIT “cannot measure ozone formation or 

transport.” State & County Br. 45. Second, they contend 

that the EPA arbitrarily treated Wise County differently by 

using HYSPLIT modeling to designate it as nonattainment 

while using historic wind patterns to designate other allegedly 

similar counties as attainment. And third, they argue that, 

even among other counties that the EPA subjected to 

HYSPLIT modeling, it arbitrarily treated Wise County worse 

because the respective HYSPLIT models demonstrated that 

wind moved through those other counties—each of which the 

EPA designated as attainment—more frequently than it moved 

through Wise County. We address each argument in turn.

First, we find no merit in the Texas Petitioners’ 

conclusory argument that the EPA erred by using HYSPLIT 

modeling at all because HYSPLIT modeling “cannot measure 

ozone formation or transport. See State & County Br. 45–46. 

Indeed, we rejected a materially indistinguishable challenge in 

ATK Launch Systems, 669 F.3d at 339, a case involving the 

EPA’s 2006 fine particulate matter NAAQS designations. 

See id. at 334. We did so there because the EPA had taken 

“reasonable steps to ensure that the ‘HYSPLIT’ model’s 

limitations were considered.” Id. at 339 (quotation mark 

omitted).

Here too, the EPA took reasonable steps to account for 

HYSPLIT’s limitations by evaluating the 
53

source-apportionment modeling and historical wind data that 

the Texas Commission submitted during the comment period. 

See Final Dallas–Fort Worth Area Designations at 14–20, 23.

Because “[o]zone and ozone precursors can be transported to 

an area from sources in nearby areas or from sources located 

hundreds of miles away,” see 2008 Designations Rule, 77 Fed. 

Reg. at 30,088, the EPA reasonably concluded that HYSPLIT 

modeling, as a more precise measurement of the path taken by 

air masses containing ozone precursors, was useful in 

determining whether wind moving through Wise County could 

have transported emissions to the areas with the violating 

monitors.

Second, we find no merit in the Texas Petitioners’ 

argument that the EPA’s use of HYSPLIT modeling to 

designate Wise County as nonattainment amounts to arbitrarily 

disparate treatment. At the outset, it bears repeating that this 

Court has expressly sanctioned the EPA’s use of a holistic, 

multi-factor, totality-of-the-circumstances test for making 

NAAQS determinations, see ATK Launch Sys., 669 F.3d at 

336; Catawba Cnty., 571 F.3d at 39, and we have twice iterated 

that, when using a multi-factor test, “ ‘discrete data points’ are 

not determinative” because isolating any one discrete 

consideration “ ‘ignores the very nature of the . . . test, which is 

designed to analyze a wide variety of data on a case-by-case 

basis.’ ” ATK Launch Sys., 669 F.3d at 336 (quoting Catawba 

Cnty., 571 F.3d at 39) (emphasis added; alteration omitted)). 

Indeed, because the EPA’s “holistic assessment of numerous 

factors . . . drives the process,” we have recognized that “no 

single factor determines a particular designation.” Id. For 

this reason, the EPA could have subjected Wise County to 

arbitrarily disparate treatment only if it treated genuinely 

“similar counties” dissimilarly. Id. (emphasis in original). 

Given “significant” differences among counties, “a direct 

one-to-one comparison of the data,” including the methods 
54

used to measure such data, could be “inappropriate” or even 

“illogical.” Id. at 337.

As noted, the EPA conducted a HYSPLIT analysis in 

areas where it “believed [HYSPLIT] could provide additional 

insight into whether [the] area[] contribute[s] to 

nonattainment.” Resp’t’s Br. 110 n.47. The EPA reasonably 

determined that Wise County was one such area because 

Dallas–Fort Worth “experiences light wind speeds and winds 

from variable directions,” making HYSPLIT’s more 

sophisticated evaluation of wind patterns “a more useful tool 

than annualized wind patterns.” EPA Response to Pet. for 

Reconsideration from Devon Energy Corp. at 12. According 

to the EPA, this more refined analysis was not necessary for all 

areas of the country, particularly those in which “there was not 

significant debate over whether [they] should be included” in a 

nonattainment area. See Resp’t’s Br. 111. The EPA’s 

decision to use HYSPLIT analysis in one area but not in 

another fits comfortably within the agency’s “technical 

expertise,” Catawba Cnty., 571 F.3d at 41, and the EPA’s 

explanation for the differing treatment was rational. 

Moreover, although the Texas Petitioners direct this Court 

to other attainment areas that were not evaluated using 

HYSPLIT modeling—specifically, Orange County and 

Cattaraugus County in New York—the “significant” 

differences between Wise County and those counties “make a 

direct one-to-one comparison of the data underlying the 

analyses inappropriate.” ATK Launch Sys., 669 F.3d at 337. 

For instance, the EPA justified its Orange County attainment 

designation, in part, on its finding that “the density of [Orange 

County’s] emissions and vehicle usages are not of the level of 

the other counties in the CSA that are in New York’s proposed 

New York–Northern New Jersey–Long Island, NY-NJ-CT 

nonattainment area.” New York-Northern New Jersey-Long 
55

Island, NY-NJ-CT Nonattainment Area Designations for the 

2008 Ozone NAAQS at 16 (emphasis added). In contrast, the 

EPA justified its nonattainment designation of Wise County, in 

part, based on the “[t]he close proximity of [Wise County’s] 

comparatively high emissions to violating monitors.” Final 

Dallas–Fort Worth Area Designations at 23 (emphasis added).

Similarly, the EPA designated Cattaraugus County as 

attainment not only because “it is in the prevailing downwind 

direction from” the nearest violating monitor but also because 

“other monitors representative of Cattaraugus County, as well 

as the rest of upstate New York, are attaining the ozone 

standard.” See Attainment Status for Jamestown, New York 

and the Remainder of Upstate New York at 6 (emphasis 

added). But in the Dallas–Fort Worth area, seven violating 

monitors surrounded Wise County and some of the 

monitors—including one located one-half mile from Wise 

County’s border—reported levels of ambient ozone higher 

than anywhere else in the United States. Because “the core 

reason for the disparate designations” did not, as the Texas 

Petitioners would have it, reflect an “inconsistent approach to 

meteorology,” Industrial Br. 19, the EPA did not arbitrarily and 

capriciously treat Wise County differently by evaluating its 

wind patterns using HYSPLIT modeling instead of prevailing 

wind patterns. 

Third, when Wise County is compared to other counties 

for which the EPA used HYSPLIT modeling, it is clear that the 

EPA did not arbitrarily subject Wise County to disparate 

treatment. The Texas Petitioners point to four other 

counties—York, Dauphin and Lawrence Counties in 

Pennsylvania and Roane County, Tennessee—each of which 

the EPA designated as attainment notwithstanding HYSPLIT 

modeling demonstrated that air moved through them to 

violating monitors more frequently than through Wise County. 
56

But again, a holistic look at why the EPA designated these 

counties attainment but designated Wise County 

nonattainment demonstrates that the EPA did not act arbitrarily 

or capriciously. 

For example, York and Dauphin Counties are both near 

Lancaster County, which houses all violating monitors in the 

area. Because Lancaster County “is served by a single-county 

transportation-planning agency,” the EPA concluded that there 

were “strong jurisdictional arguments” for designating 

Lancaster as “a single county nonattainment area” and, 

accordingly, designating all other counties in the 

vicinity—including York and Dauphin—as attainment. See 

Pennsylvania Area Designations for the 2008 Ozone NAAQS

at 29–31. In contrast, Wise County is part of the Dallas–Fort 

Worth CSA (which means it is presumptively included in the 

Dallas–Fort Worth nonattainment area) and is also part of the 

Dallas–Fort Worth metropolitan planning organization (which 

implements programs and projects to reduce emissions across 

all included counties). In other words, jurisdictional and 

regional planning concerns—not differing approaches to 

HYSPLIT modeling data—drove the EPA’s conclusion that 

York and Dauphin Counties should be designated as 

attainment while Wise County should be designated as 

nonattainment. 

