Court Opinion

ID: 4682396
Source: CourtListenerOpinion
Date Created: 2021-04-29 17:00:44.588618+00
Date Added: 2024-06-11T08:04:08.467505
License: Public Domain

FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

LEAGUE OF UNITED LATIN                No. 19-71979
AMERICAN CITIZENS; PESTICIDE
ACTION NETWORK NORTH AMERICA;            EPA No.
NATURAL RESOURCES DEFENSE             EPA-HQ-OPP-
COUNCIL; CALIFORNIA RURAL               2007-1005
LEGAL ASSISTANCE FOUNDATION;
FARMWORKERS ASSOCIATION OF
FLORIDA; FARMWORKER JUSTICE;
LABOR COUNCIL FOR LATIN
AMERICAN ADVANCEMENT;
LEARNING DISABILITIES
ASSOCIATION OF AMERICA;
NATIONAL HISPANIC MEDICAL
ASSOCIATION; PINEROS Y
CAMPESINOS UNIDOS DEL NOROESTE;
UNITED FARM WORKERS;
GREENLATINOS,
                       Petitioners,

                v.

MICHAEL S. REGAN, Administrator,
United States Environmental
Protection Agency; U.S.
ENVIRONMENTAL PROTECTION
AGENCY,
                       Respondents.
2   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

STATE OF NEW YORK; STATE OF              No. 19-71982
CALIFORNIA; STATE OF
WASHINGTON; STATE OF                       EPA No.
MARYLAND; STATE OF VERMONT;             EPA-HQ-OPP-
COMMONWEALTH OF                           2007-1005
MASSACHUSETTS,
                      Petitioners,
                                          OPINION
DISTRICT OF COLUMBIA; STATE OF
HAWAII; STATE OF OREGON,
                      Intervenors,

                v.

MICHAEL S. REGAN, Administrator,
United States Environmental
Protection Agency; U.S.
ENVIRONMENTAL PROTECTION
AGENCY,
                       Respondents.

       On Petition for Review of an Order of the
          Environmental Protection Agency

         Argued and Submitted July 28, 2020
             San Francisco, California

                 Filed April 29, 2021
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                 3

 Before: Jay S. Bybee and Jacqueline H. Nguyen, Circuit
        Judges, and Jed S. Rakoff, * District Judge.

                    Opinion by Judge Rakoff;
                     Dissent by Judge Bybee

                          SUMMARY **

             Environmental Protection Agency

    The panel granted petitions for review, vacated the
Environmental Protection Agency (“EPA”)’s 2017 Order
and 2019 Order, and remanded with instructions to the EPA
in cases challenging the EPA’s regulation of the pesticide
chlorpyrifos.

    The EPA has recognized that when pregnant mothers are
exposed to chlorpyrifos residue, this likely harms infants in
utero.    This proceeding began in 2007, when two
environmental non-profit organizations filed a petition
asking the EPA to prohibit foods that contain residue of the
insecticide chlorpyrifos. The EPA declined to take final
action on the 2007 Petition for more than a decade. This
Court issued multiple writs of mandamus requiring the EPA
to move forward. In 2017, the EPA denied the 2007 Petition,
and in 2019 denied all objections to that decision.

    *
     The Honorable Jed S. Rakoff, United States District Judge for the
Southern District of New York, sitting by designation.
    **
       This summary constitutes no part of the opinion of the court. It
has been prepared by court staff for the convenience of the reader.
4    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

    The panel held that the EPA had abdicated its statutory
duty under the Federal Food, Drug and Cosmetic Act
(“FFDCA”). The panel held that the EPA spent more than a
decade assembling a record of chlorpyrifos’s ill effects and
repeatedly determined, based on that record, that it could not
conclude, to the statutorily required standard of reasonable
certainty, that the present tolerances caused no harm. Rather
than ban the pesticide or reduce the tolerances to levels that
the EPA could find were reasonably certain to cause no
harm, the EPA sought to evade through delay tactics its plain
statutory duty. Because the FFDCA permitted no further
delays, the panel ordered the EPA within 60 days after
issuance of the mandate either to modify chlorpyrifos’s
tolerances and concomitantly publish a finding that the
modified tolerances are safe, including for infants and
children – or to revoke all chlorpyrifos tolerances. The panel
also ordered the EPA to correspondingly modify or cancel
related Federal Insecticide, Fungicide and Rodenticide Act
(“FIFRA”) regulations for food use in a timely fashion
consistent with the requirements of 21 U.S.C. § 346a(a)(1).

    Specifically, the panel first considered whether the EPA
lawfully denied the 2007 Petition. The panel rejected the
EPA’s argument that it could leave in effect tolerances,
without a new safety finding, when the EPA concluded the
petition contained insufficient evidence for the EPA to
undertake proceedings to revoke or modify tolerances. The
panel held, first, once the EPA became aware, through a
petition or otherwise, of genuine questions about the safety
of an existing tolerance, the EPA had its own continuing
duty under the FFDCA to determine whether a tolerance that
was once thought to be safe still is. Here, the EPA’s own
studies and pronouncements still in effect showed that it
regarded chlorpyrifos as harmful at levels below the existing
tolerances. Second, the 2007 Petition, under the EPA’s own
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN            5

regulations, contained more than sufficient evidence to
undertake a safety review, and the EPA recognized as much.
The panel held that when the EPA publishes a petition
seeking revocation of a tolerance and later takes final action
denying that petition, the EPA leaves that tolerance in effect.
The EPA can only do so if it finds the tolerance to be safe
for the general population and for infants and children. The
EPA failed to make such findings, directly contrary to the
FFDCA.

    The panel held that even if the FFDCA did not require a
safety finding here, the EPA’s denial of the 2007 Petition
was arbitrary and capricious. The panel rejected the EPA’s
four objections to the data.

    The panel held that its remand with specific instructions
did not raise due process concerns. On this record,
immediate issuance of a final regulation was the only
reasonable action, and the panel ordered the EPA to do so.
The panel clarified that this was not an open-ended remand,
or a remand for further factfinding.

     Dissenting, Judge Bybee wrote that the majority opinion
erred by misreading the FFDCA, and misallocating the risk
of nonpersuasion; overruling the EPA’s judgment on the
validity and weight to be given technical evidence within the
EPA’s expertise; and, by its decision to give the EPA 60 days
to issue a final decision, likely predetermining EPA’s option.
6    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

                        COUNSEL

Patti A. Goldman (argued), Marisa C. Ordonia, and Kristen
L. Boyles, Earthjustice, Seattle, Washington, for Petitioners
League of United Latin American Citizens, Pesticide Action
Network North America, Natural Resources Defense
Council, California Rural Legal Assistance Foundation,
Farmworkers Association of Florida, Farmworker Justice,
Labor Council for Latin American Advancement, Learning
Disabilities Association of America, National Hispanic
Medical Association, Pineros y Campesinos Unidos del
Noroeste, United Farm Workers, and GreenLatinos.

Frederick A. Brodie (argued), Assistant Solicitor General Of
Counsel; Andrea Oser, Deputy Solicitor General; Barbara D.
Underwood, Solicitor General; Letitia James, Attorney
General; Office of the Attorney General, Albany, New York;
Xavier Becerra, Attorney General; Christie Vosburg,
Supervising Deputy Attorney General; Reed Sato, Deputy
Attorney General; Office of the Attorney General,
Sacramento, California; Robert W. Ferguson, Attorney
General; William R. Sherman, Counsel for Environmental
Protection; Attorney General’s Office, Seattle, Washington;
Brian E. Frosh, Attorney General; Steven M. Sullivan,
Solicitor General; Joshua M. Segal, Special Assistant
Attorney General; Office of the Attorney General,
Baltimore, Maryland; Thomas J. Donovan Jr., Attorney
General; Nichols F. Persampieri, Assistant Attorney
General; Office of the Attorney General, Montpelier,
Vermont; Clare E. Connors, Attorney General; Wade H.
Hargrove III, Deputy Attorney General; Department of the
Attorney General, Honolulu, Hawaii; Ellen F. Rosenblum,
Attorney General; Benjamin Gutman, Solicitor General;
Office of the Attorney General, Salem, Oregon; Maura
Healey, Attorney General; I. Andrew Goldberg, Assistant
    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN         7

Attorney General; Environmental Protection Division,
Office of the Attorney General, Boston, Massachusetts; Karl
A. Racine, Attorney General; Loren L. Alikhan Solicitor
General; Caroline S. Van Zile, Principal Deputy Solicitor
General; Brian R. Caldwell, Assistant Attorney General,
Public Integrity Unit; Office of the Attorney General,
Washington, D.C.; for Petitioners States of New York,
California, Washington, Maryland, Vermont, Hawaii,
Oregon, the Commonwealth of Massachusetts, and the
District of Columbia.

Mark L. Walters (argued) and Jessica O’Donnell,
Environmental Defense Section, United States Department
of Justice, Washington, D.C.; Angela Huskey, Office of
General Counsel, United States Environmental Protection
Agency, Washington, D.C.; for Respondents.

Shaun A. Goho, Emmett Environmental Law & Policy
Clinic, Harvard Law School, Cambridge, Massachusetts, for
Amici Curiae American Academy of Pediatrics, Alliance of
Nurses for Healthy Environments, American Public Health
Association, Migrant Clinicians Network, Physicians for
Social Responsibility, and Union of Concerned Scientists.

Edward Lloyd, Jacob Elkin, Claire MacLachlan, and Basil
Oswald, Columbia Environmental Clinic, Morningside
Heights Legal Services, New York, New York, for Amicus
Curiae Congressman Henry Waxman.

Kathryn E. Szmuszkovicz and Andrew C. Stilton, Beveridge
& Diamond P.C., Washington, D.C.; Rachel Lattimore,
Senior Vice President & General Counsel; Ashley Boles,
Counsel; CropLife America, Washington, D.C.; for Amicus
Curiae CropLife America.
8    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

David Y. Chung, Kirsten L. Nathanson, and Elizabeth B.
Dawson, Crowell & Moring LLP, Washington, D.C., for
Amici Curiae Agribusiness Council of Indiana, Agricultural
Retailers Association, American Farm Bureau Federation,
AmericanHort, American Seed Trade Association,
American Soybean Association, American Sugarbeet
Growers Association, Beet Sugar Development Foundation,
California Alfalfa and Forage Association, California Citrus
Mutual, California Cotton Ginners and Growers
Association, California Seed Association, California
Specialty Crops Council, California Walnut Commission,
Florida Fruit and Vegetable Association, National
Agricultural Aviation Association, National Association of
Wheat Growers, National Corn Growers Association,
National Cotton Council, National Onion Association,
National Sorghum Producers, North Dakota Grain Growers
Association, Oregonians for Food and Shelter, Washington
Friends of Farms & Forests, Western Agricultural
Processors Association, Western Growers, and Western
Plant Health Association.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN             9

                          OPINION

RAKOFF, District Judge:

    This dispute concerning the documented health risks
posed by a widely used pesticide, chlorpyrifos, has been
before this Court more than a half-dozen times. The
Environmental Protection Agency (“EPA” or the “Agency”)
has recognized that when pregnant mothers are exposed to
chlorpyrifos residue, this likely harms infants in utero.
Nevertheless, in derogation of the statutory mandate to ban
pesticides that have not been proven safe, the EPA has failed
to act, requesting extension after extension. The Agency’s
present position is effectively more of the same.

    The proceeding began in 2007, when two environmental
non-profit organizations – Pesticide Action Network North
America (“PANNA”) and the Natural Resources Defense
Council, Inc. (“NRDC”) – filed a petition (the “2007
Petition”) asking the EPA to prohibit foods that contain any
residue of the insecticide chlorpyrifos. Then, and now, the
EPA has permitted distribution of food containing
chlorpyrifos residue as long as the residue is less than a limit
known as a “tolerance,” which varies depending on the food.
The 2007 Petition argued that, even at levels beneath these
tolerances, chlorpyrifos poses neurodevelopmental risks,
especially to infants and children.

    The Federal Food, Drug and Cosmetic Act (“FFDCA”)
provides that the EPA’s “Administrator may establish or
leave in effect a tolerance for a pesticide chemical residue in
or on a food only if the Administrator determines that the
tolerance is safe. The Administrator shall modify or revoke
10       LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

a tolerance if the Administrator determines it is not safe.” 1
The statute also requires that the EPA “ensure that there is a
reasonable certainty that no harm will result to infants and
children from aggregate exposure to the pesticide chemical
residue” and “publish a specific determination regarding the
safety of the pesticide chemical residue for infants and
children.” 2

    Since 2007, the evidence of harm has continued to build,
primarily through two kinds of studies: experimental studies
on live mice and rats and epidemiological studies tracking
humans who were exposed to chlorpyrifos in utero.
Between 2007 and 2016, the EPA published several Human
Health Risk Assessments regarding chlorpyrifos and
convened its Scientific Advisory Panel (“SAP”) several
times. Those assessments and SAP reviews increasingly
recognized the persuasiveness of the studies showing
chlorpyrifos’s risks. Nevertheless, the EPA declined to take
final action on the 2007 Petition for more than a decade.
Eventually, PANNA, NRDC, and others sought judicial
relief, and this Court issued multiple writs of mandamus
requiring the EPA to move forward. But, festina lente, the
EPA continued to delay ruling on the 2007 Petition. This,
moreover, was despite the fact that in November 2015, the
EPA published a Notice of Proposed Rulemaking that
proposed to revoke all chlorpyrifos tolerances because the
EPA could not find them to be safe. Similarly, in 2016, the
EPA issued a Revised Human Health Risk Assessment

     1
         21 U.S.C. § 346a(b)(2)(A)(i).
     2
         Id. § 346a(b)(2)(C)(i)–(ii).
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN               11

finding that the present tolerances are “not sufficiently health
protective.” 3

    In 2017, the EPA, pursuant to a court-set deadline,
finally ruled on the 2007 Petition. But in the very face of its
own prior acknowledgements of the health risks posed by
chlorpyrifos, the EPA denied the 2007 Petition, and in 2019
denied all objections to that decision. In reality, however,
this was just one more attempt at delay, because the EPA did
not conclude that the tolerances were safe, but simply denied
the Petition on the ground that the EPA would forgo further
consideration of the question of safety until chlorpyrifos
underwent a registration re-review under a separate statute,
which could be as late as 2022. As explained below, this
delay tactic was a total abdication of the EPA’s statutory
duty under the FFDCA.

    In short, the EPA has spent more than a decade
assembling a record of chlorpyrifos’s ill effects and has
repeatedly determined, based on that record, that it cannot
conclude, to the statutorily required standard of reasonable
certainty, that the present tolerances are causing no harm.
Yet, rather than ban the pesticide or reduce the tolerances to
levels that the EPA can find are reasonably certain to cause
no harm, the EPA has sought to evade, through one delaying
tactic after another, its plain statutory duties. The FFDCA
permits no further delay. Accordingly, for the reasons that
follow, the Court grants the petitions for review and orders
the EPA within 60 days after the issuance of the mandate
either to modify chlorpyrifos tolerances and concomitantly
publish a finding that the modified tolerances are safe,

    3
      Chlorpyrifos; Tolerance Revocations; Notice of Data Availability
and Request for Comment, 81 Fed. Reg. 81,049, 81,050 (Nov. 17, 2016)
(hereinafter “2016 Notice of Data Availability”).
12       LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

including for infants and children – or to revoke all
chlorpyrifos tolerances. The Court also orders the EPA to
correspondingly modify or cancel related FIFRA
registrations for food use in a timely fashion consistent with
the requirements of 21 U.S.C. § 346a(a)(1).

                             BACKGROUND

I. The EPA’s Duty to Regulate Pesticides

    Congress requires the EPA to regulate the use of
pesticides on food pursuant to the FFDCA. Congress also
requires the EPA to regulate the use of pesticides more
generally under the Federal Insecticide, Fungicide and
Rodenticide Act (“FIFRA”). This case principally concerns
the FFDCA.

    The FFDCA begins with a general rule that food
containing pesticide residue is unsafe and prohibited. 4
Congress empowered the EPA to make exceptions to that
rule by promulgating “tolerances” for a pesticide – i.e.,
threshold levels of pesticide residue that the EPA is
reasonably certain will cause no harm. 5 If the EPA
promulgates a tolerance for a pesticide, then food may
contain residue of that pesticide in an amount not exceeding
the applicable tolerance. 6

    The EPA’s discretion to set such tolerances is
circumscribed, however, by an uncompromisable limitation:

     4
      Id. §§ 331, 342(a)(2)(B), 346a(a)(1). The FFDCA applies only to
food and other products in interstate commerce. See 21 U.S.C. § 331.
     5
         Id. § 346a(b)(1), (b)(2)(A).
     6
         Id. § 346a(a)(4).
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN          13

the pesticide must be determined to be safe for human
beings. The EPA “may establish or leave in effect a
tolerance for a pesticide chemical residue in or on a food only
if the Administrator determines that the tolerance is safe.” 7
Furthermore, following enactment of the Food Quality
Protection Act of 1996 (“FQPA”), it is now clear that the
EPA must look beyond food to consider all of the ways
someone might be exposed to a pesticide, “including all
anticipated dietary exposures and all other exposures for
which there is reliable information.” 8 The EPA can
determine that a tolerance is safe only if “there is a
reasonable certainty that no harm will result from aggregate
exposure to the pesticide chemical residue.” 9

     In addition to requiring this general safety finding, the
FFDCA also conditions the EPA’s authority to set or leave
in effect a tolerance on its determination that the tolerance is
safe for infants and children. “In establishing, modifying,
leaving in effect, or revoking a tolerance . . . , the
Administrator . . . shall . . . ensure that there is a reasonable
certainty that no harm will result to infants and children from
aggregate exposure to the pesticide chemical residue,” and
shall “publish a specific determination regarding the safety
of the pesticide chemical residue for infants and children.” 10
If a tolerance is not safe – in other words, if the EPA cannot
determine that there is a reasonable certainty of no harm
across all sources of exposure for infants, children, and
adults – then the EPA no longer has discretion. Rather, the
    7
        Id. § 346a(b)(2)(A)(i) (emphasis added).
    8
        Id. § 346a(b)(2)(A)(ii).
    9
        Id. (emphases added).
    10
         Id. § 346a(b)(2)(C)(ii).
14    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

law commands that the EPA “shall modify or revoke [the]
tolerance.” 11

    The FFDCA authorizes “[a]ny person [to] file . . . a
petition proposing the issuance of a regulation establishing,
modifying, or revoking a tolerance.” 12 The EPA, by
regulation, may dictate what a petition seeking revocation of
a tolerance must contain. 13 Pursuant to that authority, the
EPA requires that a petition state “reasonable grounds for the
action sought,” including “an assertion of facts.” 14 If the
EPA determines that a petition has met the threshold
requirements, then it must publish the petition within
30 days. 15 “[A]fter giving due consideration to a petition . . .
and any other information available to the Administrator,”
the EPA “shall” do one of three things: “issue a final
regulation (which may vary from that sought by the petition)
establishing, modifying, or revoking a tolerance . . . (which
final regulation shall be issued without further notice and
without further period for public comment),” “issue a
proposed regulation . . . and thereafter issue a final
regulation,” or “issue an order denying the petition.” 16 If the
EPA denies a petition, “any person may file objections

     11
          Id. § 346a(b)(2)(A)(i).
     12
          Id. § 346a(d)(1).
     13
          Id. § 346a(d)(2)(B).
     14
          40 C.F.R. § 180.32(b).
     15
          21 U.S.C. § 346a(d)(3).
     16
          Id. § 346a(d)(4)(A).
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN              15

thereto with the Administrator.” 17 The Administrator “shall
issue an order stating the action taken upon each . . .
objection” “[a]s soon as practicable.” 18 Those affected may
seek “judicial review . . . in the United States Court of
Appeals.” 19

     Separately, the EPA also regulates pesticides pursuant to
FIFRA. Under FIFRA, pesticides must be registered by the
EPA before they can be distributed or sold. 20 To register a
pesticide, the EPA must determine, among other things, that
it does not have “unreasonable adverse effects on the
environment.” 21 FIFRA defines “unreasonable adverse
effects” to include “a human dietary risk from residues that
result from a use of a pesticide in or on any food inconsistent
with” the standards of the FFDCA. 22 In other words, FIFRA
incorporates the FFDCA safety standard for food uses,
among other considerations. FIFRA requires the EPA to
reevaluate pesticides as part of a registration review every
fifteen years. 23

   17
        Id. § 346a(g)(2)(A).
   18
        Id. § 346a(g)(2)(C).
   19
        Id. § 346a(h)(1).
   20
        See 7 U.S.C. § 136a(a).
   21
        Id. § 136a(c)(5)(C)–(D).
   22
        Id. § 136(bb).
   23
        See id. §§ 136a(c)(1)(F)(iii), (g)(1)(A), 136a-1(a).
16    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

II. This Administrative            Proceeding        and     Related
    Litigation

    This administrative proceeding began with the filing of
the 2007 Petition, which sought revocation of all tolerances
and registrations for chlorpyrifos. Chlorpyrifos is an
organophosphate pesticide. Organophosphates were first
developed as toxic nerve agents for potential use in chemical
warfare during World War II, and chlorpyrifos was initially
registered as a pesticide in the United States in 1965. Since
then, farmers have used chlorpyrifos to protect dozens of
types of crops. As of 2017, “[b]y pounds of active
ingredient, it [was] the most widely used conventional
insecticide in the country.” 24 Nevertheless, in 2019,
California (and the European Union) announced they would
ban the sale of chlorpyrifos. 25

    Chlorpyrifos      disrupts   the      functioning    of
acetylcholinesterase (“AChE”), a crucial enzyme that breaks
down the neurotransmitter acetylcholine. 26 In setting

     24
       Chlorpyrifos; Order Denying PANNA and NRDC’s Petition to
Revoke Tolerances, 82 Fed. Reg. 16,581, 16,584 (Apr. 5, 2017)
(hereinafter “2017 Order”).
     25
       Press Release, Cal. Env’t Prot. Agency & Cal. Dep’t of Pesticide
Regul., Agreement Reached to End Sale of Chlorpyrifos in California
by February 2020 (Oct. 9, 2019), https://www.cdpr.ca.gov/docs/pressrl
s/2019/100919.htm; Stephen Gardner, EU to Ban Chlorpyrifos Pesticide
Starting in February, Bloomberg L. News (Dec. 6, 2019, 6:43 AM),
https://news.bloomberglaw.com/environment-and-energy/eu-to-ban-
chlorpyrifos-pesticide-starting-in-february.
    26
       See EPA, Office of Prevention, Pesticides, and Toxic Substances,
EPA 738-R-01-007, Interim Reregistration Eligibility Determination for
Chlorpyrifos 2 (Feb. 2002) (“Chlorpyrifos can cause [AChE] inhibition
in humans; that is, it can overstimulate the nervous system causing
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                   17

chlorpyrifos tolerances, the EPA must determine the greatest
exposure amount that poses no risk of harm, which is known
as a “point of departure.” Since enactment of the FQPA, the
EPA has tied the chlorpyrifos point of departure directly to
acute AChE inhibition, finding that exposure to chlorpyrifos
residue on food would be unsafe if aggregate exposure
across all sources caused more than 10% acute AChE
inhibition.

