Amicus Curiae Brief — Monsanto Company, Petitioner v. John L. Durnell

Supreme Court briefApr 1, 2026

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No. 24-1068

IN THE

Supreme Court of the United States

MONSANTO COMPANY,

Petitioners,

JOHN L. DURNELL,

Respondent.

On Writ of Certiorari to

the United States Court of Appeals

for Missouri, Eastern District

BRIEF OF FARMWORKER JUSTICE,

FARMWORKER ASSOCIATION OF FLORIDA,

CALIFORNIA RURAL LEGAL ASSISTANCE

FOUNDATION, MIGRANT CLINICIANS

NETWORK, ALIANZA NACIONAL DE

CAMPESINAS, AND PESTICIDE ACTION &

AGROECOLOGY NETWORK AS AMICI CURIAE IN

SUPPORT OF RESPONDENT

GREGORY C. LOARIE

EARTHJUSTICE

1 Sansome Street

Suite 1700

San Francisco, CA 94104

PATTI GOLDMAN

Counsel of Record

NOORULANNE JAN

EARTHJUSTICE

810 3rd Avenue

Suite 610

Seattle, WA 98104

(206) 578-5868

pgoldman@earthjustice.org

Counsel for Amici Curiae

TABLE OF CONTENTS

Page

TABLE OF AUTHORITIES...................................... iii

INTEREST OF AMICI CURIAE ................................1

INTRODUCTION AND SUMMARY OF

ARGUMENT ...............................................................2

ARGUMENT ...............................................................6

FIFRA Establishes An Iterative Scheme That

Requires Manufacturers To Update Pesticide

Labels To Provide Adequate Warnings And

Directions To Protect Health. ...............................6

A. Manufacturers Have An Ongoing Duty To

Ensure Their Labels Are Adequate To Protect

Public Health. ..................................................7

B. Manufacturers Have A Duty To Submit

Adverse Effects Information, Including

Information Derived From Tort Litigation. . 10

II. States Have Authority To Determine Whether

EPA-Accepted Labels Are Adequate To Protect

Health And To Afford Greater Protection.......... 12

III. FIFRA Allows EPA To Authorize Pesticide Use

In Situations Where It Lacks Complete

Information To Find The Label Adequate To

Protect Health. .................................................... 17

IV. EPA Has Adopted Regulatory Schemes That Fail

To Require Comprehensive Cancer Testing Or

Warnings. ............................................................ 21

A. EPA’s Regulations Require Cancer Testing Of

A Pesticide’s Active Ingredient, But Not Of

The Formulated Pesticide Product. .............. 21

B. EPA’s Regulations Require Label Warnings

For Acute Toxicity, But Not For Cancer. ...... 24

V. EPA Has Yet To Ensure That Pesticide

Registrations And Labels Protect Against

Serious Toxic Effects And Exposures That

Congress Requires EPA To Address. ................. 26

A. EPA Lacks Sufficient Information To Ensure

That Labels Protect Against Serious

Noncancer Health Effects. ............................ 27

B. EPA Has Failed To Ensure That Pesticide

Labels Protect Children From Pesticide

Drift. ............................................................... 28

CONCLUSION .......................................................... 31

iii

TABLE OF AUTHORITIES

Cases

Page(s)

Bates v. Dow Agrosciences LLC,

544 U.S. 431 (2005) ...................... 4, 8, 9, 14, 15, 21

Chapman v. Monsanto Co.,

2022 WL 3971287 (S.D. Tex. 2022) ............... 11, 12

Ctr. for Env’t Health v. McCarthy,

192 F. Supp. 3d 1036 (N.D. Cal. 2016) ................ 23

Nat’l Coal. Against the Misuse of Pesticides v. EPA,

867 F.2d 636 (D.C. Cir. 1989) .............................. 20

Natural Resources Def. Council v. EPA,

38 F.4th 34 (9th Cir. 2022) .................................. 19

Ruckelshaus v. Monsanto Co.,

467 U.S. 986 (1984) .............................................. 22

Ruiz-Guzman v. Amvac Chemical Corp.,

7 P.3d 795 (Wash. 2000) ...................................... 15

Statutes and Regulations

Federal Insecticide, Fungicide, and Rodenticide Act

7 U.S.C. § 136(a) ........................................................ 22

7 U.S.C. § 136(m)....................................................... 22

7 U.S.C. § 136(n)(1) ................................................... 23

TABLE OF AUTHORITIES—Continued

Page(s)

7 U.S.C. § 136(q)(1)(F) .................................................3

7 U.S.C. § 136(q)(1)(G) ................................................3

7 U.S.C. § 136(q)(2)(A) .............................................. 23

7 U.S.C. § 136(q)(2)(D) .............................................. 25

7 U.S.C. §136(u)......................................................... 22

7 U.S.C. § 136(bb) .................................................. 6, 12

7 U.S.C. § 136(bb)(2) ................................................. 12

7 U.S.C. § 136a(a) ........................................................6

7 U.S.C. § 136a(c)(1)(C) ...............................................6

7 U.S.C. § 136a(c)(2) ....................................................6

7 U.S.C. § 136a(c)(2)(A) ............................................. 22

7 U.S.C. § 136a(c)(3)(B)(i)(II) ......................................9

7 U.S.C. § 136a(c)(5)(B) ....................................... 2, 4, 6

7 U.S.C. § 136a(c)(5)(D) ...............................................6

7 U.S.C. § 136a(c)(7)(A) ............................................. 17

7 U.S.C. § 136a(c)(7)(B) ............................................. 17

7 U.S.C. § 136a(c)(7)(C) ............................................. 17

TABLE OF AUTHORITIES—Continued

Page(s)

7 U.S.C. § 136a(d)(1)(C) ............................................ 24

7 U.S.C. § 136a(d)(1)(C)(i) ......................................... 24

7 U.S.C. § 136a(d)(1)(C)(ii) ........................................ 24

7 U.S.C. § 136a(f)(1) ............................................ 3, 7, 8

7 U.S.C. § 136a(f)(2) ............................................ 3, 7, 8

7 U.S.C. § 136a(g) ...................................................... 18

7 U.S.C. § 136a(g)(1)(A)(ii) ........................................ 18

7 U.S.C. § 136a-1 ....................................................... 18

7 U.S.C. § 136d(a)(1) ................................................. 20

7 U.S.C. § 136d(a)(2) ................................... 3, 7, 10, 11

7 U.S.C. § 136j(a)(1)(E) ....................................... 3, 7, 8

7 U.S.C. § 136j(a)(1)(F)............................................ 7, 8

7 U.S.C. § 136j(a)(2)(G) ...............................................9

7 U.S.C. § 136n(b)...................................................... 19

7 U.S.C. § 136p .......................................................... 17

7 U.S.C. § 136v(a) .................................................. 3, 12

7 U.S.C. § 136v(b) ...................................................... 15

TABLE OF AUTHORITIES—Continued

Page(s)