The Texas Petitioners’ comparisons of Wise County to 

Roane County, Tennessee, and Lawrence County, 

Pennsylvania, fare no better. Roane County is 

“geographically separated from the nearest county with a 

violating monitor” by approximately thirty miles and the ozone 

levels in the county between Roane and the next county with a 

violating monitor are in attainment. Resp’t’s Br. 122. The 

monitor in Lawrence County reports ozone levels that, at 0.066 

ppm, are well below the EPA’s NAAQS 0.075 ppm threshold. 
57

Moreover, the county with a violating monitor nearest to 

Lawrence County—Allegheny County—is not adjacent to 

Lawrence County. In contrast to both Roane County and 

Lawrence County, Wise County is adjacent to multiple 

counties reporting severe NAAQS violations, the closest of 

which is located a mere half mile from the Wise County line. 

The dispositive principle that the Texas Petitioners try to, 

but ultimately cannot, avoid is that under the EPA’s holistic 

analysis, “discrete data points” like the data from HYSPLIT 

modeling “are not determinative, because elevating them 

ignore[s] the very nature of the [holistic] test, which is 

designed to analyze a wide variety of data on a case-by-case 

basis.” ATK Launch Sys., 669 F.3d at 336 (quotation mark

omitted). Based on the foregoing analysis, we cannot say that, 

had the EPA declined to evaluate Wise County’s wind patterns 

using HYSPLIT modeling, Wise County “would not have been 

designated nonattainment.” Industrial Br. 19. Because none 

of the areas discussed by the Texas Petitioners is truly 

“similarly situated” to Wise County, and because the EPA fully 

and rationally supported its use of HYSPLIT modeling for 

Wise County, it did not act arbitrarily or capriciously. 

ii. Source-Apportionment Modeling

The Texas Petitioners also challenge the EPA’s 

modification of the Texas Commission’s 

source-apportionment modeling on three fronts. First, they 

argue that the EPA has not rationally explained why it 

considered the source-apportionment modeling’s projected 

absolute impact—instead of its projected relative impact—that 

wind from Wise County would have on violating Dallas–Fort 

Worth area monitors. Second, they argue that the EPA’s 

analysis of the Texas Commission’s source-apportionment 

modeling was inconsistent with its analysis of 
58

source-apportionment modeling submitted in connection with 

Illinois’s designation of Lake County. And third, they argue 

that the EPA’s decision to examine the model’s projected 

absolute impact rather than its relative impact violated the 

EPA’s earlier modeling guidance. 

We note, at the outset, that the EPA’s application, 

interpretation and modification of source-apportionment 

modeling plainly fall “within its technical expertise” and thus 

we owe it “an extreme degree of deference.” ATK Launch 

Sys., 669 F.3d at 338 (quotation marks omitted). To withstand 

judicial review, the EPA needs to articulate only a “rational 

connection between the facts found and the choice made,” 

Burlington Truck Lines, 371 U.S. at 168, show that it treated 

“similar counties” similarly, ATK Launch Sys., 669 F.3d at 336 

(emphasis in original), and demonstrate that it did not run afoul 

of binding guidance, see generally Appalachian Power Co. v. 

EPA, 208 F.3d 1015, 1020–23 (D.C. Cir. 2000). Because the 

EPA has done all three, we will not disturb its designation of 

Wise County as nonattainment based on the Texas Petitioners’ 

objections to its interpretation of the Texas Commission’s 

source-apportionment modeling. 

First, the Texas Petitioners challenge the EPA’s decision 

to reinterpret the source-apportionment modeling submitted by 

the Texas Commission. As discussed, supra § III.F.1, when 

the EPA received the Texas Commission’s 

source-apportionment modeling data during the comment 

period, it observed that the model did not rely on data from an 

entire ozone season. Rather, the projections in the Texas 

Commission’s model relied on data from June 2006 only. The 

Texas Commission based its approach on the fact that June 

2006 purportedly presented “an exceptionally rich set of air 

quality and meteorological measurements,” “had the most 

high-ozone days of any month” and experienced “all the 
59

meteorological conditions linked to formation of high ozone 

concentration.” See Response to Texas Commission on 

Environmental Quality’s Reconsideration Pet. at 3. 

Despite these assurances, the EPA did not agree that one 

month of data, even an “exceptionally rich” month, was 

sufficient. Specifically, the EPA observed that the ozone 

season in the Dallas–Fort Worth area was bimodal (i.e., 

reporting its highest ozone values in July-September but 

experiencing a lower ozone peak in May-June) and that the 

Texas Commission’s reliance on limited data meant that it 

failed to account for “all of the meteorology regimes conducive 

for ozone events” in the Dallas–Fort Worth area. See Final 

Dallas–Fort Worth Area Designations at 16. According to the 

EPA, “emphasis on the average modeled impact is more 

appropriate when a full ozone season of model results is 

available.” See Resp’t’s Br. 131. Because the Texas 

Commission’s model was premised on baseline data excluding 

“events that happen in mid to late-summer that often set” the 

Dallas–Fort Worth area’s ozone levels, the EPA examined 

both the projected average impact and the projected maximum 

impact of Wise County emissions. See Final Dallas–Fort 

Worth Area Designations at 16.

At bottom, the EPA had a “basic obligation” to conduct 

“reasoned decisionmaking.” Catawba Cnty., 571 F.3d at 25. 

When presented with the Texas Commission’s 

source-apportionment modeling, the EPA determined that it 

“needed to be carefully evaluated and could not simply be 

accepted at face value,” Resp’t’s Br. 126, identified several 

methodological flaws in the Texas Commission’s data, 

adjusted the Texas Commission’s submissions to account for 

the flaws and articulated, quite thoroughly, a “rational 

connection between the facts found and the choice made.” 

Burlington Truck Lines, Inc., 371 U.S. at 168. On this record, 
60

we cannot say that the EPA acted arbitrarily or capriciously in 

re-evaluating the Texas Commission’s source-apportionment 

modeling data. Rather, the EPA’s thorough treatment of all 

available data indicates that it in fact “surpassed” its 

“obligation of reasoned decisionmaking.” Catawba Cnty.,

571 F.3d at 25. 

Second, the Texas Petitioners argue that the EPA’s 

modification to the Texas Commission’s 

source-apportionment modeling subjected Wise County to 

arbitrarily disparate treatment. They compare the EPA’s 

interpretation of the Texas Commission’s modeling to its 

interpretation of source-apportionment modeling for the 

Chicago area. Specifically, they argue that (1) emissions 

from Jasper County, a Chicago-area county with attainment 

status, had a projected average impact on violating monitors 

similar to Wise County’s; (2) the EPA should have evaluated 

the average impact of Wise County’s emissions on violating 

monitors as it did for Jasper County; and (3) the EPA’s 

evaluation of Wise County’s maximum, as opposed to relative, 

estimated impact was, accordingly, inconsistent and resulted in 

an arbitrarily different result between Wise County and Jasper 

County. 

Again, we emphasize that applying different methods to 

different areas, standing alone, does not give rise to arbitrarily 

disparate treatment and given “significant” relevant 

differences between two areas, “a direct one-to-one 

comparison of the data” or the methods used to measure such 

data can be “inappropriate.” ATK Launch Sys., 669 F.3d at 

337. Here, the significant difference lies in the quality of data 

submitted by the Texas Commission compared to that 

submitted in support of Jasper County. Specifically, the 

source-apportionment model submitted in support of the 

Chicago-area designations included data from a full ozone 
61

season, which made “emphasis on the average modeled impact 

. . . more appropriate.” Resp’t’s Br. 131. As noted, the EPA 

modified the Texas Commission’s source-apportionment 

model because it did not include data from a full ozone season. 