    However, for decades, the EPA has itself expressed
concerns that chlorpyrifos might also be causing harm
through a different mechanism: neurotoxic effects that are
especially harmful to infants and children. 27 The 2007
Petition was partly based on these concerns. Yet, despite the
EPA’s expressed concerns, the EPA repeatedly failed to act
on the 2007 Petition until this Court compelled it to do so.
The following is a chronological summary both of the EPA’s
assessment of chlorpyrifos’s safety and of this dispute.

    A. 2000–2006: The EPA Finds Certain Chlorpyrifos
       Tolerances Safe, Despite Concerns

    Between 2000 and 2006, even before the Petition was
filed, the EPA began taking steps to reduce exposure to
chlorpyrifos as part of its reevaluation of chlorpyrifos’s
safety, as required by the FQPA. The FQPA imposed the
requirements, still included in the FFDCA today, that the

nausea, dizziness, confusion, and at very high exposures (e.g., accidents
or major spills), respiratory paralysis and death.”).
    27
        This different mechanism of harm might still relate to AChE
inhibition; the EPA has considered the possibility that chronic AChE
inhibition at levels of less than 10% might cause permanent damage.
Herein, unless stated otherwise, AChE inhibition means acute AChE
inhibition of 10% or more.
18    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

EPA (1) consider proof of safety as an absolute prerequisite
to establishing or leaving in effect a tolerance, without
balancing it against other factors; (2) assess a pesticide’s
cumulative exposure from multiple sources (e.g., drinking
water as well as food); and (3) specifically assess the
pesticide’s potential risks to children. The FQPA also
required the EPA to reassess the safety of all then-authorized
pesticides using this new standard.

    During this period, the EPA began to express concerns
that chlorpyrifos might be causing harms through a
mechanism other than AChE inhibition. For example, in a
2000 Human Health Risk Assessment, the EPA recognized
that studies had preliminarily shown that AChE inhibition
might not be the only mechanism of harm. 28

    The EPA also began acting on its concerns about
chlorpyrifos safety, in collaboration with the pesticide
industry. In 2000, the EPA and the chlorpyrifos technical
registrants entered into an agreement regarding chlorpyrifos
that eliminated or phased out its use for virtually all
residential and termiticide purposes, and on tomatoes and,
during the growing season, grapes and apples. 29 In 2002, the

     28
        EPA, Office of Pesticide Programs, Human Health Risk
Assessment-Chlorpyrifos 4 (June 8, 2000), https://archive.epa.gov/scip
oly/sap/meetings/web/pdf/hed_ra.pdf (discussing live animal studies and
explaining that “new data in the literature also gave rise to uncertainties
such as the suggestion that the inhibition of [AChE] may not be essential
for adverse effects on brain development”).

      Letter to Aaron Colangelo, NRDC, & Margaret Reeves, PANNA,
     29

from Steven Bradbury, EPA, re: Chlorpyrifos Petition Dated September
12, 2007 (hereinafter “2007 Petition”), at 6 (July 16, 2012).
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                    19

EPA announced certain risk mitigation measures, especially
for people exposed to chlorpyrifos through their work. 30

    Subject to these changes, however, the EPA determined
in February 2002, based upon the evidence then available,
that “[d]ietary exposures from eating food crops treated with
chlorpyrifos are below the level of concern for the entire
U.S. population, including infants and children,” and that
“[d]rinking water risk estimates . . . are generally not of
concern.” 31 The EPA reiterated its safety finding in July
2006, stating that chlorpyrifos tolerances “meet the safety
standard under Section 408(b)(2) of the FFDCA.” 32

    B. 2007: PANNA and NRDC File a Petition to Revoke
       Tolerances, Citing Mounting Evidence of Harm

    In September 2007, PANNA and NRDC filed an
administrative petition with the EPA seeking revocation of
all chlorpyrifos tolerances under the FFDCA and the
cancellation of all of chlorpyrifos’s FIFRA registrations.
The 2007 Petition asserted that scientific evidence now
available showed that the current chlorpyrifos tolerances
were not safe, especially for infants and children; indeed,
they argued, “no safe level of early-life exposure to

    30
       Interim Reregistration Eligibility Decision for Chlorpyrifos, supra
note 26.
    31
         Id. at 2.
    32
        EPA, Office of Prevention, Pesticides and Toxic Substances,
Memo to Jim Jones from Debra Edwards, Finalization of Interim
Reregistration Eligibility Decisions and Interim Tolerance Reassessment
and Risk Management Decisions for the Organophosphate Pesticides,
and Completion of the Tolerance Reassessment and Reregistration
Eligibility Process for the Organophosphate Pesticides 2 (July 31, 2006).
20       LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

chlorpyrifos can be supported.” 33 They cited “[m]any
studies published since 2001 [that] report that fetal exposure
to chlorpyrifos is more damaging than adult exposure.” 34

    The 2007 Petition relied in part upon certain experiments
performed on live mice and rats. They were exposed in utero
to levels of chlorpyrifos below those previously known to
cause AChE inhibition. The scientists found marked
declines in thinking and movement, indicative of
neurological effects. The declines were sex-linked, harming
males more than females.

    The 2007 Petition also relied upon an epidemiological
study, known as the “Columbia Study.” Researchers worked
with a cohort of pregnant women and their children,
collecting data on the mothers’ organophosphate exposure
(including chlorpyrifos) during pregnancy, and then
following the development of the children for many years.
Some of the participating children were born before the EPA
and the registrants agreed to end residential use of
chlorpyrifos, and others were born after. Over time, the
researchers found a correlation between prenatal
chlorpyrifos exposure and several negative outcomes:

     •      at age three, lower performance in motor and mental
            development tests and higher incidences of attention-
            deficit hyperactivity disorder and autism spectrum
            disorder;

      Marc S. Wu et al., NRDC, & Susan E. Kegley, PANNA, Petition
     33

to Revoke All Tolerances and Registrations for the Pesticide
Chlorpyrifos 5 (Sept. 12, 2007).
     34
          Id. at 6.
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN           21

    •     at age seven, changes in brain morphology and lower
          IQ scores; and

    •     at age eleven, a greater likelihood of mild or
          moderate tremors.

Like the live animal experiments, the Columbia Study found
that in utero exposures were harmful even beneath the levels
thought to cause notable AChE inhibition and that harms
were sex-linked, disproportionately affecting boys.

    Two other groups of researchers also conducted
epidemiological studies similar to the Columbia Study (the
“Mount Sinai Study” and the “CHAMACOS Study”;
collectively with the Columbia Study, the “Human Cohort
Studies”). The Mount Sinai and CHAMACOS Studies
looked at exposure to organophosphate pesticides and, like
the Columbia Study, found a correlation between prenatal
organophosphate exposure and cognitive impairments in
early childhood. 35

    C. 2008–2011:      The EPA Preliminarily Links
       Chlorpyrifos to Neurotoxic Harms in Infants and
       Children

    Within a year of the 2007 Petition, the EPA, in August
2008, published a Science Issue Paper, which reviewed
existing scientific studies and “preliminarily concluded that
chlorpyrifos likely played a role” in the low birth rate and
delays in infant mental development observed in the Human

    35
      Although the Mount Sinai Study and the CHAMACOS Study
were not cited in the 2007 Petition, they later became part of the
administrative record.
22    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

Cohort Studies. 36 The EPA recognized that some of these
studies found these effects despite lesser AChE inhibition,
suggesting there was a different mechanism of harm. 37
However, the paper also noted that it was “not a full and
complete risk assessment/characterization,” and that the
EPA “ha[d] not developed any final conclusions regarding
updates to the chlorpyrifos hazard assessment.” 38

    In September 2008, the EPA convened a committee of
experts known as a Scientific Advisory Panel (“SAP”) to
peer-review its findings. The 2008 SAP considered “the
results of the three [Human Cohort Studies] (with an
emphasis on the Columbia [S]tudy) . . . along with the
findings from experimental studies in animals,” and
concluded that “maternal chlorpyrifos exposure would likely
be associated with adverse neurodevelopmental outcomes in
humans.” 39 The SAP “agreed with [the EPA’s] conclusion
that chlorpyrifos likely played a role in the birth and
neurodevelopmental outcomes noted in the three [Human
Cohort Studies].” 40

    36
       Health Effects Division, Office of Pesticide Programs, EPA,
Science Issue Paper: Chlorpyrifos Hazard and Dose Response
Characterization 52 (Aug. 21, 2008).
     37
          Id. at 40–41 & fig.5.
     38
          Id. at 7.
     39
       SAP Minutes No. 2008-04, A Set of Scientific Issues Being
Considered by the Environmental Protection Agency Regarding: The
Agency’s Evaluation of the Toxicity Profile of Chlorpyrifos 13 (Sept.
16–18, 2008) (hereinafter “2008 SAP Minutes”).
     40
          Id. at 37.
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                     23

    However, the SAP also posited that the effects might not
be entirely attributable to chlorpyrifos; rather, they might
also reflect exposure to other AChE-inhibiting insecticides.
A majority of SAP members agreed that the adverse
outcomes of the Columbia Study were concerning,
especially “in light of evidence demonstrating that low levels
of exposure to toxicants once thought to have adverse
neurodevelopmental effects only at high levels (i.e. lead,
mercury, and PCBs) are now known to produce significant
effects at lower levels.” 41 Nevertheless, the 2008 SAP found
that the Human Cohort Studies had “utility for risk
characterization, but not as the principal basis for
establishing the point of departure.” 42

    About three years later, in 2011, the EPA published a
Preliminary Human Health Risk Assessment. The EPA
discussed the three Human Cohort Studies and noted the
2008 SAP’s conclusion that those studies, “in concert with
the animal studies[,] indicate that ‘maternal chlorpyrifos
exposure would likely be associated with adverse

    41
         Id. at 43–44.
    42
       2007 Petition, supra note 29, at 6–7. The Dissent notes that the
2008 SAP expressed “concerns that the Columbia Study—the most
robust of the three—did not provide sufficient data to be the sole factor
for risk assessment or modifying tolerances and produced uncertainty
through its measurement method.” Dissent, infra, at 91. In fact,
although the 2008 SAP recognized that “there were limitations . . . that
precluded [the Human Cohort Studies] from being used to directly derive
the [point of departure] or the uncertainty factor,” it also concluded that
the Columbia Study “could be used to determine bounding values for the
levels of chlorpyrifos that might cause a measurable effect.” 2008 SAP
Minutes, supra note 39, at 46. Thus, even as early as 2008, the SAP
recognized the utility of the Columbia Study for risk assessment.
24    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

neurodevelopmental outcomes in humans.’” 43 While the
Preliminary Human Health Risk Assessment asserted that
the EPA could not yet identify the mechanism of action for
neurotoxic harm, nevertheless, it viewed the Human Cohort
Studies favorably, describing the Columbia Study as a
“natural experiment” since some participants were pregnant
before the EPA banned residential use of chlorpyrifos and
some were pregnant after the ban. 44 The EPA “intend[ed] to
carefully consider the strengths and limitations of the
epidemiology studies along with the available empirical data
in a full weight of evidence analysis in the final [Human
Health Risk Assessment].” 45 Thus, while the EPA continued
to use 10% AChE inhibition to set a point of departure, it
explained that “ongoing analyses will ensure that [the points
of departure] in [its] preliminary assessment are [also]
human health protective for neurodevelopmental toxicity
that may arise from pre- or postnatal exposure.” 46

      Memo from Danette Drew et al. to Tom Myers re: Chlorpyrifos:
     43

Preliminary Human Health Risk Assessment for Registration Review,
EPA, at 28 (June 30, 2011).
     44
          Id. at 31.
     45
          Id. at 34.
     46
          Id. at 42.
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                   25

    D. 2012–2015: The EPA Expresses Increasing
       Certainty That Chlorpyrifos Causes Neurotoxic
       Effects in Infants and Children

   In April 2012, having received no response from the
EPA on the pertinent arguments raised in the 2007 Petition, 47
PANNA and NRDC petitioned this Court for a writ of
mandamus.

    Meanwhile, also in April 2012, the EPA convened
another SAP. The 2012 SAP opined with more certainty
than the 2008 SAP that multiple “lines of evidence suggest
that chlorpyrifos can affect neurodevelopment at levels
lower than those associated with AChE inhibition, and that
the use of AChE inhibition data may not be the most
appropriate for . . . [assessing] the neurodevelopmental risks
of chlorpyrifos.” 48 The 2012 SAP paid particular attention
to the Human Cohort Studies and identified “nine strengths”
of them, including, among others, the longitudinal design,
the use of biomarkers of exposure (rather than only self-
reported exposure), and “the relative consistency of findings
in different populations while using similar standardized
exposure and outcome measures.” 49 The 2012 SAP also
identified some shortcomings of the Human Cohort Studies,
such as a relatively small sample size and uncertainty

    47
       The 2007 Petition raised several other claims, some of which the
EPA addressed at earlier points in time, but here petitioners only press
the claims related to neurotoxic effects.
    48
      SAP Minutes No. 2012-04, A Set of Scientific Issues Being
Considered by the Environmental Protection Agency Regarding
Chlorpyrifos Health Effects 53 (Apr. 10–12, 2012) (hereinafter “2012
SAP Minutes”).
    49
         Id. at 18.
26    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

regarding whether harms could be attributed to chlorpyrifos
alone. Overall, though, it found that “[t]he strengths of the
three studies support the Panel’s conclusion.” 50

    Specifically, the 2012 SAP, based on its review of all the
evidence available at the time, “concur[red] with the 2008
SAP and the Agency in concluding that chlorpyrifos likely
plays a role in impacting the neurodevelopmental outcomes
examined in the three cohort studies.” 51 It noted that the
Human Cohort Studies showed potentially serious harms to
infants and children, including “abnormal reflexes in the
newborn, pervasive development disorder at 24 or
36 months, mental development at 7–9 years, and attention
and behavior problems at 3 and 5 years of age.” 52

     Despite all this, the EPA, following issuance of the 2012
SAP report, still did not take final action on the 2007
Petition; but it represented in the mandamus proceedings that
it had “a concrete timeline for final agency action that would
resolve the 2007 Petition by February 2014.” 53 In light of
that representation, this Court, in July 2013, denied PANNA
and NRDC’s petition for a writ of mandamus.

    February 2014 came and went, but the EPA did not take
final action on the 2007 Petition. PANNA and NRDC

     50
          Id.
     51
          Id.
     52
          Id. at 17.
     53
          PANNA v. EPA (In re PANNA), 532 F. App’x 649, 651 (9th Cir.
2013).
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                    27

returned to this Court in September 2014 with a second
petition for a writ of mandamus.

   Shortly thereafter, in December 2014, the EPA published
a Revised Human Health Risk Assessment. It expressed
greater certainty both that chlorpyrifos was causing the
neurotoxic harms seen in the cohort studies and that it was
doing so through a mechanism other than AChE inhibition. 54

     Because the EPA concluded that chlorpyrifos could
cause harm even if exposure was below the AChE
inhibition-related point of departure, the EPA proposed a
new method for calculating a point of departure. But with
all this, the EPA still did not act on the 2007 Petition.

    In August 2015, this Court therefore granted the second
mandamus petition. 55 The EPA had offered an “ambiguous
plan to possibly issue a proposed rule nearly nine years after
receiving the administrative petition,” and the Court found
this to be “too little, too late.” 56 The Court found the EPA’s
delay “egregious” and ordered the EPA “to issue a full and

    54
        Memo from Danette Drew et al. to Tom Myers et al. re:
Chlorpyrifos: Revised Human Health Risk Assessment for Registration
Review, EPA (Dec. 29, 2014) (hereinafter “2014 Revised Human Health
Risk Assessment”), at 43 (“[C]hlorpyrifos likely played a role in the
neurodevelopmental outcomes observed in these epidemiology
studies.”); id. at 46 (“[The] EPA believes it is unlikely mothers enrolled
in the [Human Cohort Studies] experienced [red blood cell] AChE
inhibition”); see also id. (“Given the differences across laboratory
animal and epidemiology studies, the qualitative similarity in research
findings is striking.”).
    55
         PANNA v. EPA (In re PANNA), 798 F.3d 809, 811 (9th Cir. 2015).
    56
         Id.
28    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

final response to the petition no later than October 31,
2015.” 57

     E. 2015–2016: The EPA Finds That Chlorpyrifos
        Tolerances Are Unsafe

      Once again, this Court’s deadline came and went, and the
EPA still did not take final action on the 2007 Petition. But
in November 2015, the EPA published in the Federal
Register a Notice of Proposed Rulemaking “proposing to
revoke all tolerances for residues of the insecticide
chlorpyrifos.” 58 It wrote: “The agency is proposing to
revoke all of these tolerances because [the] EPA cannot, at
this time, determine that aggregate exposure to residues of
chlorpyrifos, including all anticipated dietary exposures and
all other non-occupational exposures for which there is
reliable information, are safe.” 59 Specifically, the EPA
found that “contributions to dietary exposures to
chlorpyrifos from food and residential exposures are safe,”
but “when those exposures are combined with estimated
exposures from drinking water, as required by the FFDCA,
. . . safe levels of chlorpyrifos in the diet may be exceeded
for people whose drinking water is derived from certain
vulnerable watersheds throughout the United States.” 60

     57
          Id.

      Chlorpyrifos; Tolerance Revocations, 80 Fed. Reg. 69,080,
     58

69,081 (Nov. 6, 2015) (hereinafter “2015 Notice of Proposed
Rulemaking”).
     59
          Id.
     60
          Id.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN           29

    The EPA adhered to the findings of the 2014 Revised
Human Health Risk Assessment. It relied upon “a
considerable and still-growing body of literature on the
effects of chlorpyrifos on the developing brain of laboratory
animals (rats and mice) indicating that gestational and/or
postnatal exposure may cause persistent behavioral effects
into adulthood.” 61 It also relied upon the three Human
Cohort Studies:

          [The] EPA has considered the strengths and
          limitations of these studies, and believes that
          random or systematic errors in the design,
          conduct or analysis of these studies were
          unlikely to fully explain observed positive
          associations       between        in     utero
          [organophosphate] exposure and adverse
          neurodevelopmental effects observed at birth
          and through childhood (age 7 years). [The]
          EPA believes these are strong studies which
          support a conclusion that [organophosphates]
          likely played a role in these outcomes. 62

The EPA acknowledged “significant uncertainties . . . about
the actual exposure levels experienced by mothers and infant
participants in the three children’s health cohorts,” but found
that the measured exposures “are likely low enough that they
were unlikely to have resulted in AChE inhibition.” 63

   61
        Id. at 69,090.
   62
        Id. at 69,091.
   63
        Id. at 69,093.
30    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

     Since, however, the proposed rule did not constitute a
final response to the 2007 Petition, this Court, in December
2015, ordered the EPA “to take final action by December 30,
2016 on its proposed revocation rule and its final response
to . . . [the] 2007 [P]etition.” 64 In other words, this Court,
despite the EPA’s repeated disregard of this Court’s orders,
most leniently gave the EPA yet another year to rule on the
2007 Petition.

    In April 2016, the EPA convened another SAP, which
peer-reviewed the 2014 Revised Human Health Risk
Assessment.     The 2016 SAP “agree[d] that both
epidemiology and toxicology studies suggest there is
evidence for adverse health outcomes associated with
chlorpyrifos exposures below levels that result in 10% red
blood cell [AChE] inhibition.” 65

    However, the 2016 SAP disagreed with the EPA’s
method for calculating a new point of departure.
Specifically, “with the exception of one Panel member, the
Panel stated that using [umbilical] cord blood chlorpyrifos
concentrations for derivation of the [point of departure]
could not be justified by any sound scientific evaluation.” 66
“Many Panel members” also objected to the specific
threshold of harm that the EPA used to replace 10% AChE
inhibition – a 2% decline in working memory – saying that

     64
          PANNA v. EPA (In re PANNA), 808 F.3d 402 (9th Cir. 2015).
     65
       SAP Minutes No. 2016-01, A Set of Scientific Issues Being
Considered by the Environmental Protection Agency Regarding:
Chlorpyrifos: Analysis of Biomonitoring Data 18 (Apr. 19–21, 2016)
(hereinafter “2016 SAP Minutes”).
     66
          Id. at 26.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN             31

such a change in working memory was “of questionable
biological significance.” 67

    On the other hand, the 2016 SAP explained that, in
general, it “support[ed] the use of measured maternal
chlorpyrifos blood concentrations as a surrogate for fetal
exposure . . . .” 68 And the SAP offered some guidance on
how to proceed. “Multiple panel members noted that
[physiologically based pharmacokinetic (“PBPK”)]
modeling is a valuable tool,” 69 and the SAP recommended
that the EPA “consider determination and characterization
of time-weighted average blood concentrations for different
exposure scenarios,” 70 rather than measurements based upon
umbilical cord blood concentrations at a single point in time.

