# United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued March 22, 2018 Decided July 20 , 2018

No. 16

- 1413

N ATURAL R ESOURCES D EFENSE C OUNCIL AND S IERRA C LUB

, P ETITIONERS

v.

E NVIRONMENTAL P ROTECTION A GENCY AND A NDREW
W HEELER

, R ESPONDENTS

A MERICAN P ETROLEUM I NSTITUTE

, I NTERVENOR

On Petition for Review of a Final Agency Action of the United States Environmental Protection Agency

Margaret T. Hsieh arg ued the cause for petitioners. With

her on the briefs were Sanjay Narayan

, John Walke , and Emily

K. Davis. Nancy S. Marks entered an appearance.

Sue Chen , Attorney, U.S. Department of Justice, arg ued the cause for respondents. With her on the brief was Jeffrey H.

Wood , Acting Assistant Attorney General.

Aaron M. Flynn and Lu cinda Minton Langworthy were on the brief for intervenor

- respondent.2

Caroline Lobdell was on the brief for amici curiae National

Cattlemen ’ s Beef Association, et al. in support of respondents.

Before: G RIFFITH and K ATSAS

, Circuit Judges , and

E DWARDS

, Senior Circuit Judge

.

Opinion for the Court filed by Circuit Judge G RIFFITH

.

G RIFFITH

, Circuit Judge : The Clean Air Act calls upon the Environmental Protection Agency to protect air quality by enforcing state and local limits on the amount of pollution. The agency need not count against those limits pollution caused by “exceptional events.” In this case, Natural Resources Defense

Counci l and Sierra Club challenge a rule the agency uses to

determine whether an event caused by recurring activity is

“natura l,” and thus “exceptional,” or “caused by human activity,” and thus not. 42 U.S.C. § 7619(b)(1)(A)(iii)

. We think the agency’s rule is permitted by the Clean Air Act.

I

To “protect the public health,” 42 U.S.C. § 7409 (b)(1) , t he

Clean Air Act (the “Act”) established a nationwide policy for limiting air pollu tion on the state and local level, id. § 7410.

The Act directs the Environmental Protection Agency ( EPA )

to set uniform levels of concentrations of various pollutants

, National Ambien t Air Quality Standards (NAAQS) , that local

areas must not exceed

. Id. § 7409. E ach state must earn EPA’s approval of a state implementation plan (S IP) , which commits the state to recording levels of specified pollutants using a network of air

- quality monitors. Id. § 7410(a). By recording the concentration levels of these pollutants, the monitors identify areas that exceed the NAAQS. States report pollutant levels to EPA quarterly and receive from the agency “attainment” designations when the levels are below the NAAQS and3

“nonattainment” designations, accompanied by additional ai r

quality regulations, when the levels exceed the NAAQS. Id. § 7407; s ee also , e.g. , 40 C.F.R. § 50.6 (establishing the NAAQS for la rge particulate matter, setting attainment to be exceeding a 24

- hour average concentration of 150 μg/m 3 no

more than one day within a calendar ye ar)

.

Since 1977, EPA has recognized that “[f]ederal, [s]tate, and local air pollution control officials have ex pressed a great

deal of conce rn” that counting emissions caused by “exceptional events” inflates reported levels of pollutants

, which sometimes pushes an area otherwise in att ainment to be designated as non attainment. EPA, EPA

- 450/4

- 86

- 007, Guideline on the Identification and Use of A ir Quality Data Affected by Exceptional Events 1 (1986). To avoid this, EPA suggested in a series of informal guidelines that state and federal agencies need not include in their pollution reports those pollutants emitted from exceptional events

. See, e.g.

, EPA, OAPQS No. 1.2

- 008, Guideline for the Interpretation of Air Quality Standards ( 1977)

. The agency considered events to be exceptional if “they are not expected to recur routinely at a given location, or they are possibly uncontrollable or

unrealistic to control through the [SIP] process.” EPA

- 450/4

- 86

- 007 at 1

. In 2005, Congress added this practice to the Act

. Act of Aug. 10, 2005 , Pub. L. No. 109

- 59, sec. 6013(a), § 319, 119 Stat 1144, 1882

- 884 (codified as amended at 42 U.S.C. § 7619(b) ) (“A ir qualit y monitoring data i nfluenced by exceptional events.” ). Since then, EPA has had statutory authority to exclude from a state’s reported pollutant levels

emissions that result from exceptional events. Id.

The Act sets out several requirements that events must satisfy to be exceptional. Id. § 7619(b)(1)(A). H owever, one of

those requirements applies only to events “caused by human activity” and not “natural event[s].” Id. § 7619(b)(1)(A) (iii)4

(“[A]n event [must be ] caused by human activity that is unlikely to recur at a particular location or a natural event.”)

