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United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued October 12, 2006 Decided December 22, 2006

No. 04-1200

SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT,

PETITIONER

v.

ENVIRONMENTAL PROTECTION AGENCY,

RESPONDENT

NATIONAL ENVIRONMENTAL DEVELOPMENT ASSOCIATION’S

CLEAN AIR REGULATORY PROJECT, ET AL.,

INTERVENORS

Consolidated with

No. 04-1201, et al.

On Petitions for Review of a Final Rule of the

Environmental Protection Agency

David S. Baron argued the cause for the Environmental

petitioners and South Coast Air Quality Management District.
2

With him on the briefs were Howard I. Fox, Ann B. Weeks,

Jonathan F. Lewis, Barbara B. Baird, and Adam Babich. Kurt

R. Wiese entered an appearance.

William L. Pardee, Assistant Attorney General, Attorney

General’s Office of Commonwealth of Massachusetts, argued

the cause for petitioner Commonwealth of Massachusetts, et al.

With him on the briefs were Thomas F. Reilly, Attorney

General; Richard Blumenthal, Attorney General, Attorney

General’s Office of the State of Connecticut, Kimberly

Massicotte and Matthew Levine, Assistant Attorneys General;

Carl Danbert, Attorney General, Attorney General’s Office of

the State of Delaware, Valerie S. Csizmadia, Deputy Attorney

General; G. Steven Rowe, Attorney General, Attorney General’s

Office of the State of Maine, Gerald D. Reid, Assistant Attorney

General; Robert J. Spagnoletti, Attorney General, Attorney

General’s Office of the District of Columbia, Todd S. Kim,

Solicitor General, Edward S. Schwab, Deputy Attorney General,

Donna M. Murasky, Senior Litigation Counsel; Eliot Spitzer,

Attorney General, Attorney General’s Office of the State of New

York, J. Jared Snyder, David A. Munro, and Lisa S. King,

Assistant Attorneys General; and Robert A. Reiley, Counsel,

Commonwealth of Pennsylvania, Department of Environmental

Protection.

John K. McManus, Assistant Attorney General, Attorney

General’s Office of State of Ohio, argued the cause for

petitioner State of Ohio. With him on the briefs was Dale T.

Vitale, Assistant Attorney General.

Frank S. Craig, III argued the cause for the Industry

petitioners. With him on the briefs were Charles H. Knauss,

Robert V. Zener, John B. King, Steven J. Levine, and Patrick

O’Hara. 
3

David J. Kaplan, Attorney, U.S. Department of Justice,

argued the cause for respondent. With him on the brief were

John C. Cruden, Assistant Attorney General, Natalia T.

Sorgente, Attorney, and Jan M. Tierney, Attorney, U.S.

Environmental Protection Agency. Eric G. Hostetler, Attorney,

U.S. Department of Justice, entered an appearance.

David S. Baron and Howard I. Fox were on the brief of the

Environmental intervenors.

Charles H. Knauss, Leslie S. Ritts, Lorane F. Hebert,

Norman W. Fichthorn, Lucinda Minton Langworthy, Allison D.

Wood, Leslie A. Hulse, Richard S. Wasserstrom, Maurice H.

McBride, Ralph J. Colleli, M. Elizabeth Cox, Jan S. Amundson,

and Quentin Riegel were on the brief of the Industry intervenors

in support of Respondent. 

Frank S. Craig, III, John B. King, Geraldine E. Edens, and

Frederick R. Anderson were on the brief of amici curiae The

Chamber of Greater Baton Rouge, et al. in support of

Respondent.

Before: HENDERSON, ROGERS and BROWN, Circuit Judges.

Opinion for the Court filed by Circuit Judge ROGERS.

ROGERS, Circuit Judge: This case consolidates challenges

to the Final Phase 1 Rule To Implement the 8-Hour Ozone

National Ambient Air Quality Standard, 69 Fed. Reg. 23,951

(Apr. 30, 2004) (codified at 40 C.F.R. parts 40, 51, 81)

(hereinafter “2004 Rule”), promulgated by the Environmental

Protection Agency pursuant to the Clean Air Act (“CAA” or

“the Act”), 42 U.S.C. § 7401 et seq. Because EPA has failed to

heed the restrictions on its discretion set forth in the Act, we

grant the petitions in part, vacate the rule, and remand the matter
4

to EPA for further proceedings.

I.

The earliest clean air laws date back to the nineteenth

century, when industrial cities sought to reduce smoke

emissions. See GARY C.BRYNER,BLUE SKIES,GREEN POLITICS:

THE CLEAN AIR ACT OF 1990 AND ITS IMPLEMENTATION 98 (2d

ed. 1995). It was not until much later that the federal

government became involved. The first Clean Air Act was

passed in 1963, see Pub. L. No. 88-206, 77 Stat. 392 (1963), but

this effort, supplying little more than research funding, bore

little resemblance to the comprehensive scheme that Congress

would later impose.

The Clear Air Act Amendments of 1970 introduced the

now-familiar arrangement of state-federal cooperation. See

Clean Air Act Amendments of 1970, Pub. L. No. 91-604, 84

Stat. 1676 (1970). EPA was to prescribe a primary national

ambient air quality standard (“NAAQS”) for airborne pollutants

that was “requisite to protect the public health.” Id. § 4(a), 84

Stat. at 1678-80 (codified at 42 U.S.C. § 7409). The NAAQS

was to be attained by a state implementation plan (“SIP”),

developed by the state and approved by EPA, that introduced

sufficient pollution control techniques so as to reach attainment

by 1975, with the possibility of a one-time extension of two

more years. Id. § 4(a), 84 Stat. at 1680-82 (codified at 42 U.S.C.

§ 7410 (amended 1977)). This approach, which applied

identically to all “criteria” pollutants, proved overly ambitious.

Congress amended the Act in 1977, extending the attainment

deadlines until December 31, 1987. Pub. L. No. 95-95, §

129(b), 91 Stat. 685, 746-47 (codified at 42 U.S.C. § 7502(a)(2)

(amended 1990)).

With the new deadline approaching and penalties looming
5

for states yet to attain, Congress stepped in again. By this time,

Congress was considering new approaches to deal with unclean

air. See Henry A. Waxman, An Overview of the Clean Air Act

Amendments of 1990, 21 ENVTL. L. 1721, 1731-33 (1991)

(hereinafter “Overview”). The existing approach, which

specified the ends to be achieved but left broad discretion as to

the means, had done little to reduce the dangers of key

contaminants. For example, Don Theiler, Director of the

Wisconsin Bureau of Air Management, appearing on behalf of

two national associations of state-and-local air-control agencies,

testified that between August 1987 and February 1989, the

number of areas violating the ozone NAAQS had increased,

from seventy to ninety, exposing as many as 95 million people

to unhealthy levels of ozone. See Clean Air Act Standards:

Hearing Before the Subcomm. on Health and the Environment

of the H. Comm. on Energy and Commerce, 101st Cong. 30

(1989). In light of such failures, Congress culminated nearly ten

years of hearings and debates by enacting the 1990 Amendments

to the Act. Pub. L. No. 101-549, 104 Stat. 2399 (Nov. 15,

1990). This version of the Act provides the backdrop for the

petitions before the court.

The 1990 Amendments abandoned the discretion-filled

approach of two decades prior in favor of more comprehensive

regulation of six pollutants that Congress found to be

particularly injurious to public health: ozone, carbon monoxide,

small particulate matter, sulfur dioxide, nitrogen dioxide, and

lead. See CAA §§ 181-192, 42 U.S.C. §§ 7511-7514a. The old

ends-driven approach that had proven unsuccessful for these

pollutants was redesignated Subpart 1 (of Part D of Title I),

which Congress instructed “shall not apply with respect to

nonattainment areas for which attainment dates are specifically

provided under other provisions of this part.” CAA §

172(a)(2)(D), 42 U.S.C. § 7502(a)(2)(D). In place of Subpart 1,

Congress enacted Subpart 2 to deal with the specific problem of
6

ozone. See CAA §§ 181-185B, 42 U.S.C. §§ 7511-7511f.

Ozone, an essential presence in the atmosphere’s stratospheric

layer, is dangerous at ground level. There, ozone is formed by

the chemical reaction of nitrogen oxides (“NOx”) with any of a

number of volatile organic compounds (“VOCs”), in the

presence of sunlight. See West Virginia v. EPA, 362 F.3d 861,

865 (D.C. Cir. 2004). Ground-level ozone is a key component

of urban smog and exposure to high concentrations “can cause

lung dysfunction, coughing, wheezing, shortness of breath,

nausea, respiratory infection, and in some cases, permanent

scarring of the lung tissue.” Overview, supra, at 1758; see S.