7 U.S.C. § 136w-1 ...................................................... 14

Federal Food, Drug, and Cosmetic Act

21 U.S.C. § 346a(b)(2)(A)(i) ....................................... 12

21 U.S.C. § 346a(b)(2)(A)(ii) ................................ 12, 29

21 U.S.C. § 346a(b)(2)(C) .......................................... 18

21 U.S.C. § 346a(b)(2)(D) .......................................... 18

21 U.S.C. § 346a(b)(2)(C)(ii)(I) ............................ 12, 29

21 U.S.C. § 346a(p) .................................................... 27

21 U.S.C. § 346a(p)(6) ............................................... 27

Legislation

Federal Insecticide, Fungicide, and Rodenticide Act

Amendments,

Pub. L. No. 35-396, 92 Stat. 819 (1978) .............. 18

Fiscal Year 2023 Consolidated Appropriations Act,

Pub. L. No. 117-328,136 Stat. 4459 (2022) ......... 19

H.R. 7567 § 10204(a)(2), 119th Cong. (2026) ........... 19

EPA Regulations

Registration Standards and Registration Review

40 C.F.R. § 155.40(a) ................................................. 18

vii

TABLE OF AUTHORITIES—Continued

Page(s)

40 C.F.R. § 155.53(a) ................................................. 18

40 C.F.R. § 155.56 ..................................................... 18

40 C.F.R. § 155.58(b)(3) ............................................. 19

Labeling Requirements for Pesticides and Devices

40 C.F.R. § 156.62 ..................................................... 24

40 C.F.R. § 156.64 ..................................................... 25

40 C.F.R. § 156.70 ..................................................... 25

Data Requirements for Pesticides

40 C.F.R. § 158.500(c) ............................................... 22

40 C.F.R. § 158.500(d) ............................................... 22

Reporting Requirements for Risk/Benefit Information

Interpretations

40 C.F.R. § 159.153(b) ............................................... 10

40 C.F.R. § 159.158(a) ............................................... 10

Exemption of Federal and State Agencies for Use of

Pesticides Under Emergency Conditions

40 C.F.R. § 166.25(b) ................................................. 17

40 C.F.R. § 166.25(b)(2)(ii) ........................................ 17

viii

TABLE OF AUTHORITIES—Continued

Page(s)

Agricultural Worker Protection Standard

Pesticides; Agricultural Worker Protection Standard

Revisions, 80 Fed. Reg. 67496 (Nov. 2, 2015)… 1, 2

Federal Register

Chlorpyrifos; Cancellation Order, 65 Fed. Reg. 76233

(Dec. 6, 2000) .................................................. 11, 20

Dacthal; Notice of Receipt of Requests to Voluntarily

Cancel Pesticide Registrations, 89 Fed. Reg.

70181 (Aug. 29, 2024) .......................................... 28

Endocrine Disruptor Screening Program, 63 Fed.

Reg. 42852 (Aug. 11, 1998) .................................. 27

Mevinphos; Amendment to Cancellation Order and

FIFRA Section 6(g) Notification, 60 Fed. Reg.

17357 (Apr. 5, 1995) ....................................... 15, 20

Pesticides; Consideration of Volatilization in

Pesticide Risk Assessment: Notice of Availability

and Request for Comment, 79 Fed. Reg. 16791

(Mar. 26, 2012) ..................................................... 29

Pesticides; Emergency Order Suspending the

Registrations of All Pesticide Products Containing

Dacthal, 89 Fed. Reg. 64445 (Aug. 7, 2024) ........ 28

State Rules and Regulations

Cal. Code Regs. Tit. 3, § 6691 ................................... 14

TABLE OF AUTHORITIES—Continued

Page(s)

Cal. Code Regs. Tit. 27, § 25603 ............................... 25

N.Y. Comp. Codes R. & Regs. Tit. 6, § 326.2(c)(17)

(2021) .................................................................... 13

Or. Admin. R. 603-057-0545(2)(b) (2026) .................14

Or. Admin. R. 603-057-0545(2)(c) (2026) .................. 14

Wash. State Dep't of Agric., Rule-Making Order To

Restrict The Use Of Mevinphos (Apr. 15, 1994),

https://perma.cc/RA9V-SFZ8 ............................... 15

Other Authorities

Cal. Dep’t of Pesticide Reg., Agreement Reached to

End Sale of Chlorpyrifos by February 2020 (Oct.

9, 2019), https://perma.cc/GE9Z-DU6D............... 16

Carol Browner, Dursban Announcement (June 8,

2000), https://perma.cc/H4ES-G5CP ...................11

EPA, Agency Response to “Pesticides in the Air Kids at Risk: Petition to EPA to Protect Children

from Pesticide Drift (2009)” (Apr. 2, 2014) (EPAHQ-OPP-2009-0825-0084) ................................... 29

EPA, Agreement Reached Between EPA and

Chlorpyrifos Pesticide Registrants (June 6, 1997),

https://perma.cc/4SV2-UYA7 ............................... 11

EPA, Assessing Human Health Risk from Pesticides

(Jan. 23, 2026), https://perma.cc/M59T-46CR ....13

TABLE OF AUTHORITIES—Continued

Page(s)

EPA, Chlorpyrifos: Revised Human Health Risk

Assessment for Registration Review (Dec. 29,

2014) (EPA-HQ-OPP-2008-0850-0195) ............... 16

EPA, DRAFT Proposed PR Notice 2025-NEW

(Revised PRN 98-10) (2026) (EPA-HQ-OPP-20252863-0002) ............................................................ 14

EPA, Endocrine Disruptor Screening Program Tier 1

Screening Determinations and Associated Data

Evaluation Records (Sept. 23, 2015),

https://perma.cc/X2QW-XDW4 ............................27

EPA, EPA Fines DowElanco For Failure to Report

Pesticide Health Effects (May 2, 1995),

https://perma.cc/D7C9-6F66 ................................ 10

EPA, Ethylene Oxide Interim Registration Review

Decision (Jan. 2025) (EPA-HQ-OPP-2013-02440435) ..................................................................... 23

EPA, Implementing Chemical Specific Human

Health Spray Drift Analysis for Pesticide

Registration Actions (July 2024) (EPA-HQ-OPP2013-0676-0124) ................................................... 29

EPA, Interim Reregistration Eligibility Decision for

Chlorpyrifos (2002) (EPA-738-R-01-007) ...... 11, 14

EPA, Label Review Manual (Dec. 2024),

https://perma.cc/SY84-X8NY ........................... 9, 26

TABLE OF AUTHORITIES—Continued

Page(s)

EPA, Memorandum Reviewing Chlorpyrifos

Poisoning Data (Jan. 14, 1997),

https://perma.cc/H7JA-NC9V .............................. 11

EPA, Paraquat Dichloride Interim Registration

Review Decision (July 2021) (EPA-HQ-OPP-20110855-0307) ............................................................ 13

EPA, Pesticide Labeling Questions & Answers (last

updated May 25, 2025), https://perma.cc/GE9ZDU6D .................................................................... 14

EPA, Registration Review Process (Oct. 30, 2025),

https://perma.cc/Q7WE-LDN9 ............................. 13

EPA, Upcoming Registration Review Actions (Aug.