    The EPA returned to this Court in June 2016, claiming
that it once again could not meet the much-extended
deadline for final action on the 2007 Petition. In August
2016, the Court denied the EPA’s request for an additional
six months. 71 The Court did, however, grant the EPA a
three-month extension, to March 31, 2017. The Court
acknowledged that “evidence may be imperfect . . . [,] the
feasibility inquiry is formidable, and . . . premature
rulemaking is undesirable,” but the Court found that “at this
stage, a claim of premature rulemaking has come and

    67
         Id. at 27.
    68
         Id. at 18.
    69
         Id.
    70
         Id. at 70.
    71
         NRDC v. EPA (In re PANNA), 840 F.3d 1014, 1015 (9th Cir.
2016).
32    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

gone.” 72 The Court warned that this was “the final
extension” and that the Court would “not grant any further
extensions.” 73

    In November 2016, the EPA revised its Human Health
Risk Assessment again. The 2016 Revised Human Health
Risk Assessment remains the EPA’s most recent
comprehensive assessment of the risks of chlorpyrifos. In
the assessment, the EPA “continue[d] to conclude that the
[Human Cohort Studies] provide the most robust available
epidemiological evidence.” 74 The EPA “acknowledge[d]
the lack of [an] established” mechanism of action that would
explain the neurotoxic effects and also recognized “the
inability to make strong causal linkages, and the unknown
window(s) of susceptibility.” 75 The EPA concluded,
nevertheless, that “[t]hese uncertainties do not undermine or
reduce the confidence in the findings of the epidemiology
studies. The epidemiology studies . . . represent different
investigators, locations, points in time, exposure assessment
procedures, and outcome measurements.” 76 “In summary,”
the EPA concluded that “the [Columbia Study], with
supporting results from the other [two Human Cohort
Studies] and the seven additional epidemiological studies
    72
       Id. (quoting Public Citizen Health Rsch. Grp. v. Chao, 314 F.3d
143, 154–55 (3d Cir. 2002)).
     73
          Id.

      Memo from Wade Britton to Dana Friedman re: Chlorpyrifos:
     74

Revised Human Health Risk Assessment for Registration Review, EPA
(Nov. 3, 2016) (hereinafter “2016 Revised Human Health Risk
Assessment”), at 12.
     75
          Id.
     76
          Id.
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                    33

reviewed in 2015, provides sufficient evidence that there are
neurodevelopmental effects occurring at chlorpyrifos
exposure levels below that required for AChE inhibition.” 77
Based on this finding, the EPA continued to conclude that it
was necessary to adopt an approach “protective of both the
AChE inhibition and any adverse effects that could occur at
lower doses.” 78

    The EPA acknowledged that “the 2016 SAP did not
support using the [Columbia Study] cord blood” to derive a
new point of departure. 79 Responsive to those comments,
the EPA adopted a different approach. 80 It accepted the 2016
SAP’s statement that the “EPA should use estimated peak
blood concentrations or [time-weighted average] blood
concentrations within the prenatal period” rather than
umbilical cord blood concentrations at the time of delivery. 81
Also, consistent with the 2016 SAP’s comments, the EPA

    77
         Id. at 13.
    78
         Id.
    79
         Id.
    80
      Id. at 4 (“Given that the window(s) of susceptibility are currently
not known for the observed neurodevelopmental effects, and the
uncertainties associated with quantitatively interpreting the [Columbia
Study] cord blood data, the SAP recommended that the agency use a time
weighted average . . . blood concentration of chlorpyrifos for the
[Columbia] [S]tudy cohort as the [point of departure] for risk assessment.
[The] EPA has chosen to follow that advice in this assessment.”).
    81
         Id. at 14.
34    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

estimated blood concentrations using a PBPK model devised
by a chlorpyrifos registrant. 82

    When the EPA compared the resulting safety thresholds
against typical pesticide exposure scenarios, it determined
that chlorpyrifos tolerances were not safe – even considering
food alone, without aggregating other exposure sources, like
drinking water. 83 For example, the EPA found that expected
food exposure for children 1–2 years of age was 14,000% of
the threshold level of risk concern. 84

   The EPA announced the findings of the 2016 Revised
Human Health Risk Assessment through a Notice of Data
Availability published in the Federal Register, 85 and it
reopened the comment period on its 2015 Notice of
Proposed Rulemaking. In the Notice of Data Availability,
the EPA reiterated that the present tolerances are “not

     82
          Id.
     83
          Id. at 24.
     84
          Id. at 6.
     85
        2016 Notice of Data Availability, supra note 3, 81 Fed. Reg. at
81,050 (“After careful consideration of public comments and the SAP’s
recommendations, [the] EPA has concluded the most appropriate path
for reconciling the SAP’s concerns is to follow through on the SAP’s
recommendation to use a time weighted average approach. The agency
agrees with the 2016 FIFRA SAP (and previous SAPs) that there is a
potential for neurodevelopmental effects associated with chlorpyrifos
exposure to occur at levels below 10% RBC AChE inhibition, and that
[the] EPA’s existing point of departure (which is based on 10% AChE
inhibition), is therefore not sufficiently health protective.”).
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                  35

sufficiently health protective.” 86 The Agency explained that
its

           revised analyses do not result in a change to
           the EPA’s proposal to revoke all tolerances
           but it does modify the methods and risk
           assessment used to support that finding in
           accordance with the advice of the SAP. The
           revised analysis indicates that expected
           residues of chlorpyrifos on most individual
           food crops exceed the ‘reasonable certainty
           of no harm’ safety standard under the
           [FFDCA].

The EPA adhered to its proposal to revoke chlorpyrifos
tolerances, rather than modify them, explaining that the
“EPA has not identified a set of currently registered uses that
meets the FFDCA safety standard because it is likely only a
limited number of food uses alone, and in combination with
predicted drinking water exposures, would meet the
standard.” 87 The EPA has never retracted the findings in its
2016 Revised Human Health Risk Assessment. 88

    86
         Id.
    87
         Id.

    88
        Today, the EPA’s website continues to warn about chlorpyrifos,
citing the 2016 Revised Human Health Risk Assessment:

           What does [the] EPA’s revised human health risk
           assessment show?

           This assessment shows dietary and drinking water
           risks for the current uses of chlorpyrifos. Based on
36    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

     F. 2017–Present: The EPA Denies the 2007 Petition

    Faced with this Court’s statement that it would brook no
further delays in the EPA’s ruling on the 2007 Petition, the
EPA finally in April 2017 ruled on the 2007 Petition.
Notwithstanding the findings in its own 2016 Revised
Human Health Risk Assessment, however, the EPA’s order
denying the 2007 Petition (the “2017 Order”) stated that,
“despite several years of study, the science addressing
neurodevelopmental effects remains unresolved.” 89
Therefore, the EPA concluded that “further evaluation of the
science during the remaining time for completion of
[FIFRA] registration review is warranted to achieve greater
certainty as to whether the potential exists for adverse
neurodevelopmental effects to occur from current human
exposures to chlorpyrifos.” 90

            current labeled uses, the revised analysis indicates that
            expected residues of chlorpyrifos on food crops
            exceed the safety standard under the [FFDCA]. In
            addition, the majority of estimated drinking water
            exposure from currently registered uses, including
            water exposure from non-food uses, continues to
            exceed safe levels . . . .

EPA, Revised Human Health Risk Assessment on Chlorpyrifos,
available at https://www.epa.gov/ingredients-used-pesticide-
products/revised-human-health-risk-assessment-chlorpyrifos (last
accessed Apr. 17, 2021).
     89
          2017 Order, supra note 24, 82 Fed. Reg. at 16,583.
     90
          Id.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN              37

    The EPA further explained that it was denying the 2007
Petition only because this Court had ordered it to make a
decision, but that

          [the] EPA has . . . concluded that it will not
          complete the human health portion of the
          registration review or any associated
          tolerance revocation of chlorpyrifos without
          first attempting to come to a clearer scientific
          resolution . . . . Because the [Ninth] Circuit’s
          August 12, 2016 order has made clear,
          however, that further extensions to the March
          31, 2017 deadline for responding to the
          Petition would not be granted, [the] EPA is
          today also denying all remaining petition
          claims.

   PANNA, NRDC, and others objected to the EPA’s
denial of the 2007 Petition, both by filing objections with the
EPA and by seeking relief from this Court. The Court denied
mandamus relief on the ground that the EPA had “now
complied with our orders” to issue a decision, and
“substantive objections must first be made through the
administrative process.” 91

    But even though the statute required the EPA to rule on
petitioners’ objections “[a]s soon as practicable after
receiving the arguments of the parties,” 21 U.S.C.
§ 346a(g)(2)(C), and even though these objections were
simply reiterations of the positions petitioners had
consistently taken since 2007, the EPA had still not
responded to petitioners’ objections 14 months later, when

    91
         PANNA v. EPA (In re PANNA), 863 F.3d 1131, 1132 (9th Cir.
2017).
38    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

the Court heard oral argument on petitioners’ petition for
review of the 2017 Order.

    The EPA objected to this Court’s consideration of the
merits of the decision on the ground that, until the EPA ruled
on petitioners’ administrative objections, this Court lacked
jurisdiction. A panel of this Court concluded that “the EPA
is engaging in yet more delay tactics to avoid our reaching
the merits of . . . whether chlorpyrifos must be banned from
use on food products because the EPA has not determined
that there is a ‘reasonable certainty’ that no harm will result
from its use, even under the established tolerances.” 92 The
panel held that, under these circumstances, the Court had
jurisdiction and that, on the merits, “the EPA bears a
continuing obligation to revoke tolerances that it can no
longer find with a ‘reasonable certainty’ are safe,” and
because the Agency could not make such a finding, the
tolerance must be revoked. 93 The panel vacated the 2017
Order and remanded to the EPA with instructions to revoke
all chlorpyrifos tolerances within 60 days after issuance of
the mandate. 94

    Subsequently, however, a majority of nonrecused active
judges voted to rehear the case en banc. The en banc Court
did not address the jurisdictional question, but instead issued
a writ of mandamus requiring the EPA to rule on the
objections to the 2017 Order within 90 days. 95 In July 2019,

     92
       LULAC v. Wheeler, 899 F.3d 814, 827 (9th Cir. 2018), vacated on
reh’g en banc, 914 F.3d 1189 (9th Cir. 2019).
     93
          Id. at 829.
     94
          Id.
     95
          LULAC v. Wheeler, 922 F.3d 443, 445 (9th Cir. 2019) (en banc).
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN               39

the EPA issued a final order (the “2019 Order”) denying
petitioners’ objections and thereby completing the
administrative denial of the 2007 Petition. The 2019 Order
again relied upon the need for greater scientific certainty, but
went further and held that “the objections and the underlying
Petition are not supported by valid, complete, and reliable
evidence sufficient to meet the Petitioners’ burden under the
FFDCA, as set forth in [the] EPA’s implementing
regulations.” 96

    With the Court’s jurisdiction now clear, petitioners
petitioned for review of the 2017 and 2019 Orders. Several
states moved to intervene. The en banc Court granted the
motion to intervene, consolidated the cases, and returned the
matter to this panel as a “comeback case.” 97

                     STANDARD OF REVIEW

    The Administrative Procedure Act (“APA”) authorizes
the Court to “hold unlawful and set aside agency action,
findings, and conclusions” if they are “arbitrary, capricious,
an abuse of discretion, or otherwise not in accordance with
law,” 98 and to “compel agency action unlawfully withheld
or unreasonably delayed.” 99 Agency action is arbitrary and
capricious where the agency has “offered an explanation for

    96
        Chlorpyrifos; Final Order Denying Objections to March 2017
Petition Denial Order, 84 Fed. Reg. 35,555, 35,557 (July 24, 2019)
(hereinafter “2019 Order”).
    97
       LULAC v. Wheeler, 940 F.3d 1126, 1126–27 (9th Cir. 2019) (en
banc); see 9th Cir. Gen. Order 3.6(b).
    98
         5 U.S.C. § 706(2)(A).
    99
         Id. § 706(1).
40    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

its decision that runs counter to the evidence before the
agency.” 100

                                 ANALYSIS

I. Merits

   The Court first considers whether the EPA lawfully
denied the 2007 Petition. Petitioners argue that the EPA’s
2017 and 2019 Orders were ultra vires under the FFDCA
and arbitrary and capricious under the APA.

     A. Whether the EPA Left in Effect a Tolerance Without
        Determining That It Is Safe

    As noted above, the FFDCA provides that the EPA “may
establish or leave in effect a tolerance for a pesticide
chemical residue in or on a food only if the Administrator
determines that the tolerance is safe. The Administrator
shall modify or revoke a tolerance if the Administrator
determines it is not safe.” 101 The statute also specifically
requires that the EPA “ensure that there is a reasonable
certainty that no harm will result to infants and children from
aggregate exposure to the pesticide chemical residue” and
“publish a specific determination regarding the safety of the
pesticide chemical residue for infants and children.” 102

    Courts “normally interpret[] a statute in accord with the
ordinary public meaning of its terms at the time of its

     100
        Motor Vehicle Mfrs. Ass’n of the U.S., Inc. v. State Farm Mut.
Auto. Ins. Co., 463 U.S. 29, 43 (1983).
     101
           21 U.S.C. § 346a(b)(2)(A)(i).
     102
           Id. § 346a(b)(2)(C)(ii)(I)–(II).
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                   41

enactment.” 103 Furthermore, the FFDCA must be “given a
liberal construction consistent with the Act’s overriding
purpose to protect the public health.” 104

    The EPA admits that the 2017 and 2019 Orders left in
effect tolerances without determining that they are safe,
claiming that it could delay this determination for several
more years until it had resolved safety-related issues in the
15-year FIFRA registration review. Since, as discussed
below, the EPA’s duty to engage in a periodic FIFRA
registration review is separate from its continuous obligation
to ensure safety under the FFDCA, this concession is
effectively dispositive in favor of petitioners.

    FIFRA aside, the EPA argues that it may leave in effect
tolerances, without a new safety finding, “when [the] EPA
concludes the petition contains insufficient evidence for
[the] EPA to undertake proceedings to revoke or modify
tolerances.” This argument fails for two reasons. First, once
the EPA has become aware, through a petition or otherwise,
of genuine questions about the safety of an existing
tolerance, the EPA has its own continuing duty under the
FFDCA to determine whether a tolerance that was once
thought to be safe still is, and here the EPA’s own studies
and pronouncements still in effect show that it regards
chlorpyrifos as harmful at levels below the existing
tolerances. Second, in any case, the 2007 Petition, under the
EPA’s own regulations, contained more than sufficient
evidence to undertake a safety review, and the EPA
recognized as much, began such a review, and only now,

    103
          Bostock v. Clayton County, 140 S. Ct. 1731, 1738 (2020).
    104
        United States v. An Article of Drug . . . Bacto-Unidisk, 394 U.S.
784, 798 (1969).
42    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

13 years later, claims for the first time that the 2007 Petition
was somehow inadequate.

     1. The EPA’s Duty to Ensure Human Safety

    The FFDCA imposes a continuous duty upon the EPA
by permitting it to “leave in effect” a tolerance “only” if it
finds it is safe. To “leave” something in effect means “to
cause or allow [it] to be or remain in a specified
condition.” 105 Denying the 2007 Petition caused the
chlorpyrifos tolerances to remain in place; as the EPA itself
wrote in its brief, it “le[ft] the existing tolerances in place
pending . . . registration review.” But in so doing, the EPA
did not “determine[] that the tolerance is safe.” 106 Rather,
the EPA’s own pronouncements show that it has already
concluded that it can no longer be reasonably certain that
chlorpyrifos is safe at current tolerances.

    It should be noted in this respect that, because of the
FQPA, assurance of safety for human health is the primary
issue the EPA must consider. Before 1996, when Congress
unanimously passed the FQPA, the EPA interpreted the
FFDCA to permit the balancing of safety against other
considerations, such as economic factors. Congress was

     105
        Merriam Webster, “Leave,” available at https://www.merriam-
webster.com/dictionary/leave (last accessed Apr. 17, 2021). The Dissent
quibbles with our use of the dictionary, arguing that the phrase “leave in
effect” is unambiguous. But then the Dissent ascribes to that term a
meaning of the Dissent’s own creation: that the EPA leaves in effect a
tolerance only when it conducts FIFRA registration review. The statute
imposes no such limitation on the phrase.
     106
           21 U.S.C. § 346a(b)(2)(A)(i).
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                      43

aware of this, 107 and the FQPA largely abrogated that
approach. 108 Congress made the explicit decision to
prioritize safety over all else. This makes the FFDCA a
remedial statute, which, as noted, must be “given a liberal
construction consistent with the Act’s overriding purpose to
protect the public health.” 109 Reading the EPA’s duty
narrowly would undermine the statute’s health-protective
purpose.

    The EPA argues that one of Congress’s purposes was to
provide the EPA with regulatory discretion. The EPA points
to the fifteen-year registration review cycle under FIFRA 110
as evidence that “Congress recognized that [reregistration]
would be a complex and potentially burdensome
proceeding”; thus, by contrast, Congress must have intended
“a different” – and less burdensome – obligation “[w]hen
[the] EPA responds to a petition to revoke pesticide
tolerances” under the FFDCA.             This contention is
unpersuasive because of the differences between FIFRA and

    107
       H.R. Rep. No. 104-669, pt. 2, at 40 (1996) (noting that under the
prior procedure for setting tolerances, the EPA was authorized to
consider “factors including the necessity for production of an adequate,
wholesome, and economical food supply”).
       108
           Notwithstanding the safety standard, in certain circumstances the
EPA may leave a tolerance in effect if “[u]se of the pesticide chemical
. . . is necessary to avoid a significant disruption in domestic production
of an adequate, wholesome, and economical food supply.” 21 U.S.C.
§ 346a(b)(2)(B)(iii)(II). However, this is permitted only where the risk
of harm from a “nonthreshold effect,” such as cancer, is not significantly
greater than would be allowed for threshold effects. See id.
§ 346a(b)(2)(B)(iv). Nonthreshold effects are not at issue here.
    109
          Bacto-Unidisk, 394 U.S. at 798.
    110
          See 7 U.S.C. § 136a(g)(1)(A)(iii)–(iv).
44    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

the FFDCA. The statutes impose different duties that require
different assessments. Under FIFRA, the EPA has a
discretionary power to cancel registrations for a variety of
reasons. 111 Specifically, FIFRA requires the EPA to balance
several factors in determining whether a pesticide should be
registered. For example, although FIFRA review includes
an assessment of safety under the FFDCA, 112 it also requires
a more general assessment of a pesticide’s “economic,
social, and environmental costs and benefits,” 113 including
“the impact of [any proposed] action . . . on production and
prices of agricultural commodities, retail food prices, and
otherwise on the agricultural economy.” 114 Given these
differences, Congress’s decision to give the EPA discretion
to set FIFRA priorities does not translate to the FFDCA. The
EPA’s obligations under the FFDCA are linked to a single
issue, safety, but they are mandatory. 115 The whole point of
the FQPA would be destroyed if the EPA could exercise
unfettered discretion to defer safety considerations until it

     111
           7 U.S.C. § 136d(b).
     112
          See id. § 136(bb). The Dissent accuses us of “repeatedly
miss[ing] this point,” Dissent, infra, at 83 n.6, but the fact that FIFRA
reregistration review includes, as one component, an assessment of
safety under the FFDCA does not gainsay the many other factors FIFRA
review also encompasses. FIFRA’s wider scope justifies that statute’s
periodic rereview timeline and the greater agency discretion that
approach entails. By contrast, the FFDCA’s singular focus on safety
corresponds with the EPA’s continuous duty to leave in effect a tolerance
only if it finds that the tolerance is safe.
     113
           7 U.S.C. § 136(bb).
     114
           Id. § 136d(b).
   115
       See 21 U.S.C. § 346a(b)(2)(A)(i) (“The Administrator shall
modify or revoke [an unsafe tolerance].” (emphasis added)).
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                    45

was prepared to engage in the full multi-factor balancing
assessment required for FIFRA registration.

   Our dissenting colleague reaches a different conclusion
regarding the EPA’s obligations, or lack thereof, when
confronted with a petition for revocation of tolerances. The
Dissent focuses upon two sentences in the FFDCA:

          The Administrator may establish or leave in
          effect a tolerance for a pesticide chemical
          residue in or on a food only if the
          Administrator determines that the tolerance is
          safe. The Administrator shall modify or
          revoke a tolerance if the Administrator
          determines it is not safe. 116

We think that these two simple sentences are – with their
emphasis on the word “only” – remarkably straightforward.
As here explained, they mean that the EPA can lawfully
deny the 2007 Petition and thereby “leave in effect” a
tolerance “only if the Administrator determines that the
tolerance is safe.” The Dissent’s more strained reading of
these sentences is to the effect that there are three possible
scenarios, one in which the EPA “determines that a tolerance
is safe,” one in which the EPA “determines it is not safe,”
and one in which the EPA is unwilling or unable to make a
safety determination at this time. In this latter, middle world,
the Dissent continues, the statute is silent as to the EPA’s
obligations, leaving the EPA with the discretion to leave in
    116
        Id. The EPA and the Dissent also contend that our reading
renders the second sentence superfluous, but it does not. The second
sentence limits the EPA’s discretion by explaining that when it finds that
a tolerance is not safe, it may not, for example, convene a SAP or wait
15 years pending further research; its only options are to revoke or
modify the tolerance.
46    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

effect a tolerance based on its prior safety finding (here, the
2006 safety finding).

    One problem (among others) with the Dissent’s
imaginative reading is that other statutory provisions are not
silent. The FFDCA imposes an overarching obligation that
the EPA protect human safety, and particularly the safety of
infants and children:

        In establishing, modifying, leaving in effect,
        or revoking a tolerance or exemption for a
        pesticide chemical residue, the Administrator
        shall assess the risk of the pesticide chemical
        residue . . . and shall ensure that there is a
        reasonable certainty that no harm will result
        to infants and children from aggregate
        exposure to the pesticide chemical residue. 117

    Congress has excluded the middle, not this Court. The
EPA can only lawfully take agency action to establish or
leave in effect a tolerance (e.g., denying the 2007 Petition) if
the EPA finds that the tolerance is safe.