REP. NO. 101-228, at 6 (1989), reprinted in 5 COMM. ON ENV’T

& PUB. WORKS, U.S. SENATE, A LEGISLATIVE HISTORY OF THE

CLEAN AIR ACT AMENDMENTS OF 1990, at 8338, 8346

(hereinafter “LEGISLATIVE HISTORY”).

No longer willing to rely upon EPA’s exercise of discretion,

Congress adopted a graduated classification scheme that

prescribed mandatory controls that each state must incorporate

into its SIP. Thus, as of the date of enactment of the 1990

Amendments, areas failing to reach attainment under the

NAAQS would become, upon such designation by EPA, subject

to Subpart 2 requirements by operation of law. See CAA §

181(a)(1), 42 U.S.C. § 7511(a)(1). Under Subpart 2, each area

was to be classified according to its design value—the measured

concentration of ground-level ozone. The statutory Table 1

provided that areas were to be classified as Marginal, Moderate,

Serious, Severe, or Extreme depending upon how much the

design value exceeded the NAAQS at the time of designation.

CAA § 181(a) tbl.1, 42 U.S.C. § 7511(a) tbl.1. Areas with

greater problems were given more time to attain the NAAQS but

a harsher set of mandatory controls, including provisions for

demonstrations of reasonable further progress, NOx control,

motor vehicle emissions control, and new source review. See

CAA § 182, 42 U.S.C. § 7511a. Areas that failed to meet a
7

deadline were to be reclassified to a higher classification

automatically, thereby according more time to comply with the

NAAQS while subjecting that area to more stringent mandatory

controls. CAA § 181(b)(2), 42 U.S.C. § 7511(b)(2). This

protocol was prescribed whether or not that area was closer to

attainment when it missed the deadline than when it was

originally classified. For Severe and Extreme areas that still had

not reached attainment by November 15, 2005 or 2010,

respectively, the Act called for the imposition of penalties to

provide incentives for major polluters to reduce VOC emissions.

See CAA § 185, 42 U.S.C. § 7511d. Under the 1990

Amendments, the NAAQS stood at 0.12 parts per million

(“ppm”), measured as the maximum average concentration for

a one-hour period during a calendar year. See 40 C.F.R. §

50.9(a) & app. H. This regulatory scheme remained in place

until 1997.

Although Subpart 2 of the Act and its Table 1 rely upon the

then-existing NAAQS of 0.12 ppm, measured over a one-hour

period, elsewhere the Act contemplates that EPA could change

the NAAQS based upon its periodic review of “the latest

scientific knowledge useful in indicating the kind and extent of

all identifiable effects on public health” that the pollutant may

cause. CAA §§ 108(a), 109(d), 42 U.S.C. §§ 7408(a), 7409(d).

The Act provides that EPA may relax a NAAQS, but in so

doing, EPA must “provide for controls which are not less

stringent than the controls applicable to areas designated

nonattainment before such relaxation.” CAA § 172(e), 42

U.S.C. § 7502(e). This provision protects against backsliding.

In 1997, citing a new scientific understanding that

prolonged ozone exposure was more harmful to public health

than the short-term exposure then regulated, EPA promulgated

a rule setting a new NAAQS for ambient ozone. See NAAQS

for Ozone, 62 Fed. Reg. 38,856 (July 18, 1997) (codified at 40
8

1 Chevron U.S.A. Inc. v. Natural Res. Def. Council, Inc., 467

U.S. 837, 842-43 (1984) (employing two-step analysis).

C.F.R. §§ 50.9, 50.10) (hereinafter “1997 Rule”). The new

NAAQS replaced the one-hour, 0.12 ppm standard with an

eight-hour, 0.08 ppm standard, now measured as the fourthhighest daily level in a calendar year. Id. The new standard

thus both changed the measuring scheme and was marginally

more stringent, as EPA recognized that an eight-hour level of

0.09 ppm would have “generally represent[ed] the continuation

of the present level of protection.” Id. at 38,858. Alongside its

revised standard, EPA also announced an implementation

“guidance” indicating its intention to phase out the one-hour

standard only after “EPA determines that the area has air quality

meeting the 1-hour standard,” id. at 38,894 (codified at 40

C.F.R. § 50.9(b)), while implementing the eight-hour standard

under the generic Subpart 1 of the Act, id. at 38,873.

On petitions for review, this court held, in relevant part, that

under Chevron1

 Step 1 EPA could not use the discretion-filled

Subpart 1. Congress had expressed its clear intent that the

mandatory control scheme it set forth in Subpart 2 was to be

used to regulate ozone. Am. Trucking Ass’ns v. EPA, 175 F.3d

1027, amended on reh’g, 195 F.3d 4 (D.C. Cir. 1999). On

certiorari, the Supreme Court agreed that Subpart 2

“unquestionably” “provide[s] for classifying nonattainment

ozone areas under the revised standard,” but disagreed that the

case could be resolved exclusively under Chevron Step 1.

Whitman v. Am. Trucking Ass’ns, 531 U.S. 457, 482-86 (2001).

Instead, the Court recognized that 

to the extent that the new ozone standard is stricter

than the old one, the classification system of Subpart 2

contains a gap, because it fails to classify areas whose

ozone levels are greater than the new standard (and
9

thus nonattaining) but less than the approximation of

the old standard codified by Table 1.

Id. at 483 (citations omitted). In addition to this classification

gap, the Court also found a measurement gap and a timing gap:

the one-hour averages could not well be used to evaluate eighthour ozone concentrations and the deadlines set forth in Table

1 would “make no sense for areas that are first classified under

a new standard after November 15, 1990.” Id. at 483-84. The

Court therefore indicated that “[t]hese gaps in Subpart 2’s

scheme prevent us from concluding that Congress clearly

intended Subpart 2 to be the exclusive, permanent means of

enforcing a revised ozone standard in nonattainment areas.” Id.

at 484. Thus, it “would defer to the EPA’s reasonable resolution

of that ambiguity” under Chevron Step 2. Id.

While recognizing the existence of these gaps, the Supreme

Court was careful to emphasize their narrow scope. EPA was

not “to render Subpart 2’s carefully designed restrictions on

EPA discretion utterly nugatory,” nor could it “construe the

statute in a way that completely nullifies textually applicable

provisions meant to limit its discretion.” Id. at 484-85. Because

“Subpart 2 was obviously written to govern implementation for

some time,” EPA’s 1997 approach, leaving Subpart 2 “abruptly

obsolete,” was “astonishing.” Id. at 485. Thus, while EPA was

invited to exercise its discretion as to the relationship between

Subparts 1 and 2, the Court instructed that the range of

reasonable interpretations was constrained.

In 2003, with the eight-hour NAAQS still awaiting

implementation by EPA, several environmental groups sued

seeking adherence by EPA to its obligation to designate

nonattainment areas under section 107(d)(1) of the Act, 42

U.S.C. § 7407(d)(1). See Air Quality Designations and

Classifications for the 8-Hour Ozone NAAQS, 69 Fed. Reg.
10

23,858, 23,860 (Apr. 30, 2004). EPA entered into a consent

decree requiring it to issue the designations by April 15, 2004.

Id.

On April 30, 2004, EPA promulgated the implementation

rule, 69 Fed. Reg. 23,951, which announced a new approach to

ozone regulation. Reversing its 1997 position, EPA announced

that the one-hour NAAQS would be withdrawn “in full,” one

year following the effective date of the eight-hour NAAQS

designations. Id. at 23,954 (codified at 40 C.F.R. § 50.9(b)).

Under the 2004 Rule, Subpart 2 would apply only to areas that

were nonattaining under both the eight-hour standard and the

now-revoked one-hour standard. Id. at 23,958. Subpart 1 would

apply to the remaining eight-hour nonattainment areas (i.e.,

those with eight-hour design values greater than 0.08 ppm but

one-hour design values no greater than 0.12 ppm). EPA

reasoned that placing more areas under the “more flexible

provisions of the CAA” would “provide the States and Tribes

with greater discretion in determining the mix of controls

needed to expeditiously attain the 8-hour NAAQS.” Id. As a

result, 76 of 122 nonattaining areas would be governed by

Subpart 1. See Proposed Rule To Implement the 8-Hour Ozone

NAAQS, 68 Fed. Reg. 32,802, 32,814 (June 2, 2003)

(hereinafter “2003 NOPR”).

In addition to this interpretation of the classification gap,

the 2004 Rule also addressed the measurement and timing gaps.

