 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued October 12, 2018               Decided April 26, 2019

                        No. 17-1201

             ENVIRONMENTAL DEFENSE FUND,
                     PETITIONER

                             v.

    ENVIRONMENTAL PROTECTION AGENCY AND ANDREW
       WHEELER, ADMINISTRATOR, UNITED STATES
         ENVIRONMENTAL PROTECTION AGENCY,
                   RESPONDENTS

          AMERICAN CHEMISTRY COUNCIL, ET AL.,
                    INTERVENORS


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


     Robert P. Stockman argued the cause and filed the briefs
for petitioner.

     Phillip R. Dupré, Attorney, United States Department of
Justice, argued the cause for respondents. With him on the
brief was Jeffrey H. Wood, then-Acting Assistant Attorney
General.

   Donald P. Gallo, James W. Conrad, Jr., Richard S.
Moskowitz, Peter D. Keisler, Samuel B. Boxerman, Timothy K.
                              2
Webster, C. Frederick Beckner, III, Judah Prero, Samina M.
Bharmal, David B. Weinberg, Martha E. Marrapese, Roger H.
Miksad, Linda E. Kelly, Steven P. Lehotsky, and Michael B.
Schon were on the brief for intervenors in support of
respondent United States Environmental Protection Agency.
Michael D. Boucher and Warren U. Lehrenbaum entered
appearances.

    Before: GARLAND, Chief Judge, MILLETT, Circuit Judge,
and EDWARDS, Senior Circuit Judge.

    Opinion for the Court filed by Circuit Judge MILLETT.

     MILLETT, Circuit Judge: The Toxic Substances Control
Act, 15 U.S.C. § 2601 et seq., requires the Environmental
Protection Agency to publish an inventory of chemicals
manufactured or processed in the United States.
15 U.S.C. § 2607(b)(1). The 2016 Amendments to the Act
directed the EPA to issue a rule establishing a process for
updating the Inventory. The EPA promulgated that rule the
following year. See TSCA Inventory Notification (Active-
Inactive) Requirements, 82 Fed. Reg. 37,520 (Aug. 11, 2017).
As part of that rulemaking process, the EPA abandoned
questions that had required each company seeking to keep the
chemical identity of a substance confidential to substantiate
that the chemical identity “is not readily discoverable through
reverse engineering.” 15 U.S.C. § 2613(c)(1)(B)(iv).

     The Environmental Defense Fund challenges that 2017
rule on the ground that it unlawfully shields information from
public disclosure. Environmental Defense is correct that the
EPA’s elimination of questions pertaining to reverse
engineering was arbitrary and capricious, and so we grant the
petition in that respect. We otherwise deny the petition for
review.
                               3

                               I

                               A

     Congress passed the Toxic Substances Control Act
(“Control Act”) in 1976 to “assure that * * * innovation and
commerce in * * * chemical substances and mixtures do not
present an unreasonable risk of injury to health or the
environment.” 15 U.S.C. § 2601(b)(3). Congress charged
the EPA with administering the Control Act, which included
the tasks of “compil[ing], keep[ing] current, and publish[ing] a
list of each chemical substance which is manufactured or
processed in the United States.” Id. § 2607(b)(1). That list,
commonly referred to as the “Inventory,” contains a
confidential portion and a non-confidential portion. Id.
§ 2607(b)(4)(B)(i). Both portions are publicly accessible on
the EPA’s website. But the confidential portion identifies
substances by “a structurally descriptive generic name” rather
than a “specific chemical identity.”               15 U.S.C.
                 1
§ 2613(c)(1)(C). The Inventory currently lists approximately
86,000 chemicals, roughly 18,000 of which are classified as
confidential.

     “[C]oncern[ed] about the pace of EPA’s work” keeping
the Inventory up to date, H.R. REP. NO. 176, 114th Cong., 1st
Sess. 12 (2015), Congress amended the Control Act in 2016.
See Frank R. Lautenberg Chemical Safety for the 21st Century
Act, Pub. L. No. 114–182, 130 Stat. 448 (2016) (codified at 15
U.S.C. § 2601 et seq.).        As relevant here, the 2016