Moreover, the EPA had to compensate for the fact that the 

Texas Commission’s source-apportionment model 

underestimated the number of days that monitors in the Dallas–

Fort Worth area exceeded the ozone NAAQS because the 

model under-predicted peak ozone levels around the monitors, 

sometimes by a significant range. The source-apportionment 

model for Jasper County, however, had the opposite problem; 

it did not account for recent emissions reductions at a Jasper 

County power plant and thus the Chicago-area 

source-apportionment model over-reported Jasper County’s 

emissions impact. See Chicago Area Designations at 9–10. 

Stated differently, because Wise County’s model 

under-reported its emissions impact and Jasper County’s 

model over-reported its emissions impact, the EPA reasonably 

concluded that the two counties should receive different 

attainment designations. 

Third, the Texas Petitioners argue that the EPA arbitrarily 

and capriciously deviated from its earlier guidance on 

source-apportionment modeling, which guidance allegedly 

expressed a preference for relative, rather than absolute, 

modeling. Specifically, they argue that the EPA’s reliance on 

Wise County’s maximum potential emissions impact directly 

conflicts with the EPA’s 2007 “Guidance on the Use of Models 

and Other Analyses for Demonstrating Attainment of Air 

Quality Goals for Ozone, PM2.5, and Regional Haze” (2007 

Attainment Guidance). In that guidance, the EPA stated that 

its “recommended test is one in which model estimates are 

used in a ‘relative’ rather than ‘absolute’ sense.” Id. at 15. 
62

As a threshold matter, the 2007 Attainment Guidance does 

not speak to the use of source-apportionment modeling in the 

designation process; rather, it recommends procedures that a 

state can use after it has been designated as nonattainment to 

show that its proposed emission control strategy will 

eventually result in attainment status. But even assuming that 

the 2007 Attainment Guidance informs the current NAAQS 

designation process, the EPA did not err by deviating from it. 

Indeed, the 2007 Guidance expressly contemplates deviations 

in appropriate cases:

This document does not substitute for any 

Clean Air Act provision or EPA regulation, nor 

is it a regulation itself. Thus, it does not 

impose binding, enforceable requirements on 

any party, nor does it assure that EPA will 

approve all instances of its application. The 

guidance may not apply to a particular 

situation, depending upon the circumstances. 

The EPA and State decision makers retain the 

discretion to adopt approaches on a 

case-by-case basis that differ from this 

guidance where appropriate. . . . 

Users are cautioned not to regard statements 

recommending the use of certain procedures or 

defaults as either precluding other procedures 

or information, or providing guarantees that 

using these procedures or defaults will result in 

actions that are fully approvable. . . . EPA 

cannot assure that actions based upon this 

guidance will be fully approvable in all 

instances.

2007 Attainment Guidance at ix.
63

As noted, the EPA fully explained why it revised and 

independently evaluated the Texas Commission’s 

source-apportionment modeling to account for “the limited 

data set [the Texas Commission] relied upon.” Resp’t’s 

Br. 136. Because the 2007 Attainment Guidance did not 

compel the EPA to limit its consideration to relative projected 

impacts, and because the EPA articulated a “rational 

connection between the facts found and the choice made,” 

Catawba Cnty., 571 F.3d at 41, it did not act arbitrarily or 

capriciously when it relied on Wise County’s absolute, rather 

than relative, impact on NAAQS-violating monitors.

The fundamental deficiency in the Texas Petitioners’ 

challenges to the EPA’s revision of the Dallas–Fort Worth area 

source-apportionment model is that, to establish that “EPA’s 

administration of the complicated provisions of the Clean Air 

Act” was erroneous, Catawba Cnty., 571 F.3d at 41, they have 

to demonstrate more than mere disagreement with the EPA’s 

reasoning. Barring an unreasonable or irrational application 

of the “scientific data within [the EPA’s] technical expertise,” 

City of Waukesha, 320 F.3d at 247, we cannot say that the EPA

acted arbitrarily or capriciously. The record plainly shows 

that the EPA “considered all relevant factors and articulated a 

‘rational connection between the facts found and the choice 

made’ ” when it declined to accept the Texas Commission’s 

source-apportionment model without modification. Catawba 

Cnty., 571 F.3d at 41 (quoting Burlington Truck Lines, 371 

U.S. at 168). We therefore hold that the EPA did not act 

arbitrarily or capriciously when it did so.
64

3. The Constitutional Challenges

In this section, we address three constitutional challenges 

that Texas, Wise County, and the Texas Commission on 

Environmental Quality (collectively, Texas State Petitioners) 

raise to the EPA’s designation of Wise County, Texas as a 

nonattainment area. 

i. The Tenth Amendment & The Spending Clause

The Texas State Petitioners, joined by the Mississippi 

Petitioners, argue that § 7407(d)(1)(B) and related sections of 

the Clean Air Act—at least to the extent that they authorize the 

EPA to override the State’s designation and declare Wise 

County a nonattainment area—violate the Tenth Amendment 

and exceed the Congress’ authority under the Spending Clause. 

First, the Texas State Petitioners maintain that 

§ 7407(d)(1)(B) unlawfully permits the EPA to 

“commandeer[] State regulators to enforce a federal regulatory 

program.” State & County Br. 32. The section grants the 

EPA authority to “make such modifications as the 

Administrator deems necessary to the designations of the areas 

. . . submitted [by the States].” 42 U.S.C. § 7407(d)(1)(B)(ii). 

According to the petitioners, “[w]hen EPA overrides a State, it 

compels State regulators to enforce a myriad of federal 

requirements involving emissions controls, clean fuel 

programs, transportation and land use limitations in the 

designated area.” State & County Br. 33 (citing 42 U.S.C. 

§§ 7511 et seq. (outlining requirements specific to ozone 

nonattainment areas)). 

The Texas State Petitioners are correct that “the Federal 

Government may not compel the States to implement . . . 

federal regulatory programs,” Printz v. United States, 521 U.S. 
65

898, 925 (1997).20 But the Clean Air Act does not do that. 

Instead, the statutory scheme authorizes the EPA to 

promulgate and administer a federal implementation plan of its 

own if the State fails to submit an adequate state 

implementation plan. See 42 U.S.C. § 7410(c). And as we 

recently noted, the Supreme Court has “repeatedly affirm[ed] 

the constitutionality of federal statutes that allow States to 

administer federal programs but provide for direct federal 

administration if a State chooses not to administer it.” Texas 

v. EPA, 726 F.3d 180, 196–97 (D.C. Cir. 2013) (citing New 

York v. United States, 505 U.S. 144, 167–68, 173–74 (1992); 

Hodel v. Va. Surface Mining & Reclamation Ass’n, Inc., 452 

U.S. 264, 288 (1981)). Here, too, the “full regulatory burden 

will be borne by the Federal Government” if a State chooses 

not to submit an implementation plan. Va. Surface Mining & 

Reclamation Ass’n, 452 U.S. at 288. Under these 

circumstances, “there can be no suggestion that the Act 

commandeers . . . the States.” Id.

Second, the Texas State Petitioners maintain that the 

Clean Air Act’s sanctions for noncompliant states impose such 

a steep price that State officials effectively have no choice but 

to comply—in contravention of the Supreme Court’s decision 

in National Federation of Independent Business v. Sebelius 

(NFIB), 132 S. Ct. 2566, 2603 (2012) (plurality opinion). See

 20 See Nat’l Fed’n of Indep. Bus. v. Sebelius, 132 S. Ct. 2566, 

2602 (2012) (plurality opinion) (noting that the Court has struck 

“down federal legislation that commandeers a State’s legislative or 

administrative apparatus for federal purposes”); Printz, 521 U.S. at 

933 (invalidating federal legislation compelling State law 

enforcement officers to perform federally mandated background 

checks on handgun purchasers); New York v. United States, 505 U.S. 