     2. The Burdens of Production and Persuasion

    The EPA claims that the issue of safety as it bears on an
existing tolerance need not be addressed unless a petitioner
meets a threshold burden to come forward with evidence that
the existing tolerance is unsafe. In this regard, the EPA
points to the fact that the FFDCA gives the EPA the
authority to “establish the requirements for information and

    117
        21 U.S.C. § 346a(b)(2)(C) (punctuation and section lettering
omitted).
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                   47

data to support a petition to modify or revoke a tolerance.” 118
In a regulation promulgated pursuant to that authority, the
EPA requires such a petition to “furnish reasonable grounds
for the action sought.” 119 Reasonable grounds “include . . .
an assertion of facts (supported by data if available) showing
. . . that new data are available as to toxicity of the chemical,
or that experience with the application of the tolerance . . .
may justify its modification or revocation.” 120

    We do not doubt that the EPA has gatekeeping authority
to reject a wholly frivolous petition – i.e., a petition that fails
even to “furnish reasonable grounds for the action sought” –
without publishing a notice of its filing if the petition is
deficient on its face, and in such circumstances we can
assume the EPA need not address the concerns raised by the
petition. But the record here unequivocally shows both that
the 2007 Petition met all relevant requirements and that, in
fact, it caused the EPA to re-evaluate the safety of the
chlorpyrifos tolerances, thus triggering the EPA’s duty to
ensure a reasonable certainty of no harm.

    The FFDCA requires the EPA to determine whether a
petition satisfies the threshold requirements prior to
publishing a notice of the filing of the petition. 121 Here, the
EPA published a notice of the filing of the 2007 Petition in

    118
          21 U.S.C. § 346a(d)(2)(B).
    119
          40 C.F.R. § 180.32(b).
    120
          Id.
    121
        See 21 U.S.C. § 346a(d)(3) (“A notice of the filing of a petition
that the Administrator determines has met the [data and information]
requirements . . . shall be published by the Administrator within 30 days
after such determination.” (emphasis added)).
48    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

October 2007, 122 thereby finding that it met the data and
information requirements in the FFDCA and the EPA’s
regulations promulgated thereunder. The EPA cannot now
be heard, more than a dozen years later, to claim that the
petition did not, in fact, meet those threshold requirements.

     Independently, even if the EPA had raised this issue
thirteen years ago when the 2007 Petition was filed, the EPA
offers no specific way in which the petition failed to comply
with the EPA’s technical requirements and no plausible
argument for why the 2007 Petition does not contain
“reasonable grounds” for revocation. The EPA points to the
continued scientific uncertainty regarding how chlorpyrifos
harms infants and children and the fact that the 2007 Petition
did not attach complete underlying data for the studies that
it cited. But the regulation does not say that the petition must
prove that revocation is required; it requires only that the
petition state “reasonable grounds” for revocation. And the
grounds listed in the 2007 Petition meet any definition of
“reasonable”; indeed, the EPA has implicitly acknowledged
as much by reacting to the 2007 Petition with years of
deliberation, hundreds of pages of analysis, several
convenings of the SAP, and a Notice of Proposed
Rulemaking and further Notice of Data Availability
proposing to grant the requested relief, all substantially
based on grounds cited in the 2007 Petition.

    The Dissent contends that a petitioner who seeks
revocation of a pesticide tolerance bears not only a burden
of production, i.e., to provide “reasonable grounds” for
revocation, but also a burden of persuasion, i.e., to offer
valid, complete, and reliable data that affirmatively
demonstrate that the tolerances are unsafe. However, as

     122
           72 Fed. Reg. 58,845 (Oct. 17, 2007).
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN               49

previously explained, the Dissent’s reading is inconsistent
with the FQPA’s health protective purpose and the FFDCA’s
overarching command that the EPA, whenever leaving in
effect a tolerance, “assess the risk of the pesticide chemical
residue . . . and . . . ensure that there is a reasonable certainty
that no harm will result to infants and children from
aggregate exposure . . . .” 123 The Dissent’s reading is also
inconsistent with the EPA’s regulations, which only impose
a burden of production on the petitioner. 124 Indeed, in its
brief the EPA relies upon the burden-setting regulation that
would apply if the EPA conducted an evidentiary hearing on
the 2007 Petition. Although there was no evidentiary
hearing here, the regulation is illustrative. Ordinarily, “[t]he
party whose request for an evidentiary hearing was granted
has the burden of going forward in the hearing with evidence
as to the issues relevant to that request for a hearing.” 125
However, when section 408 of the FFDCA is at issue, the
section pertaining to “safety,” then “[t]he party or parties
who contend that a regulation satisfies the criteria of section
408 of the FFDCA has the burden of persuasion in the
hearing on that issue, whether the proceeding concerns the
establishment, modification, or revocation of a tolerance or
exemption from the requirement for a tolerance.” 126 Put
simply, on the question of safety, while the burden of
production is on the petitioners, the burden of persuasion
always rests on the party claiming that a tolerance is safe.
For these reasons, the Court concludes that when the EPA

    123
          21 U.S.C. § 346a(b)(2)(C).
    124
          40 C.F.R. § 180.32(b).
    125
          40 C.F.R. § 179.91(a).
    126
          Id. § 179.91(b).
50    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

publishes a petition seeking revocation of a tolerance and
later takes final action denying that petition, the EPA leaves
that tolerance in effect. The EPA can only do so if it finds
the tolerance to be safe for the general population and for
infants and children. 127 Here, the EPA did not make such
findings, so it acted directly contrary to the FFDCA.

     B. Whether Denying the 2007 Petition Was Arbitrary
        and Capricious

    Separately, in light of the present record and the EPA’s
assessment of that record, petitioners argue that, even if the
FFDCA does not require a safety finding here (which we
find it does), the EPA’s denial of the 2007 Petition was
arbitrary and capricious. The Court agrees.

    An agency has a baseline obligation to “articulate a
satisfactory explanation for its action including a ‘rational
connection between the facts found and the choice
made.’” 128 The EPA has not done so because none of the
reasons proffered in the 2017 and 2019 Orders provides “a
satisfactory explanation for” denying the 2007 Petition.

    The EPA has not retracted the 2016 Revised Human
Health Risk Assessment indicating that chlorpyrifos is not
safe at current tolerances and has not issued a new Human

     127
        This is not to say, of course, that the EPA must perform a new
Human Health Risk Assessment in response to every petition. The EPA
might consider the issues raised by the petition alongside all the other
evidence considered in its most recent safety determination and conclude
that it need not conduct further review before reaffirming its prior
findings.
    128
        Motor Vehicle Mfrs. Ass’n, 463 U.S. at 43 (quoting Burlington
Truck Lines v. United States, 371 U.S. 156, 168 (1962)).
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN             51

Health Risk Assessment or SAP report since 2016. Rather,
the 2017 Order denied the 2007 Petition on purely
discretionary grounds, relying upon the EPA’s purported
authority to demand more study through at least 2022. After
13 years of delay, a desire for yet more delay does not
rationally support denial of a petition that the EPA’s own
prior studies indicate raises a genuine issue of ongoing harm
to infants and children.

    The EPA asserted in the 2017 Order that it “may lawfully
re-prioritize the registration review schedule developed by
earlier [presidential] administrations.” 129 In other words,
more delay. Furthermore, while the EPA recognized that the
2007 Petition was filed under the FFDCA and raised
arguments concerning human safety, the EPA found in its
2017 Order that it had to be permitted to synchronize its
review of the petition with FIFRA registration review. To
find otherwise “would effectively give petitioners under the
FFDCA the authority to re-order scheduling decisions
regarding the FIFRA registration review process that
Congress has vested in the Administrator.” 130

    But the FIFRA registration review, as already noted, is a
different animal, in that it permits a balancing of multiple
factors, whereas a FFDCA review is limited to the sole issue
of safety but allows no balancing as far as that factor is
concerned. Chlorpyrifos’s wide use and the significance of
this issue to the Administration are not valid legal
considerations, as the EPA recognized in its 2017 Order. 131

   129
         2017 Order, supra note 24, 82 Fed. Reg. at 16,590.
   130
         Id.
   131
         Id.
52    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

As already noted, the FQPA amended the FFDCA to
explicitly prohibit the EPA from balancing safety against
other considerations, including economic or policy
concerns, in most instances. Thus, the EPA’s citation to
these admittedly extralegal factors in its denial of the 2007
Petition is telling. It strongly suggests that the EPA’s about-
face in 2017 was motivated by factors unrelated to human
safety, contrary to the FFDCA’s commands.

    The reference in the denial to the FIFRA 15-year period
of review is, instead, nothing but a red herring, as the 2007
Petition does not concern FIFRA registration review. It
concerns a petition under the FFDCA that contends that
chlorpyrifos is unsafe. The EPA’s position would largely
strip FFDCA petitions of meaning, converting them into
comments for the EPA to consider whenever it gets around
to the next FIFRA registration review. The EPA offers no
statutory support for this – because there is none. When, as
here, a petitioner files a detailed petition identifying new
evidence providing reasonable grounds to believe that
exposure at less than a pesticide’s current tolerances may be
unsafe, the EPA has a duty to “giv[e] due consideration to
[the] petition . . . and any other information available” 132 and
to act on that petition with reasonable dispatch to protect
human health – not fifteen years later. For these reasons,
consistent with what this Court has said for years, the EPA’s
desire for delay is not a satisfactory explanation for denying
the 2007 Petition.

   The 2019 Order (unlike the 2017 Order) relied upon a
second ground for denial of the 2007 Petition. The EPA
found that PANNA and the NRDC bore an initial burden of
production that, according to the EPA, they did not meet.

     132
           21 U.S.C. § 346a(d)(4)(A).
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN             53

The EPA pointed out that the FFDCA requires it to consider
“the validity, completeness, and reliability of the available
data” 133 and authorizes it to promulgate regulations stating
what a petition must contain. 134 As noted above, under this
authority, the EPA promulgated a regulation requiring a
petition to include “reasonable grounds” for revocation,
which include an “assertion of facts (supported by data if
available).” 135 Given this initial burden of production, the
“EPA conclude[d] that the information . . . presented by
Petitioners is not sufficiently valid, complete, and reliable to
support abandoning the use of AChE inhibition as the critical
effect for regulatory purposes under the FFDCA section
408.” 136 Thus, the EPA concluded that the FFDCA safety
issue was not before it.

    For reasons already stated, this finding is unreasonable
and inconsistent with the petition itself. The 2007 Petition
claimed in detail that chlorpyrifos posed a risk of neurotoxic
harm, especially to infants and children, and it invoked the
live animal studies and the Columbia Study as evidence.
The EPA acknowledges that it “has, since [2006],
consistently concluded that the available data support a
conclusion of increased sensitivity of the young to the
neurotoxic effects of chlorpyrifos and for the susceptibility
of the developing brain to chlorpyrifos.” 137 Therefore, under
any reasonable construction, the 2007 Petition met the low

   133
         21 U.S.C. § 346a(b)(2)(D)(i).
   134
         Id. § 346a(d)(2)(B).
   135
         40 C.F.R. § 180.32.
   136
         2019 Order, supra note 96, 84 Fed. Reg. at 35,563.
   137
         Id.
54    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

bar of stating “reasonable grounds” for revocation with an
“assertion of facts” in support. Also, as noted above, the
time for finding that the petition did not meet the burden of
production was in 2007, before the EPA published the
petition in the Federal Register.

    Because the Court rejects both of the EPA’s
justifications for refusing to make a safety finding, the Court
concludes that the EPA’s denial of the 2007 Petition was
arbitrary and capricious. 138

    Although not necessary for this determination, the Court,
for completeness, also considers the EPA’s four objections
to the data.

    First, the EPA objects, in general, that “the science on
this question is not resolved and would benefit from
additional inquiry.” 139 It will always be possible to conduct
additional studies or to reach a greater degree of certainty,
but a generalized concern that the science is not resolved is
not a rationale sufficient to support denying a revocation
petition. The FFDCA requires that the EPA make a safety
determination based on whatever “information” is

     138
         The Dissent takes great umbrage at this conclusion, reminding us
that “[w]hen an agency makes determinations ‘within its area of special
expertise, at the frontiers of science . . . a reviewing court must generally
be at its most deferential.’” Dissent, infra, at 109 (alteration in original)
(quoting Balt. Gas & Elec. Co. v. NRDC, 462 U.S. 87, 103 (1983)). If
the 2019 Order had found that existing chlorpyrifos tolerances were safe,
then such deference would be appropriate. But no such finding was
made. It is the Order’s utter failure to make a required safety
determination that this Court finds was arbitrary and capricious. This
has nothing to do with deference or non-deference to expertise and
everything to do with simple compliance with the law.
     139
           Id. at 35,560.
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                  55

“available.” 140 And, as this Court has said before, a statutory
mandate to rely on “available” scientific data “does not mean
‘the best scientific data possible.’” 141

    Second, the EPA argues that it does not know how
chlorpyrifos’s neurotoxic effects harm infants and children.
But that is not the question before the EPA. The question is
whether chlorpyrifos causes such harms. Even if the
mechanism is unknown, if a tolerance is unsafe, then the
EPA must revoke it. 142

    Third, the EPA argues that the studies of rats and mice
applied a “dosing regimen . . . that differs from
internationally accepted protocols.” 143 The EPA says:

           [T]he in vivo laboratory animal studies
           generally use fewer days of dosing that are
           aimed at specific periods of rodent fetal or
           early post-natal development compared to
           internationally adopted guideline studies
           which are intended to cover both pre- and
           post-gestational periods. The degree to
           which these shorter dosing periods coincide

    140
          21 U.S.C. § 346a(d)(4)(A).
    141
        San Luis & Delta-Mendota Water Auth. v. Jewell, 747 F.3d 581,
602 (9th Cir. 2014) (quoting Building Indus. Ass’n v. Norton, 247 F.3d
1241, 1246 (D.C. Cir. 2001)).
    142
        Cf. Am. Trucking Ass’ns, Inc. v. EPA, 175 F.3d 1027, 1055 (D.C.
Cir. 1999) (finding the EPA was not required to prove “how particles
actually interact with cells and organs to cause sickness and death”),
aff’d in part and rev’d in part on other grounds sub nom. Whitman v.
Am. Trucking Assn’s, 531 U.S. 457 (2001).
    143
          2019 Order, supra note 96, 84 Fed. Reg. at 35,563.
56    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

           with comparable windows of susceptibility in
           human brain development is unclear. 144

This argument, apparently raised for the first time in the
2019 Order, is stated in cursory fashion. The EPA does not
identify these “internationally accepted protocols” or
explain why the EPA did not find deviations from these
protocols to be troubling in the 2015 Notice of Proposed
Rulemaking, the 2016 Notice of Data Availability, the 2016
Revised Human Health Risk Assessment, or the many other
publications by the EPA that relied upon the animal studies.
In any event, however, even if the Court were convinced, for
the sake of argument, that divergence from these
internationally accepted dosing protocols might somewhat
diminish the value of these studies, it would not change the
result, for reasons described below.

    Fourth and finally, the EPA objects that it has been
unable to get the raw data, as well as information concerning
how residential pesticides were applied, from the Columbia
Study. (Columbia, for its part, has expressed reasonable
concerns about the subjects’ privacy, especially given that
the study covered a small geographic radius. Nevertheless,
Columbia suggested to the EPA that it could make at least

     144
         Id. The EPA also explains that “except for some studies
conducted recently, most of the in vivo laboratory studies use doses that
are higher than doses that cause 10% [red blood cell] AChE inhibition.
These studies are therefore are [sic] not useful quantitatively to evaluate
whether [the] EPA’s current regulatory standard is or is not sufficient to
preclude the potential for neurodevelopmental effects.” Id. This
objection is, of course, valid as far as it goes: studies that apply pesticide
at doses above the current tolerance are less helpful in showing whether
the tolerance is safe. But the EPA concedes that “some studies” use
lower doses. The EPA offers no justification for refusing to consider
these studies.
         LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                57

some of the datasets available for viewing in a secure data
center. 145) The EPA has changed its position over time
regarding the value of this data. It initially requested the
data, but after meeting with the Columbia researchers in
2014, the EPA abandoned its request for this data. 146 Later,
when the EPA sought to develop a point of departure based
upon the umbilical cord blood measurements in the
Columbia Study, it sought the data again. However, the
2016 SAP took issue with an approach based upon those
cord blood measurements, so, as explained above, the EPA
moved to a time-weighted average approach based upon a
registrant’s PBPK model. As a result, the EPA once again
determined that it did not need the Columbia data, explaining
that its new approach “does not directly rely on quantitative
measures of chlorpyrifos in cord blood obtained from
[Columbia], and thus, the lack of access to the raw data from
[Columbia] is less of an uncertainty.” 147 The EPA has now
reversed position yet again, reiterating its desire for the data.

    145
       See Chlorpyrifos Epidemiology Study Data De-identification
Discussion (July 31, 2018).
    146
         2014 Revised Human Health Risk Assessment, supra note 54,
at 391 (“As a result of this meeting and additional discussions with
[Columbia] staff, [the] EPA concluded that access to the raw data would
either not provide answers to [the] EPA’s questions or that the
information [the] EPA sought could be obtained without analyzing the
raw data. Indeed, based on discussions in that meeting as well as further
work conducted by agency staff, [the] EPA has gained additional
information to better clarify and characterize the major issue areas
identified as uncertainties. For these reasons, [the] EPA decided that it
would not further pursue its request for the analytic data file from the
[Columbia] researchers.”) (emphasis added).
    147
          2016 Revised Human Health Risk Assessment, supra note 74,
at 14.
58    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

    The EPA’s flip-flopping suggests the weakness of this
objection. Nevertheless, even if the Court were to assume
for the sake of argument that the underlying data, and
information concerning the method of residential pesticide
application, would be of some use and that the EPA’s
inability to access it might diminish the value of the
Columbia Study, it would not change the result in this case.

    This is because, while the EPA might reasonably
conclude that divergences from international protocols and
lack of access to raw data might affect the weight the EPA
accords to these studies, they are nowhere near enough to
show that the studies are entirely unreliable. The FFDCA
requires the EPA to consider the “information” that is
“available” 148 and to make a safety determination based on
that information. In this case, live animal studies showing
sex-linked, neurotoxic harms from in utero chlorpyrifos
exposure are available – even if such studies are supposedly
not perfectly aligned with (unspecified) international
standards. And peer-reviewed cohort studies showing harms
to infants’ neurological development following their
mothers’ exposure to chlorpyrifos are available – even if the
underlying data is not. The EPA speculates that it might find
an error if the unspecified international standards were
applied to the animal studies or if the data from the Human
Cohort Studies were available. But that is all it is:
speculation. Such speculation “runs counter to the evidence
before the agency,” 149 so it cannot form the basis for denying
the 2007 Petition.

     148
           21 U.S.C. § 346a(d)(4)(A).
     149
           See Motor Vehicle Mfrs. Ass’n, 463 U.S. at 43.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN          59

II. Remedy

    The Court concludes that the EPA lacked power to deny
the 2007 Petition without making the safety findings
required by the FFDCA and that the EPA’s decision was
arbitrary and capricious. Therefore, the Court must, at least,
“set aside the order or regulation complained of” 150 and
remand to the EPA. Petitioners argue that the Court should
also order the EPA to revoke the current chlorpyrifos
tolerances and registrations by a date certain. Under the
APA, the Court has the power to “compel agency action
unlawfully withheld or unreasonably delayed.” 151 The Court
returns once more to the two sentences of the FFDCA that
are key to assessing whether the Court should order the relief
petitioners request:

          The Administrator may establish or leave in
          effect a tolerance for a pesticide chemical
          residue in or on a food only if the
          Administrator determines that the tolerance is
          safe. The Administrator shall modify or
          revoke a tolerance if the Administrator
          determines it is not safe. 152

     The second sentence is more than a mere gloss on the
first because the command inherent in the second sentence

   150
         21 U.S.C. § 346a(h)(2).
   151
         5 U.S.C. § 706(1).
   152
         21 U.S.C. § 346a(b)(2)(A)(i).
60       LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

is important. 153 To be sure, the “only if” clause in the first
sentence, standing alone, limits what the EPA may do when
it determines that a tolerance is unsafe: it may not leave it in
effect. But what are the EPA’s options? May it order
additional study? Convene another SAP? Wait for fifteen
years to see if further evidence appears? No. The second
sentence makes clear that, once the EPA has determined that
a tolerance is not safe, it has no discretion to temporize
pending additional research; it must modify or revoke the
tolerance. For these reasons, if the EPA has determined that
the present chlorpyrifos tolerances are not safe – or if that is
the only conclusion the EPA could reasonably draw on this
record – then the EPA has unlawfully withheld the relief that
petitioners request.

    On the present record, the only reasonable conclusion the
EPA could draw is that the present tolerances are not safe
within the meaning of the FFDCA. The EPA can find a
tolerance safe only if there is “a reasonable certainty” of “no
harm,” 154 and for nearly a decade, the EPA and its SAPs
have concluded that there is not a reasonable certainty of no
harm:

     •      2012 SAP: “[E]vidence suggest[s] that chlorpyrifos
            can affect neurodevelopment at levels lower than
            those associated with AChE inhibition, and that the
            use of AChE inhibition data may not be the most
            appropriate for dose-response modeling and

     153
        For this reason, the EPA and the Dissent are also incorrect to
contend that petitioners’ reading of the statute contains surplusage. See
Dissent, infra, at 80.
     154
           21 U.S.C. § 346a(b)(2)(A)(ii).
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN            61

           derivation of a point of departure for assessment of
           the neurodevelopmental risks of chlorpyrifos.” 155

    •      2014 Revised Human Health Risk Assessment:
           “[C]hlorpyrifos likely played a role in the
           neurodevelopmental outcomes observed in these
           epidemiology studies.” 156 Moreover, “it is unlikely
           mothers enrolled in the [Human Cohort Studies]
           experienced [red blood cell] AChE inhibition.” 157

    •      2015 Notice of Proposed Rulemaking: “[The] EPA
           cannot, at this time, determine that aggregate
           exposure to residues of chlorpyrifos, including all
           anticipated dietary exposures and all other non-
           occupational exposures for which there is reliable
           information, are safe.” 158

    •      2016 SAP: “[B]oth epidemiology and toxicology
           studies suggest there is evidence for adverse health
           outcomes associated with chlorpyrifos exposures

    155
          2012 SAP Minutes, supra note 48, at 53.
    156
        SAP Minutes No. 2008-04, A Set of Scientific Issues Being
Considered by the Environmental Protection Agency Regarding: The
Agency’s Evaluation of the Toxicity Profile of Chlorpyrifos 43
(Sept. 16–18, 2008).
    157
          Id. at 46.
    158
        2015 Notice of Proposed Rulemaking, supra. note 58, 80 Fed.
Reg. at 69,081.
62       LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

            below levels that result in 10% red blood cell [AChE]
            inhibition.” 159

     •      2016 Revised Human Health Risk Assessment:
            The Columbia Study, “with supporting results from
            the other [Human Cohort Studies] and the seven
            additional epidemiological studies reviewed in 2015,
            provides sufficient evidence that there are
            neurodevelopmental      effects      occurring    at
            chlorpyrifos exposure levels below that required for
            AChE inhibition.” 160

     •      2016 Notice of Data Availability: “[E]xpected
            residues of chlorpyrifos on most individual food
            crops exceed the ‘reasonable certainty of no harm’
            safety standard under the [FFDCA] . . . . [The] EPA
            has not identified a set of currently registered uses
            that meets the FFDCA safety standard . . . . 161

   Even in its brief here, the EPA, though it purports to
withhold judgment on chlorpyrifos’s safety, admits that it
cannot conclude there is a reasonable certainty of no harm.
Rather, the EPA represents that there are “uncertainties
concerning the impact of chlorpyrifos on children”
(emphasis added).