    1
          See How to Access the TSCA Inventory, EPA,
https://www.epa.gov/tsca-inventory/how-access-tsca-inventory
#download (last visited April 17, 2019).
                               4
amendments directed the EPA to promulgate a rule—known as
the Inventory Rule—that would impose new reporting
requirements for chemical manufacturers and processors
(“chemical companies”). See 15 U.S.C. § 2607(b)(4)–(5).
Specifically, the Inventory Rule requires chemical companies
to notify the EPA of each chemical on the Inventory that they
had “manufactured or processed for a nonexempt commercial
purpose” during the ten-year period prior to June 22, 2016. Id.
§ 2607(b)(4)(A)(i). Each chemical for which the EPA
receives such a notification would be labeled “active,” while
all the rest would be labeled “inactive.”                   Id.
§ 2607(b)(4)(A)(ii)–(iii), (b)(5)(B)(i)–(iii).         Chemical
companies also have to submit a notification form identifying
in advance any inactive chemical substance for which they
intend to resume manufacturing or processing going forward.
Id. § 2607(b)(5)(B)(i).

     Congress directed the EPA to update the confidential
portion of the Inventory as well. In particular, the 2016
amendments to the Control Act instruct the EPA to (i) “require
any manufacturer or processor of a chemical substance on the
confidential portion of the [Inventory] that seeks to maintain an
existing claim for protection against disclosure of the specific
chemical identity of the chemical substance as confidential” to
notify the EPA of that request; (ii) demand that chemical
companies provide “substantiation” for those claims of
confidentiality; and (iii) “move any active chemical substance
for which no [confidentiality] request [i]s received” to the non-
confidential portion of the list. 15 U.S.C. § 2607(b)(4)(B).

     When an application to maintain confidential treatment is
received, the EPA must independently determine whether
confidentiality is warranted. To that end, Congress directed
the EPA to “promulgate a rule that establishes a plan to review
                               5
all claims to protect the specific chemical identities” asserted
as confidential. 15 U.S.C. § 2607(b)(4)(C).

     Once the EPA compiles the initial list of active chemical
substances, the Control Act affords the agency up to seven
years to complete its review of which of those active chemical
substances should receive confidential treatment. 15 U.S.C.
§ 2607(b)(4)(E). For those chemicals that remain on the
confidential portion of the Inventory, the EPA must “develop a
system to assign a unique identifier to each specific chemical
identity” and must “apply that identifier consistently to all
information relevant to the applicable chemical substance[.]”
Id. § 2613(g)(4)(A).

     The EPA promulgated the final Inventory Rule in August
2017. 82 Fed. Reg. 37,520 (codified at 40 C.F.R. §§ 710.23–
710.39). The Inventory Rule implements the retrospective
and prospective reporting requirements that Congress required.
Companies that manufactured and processed chemicals during
the ten years prior to June 22, 2016 must submit a “Notice of
Activity Form A.” See id. at 37,523, 37,525. After the EPA
designates substances as active or inactive, those that intend to
revive the manufacture or processing of an inactive chemical
must submit a “Notice of Activity Form B.” See id. These
Forms also allow a manufacturer or processor of a chemical
that was originally on the confidential portion of the Inventory
to seek to continue that confidential status going forward.
And it may do so regardless of whether that manufacturer or
processor was the one that had initially requested that the
chemical identity be shielded from public disclosure. Id. at
37,527.

    To assert a claim of confidentiality, the Control Act
requires the requesting company to certify that:
                                6
   (i)       My company has taken reasonable measures
             to protect the confidentiality of the
             information;

   (ii)      I have determined that the information is not
             required to be disclosed or otherwise made
             available to the public under any other
             Federal law;

   (iii)     I have a reasonable basis to conclude that
             disclosure of the information is likely to
             cause substantial harm to the competitive
             position of my company; and

   (iv)      I have a reasonable basis to believe that the
             information is not readily discoverable
             through reverse engineering.

82 Fed. Reg. at 37,544 (codified at 40 C.F.R. § 710.37(e)); see
also 15 U.S.C. § 2613(c)(1)(B) (establishing these criteria).

    But the Control Act does not stop there. The Act further
mandates that, once a claim of confidentiality is asserted, its
proponent must “substantiate” the need for secrecy.
15 U.S.C. § 2613(c)(3); see also id. § 2607(b)(4)(B)(iii)
(instructing the EPA to “require the substantiation of
[confidentiality] claims”). To implement that substantiation
requirement, the Inventory Rule requires applicants to answer
the following questions:

   •      Do you believe that the information is exempt
          from [the Act’s] substantiation [requirement]?
                              7
   •   Will disclosure of the information likely result
       in substantial harm to your business’s
       competitive position?