144, 174–77 (1992) (invalidating a provision of a federal statute 

compelling a State either to take title to nuclear waste or to enact 

particular state waste regulations). 
66

State & County Br. 33–34. The Act requires the EPA to 

impose sanctions on a State that fails to submit an adequate 

plan or implement an approved plan if it does not correct the 

deficiency within 18 months. See 42 U.S.C. § 7509(a). The 

focus of the petitioners’ challenge is the sanction regarding 

federal highway funds. Under the Act, the EPA 

Administrator may prohibit the approval of any transportation 

projects or grants within the nonattainment area, except those 

that the Secretary of Transportation determines are intended to 

resolve a demonstrated safety problem and will likely result in 

a reduction in accidents. Id. § 7509(b)(1)(A). The Secretary 

of Transportation may also continue to approve a number of 

other kinds of projects and grants, notwithstanding the EPA 

Administrator’s prohibition. Id. § 7509(b)(1)(B)(i)–(viii) 

(authorizing continued approval of projects and grants 

including capital programs for public transit, projects affecting 

bus lanes and high occupancy vehicle lanes, programs that 

improve traffic flow, and programs that “would improve air 

quality and would not encourage single occupancy vehicle 

capacity”).

As Chief Justice Roberts noted in NFIB, the Supreme 

Court has “long recognized that Congress may use” the power 

given it by the Spending Clause “to grant federal funds to the 

States, and may condition such a grant upon the States’ ‘taking 

certain actions that Congress could not require them to take.’ ” 

NFIB, 132 S. Ct. at 2601 (quoting Coll. Sav. Bank v. Fla. 

Prepaid Postsecondary Educ. Expense Bd., 527 U.S. 666, 686 

(1999)). “Such measures ‘encourage a State to regulate in a 

particular way, [and] influenc[e] a State’s policy choices.’ ” 

Id. at 2601–02 (quoting New York, 505 U.S. at 166) (alterations 

in original). “The conditions imposed by Congress ensure 

that the funds are used by the States to ‘provide for the . . . 

general Welfare’ in the manner Congress intended.” Id. at 

2602 (quoting U.S. CONST., art. I, § 8, cl. 1). 
67

“At the same time,” the Chief Justice continued, the 

Court’s “cases have recognized limits on Congress’s power 

under the Spending Clause to secure state compliance with 

federal objectives.” Id. The Court has “repeatedly 

characterized . . . Spending Clause legislation as ‘much in the 

nature of a contract.’ ” Id. (quoting Barnes v. Gorman, 536 

U.S. 181, 186 (2002) (quoting Pennhurst State Sch. & Hosp. v. 

Halderman, 451 U.S. 1, 17 (1981))). “The legitimacy of 

Congress’s exercise of the spending power ‘thus rests on 

whether the State voluntarily and knowingly accepts the terms 

of the contract.’ ” Id. (quoting Pennhurst, 451 U.S. at 17) 

(some internal quotation marks omitted). “Congress may use 

its spending power to create incentives for States to act in 

accordance with federal policies,” the Chief Justice concluded, 

“[b]ut when ‘pressure turns into compulsion,’ the legislation 

runs contrary to our system of federalism.” Id. (quoting 

Steward Mach. Co. v. Davis, 301 U.S. 548, 590 (1937)).21 

In NFIB, the Court struck down—as in excess of the 

Congress’ authority under the Spending Clause—a provision 

of the Affordable Care Act (ACA) that expanded the scope of 

the Medicaid program and increased the number of individuals 

the States had to cover. Although the Act increased federal 

funding to cover much of the States’ costs in expanding 

Medicaid coverage, it also provided that, if a State did not 

 21 As we discuss below, the Texas State Petitioners argue that 

the threat of highway sanctions makes the promulgation of SIP 

provisions for a nonattainment area effectively compulsory. They 

do not argue that the sanctions provision fails to comply with any 

other constitutional requirements governing conditions on federal 

grants to the States. See South Dakota v. Dole, 483 U.S. 203, 207–

08 (1987) (requiring that conditions promote the general welfare, be 

unambiguous, be related to the federal interest, and be consistent 

with other constitutional provisions). 
68

comply with the Act’s new coverage requirements, it could 

lose not only the new federal funding, but all of its existing 

federal Medicaid funds. NFIB, 132 S. Ct. at 2582. The Chief

Justice’s plurality opinion—for himself and Justices Breyer 

and Kagan—controls our decision on this issue.22

In addressing the question of overbearing financial 

coercion, the Chief Justice first discussed Dole, 483 U.S. 203, 

in which the Court rejected such a challenge. In that case, the 

Congress had threatened to withhold 5 per cent of a State’s 

federal highway funding unless the State raised its drinking age 

to 21. The Chief Justice noted that, although “the condition 

was ‘directly related to one of the main purposes for which 

highway funds are expended—safe interstate travel,’ ” it “was 

not a restriction on how the highway funds—set aside for 

specific highway improvement and maintenance efforts—were 

to be used.” NFIB, 132 S. Ct. at 2604 (quoting Dole, 483 U.S. 

at 208). “[A]ccordingly,” he said, the Dole Court “asked 

whether ‘the financial inducement offered by Congress’ was 

‘so coercive as to pass the point at which pressure turns into 

compulsion.’ ” Id. (quoting Dole, 483 U.S. at 211) (some 

internal quotation marks omitted). The Court answered that 

this monetary sanction was not impermissibly coercive, but 

rather offered only “relatively mild encouragement to the 

 22 When a majority of the Supreme Court agrees on a result, but 

“no single rationale explaining the result enjoys the assent of five 

Justices, ‘the holding of the Court may be viewed as that position 

taken by those Members who concurred in the judgments on the 

narrowest grounds . . . .’ ” Marks v. United States, 430 U.S. 188, 

193 (1977) (quoting Gregg v. Georgia, 428 U.S. 153, 169 n.15 

(1976) (plurality opinion)). The NFIB plurality found a Spending 

Clause violation on narrower grounds than did the joint opinion of 

Justices Scalia, Kennedy, Thomas, and Alito, NFIB, 132 S. Ct. at 

2656–69. See Mayhew v. Burwell, 772 F.3d 80, 88–89 (1st Cir. 

2014). It therefore controls here. Id.
69

states” because “all South Dakota would lose if she adheres to 

her chosen course as to a suitable minimum drinking age is 

5%” of her federal highway funds. Dole, 483 U.S. at 211; see 

NFIB, 132 S. Ct. at 2604. “In fact,” as the Chief Justice 

further noted in NFIB, “the federal funds at stake constituted 

less than half of one percent of South Dakota’s budget at the 

time.” NFIB, 132 S. Ct. at 2604.

In NFIB, the Chief Justice found that, as in Dole, the 

conditions the ACA imposed on the States did not “govern the 

use of” the new funds it granted to the States, but rather took 

“the form of threats to terminate other significant independent 

grants” already in existence. Id. Accordingly, he said, “the 

conditions are properly viewed as a means of pressuring the 

States to accept policy changes” and their level of coerciveness 

therefore had to be evaluated. Id. Upon doing so, the Chief 

Justice found the ACA’s financial sanction to be “a gun to the 

head,” in contrast to the “mild encouragement” in Dole. Id. 

A State that opted out of the ACA’s Medicaid expansion stood 

“to lose not merely ‘a relatively small percentage’ of its 

existing Medicaid funding, but all of it.” Id. (quoting Dole, 

483 U.S. at 211). That, the Chief Justice found, could amount 

to “over 10 percent of a State’s overall budget.” Id. at 2604–

05.