    The EPA has not determined, and on this record
reasonably could not determine to a “reasonable certainty”

     159
           2016 SAP Minutes, supra note 65, at 18.
     160
           2016 Revised Human Health Risk Assessment, supra note 74,
at 13.
     161
           Id.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                      63

that aggregate chlorpyrifos exposures under the current
tolerances pose no risk of harm. Therefore, by statutory
definition, the present tolerances are not safe. Accordingly,
the EPA’s obligation is clear: it must modify or revoke
chlorpyrifos tolerances and modify or cancel chlorpyrifos
registrations.

    The EPA cites cases counseling that upon reversal of
agency action, an open-ended remand is the correct
approach, “[g]enerally speaking” 162 and “except in rare
circumstances.” 163 But this is not a typical case. On the
present record the EPA has limited legal discretion: its only
options are to modify or revoke the tolerances. Nor would it
be reasonable to remand for further factfinding after thirteen
years of interminable delay. Indeed, further delay would
make a mockery, not just of this Court’s prior rulings and
determinations, but of the rule of law itself. This is precisely
the sort of “rare circumstance” where yet another open-
ended remand would only frustrate the purpose of the
FFDCA.

    Finally, the EPA argues that “any order by this Court
unilaterally ordering [the] EPA to revoke the existing
tolerances for chlorpyrifos or cancel the existing
registrations would raise serious due process concerns” for
registrants and “violate Congress’s procedures.” Here,
however, the Court is not unilaterally ordering the EPA to
revoke existing tolerances; as explained below, it may
instead modify such tolerances if it can make the requisite
safety findings.

   162
         INS v. Orlando Ventura, 537 U.S. 12, 16 (2002).
   163
         Fla. Power & Light Co. v. Lorion, 470 U.S. 729, 744 (1985).
64    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

    In any event, remanding with specific instructions does
not raise due process concerns. In responding to a petition,
the FFDCA explicitly authorizes the EPA to “issue a final
regulation modifying or revoking a tolerance . . . (which
final regulation shall be issued without further notice and
without further period for public comment).” 164 On this
record, immediate issuance of a final regulation is the only
reasonable action, and the Court orders the EPA to do so.

    Such a final regulation could take one of two forms:
either it could revoke all chlorpyrifos tolerances or it could
modify chlorpyrifos tolerances and conclude that under the
new tolerances there is a “reasonable certainty that no harm
will result” due to “aggregate exposure to the pesticide
chemical residue” that would result from such modified
tolerances, including “to infants and children.” 165 To be
clear, the EPA may only choose to modify chlorpyrifos
tolerances, rather than to revoke them, if at the same time it
publishes such a safety determination. 166 On this record, it

     164
         21 U.S.C. § 346a(d)(4)(A)(i) (emphasis added) (comma
omitted).
     165
           Id. § 346a(b)(2)(A)(ii), (b)(2)(C)(ii)(I).
     166
         The Dissent opines that the Court “may have effectively
foreclosed other options Congress made available,” Dissent, infra, at 112
n.11, such as the exceptional steps the EPA may take when “the residue
protects consumers from adverse effects on health that would pose a
greater risk than the dietary risk” or when the tolerance “is necessary to
avoid a significant disruption in domestic production of an adequate,
wholesome, and economical food supply.”                       21 U.S.C.
§ 346a(b)(2)(B)(iii). These provisions offer alternatives to the FFDCA’s
general safety requirement for certain “eligible pesticide chemical
residues,” but only for adults. While subparagraph (b)(2)(B) provides an
exception to “subparagraph [(b)(2)(A)(i)],” the general safety rule, it
expressly requires compliance with subsection (b)(2)(C), which
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                      65

may well be that the EPA cannot make such a determination.
In 2016, the EPA explained that it “ha[d] not identified a set
of currently registered uses that meets the FFDCA safety
standard,” 167 a finding consistent with more than a decade of
EPA issue papers, revised human health risk assessments,
and SAP proceedings.

    Nevertheless, during the pendency of this proceeding, in
December 2020, the EPA issued a Proposed Interim
Registration Review Decision proposing to modify certain
chlorpyrifos tolerances. The EPA also convened another
SAP in 2020. If, based upon the EPA’s further research the
EPA can now conclude to a reasonable certainty that
modified tolerances or registrations would be safe, then it
may modify chlorpyrifos registrations rather than cancelling
them. 168

mandates that the EPA assure a reasonable certainty of no harm to
children specifically. Id. § 346a(b)(2)(B)(vi). Thus, these provisions are
irrelevant because regardless of whether chlorpyrifos is an “eligible”
pesticide for purposes of § 346a(b)(2)(B) – a question not briefed by the
parties and raised sua sponte by the Dissent – the EPA may only leave
in effect chlorpyrifos tolerances that are safe for children.
     167
         2016 Notice of Data Availability, supra note 3, 81 Fed. Reg.
at 81,050.
    168
        Whichever path the EPA chooses to take, the FFDCA also
provides that within 60 days after the EPA publishes a final response to
the 2007 Petition, either modifying chlorpyrifos tolerances and
publishing a safety finding or revoking chlorpyrifos tolerances, anyone
may object to the EPA’s final order, 21 U.S.C. § 346a(g)(2)(A), and the
EPA must then “issue an order stating the action taken” on those
objections, id. § 346a(g)(2)(C). It is hard to imagine that registrants will
have much to add, given the many opportunities they have already
received to comment on the 2015 Notice of Proposed Rulemaking and
the 2016 Notice of Data Availability, as well as to participate as amici
66    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

      To be clear, however, this is not an open-ended remand
or a remand for further factfinding. The EPA must act based
upon the evidence and must immediately revoke or modify
chlorpyrifos tolerances.

    For these reasons, the Court remands this matter to the
EPA with instructions to publish a legally sufficient final
response to the 2007 Petition within 60 days of the issuance
of the mandate. That response must be a final regulation that
either revokes all chlorpyrifos tolerances or modifies
chlorpyrifos tolerances and makes the requisite safety
findings based on aggregate exposure, including with respect
to infants and children.

    While the Dissent effectively views this as a “tight
deadline[],” 169 it agrees that the “EPA dithered far too
long.” 170 The EPA has had nearly 14 years to publish a
legally sufficient response to the 2007 Petition. During that
time, the EPA’s egregious delay exposed a generation of
American children to unsafe levels of chlorpyrifos. By
remanding back to the EPA one last time, rather than
compelling the immediate revocation of all chlorpyrifos
tolerances, the Court is itself being more than tolerant. But
the EPA’s time is now up.

curiae before this Court. But, in any event, registrants’ 60-day period to
object will follow the EPA’s final revocation of chlorpyrifos tolerances
(or modification with concomitant safety findings). If registrants ask the
EPA to promulgate new chlorpyrifos tolerances or revert to higher
tolerances, they must provide proof of safety, and the EPA can approve
registrants’ request only if the EPA concludes that there is a reasonable
certainty of no harm, including for infants and children.
     169
           Dissent, infra, at 115.
     170
           Dissent, infra, at 67.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN          67

                            CONCLUSION

    We GRANT the petitions for review. The 2017 Order
and the 2019 Order are vacated, and the matter is remanded
to the EPA, with instructions to (1) grant the 2007 Petition;
(2) issue a final regulation within 60 days following issuance
of the mandate that either (a) revokes all chlorpyrifos
tolerances or (b) modifies chlorpyrifos tolerances and
simultaneously certifies that, with the tolerances so
modified, the EPA “has determined that there is a reasonable
certainty that no harm will result from aggregate exposure to
the pesticide chemical residue, including all anticipated
dietary exposures and all other exposures for which there is
reliable information,” 171 including for “infants and
children”; 172 and (3) modify or cancel related FIFRA
registrations for food use in a timely fashion consistent with
the requirements of 21 U.S.C. § 346a(a)(1).

   VACATED    AND                         REMANDED,   WITH
INSTRUCTIONS.

BYBEE, Circuit Judge, dissenting:

    This is a consequential proceeding. EPA has before it a
petition to revoke the tolerances for chlorpyrifos, one of the
most important pesticides in the United States. This is a very
complicated statute and I agree with the majority that EPA
dithered far too long before ruling on the petition. Beyond
that, I disagree with the majority opinion and judgment. In

   171
         21 U.S.C. § 346a(b)(2)(A)(ii).
   172
         Id. § 346a(b)(2)(C)(ii)(I).
68   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

my view it has misread EPA’s obligations to review
pesticide chemical residue tolerances EPA has previously
found to be “safe” under the Federal Food, Drug, and
Cosmetic Act (FFDCA), 21 U.S.C. § 346a(b)(2)(A)(i).
Further, the majority has substituted its own judgment for
EPA’s decision and then concluded that, because there is a
difference of opinion, EPA’s decision must be arbitrary and
capricious. See 5 U.S.C. § 706(2)(A). Difference is not
caprice. Finally, among the options Congress entrusted to
EPA when an existing tolerance is determined to be unsafe,
the majority effectively mandates the option that EPA will
enforce.

    As to the first point, I part with the majority over EPA’s
duty with respect to the petition. According to the majority,
EPA must find that chlorpyrifos is safe for human use, and
EPA did not do so here. Maj. Op. at 41–46. EPA did find
chlorpyrifos safe. That was the result of the proceedings in
2006, made final shortly before the present petition was
filed. The question EPA had to answer in this proceeding is
whether new scientific evidence is sufficient to require EPA
to “modify or revoke” its prior determination. Under the
FFDCA, EPA must do so “if the Administrator determines it
is not safe.” 21 U.S.C. § 346a(b)(2)(A)(i) (emphasis added).
Because EPA found that chlorpyrifos was safe when it
concluded its prior rulemaking in 2006, EPA properly
determined here that there was insufficient evidence to
conclude that chlorpyrifos is “not safe” and thus it was not
required to “modify or revoke” those tolerances. EPA does
not start from scratch when it is reviewing a petition to
revoke or modify, but may rely on its prior finding. The
majority would require, contrary to the FFDCA, that EPA
start all over again. I take this point up in Part I.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN            69

    As to the second point, the majority cherry-picks EPA’s
careful and honest questions about the safety of chlorpyrifos
in light of various studies produced in the petition.
Admittedly, it feels like EPA had this question under review
for far too long—through three administrations—but the
majority then assumes EPA’s tentative conclusions are
proven and concludes that it was arbitrary and capricious for
EPA to determine otherwise. However, EPA never
concluded that the studies presented to it were scientifically
established. At every step of its overly cautious proceedings,
EPA referred these studies to its Scientific Advisory Panel
(SAP), which ultimately advised EPA that it could not verify
the studies’ conclusions.         When EPA requested the
underlying data, the studies’ authors declined to produce it.
Left without means of authenticating the studies, EPA
concluded there was insufficient verifiable evidence to
conclude that chlorpyrifos was “not safe” and to require EPA
to modify or revoke its prior approval. The petition failed
for lack of scientifically verifiable evidence. EPA explained
all of this in detail, explained why it needed additional time
to conduct the appropriate inquiries, and advised how it
would proceed through the reregistration required by the
statute. There is nothing arbitrary and capricious about that.
I address this problem in Part II.

     Not only do we decide that EPA’s decision was arbitrary
and capricious, but we have effectively decided the
appropriate remedy. By ordering EPA either to revoke all
tolerances or modify the tolerances with the requisite safety
findings within 60 days, our order virtually guarantees the
EPA will revoke chlorpyrifos tolerances. This is a vast
overreach, a clear abuse of our discretion, as I discuss in Part
III.
70   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

    We can be unhappy with EPA’s dilatory proceedings,
but the remedy for that is a writ of mandamus, which we
issued in League of United Latin American Citizens v.
Wheeler (LULAC III), 922 F.3d 443 (9th Cir. 2019) (en
banc). Now that EPA has complied fully with our directions,
we don’t get to set aside EPA’s decision “simply because
[we are] unhappy with the result reached.” Vt. Yankee
Nuclear Power Corp. v. NRDC, 435 U.S. 519, 558 (1978).
Nor do we get to “second-guess[] the [agency’s] weighing
of risks and benefits.” Dep’t of Com. v. New York, 139 S. Ct.
2551, 2571 (2019). “[A] reviewing court must remember
that” when an agency is acting “within its area of special
expertise, at the frontiers of science,” we “must generally be
at [our] most deferential.” Balt. Gas & Elec. Co. v. NRDC,
462 U.S. 87, 103 (1983). I respectfully dissent.

                               I

    For starters, I fundamentally disagree with the majority
over its construction of the FFDCA. The majority reads
§ 346a(b)(2)(A)(i), which is the critical section of the
FFDCA for setting standards for pesticide use, as creating a
binary choice for EPA: either a tolerance is “safe” or it is
“not safe.” The majority concludes that because EPA did
not conclude that the chlorpyrifos tolerances were “safe”
when it denied the petition, EPA must have concluded that
they were “not safe” and the petition should have been
granted. See Maj. Op. at 41 (EPA “left in effect tolerances
without determining that they are safe . . . .”). With respect,
the majority has misread the statute and its logic. I will start
with some background on the statutes, then turn to how the
majority has misread the statute, and conclude by addressing
two additional arguments the majority makes.
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                71

                                  A

    Let’s start with some background. EPA regulates
pesticides pursuant to two statutes: the Federal Food, Drug,
and Cosmetic Act (FFDCA), 21 U.S.C. § 346a, and the
Federal Insecticide, Fungicide, and Rodenticide Act
(FIFRA), 7 U.S.C. §§ 136a–136y. The provisions relevant
here were adopted as amendments to those Acts in the Food
Quality Protection Act of 1996 (FQPA), Pub. L. No. 104-
170, 110 Stat. 1489 (Aug. 3, 1996). See Nw. Coal. for Alts.
to Pesticides v. EPA, 544 F.3d 1043, 1046 (9th Cir. 2008).
The FFDCA authorizes EPA to regulate pesticides used on
food that pose safety risks to humans and to establish
pesticide tolerance levels “necessary for the protection of
public health.” 21 U.S.C. § 346. FIFRA authorizes EPA to
“limit the distribution, sale, or use” of pesticides “[t]o the
extent necessary to prevent unreasonable adverse effects on
the environment” and issue registrations for distribution or
sale of pesticides. 7 U.S.C. § 136a(a).

    The FFDCA begins with a presumption that all
“pesticide chemical residue in or on a food . . . [is] unsafe.”
21 U.S.C. § 346a(a)(1)(A). If the EPA Administrator
determines that a pesticide is “safe,” the Administrator may
establish a regulatory “tolerance.” 1 A pesticide may be
deemed “safe” if EPA has found “that there is a reasonable

    1
      EPA may also exempt a pesticide from the FFDCA, where either
(1) use of the pesticide protects consumers from greater adverse health
effects than the dietary risk of the pesticide or (2) the pesticide is
necessary to avoid significant disruption in the food supply chain, so
long as aggregate risk is not too high. 21 U.S.C. § 346a(b)(2)(B)(ii)–
(iv).

   Although some of the statutes I will cite here refer to exemptions,
EPA did not consider exemption of chlorpyrifos in this proceeding.
72   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

certainty that no harm will result from aggregate exposure to
the pesticide.” Id. § 346a(b)(2)(A)(i), (ii). The FFDCA has
a separate requirement protecting infants and children. EPA
must separately assess the risk of the pesticide based on
available information concerning consumption patterns,
special susceptibility, and cumulative effects unique to
infants and children. Id. § 346a(b)(2)(C)(i). Based on this
assessment, EPA must “ensure that there is a reasonable
certainty that no harm will result to infants and children from
aggregate exposure” and “publish a specific determination
regarding safety” of the pesticide for infants and children.
Id. § 346a(b)(2)(C)(ii). In making these determinations,
EPA “shall consider . . . the validity, completeness, and
reliability of the available data” and “available information
concerning the relationship of the results of such studies to
human risk.” Id. § 346a(b)(2)(D)(i), (iii).

      In addition to establishing safe tolerance levels for
pesticides under the FFDCA, EPA regulates pesticides under
FIFRA by issuing registrations required for distribution or
sale. 7 U.S.C. § 136a(a). EPA may register a pesticide
where, in addition to other requirements, “it will perform its
intended function without unreasonable adverse effects on
the environment” and “when used in accordance with
widespread and commonly recognized practice it will not
generally cause unreasonable adverse effects on the
environment.” Id. § 136a(c)(5)(C), (D). “Unreasonable
adverse effects on the environment” are unreasonable risks
to man or the environment, including “human dietary risk
. . . inconsistent with the standard under section 346a of Title
21.” Id. § 136(bb). Thus, FIFRA incorporates the FFDCA
safety determination into its registration assessment.

   At the time the FQPA was passed in 1996, there were a
number of existing tolerances in effect. The use of
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                   73

chlorpyrifos, for example, has been federally authorized
since 1965. See Chlorpyrifos; Final Order Denying
Objections to March 2017 Petition Denial Order, 84 Fed.
Reg. 35,555, 35,558 (July 24, 2019) (Final Order). The
FFDCA, as amended by the FQPA, provided that
“[r]egulations that establish tolerances” issued on or before
August 3, 1996, “shall remain in effect unless modified or
revoked.” 21 U.S.C. § 346a(j)(3). The Act also instructed
EPA to “review tolerances and exemptions for pesticide
chemical residues in effect on [August 2, 1996],” and to
determine whether to leave in effect, “modify or revoke”
those tolerances in accordance with the new standards. Id.
§ 346a(q)(1). 2 The FFDCA provided that EPA “shall . . .
modify or revoke the tolerance or exemption if the tolerance
or exemption does not meet such requirements.” Id. The
FFDCA further provided that at any time EPA could, on its
own initiative, issue regulations “establishing, modifying,
. . . or revoking a tolerance for a pesticide . . . .” Id.
§ 346a(e)(1)(A). Once a pesticide has been approved and
registered, FIFRA requires EPA to reevaluate the
registration within 15 years, in this case no later than
October 2022. 7 U.S.C. § 136a(g)(1)(A)(iii), (iv). During
FIFRA reregistration, EPA must decide whether to leave a
tolerance in effect or revoke or modify it.               Id.
§ 136a(g)(1)(A).

    The general standards for establishing, leaving in effect,
modifying, or revoking tolerances are found in
§ 346a(b)(2)(A)(i):

    2
     The FQPA required EPA to review tolerances in existence in 1996
according to a priority schedule. 21 U.S.C. § 346a(q)(1), (2). EPA
placed chlorpyrifos in its first priority group and completed its review in
2006. Final Order, 84 Fed. Reg. at 35,558.
74       LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

           The Administrator may establish or leave in
           effect a tolerance for a pesticide chemical
           residue in or on a food only if the
           Administrator determines that the tolerance is
           safe. The Administrator shall modify or
           revoke a tolerance if the Administrator
           determines it is not safe.

These sentences are awkwardly written. For readability we
can transpose them as follows:

           Only if the Administrator determines that a
           tolerance for a pesticide chemical residue in
           or on a food is safe may the Administrator
           establish or leave in effect the tolerance. 3 If
           the Administrator determines a tolerance is
           not safe, the Administrator shall modify or
           revoke the tolerance.

These standards are consistent with the presumption against
the use of pesticides in food. If EPA determines a pesticide
is safe, then EPA may establish a new tolerance or leave in
place a tolerance previously established. However, if EPA
determines a tolerance is not safe, then EPA shall modify or
revoke the tolerance. Establishing or leaving a tolerance in
place is not mandatory, even if EPA determines that a
pesticide is safe; but if EPA determines a tolerance is not
safe, it must modify or revoke the tolerance.

     3
       This sentence could also be written as “If the Administrator
establishes or leaves in effect a tolerance, then he has determined that the
tolerance is safe.”
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                 75

    When acting on its own initiative or in response to a
petition, 4 the FFDCA requires EPA to consider “the validity,
completeness, and reliability of the available data from
studies of the pesticide” as well as other available
information concerning risks and effects. § 346a(b)(2)(D).
The statute also authorizes EPA to adopt regulations
governing “requirements for information and data to support
a petition to modify or revoke a tolerance.” § 346a(d)(1),
(d)(2)(B). EPA has issued regulations establishing these
requirements and mandating supporting data and studies.
40 C.F.R. § 180.32(b). A petition must be supported by
“reasonable grounds for the action sought,” including “an
assertion of facts (supported by data if available)” that “may
justify [the tolerance’s] modification or revocation.” Id.
§ 180.32(b). The regulations also specify the form and
content required for a petition. Id. § 180.7(b). Under its
regulations, EPA may deny a petition when it finds that a
petition is not supported by “reasonable grounds” for
revocation. Id. § 180.32(b).