   •   To the extent your business has disclosed the
       information to others (both internally and
       externally), what precautions has your business
       taken?

   •   Does the information appear in any public
       documents, including (but not limited to) safety
       data sheets, advertising or promotional material,
       professional or trade publication, or any other
       media or publications available to the general
       public?

   •   Is the claim of confidentiality intended to last
       less than 10 years[?]

   •   Has EPA, another federal agency, or court made
       any confidentiality determination regarding
       information associated with this chemical
       substance?

   •   Is the confidential chemical substance publicly
       known to have ever been offered for
       commercial distribution in the United States?

See 82 Fed. Reg. at 37,544 (codified at 40 C.F.R. § 710.37(c)).

     The Inventory Rule does not expressly incorporate all of
the Act’s many procedural requirements. Nor does it address
the Control Act’s requirement, 15 U.S.C. § 2613(g)(4), that the
EPA assign “unique identifiers” to chemicals that it eventually
                                8
decides should be listed on the confidential portion of the
Inventory.

                                B

     The Environmental Defense Fund is an organization that
promotes public awareness of the environmental and health
risks that chemicals pose. See Environmental Defense
Standing Addendum 3.           Environmental Defense timely
petitioned this court for review of the Inventory Rule. See 15
U.S.C. § 2618(a). A group of chemical-industry associations
(“Industry”) intervened in support of the EPA.

                               II

     We start, as we must, by verifying that Environmental
Defense has Article III standing to challenge the Inventory
Rule. See DaimlerChrysler Corp. v. Cuno, 547 U.S. 332, 340
(2006) (“We have ‘an obligation to assure ourselves’ of
litigants’ standing under Article III.”) (quoting Friends of the
Earth, Inc. v. Laidlaw Envtl. Servs. (TOC), Inc., 528 U.S. 167,
180 (2000)). To that end, Environmental Defense must
demonstrate that it has suffered a concrete and particularized
injury in fact that is both fairly traceable to the EPA’s action
and likely to be redressed by a favorable judicial decision.
Lujan v. Defenders of Wildlife, 504 U.S. 555, 560–561 (1992).

     Environmental Defense has succeeded in that task by
asserting a quintessential claim of informational standing.
The law is settled that “a denial of access to information”
qualifies as an injury in fact “where a statute (on the claimants’
reading) requires that the information ‘be publicly disclosed’
and there ‘is no reason to doubt their claim that the information
would help them.’” Friends of Animals v. Jewell, 824 F.3d
1033, 1040–1041 (D.C. Cir. 2016) (quoting Ethyl Corp. v.
                               9
EPA, 306 F.3d 1144, 1148 (D.C. Cir. 2002)); see also FEC v.
Akins, 524 U.S. 11, 21 (1998). Here, Environmental Defense
claims that the Control Act requires disclosure to it (and the
public at large) of chemical identities that the Inventory Rule
will keep secret. And “there is no reason to doubt” that access
to additional information about chemicals manufactured or
processed in the United States will promote Environmental
Defense’s environmental interests, research, and educational
activities. Jewell, 824 F.3d at 1041 (quoting Ethyl Corp., 306
F.3d at 1148); see generally Environmental Defense Standing
Addendum. Finally, a decision by this court to vacate or
require reconsideration of the rule would remedy that asserted
harm by requiring the disclosure of additional information.
See Wertheimer v. FEC, 268 F.3d 1070, 1074–1075 (D.C. Cir.
2001).

                               A

     Environmental Defense challenges five distinct features of
the Inventory Rule: (i) the EPA’s exclusion of substantiation
questions regarding reverse engineering; (ii) the Rule’s criteria
for “maintaining” a confidentiality claim; (iii) the EPA’s
choice not to incorporate certain regulatory requirements into
the Inventory Rule; (iv) the EPA’s failure to implement the
Act’s “unique identifier” requirements in this rulemaking; and
(v) the Rule’s exemption of exported chemicals from its
notification requirements. We must uphold the EPA’s Rule
unless it is “arbitrary, capricious, an abuse of discretion, or
otherwise not in accordance with law.” 5 U.S.C. § 706(2)(A);
see also 15 U.S.C. § 2618(c)(1)(B). Under that standard of
review, only Environmental Defense’s first claim succeeds.
                              10
                               1

    Environmental Defense challenges the EPA’s failure to
require companies to “substantiate” that a chemical identity
they wish to keep confidential is not “readily discoverable
through reverse engineering.”             See 15 U.S.C.
§ 2613(c)(1)(B)(iv), (c)(3). We agree that the reverse-
engineering aspect of the Inventory Rule comes up short.