. T hrough notice

- and

- comment rulemaking , EPA proposed that

“ natural events ” include events that are caused by both natural and human activity , so long as such human activity complies

with relevant envi ronmental regulations. Treatment of Data Influenced by Exceptional Events, 80 Fed. Reg. 72,840, 72,85 4 (Nov. 20, 2015) . Natural Resources Defense Council and

Sierra Club (together, the “environmental groups”) objected to

the definition , arguing that an eve nt caused by human activity

cannot be a natural event. EPA replied that “there is not always a bright line” between natural and human

- caused events , J.A. 135, and adopted the definition as a final rule

, Treatment of Data Influenced by Exceptional Events, 81 Fed. Reg. 68,216 (Oct. 3, 2016) (“2016 Rule”)

.

T he environmental groups filed a timely petition for

review in our court, 1 and we have jurisdiction to review t he

2016 Rule for compliance with the Act

. Se e 42 U.S.C. § 7607(b)(1). The American Petroleum Institute (API) moved

to intervene on behalf of EPA but failed to show the required Article III standing. See Deutsche Bank Nat ional Trust Co. v.

FDIC , 717 F.3d 189 , 193 (D.C. Cir. 2013) . API claims representational standing, 2 API Mot. to Intervene 6 n.2, but that

1 Although an EPA rule previously defined “natural event” in 2007, the 2016 Rule reopened the issue. See Sierra Club v. EPA , 551 F.3d 1019, 1024 (D.C. Cir. 2008)

. 2 An association has standing on behalf of its members when: “(1) ‘its members would otherwise have standing to sue in their own right’; (2) ‘the interests it seeks to protect are germane to the organization’s purpose’; and (3) ‘neither the claim asserted nor the relief requested requires the participation of indiv idual members in

the lawsuit.’” Ctr. for Sustainable Econ. v. Jewell , 779 F.3d 588, 596 (D.C. Cir. 2015) (quoting Hunt v. Wash. State Apple Adver.

Comm’n

, 432 U.S. 333, 343 (1977)).5

requires “specifically identify[ing] members who h ave suffered the requisite harm, ” Chamber of Commerce of the U.S.

v. EPA , 642 F.3d 192, 199 (D.C. Cir. 2011) (citations and

int ernal quotation marks omitted). Nowhere in its motio n or brief does API identify a single member of its organization or support with evidence its vague assertion that an adverse result in this case will injure any member. Because API failed to establish the constitutional standing required t o pa rticipate as an intervenor, we instead grant it the status of amicus curiae

. See Fed. R. App. P. 29(a); s ee also Old Dominion Elec. Coop.

v. FERC , 892 F.3d 1223, 1232

- 34 ( D.C. Cir. 2018); Rio Grande Pipeline Co. v. FERC , 178 F.3d 533 , 539 (D.C. Cir. 1999).

We now consider whether the Act’s exceptional

- event provision permits EPA to attribute emissions to natural causes when they were also caused by regulated human activity.

II

The Act allows areas to keep their attainment designations when their pollutant levels exceed the NAAQS so long as those emissions resulted from an exceptional event. An exceptional

event is one that “affects air quality,” is “not reasonably controllable or preventable,” and is “caused by .

. . activity that is unlikely to recur at a particular location. ” 42 U.S.C. § 7619(b)(1)(A). But even a recurring event can be “exceptional” if it is a “natural event.” Id. § 7619(b)(1)(A) (iii)

.

The Act does not give a definition for “natural event,” so

EPA defined it in the 2016 Rule:

[A natural event is] a n event and its resulting emissions, which may recur at the same location, in which human activity plays little or no direct causal role. For purposes6

of the definition of a natural event, anthropogenic sources that are reasonably controlled sh all be considered to not play a direct role in causing emissions.

81 Fed. Reg. at 68,277 (codified at 40 C.F.R. § 50.1(k))

. In other words, to determine whether a recurring event is natural

, and thus exceptional, EPA looks at the activities that caused th e emissions

. See id. at 68,232 (explaining that EPA classifies events based on the underlying sources of their emissions)

. When making this decision, EPA will disregard contribution s to the emissions made by human activities, or “anthropogenic sources,” that “are reasonably controlled” by complying with emissions regulations. 3 As a consequence, an event is natural

if it resulted from at least some natural activity and any amount, no matter how significant, of reasonably controlle d human activity. See id. at 68,231 (explaining that an event cannot be

“natural if all of the event

- related emissions originated from anthropogenic sources”).