26, 2025), https://perma.cc/W9EJ-2XWC ............ 19

EPA Office of Inspector General, EPA’s Endocrine

Disruptor Screening Program Has Made Limited

Progress in Assessing Pesticides (2021) (21-E0186), https://perma.cc/DT76-JHSN ................... 27

GAO, Pesticides: EPA Should Take Steps to Improve

Its Oversight of Conditional Registrations (2013)

(GAO-13-145) ....................................................... 17

Jim Morris, The Stuff in the Backyard Shed – The

Pesticide Is Effective And Sells Like Mad. But Is It

Safe For Everyone?, U.S. News & World Report,

Nov. 8, 1999, https://perma.cc/9E9N-QRPW ...... 10

xii

TABLE OF AUTHORITIES—Continued

Page(s)

Label for ACE-jet, EPA Reg. No. 74578-2 (Jan. 25,

2022), https://perma.cc/V6ZC-BRDX ................... 15

Label for Kerb 3.3 SC, EPA Reg. No. 62719-578

(Sept. 18, 2020), https://perma.cc/5G9R-T7Z5 .... 25

Label for Willowood Pronamide 3.3SC, EPA Reg. No.

87290-22 (Sept. 18, 2020), https://perma.cc/RKV4FNQE.................................................................... 25

INTEREST OF AMICUS CURIAE

Amici

Farmworker

Justice,

Farmworker

Association of Florida, California Rural Legal

Assistance Foundation, Migrant Clinicians Network,

Alianza Nacional de Campesinas, and Pesticide

Action & Agroecology Network are nonprofit

organizations that represent, serve, and partner with

hundreds of thousands of farmworkers across the

country to minimize workers’ exposures to dangerous

pesticides. 1

As the individuals directly handling pesticides and

crops sprayed with pesticides, farmworkers are

exposed to pesticides more frequently and in greater

concentrations than any other population. The

Environmental Protection Agency (EPA) has

recognized that “there is strong evidence that

[farm]workers and [pesticide] handlers may be

exposed to pesticides at levels that can cause adverse

effects,” including exposures that cause significant

long-term health risks. Pesticides; Agricultural

Worker Protection Standard Revisions, 80 Fed. Reg.

67496, 67498 (Nov. 2, 2015). Indeed, EPA estimates

that about 10,000 to 20,000 physician-diagnosed

poisonings occur annually at farms, nurseries, and

greenhouses across the country. Id. at 67502.

Farmworkers and their family members may also be

exposed when pesticide dust or droplets move through

No counsel for a party authored this brief in whole or in

part, and no such counsel, party, or any other person or entity—

other than amici curiae and their counsel—made a monetary

contribution intended to fund the preparation or submission of

this brief.

(1)

the air to where they live or go to school. See id.

Farmworkers depend on the EPA pesticideregistration process to ensure that pesticide labels

provide adequate warnings and directions to help

minimize harm from exposure. Labels can, for

example, prohibit particularly hazardous spraying

methods or mandate protective clothing, respirators,

or longer periods of time before farmworkers can reenter fields after pesticide spraying. See 80 Fed. Reg.

at 67502. The registration process produces adequate

label directions only if EPA has up-to-date and

complete information about the dangers from the

pesticide’s use.

State failure to warn litigation plays a critical role

in uncovering information that manufacturers have

not submitted to EPA or that demonstrates the need

for stronger label warnings or directions. Such

litigation has spurred manufacturers to modify their

pesticide labels to afford workers and their families

greater protection from pesticides. Such litigation also

provides an avenue for workers to obtain damages to

cover their medical expenses and lost wages when

they are injured because the manufacturer’s label

lacks adequate warnings or directions for use to

minimize harm.

INTRODUCTION AND

SUMMARY OF ARGUMENT

Under the Federal Insecticide, Fungicide, and

Rodenticide Act (FIFRA), EPA registers pesticides

upon determining, among other things, that the

pesticide label submitted by the manufacturer

complies with FIFRA. 7 U.S.C. § 136a(c)(5)(B). But

EPA makes this determination based on the

information on hand at that moment in time. Often

EPA lacks sufficient information to assess many ways

the pesticide can harm human health. Gaps in the

scientific evidence are filled over time and lead

manufacturers to change the pesticide label.

Under FIFRA, the label is not cast in stone.

Instead, FIFRA establishes an ongoing, iterative

scheme that obligates manufacturers to provide EPA

with the most up-to-date information about a

pesticide’s adverse effects, such as its potential to

cause cancer. 7 U.S.C. § 136d(a)(2). FIFRA likewise

obligates manufacturers to revise pesticide labels to

ensure that they avoid misbranding by providing

adequate warnings and directions for use to protect

health. See id. §§ 136(q)(1)(F)-(G), 136j(a)(1)(E). The

fact that EPA has registered the pesticide and

accepted the manufacturer’s label is not a defense for

violating FIFRA’s misbranding prohibition. Id.

§ 136a(f)(2). And EPA must amend pesticide

registrations to reflect label changes made by the

manufacturer unless the label change would violate

FIFRA. Id. § 136a(f)(1). State failure to warn claims

impose equivalent obligations and often uncover

adverse effects information that leads manufacturers

to change their labels to afford adequate health

protection.

FIFRA expressly preserves state authority to

regulate pesticide use to afford greater protection

than EPA. 7 U.S.C. § 136v(a). While EPA approves

labels based on FIFRA’s unreasonable adverse effects

determination—which balances health risks against

the pesticide’s benefits—a state may impose

additional limitations on pesticide use under a more

health-protective standard. Manufacturers can in

turn amend their labels to incorporate state use

regulations, reinforcing the continuous, adaptive

nature of pesticide labels. State failure to warn claims

generate additional information that can ensure the

EPA-accepted label has adequate directions to protect

health and avoid violating FIFRA’s misbranding

prohibition.

Although FIFRA charges EPA with determining

whether the manufacturer’s label complies with

FIFRA’s requirements when registering a pesticide, 7

U.S.C. § 136a(c)(5)(B), EPA reviews the label at a

point in time when the agency often lacks complete

information about all the ways the pesticide harms

people’s health. Based on this Court’s decision in

Bates v. Dow Agrosciences LLC, 544 U.S. 431, 450

(2005), the United States concedes that “a pesticide

might be misbranded for reasons outside the scope of

what EPA assesses during the registration process.”

U.S. Br. 27. Under FIFRA and EPA’s implementing

regulations, there often are substantial gaps in the

scientific evidence and in what EPA assesses.

FIFRA directs EPA to establish the minimum

toxicity data needed for a fully informed unreasonable

adverse effects determination, but FIFRA authorizes

EPA to allow some pesticide uses without all the

required data. FIFRA also allows EPA to complete

iterative reviews of pesticide registrations without

sufficient studies to assess the pesticide’s propensity

to cause serious toxic effects. EPA cannot assess such

effects until the manufacturer submits the missing

studies for the next round of iterative reviews. EPA

can also allow voluntarily canceled pesticides to be

used with outdated labels that fail to afford adequate

health protection.