In the case now before us, the Congress has conditioned 

some federal highway funding on Texas’s adoption of an 

adequate implementation plan. This condition, like the one at 

issue in Dole, is—at least arguably—not a restriction on how 

the highway funds are to be used, but rather an incentive to 

encourage States to take action in a related policy area. But 

see discussion infra. Although as discussed below we are 

uncertain whether that alone is sufficient to trigger a 

coerciveness inquiry, we will proceed to evaluate the coercive 

effect of section 7509(b). For the following reasons, we find 
70

that the potential funding sanctions contained in section

7509(b) of the Clean Air Act are not nearly as coercive as those 

in the ACA. 

First, unlike the situation in NFIB and like that in Dole, a 

noncompliant State does not risk losing all federal funding for 

an existing program. To the contrary, the EPA Administrator 

can only prohibit funding for transportation projects or grants 

applicable to the nonattainment area. 42 U.S.C. 

§ 7509(b)(1)(A); 40 C.F.R. § 52.31(b)(3), (e)(2) (providing 

that the “highway funding sanction shall apply . . . only to . . . 

areas that are designated nonattainment”); see Virginia v. 

Browner, 80 F.3d 869, 881 (4th Cir. 1996) (“[A] state does not 

lose any highway funds that would be spent in areas of the state 

that are in attainment.”). Even within the nonattainment area, 

the Administrator may not prohibit the approval of projects or 

grants that the Secretary of Transportation determines are 

intended to resolve a demonstrated safety problem and will 

likely result in a reduction in accidents. 42 U.S.C. 

§ 7509(b)(1)(A). Indeed, the Secretary of Transportation may 

continue to approve a number of other kinds of projects and 

grants as well, including those that “would improve air 

quality.” Id. § 7509(b)(1)(B)(viii); see id. § 7509(b)(1)(B)(i)–

(viii). 

Second, the threatened loss of federal highway funding 

does not even approach the “over 10 percent of a State’s 

overall budget” at issue in NFIB. Texas advises us that it 

received more than $3 billion in federal highway and transit 

funds in 2013. State & County Br. 33 n.29. Even if all of 

that were withheld, it would still have amounted to less than 4 

per cent of the State’s 2013 budget.23 But as noted above, 

 23 See Nat’l Ass’n of State Budget Officers, The State 

Expenditure Report 2012–2014 8 (2014) (listing 2013 expenditures 
71

Texas does not stand to lose all of its highway funds. The

potential sanction applies, at most, to highway funds for 

projects in nonattainment areas. Wise County is the only 

county for which the petitioners make a Tenth Amendment 

argument, and because it is only one of 254 Texas counties, it 

is unlikely that the loss of even all of that county’s federal 

highway funds would put a serious dent in the State’s total 

budget.24 Moreover, as also noted above, it is unlikely that 

even that one county would lose all of its federal highway 

funding because the potential sanction does not extend to 

funding for a list of enumerated projects. See 42 U.S.C. 

§ 7509(b)(1)(A), (B)(i)–(viii). 

In short, it is clear that Texas does not risk losing 

anywhere near the percentage of its federal funding—either for 

the program at issue or of its overall budget—that the Court 

found fatal in NFIB. Precisely how much less, we do not 

know. But the burden of establishing unconstitutionality is on 

the challenger, and Texas has failed to provide the necessary 

information. That failure is further ground for rejecting the 

State’s constitutional challenge. See NFIB, 132 S. Ct. at 2662 

(joint opinion of Scalia, Kennedy, Thomas, and Alito, JJ.) 

 

as approximately $93 billion); Texas General Appropriations Act for 

the 2012–13 Biennium xi (2011), available at 

http://www.lbb.state.tx.us/Documents/GAA/General_Appropriation

s_Act_2012-13.pdf (appropriating approximately $79 billion for 

2013). 

24 Seventeen other Texas counties are also in nonattainment 

areas. See Final Dallas–Fort Worth Area Designations at 1; 

Houston-Galveston-Brazoria, Texas Final Area Designations for the 

2008 Ozone NAAQS at 1. But that is still only a small percentage 

of the State’s total of 254 counties. See also Envtl. Prot. Agency, 

Map of Texas 8-hour Ozone Nonattainment Areas (2008 Standard), 

available at http://www.epa.gov/oaqps001/ greenbk/tx8_2008.html.
72

(“[C]ourts should not conclude that legislation is 

unconstitutional on this ground unless the coercive nature of an 

offer is unmistakably clear.”); see also United States v. 

Morrison, 529 U.S. 598, 607 (2000) (requiring a “plain 

showing” of unconstitutionality); United States v. Bland, 472 

F.2d 1329, 1334 (D.C. Cir. 1972) (en banc) (noting that “the 

burden of establishing the unconstitutionality of a statute rests 

on him who assails it”).

Finally, although we have concluded that the highway 

sanction is not unconstitutionally coercive, we note some 

uncertainty as to whether a coerciveness inquiry was required. 

There are two circumstances that may distinguish this case 

from those in which the Supreme Court has found such an 

inquiry necessary.

First, as described in NFIB, the inquiry in Dole was 

triggered by the fact that the Congress had imposed a condition 

that did not restrict how the federal highway funds at issue 

were to be used. Here, by contrast, the condition and sanction 

do redirect the federal highway funds of non-complying states 

to programs of the Congress’ choosing, including those that 

“would improve air quality and would not encourage single 

occupancy vehicle capacity.” 42 U.S.C. 

§ 7509(b)(1)(B)(viii); see id. § 7509(b)(1)(B)(i)–(viii). As 

the Senate Committee Report on the 1990 Clean Air Act 

amendments explains, for nonattainment areas in States that 

fail to submit an adequate SIP, “Federal transportation 

investments” are “shifted to transportation programs that are 

designed to provide alternatives to the single occupancy 

vehicle and that contribute to reducing future [vehicle miles 

traveled].” S. REP. NO. 101-228, at 26 (1989). 

Second, the condition at issue in Dole—which required 

the States to raise their drinking age to 21—was also, at the 
73

time of South Dakota’s challenge, a new condition that had not 

been part of the original program. In NFIB, although the 

condition was a restriction on how Medicaid funds could be 

spent, Chief Justice Roberts found that the condition was also a 

new one. “Indeed,” he stressed, “the manner in which the 

expansion is structured indicates that while Congress may have 

styled the expansion a mere alteration of existing Medicaid, it 

recognized it was enlisting the States in a new health care 

program.” NFIB, 132 S. Ct. at 2606. This was important, he 

said, because “Spending Clause legislation [is] much in the 

nature of a contract,” id. at 2602 (internal quotation marks 

omitted), and “[t]hough Congress’ power to legislate under the 

spending power is broad, it does not include surprising 

participating States with post-acceptance or retroactive 

conditions,” id. at 2606 (internal quotation marks omitted). In 

both Dole and NFIB, the condition at issue was “new” in two 

senses of the word: Both conditions had been recently 

enacted at the time of the litigation, and both conditions 

imposed additional requirements with which States had to 

comply to continue receiving preexisting federal funding. 

Neither the Clean Air Act’s requirement to submit an 

implementation plan, nor its highway funds sanction, is a 

condition that has been newly imposed on the States. 

Although both were new in 1977, see Clean Air Act 

Amendments of 1977, Pub. L. No. 95-95, §§ 103, 176, 91 Stat. 