According to the environmental groups, this approach stretches the meaning o f “natural event” b eyond what the text of the Act can bear. They concede that, in some circumstances, the Act permits EPA to classify an event and its resulting

emissions as natural even though human activity played a small

role

. However, they contend that EPA m ust count , for the purposes of characterizing an event as natural, the role played by both types of human activity

— that which complies with environmental regulations and that which does not.

We review EPA’s definition of natural event under

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

Inc. , 467 U.S. 837 (1984): “If the Act unambiguously

3 In general, “reasonably controlled” means that the human activity satisf ied the relevant SIP standards. 40 C.F.R. § 50.14(b)(8)(v).7

aut horizes or forecloses EPA’s .

. . rule, step one of the

Chevron analysis requires that we follow Congress’s express policy choice. If the Act is unclear on the matter, step two of

Chevron requires that we defer to EPA’s reasonable interpretation.” Sierra Club v. E PA , 536 F.3d 673, 677 (D.C. Cir. 2008) (citing Chevron

, 467 U.S. at 842

- 43)

.

At step one, we consider whether the Act issued unambiguous instructions for distinguishing natural events

from events caused by human activity

. O utside its statutory

context

, “ natural ” ordinarily means something unaffected by human activity

. See, e.g.

, M erriam

- Webster ’s Collegiate Dictionary 774 (10th ed. 1997) ( defining natural as “growing

without human care

. . . ex isting in or produced by nature : not artificial”); Oxford English Dictionary Online, http://www.oed.com/view/Ent ry/125333 (3d ed. 2003) ( defining natural as “[f]ormed by nature; not subject to human intervention, not artificial” ); Black’s Law Dictionary 1048 (7th ed. 1999) (defining natural as “[b] rought about by nature as opposed to artificial means ” ). And an ordin ary reading of

“natural event” summons images of natural disasters such as tornados and volcanic eruptions; cosmic episodes, such as

comets and harvest moon s; and organic processes, such as vir al epidemics and seasonal changes

. These examples leave little

room for human causation

.

But what “natural event” means in the Act does not depend entirely on its ordinary reading because “the words of a statute must be read in their context and with a view to their place in the overall statutory scheme.” Nat’l Ass’n of Home Builders v. Defenders of Wildlife , 551 U.S. 644, 666 (2007) (in ter nal quotation marks omit ted) ; see also Pereira v. Sessions

, 138 S. Ct. 2105, 2110 (2018) ( interpreting the statute in light of its statutory context)

. B y pairing “natural event ” alongside “an event caused by human activity,” the Act uses the phrase as a8

tool to separate events into the two categories , requiring it to

carry a special meaning. Perhaps if EPA had to separate only those events caused by either solely natural or sole ly human activity, the ordinary understanding of “natural event” might

do the trick. But many events are caused by a combination of

the two. For example, c onsider a windstorm that sweep s dust

into the air so that it is emitted as small particulate matter, which is subject to the NAAQS

. A t first blush, the emissions appear to be the result of the windstorm and, therefore, a natural

event. Bu t this is less obvious if the storm swept up the dust only because the ground’s surface had been loosened by recent

con struction

. See 80 Fed. Reg. at 72,854 n.34 . In that case, the natural event caused the emissions only because human activity changed the landscape. The point at which hu man contribution s convert a natural event into one caused by human activity is blurry at best

.

But EPA must draw that line

, and the Act provides little guidance beyond est ablishing that the distinction exists. 4 See

42 U.S.C. § 7619(b)(1)(A)(iii) (allowing an event to be exceptional only if it is “natural” or “caused by human activ ity that is unlikely to recur at a particular location”). Many possible rules for sorting events may be permissible under the

statute. S ome may be easier to administer than others, but the

Act leaves the choice t o EPA. The statutory language is far

from un ambigu ous and is, instead, a classic example of Congress leaving a gap for EPA to fill with reasonable regulations. See Nat’l Cable & Telecomm. Ass’n v. Brand X

Internet Servs. , 545 U.S. 967 , 980 (2005) (“[A]mbiguities in statutes within an agency’s jurisd iction to administer are delegations of authority to the agency to fill the statutory gap in reasonable fashion.”); Chevron , 467 U.S. at 843

- 44.

4 The Act also provides broad governing principles, such as the supremacy of public health , that could place some limits on EPA’s

choice of rules

. See 42 U.S.C. § 7619(b)(3).9

It is at Chevron step two that we determine if the 2016 Rule “fill[s] the statutory gap in reasonable fashion. ” Brand X , 545

U.S. at 980. The environmental groups think the rule upends

the statut ory distinction between natural events and those caused by human activity . They contend it is unreasonable for

EPA to assume that human activity did not cause an event simply because that activity complied with environmental regulations

. As a consequence, they worry, EPA will treat emissions from recurring human activity as emissions from an exceptional event.