Whereas the 1990 Amendments prescribed classifying areas as

of that date and starting the attainment clock on November 15,

1990, under the 2004 Rule, areas would be redesignated under

the eight-hour standard as covered by Subpart 1 or one of the

five categories of Subpart 2 (Marginal, Moderate, Serious,

Severe, or Extreme) according to a regulatory translation of

Table 1. Id. at 23,998 (codified at 40 C.F.R. § 50.903(a) tbl.1).

EPA’s translation meant that areas with the same percentage
11

2 After limited reconsideration proceedings also challenged

here, EPA reaffirmed the 2004 Rule as to NSR, see Nonattainment

Major New Source Review Implementation Under 8-Hour NAAQS:

Reconsideration, 70 Fed. Reg. 39,413 (July 8, 2005) (hereinafter

“NSR Reconsideration”), and made additional findings as to penalties,

deviation from the one-hour NAAQS and the eight-hour

NAAQS would be classified the same. Id. at 23,957. The

deadlines for attainment set forth in Table 1 were interpreted to

restart as of the date of classification under the new standard.

See id. at 23,966-67. Because air quality had improved since

1990, the net effect of the new approach was that many areas

would have a lower classification for eight-hour ozone than they

had for one-hour ozone. Recognizing that this could result in

areas being subjected to less stringent controls, EPA interpreted

the anti-backsliding provision, section 172(e) of the Act, and

reasoned that “if Congress intended areas to remain subject to

the same level of control where a NAAQS was relaxed, they

also intended that such controls not be weakened where the

NAAQS is made more stringent.” Id. at 23,972. As a result, the

2004 Rule mandates that all “controls” from the one-hour era

must remain in place, including controls that a state was already

obligated to adopt but as yet had not. Id. However, EPA

determined that only certain of the programs established by

Congress in Subpart 2 constituted applicable “controls”; the

others would not need to be retained. So, the 2004 Rule

authorized states to remove from their SIPs one-hour New

Source Review (“NSR”), section 185 penalty provisions for

Severe and Extreme areas, conformity demonstrations, and

attainment contingency plans. Id. at 23,984-85.

II.

In these consolidated petitions, a host of parties challenge

the 2004 Rule and related EPA decisions on rehearing.2

 No
12

timing, contingency measures, and attainment demonstrations, see

Phase 1 Implementation of the 8-Hour Ozone NAAQS:

Reconsideration, 70 Fed. Reg. 30,592 (May 26, 2005) (hereinafter

“2004 Rule Reconsideration”).

3 The State petitioners are Connecticut, Delaware, Maine,

Massachusetts, New York, and the District of Columbia.

petitioner disputes that the eight-hour standard must be

implemented; instead, they differ as to how quickly it must be

attained and under what constraints. Parties with similar

concerns were grouped for briefing purposes, leaving four

principal opponents to various aspects of the 2004 Rule: the

State petitioners,3 the Environmental petitioners, the Industry

petitioners, and the State of Ohio. A subset of the petitioners

also intervened to support different aspects of the 2004 Rule to

which other petitioners objected. To summarize the challenges:

The State and Environmental petitioners contend that EPA’s

understanding of the interrelationship between Subpart 1 and

Subpart 2 contravenes the Act and led to arbitrary and capricious

choices reflected in the 2004 Rule. The State of Ohio contends

that EPA erred by establishing an unreasonable timeframe for

attainment. One Industry petitioner, the National Petrochemical

& Refiners Association (“NPRA”), contends that EPA’s

translation of the statutory one-hour Table 1, CAA § 181(a)

tbl.1, 42 U.S.C. § 7511(a) tbl.1, into a converted regulatory

eight-hour Table 1, 40 C.F.R. § 50.903(a) tbl.1, is flawed and

thus arbitrary and capricious. Another Industry petitioner, the

Chamber of Greater Baton Rouge (“Baton Rouge”), contends

that EPA lacks authority to continue to enforce any one-hour

requirements against areas with lower eight-hour classifications.

The State and Environmental petitioners, conversely, contend

that EPA should have retained more of the one-hour control

requirements to prevent backsliding, and the Environmental

petitioners contend that EPA should not have revoked the one-
13

hour standard at all.

Upon review of these challenges, the court may reverse any

action found to be “arbitrary, capricious, an abuse of discretion,

or otherwise not in accordance with law.” CAA § 307(d)(9), 42

U.S.C. § 7607(d)(9). The court will defer to EPA’s statutory

interpretations in accordance with the two-step framework of

Chevron U.S.A. Inc. v. Natural Resource Defense Council, Inc.,

467 U.S. 837, 842-43 (1984); see Bluewater Network v. EPA,

372 F.3d 404, 410 (D.C. Cir. 2004). The court first asks

“whether Congress has directly spoken to the precise question

at issue.” Chevron, 467 U.S. at 842. If so, “that is the end of the

matter; for the court, as well as the agency, must give effect to

the unambiguously expressed intent of Congress.” Id. at 842-43.

However, if “the statute is silent or ambiguous with respect to

the specific issue, the question for the court is whether the

agency’s answer is based on a permissible construction of the

statute.” Id. at 843. Upon review of these challenges, for the

following reasons, we dismiss Ohio’s petition, grant the State

petition, grant the Environmental petition in part, and deny the

Industry petitions. 

III.

The State of Ohio petitions for review on the ground that

the attainment dates for eight-hour ozone are unreasonably soon

and favors waiting to impose the eight-hour standard until the

one-hour standard has been achieved. The Act provides that an

aggrieved party may petition for judicial review in this court as

to any “nationally applicable regulations promulgated, or final

action taken, by the Administrator under [the Act.]” CAA §

307(b)(1), 42 U.S.C. § 7607(b)(1). However, “[o]nly an

objection to a rule or procedure which was raised with

reasonable specificity during the period for public comment

(including any public hearing) may be raised during judicial
14

review.” CAA § 307(d)(7)(B), 42 U.S.C. § 7607(d)(7)(B). As

a result, Ohio is barred from seeking relief from the 2004 Rule.

In its petition for review, Ohio objects to the allegedly

unreasonable attainment time-frame adopted by EPA. Ohio’s

comments during rulemaking, however, express a different view

as to attainment deadlines: that “[EPA’s] approach would be a

reasonable interpretation of Subpart 2.” Ohio EPA’s Comments

on the Proposed 8-Hour Ozone Implementation Plan 2. It is

settled law that a party that presents a winning opinion before

the agency cannot reverse its position before this court. See S.

Pac. Transp. Co. v. ICC, 69 F.3d 583, 588 (D.C. Cir. 1995). 

Citing Appalachian Power Co. v. EPA, 135 F.3d 791 (D.C.

Cir. 1998), Ohio insists that it preserved its challenges in the

cover letter to its comments, where it cautioned EPA that “[t]he

surest way to develop an implementation plan that holds up to

judicial scrutiny would be through an amendment to the Clean

Air Act.” Letter from Christopher Jones, Director, Ohio EPA,

to Marianne L. Horinko, Acting Administrator, EPA (Aug. 1,

2003). Under Appalachian Power, commenters must be given

some leeway in developing their argument before this court, so

long as the comment to the agency was adequate notification of

the general substance of the complaint. Id. at 817-18.

Moreover, for aggrievement that reaches “key assumptions” of

an agency, even the failure to object during the comment period

is insufficient to bar review. Id. at 818. Here, Ohio cannot

seriously claim that it put EPA on notice of its objections to the

details of the 2004 Rule merely by expressing a general

procedural preference in its cover letter. And even if the

attainment deadlines constitute a “key assumption,” nothing in

Appalachian Power supersedes the principle that commenters

may not reverse course after their preferred approach is adopted

by the agency. Therefore, Ohio has forfeited its claims and we

must dismiss its petition.
15

IV.

The State and Environmental petitioners challenge EPA’s

resolution of the gap between Subpart 1 and Subpart 2

recognized by the Supreme Court in Whitman, 531 U.S. at 483.

The State and Environmental petitioners contend that EPA has

repeated the errors of the 1997 Rule by promulgating a

regulation where 76 of 122 nonattaining areas are projected to

be governed by Subpart 1. See 2003 NOPR, 68 Fed. Reg. at

32,814. They further contend that the Act does not support any

ozone nonattainment areas being regulated exclusively under

Subpart 1. Although Whitman forecloses the latter contention,

we agree that the manner in which the 2004 Rule treats the

relationship between Subpart 1 and Subpart 2 fails to adhere to

the statutory scheme enacted by Congress in 1990 to address

ground-level ozone in nonattainment areas.

A.