685, 687–88, 749–50 (1977), since then Texas has submitted 

implementation plans and accepted billions of dollars in 

highway funding. Accordingly, when the EPA issued the 

Wise County nonattainment designation in 2012, Texas was 

not suddenly surprised by dramatically new conditions 

retroactively imposed after a long period in which the State had 

accepted and relied upon unconditional federal funding—as 

was the case in NFIB. 
74

These differences from the Supreme Court’s precedents 

create some uncertainty as to whether the coerciveness inquiry 

employed in Dole and NFIB was even triggered by the Clean 

Air Act provisions at issue here. Even if it were, the fact that 

the State has long accepted billions of dollars notwithstanding 

the challenged conditions may be an additional relevant factor 

in the contract-like analysis the Court has in mind for assessing 

the constitutionality of Spending Clause legislation. But we 

need not resolve that uncertainty today. Because the 

challenged provisions of the Clean Air Act survive a 

coerciveness inquiry in any event, we reject the Texas State 

Petitioners’ challenge to their constitutionality.

ii. The Commerce Clause

The Texas State Petitioners also argue that the Wise 

County designation exceeds the scope of the Congress’ 

authority under the Commerce Clause. As explained above, 

supra § III.F.1, the designation declared that Wise County 

contributed enough ozone emissions to nearby violations of the 

NAAQS to warrant its own nonattainment designation. By 

virtue of that designation, sources of emissions within the 

county must comply with a variety of additional requirements. 

See, e.g., 42 U.S.C. § 7502(c)(1) (requiring the implementation 

of “all reasonably available control measures”); id.

§ 7502(c)(5) (requiring “permits for the construction and 

operation of new or modified major stationary sources 

anywhere in the nonattainment area”). 

The Commerce Clause grants the Congress the power 

“[t]o regulate Commerce . . . among the several States.” U.S. 

CONST., art. I, § 8, cl. 3. The Supreme Court has “recognized 

. . . that ‘[t]he power of Congress over interstate commerce is 

not confined to the regulation of commerce among the states,’ 

but extends to activities that ‘have a substantial effect on 
75

interstate commerce.’ ” NFIB, 132 S. Ct. at 2585–86 (opinion 

of Roberts, C.J.) (quoting United States v. Darby, 312 U.S. 

100, 118–19 (1941)); see United States v. Lopez, 514 U.S. 549, 

558–59 (1995). “Congress’s power, moreover, is not limited 

to regulation of an activity that by itself substantially affects 

interstate commerce, but also extends to activities that do so 

only when aggregated with similar activities of others.” 

NFIB, 132 S. Ct. at 2586 (opinion of Roberts, C.J.) (citing 

Wickard v. Filburn, 317 U.S. 111, 127–28 (1942)). The 

question for a court is whether there was a “rational basis” for 

the Congress’ conclusion that a regulated activity substantially 

affects interstate commerce. Hodel v. Indiana, 452 U.S. 314, 

323–24 (1981); see Nat’l Ass’n of Home Builders v. Babbitt

(NAHB), 130 F.3d 1041, 1051 (D.C. Cir. 1997) (opinion of 

Wald, J.). 

The Texas State Petitioners’ first contention is that the 

NOx emissions produced by oil and gas activity in the Barnett 

Shale in Wise County do not “ ‘substantially affect’ interstate 

commerce,” principally because the emissions are “wholly 

intrastate.” State & County Br. 36. That premise is 

unsupported by any proffered evidence and is factually 

incorrect. The phenomenon of interstate transport of ozone 

has been thoroughly studied, and it has been recognized by the 

Congress, the EPA, the Supreme Court, and this Court.

25 The 

 25 See 42 U.S.C. §§ 7410(a)(2)(D), 7511c (Clean Air Act 

provisions addressing interstate transport of ozone); S. REP.

NO. 101-228, at 34 (1989) (discussing Clean Air Act amendments 

designed to “[c]ontrol . . . interstate ozone pollution”); id. at 13 

(noting that “ozone is not a local phenomenon but is formed and 

transported over hundreds of miles and several days”); 2008 

Designations Rule, 77 Fed. Reg. at 30,089 (finding that ozone and 

ozone precursors travel easily through the atmosphere, which can 

result in NAAQS violations hundreds of miles from the precursors’ 

source); EME Homer City Generation, L.P., 134 S. Ct. at 1594 
76

“winds, of course, recognize no [state] boundaries.” United 

States v. Ford Motor Co., 814 F.2d 1099, 1102 (6th Cir. 1987).

But even if the particular emissions from the Barnett Shale 

stopped at the Texas state line, the regulation of their sources 

would still be permissible under the Commerce Clause for two 

reasons. First, “where a general regulatory statute bears a 

substantial relation to commerce, the de minimis character of 

individual instances arising under that statute is of no 

consequence.” Lopez, 514 U.S. at 558 (internal quotation 

marks omitted) (emphasis omitted); see Gonzales v. Raich, 545 

U.S. 1, 17 (2005); NAHB, 130 F.3d at 1046 (opinion of Wald, 

J.). And there is no doubt that the general regulatory scheme 

of the Clean Air Act has a substantial relation to interstate 

commerce. Indeed, the same is true even if we focus only 

upon the Act’s generally applicable ozone provisions.

Moreover, we can find a substantial effect not only by 

examining the emissions that are produced, but also by 

examining the activities that the challenged statute regulates to 

reduce the production of those emissions. See Rancho Viejo, 

LLC v. Norton, 323 F.3d 1062, 1067 (D.C. Cir. 2003); NAHB, 

130 F.3d at 1046 & n.3 (opinion of Wald, J.); id. at 1058 

(Henderson, J., concurring). As we explained in Rancho 

Viejo, on this rationale we “focus[] on the activity that the 

federal government seeks to regulate.” 323 F.3d at 1069; see 

Morrison, 529 U.S. at 609 (instructing that “the proper 

inquiry” is whether the challenge is to “a regulation of activity

that substantially affects interstate commerce”) (emphasis 

 

(detailing the “journey” taken by ozone precursors, which “often 

develop into ozone . . . by the time they reach the atmospheres of 

downwind States”); Virginia v. EPA, 108 F.3d 1397, 1400 (D.C. Cir. 

1997) (describing the “ozone transport phenomenon” in the lower 

atmosphere). 
77

added); Lopez, 514 U.S. at 558–59 (“Congress’ commerce 

authority includes the power to regulate . . . those activities that 

substantially affect interstate commerce.”) (emphasis added). 

In Rancho Viejo, we upheld the constitutionality of the Fish 

and Wildlife Service’s decision to protect an endangered toad 

species by regulating a housing development, on the ground 

that the regulated activity, a “202-acre project, located near a 

major interstate highway, [was] . . . presumably being 

constructed using materials and people from outside the state.” 

323 F.3d at 1069 (internal quotation marks omitted). 

Likewise, in NAHB, we upheld the Service’s decision to 

protect an endangered fly species by regulating the 

construction plan for a hospital, on the ground that the 

commercial land development at issue “ha[d] a plain and 

substantial effect on interstate commerce.” 130 F.3d at 1059 

(Henderson, J., concurring); see id. at 1056 (opinion of Wald, 

J.).

Here, the activities that the EPA seeks to regulate are the 

commercial, industrial, and extraction processes that produce 

the emissions at issue. See 42 U.S.C. § 7511a; 2008 

Designations Rule, 77 Fed. Reg. at 30,089. The 

nonattainment designation triggers regulatory controls on the 

sources of those emissions, many of which are indisputably 

entities engaged in substantial interstate commerce. In the 

case of Wise County in particular, those entities include 

multinational companies engaged in the production and sale of 

oil and gas from the Barnett Shale, including several of the 

Industrial Petitioners here.26 The restrictions triggered by the 

 26 Industrial Petitioner Devon Energy Corporation, for example, 

“is a leading independent oil and natural gas exploration and 

production company,” with operations “focused onshore in the 

United States and Canada.” Industrial Br. iv. “Devon is also one 

of North America’s larger processors of natural gas liquids, with . . . 

natural gas processing facilities in many of its producing areas, 
78

nonattainment designation thus affect the conditions under 

which interstate commerce in oil and gas may proceed. And 

as such, the designation process “regulates and substantially 

affects commercial . . . activity which is plainly interstate.” 

NAHB, 130 F.3d at 1058 (Henderson, J., concurring).