                               a

     At the outset, the EPA and Industry argue that
Environmental Defense lacks standing to challenge the
agency’s choice of substantiation questions. In their view, it
is “merely speculative” that the inclusion of any particular
question “would lead EPA to disapprove—or would cause a
potential claimant not to submit—a request to maintain a
specific chemical identity on the confidential portion of the
* * * Inventory.” EPA Br. 35 (formatting altered).

     That makes little sense. Substantiation questions are the
EPA’s tool for gathering the information it uses to evaluate
confidentiality claims.      They are, in other words, an
indispensable procedural step in the agency’s confidentiality
determination. Because Environmental Defense asserts an
informational injury that arises directly from confidentiality
determinations, “[a]ll that is necessary” for standing is for
Environmental Defense “to show that the procedural step was
connected to the substantive result.” Sugar Cane Growers
Coop. of Fla. v. Veneman, 289 F.3d 89, 94–95 (D.C. Cir. 2002);
see also Center for Biological Diversity v. EPA, 861 F.3d 174,
184 (D.C. Cir. 2017) (petitioner “need not show that but for the
alleged procedural deficiency the agency would have reached
a different substantive result”). Informing the confidentiality
decision is the raison d’être of the substantiation questions.
                               11
And that is the end of the matter as far as standing is concerned.
See Veneman, 289 F.3d at 94–95.

                                b

     When a company makes a confidentiality claim under the
Act, it must both “assert” and then “substantiate” the need for
such protection. 15 U.S.C. § 2613(c)(1), (3). An “assertion”
of a confidentiality claim must “include a statement” that,
among other things, the claimant has a “reasonable basis to
believe that the information is not readily discoverable through
reverse engineering.”         Id. § 2613(c)(1)(B)(iv).       The
Inventory Rule properly effectuates that requirement. 82 Fed.
Reg. at 37,544 (codified at 40 C.F.R. § 710.37(e)(4)). The
problem for the EPA is that the Control Act does not accept a
company’s assertions at face value. Quite the opposite, the
statute specifically requires the company to “substantiate” its
confidentiality claim. 15 U.S.C. § 2613(c)(3).

     In the Notice of Proposed Rulemaking for the Inventory
Rule, the EPA listed more than twenty substantiation questions,
including questions related to each of the four statutorily
required assertions. 82 Fed. Reg. 4255, 4268–4269 (Jan. 13,
2017); see 15 U.S.C. § 2613(c)(1)(B). To address reverse
engineering, the proposed questions were:

       Does this particular chemical substance leave
       the site of manufacture in any form, e.g., as
       product, effluent, emission?       If so, what
       measures have been taken to guard against the
       discovery of its identity? * * * If the chemical
       substance leaves the site in a product that is
       available to the public or your competitors, can
       the chemical substance be identified by analysis
       of the product?
                               12

Id. at 4268.

    By the agency’s own admission, the final rule sets forth an
“extensively re-written” list of questions. 82 Fed. Reg. at
37,527, 37,537. The EPA scrapped, among other things, all
substantiation questions related to the requirement that a
substance’s chemical identity not be susceptible to reverse
engineering. See id. at 37,544.

    An agency acts arbitrarily and capriciously when it offers
inaccurate or unreasoned justifications for a decision. See
Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State Farm Mut.
Auto. Ins. Co., 463 U.S. 29, 43 (1983); Clean Air Council v.
Pruitt, 862 F.3d 1, 10 (D.C. Cir. 2017) (concluding that the
EPA’s explanation for a decision was “inaccurate and thus
unreasonable”).

    That is precisely what the EPA did here. Its omission of
any inquiry into a chemical identity’s susceptibility to reverse
engineering effectively excised a statutorily required criterion
from the substantiation process.              See 15 U.S.C.
§ 2613(c)(1)(B)(iv), (c)(3). Lest there be any doubt, the
agency conceded at oral argument that the Inventory Rule
eliminated the only questions that substantiate the assertion that
“the information is not readily discoverable through reverse
engineering.” Id. § 2613(c)(1)(B)(iv); see Oral Argument Tr.
at 35:42–35:46 (“These questions do not specifically
encompass reverse engineering.”).