The purpose of the Clean Air Act has long been “to promote

the public health and welfare and the productive capacity of [the

Nation’s] population.” CAA § 101(b)(1), 42 U.S.C. §

7401(b)(1). The promulgation of a primary NAAQS

specifically addresses this first component, public health. CAA

§ 109(b), 42 U.S.C. § 7409(b); see Am. Petroleum Inst. v.

Costle, 665 F.2d 1176, 1181 (D.C. Cir. 1981). Because

Congress recognized that it must attain this level of air-quality

public health without resort to any “‘magic’ solutions,” it

adopted the comprehensive regulatory requirements of Subpart

2. H.R. REP. NO. 101-490, pt. 1, at 147 (1990), reprinted in 2

LEGISLATIVE HISTORY, supra, at 3021, 3171.

Had there been no scientific advancements of moment in

EPA’s view since 1990, the one-hour standard would still be in

place. Any area with a one-hour ozone level exceeding 0.121
16

ppm would be designated nonattainment and all such

nonattainment areas would be regulated pursuant to the detailed

protocols of Subpart 2. The 1997 Rule changed two aspects of

the NAAQS: the measuring stick and the target. Changes in the

former provide no basis for the displacement of Congress’s

well-considered approach for reaching its desired level of public

health. EPA acknowledged that the level of public health

achieved by 0.121 ppm of one-hour ozone is equivalent to the

level of public health achieved by 0.09 ppm of eight-hour ozone.

See Whitman, 531 U.S. at 483; 1997 Rule, 62 Fed. Reg. at

38,858. Any area failing to achieve the equivalent of Congress’s

chosen level of public health must be covered by Congress’s

chosen prophylactic scheme. Therefore, to the extent that the

2004 Rule regulates areas with an eight-hour design value

exceeding 0.09 ppm under Subpart 1, EPA has misinterpreted

the gap where it is authorized to exercise its discretion and has

trespassed into areas where Subpart 2 unquestionably applies. 

The Supreme Court in Whitman recognized three gaps in

the Act that were evident after the 1997 change in the NAAQS.

The first gap was a measurement gap: “Using the old 1-hour

averages of ozone levels . . . as Subpart 2 requires would

produce at best an inexact estimate of the new 8-hour averages.”

Whitman, 531 U.S. at 483 (citations omitted). The second gap

was a classification gap: “to the extent that the new ozone

standard is stricter than the old one, the classification system of

Subpart 2 contains a gap, because it fails to classify areas whose

ozone levels are greater than the new standard (and thus

nonattaining) but less than the approximation of the old standard

codified by Table 1. Id. (citations omitted). The third gap was

a timing gap: “Subpart 2’s method for calculating attainment

dates . . . seems to make no sense for areas that are first

classified under a new standard after November 15, 1990.” Id.

The State and Environmental petitioners read the
17

classification gap quite narrowly. They maintain that this gap

merely authorized EPA to adjust Table 1 to incorporate newly

nonattaining areas into one of the Subpart 2 categories. Once

EPA translated Table 1, its discretion was exhausted. Under this

reading, however, all areas would be subject to Subpart 2 as a

matter of Chevron Step 1. The Supreme Court in Whitman

indicated otherwise. Although the Court referred to the gap as

a “fail[ure] to classify,” Whitman, 531 U.S. at 483, the Court

later said that it could not “conclud[e] that Congress clearly

intended Subpart 2 to be the exclusive, permanent means of

enforcing a revised ozone standard in nonattainment areas.” Id.

at 484 (emphasis added). 

EPA interpreted the classification gap differently, indicating

“that there was no gap in the statute for those areas with a 1-

hour design value above 0.121 ppm.” 2004 Rule, 69 Fed. Reg.

at 23,957. This reasoning implies that EPA views the gap as a

two-dimensional void bounded by 0.121 ppm of one-hour ozone

and 0.08 ppm of eight-hour ozone. But this approach would

mean that areas with air less healthful than what Congress

thought it had addressed could be freed from Subpart 2. This is

not the gap that the Supreme Court recognized. The Court

characterized the gap as those “areas whose ozone levels are

greater than the new standard (and thus nonattaining) but less

than the approximation of the old standard codified by Table 1.”

Whitman, 531 U.S. at 483 (emphasis added). This statement

was preceded by reference to EPA’s assertion that the “8-hour

standard of 0.09 ppm rather than 0.08 ppm would have

‘generally represent[ed] the continuation of the [old] level of

protection.’” Id. (alterations in original) (quoting 1997 Rule, 62

Fed. Reg. at 38,858).

In other words, the gap identified in Whitman affords EPA

discretion only to the extent that an area is nonattaining but its

air quality is not as dangerous as the level addressed by the 1990
18

Amendments, which now translates to 0.09 ppm on the eighthour scale. Thus, the gap extends only to the extent that the

standard was strengthened and not to the extent that the

measurement technique merely changed. Recall that when the

Supreme Court assessed the 1997 Rule, it thought that the oneand eight-hour standards were to coexist. Id. at 478. But the

Court nowhere indicated that the still-present threshold for onehour compliance should be used to partition eight-hour

nonattaining areas. To the contrary, considering the statements

of the Court in context strengthens the conclusion that the

regulation of the eight-hour standard is to be independent of the

one-hour standard. Eight-hour nonattainment areas must be

subject to Subpart 2 wherever they have air at least as

unhealthful as Congress contemplated when enacting the 1990

Amendments. Because Chevron Step 1 controls the extent of

the gap, we need not address the State and Environmental

petitioners’ further contentions that EPA’s approach absurdly

uses one-hour ozone levels—a metric that EPA concedes is no

longer relevant—to determine how to fix eight-hour ozone

nonattainment, and that this interpretation, by treating areas with

similar eight-hour levels differently, is arbitrary and capricious.

B.

For areas with ozone levels between 0.08 and 0.09 ppm, the

2004 Rule overlaps with the gap recognized in Whitman. To

this extent, the question under Chevron Step 2 is whether EPA’s

interpretation, while not required to “represent[] the best

interpretation of the statute,” is reasonable. Smiley v. Citibank

(S.D.), N.A., 517 U.S. 735, 744-45 (1996). Obviously, EPA’s

approach must be “based on a permissible construction of the

statute.” Chevron, 467 U.S. at 843 (emphasis added).

In the 2004 Rule, EPA determined that for all areas where

it need not impose Subpart 2 requirements, it will not do so.

This conforms to “[o]ne of EPA’s stated goals . . . [,] to provide
19

flexibility to States and Tribes on implementation approaches

and control measures within the structure of the CAA.” 2004

Rule, 69 Fed. Reg. at 23,958. EPA advances several reasons for

its approach: first, “because subpart 2 was developed by

Congress 13 years ago and our scientific understanding of the

causes of ozone pollution and the transport of ozone and its

precursors has significantly advanced,” id. at 23,960; and

second, “[b]ecause control requirements for marginal areas are

similar to those for subpart 1 areas, and because most of these

areas are projected to attain within 3 years, the distinction in

regulatory category may make no practical difference for many

of these areas,” id. at 23,961. See also 2003 NOPR, 68 Fed.

Reg. at 32,814. Even assuming (without deciding) for purposes

of this appeal that the 2004 Rule would be a reasonable

approach to reducing air pollution, it is not a reasonable

interpretation of Congress’s approach in the 1990 Amendments.

The main thrust of EPA’s interpretation is that Subpart 1 is

best because it maximizes EPA’s ability to tailor a SIP to the

situation of that state. But at no point does EPA explain how its

interpretation fits with the 1990 Amendments, which Congress

purposefully crafted to limit EPA discretion. See Whitman, 531

U.S. at 485. Further, to the extent EPA’s rationale rests on the

claims that technology has advanced since 1990, Congress

considered this possibility by providing for periodic review of

each NAAQS. See CAA § 109(d)(1), 42 U.S.C. § 7409(d)(1).

There are no comparable provisions providing that Subpart 2

requirements may be stripped away if EPA becomes convinced

that it may achieve attainment more efficiently. “[I]t is

generally presumed that Congress acts intentionally and

purposely when it includes particular language in one section of

a statute but omits it in another.” City of Chicago v. Envtl. Def.

Fund, 511 U.S. 328, 338 (1994) (internal quotation marks

omitted). The interpretation advanced by EPA cannot be

squared with Congress’s desire to limit EPA discretion by
20

devising a plan that would reach far into the future. See

Whitman, 531 U.S. at 485. As knowledge about the causes and

cures of pollution has increased, Congress has not previously

hesitated to step in and modify its approach. That Congress has

not provided for an agency override of its methodology is

telling.

Similarly, EPA’s insistence that certain areas should not be

subjected to Subpart 2 because they will soon attain the eighthour NAAQS is untethered to Congress’s approach. Congress

considered the possibility of areas being classified nonattaining

but missing the target by only a small amount. These are the

Marginal areas that are required to introduce far less

burdensome ozone controls than areas with more polluted air.