The Texas State Petitioners’ second contention is that, 

“[e]ven if incidental emissions do ‘substantially affect’ 

interstate commerce, they are not ‘quintessentially economic 

activity’ ” and cannot be regulated under the Commerce 

Clause. State & County Br. 36. This contention is based on 

the Court’s decision in Lopez, which held the Gun-Free School 

Zones Act unconstitutional in part because the statutory 

provision at issue, which criminalized the possession of a gun 

in a school zone, had “nothing to do with ‘commerce’ or any 

sort of economic enterprise, however broadly one might define 

those terms.” Lopez, 514 U.S. at 560–61; see also Morrison, 

529 U.S. at 610–11, 613. There are two answers to this 

contention.

First, ozone pollution itself has economic consequences 

for interstate commerce. The Congress so found in the course 

of amending the Clean Air Act. See S. REP. NO. 101-228, at 8 

(1989) (noting that exposure to air pollution costs the United 

States $40 billion annually in additional health care costs, and 

documenting health effects of ozone and other pollutants); id. 

(noting that “ozone causes annual crop losses of $2 to $3 

billion per year”). Although we are not bound by 

congressional findings, they may assist us in “evaluat[ing] the 

legislative judgment that the activity in question substantially 

 

including Wise County, Texas.” Id.; see id. at 13 (“Industrial 

Petitioners and members with operations in Wise County were 

immediately subjected to increased regulatory burdens due to the 

nonattainment designation.”). 
79

affected interstate commerce.” Lopez, 514 U.S. at 562–63; 

see Rancho Viejo, 323 F.3d at 1069. Indeed, we have 

previously credited the Congress’ findings regarding ozone 

pollution, concluding that the Act’s “legislative history and 

EPA’s report to Congress substantiate the heavy impact ozone 

pollution has on national health care costs and national 

agricultural production.” Allied Local, 215 F.3d at 83. 

Second, the activities that are ultimately regulated by the 

designation process are not the ozone precursor “emissions,” 

but rather the activities that produce the emissions. Those 

include the operation of power plants, gas processors, and 

vehicles that produce the emissions. See 42 U.S.C. § 7511a. 

As we explained in Rancho Viejo, the regulated activity in that 

case was a company’s “planned commercial development, not 

the arroyo toad that it threaten[ed].” 323 F.3d at 1072. The 

same point is true here. Just as the Endangered Species Act 

“does not purport to tell toads what they may or may not do,” 

id., the Clean Air Act does not tell NOx or VOCs what to do. 

Rather, it tells the commercial and industrial sources that 

produce those compounds what they may do.

As we noted in Allied Local, the Supreme Court has long 

made clear that “ ‘the power conferred by the Commerce 

Clause [is] broad enough to permit congressional regulation of 

activities causing air or water pollution, or other environmental 

hazards that may have effects in more than one State.’ ” 

Allied Local, 215 F.3d at 83 (quoting Va. Surface Mining & 

Reclamation Ass’n, 452 U.S. at 282) (emphasis added); id. 

(noting that the Supreme Court cited Virginia Surface Mining 

and Reclamation Association with approval in both Lopez and 

Morrison). “[B]ecause we are required to accord 

congressional legislation a ‘presumption of 

constitutionality,’ ” Rancho Viejo, 323 F.3d at 1069 (quoting 

Morrison, 529 U.S. at 607), the petitioners’ inability to 
80

establish that emissions-producing sources in the State do not 

substantially affect interstate commerce “is fatal to [their] 

cause,” id.; see Morrison, 529 U.S. at 607 (“Due respect for the 

decisions of a coordinate branch of Government demands that 

we invalidate a congressional enactment only upon a plain 

showing that Congress has exceeded its constitutional 

bounds.”). The regulation of the sources of Wise County 

emissions through the Clean Air Act’s designation process lies 

well within the Congress’ authority to regulate interstate 

commerce. 

iii. The Due Process Clause

The Texas State Petitioners’ third constitutional challenge 

maintains that the EPA’s designation of Wise County violated 

the Due Process Clause because the former Administrator of 

EPA Region 6, Al Armendariz, failed to disqualify himself 

from the proceedings. 

According to the petitioners, Armendariz should have 

disqualified himself for four reasons. First, Armendariz has a 

history of working for environmental advocacy groups. 

Second, a report he authored as an advocate before joining the 

EPA concluded that emissions from the Barnett Shale were 

contributing significantly to local and global pollution. Third, 

a speech Armendariz gave after joining the EPA analogized his 

aggressive enforcement policy against oil and gas companies 

that “are not complying with the law” to the way “Romans 

used to conquer those villages in the Mediterranean” by 

“crucify[ing]” the first people they saw. Terrence Henry, 

Texas EPA Official Apologizes for ‘Crucify Them’ Comments, 

Apr. 26, 2012, State Impact NPR, 

http://stateimpact.npr.org/texas/2012/04/26/epa-official-apolo

gizes-for-crucify-comments (quoting Armendariz). “You 

make examples out of people who . . . are not complying with 
81

the law,” Armendariz said. “There’s a deterrent 

factor. . . . And they decide at that point that it’s time to clean 

up.” Id.27 Finally, in the petitioners’ view, “[n]ormally, the 

prevailing wind direction and EPA-standard modeling would 

have led EPA to accept” Texas’s designation of Wise County 

as attainment. State & County Br. 38. All of this, the 

petitioners argue, “create[s] a presumption that the Agency’s 

mind was closed and it was unwilling or unable to rationally 

consider arguments against nonattainment.” Id. at 37.

In Air Transport Association of America, Inc. v. National 

Mediation Board, 663 F.3d 476 (D.C. Cir. 2011), we repeated 

this circuit’s approach to the kind of claim that the petitioners 

raise here. “Decisionmakers violate the Due Process Clause 

and must be disqualified,” we said, “when they act with an 

‘unalterably closed mind’ and are ‘unwilling or unable’ to 

rationally consider arguments.” Id. at 487 (quoting Ass’n of 

Nat’l Advertisers, Inc. v. FTC, 627 F.2d 1151, 1170, 1174 

(D.C. Cir. 1979)). “[A]n individual should be disqualified 

from rulemaking only when there has been a clear and 

convincing showing that the . . . member has an unalterably 

closed mind on matters critical to the disposition of the 

proceeding.” Id. (quoting C & W Fish Co., Inc. v. Fox, 931 

F.2d 1556, 1564 (D.C. Cir. 1991) (internal quotation marks 

omitted)). The four arguments advanced by the Texas State 

Petitioners are insufficient to make that “clear and convincing” 

showing.28

 27 After a video of the speech was discovered, Armendariz 

resigned. Id. Soon thereafter, the EPA promulgated the Wise 

County nonattainment designation.

28 The Supreme Court has held that States are not “persons” 

within the meaning of the Due Process Clause. See South Carolina 

v. Katzenbach, 383 U.S. 301, 323–24 (1966); see also Republic of 
82

Our decision in C & W Fish Company establishes that 

neither Armendariz’ employment history nor the report he 

authored before joining the EPA required his disqualification. 

There, we considered the impartiality of an agency 

administrator who had previously served as the chairman of a 

group advocating for the precise agency policy at issue in the 

case, and who after his appointment remarked that there was 

“no question” that the policy should be implemented. C & W 

Fish Co., 931 F.2d at 1564. Those circumstances, we said, did 

“not even approach a ‘clear and convincing showing’ that [the 

administrator] had an ‘unalterably closed mind.’ ” Id. at 

1565. 

The petitioners’ third argument is also unpersuasive. 

There is no doubt that Armendariz’ “crucifixion” comments 

were offensive. But that does not suffice to make the requisite 

showing. The comments described Armendariz’ general 

approach to enforcement, but were neither specifically about 

the designation process nor specifically targeted at production 

from the Barnett Shale. Accordingly, they did not reveal 

Armendariz’ views on “matters critical to the disposition of the 

proceeding.” Ass’n of Nat’l Advertisers, 627 F.2d at 1170. 