To illustr ate their concern, they describe how the 2016 Rule would apply to a windstorm that blew pollutants emitted from a reasonably controlled power plant to another jurisdiction’s air

- qual ity monitor

, which then registered a much higher pollutant concentration t han would be typical for that

area. The environmental groups argue that EPA would consider

the emissions to be the result of a natural event

. Although human activity produced the emissions, they believe EPA would not consider the role played by the power p lant because it complied with the relevant air

- quality regulations. Instead,

EPA would look to only the windstorm and conclude that the

event was natural.

But such an outcome wouldn’t be possible under the statutory and regulatory safeguards in place. T he environmental groups do not challenge EPA’s understanding

that an “event” must be an occurrence that “deviat[es] from normal or expected conditions.” 81 Fed. Reg. at 68,228. Emissions that result from only “ routine” activity cannot be

treated as exceptional

- event emissions. Id.

The environmental groups seem to suggest that emissions

from “ routine ” activities could become emissions from an10

“ event ” if they are later affected by unexpected activity

. However, this misreads the 2016 Rule. “ Natural ev ent means an event and its resulting emissions,” 40 C.F.R. § 50.1(k) (second emphasis added), and EPA has made clear that emissions only result from the events that generate them, 81 Fed. Reg. at 68,226. 5 Activities that cause emissions to behave

in a cert ain way, such as migrating to new areas or concentrating in dangerous amounts, are not events that cause

the emissions. Id . In the windstorm example, it was the power plant and not the windstorm that generated the emissions. Although the pollutants only re ached the monitor because they were carried by the windstorm, they were emitted into the air before the wind arrived at the scene. Under the 2016 Rule,

those emissions would be attributed to the power plant, not the natural activity of the windstorm. 6

T he agency would give a different answer for emissions generated by a windstorm that s wept up particulate matter fr om a dirt road

. In that case , no pollutants would be emitted until

the wind struck the road and swept particles into the air. If the

road w ere reasonably controlled, EPA would discount the

5 To the extent the environmental groups are challenging EPA’s interpretation of its own regulations, we defer to the agency’s understanding. See Auer v. Robbins , 519 U.S. 452, 461 (1997) (holding that an agency’s interpretation of its own regulation, unless “plainly erroneou s or inconsistent with the regulation,” controls (internal quotation marks omitted)). Even if the regulation could be read to include emissions that have already been generated, EPA’s reading is certainly consistent with the 2016 Rule.

6 This does not mea n that emissions produced by human activity and transported by wind to a new area can never be the result of an exceptional event. It simply means that EPA would treat them as a result of human activity and consequently subject to the recurrence

condition for exceptional events. See, e.g. , 81 Fed. Reg. at 68,280 (discussing “emissions

- generating activity that occurs outside of the State’s jurisdictional boundaries”).11

road’s role and look onl y to the windstorm. But if the road had been improperly maintained , EPA would consider both the

road’s and the windstorm’s contribution s to the emissions.

We think the 2016 Rule prese rves the Act’s distinct

t reatment of natural events

. Although we recognize the possibility raised, but not demonstrated, by the environmental groups that extreme and unforeseen applications of the rule might have problematic results, the 2016 Rule still pa sses muster under Chevron step two. The “possibility that the rule, in uncommon particular applications, might exceed EPA’s statutory authority does not warrant judicial condemnation of the rule in its entirety.” EPA v. EME Homer City Generation,

L.P. , 134 S. Ct. 1584, 1609 (2014) ; see also Babbitt v. Sweet Home Chapter of C mtys. for a Great Or

. , 515 U.S. 687, 699

- 700 (1995) (upholding a rule as reasonable despite possible applications that would be impermissible under the statute ). If EPA applies the rule in a way that the Act would not permit

, an injure d party can petition us to review the agency’s action at

that time

. See EME Homer City , 134 S. Ct. at 1609 (explain ing

that as

- applied challenges remain available if EPA were to apply a rule, which the C ourt had upheld under Chevron , in a way that was impermissible under the statute) ; Util. Air Regulatory Grp. v. EPA , 885 F.3d 714, 723 (D.C. Cir. 2018).

F or now, we uphold the definition of natural event against the environmental group’s facial challenge to th e 2016 Rule

.

III

We deny the petition for review because t he 2016 Rule’s

definition of natural event is permissible under the Act.

So ordered

.