See CAA § 181, 42 U.S.C. § 7511. Thus, even if “Subpart 1 is

preferable to mandating unnecessary Subpart 2 controls,” Brief

for Respondent at 46, EPA cannot replace Congress’s judgment

with its own.

We therefore hold that the 2004 Rule violates the Act

insofar as it subjects areas with eight-hour ozone in excess of

0.09 ppm to Subpart 1. We further hold that EPA’s

interpretation of the Act in a manner to maximize its own

discretion is unreasonable because the clear intent of Congress

in enacting the 1990 Amendments was to the contrary.

V.

Industry petitioner NPRA challenges the conversion of the

one-hour Table 1, codified at 42 U.S.C. § 7511(a) tbl.1, to its

eight-hour regulatory equivalent, 40 C.F.R. § 50.903(a) tbl.1.

We first address EPA’s contention that NPRA lacks Article III

standing to pursue its claims before this court.
21

A.

The doctrine of standing enforces the limitations on the

federal judiciary stemming from the Article III case-orcontroversy requirement. See U.S. CONST. art. III, § 2; Allen v.

Wright, 468 U.S. 737, 750-51 (1984). A party’s standing is a

“predicate to any exercise of our jurisdiction.” Fla. Audubon

Soc’y v. Bentsen, 94 F.3d 658, 663 (D.C. Cir. 1996) (en banc).

As an association, NPRA “has standing to bring suit on

behalf of its members when: (a) its members would otherwise

have standing to sue in their own right; (b) the interests it seeks

to protect are germane to the organization’s purpose; and (c)

neither the claim asserted nor the relief requested requires the

participation of individual members in the lawsuit.” United

Food & Commercial Workers Union Local 751 v. Brown Group,

Inc., 517 U.S. 544, 553 (1996) (quoting Hunt v. Wash. State

Apple Adver. Comm’n, 432 U.S. 333, 343 (1977)). Only the first

element of standing can seriously be challenged here. An

individual plaintiff has standing if it can demonstrate injury-infact that has been caused by the defendant and that is capable of

being redressed by this court’s order. Friends of the Earth, Inc.

v. Laidlaw Envtl. Servs. (TOC), Inc., 528 U.S. 167, 180-81

(2000); Lujan v. Defenders of Wildlife, 504 U.S. 555, 560-61

(1992). 

EPA contests causation on the ground that because only the

states are directly affected by the 2004 Rule, and because EPA

has not specifically mandated controls, NPRA is only harmed

through the intervening acts of the independent third-party

states. See Nat’l Wrestling Coaches Ass’n v. Dep’t of Educ.,

366 F.3d 930, 938 (D.C. Cir. 2004). NPRA responds that it is

inevitable that NPRA members will be affected by the 2004

Rule and will be required to install controls either not previously

required or at an earlier date than previously anticipated.
22

In order for NPRA to have standing, there must be a

“‘substantial probability’ that [EPA’s] action ‘created a

demonstrable risk, or caused a demonstrable increase in an

existing risk, of injury to the particularized interests of’” NPRA.

Nat’l Parks Conservation Ass’n v. Manson, 414 F.3d 1, 6 (D.C.

Cir. 2005) (quoting Fla. Audubon, 94 F.3d at 669). We have

little difficulty concluding that NPRA has met this threshold. It

is inconceivable that EPA’s comprehensive reworking of an Act

that specifically controls the requirements for industrial

pollution would fail to affect the requirements of even a single

NPRA member. See Am. Library Ass’n v. FCC, 406 F.3d 689,

696 (D.C. Cir. 2005); Bethlehem Steel Corp. v. EPA, 723 F.2d

1303, 1306 (7th Cir. 1983); see also Natural Res. Def. Council,

Inc. v. EPA, 902 F.2d 962, 975 n.33 (D.C. Cir. 1990), vacated in

part on other grounds, 921 F.2d 326 (D.C. Cir. 1991);

Overview, supra, at 1815.

B.

NPRA’s petition bridges the classification and timing gaps

referenced in Whitman. See supra Part IV.A. The court

“defer[s] to the EPA’s reasonable resolution of the ambiguity.”

Whitman, 531 U.S. at 484. The essence of NPRA’s challenge is

that while translating Table 1, EPA failed to acknowledge the

differences between one-hour and eight-hour ozone. NPRA

raises two main contentions: first, that eight-hour ozone is

proportionally more difficult to reduce than one-hour ozone; and

second, that EPA adopted the new approach aware that some

areas would be unable to meet the prescribed guidelines, instead

relying upon the states to reclassify themselves voluntarily.

1.

To create an updated version of Table 1, EPA considered a

number of approaches for determining the proper deadlines and

method of classification. With respect to maximum attainment

dates, EPA recognized that “a strict application of Table 1
23

would produce absurd results for most areas” because most of

the deadlines had already passed, and “promulgat[ed] a targeted

revision of Table 1 to reflect attainment dates consistent with

Congressional intent.” 2004 Rule, 69 Fed. Reg. at 23,966.

Because the original attainment dates were linked to the date on

which most areas were designated and classified as a matter of

law, EPA proposed to use the same time periods and to start the

clock as of the time of designation for eight-hour ozone. 2003

NOPR, 68 Fed. Reg. at 32,808.

The other factor influencing attainment deadlines is the

mapping of design values onto area classes. For this purpose,

EPA proposed

to translate the classification thresholds in Table 1 of

section 181 from 1-hour values to 8-hour values in the

following manner: Determine the percentage by which

each classification threshold in Table 1 of section 181

exceeds the 1-hour ozone standard and set the 8-hour

threshold value at the same percentage above the 8-

hour ozone standard. For example, the threshold

separating marginal and moderate areas in Table 1 is

15 percent above the 1-hour standard, so we would set

the 8-hour moderate area lower threshold value at 15

percent above the 8-hour standard.

Id. at 32,812. In response to comments, EPA introduced

additional alternatives and reopened the comment period. Under

the new Alternative A, the range of the one-hour Table 1 was

narrowed so that the eight-hour table used 

50 percent (instead of 100 percent) of the percentages

that the classification thresholds were above the 1-hour

NAAQS in our proposed June 2003 translation of

Table 1. In other words, since the moderate threshold
24

4 Alternative A also utilized a different approach for

distinguishing between Subpart 1 and Subpart 2 areas. All areas with

eight-hour design values exceeding 0.091 ppm were categorized under

Subpart 2. 2004 Rule, 69 Fed. Reg. at 23,957; see supra Part IV.A.

for the 1-hour NAAQS is 15 percent above the 1-hour

NAAQS, we would adjust the moderate threshold for

purposes of the 8-hour NAAQS to be 7.5 percent

above . . . the lowest level in Table 1 for [this

alternative].

2004 Rule, 69 Fed. Reg. at 23,9574

; see also Proposed Rule To

Implement the 8-Hour Ozone NAAQS, 68 Fed. Reg. 60,054,

60,059 (Oct. 21, 2003). The effect of this approach would be to

place more areas in higher classes, giving them more time to

attain (while subjecting them to additional mandatory controls).

NPRA maintains that EPA should have adopted the fiftypercent approach or some other approach that delayed

attainment deadlines it considered to be unreasonable. The basis

for this objection is data provided in the rulemaking comments

of the American Petroleum Institute (“API”). See Comments of

the American Petroleum Institute on the Proposed Rule To

Implement the 8-Hour Ozone National Ambient Air Quality

Standard 7, 13-14. API presented data suggesting that eighthour ozone levels fell at only half the rate of one-hour ozone

levels during the twenty years ending 2001. Id. However, EPA

did not find these data compelling, explaining that “[p]rograms

designed to address the 1-hour ozone NAAQS were not

necessarily designed to reduce 8-hour ozone levels at some

prescribed rate.” Memorandum from Fred Dimmick, Group

Leader, Air Quality Trends Analysis Group, on API Comments

Regarding Relation Between Ozone 1-Hour and 8-Hour Trends

2 (Feb. 11, 2004). So the historical data (for which EPA also

contested the methodology) are not truly predictive of the
25

5 Section 181(b)(3) of the Act provides:

The Administrator shall grant the request of any State

to reclassify a nonattainment area in that State in

accordance with [Table 1] to a higher classification.

The Administrator shall publish a notice in the

Federal Register of any such request and of action by

the Administrator granting the request.

42 U.S.C. § 7511(b)(3). 

relative difficulty in reducing one- and eight-hour ozone.