    The agency’s explanation for excising that criterion was,
nonsensically, a denial that it had done so. Specifically, the
EPA explained that the omission is “intended to more
succinctly secure answers for the basis of the [confidentiality]
assertions[.]” 82 Fed. Reg. at 37,537 (emphasis added). But
                              13
succinctness means no unnecessary words; it does not mean no
words at all. What the Inventory Rule actually does is decline
altogether to “secure answers” substantiating a company’s
“assertion” that its chemical product cannot be reverse
engineered. Id. But it makes no sense to treat as confidential
the chemical identity of a substance that can readily be
discovered through reverse engineering—as the EPA itself
agrees. Oral Argument Tr. 24:48–24:59 (“[D]oes the EPA
agree that if something is readily reversibly engineered [then]
it doesn’t qualify for confidential treatment?” [Agency
counsel]: “Yes.”).

     Yet the EPA’s Rule offers no sensible explanation at all
for that gap in substantiation, nor does it even acknowledge the
consequence of its omission. That error is fatal. The
Inventory Rule is arbitrary and capricious to the extent that it
omits any substantiation requirement pertaining to reverse
engineering. See State Farm, 463 U.S. at 43; Clean Air
Council, 862 F.3d at 10.

                               2

     Next, Environmental Defense contends that the Inventory
Rule enables a broader array of companies to “maintain” an
existing confidentiality claim than the Control Act allows. 15
U.S.C. § 2607(b)(4)(B)(ii). That is incorrect.

     Under the Control Act, if a manufacturer or processor
wants the confidential status of an already listed chemical to
continue on the updated Inventory, it must submit a request to
the EPA. 15 U.S.C. § 2607(b)(4)(B)(ii). The EPA reads that
statutory directive to allow “any manufacturer or processor [to]
seek to maintain an existing claim for specific chemical
identity,” even if the company was not the source of the
“original claim that caused the specific chemical identity to be
                               14
listed on the confidential portion of the Inventory.” 82 Fed.
Reg. at 37,527. That is, the Inventory Rule allows any
company that manufactures or processes substances already on
the confidential Inventory to seek perpetuation of that status,
regardless of whether it was the company that claimed
confidentiality in the first place.

     Environmental Defense reads the statutory language
differently. In its view, the Control Act permits only the
original claimant or its successor-in-interest to preserve
confidential treatment.

    The EPA wins this debate.

      For starters, the text of the Control Act does not require
Environmental Defense’s rule.           The relevant statutory
language is silent as to whether a company may maintain an
existing claim of confidentiality if it was not the original
claimant. See 15 U.S.C. § 2607. Congress thus left that
question of implementation to the expertise of the EPA. See
Chevron U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467
U.S. 837, 844 (1984). So we must sustain the EPA’s position
if it “is based on a permissible construction of the statute.” Id.
at 843.

      The EPA’s position easily clears that hurdle. Allowing
any chemical manufacturer or processor to seek continued
protection against public disclosure for its chemical substance
fits comfortably within the statutory text. Section 2607’s sole
limitation on the class of manufacturers and processors that
may wish to maintain an existing confidentiality claim is that
they manufacture or process “a chemical substance on the
confidential portion of the [Inventory].”           15 U.S.C.
§ 2607(b)(4)(B)(ii).    “[A]ny” of those manufacturers or
processors may apply. Id. (emphasis added).
                              15

      Nothing in the word “maintain” contracts that broad
language. To “maintain” commonly means “to keep in an
existing state.” MERRIAM-WEBSTER DICTIONARY 431 (def.
1) (7th ed. 2016). The word imposes no limit on who may do
that maintaining. A recent homebuyer, for example, might
maintain the existing landscaping.      New team players
certainly hope to maintain the winning streak of last year’s
team. So too here, the statutory language naturally permits a
manufacturer or processor to maintain a confidentiality status
first obtained by another.

     Environmental Defense agrees that an original claimant’s
successor-in-interest can “maintain an existing claim.” But
nothing in the statutory text requires drawing an impermeable
line there. The EPA reasonably concluded that the claimant’s
corporate genealogy is beside the point.