                                   B

    Now to the majority’s errors. The majority reads
§ 346a(b)(2)(A)(i) as creating a binary choice, an “either/or”
scenario: either a tolerance is “safe” or it is “not safe.” For
the majority, there is no middle ground. See Maj. Op. at 13,
(“If a tolerance is not safe—in other words, if the EPA
cannot determine that there is a reasonable certainty of no
harm across all sources of exposure for infants, children, and
adults—then the EPA no longer has discretion.”), 62–63

    4
       The FFDCA provides a mechanism for interested persons to
petition EPA to “propos[e] the issuance of a regulation establishing,
modifying, or revoking a tolerance for a pesticide chemical residue in or
on a food.” Id. § 346a(d)(1)(A).
76   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

(“EPA has not determined . . . that aggregate chlorpyrifos
exposures under the current tolerances pose no risk of harm.
Therefore, by statutory definition, the present tolerances are
not safe.”). The majority’s logic is irrefutable because the
statement is, of course, a tautology. But as a tautology it is
not helpful, because it doesn’t tell us anything about the
actual state of affairs. As Ludwig Wittgenstein once
commented, “I know nothing about the weather when I know
that it rains or does not rain.” 5 The problem with the
majority’s reasoning is, in a phrase, the fallacy of the
excluded middle. See Wall v. Mich. Rental, 852 F.3d 492,
496 (6th Cir. 2017) (“[A] statement of two contradictory
facts [is] a statement of nothing at all under a venerable
principle of logic—the law of the excluded middle.”); Miller
v. Henman, 804 F.2d 421, 426 (7th Cir. 1986) (rejecting the
“Law of the Excluded Middle” in favor of “a third
alternative”). It is true that § 346a(b)(2)(A)(i) uses the terms
“safe” and “not safe.” But the context for the terms is
different. The terms are opposites, but they do not exhaust
the possible outcomes.

    We should be familiar with the problem of the excluded
middle from other areas of law and life. For example,
“guilty” and “not guilty,” as logical opposites, describe the
universe, so long as we don’t care about factual innocence.
But if we do, we have to consider a third alternative. Thus,
we have examples where courts have gone beyond the binary
thinking of guilty/not guilty to declare persons “factually
innocent.” See Humphries v. Cnty. of L.A., 554 F.3d 1170,
1181–82 & nn. 6, 8 (9th Cir. 2009) (discussing the legality
and effect of findings of “factually innocent” by a California
criminal court and “not true” by a California juvenile court

    5
      Ludwig Wittgenstein, Tractatus Logico-Philosophicus, quoted in
Joseph G. Brennan, A Handbook of Logic 160 (2d ed. 1961).
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN            77

in a child abuse case), rev’d in part on other grounds, Cnty.
of L.A. v. Humphries, 562 U.S. 29 (2010). Other countries
offer juries the option of a third verdict. See Samuel L. Bray,
Comment, Not Proven: Introducing a Third Verdict, 72 U.
Chi. L. Rev. 1299, 1299–1300 (2005) (“Not proven and not
guilty are both acquittals, indistinguishable in legal
consequence but different in connotation. Not guilty is for a
defendant the jury thinks is innocent; not proven, for a case
with insufficient evidence of guilt”; citing Scottish law as an
example). In football, a ruling may be overturned only if
there is indisputable evidence that it was wrong. But what if
the ruling is not indisputably wrong? Do we care if it was
correct, or just “not wrong”? Turns out that we do. The
presumption will lie with the official who made the call. If
the ruling cannot be overturned, “the ruling on the field
stands.” But if the ruling on the field is correct, then “the
ruling on the field is confirmed.” See NCAA Football Rules
Book R. 12, § 6, art. 1.d (2019) (distinguishing three options:
“the ruling on the field is confirmed,” “the ruling on the field
stands,” and reversing a ruling). There is no practical
difference in the immediate effect on the game between “the
ruling on the field stands” and “the ruling on the field is
confirmed,” but there are collateral consequences for
officials and for the lively debates among the fans that
inevitably follow in close games.

    The majority’s premise that a pesticide is either “safe” or
“not safe” ignores an important alternative—namely, that
there is insufficient information to reach either of those
conclusions. That is why Congress instructed EPA to
consider “the validity, completeness, and reliability of the
available data”—it understood that the evidence might be
inconclusive. 21 U.S.C. § 346a(b)(2)(D)(i). That is also
why § 346a(b)(2)(A)(i) allocates a burden of persuasion. I
hesitate to use the term “burden of proof” because it suggests
78   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

that EPA and petitioners are adverse to each other; they are
not. EPA is responsible for regulating pesticide use and, as
a court, we assume that it has developed an expertise. We
also assume that EPA will be an honest broker in assessing
the safety of a pesticide; after all, agency employees have to
eat the same food we do. So instead of “burden of proof,” I
am going to use the term “risk of nonpersuasion.”

    Here is how the risk of nonpersuasion figures into the
FFDCA. When EPA receives a petition, it has a duty of
inquiry, but it is a different duty depending on whether the
decision on the table is whether to establish or leave in effect
a tolerance (the first sentence of § 346a(b)(2)(A)(i)) or to
modify or revoke a tolerance (the second sentence in that
subsection). EPA (or a petitioner) has the initial burden to
show that a proposed tolerance can be safely established. If
the proposal does not satisfy that standard, EPA cannot adopt
the proposed tolerance. EPA has the same burden when it
considers an existing tolerance for reregistration. Recall that
when the FQPA was adopted in 1996, that Act tightened the
standards for pesticides. Because EPA had approved
pesticides in use, the FQPA required EPA to review and
reregister all existing tolerances to determine whether to
“leave in effect” those tolerances. 21 U.S.C. §§ 346a(j)(3),
(q)(1).     Additionally, the FQPA, amending FIFRA,
mandated that following that reregistration, EPA must
review existing tolerances no less frequently than every
15 years. 7 U.S.C. § 136a(a), (g)(1)(A)(iv). In these
reregistration proceedings, EPA must conclude that the
existing tolerance is “safe” before it can “leave [it] in effect.”
21 U.S.C. § 346a(b)(2)(A)(i). What happens if the evidence
is inconclusive? Since there is a presumption that all
pesticides are “unsafe,” id. § 346a(a)(1), the risk of
nonpersuasion means that EPA must either approve the
tolerance or exempt it under other provisions of the FFDCA,
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN             79

see id. § 346a(a)(1)(A), (B).              As I transposed
§ 346a(b)(2)(A)(i) for readability, “only if the Administrator
determines that the tolerance is safe may [the Administrator]
establish or leave in effect a tolerance.”

    By contrast, when a petitioner requests modification or
revocation of an existing tolerance, the risk of nonpersuasion
cuts in the opposite direction. EPA has previously found the
tolerance to be “safe.” If EPA subsequently determines that
the pesticide is “not safe,” then it must modify or revoke the
tolerance. What happens if the evidence is inconclusive?
The risk of nonpersuasion means that EPA may, but does not
have to, modify or revoke the tolerance.                Section
346a(b)(2)(A)(i) is clear (as I have revised it for readability):
“If the Administrator determines a tolerance is not safe, the
Administrator shall modify or revoke the tolerance.”
Accordingly, when a petitioner files an appropriate petition
claiming that a tolerance is not safe, EPA assumes a duty of
inquiry, but not a duty of declaring anew that the tolerance
is “safe.” Here is the crucial distinction: determining that a
tolerance is “not safe” is not the same as not determining
that a tolerance is “safe.” The majority’s either/or approach
has excluded the middle. As the First Circuit explained,
albeit in a different context:

        Confronted by such conflict a reasonable
        person investigates matters further; he
        receives assurances or clarification before
        relying. A reasonable person does not
        gamble with the law of the excluded middle,
        he suspends judgment until further evidence
        is obtained. Explicit conflict engenders
        doubt, and to rely on a statement the veracity
        of which one should doubt is unreasonable.
        The law does not supply epistemological
80   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

        insurance. Nor does it countenance reliance
        on one of a pair of contradictories simply
        because it facilitates the achievement of
        one’s goal.

Trifiro v. Nw. York Life Ins. Co., 845 F.2d 30, 33–34 (1st Cir.
1988).

    The majority’s either/or treatment of § 346a(b)(2)(A)(i)
has two important consequences. First, it effectively reads
the second sentence of that subsection out of the statute
because, in the majority’s understanding, EPA always has
the burden to show that a tolerance is “safe,” which means
that it is, by definition, not “not safe.” Or, to put it another
way, in the majority’s view, if at any time EPA does not
affirmatively declare that a tolerance is “safe,” the tolerance
is, again by definition, “not safe.” Under the majority’s
reading, the second sentence of § 346a(b)(2)(A)(i) doesn’t
do any work because in order to determine that a tolerance
is “not safe” EPA must decide that it is not “safe.” In other
words, for the majority, in every case EPA has a duty of
reregistration. The reason the majority has committed this
error of logic is that it fails to appreciate the different context
for the two sentences in § 346(b)(2)(A)(i). In the first
sentence, the presumption runs against the tolerance because
EPA is required to establish or reregister (“leave in effect”)
the tolerance. In the second sentence, EPA has already
determined that the tolerance is “safe,” so the question is
whether there is enough evidence to show that it is “not
safe.” When EPA denies a petition for insufficient evidence,
it may rely on its prior determination that the tolerance is
“safe.” The two sentences operate in different contexts.

    Second, the majority’s reading means that petitioners can
seize control of the statutory schedule for reviewing existing
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN             81

tolerances. Under the FQPA, EPA had to review all existing
tolerances, such as chlorpyrifos, under the new standard.
And it had to do so “as expeditiously as practicable,” but no
later than 2006. 21 U.S.C. § 346a(q)(1). This EPA did in
2006, leaving in effect the chlorpyrifos tolerance. Under the
FIFRA and the FFDCA, EPA would have to reevaluate
chlorpyrifos for reregistration no later than October 2022.
See 7 U.S.C. § 136a(g)(1)(A)(iv); Final Order, 84 Fed. Reg.
at 35,558. In the interim, any interested person may petition
EPA to modify or revoke the tolerance. Under the majority’s
reading of the FFDCA, to respond to the petition, EPA must
either reregister chlorpyrifos as “safe” or modify or revoke
the tolerance—but in either case the petition has altered the
statutory review process for chlorpyrifos. Since petitioners
can file petitions at will, EPA has lost control over its docket,
and the statutory schedule has been derailed. As EPA put it,
if

        EPA were required to truncate its ongoing
        registration review process to make a new
        FFDCA safety finding every time it received
        a petition to modify or revoke tolerances,
        petitioners would effectively have the
        authority to re-order the Administrator’s
        scheduling of registration review decisions
        under FIFRA and dictate the extent of inquiry
        EPA may put to a matter before reaching a
        resolution.

Final Order, 84 Fed. Reg. at 35,565.

                               C

    Despite the (relative) clarity of these provisions, the
majority makes two arguments to get around this reading of
§ 346a(b)(2)(A)(i). First, the majority holds that any time
82   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

EPA considers a petition to modify or revoke an existing
tolerance (which is governed by the second sentence of
§ 346a(b)(2)(A)(i)), it is “leav[ing] in effect” the tolerance
(which is governed by the first sentence). Maj. Op. at 41–
42. It concludes that EPA has “a continuous duty” under the
FFDCA “to ‘leave in effect’ a tolerance ‘only’ if it finds it is
safe.” Id. at 42. Second, the majority claims that once EPA
accepted the petition, because it was not “wholly frivolous,”
EPA had an independent duty to determine whether
chlorpyrifos is “safe” and cannot now claim that the petition
was “somehow inadequate.” Id. at 42, 47. Neither point
withstands scrutiny.

    The majority’s focus on EPA “leaving in effect” the
chlorpyrifos tolerance misconceives the proceedings. Under
the FFDCA, any petitioner had the right to petition EPA to
“establish[], modify[] or revok[e]” a tolerance. 21 U.S.C.
§ 346a(d)(1)(A). “Leave in effect” is not mentioned as an
option in the petition subsection, and for good reason: “leave
in effect” has a particular context and meaning in the
FFDCA. As I have explained, prior to the adoption of the
FQPA in 1996, which established the current statutory
standards in the FFDCA, there were tolerances in place for
pesticides such as chlorpyrifos. The FQPA imposed a duty
and a schedule on EPA to review all existing tolerances and
to decide whether to “leave in effect” those tolerances.
21 U.S.C. § 346a(q)(1).       See also id. § 346a(l)(3)(B)
(explaining if EPA suspends a tolerance it “shall not be
considered to be in effect,” but if the suspension is
terminated, “leaving the registration of the pesticide for such
use in effect,” EPA must rescind the suspension). Because
the prior tolerances were not established under the same
standards demanded by the FFDCA, as amended by the
FQPA, EPA had to determine afresh that the preexisting
tolerances were “safe.” With respect to that review, EPA
      LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                     83

could “leave in effect a tolerance . . . only if the
Administrator determines that the tolerance is safe.” Id.
§ 346a(b)(2)(A)(i). Under FIFRA, EPA must also re-certify
its tolerances no less than every 15 years and decide whether
to leave a tolerance in effect or modify or revoke it. 7 U.S.C.
§ 136a(g)(1)(A). 6 The majority has conflated EPA’s
responsibility with respect to the preexisting tolerances with
its responsibility when it reviews a petition.

    The majority reaches its conclusion because it reads
§ 346a(b)(2)(A)(i) in isolation from the rest of the statute.
That leads the majority to consider a dictionary definition of
the phrase. Maj. Op. at 42. Dictionaries can be useful for
understanding terms. Here, recurring to a dictionary is
neither necessary nor useful, because the term “leave in
effect” is not ambiguous when it is read in context with the
remainder of the statute. See Carson Harbor Vill., Ltd. v.
Unocal Corp., 270 F.3d 863, 878 (9th Cir. 2001) (en banc)

     6
       Contrary to the majority’s statements, FIFRA incorporates the
FFDCA’s standards. See 7 U.S.C. § 136(bb) (referring to “the standard
under Section 346a of Title 21”). As part of its reregistration
requirements for licensing, FIFRA requires EPA to review its FFDCA
standards no less than every 15 years. See Final Order, 84 Fed. Reg.
at 35,557 (“In the FQPA, Congress integrated action under the two
statutes by requiring that the safety standard under the FFDCA be used
as a criterion in FIFRA registration actions for pesticide uses that result
in residues in or on food.”). Because FIFRA requires periodic
recertification under FFDCA, the FFDCA standard governs
chlorpyrifos’s use, independent of anything required for licensing under
FIFRA. The majority repeatedly misses this point. See Maj. Op. at 43–
44 (“[EPA’s claim that reregistration is required by FIFRA] is
unpersuasive because of the differences between FIFRA and the
FFDCA. The statutes impose different duties that require different
assessments.”), 51 (“FIFRA registration review . . . is a different animal,
in that it permits a balancing of multiple factors, whereas a FFDCA
review is limited to the sole issue of safety . . . .”).
84   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

(“Where the language is plain and admits of no more than
one meaning the duty of interpretation does not arise, and the
rules which are to aid doubtful meanings need no
discussion.” (quoting Caminetti v. United States, 242 U.S.
470, 485 (1917)); see also Hughes Aircraft Co. v. Jacobson,
525 U.S. 432, 438 (1999) (“[W]here the statutory language
provides a clear answer, [the inquiry] ends there . . . .”);
Robinson v. Shell Oil Co., 519 U.S. 337, 340 (1997) (“Our
inquiry must cease if the statutory language is unambiguous
and the statutory scheme is coherent and consistent.”
(internal quotation marks and citations omitted)); United
States v. Williams, 659 F.3d 1223, 1225 (9th Cir. 2011) (“If
the plain meaning of the statute is unambiguous, that
meaning is controlling . . . .”). When the statute offers a
definition of a term, the statutory definition—even if it is a
functional usage—governs. Carson Harbor Vill., 270 F.3d
at 878 (“When a statute includes an explicit definition,
however, we must follow that definition, even if it varies
from that term’s ordinary meaning.” (quoting Stenberg v.
Carhart, 530 U.S. 914, 942 (2000) (alteration omitted)); see
also United States v. Havelock, 664 F.3d 1284, 1289 (9th
Cir. 2012) (en banc) (“Statutory construction must begin
with the language employed by Congress and the assumption
that the ordinary meaning of that language accurately
expresses the legislative purpose.           That assumption,
however, does not apply where Congress provides a
statutory definition.” (internal citations and quotation marks
omitted)). The FFDCA, as amended by the FQPA, is quite
clear that “leave in effect” refers to a particular kind of
proceeding mandated by Congress.

    That brings us to the majority’s second point. The
majority attempts to shift the risk of nonpersuasion through
a contorted reading of EPA’s regulations regarding the filing
of a petition. According to the majority, EPA has a
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN          85

“gatekeeping authority to reject a wholly frivolous petition.”
Maj. Op. at 47. But if EPA accepts a petition, it “trigger[s]
the EPA’s duty to ensure a reasonable certainty of no harm”
by re-evaluating chlorpyrifos and, if it decides to “leave in
effect” the tolerance, it must certify chlorpyrifos as “safe.”
Id. According to the majority, accepting a petition flips the
risk of nonpersuasion. But EPA’s regulations say nothing of
the kind.

    In an exercise of its “gatekeeping authority,” EPA has
adopted “Procedure for modifying and revoking tolerances
or exemptions from tolerances.” 40 C.F.R. § 180.32. That
regulation provides in relevant part:

       Any person may file with the Administrator a
       petition proposing the issuance of a
       regulation modifying or revoking a tolerance
       or exemption from a tolerance for a pesticide
       chemical residue. The petition shall furnish
       reasonable grounds for the action sought.
       Reasonable grounds shall include . . . an
       assertion of facts (supported by data if
       available) showing that new uses for the
       pesticide chemical have been developed or
       old uses abandoned, that new data are
       available as to toxicity of the chemical, or
       that experience with the application of the
       tolerance or exemption from tolerance may
       justify its modification or revocation.

Id. § 180.32(b). There is not a word in the regulation that
would affect the risk of nonpersuasion. The regulation
requires little to be a qualifying petition: “reasonable
grounds,” including “an assertion of facts” which shall be
“supported by data if available.” Id. (emphasis added). That
86    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

is the most modest of rules. EPA will generously accept
such petitions and consider them. Accepting a petition—
which in the majority’s phrase means that they are not
“wholly frivolous” 7—is the lowest of bars. This is as it
should be. We want interested persons—“any person”—to
be able to go to EPA and suggest that it take a second look
at a tolerance for a pesticide going on our food. But the
majority takes EPA’s decision to accept the petition as
nullifying EPA’s prior decision to approve the tolerance;
effectively, EPA must start all over again. That’s not how
administrative law usually works. Under the FFDCA, EPA
must modify or revoke the tolerance if it is “not safe.” The
majority would require EPA to prove that the tolerance is
“safe.”

    Although EPA’s Final Order was overdue, there was
nothing improper in its form. EPA denied the petition and
instead relied upon its 2006 safety determination for
chlorpyrifos tolerances because it found that the data and
studies supporting the petition were “not sufficiently valid,
complete, and reliable” to support revocation. Final Order,
84 Fed. Reg. at 35,562–63. In other words, the data
supporting the petition was not sufficient to support a
determination that chlorpyrifos tolerances are “not safe.”
21 U.S.C. § 346a(b)(2)(A)(i).

    The FFDCA does not require EPA to make a new safety
determination in response to a petition supported solely by
studies that EPA has already considered and found
insufficient for revocation while conducting its FIFRA
review. Here, EPA considered the petition’s cited studies at
multiple instances during its own review and found that they

    7
      So far as I can tell, the phrase “wholly frivolous” belongs to the
majority.
     LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN          87

were not reliable enough to support revocation without more
information. See Final Order, 84 Fed. Reg. at 35,563. The
agency’s determination that the petition did not present
sufficiently valid, complete, or reliable information to
support revocation is thus supported by the record. See
§ 346a(b)(2)(D). Because the 2007 petition did not present
reasonable grounds for modification or revocation, EPA was
entitled to rely upon its 2006 safety finding while it engaged
in its FIFRA review of chlorpyrifos tolerances. The
tolerance had already been deemed “safe,” and the petition
did not raise sufficient grounds to overcome that
presumption.

     Under a correct reading of the statute, and proper
allocation of the risk of nonpersuasion, we should be
reviewing EPA’s determination that the petition, and the
evidence it mustered, was insufficient to determine that the
chlorpyrifos tolerance is “not safe.” That is not the inquiry
the majority conducts, so in Part II I will review the
proceedings before EPA, as punctuated by our orders, and
its Final Order, which is the only decision we have authority
to review. 5 U.S.C. § 704.

                              II

    EPA’s denial of the 2007 petition was not arbitrary or
capricious. The denial of the petition did not conflict with
any final agency findings or conclusions and, to the contrary,
was supported by the extensive record of EPA’s concerns
with the petition’s supporting studies over the course of
nearly a decade. The only final agency action in effect for
chlorpyrifos tolerances is the 2006 safety determination, and
EPA’s denial of the petition comports with this
determination.
88    LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

    I will begin with a brief review of EPA’s 2006–17
proceedings, with some emphasis on the questions and
qualifications EPA raised at each step of those proceedings.
I will then turn to the Final Order and our review under the
APA.

                             A

    In 2006, pursuant to the FFDCA, EPA completed a
tolerance reassessment of chlorpyrifos and found that
chlorpyrifos was eligible for reregistration and met the
standard of 21 U.S.C. § 346a(b)(2). EPA, Office of
Prevention, Pesticides and Toxic Substances, Memo to Jim
Jones from Debra Edwards, Finalization of Interim
Reregistration Eligibility Decisions and Interim Tolerance
Reassessment and Risk Management Decisions for the
Organophosphate Pesticides, and Completion of the
Tolerance Reassessment and Reregistration Eligibility
Process for the Organophosphate Pesticides (July 31, 2006)
(2006 Reregistration Decision); see also Final Order,
84 Fed. Reg. at 35,558. In doing so, EPA found that
chlorpyrifos tolerances were safe and left them in effect.