In addition, EPA’s regulations leave significant

gaps in the cancer studies before the agency and

cancer warnings. In specifying the data required for

registration as FIFRA requires, EPA has required

cancer testing of the pesticide’s active ingredient but

not the whole pesticide product. Moreover, although

EPA has promulgated regulations elucidating

FIFRA’s requirements for classifying pesticides

according to their acute toxicity—and providing

corresponding warnings—FIFRA establishes no

comparable requirements for chronic risks like

cancer. EPA therefore does not require tests to

address the cancer-causing potential of the pesticide

product, and it does not scrutinize labels for the

existence or adequacy of cancer warnings.

EPA similarly has insufficient information to

assess certain noncancer toxic effects that Congress

directed it to address. For instance, EPA has

established a statutorily mandated program for

testing pesticides for dangerous endocrine disruption

effects, yet the agency has still not obtained the

required tests. The agency is only beginning to assess

the health risks to children from exposure to pesticide

dust and vapors that move away from the fields to

schools, homes, and playgrounds. EPA has, therefore,

made

registration

decisions

and

accepted

manufacturer labels without assessing potentially

serious toxic effects and exposures that Congress

directed it to address.

Because EPA has accepted the manufacturer’s

label based on its assessment of only some harms to

human health, pesticide labels often lack adequate

warnings or directions for use. State failure to warn

claims address this gap by uncovering scientific

studies and adverse effects information that was not

before EPA when it accepted the manufacturer’s label.

Such claims also create incentives for manufacturers

to comply with their statutory obligation to ensure

that their labels contain adequate warnings and

directions to protect health. And failure to warn

claims can provide compensation to people who suffer

harm to their health because label warnings were

inadequate.

ARGUMENT

FIFRA Establishes An Iterative Scheme

That Requires Manufacturers To Update

Pesticide Labels To Provide Adequate

Warnings And Directions To Protect

Health.

Congress amended FIFRA in 1972 to require

pesticide manufacturers to obtain an EPA

registration for a pesticide to be sold in the United

States. See 7 U.S.C. § 136a(a). To obtain a

registration, the manufacturer must submit the

complete pesticide labeling and laboratory studies

required by EPA regulations. Id. §§ 136a(c)(1)(C),

136a(c)(2). EPA must in turn find that the label

complies with FIFRA’s requirements and that use of

the pesticide “in accordance with widespread and

commonly recognized practice” will not generally

cause “unreasonable adverse effects on the

environment.” Id. § 136a(c)(5)(B), (D). That standard

is defined as “any unreasonable risk to man or the

environment, taking into account the economic, social,

and environmental costs and benefits” of the pesticide

use. Id. § 136(bb).

Once a pesticide is registered, however, the label is

not static. Manufacturers have an ongoing duty to

update their labels to ensure they contain adequate

instructions to protect health and to keep EPA

apprised of any information regarding the pesticide’s

potential to cause adverse effects. For its part, EPA

must amend registrations to reflect label changes

made by the manufacturer as long as the changes do

not violate FIFRA’s provisions. 7 U.S.C. § 136a(f)(1).

Accordingly, by FIFRA’s design, the most recent label

accepted by EPA is not set in stone. It must evolve to

be sufficient to protect public health.

A. Manufacturers Have An Ongoing Duty

To Ensure Their Labels Are Adequate

To Protect Public Health.

Pesticide manufacturers have an ongoing duty to

ensure that their labels will protect the public.

Manufacturers must continually ensure that their

labels avoid misbranding, see 7 U.S.C. § 136j(a)(1)(E)(F), and registration is no defense, id. § 136a(f)(2). And

they must provide EPA emerging science and other

information about the pesticide’s adverse effects. Id. §

136d(a)(2).

1. EPA’s Past Approval Of A Pesticide

Label Is No Defense To A Misbranding Violation.

The fact that EPA has registered a pesticide is

“prima facie evidence” of compliance with FIFRA’s

registration requirements. 7 U.S.C. § 136a(f)(2). But

it is not “a defense for the commission of any offense”

under FIFRA. Id.

On its face, FIFRA’s no-defense provision extends

to “any offense” under FIFRA, which includes

distributing any pesticide that is misbranded. 7

U.S.C. § 136j(a)(1)(E)-(F). As this Court recognized

over twenty years ago, the no-defense provision

requires manufacturers to come forward with

proposed label changes: “Because it is unlawful under

the statute to sell a pesticide that is registered but

nevertheless misbranded, manufacturers have a

continuing obligation to adhere to FIFRA’s labeling

requirements.” Bates, 544 U.S. at 438 (citation

omitted).

2. FIFRA Allows Manufacturers To

Amend Their Labels To Provide

Greater Protection.

Under FIFRA, it is the manufacturer’s prerogative

to change its pesticide label. FIFRA mandates that, if

a manufacturer changes a pesticide label, “the

registration shall be amended to reflect such change

if the Administrator determines that the change will

not violate any provision of this subchapter.” 7 U.S.C.

§ 136a(f)(1) (emphasis added). EPA would have no

basis for preventing the manufacturer from providing

stronger or more detailed health warnings since

EPA’s past registration of the pesticide is “no defense”

to a violation of FIFRA’s misbranding requirement to

ensure the label provides adequate health warnings.

It is commonplace for manufacturers to modify

their labels to add directions for use to guard against

health or environmental harm. Indeed, in Bates, Dow

Agrosciences submitted and EPA quickly accepted a

modified label, advising against applying the pesticide

to certain soils in states where peanut farmers had

experienced crop damage. See 544 U.S. at 435.

EPA’s process of reviewing labels is not onerous.

EPA stamps the manufacturer label “accepted”

without making written findings. See EPA, Label

Review

Manual

(Dec.

2024),

https://perma.cc/SY84-X8NY

(Label

Review

Manual). 2 And FIFRA directs EPA to act “as

expeditiously as possible” on an application for a

registration amendment that does not require review

of scientific data, 7 U.S.C. § 136a(c)(3)(B)(i)(II)—

which is often the case with label changes refining the

directions for use or adding cancer warnings.

Monsanto raises the specter of EPA preventing it

from adding a cancer warning to the Roundup label.

But Monsanto never identifies a single instance where

EPA has prevented the addition of a cancer warning.

Nor has it pointed to a particular provision of FIFRA

that would allow EPA to block addition of a cancer

warning or further label directions to reduce exposure

to a pesticide that has the potential to cause cancer. 3

page.

Due to irregular pagination, this brief cites to the PDF

In characterizing pesticide labels as somehow inviolate

and impossible to change, Monsanto repeatedly quotes a

statement in EPA’s Pesticide Registration Manual that “[t]he

label is the law.” Pet. Br. 8, 26, 45. That phrase, however, reflects

the fact that it is a violation of FIFRA to use a pesticide in a

manner inconsistent with its label. See 7 U.S.C. § 136j(a)(2)(G);

see also Label Review Manual at 11 (“label is the law” refers to

FIFRA’s provision making violations of label requirements

B. Manufacturers Have A Duty To Submit

Adverse Effects Information, Including

Information

Derived

From

Tort

Litigation.