Indeed, EPA’s own data suggest that the ratio between eighthour and one-hour ozone is converging toward a constant

proportion, eight-tenths. See id. at 2, 4 fig.3. This implies that

reducing one-hour and eight-hour ozone levels by the same

percentage would be equally difficult. In light of these data,

NPRA fails to show that EPA was arbitrary or capricious in

adopting the percentage-deviation approach.

2.

NPRA’s second objection is that EPA acknowledged that its

classification scheme may result in some areas that will not be

able to attain by the deadline prescribed for their category. For

these “misclassified” areas, EPA has decided to rely upon the

voluntary bump-up provision of section 181(b)(3).5

 See 2004

Rule, 69 Fed. Reg. at 23,959-60. NPRA contends that by

resorting to section 181(b)(3), EPA is shirking its classification

responsibility, leaving these decisions to the states contrary to

Congress’s intent. Taken to the extreme, section 181(b)(3)

could damage Congress’s approach. However, Congress

understood that the classification system would not be errorproof and merely chose “outside limits intended to provide a

reasonable target for a large class of nonattainment areas.” H.R.

REP. NO. 101-490, pt. 1, at 229, reprinted in 2 LEGISLATIVE

HISTORY, supra, at 3253.
26

NPRA maintains that EPA anticipates fifteen areas,

including major metropolises, will be unable to attain within the

time allowed. However, EPA found that its chosen option

“provides sufficient time for most areas.” 2004 Rule, 69 Fed.

Reg. at 23,959. Moreover, its modeling did not incorporate

future technological advances. EPA’s “repeated experience over

the past three decades is that market forces stimulated by the

CAA have repeatedly led to technological advances and learning

through experience, making it possible over time to achieve

greater emissions reductions at lower costs than originally

anticipated.” Id.

In light of the nature of the classification scheme, the

availability of section 181(b)(3) bump-ups, and the prospects for

future technological improvements credited by EPA, we deny

NPRA’s petition.

VI.

The final set of challenges concerns what remains of the old

one-hour standard. The Environmental petitioners contend that

EPA’s revocation of the one-hour standard was unlawful and

arbitrary. Short of that, they join the State petitioners in

contending that the 2004 Rule violates the anti-backsliding

provisions of the Act. Industry petitioner Baton Rouge contends

that EPA lacks authority to require any anti-backsliding

provisions that do not relate to the eight-hour NAAQS.

A.

In 1997, EPA determined that, while it was replacing the

one-hour NAAQS with an eight-hour NAAQS, it would

continue to enforce the one-hour NAAQS until “a determination

by the EPA that an area has attained air quality that meets the 1-

hour standard.” Implementation Plan for Revised Air Quality

Standards, 62 Fed. Reg. 38,421, 38,424 (July 18, 1997); see
27

Whitman, 531 U.S. at 478; 1997 Rule, 62 Fed. Reg. at 38,873,

38,894-95. In the 2004 Rule, EPA reversed course, opting

instead to “revoke the 1-hour standard in full, including the

associated designations and classifications, 1 year following the

effective date of the designations for the 8-hour NAAQS.” 2004

Rule, 69 Fed. Reg. at 23,954. The Environmental petitioners

contend that because Congress “codified” the one-hour standard,

EPA cannot revoke it. In the alternative, they contend that EPA

was arbitrary and capricious in revoking the standard, because

maintaining the one-hour standard would also help to reduce

eight-hour ozone levels. EPA responds that any challenge to its

1997 Rule is time-barred, and, in any event, its actions are

reasonable. 

1.

The judicial review provision of the Act provides aggrieved

parties sixty days in which to petition for review. CAA §

307(b), 42 U.S.C. § 7607(b). Were the Environmental

petitioners challenging the revocation of the one-hour standard,

which occurred in the 1997 Rule revising the standard, its

petition would be out of time and the court could not entertain

it. However, we read their petition to challenge only the

revocation of the one-hour standard prior to its attainment, as

their reply brief makes clear. This objection is timely. Cf.

Clean Air Implemention Project v. EPA, 150 F.3d 1200, 1204

(D.C. Cir. 1998).

Because the EPA indicated in the 1997 Rule that it had no

intention of withdrawing the one-hour standard before all areas

had reached attainment, see 1997 Rule, 62 Fed. Reg. at 38,873,

Environmental petitioners had no reason to lodge their challenge

in 1997. The 1997 Rule did not reflect a finding that one-hour

ozone was unimportant and that continued regulation was

unnecessary. See id. at 38,872. As the Environmental

petitioners observe, it was only when EPA switched course in
28

the 2004 Rule, opting to revoke the one-hour standard without

awaiting attainment, that their challenge became ripe. This is

not a case like Environmental Defense v. EPA, 467 F.3d 1329

(D.C. Cir. 2006), where EPA did not change its 1997 regulation

when promulgating a 2004 rule. Id. at 1333. Because the

Environmental petitioners’ challenge is timely, we turn to the

merits.

2.

Section 109(d)(1) of the Act provides that “at five-year

intervals . . . , the Administrator shall complete a thorough

review of the . . . national ambient air quality standards

promulgated under this section and shall make such revisions in

such . . . standards as may be appropriate.” 42 U.S.C. §

7409(d)(1). The anti-backsliding provision, section 172(e),

provides that in the event “the Administrator relaxes a [primary

NAAQS] after November 15, 1990, the Administrator shall . . .

provide for controls which are not less stringent than the

controls applicable to areas designated nonattainment before

such relaxation.” 42 U.S.C. § 7502(e).

The Environmental petitioners contend that the one-hour

standard cannot be withdrawn because Congress “codified” the

one-hour standard in Subpart 2. Congress contemplated,

however, the possibility that scientific advances would require

amending the NAAQS. Section 109(d)(1) establishes as much,

and section 172(e) regulates what EPA must do with revoked

restrictions. While certain other provisions in Subpart 1 are

explicitly rendered inapplicable to ozone when regulated under

Subpart 2, see CAA § 172(a)(1), (2), 42 U.S.C. § 7502(a)(1),

(2), Section 109(d)(1) is not. See Am. Trucking Ass’ns, 175 F.3d

at 1047. Therefore, EPA retains the authority to revoke the onehour standard so long as adequate anti-backsliding provisions

are introduced. Additionally, EPA was not, as the

Environmental petitioners contend, arbitrary and capricious in
29

withdrawing the one-hour requirements, having found in 1997

that the eight-hour standard was “generally even more effective

in limiting 1-hour exposures of concern than is the current 1-

hour standard.” 1997 Rule, 62 Fed. Reg. at 38,863. The only

remaining requirements as to the one-hour NAAQS are the antibacksliding limitations.

B.

Baton Rouge takes the opposite position and contends that

no remnants of the one-hour rule may be retained, except to the

extent that controls are already incorporated into SIPs. These

controls, however, could be removed pursuant to section 110(l)

of the Act once the state demonstrates that their removal will not

“interfere with any applicable requirement concerning

attainment and reasonable further progress” toward the eighthour standard. 42 U.S.C. § 7410(l). 

Baton Rouge has suffered from a history of near-misses in

ozone attainment. In 1990, the area was classified Serious under

Table 1, providing until 1999 to attain. When Baton Rouge

missed attainment, by just 0.002 ppm, it was bumped up to

Severe status by the terms of the Act. See CAA § 181(b)(2), 42

U.S.C. § 7511(b)(2). Baton Rouge had not finished

implementing the controls for a Severe area when the eight-hour

standard was put into place. Based on its eight-hour design

value, Baton Rouge was reclassified under Subpart 2 as

Marginal. 40 C.F.R. § 81.319.

Baton Rouge objects to the 2004 Rule insofar as it requires

the implementation of Severe controls not yet implemented that

it claims do not constitute “applicable requirements” that must

be included in SIPs. 40 C.F.R. § 51.900(f); see CAA §

172(c)(7), 42 U.S.C. § 7502(c)(7). It contends that it should be

subjected only to the requirements for a Marginal eight-hour

area, both because these requirements reflect the improved
30

quality of Baton Rouge’s air and because they now constitute

the “applicable requirements” under the prevailing NAAQS. It

is undisputed, of course, that Baton Rouge would be subject to

all of the Severe requirements but for the change in the NAAQS.

Baton Rouge’s contention is the counterintuitive claim that the

strengthening of the NAAQS entitles it to a weaker regulatory

regime.

At the center of this dispute is EPA’s interpretation of the

anti-backsliding provision, section 172(e), 42 U.S.C. § 7502(e).