     Environmental Defense reasons that all claimants who
were not original claimants or their successors-in-interest
should be required to file a new claim of confidentiality under
15 U.S.C. § 2613. That route would afford the EPA just
ninety days for review, 15 U.S.C. § 2613(g)(1)(A), as opposed
to the seven years allowed to decide whether existing claims of
confidentiality should continue, id. § 2607(b)(4)(E).

     Environmental Defense’s approach is no real alternative at
all. The Control Act provides that for active substances, if “no
request [i]s received to maintain an existing claim for
protection against disclosure,” the EPA “shall” move that
chemical substance “from the confidential portion of the list
* * * to the nonconfidential portion of that list.” 15 U.S.C.
§ 2607(b)(4)(B)(iv) (emphasis added).         And the statute
requires that those requests to maintain confidentiality had to
be filed “not later than 180 days after the date on which the
                              16
final rule is published in the Federal Register,” id.
§ 2607(b)(4)(A)(i)—that is, by February 7, 2018. That
approach leaves insufficient time for new applications for
confidentiality to be filed and acted upon before the previously
confidential chemical identity is publicly disclosed. And once
that disclosure occurs, the cat is out of the bag. There will be
no confidentiality for a new claimant to obtain. See id.
§ 2607(b)(8) (“No person may assert a new claim * * * for
protection from disclosure of a specific chemical identity of
any active or inactive substance * * * that is not on the
confidential portion of the [Inventory].”); see also S. REP. NO.
67, 114th Cong., 1st Sess. 24 (2015) (explaining that
“information that is * * * already publicly available cannot be
newly protected as [confidential] under [the Act]”).

     Environmental Defense finds that consequence
untroubling, reasoning that any company that had not already
claimed confidentiality for a chemical that it manufactures or
processes should be deemed to have forfeited the claim.
Environmental Defense Br. 40–41. But that ignores the
myriad circumstances in which it would have made no sense
for a company to submit its own confidentiality claim. For
instance, there would be no need for more than one
manufacturer in a co-manufacturing arrangement to submit a
confidentiality claim for the same chemical substance.
Likewise, an importer notified by a supplier that a chemical
already was on the confidential portion of the list would have
had no reason to submit a redundant claim. The EPA sensibly
determined that companies like those “legitimately benefit
from the confidential status of a specific chemical identity,”
and therefore should have the opportunity to seek
confidentiality going forward. 82 Fed. Reg. at 37,527.

     For all of those reasons, the EPA acted well within its
discretion in concluding that, as part of the Inventory update,
                                   17
any manufacturer or processor of a chemical substance can file
a claim to maintain the chemical substance’s confidentiality.

                                   3

     The Inventory Rule provides that information claimed to
be confidential “will be treated and disclosed in accordance
with 40 C.F.R. part 2, subpart B,” which regulates the EPA’s
treatment of confidential business information. 82 Fed. Reg.
at 37,543 (codified at 40 C.F.R. § 710.37(a)). 2 Environmental
Defense takes exception to that provision because the subpart
B regulations do not mirror all of the Control Act’s procedural
requirements.

     At the outset, the EPA and Industry again contest
Environmental Defense’s standing to make this claim. And
once again, they try to dress a merits argument in jurisdictional
garb. Environmental Defense is challenging provisions of the
Inventory Rule that it views as withholding information from
public disclosure. That is the same type of individualized and
direct informational injury that parties have standing to
challenge. See Friends of Animals, 824 F.3d at 1040–1041.

      Turning to the merits, Environmental Defense argues that
the Inventory Rule’s disclosure procedures unlawfully fail to
incorporate the Control Act’s requirements that the EPA (i)
review claims within ninety days, 15 U.S.C. § 2613(g)(1)(A);
(ii) inform the claimant of the EPA’s denial of a confidentiality
claim and allow only thirty days for appeal, id. § 2613(g)(2);
and (iii) publicly disclose any non-confidential aspects of its
confidentiality decisions, id. § 2625(j)(1).

    2
         40 C.F.R. part 2, subpart B is codified at 40 C.F.R. §§ 2.201–
2.311.
                               18

     That claim fails. Environmental Defense cites nothing in
the regulation that contradicts those statutory obligations. The
EPA acknowledges, as it must, that the Act “applies of its own
force,” EPA Br. 44, and nothing in the Inventory Rule
countermands or frustrates those statutory obligations. The
Inventory Rule’s provisions simply complement and elaborate
upon some of the statutory requirements without displacing the
others.