Manufacturers have an ongoing obligation to

provide EPA with all information in their possession

regarding a pesticide’s adverse effects on health and

the environment. See 7 U.S.C. § 136d(a)(2). This

mandate extends to information generated or

obtained in tort litigation, including discovery and

expert reports. See 40 C.F.R. § 159.158(a); id.

§ 159.153(b) (defining “Qualified expert”).

The evidence amassed in tort litigation can show

how people are being harmed by a pesticide and how

labels must be changed to prevent or lessen the harm.

Dursban—a

residential-use

pesticide

product

containing the acutely toxic pesticide chlorpyrifos—is

illustrative. During the 1990s, dozens of people filed

lawsuits alleged that spraying Dursban to control

insects in their homes caused serious harm, including

to children who suffered from seizures, learning

impairments, and paralysis. See Jim Morris, The Stuff

in the Backyard Shed – The Pesticide Is Effective And

Sells Like Mad. But Is It Safe For Everyone?, U.S.

News

World

Report,

Nov.

1999,

https://perma.cc/9E9N-QRPW. DowElanco disclosed

in discovery hundreds of incidents of adverse health

effects from Dursban that it had failed to report to

EPA, leading EPA to impose what was then its largest

civil penalty for a violation of FIFRA’s adverse effects

reporting provision. EPA, EPA Fines DowElanco For

unlawful).

Failure to Report Pesticide Health Effects (May 2,

1995), https://perma.cc/D7C9-6F66.

Based on the poisoning reports, EPA scientists

recommended amending the Dursban label to instruct

people to stay out of the area during certain

applications and to seek immediate medical attention

if they experience headaches, nausea, unusual

fatigue, or dizziness. EPA, Memorandum Reviewing

Chlorpyrifos Poisoning Data at 6-7, 41 (Jan. 14, 1997),

https://perma.cc/H7JA-NC9V. EPA’s recommendations led manufacturers to amend Dursban labels to

end certain uses and to provide additional instructions to reduce exposures. EPA, Agreement Reached

Between EPA and Chlorpyrifos Pesticide Registrants

(June 6, 1997), https://perma.cc/4SV2-UYA7. EPA’s

2000 human health risk assessment considered the

poisonings and found unacceptable risks from

residential uses, which spurred DowElanco to

voluntarily cancel virtually all residential uses. Carol

Browner, Dursban Announcement (June 8, 2000),

https://perma.cc/H4ES-G5CP; see EPA, Interim

Reregistration Eligibility Decision for Chlorpyrifos at

viii-ix, 3-6 (2002) (EPA-738-R-01-007) (describing

agreement); Chlorpyrifos; Cancellation Order, 65 Fed.

Reg. 76233, 76234 (Dec. 6, 2000).

As another example, a district court determined in

2022 that Monsanto had potentially violated FIFRA,

7 U.S.C. § 136d(a)(2), by failing to submit evidence to

EPA regarding the conclusions reached by Monsanto’s

toxicology expert and the company’s response. See

Chapman v. Monsanto Co., 2022 WL 3971287 at *810 (S.D. Tex. 2022). Specifically, Monsanto failed to

tell EPA that the expert had advised that glyphosate

could be genotoxic and should be tested for

genotoxicity and that Monsanto never conducted the

studies the expert recommended, including of the

formulated product Roundup. Id.

Under FIFRA, manufacturers must inform EPA of

any adverse effects from their pesticides, including

information uncovered in tort litigation. Such

information, including in the form of jury verdicts,

furthers FIFRA’s requirement that manufacturers

ensure their pesticide labels provide adequate

warnings and directions to protect health.

II. States Have Authority To Determine

Whether

EPA-Accepted

Labels

Are

Adequate To Protect Health And To

Afford Greater Protection.

Under the cooperative federalism scheme

embodied in FIFRA, states can impose more stringent

health protection than EPA. See 7 U.S.C. § 136v(a). In

doing so, states are not bound by FIFRA’s

unreasonable adverse effects standard, which

requires EPA to balance the human health risks

against the economic and other benefits of using the

pesticide. See id. § 136(bb). 4 States can instead decide

to afford greater health protection or strike the

For pesticides used on food, FIFRA defines

“unreasonable adverse effects” to incorporate the Federal Food,

Drug and Cosmetic Act’s more health-protective standard. 7

U.S.C. § 136(bb)(2). To promulgate a tolerance regulation

allowing residues of a pesticide on food, EPA must find the

pesticide “safe,” meaning there is reasonable certainty of no

harm to the general population and to children. 21 U.S.C.

§ 346a(b)(2)(A)(i)-(ii); id. § 346a(b)(2)(C)(ii)(I).

balance differently.

EPA conducts a series of risk assessments,

including for occupational exposures, to determine

whether exposures will result in risks that exceed the

risk level the agency deems acceptable. See, e.g., EPA,

Assessing Human Health Risk from Pesticides (Jan.

23, 2026), https://perma.cc/M59T-46CR. Where EPA

finds risks of concern, it assesses the pesticide’s

benefits to growers and balances the risks against

those benefits. See, e.g., EPA, Registration Review

Process (Oct. 30, 2025), https://perma.cc/Q7WELDN9. The agency can thus decide that avoiding

increased costs to growers justifies exposing people to

what it deems unacceptable health risks.

For example, EPA decided to allow workers who

apply the pesticide paraquat to be exposed to risks of

concern from aerial spraying on cotton because it

deemed the use critical. EPA, Paraquat Dichloride

Interim Registration Review Decision at 29 (July

2021) (EPA-HQ-OPP-2011-0855-0307). It allowed

workers to apply paraquat through ground spraying

with a respirator, and not in an enclosed cab, to

provide growers flexibility. Id. at 32-33. And the

agency allowed farmworkers to enter treated fields

before the risks would be below its acceptable risk

level because the longer re-entry prohibition could

render the pesticide unusable for the crop. Id. at 35.

In striking a different balance, states have banned

pesticides that EPA allows to be used, see, e.g., N.Y.

Comp. Codes R. & Regs. Tit. 6, § 326.2(c)(17) (2021)

(chlorpyrifos cannot be sold or used in New York), or

have afforded greater health protections by, for

example, prohibiting aerial spraying or imposing

additional requirements to protect workers. Compare

Or. Admin. R. 603-057-0545(2)(b)-(c) (2026) (Oregon

prohibitions on aerial spraying and expansion of time

required before returning to fields after spraying)

with EPA, Interim Reregistration Eligibility Decision

for Chlorpyrifos at 81, 82, 85-86 (2002) (EPA-378-R01-007). And states have imposed limits on pesticide

spraying in close proximity to schools and daycare

centers. Cal. Code Regs. Tit. 3, § 6691 (limiting

pesticide application methods within one-quarter mile

of schools and daycare centers in California).