By its terms, Section172(e) applies only when EPA “relaxes” a

primary NAAQS, id., but EPA interpreted it to apply here,

reasoning that “if Congress intended areas to remain subject to

the same level of control where a NAAQS was relaxed, they

also intended that such controls not be weakened where the

NAAQS is made more stringent.” 2004 Rule, 69 Fed. Reg. at

23,972. Considered as a whole, the Act reflects Congress’s

intent that air quality should be improved until safe and never

allowed to retreat thereafter. Even if EPA set requirements that

proved too stringent and unnecessary to protect public health,

EPA was forbidden from releasing states from these burdens.

See CAA § 172(e), 42 U.S.C. § 7502(e). Even areas that

attained were not allowed to remove controls. At most, an

attaining area was allowed to shift controls from active

enforcement to the contingency plan that would be automatically

triggered should air quality again deteriorate. CAA § 175A, 42

U.S.C. § 7505a. And EPA was to enforce a high threshold for

removing controls from a SIP—no mandatory controls could be

removed and nothing could be done that would hinder an area’s

ability to achieve prescribed annual incremental emissions

reductions. CAA § 110(l), 42 U.S.C. § 7410(l). As a result,

Baton Rouge’s position that Congress intended to allow the

scenario it prefers does not withstand scrutiny.

Similarly, Baton Rouge’s position that it need not
31

implement one-hour Serious requirements that were not a part

of its SIP when the NAAQS changed fails. A mandatory control

that a state is obligated to implement is “applicable”

notwithstanding the state’s delay in compliance with the

requirement. See 2004 Rule, 69 Fed. Reg. at 23,972. The Act

placed states onto a one-way street whose only outlet is

attainment. That Baton Rouge has found attainment more

difficult than it apparently expected does not entitle it to reverse

course. EPA’s interpretation of section 172(e) is to this extent

consistent with Congress’s expressed intent and therefore is

reasonable.

C.

After interpreting section 172(e) to apply to the

strengthening of the ozone NAAQS, EPA proceeded to limit the

scope of its interpretation. Finding ambiguity in the word

“controls,” EPA determined that one-hour NSR, which it

characterized as a growth measure, need not be continued. 2004

Rule, 69 Fed. Reg. at 23,985. The State and Environmental

petitioners challenge this reinterpretation, as well as EPA’s

treatment of one-hour penalties, rate-of-progress milestones,

contingency plans, and motor vehicle conformity

demonstrations. We conclude that each of these measures is a

“control[]”and that withdrawing any of them from a SIP would

constitute impermissible backsliding.

1.

NSR. NSR is a permitting process that restricts major

modifications and new construction based on an area’s airquality classification. See New York v. EPA, 443 F.3d 880, 883

(D.C. Cir. 2006). As relevant, NSR requires major facilities to

include technology consistent with the lowest achievable

emissions rate (“LAER”) and to offset any increased emissions

with greater reductions elsewhere. See CAA § 173, 42 U.S.C.

§ 7503. As with the rest of the Act, the severity of NSR
32

restrictions increases as the nonattainment classification

worsens. Moving up a classification results in a narrower

definition of a “major” facility and imposes a greater offset ratio

for any increased VOC emissions. See CAA § 182, 42 U.S.C.

§ 7511a. Areas yet to attain the one-hour NAAQS were

classified at best Severe prior to the revocation of the standard.

Under one-hour NSR, they must achieve LAER for any source

exceeding 25 tons per year of VOC emissions and must offset

any increase in VOC emissions by a decrease of 1.3 times that

amount. CAA § 182(d), 42 U.S.C. § 7511a(d).

EPA decided that one-hour NSR requirements are no longer

required under the Act and that areas should be constrained only

by the NSR requirements for their eight-hour classification.

2004 Rule, 69 Fed. Reg. at 23,985. This marked a change from

its 2003 NOPR, in which EPA indicated that “the major source

applicability cut-offs and offset ratios continue to apply to the

extent that the area has a higher classification for the 1-hour

standard than for the 8-hour standard[, because w]e see no

rationale under the CAA . . . why the existing NSR requirements

should not remain ‘applicable requirements.’” 2003 NOPR, 68

Fed. Reg. at 32,821. On reconsideration, EPA affirmed the

revocation of one-hour NSR. See NSR Reconsideration, 70 Fed.

Reg. 39,413. 

The result of this change is to subject fewer areas to LAER

and to offset requirements that themselves are weakened. EPA

maintains that this is proper because NSR is not a “control.”

Instead, EPA defines controls as “mandatory control measures

that can be quantified and relied upon in a modeling

demonstration to show how the measure helps an area reach

attainment.” Brief for Respondent at 95; see also Nonattainment

Major NSR Implementation Under 8-Hour Ozone NAAQS:

Reconsideration, 70 Fed. Reg. 17,018, 17,021-23 (Apr. 4, 2005).

By this reasoning, because NSR does not provide a
33

priori quantifiable emissions reductions, it is not a control. This

interpretation does not withstand scrutiny. By attempting to

redefine what is a “control” circularly as a subset of itself, EPA

violates logic, its own past practice, and the Act’s plain

meaning.

EPA maintains that States do not rely upon NSR to actively

reduce their ozone levels and that NSR was not introduced to

achieve emissions reductions. But this is beside the point

because EPA nowhere claims that if NSR were not present, there

would be no effect on ozone levels. Its arbitrary distinction

between actively reducing levels and merely limiting growth

finds no support in the nature of “control.” Past and current

practice confirms that NSR is a control. The Act itself provides

that the NSR permit program involves “controls” when section

108(h) requires EPA to “make information regarding emission

control technology available to the States and to the general

public through a central database” and indicates that “[s]uch

information shall include all control technology information

received pursuant to State plan provisions requiring permits for

sources.” 42 U.S.C. § 7408(h). EPA has consistently found

NSR to be a control. In its NOx SIP Call, 63 Fed. Reg. 57,356,

57,442 tbl.IV-2 (Oct. 27, 1998), EPA included NSR in its list of

“controls.” In a proposed rule regarding particulate matter, EPA

sought to apply two statutory clauses because they “apply to

[SIP] provisions and control requirements, which include NSR

programs.” Proposed Rule To Implement the Fine Particle

NAAQS, 70 Fed. Reg. 65,984, 66,035 (Nov. 1, 2005); see also

id. at 66,037. In a turbine regulation earlier this year, it stated

that “emission control programs such as . . . NSR already

promote or require emission controls that would effectively

prevent emissions from increasing.” Standards of Performance

for Stationary Combustion Turbines, 71 Fed. Reg. 38,482,

38,491 (July 6, 2006). In addition, the court has previously

characterized NSR as imposing “control requirements.” New
34

York, 443 F.3d at 883; see also Sierra Club v. Costle, 657 F.2d

298, 338 (D.C. Cir. 1981) (quoting Standards of Performance for

New Stationary Sources, 45 Fed. Reg. 8210, 8220 (Feb. 6,

1980)). Furthermore, the House Report introducing the permit

program lists NSR as a “control” at least twice. See H.R. REP.

NO.101-490, pt. 1, at 166, 168 fig.1, reprinted in 2 LEGISLATIVE

HISTORY, supra, at 3190, 3192 fig.1 (“Modification Offsets”).

EPA tries to find ambiguity by interposing section

110(a)(2)(A) against (C) and section 172(c)(1) and (6) against

(5). The Sixth Circuit credited this approach in Greenbaum v.

EPA, 370 F.3d 527 (6th Cir. 2004). However, Greenbaum

involved a different ultimate question, namely, whether NSR is

required for attainment areas, and required that court to

determine the meaning of a different term, “measures.” Because

the term “measures” was used in the provision providing for

redesignation to attainment, the Sixth Circuit found it

appropriate to refer to other instances of “measures” elsewhere

in the Act and concluded that NSR was not a “measure.” Id. at

535-38. This has no bearing on whether NSR is a “control.” In

light of abundant other evidence that NSR is a control, EPA’s

attempt to conjure up ambiguity by referring to provisions

involving a different noun is unavailing.

We therefore conclude that there is no ambiguity as to the

meaning of “control” in Section 172(e), the anti-backsliding

provision. Something designed to constrain ozone levels is a

“control,” and this would include NSR. To conclude otherwise

would mean that Congress considered its carefully-crafted and

well-calibrated graduated restrictions on new and modified

sources less important than other provisions. If anything, the

Act and its legislative history reflect the opposite position. See

New York, 443 F.3d at 887 (citing 42 U.S.C. § 7411(a)(4)); S.

REP. NO. 101-228, at 24-25 (1989), reprinted in 5 LEGISLATIVE

HISTORY, supra, at 8364-65. 
35

6 Section 185(a) of the Act provides:

Each implementation plan revision required [for

Severe and Extreme ozone nonattainment areas] shall

provide that, if the area to which such plan revision

applies has failed to attain the [primary NAAQS] for

ozone by the applicable attainment date, each major

stationary source of VOCs located in the area shall,

except as otherwise provided under subsection (c) of

this section, pay a fee to the State as a penalty for

such failure . . . .