     Environmental Defense seems to want the statutory
requirements duplicated in the rule for duplication’s sake.
That is not necessary. “[A] regulation can never ‘trump the
plain meaning of a statute.’” Texas v. EPA, 726 F.3d 180, 195
(D.C. Cir. 2013) (quoting Atlantic City Elec. Co. v. FERC, 295
F.3d 1, 11 (D.C. Cir. 2002)). Should the EPA’s future
implementation of these provisions of the Inventory Rule fall
short of statutory mandates, a challenge can be raised then.
But there is nothing facially troubling about the failure to copy
every relevant statutory obligation into the regulation.

                               4

     Environmental Defense’s fourth objection to the Inventory
Rule is that it fails to implement the statutory scheme for
assigning a unique public identifier for each chemical identity
it decides to keep confidential. Environmental Defense points
to the Control Act’s requirement that the EPA “develop a
system to assign a unique identifier to each specific chemical
identity for which the Administrator approves a request for
protection from disclosure,” and then “apply that identifier
consistently to all information relevant to the applicable
chemical substance[.]” 15 U.S.C. § 2613(g)(4)(A)(i)–(ii).
The Control Act also directs the EPA to “annually publish and
update a list of chemical substances, referred to by their unique
                                 19
identifiers, for which claims to protect the specific chemical
identity from disclosure have been approved, including the
expiration date for each such claim[.]” Id. § 2613(g)(4)(B).

     There is no question that the Inventory Rule does not
implement those requirements. But the APA is patient. Or at
least more patient than Environmental Defense. Agencies
need not address all regulatory obligations “in one fell swoop.”
United States Telecom Ass’n v. FCC, 359 F.3d 554, 588 (D.C.
Cir. 2004). And nothing in the Control Act requires the EPA
to develop and implement the unique-identifier system
alongside its Inventory review process. Unlike the statutory
command to promulgate the Inventory Rule within a year, see
15 U.S.C. § 2607(b)(4)(A)(i), the Act establishes no deadline
for the EPA’s development and implementation of unique
identifiers, see id. § 2613(g)(4). And it is not unreasonable for
the EPA to defer that process while it first starts the process of
determining how many and which chemical substances will be
accorded confidential treatment. It is not for us to “second-
guess EPA’s decision to prioritize” those regulatory tasks.
WildEarth Guardians v. EPA, 751 F.3d 649, 656 (D.C. Cir.
2014). 3

     Environmental Defense separately complains that the EPA
failed to address its comment about implementing the unique
identifier system. To be sure, an agency’s “fail[ure] to
respond to major substantive comments” can render a decision

     3
       This is not a case in which the agency is sitting on its hands.
The EPA solicited comments “on approaches for assigning and
applying unique identifiers” before the final Inventory Rule was
promulgated, 82 Fed. Reg. 21,386 (May 8, 2017), solicited further
comments on “an additional approach” a few months later, 83 Fed.
Reg. 5623 (Feb. 8, 2018), and published its final policy
determination before briefing in this case concluded, 83 Fed. Reg.
30,168 (June 27, 2018).
                              20
arbitrary and capricious. Sierra Club v. EPA, 863 F.3d 834,
838 (D.C. Cir. 2017). At the same time, an agency need not
“discuss every item of fact or opinion included” in comments.
Public Citizen, Inc. v. FAA, 988 F.2d 186, 197 (D.C. Cir. 1993)
(quoting Automotive Parts & Accessories Ass’n v. Boyd, 407
F.2d 330, 338 (D.C. Cir. 1968)). Environmental Defense did
not submit “major substantive comments” requesting that the
EPA implement the unique identifier system during this
rulemaking. Sierra Club, 863 F.3d at 838. It merely
referenced unique identifiers as part of an “example” of
statutory requirements that are “broader than just Inventory
listings.” J.A. 22. Nothing in the APA saddles agencies with
the crushing task of responding to every single example cited
in every single comment, especially where, as here, the
reference is to a matter that the agency permissibly was not yet
regulating.

                               5

     Lastly, Environmental Defense objects to the exclusion of
export-only chemicals from the Inventory Rule’s requirement
that chemical companies notify the EPA of chemical
substances being manufactured or processed. We hold that
the EPA’s decision reflected a reasonable interpretation of the
Control Act.