When states adopt stronger safeguards, they are

essentially finding that the EPA-accepted label fails

to provide adequate warnings and directions to

protect health. See Bates, 544 U.S. at 442 (“States

have ample authority to review pesticide labels to

ensure they comply with both federal and state

labeling requirements.”); see also 7 U.S.C. § 136w-1

(states exercising primary enforcement authority may

bring misbranding actions before state administrative

bodies and courts). EPA, therefore, has no monopoly

on deciding what instructions for use are adequate to

protect human health.

State limitations on pesticide use can be

communicated through the EPA-accepted pesticide

label. Indeed, current EPA policies allow

manufacturers to add state-specific use prohibitions

to the label without notifying EPA, provided the state

limitation is phrased as “Not Registered for Use” in

the state or registered subject to specified safeguards.

See EPA, Pesticide Labeling Questions & Answers at

16. Non-notifications

(May

25,

2025),

https://perma.cc/GE9Z-DU6D; EPA, DRAFT Proposed

PR Notice 2025-NEW (Revised PRN 98-10) at 25-26

(Jan. 5, 2026) (EPA-HQ-OPP-2025-2863-0002).

The word “[u]niformity” in the heading of FIFRA’s

label preemption provision, 7 U.S.C. § 136v(b), reflects

the fact that there is one nationwide label that often

includes state-specific content. See, e.g., Label for

ACE-jet, EPA Reg. No. 74578-2 at 3 (Jan. 25, 2022),

https://perma.cc/V6ZC-BRDX (acephate label lists

state use limitation and instructs to check with state

authorities for additional use regulations). There is no

“crazy-quilt ” of conflicting labels, Bates, 544 U.S. at

451, just one label incorporating state-specific

directions.

State pesticide use restrictions can also spur

changes in EPA’s pesticide registrations and the

manufacturers’ labels. For example, states added

safeguards beyond EPA’s requirements for use of

mevinphos after it caused large numbers of worker

poisonings. See, e.g., Wash. State Dep’t of Agric., RuleMaking Order To Restrict The Use Of Mevinphos

(Apr. 15, 1994), https://perma.cc/RA9V-SFZ8. 5 When

the manufacturer subsequently agreed to voluntarily

cancel the mevinphos registration to avoid an EPA

suspension,

EPA

required

amended

labels

incorporating California’s worker protections as a

condition of most sales during the phase-out period.

See Mevinphos; Amendment to Cancellation Order

and FIFRA Section 6(g) Notification, 60 Fed. Reg.

17357, 17358 (Apr. 5, 1995) (prohibiting hand-held

Several workers who were poisoned sued the pesticide

manufacturer, including for failure to warn of the risks posed by

mevinphos. See Ruiz-Guzman v. Amvac Chemical Corp., 7 P.3d

795 (Wash. 2000).

sprayers and requiring respirators, protective

eyewear, and chemical-resistant clothing).

As another example, several states limited

agricultural uses of chlorpyrifos to address scientific

evidence linking exposures during pregnancy with

learning and behavioral disorders. See supra at 13-14;

see also EPA, Chlorpyrifos: Revised Human Health

Risk Assessment for Registration Review at 6-7, 3249 (Dec. 29, 2014) (EPA-HQ-OPP-2008-0850-0195)

(EPA findings linking exposures during pregnancy to

learning and behavioral disorders in children). For

example, the California Department of Pesticide

Regulation initiated cancellation proceedings, which

culminated in Dow Agrosciences (the primary

chlorpyrifos maker at the time) agreeing to cancel

almost all chlorpyrifos uses in California. Cal. Dep’t of

Pesticide Reg., Agreement Reached to End Sale of

Chlorpyrifos by February 2020 (Oct. 9, 2019),

https://perma.cc/GE9Z-DU6D.

FIFRA expressly preserves state authority to

afford workers and others greater protection when

they find EPA-accepted labels inadequate to protect

public health. Indeed, when states adopt more

protective pesticide regulations, they often spur EPA

strengthen

federal

registrations

and

manufacturers to provide more protective label

instructions. Juries deciding state failure to warn

claims can likewise spur manufacturers and EPA to

improve pesticide labels, while also providing

compensation to people who have been harmed by the

manufacturer’s prior failure to ensure that its labels

will protect against harm.

III. FIFRA Allows EPA To Authorize Pesticide

Use In Situations Where It Lacks

Complete Information To Find The Label

Adequate To Protect Health.

FIFRA allows EPA to authorize pesticide use in

many situations where, by statutory design, the

agency has incomplete information about the

pesticide’s risks to human health. In these situations,

EPA has not made a fully informed judgment that the

label contains all necessary warnings and directions.

First, FIFRA allows EPA to conditionally register

a new pesticide or additional uses of an alreadyregistered pesticide, even though the manufacturer

has not submitted all the studies required for

registration. 7 U.S.C. § 136a(c)(7)(A)-(C). EPA must

find that the additional uses will not significantly

increase the risk of unreasonable adverse effects and

that new active ingredients will not cause

unreasonable adverse effects during the conditional

registration period. EPA, however, makes these

findings without the full suite of studies required for

registration. Id.; see GAO, Pesticides: EPA Should

Take Steps to Improve Its Oversight of Conditional

Registrations at 11-12 (2013) (GAO-13-145)

(describing EPA’s widespread issuance of conditional

registrations, some lasting a decade or more).

Second, FIFRA authorizes EPA to issue emergency

exemptions for unregistered uses of pesticides in a

defined geographic area where EPA determines an

emergency exists, most often because of a pest

outbreak. 7 U.S.C. § 136p. EPA can reissue emergency

exemptions in successive growing seasons if an

application for registration has been filed. See 40

C.F.R. § 166.25(b); id. § 166.25(b)(2)(ii). EPA allows

use of these pesticides often for years without the

studies and risk assessment findings needed to

Third, FIFRA requires iterative reviews of

pesticide registrations to ensure pesticides meet

FIFRA’s standards, but each review identifies gaps in

scientific evidence that must be addressed in future

reviews. Pesticide labels reflect only the data on hand

and not necessarily all ways the pesticide can harm

human health.

The initial round of review entailed re-registering

older pesticides that had been allowed to stay on the

market without meeting the stronger health and

environmental standards incorporated into FIFRA in

1972. See FIFRA Amendments, Pub. L. No. 35-396,

§ 8, 92 Stat. 819, 827 (1978); 7 U.S.C. § 136a-1.

Congress recognized, however, that at the end of this

one-time review, there would still be gaps in toxicity

studies and exposure data (particularly for risks to

children from pesticides used on food crops). See 21

U.S.C. § 346a(b)(2)(C)-(D); see infra at 27.

Registered and re-registered pesticides are subject

to ongoing 15-year registration reviews to ensure that

the pesticides continue to meet FIFRA’s unreasonable

adverse effects standard based on evolving science

and regulatory requirements. 7 U.S.C. § 136a(g); 40

C.F.R. § 155.40(a); id. § 155.53(a). Under EPA’s

regulations promulgated pursuant to 7 U.S.C.