42 U.S.C. § 7511d(a).

2.

Penalties. The 1990 Amendments took a long-horizon

approach to the problem of ozone pollution. Recognizing that

some areas would struggle long into the future, the 1990

Amendments extended attainment dates as late as 2005 and

2010. Beyond those deadlines, the 1990 Amendments provided

for penalties, CAA § 185(a), 42 U.S.C. § 7511d(a),6 to

encourage areas still yet to attain. Because EPA promulgated

the 2004 Rule before the first penalties would have been

required in 2005, the provision has never been enforced. EPA

uses this convenient timing to argue that the section 185(a)

penalties are therefore excluded from the reference in the antibacksliding provision, section 172(e), to “controls applicable . . .

before . . . relaxation.” 42 U.S.C. § 7502(e).

EPA reasons that the Act “does not mandate that controls be

as stringent as those that could not be required to be imposed

until a date after the previous NAAQS no longer exists.” 2004

Rule Reconsideration, 70 Fed. Reg. at 30,593. This assertion is

untenable. By EPA’s reading, the standards could be changed

every fourteenth year—just prior to the attainment date—and a
36

state could go unpenalized without ever attaining even the

original NAAQS referenced in the 1990 Amendments. The

Supreme Court in Whitman instructed that

Subpart 2 was obviously written to govern

implementation for some time. . . . A plan reaching so

far into the future was not enacted to be abandoned the

next time the EPA reviewed the ozone

standard—which Congress knew could happen at any

time, since the technical staff papers had already been

completed in late 1989.

531 U.S. at 485.

As Congress set the penalty deadline well into the future,

giving states and industry ample notice and sufficient incentives

to avoid the penalties, they were “applicable” before they

actually were imposed. For a provision to be “applicable” in

this context, it need not be currently enforceable. Congress

designed section 185(a) to influence state action prior to 2005,

and in this sense, it has long been “applicable.” If a group of

petitioners believed that the penalties were unlawful and would

force the implementation of unnecessary changes, they would

have had a ripe claim long ago under Abbott Laboratories v.

Gardner, 387 U.S. 136, 148-49, 153 (1967). Accord Chamber

of Commerce v. Reich, 57 F.3d 1099, 1101 (D.C. Cir. 1995).

Because these penalties were designed to constrain ozone

pollution, they are controls that section 172(e) requires to be

retained. While EPA maintains that it would be impractical to

enforce these penalties because EPA will no longer make

findings of attainment and conformity assessments as to the onehour standard, see 2004 Rule, 69 Fed. Reg. at 23,985, section

172(e) does not condition its strict distaste for backsliding on

EPA’s determinations of expediency; EPA must determine its

procedures after it has identified what findings must be made
37

under the Act. For these reasons, section 185 penalties must be

enforced under the one-hour NAAQS.

3.

Milestones. Rate-of-progress milestones apply to areas

categorized Moderate and above and require annual percentage

reductions in ozone-precursor emissions. CAA § 182(b)(1),

(c)(2)(B), (d), (e), 42 U.S.C. § 7511a(b)(1), (c)(2)(B), (d), (e).

Serious areas must develop adequate plans to attain threepercent annual reductions over each three-year period until

attainment. CAA § 182(c)(2)(B), 42 U.S.C. § 7511a(c)(2)(B);

see Sierra Club v. EPA, 356 F.3d 296, 299 (D.C. Cir. 2004).

The Environmental petitioners sought review of EPA’s

treatment of these provisions, believing them no longer to apply

to one-hour ozone levels under the 2004 Rule. EPA responded

that petitioners had misinterpreted the 2004 Rule and that rateof-progress plans continue in force as “applicable requirements”

based on the one-hour standard. Because there is no dispute

here, we merely take note of EPA’s interpretation of its rule.

See Alaska Prof’l Hunters Ass’n v. FAA, 177 F.3d 1030, 1033-

34 (D.C. Cir. 1999).

4.

Contingency Plans. Each SIP must include “specific

measures to be undertaken if the area fails to make reasonable

further progress, or to attain the national primary ambient air

quality standard by the attainment date.” CAA § 172(c)(9), 42

U.S.C. § 7502(c)(9); see CAA § 182(c)(9), 42 U.S.C. §

7511a(c)(9) (contingency plans for Serious areas); Sierra Club

v. EPA, 294 F.3d 155, 164 (D.C. Cir. 2002). EPA determined

that “[w]here contingency measures have not yet been triggered,

we believe it is consistent with Congressional intent to allow

areas to remove those measures (or to modify the trigger for

such measures to reflect the 8-hour standard).” 2004 Rule
38

7 Section 176(c)(2)(A) provides that

no transportation plan or transportation improvement

program may be adopted by a metropolitan planning

organization . . . or be found to be in conformity by

a metropolitan planning organization until a final

determination has been made that emissions expected

from implementation of such plans and programs are

consistent with estimates of emissions from motor

vehicles and necessary emissions reductions

Reconsideration, 70 Fed. Reg. at 30,599. 

EPA can point to no aspect of Congress’s approach that

suggests that the one-hour ozone levels specifically addressed by

statute can be allowed to deteriorate. Even if EPA had

determined that ozone was not nearly as damaging as previously

believed and that a level of 100 ppm was acceptable, section

172(e) would still require the automatic imposition of

contingency measures if an area were to miss the preexisting

threshold of 0.12 ppm. This is precisely the type of backsliding

contemplated by the Act. As discussed with respect to penalties,

EPA’s emphasis on whether the controls have been “triggered”

is a red herring. To conform to Congressional intent, one-hour

contingency plans must remain in place even after transitioning

away from the one-hour standard.

5.

Motor Vehicle Emission Budgets. In enacting the 1990

Amendments, Congress was particularly concerned with

pollution arising from automobile emissions. See S. REP. NO.

101-228, at 85-86, reprinted in 5 LEGISLATIVE HISTORY, supra,

at 8425-26. As a result, it strengthened efforts to ensure that

local transportation planning conforms to pollution controls in

approved SIPs by adding section 176(c)(2)(A), 42 U.S.C. §

7506(c)(2)(A).7 See Envtl. Def. Fund v. EPA, 167 F.3d 641,
39

contained in the applicable implementation plan.

42 U.S.C. § 7506(c)(2)(A).

643-44 (D.C. Cir. 1999). Conformity, in turn, requires a finding

that anticipated emissions will not frustrate a SIP’s purpose nor

contribute additional violations or delays in any area. CAA §

176(c)(1), 42 U.S.C. § 7506(c)(1). EPA implemented this

mandate by establishing motor vehicle emissions budgets not to

be exceeded by Metropolitan Planning Organizations. See 40

C.F.R. § 93.118.

In the 2004 Rule, EPA determined that “conformity

determinations [would] no longer [be] required for the 1-hour

NAAQS.” 69 Fed. Reg. at 23,985; see also Transportation

Conformity Rule Amendments for the New 8-Hour Ozone and

PM2.5 NAAQS, 69 Fed. Reg. 40,004, 40,009 (July 1, 2004)

(hereinafter “Transportation Conformity Rule Amendments”).

EPA acknowledged that “the majority of commenters that

addressed this issue objected to EPA’s proposal,” 2004 Rule, 69

Fed. Reg. at 23,986, but concluded that the Act “specifically

states that conformity applies only in” nonattainment and

maintenance areas, id. at 23,987.

Although section 176 provides a floor above which

conformity determinations are required, EPA cannot conclude

that conformity determinations are unnecessary without

confronting section 172(e). Because one-hour conformity

determinations constitute “controls” under section 172(e), they

remain “applicable requirements” that must be retained. EPA

cannot well respond to commenters’ concerns that removing

one-hour conformity demonstrations would “allow large

increases in motor vehicle emissions” by acknowledging that

“requiring conformity for both ozone standards at the same time

would be overly burdensome and confusing.” Transportation
40

Conformity Rule Amendments, 69 Fed. Reg. at 40,009-10. EPA

is required by statute to keep in place measures intended to

constrain ozone levels—even the ones that apply to outdated

standards—in order to prevent backsliding. This principle

encompasses conformity determinations.

VII.

Consistent with Whitman and the Act, we grant the State

petition and the Environmental petition, except with respect to

the withdrawal of the one-hour NAAQS; we also deny the

Industry petitions and we dismiss the Ohio petition.

Accordingly, we vacate the 2004 Rule and remand the matter to

EPA.