And even if they had, they would not alone demonstrate an 

unalterably closed mind on the subject. See C & W Fish Co., 

931 F.2d at 1565 (“ ‘We would eviscerate the proper evolution 

of policymaking were we to disqualify every administrator 

who has opinions on the correct course of his agency’s future 

 

Argentina v. Weltover, Inc., 504 U.S. 607, 619 (1992) (citing

Katzenbach, 383 U.S. at 323–24); Price v. Socialist People’s Libyan 

Arab Jamahiriya, 294 F.3d 82, 96 (D.C. Cir. 2002). Although one 

circuit has held that counties are protected in some circumstances, 

see County of Santa Cruz v. Sebelius, 399 F. App’x 174, 176 (9th 

Cir. 2010), we need not consider the issue because we find no 

violation here.
83

actions.’ ” (quoting Ass’n of Nat’l Advertisers, 627 F.2d at 

1174)).

Finally, we cannot infer bias from the fact that, in the 

opinion of the petitioners, the computer modeling supported an 

attainment designation for Wise County. As we held in C & 

W Fish Company, “we reject the suggestion that we look to the 

adequacy of [an agency official’s] examination of the facts and 

issues in order to determine whether he was biased.” 931 F.2d 

at 1564. Rather, “[w]hether [the official] weighed the facts 

properly is to be examined only in determining if his decision 

was arbitrary or capricious.” Id. at 1564–65. And that is an 

examination that we separately undertake in section III.F.2,

supra.

For the foregoing reasons, we reject the petitioners’ three 

constitutional challenges to the designation of Wise County as 

a nonattainment area.

4. The Remaining Challenges

Finally, the Texas State Petitioners argue that we should 

vacate the EPA’s Wise County nonattainment designation 

because the EPA (1) failed to comply with the Information 

Quality Act, (2) failed to promulgate regulations defining the 

terms “necessary” and “contribute,” (3) concluded that Wise 

County emissions “can” contribute to NAAQS violations when 

it was statutorily required to conclude that Wise County “did” 

contribute, and (4) failed to give them “fair notice” of the 

EPA’s requirements. State & County Br. 46–52. We reject 

all four contentions. 

First, the Texas State Petitioners urge us to conclude that 

the Information Quality Act requires the EPA to use “the best 

available science and supporting studies conducted in 

accordance with sound and objective scientific practices” in 
84

making NAAQS designations, State & County Br. 46 (citing 

Prime Time Int’l Co. v. Vilsack, 599 F.3d 678, 685–86 (D.C. 

Cir. 2010)), and that the EPA failed to do so here. But almost 

every court that has addressed an Information Quality Act 

challenge has held that the statute “creates no legal rights in 

any third parties,” Salt Inst. v. Leavitt, 440 F.3d 156, 159 (4th 

Cir. 2006);29 see also Harkonen v. U.S. Dep’t of Justice, No. C 

12-629 CW, 2012 WL 6019571, at *11 (N.D. Cal. Dec. 3, 

2012) (collecting cases). And this Court has held that the 

Information Quality Act is not “an independent measure of 

EPA’s NAAQS decision.” Mississippi, 744 F.3d at 1347. 

The purpose of the Information Quality Act is to “ensur[e] and 

maximize[e] the quality, objectivity, utility, and integrity of 

information (including statistical information) disseminated by 

Federal agencies” and does not constitute a statutory 

mechanism by which the EPA’s conclusions reached while 

making its nonattainment determinations can be challenged. 

See 44 U.S.C. § 3516 note (emphasis added). 

Second, the Texas State Petitioners argue that the EPA 

should define the terms “contribute” and “necessary” through 

administrative rulemaking in order to rein in the “boundless 

override discretion” it uses to “commandeer[]” states to 

“enforce its massive regulatory scheme.” See State & County 

Br. 48. Our Catawba County holding forecloses this 

argument. There, we held that the EPA was “free to adopt a 

totality-of-the-circumstances test to implement a statute that 

confers broad discretionary authority.” Catawba Cnty., 571 

F.3d at 39. Finally, the Texas State Petitioners offer no reason 

why the word “necessary,” which the EPA reasonably 

 29 But see Prime Time, 599 F.3d at 685–86 (affirming dismissal 

of Information Quality Act challenge on different grounds without 

addressing argument that the statute creates no legal rights in third 

parties). 
85

interpreted as authorizing modification of a state’s 

recommended designation that does “not meet the statutory 

requirements or [was] otherwise inconsistent with the facts or 

analysis deemed appropriate by the EPA,” see 2008 

Designations Rule, 77 Fed. Reg. at 30,090, must be defined via 

rulemaking.

Third, the Texas State Petitioners argue that the EPA 

exceeded its authority under the Clean Air Act because it 

concluded that Wise County emissions “can” contribute to 

NAAQS violations, whereas the Act authorizes a finding that 

Wise County “does” so contribute. See State & County Br.

50. This argument is premised on the EPA’s response to a 

petition for reconsideration challenging the Wise County 

nonattainment designation, to which the EPA responded that 

“the Wise County emissions are large enough that they can

contribute to ozone exceedances on certain days.” EPA 

Response to Pet. for Reconsideration from Wise Cnty., Office 

of the Cnty Judge at 2 (emphasis added). But read in toto, the 

EPA’s justification for including Wise County in the Dallas–

Fort Worth nonattainment area was anything but theoretical: 

Wise County [h]as 2008 NEI emissions of 

11,911 tons of NOx and 17,609 tons of VOC; 

there are 60 people per square mile; has a 2010 

population of 59,127 with a growth rate of 5.9 

percent between 2000 and 2010; total VMT is 

969 million. The close proximity of these 

comparatively high emissions to violating 

monitors indicates that this county should be 

included in the nonattainment area. The high 

growth in these emissions is due in large part to 

growth in emissions from Barnett Shale gas 

production development, but also due to 

growth in population. Examination of back 
86

trajectories indicates that at times emissions 

from Wise County contribute to observed 

violations in the area and also to observed 

violations that have helped set the DFW area 

DV in the past. Source apportionment 

modeling for a portion of an ozone season 

indicates that emissions from Wise County can 

contribute to observed violations in the DFW 

nonattainment area. These factors support the 

inclusion of Wise County in the nonattainment 

area.

Final Dallas–Fort Worth Area Designations at 23. Read in 

context, we conclude that the EPA in fact found that Wise 

County does contribute to NAAQS violations in the Dallas–

Fort Worth area. 

Fourth, the Texas State Petitioners argue the EPA failed to 

provide them with “fair notice” of its requirements. Even 

assuming the fair notice doctrine applies, cf. Ark. Dep’t of 

Human Servs. v. Sebelius, 818 F. Supp. 2d 107, 120–21 

(D.D.C. 2011), the EPA did not violate it. The fair notice 

doctrine, which is couched in terms of due process, provides 

redress only if an agency’s interpretation is “so far from a 

reasonable person’s understanding of the regulations that they 

could not have fairly informed the regulated party of the

agency’s perspective.” United States v. Chrysler Corp., 158 

F.3d 1350, 1354 (D.C. Cir. 1998) (alteration omitted). Here, 

the EPA not only provided the 2008 Guidance to aid the states 

in making their initial designations, it also provided a 

preliminary technical support document to each state before 

finalizing any of its proposed modifications to the state’s initial 

designations. See, e.g., Preliminary Dallas–Fort Worth Area 

Designations. The technical support document, in turn, gave

each state a precise explication of all proposed EPA 
87

modifications as a roadmap to use during the 120-day 

comment period. Simply put, the EPA set forth its analysis, 

provided an opportunity to rebut its conclusions and ultimately 

explained why it had not changed its mind. Accordingly, the 

Texas State Petitioners’ fair notice doctrine argument is 

meritless. 

For the foregoing reasons, the consolidated petitions for 

review are denied.

So ordered.