§ 136a(g)(1)(A)(ii), EPA can issue interim registration

review decisions addressing some, but not all, of the

pesticide’s risks. 40 C.F.R. § 155.56. The regulations

also allow EPA to require new studies at the

culmination of registration review to fill in gaps in

information about the pesticide’s health effects. Id.

§ 155.58(b)(3). Moreover, the deadline for this round

of registration review has been extended to be 19

years and may be extended further. 6 As a result, many

pesticide registrations and EPA-accepted labels have

not been brought in line with current standards and

science. See EPA, Upcoming Registration Review

Actions (Aug. 26, 2025), https://perma.cc/W9EJ2XWC.

In addition, FIFRA authorizes the courts of

appeals to set aside registration decisions that are not

supported by substantial evidence. 7 U.S.C. § 136n(b).

When a registration review decision is set aside, as

occurred with EPA’s 2020 interim registration review

decision for glyphosate, the pesticide may continue to

be used under the previous registration decision. In

Natural Resources Defense Council v. EPA, the court

of appeals held that EPA’s cancer finding for

glyphosate was not supported by substantial evidence

because EPA discounted studies that correlated

glyphosate exposures with cancer. 38 F.4th 34, 45-51

(9th Cir. 2022). The court vacated the human health

portion of the interim registration review decision

upon finding that “EPA’s errors in assessing humanhealth risk are serious.” Id. at 52. EPA’s cancer

finding remains in limbo, as EPA has yet to make a

While Congress set a 2022 deadline for completing the

first round of registration review, Congress subsequently

extended that deadline to October 2026, and pending legislation

would extend the deadline further to October 2031. Fiscal Year

2023 Consolidated Appropriations Act, Pub. L. No. 117-328,

§ 711(a), 136 Stat. 4459, 6083 (2022); H.R. 7567 § 10204(a)(2),

119th Cong. (2026).

new registration review decision for glyphosate. As a

result, no legally valid cancer determination currently

underpins the EPA-accepted Roundup label.

Fourth, FIFRA authorizes EPA to allow continued

sale and use of existing stocks of a pesticide whose

registration has been voluntarily canceled, provided

that EPA “determines that such sale or use is not

inconsistent with the purposes of” FIFRA. 7 U.S.C.

§ 136d(a)(1); see Nat’l Coal. Against the Misuse of

Pesticides v. EPA, 867 F.2d 636, 641 (D.C. Cir. 1989)

(EPA allowed continued sale and use of existing stocks

to avoid time-consuming cancellation proceedings).

Often the manufacturer voluntarily cancels a

pesticide registration after contesting EPA’s riskassessment findings and stated intention to pursue

cancellation of the registration. In these situations,

EPA has found that use in accordance with the

pesticide label poses unacceptable health risks. See,

e.g., 60 Fed. Reg. at 17358 (allowing use of mevinphos

pesticide products that lacked the recent label

protections for workers); 65 Fed. Reg. at 76238-39

(allowing four years to use existing chlorpyrifos stocks

for termite control despite EPA’s finding that the use

presented unacceptable risks to children); see supra at

11, 13.

Merely because EPA has accepted a pesticide label

does not mean it has a sufficient basis for determining

that the warnings and directions are adequate to

protect people from serious harm. FIFRA authorizes

EPA to act on the basis of the information it has at a

given point in time and to ratchet up health

protections in subsequent reviews as informational

gaps are filled.

IV. EPA Has Adopted Regulatory Schemes

That Fail To Require Comprehensive

Cancer Testing Or Warnings.

EPA’s implementing regulations do not require

cancer testing of the formulated pesticide product or

cancer warnings. As a result of these regulatory gaps,

EPA lacks sufficient information to make a fully

informed finding about the pesticide product’s

propensity to cause cancer, and the agency has not

taken on the task of ensuring pesticide labels have

adequate cancer warnings. These deficits reinforce

that EPA’s acceptance of a pesticide label does not

amount to a conclusive cancer determination that

could preempt state failure to warn suits.

In Bates, this Court concluded it was unlikely that

Congress intended to preempt state-law liability for

crop damage because EPA does not review pesticide

efficacy. 544 U.S. at 450. Acknowledging this

statement in Bates, the United States concedes that

“a pesticide might be misbranded for reasons outside

the scope of what EPA assesses during the

registration process.” U.S. Br. 27. But efficacy is not

the only information deficit in EPA’s pesticide

reviews. EPA similarly lacks sufficient information to

assess cancer risks posed by pesticide products and it

does not require label warnings for cancer.

A. EPA’s Regulations Require Cancer

Testing Of A Pesticide’s Active

Ingredient, But Not Of The Formulated

Pesticide Product.

Pursuant to its statutory obligation to specify the

information required to support a pesticide-

registration application, 7 U.S.C. § 136a(c)(2)(A), EPA

has promulgated regulations setting out the

minimum data requirements for registration. Those

regulations require chronic testing for carcinogenicity

to be assessed by testing only the active ingredient,

not the actual end-use product that will be applied in

the field. 40 C.F.R. § 158.500(c)-(d). As a result, EPA

lacks information to address the cancer-causing

potential of the whole pesticide product or the

adequacy of the pesticide label to address such risks.

While FIFRA defines “pesticide” to include “any

substance or mixture of substances intended for

preventing, destroying, repelling, or mitigating any

pest,” 7 U.S.C. §136(u), it differentiates between a

pesticide’s “active” and “inert” ingredients. An

ingredient is considered “active” if it “will prevent,

destroy, repel, or mitigate any pest,” id. § 136(a), while

“inert” “means an ingredient which is not active,” id.

§ 136(m). A pesticide formulation combines active and

inert ingredients into end-use products. See

Ruckelshaus v. Monsanto Co., 467 U.S. 986, 997

(1984).

For Roundup, this means that EPA has required

cancer testing of the active ingredient glyphosate, but

not of Roundup’s inert ingredients. One of Roundup’s

“inert” ingredients is a surfactant, which reduces

surface tension, allowing the pesticide spray to adhere

to and penetrate waxy leaves. RA44 (¶ 33). There is

evidence in the trial record that the surfactant makes

Roundup more genotoxic than glyphosate alone.

RA44-45 (¶¶ 34, 36); RA80.

Since EPA requires cancer testing only of the

active pesticide ingredient, the agency is not basing

its registration decisions on the cancer-causing

potential of the end-use product. If a failure to warn

claim established that an ingredient other than

glyphosate increases Roundup’s cancer-causing

properties, a jury verdict (like the one in this case)

could serve an important gap-filling purpose. It would

hold Monsanto accountable for failing to warn of the

cancer risks associated with the entire product.

FIFRA also does not require disclosure of inert

ingredients that have the potential to cause cancer or

other chronic illnesses. FIFRA deems a pesticide

“misbranded” if “the label does not bear an ingredient

statement,” but the ingredient statement needs to

disclose only the total percentage of all inert

ingredients, not the names of inert ingredients. 7

U.S.C. § 136(q)(2)(A); id. § 136(n)(1).