     1. The Petition is filed; EPA conducts various studies
        for reregistration

    In September 2007, the Pesticide Action Network North
America (PANNA) and the National Resources Defense
Council (NRDC) filed a petition with EPA to revoke all
tolerances for chlorpyrifos based on new studies purporting
to show that current chlorpyrifos tolerances were not safe.
See Petition to Revoke All Tolerances and Cancel All
Registrations for the Pesticide Chlorpyrifos; Notice of
Availability, 72 Fed. Reg. 58,845 (Oct, 17, 2007); see also
Final Order, 84 Fed. Reg. at 35,556. Petitioners raised ten
claims alleging numerous errors in the 2006 Reregistration
        LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN                  89

Decision, including claims that EPA ignored or
misinterpreted data. 8 EPA was able to resolve seven of the
ten claims relatively quickly. In July 2012 and July 2014,
EPA issued interim responses indicating its intent to deny all
but the three claims at issue here (grounds 7–9 in the
petition), and it informed Petitioners of its intent to finalize
all interim conclusions (grounds 1–6, and 10) when it
resolved the remaining three claims, a decision to which
Petitioners did not object. Final Order, 84 Fed. Reg. at
35,556; see also In re Pesticide Action Network North
America (PANNA I), 532 F. App’x 649 (9th Cir. 2013)
(denying petition for mandamus). The three claims not
addressed by EPA in those responses were interrelated and
concerned the potential for chlorpyrifos exposure at current
tolerance levels to cause neurodevelopmental effects in
children. Final Order, 84 Fed. Reg. at 35,556. However,
EPA did not give these claims short shrift. Instead, early in
its review, in 2009, the agency found the issues raised
important enough questions that they should be addressed as
part of an accelerated reregistration review of chlorpyrifos.
Id. at 35,556 (noting that these claims “raised novel, highly
complex scientific issues” that should be addressed in EPA’s

    8
       Petitioners alleged that EPA: (1) “ignored genetic evidence of
vulnerable populations”; (2) “needlessly delayed a decision regarding
endocrine disrupting effects”; (3) “ignored data regarding cancer risks”;
(4) “misrepresented risks and failed to apply FQPA 10X safety factor”
in its 2006 cumulative risk assessment; (5) “over-relied on registrant
data”; (6) “failed to properly address the exporting hazard in foreign
countries from chlorpyrifos”; (7) “failed to quantitatively incorporate
data demonstrating long-lasting effects from early life exposure to
chlorpyrifos in children”; (8) “disregarded data demonstrating that there
is no evidence of a safe level of exposure during pre-birth and early life
stages”; (9) “failed to cite or quantitatively incorporate studies and
clinical reports suggesting potential adverse effects below 10%
cholinesterase inhibition”; and (10) “failed to incorporate inhalation
routes of exposure.” Final Order, 84 Fed. Reg. at 35,556.
90   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

expedited reregistration review). Despite its 2022 statutory
deadline, EPA announced that it planned to prioritize review
of chlorpyrifos and complete reevaluation by 2015, years
ahead of schedule. Id. at 35,558. However, this review
proved to be complex, particularly with regard to the
potential human health risks and neurodevelopmental effects
of chlorpyrifos tolerances. Id.

    In the interim, EPA convened scientific panels to
evaluate the evidence and published reports. In 2008, as part
of its reregistration review, EPA published a Science Issue
Paper addressing chlorpyrifos hazards. EPA, Office of
Pesticide Programs, Science Issue Paper: Chlorpyrifos
Hazard and Dose Response Characterization (Aug. 21,
2008). The paper summarized “data relevant to infants,
children, and pregnant women,” interpreted this data, and
suggested alternatives for updating the mechanism used to
assess chlorpyrifos tolerance safety. Id. at 7. The paper
“preliminarily concluded that chlorpyrifos likely played a
role in” adverse health effects in children. Id. at 52.
However, the paper specifically noted that there had not been
“a full and complete risk assessment/characterization” of the
human health risks of chlorpyrifos and that “the [EPA] has
not developed any final conclusions regarding updates to the
chlorpyrifos hazard assessment.” Id. at 7.

    Later that year, EPA convened a Science Advisory Panel
(SAP or the Panel), a federal advisory committee
“established under the provisions of FIFRA” that “serves as
the [EPA’s] primary scientific peer review mechanism” for
pesticide matters, to peer review the paper. EPA, SAP
Minutes No. 2008-04: A Set of Scientific Issues Being
Considered by the Environmental Protection Agency
Regarding: The Agency’s Evaluation of the Toxicity Profile
of Chlorpyrifos 2 (Sept. 16–18, 2008). The SAP also
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considered several new studies concerning the risk of
chlorpyrifos to pregnant women and children. The SAP’s
evaluation noted that “Panel members were concerned that a
high degree of uncertainty is evident in the available data
. . . .” Id. at 10. First, the Panel expressed concerns about
several laboratory studies involving live rodents and the
meaning of phrases used and experimental methods
employed, and concluded that this data was “insufficient.”
Id. at 11–12. The Panel also considered three epidemiology
studies, referred to as the Mt. Sinai, CHAMACOS, and
Columbia University studies. The Columbia Study, which
assessed chlorpyrifos risk to pregnant women, infants, and
children, commanded particular attention. Id. at 12. The
Panel found defects in all three of the studies, including
concerns that the Columbia Study—the most robust of the
three—did not provide sufficient data to be the sole factor
for risk assessment or modifying tolerances and produced
uncertainty through its measurement method. Id. at 12–13,
32–35, 43–44. Although the SAP found that the studies
“raise concerns,” the SAP also agreed that the studies were
inconclusive. Id. at 13–14. The SAP concluded that
“chlorpyrifos could have contributed to the birth and
neurodevelopmental outcomes” indicated in the studies, but
“that due to their limitations, the epidemiological data
currently available are useful primarily for hazard
identification.” Id. at 13.

    In 2011, EPA published a Preliminary Human Health
Risk Assessment (PHHRA) for chlorpyrifos as part of its
forthcoming FIFRA review. EPA, Office of Chemical
Safety & Pollution Prevention, Chlorpyrifos: Preliminary
Human Health Risk Assessment for Registration Review 1–
2 (June 30, 2011). This assessment again considered the
laboratory and epidemiology studies evaluated by the 2008
SAP and similarly noted their limitations. Id. at 29–34. The
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PHHRA also considered developments since the 2008 SAP,
including new data and follow-up analysis on the Columbia
Study that had been recommended by the Panel. Id. at 34.
EPA came to no definitive conclusion in the PHHRA, instead
stating that analyses were ongoing and the final assessment
would

        be based on a full scientific weight of
        evidence approach that considers the best
        available science and integrates all key lines
        of evidence, from empirical animal
        toxicology     to    observational     human
        epidemiology studies, in an integrated
        framework analysis and will transparently
        address and clearly characterize the strength
        of the evidence and areas of remaining
        uncertainty and variability.

Id. at 42.

    In April 2012, EPA again convened the SAP to consider
the health effects of chlorpyrifos. EPA, SAP Minutes 2012-
04: A Set of Scientific Issues Being Considered by the
Environmental Protection Agency Regarding Chlorpyrifos
Health Effects (April 10–12, 2012). The SAP recognized “a
growing body of literature with laboratory animals (rats and
mice) indicating that gestational and/or early postnatal
exposure to chlorpyrifos may cause persistent effects into
adulthood” and epidemiology studies “that have reported
associations      with     birth    outcomes,    childhood
neurobehavioral and neurodevelopment outcomes.” Id.
at 10. In addition to nine new laboratory studies, the 2012
SAP reviewed the same laboratory studies evaluated by the
2008 SAP, again noting the laboratory studies’ limitations
and “recommend[ing] these experimental outcomes be
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regarded as exploratory, and hypothesis-generating, as
opposed to being evidence of toxicity.” Id. at 15. However,
the Panel found that, despite concerns about the studies, “the
collective weight of evidence from these studies demonstrate
that it is probable that there are significant long-term adverse
effects from chlorpyrifos exposure.” Id. at 16. The 2012
SAP likewise considered the same epidemiology studies
analyzed by the 2008 SAP, recognizing their strengths and
limitations. Id. at 17–18, 48–50. The Panel noted that the
epidemiological studies indicated “that chlorpyrifos likely
plays a role in impacting the neurodevelopmental outcomes
examined in the three cohort studies” but proposed further
study because “the data generated from these studies alone
are not adequate enough” to make a definitive risk
assessment. Id. at 18–19. The SAP advised EPA to “explore
additional ways of using these studies” and conduct
additional research. Id. at 19–20.

    In December 2014, EPA published a Revised Human
Health Risk Assessment (2014 RHHRA) for chlorpyrifos.
EPA, Office of Chemical Safety & Pollution Prevention,
Chlorpyrifos: Revised Human Health Risk Assessment for
Registration Review (Dec. 29, 2014).              This revised
assessment incorporated comments on the preliminary
assessment and included assessment of new data. Id. at 5.
The 2014 RHHRA found that data, including the laboratory
and epidemiology studies, “indicate that chlorpyrifos likely
played a role in the neurodevelopmental outcomes reported
by the epidemiologic study (Columbia University)
investigators” but that “uncertainties . . . preclude definitive
causal inference.” Id. at 6. Yet again, EPA noted that the
studies reflected both strengths and “notable limitations.”
Id. at 43. In this assessment, EPA also revised its approach
to calculating chlorpyrifos “points of departure,” or the
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ceiling for safe exposure to a pesticide based on these
studies. Id. at 40, 62–70, 131.

    In January 2015, EPA announced the availability of the
2014 RHHRA and sought public comments on “the Agency’s
risk assessment methodologies and assumptions . . . [and]
suggestions for mitigating any risks identified in the [2014
RHHRA].” Chlorpyrifos Registration Review; Revised
Human Health Risk Assessment; Notice of Availability,
80 Fed. Reg. 1,909, 1,910 (Jan. 14, 2015). Additionally, in
March 2015, EPA advised counsel for the petitioners by
letter that it intended to deny the three unresolved claims in
the 2007 Petition—the claims at issue in this appeal. EPA,
Office of Chemical Safety & Pollution Prevention, Re:
Chlorpyrifos Petition Dated September 12, 2007; March
2015 Provisional Response (Mar. 26, 2015).               EPA
incorporated its prior partial petition responses from 2012
and 2014, which denied seven of the ten claims raised in the
petition. Id. With respect to the three remaining claims,
which were those related to infants and children and based
on the Columbia, Mount Sinai, and CHAMACOS studies,
EPA advised counsel that “EPA does not believe the claims
raised in your petition establish a basis to revoke all
chlorpyrifos tolerances and cancel all chlorpyrifos
registrations.” Id. at 3. The letter noted that EPA had “risk
concerns” with exposure to chlorpyrifos in drinking water,
but it was seeking comment on its 2014 RHHRA and would
“take appropriate action under the FFDCA and/or FIFRA to
ensure that exposures to chlorpyrifos are consistent with the
requirements of those statutes.” Id. at 3–4.

     2. We issue mandamus; EPA proposes to revoke the
        tolerances

   Six months later, in August 2015, we issued a writ of
mandamus ordering EPA “to issue either a proposed or final
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revocation rule or a full and final response to the
administrative petition.” In re Pesticide Action Network
North America (PANNA II), 798 F.3d 809, 815 (9th Cir.
2015). In response, EPA issued a proposed rule to revoke
all chlorpyrifos tolerances because “EPA cannot, at this
time, determine that aggregate exposure to residues of
chlorpyrifos, including all anticipated dietary exposures and
all other non-occupational exposures for which there is
reliable information, are safe.” Chlorpyrifos; Tolerance
Revocations, 80 Fed. Reg. 69,080, 69,080–81 (Nov. 6, 2015)
(2015 Proposed Rule). EPA advised that it was issuing the
proposed rulemaking because of our mandamus order and
that the proposal was “in advance of [EPA] completing its
refined drinking water assessment.” Id. at 69,083. EPA
explained that it “believe[d] that acute dietary risk from food
only does not present a significant risk” and that “EPA
would therefore not be proposing the revocation of
chlorpyrifos if dietary exposures were confined to food.” Id.
at 69,096–97. The basis for the proposed revocation was
instead new data indicating that “for some portions of the
country, food exposures, when aggregated with residential
exposures and potentially more significant drinking water
exposures, do present a significant risk concern and support
revocation of all chlorpyrifos tolerances.” Id. at 69,097. At
the same time, EPA stated that it had “insufficient time to
address comments received on the [2014] RHHRA,” and it
would “update this action . . . as EPA completes additional
work.” Id. at 69,083. EPA also cautioned that its analysis
was incomplete and that it might yet modify the proposed
rule based on the completed analysis and comments. Id. We
then ordered EPA to take final action on the proposed rule
and on PANNA and NRDC’s petition no later than
December 30, 2016. In re Pesticide Action Network North
America (PANNA III), 808 F.3d 402, 403 (9th Cir. 2015).
96   LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

    In March 2016, EPA published a new Chlorpyrifos Issue
Paper and solicited comment from the SAP regarding
changing points of departure based solely on
neurodevelopmental effects measured by the Columbia
Study. EPA, Office of Pesticide Programs, Chlorpyrifos
Issue Paper: Evaluation of Biomonitoring Data from
Epidemiology Studies 9 (Mar. 11, 2016) (2016 Issue Paper).
At the time EPA had proposed to revoke chlorpyrifos
tolerances, “EPA had not completed a refined drinking water
assessment or additional analysis of the hazard from
chlorpyrifos that was suggested by several commenters.”
EPA, Office of Chemical Safety & Pollution Prevention,
Chlorpyrifos: Revised Human Health Risk Assessment for
Registration Review 3 (Nov. 3, 2016) (2016 RHHRA). After
engaging in additional research, EPA—in this Issue Paper—
proposed using different “toxicological points of departure”
based on data from the Columbia Study, and sought the
advice of the 2016 SAP on this new approach. 2016 Issue
Paper at 9.

    In April 2016, the SAP convened to review the Issue
Paper. EPA, SAP Minutes No. 2016-01: A Set of Scientific
Issues Being Considered by the Environmental Protection
Agency Regarding: Chlorpyrifos: Analysis of Biomonitoring
Data (April 19–21, 2016) (2016 SAP Minutes). The SAP
expressed significant disagreement with the substance of the
paper, including a lack of confidence that the Columbia
Study “c[ould] accurately be used” in determining new
points of departure. Id. at 18. The panel “thought the quality
of the [Columbia Study] data is hard to assess when raw
analytical data have not been made available, and the study
has not been reproduced.” Id. The SAP noted that review
of the raw data from the Columbia Study could resolve some
uncertainty regarding the study’s conclusions. Id. at 20.
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    By mid-2016, claiming “extraordinary circumstances,”
EPA requested a six month extension on our order of final
action. In re Pesticide Action Network North America
(PANNA IV), 840 F.3d 1014, 1015 (9th Cir. 2016). EPA
advised us that it had “issued its proposed rule before
completing two studies that may bear on the Agency’s final
rule.” Id. at 1015. We characterized EPA’s request as
“another variation on a theme ‘of partial reports, missed
deadlines, and vague promises of future action.’” Id.
(quoting PANNA II, 798 F.3d at 811). We denied EPA’s
request and ordered final action by March 31, 2017. Id.

    In November 2016, EPA released yet another Revised
Human Health Risk Assessment, responding to the 2016
SAP’s concerns. EPA, Office of Chemical Safety &
Pollution Prevention, Chlorpyrifos: Revised Human Health
Risk Assessment for Registration Review (Nov. 3, 2016)
(2016 RHHRA). EPA recounted that in 2013 it had sought
the raw data used in the Columbia Study, and although the
researchers would not agree to provide EPA with the data,
EPA “gained valuable insight into the conduct of the study.”
Id. at 9–10. EPA concluded that the SAP had rejected both
the approach in the 2015 Proposed Rule and the new method
based on the Columbia Study. Id. at 3. EPA agreed with the
SAP that, despite uncertainties in the studies, there was
“sufficient evidence that there are neurodevelopmental
effects occurring at chlorpyrifos exposure levels” below the
tolerances. Id. at 13. As a result, EPA proposed following
the 2016 SAP’s recommendation to use a hybrid point of
departure, rather than relying solely on the data from the
Columbia Study. Id. at 13–14.

   Within two weeks of issuing the 2016 RHHRA, EPA
reopened the comment period on the 2015 Proposed Rule.
Chlorpyrifos; Tolerance Revocations; Notice of Data
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Availability and Request for Comment, 81 Fed. Reg. 81,049
(Nov. 17, 2016) (2016 Request for Comments). EPA noted
that it was not proposing “a change to the EPA’s proposal to
revoke all tolerances but it does modify the methods and risk
assessment used to support that finding in accordance with
the advice of the SAP.” Id. at 81,050; see also id. (“[T]he
agency’s analysis provided in this notice continues to
indicate that the risk from the potential aggregate exposure
does not meet the FFDCA safety standard.”). At the same
time, EPA expressed frustration with the process, and
advised that “the timing of EPA’s issuance of the proposal
was dictated” by our order in PANNA II. Id. EPA was clear
that the basis for its proposed revocation depended on
studies that were incomplete. It observed that EPA had
completed a water assessment, but “[b]ecause of the court
decision . . . EPA was not able to complete a more refined
drinking water assessment for chlorpyrifos in advance of the
proposed rule” and that with additional time it conducted the
assessment to provide “a more tailored approach to risk
mitigation.” Id. at 81,051. EPA admitted that

       In the proposal, EPA proposed revoking all
       tolerances largely because the agency could
       not make a safety finding based on drinking
       water exposure in highly-vulnerable
       watersheds. EPA reasoned if it could better
       identify where such vulnerable areas might
       be, it could be possible for registrants to
       amend product labeling in ways that might
       make unnecessary some number of the
       proposed tolerance revocations.

Id. Importantly, EPA warned that its proposed course of
conduct was not fixed:
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         Since EPA is still in the process of
         deliberating the provisions of a final rule,
         EPA cannot definitively state whether this
         information will provide support for any
         provision of the final rule, or that the agency
         has determined that it is appropriate to rely on
         this information in developing the final rule.

Id.

      3. EPA denies the petition; we issue mandamus

    In April 2017, EPA reversed course, issuing a final
response to the 2007 petition, which denied it in full.
Chlorpyrifos; Order Denying PANNA and NRDC’s Petition
to Revoke Tolerances, 82 Fed. Reg. 16,581 (April 5, 2017)
(2017 Denial). The order stated:

         Following a review of comments on both the
         November 2015 proposal and the November
         2016 notice of data availability, EPA has
         concluded that, despite several years of
         study,      the      science      addressing
         neurodevelopmental       effects     remains
         unresolved and that further evaluation of the
         science during the remaining time for
         completion of registration review is
         warranted to achieve greater certainty as to
         whether the potential exists for adverse
         neurodevelopmental effects to occur from
         current human exposures to chlorpyrifos.
         EPA has therefore concluded that it will not
         complete the human health portion of the
         registration review or any associated
         tolerance revocation of chlorpyrifos without
100 LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

       first attempting to come to a clearer scientific
       resolution on those issues.

Id. at 16,583. EPA thus denied the petition without resolving
all scientific uncertainty concerning the tolerances
“[b]ecause the 9th Circuit’s August 12, 2016 order has made
clear, however, that further extensions to the March 31, 2017
deadline for responding to the Petition would not be
granted.” Id. (referring to PANNA IV, 840 F.3d at 1015).
EPA explained that the comments received in response to the
2015 Proposed Rule “suggest that there continue to be
considerable areas of uncertainty with regard to what the
epidemiology data show and deep disagreement over how
those data should be considered in EPA’s risk assessment.”
Id. at 16,590. It then explained why it was denying the
petition, rather than continuing its prior course:

       As the 9th Circuit has made clear . . . EPA
       must provide a final response to the Petition
       by March 31, 2017, regardless of whether the
       science remains unsettled and irrespective of
       whatever options may exist for a more
       complete resolution of these issues . . . .

       Although past EPA administrations had
       chosen to attempt to complete [FIFRA]
       review several years in advance of the
       statutory deadline (and respond to the
       Petition on the same time frame), it has
       turned out that it is not possible to fully
       address these issues early in the registration
       review period . . . . Accordingly, EPA is
       denying these Petition claims and intends to
       complete a full and appropriate review of the
       neurodevelopmental data before either
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       finalizing the [2015] proposed rule . . . or
       taking an alternative regulatory path.

Id. EPA concluded that “given the importance of this matter
and the fact that critical questions remain regarding the
significance of the data addressing neurodevelopmental
effects, EPA believes there is good reason to extend the
registration review of chlorpyrifos and therefore to deny the
Petition.” Id.

    Various organizations petitioned our court for review of
EPA’s order. On review of EPA’s 2017 Denial, the panel
ordered EPA to revoke the chlorpyrifos tolerances. League
of United Latin American Citizens v. Wheeler (LULAC I),
899 F.3d 814, 829 (9th Cir. 2018). Judge Fernandez
dissented on the grounds that the 2017 Denial was not a final
action. Id. at 830–32 (Fernandez, J., dissenting). We
granted en banc review, vacated the panel opinion, and
ordered EPA to issue a final order. League of United Latin
American Citizens v. Wheeler (LULAC II), 922 F.3d 443,
445 (9th Cir. 2019) (en banc). EPA issued its Final Order
in July 2019, and we referred the petition back to the three-
judge panel. League of United Latin American Citizens v.
Wheeler (LULAC III), 940 F.3d 1126, 1127 (9th Cir. 2019).

                             B

    EPA’s Final Order responded to the two objections
raised in LULAC I: (1) that the “EPA has unlawfully left
chlorpyrifos tolerances in place without making the safety
finding required by the FFDCA”; and (2) that EPA must
revoke the tolerances because it “has previously found that
chlorpyrifos tolerances are unsafe and has not disavowed
those findings.” Final Order, 84 Fed. Reg. at 35,561.
102 LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

   1. Failure to find that chlorpyrifos is “safe”

    EPA first addressed Petitioners’ argument that EPA was
required to make a new safety finding to deny the petition.
EPA found that it was not required to make a new safety
determination in response to every revocation petition, the
FFDCA did not require revocation in the absence of a new
safety determination for each petition, and even if a new
safety determination was required, both the FFDCA and
EPA implementing regulations “require petitioners seeking
withdrawal of a tolerance to support this request with valid,
complete and reliable data that set forth why the tolerances
are unsafe.” Id. at 35,562.

    The agency found that petitioners had not met their
burden of presenting evidence that the tolerances must be
revoked because “the information yet presented by
Petitioners is not sufficiently valid, complete, and reliable.”
Id. at 35,562–63. EPA had already considered, during its
2006 review, the laboratory and epidemiological studies
cited by Petitioners and had “consistently concluded” these
studies did not warrant revocation based on “an evaluation
across multiples lines of evidence.” Id. at 35,563. EPA
determined these studies were deficient because they lacked
a “mechanistic understanding for effects on the developing
brain,” which precluded EPA from having a “valid or
reliable way[] to bridge the scientific interpretation” of the
studies with chlorpyrifos; the dosing regimen of the in vivo
studies presented problems for “quantitative interpretation
and extrapolation of the results” because they did not align
with “internationally accepted protocols”; and EPA had been
unable to obtain the raw data underlying the epidemiological
studies, despite numerous efforts, to allow for verification of
validity and reliability as well as replication. Id. EPA
candidly acknowledged that its conclusion was “at odds”
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with its 2016 RHHRA but ultimately asserted that it had
“undertaken considerable efforts to assess the available
chlorpyrifos data.” Id. at 35,564; see also id. (“EPA
acknowledges this conclusion differs from the position
supported in the 2016 revised human health risk
assessment.”).      The agency concluded that “the
shortcomings of the data identified raise issues of validity,
completeness and reliability under the FFDCA that direct
against using the data for risk assessment at this time.” Id.