    Under the Control Act, the EPA “shall require
manufacturers” and “may require processors” to “notify the
Administrator * * * of each chemical substance on the
[Inventory] that the manufacturer or processor * * * has
manufactured or processed for a nonexempt commercial
purpose during the 10-year period ending on the day before
June 22, 2016.” 15 U.S.C. § 2607(b)(4)(A)(i) (emphasis
added). Without any statutory guidance as to what counts as
a “nonexempt commercial purpose,” the agency concluded it
                              21
was consistent with the Control Act to exclude, among other
things, “[t]he manufacturing or processing of a chemical
substance solely for export from the United States * * *.” 82
Fed. Reg. 37,541 (codified at 40 C.F.R. § 710.27(a)(4)).

     Environmental Defense insists that the statute itself
declares exports to be a “nonexempt commercial purpose”
because Section 2611, which applies specifically to exports,
says that “this chapter (other than section 2607 of this title)
shall not apply to any chemical substance, mixture, or to an
article containing a chemical substance or mixture” that is
manufactured or processed for export. 15 U.S.C. § 2611(a)(1)
(emphasis added).      As Environmental Defense sees it,
Congress’s decision to carve regulation under Section 2607 out
of the statute’s otherwise-broad exemption for exported
chemicals means that Congress intended for Section 2607 to
apply to exports.

     We agree with Environmental Defense that the upshot of
Section 2611 is that Section 2607 “shall * * * apply” to
chemicals for export. But what does it mean to “apply” 15
U.S.C. § 2607—a nearly four thousand-word chunk of the
statute—to exported chemicals? Congress did not say.

     In light of this congressional silence, the Rule’s narrow
excision of exports from one reporting requirement passes
muster. See Chevron, 467 U.S. at 843. The EPA explained
that Section 2611 insulates export chemicals from numerous
other statutory requirements, including prospective reporting
requirements under 15 U.S.C. § 2604. 82 Fed. Reg. at 37,528;
see 15 U.S.C. § 2611(a)(1) (providing that “this chapter,”
including § 2604, “shall not apply to” export-only chemicals);
id. § 2604(a) (imposing prospective notification requirements);
id. § 2607(b)(1) (“[The Inventory] shall at least include each
chemical substance which any person reports, under section
                             22
2604 of this title or subsection (a) of this section, is
manufactured or processed in the United States.”). So all the
EPA did here is exempt those same export chemicals from the
Act’s retrospective reporting requirements in Section 2607.
See 15 U.S.C. § 2607(b)(4)(A)(i). To decide otherwise would
have made compliance more onerous for previous
manufacturers of exported chemicals than for future
manufacturers of exported chemicals. Whatever Congress
meant by the cross-reference to Section 2607 in Section 2611,
the EPA reasonably concluded it was not to impose that
illogical regulatory construct.

     Nor did the EPA fail to provide sufficient notice in the
Notice of Proposed Rulemaking that export-only chemicals
would be excluded from the statute’s definition of “nonexempt
commercial purpose.” See Environmental Defense Br. 57.
The Notice advised that the EPA intended to define
“nonexempt commercial purpose” consistently with the
“commonly-accepted usage” of that phrase at the time the
Control Act was amended. 82 Fed. Reg. at 4259. Two of the
three legal sources the agency cited for that common usage—
15 U.S.C. § 2604 and 40 C.F.R. § 720.30—exempt export-only
chemicals from reporting requirements. Id. Unsurprisingly,
then, the agency received several comments requesting that it
add the export-only exemption that was missing from the
proposed rule.      See, e.g., J.A. 47 (Fertilizer Institute
comments); J.A. 68 (Biobased and Renewable Products
Advocacy Group comments); J.A. 89 (Vinyl Institute
comments); J.A. 118 (Pine Chemicals Association
International comments). Environmental Defense, like those
other commenters, “should have anticipated that the change
was possible, and thus reasonably should have filed their
comments on the subject during the notice-and-comment
period.” CSX Transp., Inc. v. Surface Transp. Bd., 584 F.3d
1076, 1079–1080 (D.C. Cir. 2009) (formatting altered).
                               23

                           *****

     For all of those reasons, we order a limited remand,
without vacatur, for the EPA to address its arbitrary elimination
of substantiation questions regarding reverse engineering. We
otherwise deny the petition for review.

                                                    So ordered.