    EPA explained that a majority of the 2016 SAP had
concluded that use of the scientific studies under review for
developing points of departure “could not be justified by any
sound scientific evaluation.” Id. at 33,564. The SAP
“expressed significant reservations” about using the studies
as the sole source of revised points of departure and “noted
the incompleteness of the information,” including the
“reproducibility” of the data. Id. EPA concluded that
“[b]ased on the uncertainties identified by the 2016 SAP,”
the data were “not complete.” Id. EPA further laid out its
requests to obtain the raw data underlying the studies and
“visit[] [to] Columbia University in an attempt to better
understand their study results and what raw data exist.” Id.
at 33,565. Although the university initially had pledged to
share its data, it failed to produce it, citing “privacy
concerns.” Id. As a result, “EPA cannot validate or confirm
the data analysis performed, the degree to which the
statistical methods employed were appropriate, or the extent
to which (reasonable or minor) changes in assumptions may
have changed any final results or conclusions.” Id. As a
consequence, EPA concluded petitioners had “failed to meet
their initial burden of providing sufficiently valid, complete,
and reliable evidence that neurodevelopmental effects may
be occurring at levels below EPA’s current regulatory
standard.” Id.
104 LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

    EPA further concluded that denying the 2007 petition
was appropriate because the claims in the petition would be
subject to FIFRA registration review, which is a “more up-
to-date, thorough and methodical” review. Id. EPA
reiterated its commitment to complete FIFRA and FFDCA
review of chlorpyrifos tolerances in advance of the October
2022 deadline, anticipating some updates “by summer of
2020.” Id. at 35,566.

   2. EPA’s prior finding that chlorpyrifos is “not safe”

    EPA also addressed petitioners’ objection that the
agency had already found chlorpyrifos to be unsafe in its
2015 proposed tolerance revocation. Id. at 35,566. EPA,
however, was quite clear that “EPA has not made any
findings that chlorpyrifos tolerances are not safe.” Id. EPA
pointed out that its last final action regarding the safety of
chlorpyrifos tolerances—and the only regulatory finding in
effect—was its 2006 reregistration and safety determination.
Id. The 2015 Proposed Rule was not a final agency action,
and “EPA made clear it was issuing the proposal because of”
the Ninth Circuit’s order, “without having resolved many of
the issues critical to EPA’s FFDCA determination and
without having fully considered comments previously
submitted to the Agency.” Id. It was up to EPA to “choose
to finalize, modify or withdraw the proposal based on the
comments received.” Id. Accordingly, its prior proposed
findings were “not binding pronouncements.” Id.

                              C

    EPA’s decision to deny the petition in its entirety in
response to our writ of mandamus is entirely reasonable. We
ordered EPA to grant or deny the petitions; EPA did as we
ordered. It has explained why it did so and explained how it
will proceed with the chlorpyrifos reregistration, in which it
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will have to decide whether it is “safe.” There is nothing
arbitrary or capricious in EPA’s decision.

      Although petitioners can argue that the denial of the
petition conflicts with EPA’s prior proposal, the 2015
Proposed Rule is just that—a proposed rule. 2015 Proposed
Rule, 80 Fed. Reg. at 69,083 (“EPA may update this
[proposed rule] with new or modified analyses as EPA
completes additional work after this proposal.”). “Agencies
are entitled to change their minds.” Defenders of Wildlife v.
Zinke, 856 F.3d 1248, 1262 (9th Cir. 2017) (citation
omitted); see also Nat’l Ass’n of Home Builders v. Defenders
of Wildlife, 551 U.S. 644, 658–59 (2007) (“[T]he only
‘inconsistency’ respondents can point to is the fact that the
agencies changed their minds—something that, as long as
the proper procedures were followed, they were fully
entitled to do.”). “The federal courts ordinarily are
empowered to review only an agency’s final action, see
5 U.S.C. § 704, and the fact that a preliminary determination
. . . is later overruled . . . does not render the decisionmaking
process arbitrary and capricious.” Nat’l Ass’n of Home
Builders, 551 U.S. at 659. Agencies that change their mind
are not “subjected to more searching review.” FCC v. Fox
Television Stations, Inc., 556 U.S. 502, 514 (2009). What is
important is that the agency “display awareness that it is
changing position” and has explained itself. Id. at 515. EPA
did not act arbitrarily and capriciously merely because it
reversed course from its 2015 Proposed Rule—a reversal
that EPA explained.

    Nor was the 2016 RHHRA a final agency action. Human
Health Risk Assessments are part of FIFRA reregistration
review but are not in themselves safety determinations. 2016
RHHRA at 3. It is the final Reregistration Eligibility
Decision—which in this case was issued in 2006—that
106 LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

serves as the final EPA action for determining safety
pursuant to the FFDCA. 2006 Reregistration Decision at 1–
2. Although the 2016 RHHRA stated that the studies cited
by the petition provided “sufficient evidence that there are
neurodevelopmental effects occurring at chlorpyrifos
exposure levels below” current tolerances, this conclusion is
tentative until the agency adopts it as part of a final order or
rule. 2016 RHHRA at 13. The 2016 RHHRA remains part
of a broader review process that will culminate in another
Registration Eligibility Decision no later than 2022. In the
meantime, however, relying on its Scientific Advisory
Panel, EPA has explained why that study is flawed. The
methodology used in the 2015 Proposed Rule was rejected
by the SAP, and the 2016 RHHRA attempted to address the
SAP’s concerns by using a different approach. Id. at 3–4.

    As it is entitled to do, EPA has sufficiently explained its
rationale for reversing course from the 2015 Proposed Rule
and 2016 RHHRA and denying the petition. EPA was
required to “examine the relevant data and articulate a
satisfactory explanation for its action including a rational
connection between the facts found and the choice made.”
Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State Farm Mut.
Ins. Co., 463 U.S. 29, 43 (1983) (quotations marks and
citation omitted). EPA did articulate an explanation for its
departure from the 2015 Proposed Rule and the 2016
RHHRA in its 2017 Denial and Final Order. In its 2017
Denial of the petition, EPA explained that responses from
the 2016 SAP and comments received in response to the
2015 Proposed Rule raised “considerable areas of
uncertainty” regarding the studies. 2017 Denial, 82 Fed.
Reg. at 16,590. Based on this uncertainty, EPA concluded
that it should instead “explore approaches raised by the SAP
and commenters on the proposed rule, and possibly seek
additional authoritative peer review of EPA’s risk
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assessment prior to finalizing any regulatory action in the
course of registration review.” Id.

    EPA again explained the rationale for its departure from
the 2016 RHHRA in its Final Order. EPA explicitly
recognized its denial of the petition was “at odds with” the
2016 RHHRA, but it explained that it had “undertaken
considerable efforts to assess the available chlorpyrifos
data,” summarizing its longstanding concerns about the
studies relied on by petitioners. Final Order, 84 Fed. Reg.
at 35,564. EPA discussed its decision to convene the SAP
in 2016 to specifically consider the EPA’s proposal to use
information derived from the Columbia Study to develop a
point of departure—a meeting EPA noted “was unique in
focus compared to the previous meetings”—and the SAP’s
rejection of using that data alone as the basis for the new
point of departure. Id. EPA explained that the 2016 SAP’s
feedback on the proposal based on the Columbia Study data
was “consistent with concerns raised in public comments
EPA received on the use of the epidemiology data
throughout the course of registration review.” Id. EPA
further noted that, although the 2008 and 2012 SAPs
recognized strengths in the Columbia Study, neither
recommended changing points of departure based on the
study, and the 2016 SAP expressed even more reservation
about using the study in this way. Id. Thus, despite
preliminary assessments that recognized potential in the
Columbia Study data, EPA ultimately concluded that “the
shortcomings of the data identified raise issues of validity,
completeness and reliability under the FFDCA that direct
against using the data for risk assessment at this time.” Id.
EPA also noted that this was not its final conclusion
regarding the validity of the studies and that it “intends to
continue its exploration of the uncertainty” with regards to
the studies’ conclusions. Id. Because these studies—which
108 LEAGUE OF UNITED LATIN AM. CITIZENS V. REGAN

met the threshold requirements for consideration on the
merits—were not sufficiently valid, complete, and reliable
to support revocation, EPA decided not to modify or revoke
the chlorpyrifos tolerances.

     Nothing in EPA’s explanations is arbitrary or capricious.
It is clear that the agency has struggled with the scientific
studies before it. But nothing in either the procedure or the
substance of EPA’s actions—aside from playing Hamlet—
suggests that the agency has been irresponsible. To the
contrary, at every step of the way, EPA has conscientiously
examined the evidence. In 2015, it told petitioners it would
deny the petition outright. This was not surprising because
EPA had long advised the petitioners and other interested
persons of the flaws in the studies. It changed course later
that year when it was forced to make a decision in response
to our writ of mandamus. EPA then proposed revoking the
chlorpyrifos tolerances based on a novel measure of the
effect on infants and children—only to have the SAP
disapprove of the measure in 2016 and recommend further
study. EPA requested further comments on the science—
and an extension of time to make a decision. When we told
EPA that there would be no further extensions, EPA called
for additional comments and repeated that the studies were
inconclusive, but EPA continued to believe it had no choice
but to revoke the tolerances. But even as it called for last
comments, EPA advised that it was “still in the process of
deliberating the provisions of a final rule.” 2016 Request for
Comments, 81 Fed. Reg. at 81,051.

    So how do we assess this convoluted history? It is
certainly true that the agency had some stops and starts along
the way, but that is evidence of deliberate decisionmaking,
not dereliction of duty. We, of all institutions, should respect
that there will be give-and-take in complicated matters of
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consequence. The FFDCA does not demand unanimity
within EPA, any more than it requires unanimity from this
court before we may issue a judgment in this case.

      In my view, the majority has intervened in ongoing
debates within EPA over what the evidence proves and how
it should be weighed. It is not our place to second-guess
EPA’s scientific assessment of laboratory and
epidemiological studies supporting the petition. “Deference
to an agency’s technical expertise and experience is
particularly warranted with respect to questions involving
. . . scientific matters.” United States v. Alpine Land &
Reservoir Co., 887 F.2d 207, 213 (9th Cir. 1989). When an
agency makes determinations “within its area of special
expertise, at the frontiers of science . . . a reviewing court
must generally be at its most deferential.” Balt. Gas & Elec.
Co. v. NRDC, 462 U.S. 87, 103 (1983). The majority
improperly makes its own assessment of the reliability of the
studies and whether EPA’s concerns are sufficient to
determine that chlorpyrifos tolerances are “not safe.” Maj.
Op. 54–58, 60–63. But EPA’s assessment of the scientific
strength of the studies supporting the petition is precisely the
type of analysis that should be given deference. FFDCA
safety determinations are within EPA’s area of expertise.
We should not second-guess EPA’s scientific conclusions
with regards to the value of these studies. EPA’s denial of
the 2007 petition was neither arbitrary nor capricious.

                             ***

    The FFDCA does not require EPA to engage in a full-
blown FFDCA safety evaluation in response to every
petition filed with the agency. Instead, where a petition
presents reasonable grounds for revocation, EPA must
consider whether the petition puts forth data that supports a
determination that a pesticide tolerance is not safe. Where
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the data supporting a petition are not sufficiently valid,
reliable, or complete, EPA may deny the petition and rest on
its operative safety determination. Here, EPA complied with
its statutory obligation: the agency considered the petition on
the merits and determined that the data supporting the
petition was insufficient to support revocation. Based on this
determination, EPA denied the petition and relied on its 2006
finding that chlorpyrifos tolerances are safe. EPA explained
the deficiencies in the underlying petition’s supporting
studies and its rationale for departing from its prior
preliminary determinations. EPA did all that the FFDCA
required.

                                   III

      Even if I thought the majority had read the statute
correctly and had a clear-eyed view of the validity and
weight to be given to the scientific evidence, the remedy
ordered by the majority is an abuse of our discretion.
Assuming that petitioners have demonstrated that
chlorpyrifos is “not safe,” the FFDCA gives EPA the
discretion to decide whether to modify or to revoke the
tolerance. See 21 U.S.C. § 346a(b)(2)(A)(i); Maj. Op. at 60
(“[O]nce the EPA has determined that a tolerance is not safe,
. . . it must modify or revoke the tolerance.”). Concluding
that on this record “the present tolerances are not safe,” Maj.
Op. at 63, the majority orders EPA to “modify or revoke
chlorpyrifos tolerances and modify or cancel chlorpyrifos
registrations,” 9 Maj. Op. at 63, and gives EPA 60 days to do

     9
        In ordering the modification or cancellation of FIFRA
registrations, Maj. Op. at 67, the majority has exceeded the scope of what
a petition under the FFDCA allows: modification or cancellation of
chlorpyrifos tolerances under the FFDCA.                See 21 U.S.C.
§ 346a(d)(1)(A) (allowing petitions “proposing the issuance of a
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so, Maj. Op. at 67. It is more than a little ironic that this
court will have taken over a year since the filing of the last
brief to decide this case, but we will expect EPA to make an
informed decision in the next 60 days.

     The 60 days the majority gives EPA is not a number
drawn from the statutes, but one made up by the majority,
and it may well foreordain the option EPA must choose. In
my view, the stakes in this case are too high for the majority
to take upon itself to decide what the United States will do
with respect to chlorpyrifos. “By pounds of active
ingredient, [chlorpyrifos] is the most widely used
conventional insecticide in the country” and for some crops
it is “currently the only cost-effective choice for control of
certain insect pests.” Final Order, 84 Fed. Reg. at 35,558. 10
That, of course, is not an argument for finding chlorpyrifos
safe, as EPA recognized, but it should sharpen our focus on
what we are doing. See 2017 Denial, 82 Fed. Reg. at 16,590
(“Although not a legal consideration, it is important to
recognize that for many decades chlorpyrifos has been and
remains one of the most widely used pesticides in the United
States, making any decision to retain or remove this pesticide
from the market an extremely significant policy choice.”).
That is why EPA should be considering the options Congress

regulation establishing, modifying or revoking a tolerance” under that
statute (emphasis added)). Although modification of revocation of a
tolerance under the FFDCA will necessarily impact registrations under
FIFRA, the FFDCA does not afford this court authority to order
modification or cancellation under FIFRA.
    10
      Chlorpyrifos tolerances are classified by crop (e.g., alfalfa,
almonds, apples, corn, cotton, grapes, oranges, pears, soybeans, walnuts,
and wheat) and usage (e.g., cockroach and fire ant control, mosquito
abatement, utility pole treatments) and are region specific. The
complexity of the tolerances is difficult to overstate.
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made available, not us. And we have not given anything but
the most fleeting consideration to the options. 11

    It is far from clear that EPA will be able to do anything
in the next 60 days other than revoke the tolerances. Yet,
between argument and the issuing of this decision, EPA
advised us that it has issued an interim decision to reregister
chlorpyrifos, with modifications. Pesticide Registration
Review; Proposed Interim Decision for Chlorpyrifos; Notice
of Availability, 85 Fed. Reg. 78,849 (Dec. 7, 2020) (2020
Proposed Interim Decision) (inviting comments on EPA,
Chlorpyrifos: Proposed Interim Registration Review
Decision (Dec. 3, 2020) (2020 Proposed Interim
Registration)). In the 2020 Proposed Interim Registration,
EPA explained that it was proceeding with suggested
modifications, but that it still faced “numerous novel
scientific issues, notably the potential for neurodevelopment
effects on the young.” 2020 Proposed Interim Registration
Decision at 10. Candidly, EPA stated:

         Despite several years of study, the science
         addressing neurodevelopmental effects
         remains unresolved. . . . Notwithstanding,

    11
        The majority may have effectively foreclosed other options
Congress made available to EPA. Under the FFDCA, if a petitioner can
show that it not safe, EPA must modify or revoke the tolerance; or, in its
periodic statutory review, if EPA cannot determine chlorpyrifos is safe,
it cannot leave the tolerance in place. But if EPA arrives at that point,
there is yet an additional option: EPA has the power to leave in effect or
modify a tolerance if it concludes that certain consequences will
follow—if “the residue protects consumers from adverse effects on
health that would pose a greater risk than the dietary risk” or if the
tolerance “is necessary to avoid a significant disruption in domestic
production of an adequate, wholesome, and economical food supply.”
21 U.S.C. § 346a(b)(2)(B)(iii). These contingencies would still require
EPA to certify that the tolerances modified or left in effect satisfy the
“no harm” to infants and children criteria in 21 U.S.C. § 346a(b)(2)(C).
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       EPA recognizes that the science is evolving
       on this topic, and that there may be new
       information available prior to the completion
       of registration review that may impact the
       agency’s conclusions about these effects.

Id. It further advised that it had convened a SAP in
September 2020 “to assess new approval methodologies that
might used to evaluate developmental neurotoxicity in
EPA’s assessment of risks to human health.” Id.; see also
id. at 40, 63. The SAP’s report was issued a week later in
December 2020. EPA, FIFRA Scientific Advisory Panel
Meeting Minutes and Final Report No. 2020-02: Peer
Review of the Use of New Approach Methodologies (NAMs)
to Derive Extrapolation Factors and Evaluate
Developmental Neurotoxicity for Human Health Risk
Assessment (Sept. 15–18, 2020) (report released Dec. 15,
2020). For the reasons I have explained, in this latest
proceeding, the risk of nonpersuasion runs against the
existing tolerances. That means that EPA will have to decide
the issues reserved in its interim proceedings—and,
specifically, the question of safe tolerances for children and
youth—and it must do so by 2022, the deadline set by
Congress.

    What effect the majority’s order will have on EPA’s
latest proceeding is unclear, but the majority’s order presents
it with two unsatisfactory choices: either issue modified
tolerances outside the procedure required by the FFDCA,
FIFRA, and APA, or revoke the tolerances. Given the 2020
Proposed Interim Registration Decision, maybe EPA will be
comfortable issuing modified tolerances, but in order to do
so it will have to accelerate its schedule, and that may mean
skipping some steps.          See 2020 Proposed Interim
Registration Decision at 4, 8–9 (explaining that EPA is
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awaiting revised biological opinions from the National
Marine Fisheries Service and the U.S. Fish & Wildlife
Service). Alternatively, EPA may be forced to revoke
tolerances that it has tentatively concluded it will reregister
or reregister with modifications. Perhaps EPA will again
approve registration of chlorpyrifos at some future date once
it completes full FIFRA and FFDCA review, but our
precipitous order will have imposed tremendous costs on
various sectors of the economy without waiting for the
system to work.

    Finally, I have to comment on the artificial schedule that
our court has imposed on EPA, not only in this case, but time
and again in these proceedings. EPA took the 2007 petition
to revoke chlorpyrifos very seriously. Unlike reregistration
under FIFRA, there is no statutory deadline for dealing with
a petition, although in principle twelve years seems like
more than enough time. The extraordinary delay, however,
makes more sense in context: EPA initially believed that it
could accelerate the FIFRA reregistration due in 2022 and
address both the petition and the reregistration at the same
time and well before that date. In the meantime, the
petitioners asked us to intervene and order EPA to rule on its
petition. EPA repeatedly advised us that it could not meet
those demands if it was to complete the reregistration
process properly. We insisted. Eventually, but reluctantly,
EPA proposed to revoke the tolerances—even as it stated
that it was doing so without complete information. See, e.g.,
2016 Request for Comments, 81 Fed. Reg. at 81,050; 2015
Proposed Rule, 80 Fed. Reg. at 69,080. After further
proceedings, EPA concluded that it was better to deny the
petitions outright because the petitioners had failed to show
that the tolerances were not safe, and then complete the
FIFRA reregistration process, where it would have a full
record. EPA’s decision is consistent with the FFDCA, as
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amended by the FQPA. Although in hindsight the process
took much longer than EPA anticipated, that was a
reasonable decision on EPA’s part at the time.

    When we intervene in scientific inquiries with
impatience and impose artificial deadlines, we bear some
responsibility for the confusion that results. In San Luis &
Delta-Mendota Water Authority v. Jewell, 747 F.3d 581 (9th
Cir. 2014), the district court ordered the U.S. Fish & Wildlife
Service to produce a complex, 400-page biological opinion
in less than a year. The resulting biological opinion was

       a jumble of disjointed facts and analyses. It
       appears to be the result of exactly what we
       would imagine happens when an agency is
       ordered to produce an important opinion on
       an extremely complicated and technical
       subject matter covering multiple federal and
       state agencies and affecting millions of acres
       of land and tens of millions of people.

Id. at 605; see also id. at 605 n.15 (noting that “the FWS had
less time to produce its opinion than either the district court
or we will have had to review it”). We “wonder[ed] whether
anyone was ultimately well-served by the imposition of tight
deadlines in a matter of such consequence.” Id. at 606.
When we interject ourselves into technical proceedings, our
“[d]eadlines become a substantive constraint on what an
agency can reasonably do. . . . Such scientific tasks may not
be as well suited to deadlines as producing written copy; the
final product will necessarily reflect the time allotted to the
agency.” Id. We can only hope that “[f]uture analyses [will]
be given the time and attention that these serious issues
deserve.” Id.
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    In any event, our order is an abuse of any discretion the
APA confers on us. We have the power to “compel agency
action . . . unreasonably delayed,” 5 U.S.C. § 706(1), but we
do not have the power to choose among the options available
to EPA. Our deadline may effectively make the choice for
EPA.

                              IV

    There are manifest errors in the majority opinion. It has
misread the FFDCA and misallocated the risk of
nonpersuasion. It has overruled EPA’s judgment on the
validity and weight to be given technical evidence within
EPA’s expertise. And by its decision to give EPA 60 days
to issue a final decision in this case, the majority has likely
predetermined EPA’s option. I respectfully, but firmly,
dissent.