EPA has classified many commonly used inert

ingredients as hazardous. See e.g. Ctr. for Env’t

Health v. McCarthy, 192 F. Supp. 3d 1036, 1040 (N.D.

Cal. 2016) (EPA has designated hundreds of inert

ingredients as hazardous.). Indeed, there is evidence

in the trial record that Roundup contains cancercausing inert ingredients, including ethylene oxide, 3

Tr. 2007-008, which EPA has classified as a human

carcinogen.

EPA,

Ethylene

Oxide

Interim

Registration Review Decision at 21 (Jan. 2025) (EPAHQ-OPP-2013-0244-0435).

Because EPA registers pesticides without cancer

tests on the end-use product, it makes no

determination about the whole product’s propensity to

cause cancer when it accepts manufacturers’ pesticide

labels. Similarly, EPA requires no label disclosures of

cancer-causing inert ingredients. Endowing such

omissions in EPA-accepted labels with preemptive

effect would deprive people of critical information they

need to protect themselves from toxic pesticides.

B. EPA’s Regulations Require Label

Warnings For Acute Toxicity, But Not

For Cancer.

EPA has adopted regulations requiring acute

toxicity warnings, but not warnings for cancer or

other chronic health risks. Its acceptance of a

manufacturer label, therefore, cannot be deemed a

determination about whether a cancer warning

should be provided.

FIFRA directs EPA to classify pesticides as

restricted use when use of the pesticide in accordance

with its directions for use, warnings, and cautions

may generally cause unreasonable adverse effects

without

additional

restrictions.

U.S.C.

§ 136a(d)(1)(C). Restricted use pesticides can only be

applied by a certified applicator or under an

applicator’s direct supervision. Id. § 136a(d)(1)(C)(i)(ii).

To comply with FIFRA’s direction to classify

acutely toxic pesticides as restricted use, EPA has

promulgated regulations establishing a toxicity

classification system based on oral, dermal, and

inhalation exposures. 40 C.F.R. § 156.62. The most

acutely toxic pesticides are classified as restricted use.

7 U.S.C. § 136a(d)(1)(C).

Under FIFRA, a label for a restricted use pesticide

is misbranded if it does not bear the skull and

crossbones, the word “poison,” and first-aid

treatments in case of poisonings. See 7 U.S.C.

§ 136(q)(2)(D). EPA’s regulations add that the

pesticide label must display a signal word

(“DANGER,” “WARNING,” and “CAUTION”),

reflecting the pesticide’s toxicity category, 40 C.F.R.

§ 156.64, as well as precautionary statements

describing the hazard and measures “to be taken to

avoid accident, injury or toxic effect or to mitigate the

effect,” id. § 156.70.

FIFRA has no analogous provisions requiring

cancer classifications or label disclosures. Nor has

EPA promulgated regulations governing cancer

classifications or warnings. As the United States has

explained, “EPA does not typically use the

registration process to address [such] harms by

requiring chronic-risk warnings on a pesticide’s

labeling.” U.S. Br. 11, Monsanto Co. v. Hardeman,

No. 21-241 (filed May 10, 2022), cert. denied, 142 S.

Ct. 2834 (Mem.).

The fact that some pesticide labels have cancer

warnings while others do not is an outgrowth of

choices made by the manufacturer, not EPA. Many

pesticide manufacturers have added cancer warnings

to comply with California’s Proposition 65, which

requires label warnings for pesticides the state has

determined are carcinogenic—even if EPA has not.

Cal. Code Regs. Tit. 27, § 25603. See, e.g., Label for

Kerb 3.3 SC, EPA Reg. No. 62719-578 at 31, 47 (Sept.

18, 2020), https://perma.cc/5G9R-T7Z5; Label for

Willowood Pronamide 3.3SC, EPA Reg. No. 87290-22

at 29 (Sept. 18, 2020), https://perma.cc/RKV4-FNQE.

EPA expressed concerns when labels making

Proposition 65 disclosures used language EPA had

assigned a specific meaning in its acute toxicity

regulations. To avoid a conflict, EPA has instructed

companies to use “notice” or “attention” instead of

“warning” because “warning” is a signal word

denoting an acute toxicity classification under EPA’s

regulations. Label Review Manual at 88. As long as

they do not use acute toxicity signal words,

manufacturers remain free to add Proposition 65

cancer warnings to their pesticide labels.

When EPA accepts a manufacturer’s label, it is not

passing on the need for a cancer warning. Its

acceptance of the label, therefore, cannot be

characterized as EPA’s determination that the label is

adequate without such a warning.

V. EPA Has Yet To Ensure That Pesticide

Registrations And Labels Protect Against

Serious Toxic Effects And Exposures That

Congress Requires EPA To Address.

As explained above, FIFRA authorizes EPA to

allow pesticides to be used in many situations where

it lacks sufficient information to ensure pesticide

labels contain adequate warnings and directions to

protect human health. EPA’s regulations also fail to

require comprehensive cancer testing of pesticide

products or cancer warnings. In addition, EPA lacks

sufficient information to protect people from other

toxic effects and exposures, as Congress has directed.

For this reason as well, the fact that EPA has accepted

a pesticide label cannot be deemed to be a conclusive

agency determination that the label provides

adequate warnings and directions to protect health.

A. EPA Lacks Sufficient Information To

Ensure That Labels Protect Against

Serious Noncancer Health Effects.

In 1996, Congress directed EPA to develop a

program to screen pesticides to determine if they

interfere with the body’s endocrine system or mimic,

block, or alter natural hormones, which can cause

fertility, cancer, metabolic, and developmental effects.

21 U.S.C. § 346a(p). When EPA finds such an effect, it

must take appropriate action “to ensure the protection

of public health.” Id. § 346a(p)(6). While EPA created

the endocrine disruption screening program in 1998,

see Endocrine Disruptor Screening Program, 63 Fed.

Reg. 42852 (Aug. 11, 1998), it has yet to obtain the

required tests for most pesticides. See EPA Office of

Inspector General, EPA’s Endocrine Disruptor

Screening Program Has Made Limited Progress in

Assessing Pesticides at 8-9 (2021) (21-E-0186)

https://perma.cc/DT76-JHSN. In a recent consent

decree, EPA committed to obtain the overdue testing

by 2035. Partial Consent Decree at 4-5, Alianza

Nacional de Campesinas v. EPA, No. 4:22-cv-09030JST (N.D. Cal. filed Jan. 21, 2025), Dkt. No. 87.

Without such testing, EPA has neither assessed nor

ensured pesticide registrations and labels protect

people from disruption of the human endocrine

system.

In its initial screening, EPA recommended more

comprehensive testing of many possible endocrine

disruptors, including dacthal. EPA, Endocrine

Disruptor Screening Program Tier 1 Screening

Determinations and Associated Data Evaluation

Records (Sept. 23, 2015), https://perma.cc/X2QW-

XDW4. Years after EPA ordered a thyroid study for

dacthal, the manufacturer submitted the required

study, which showed that very small exposures during

pregnancy can lead to low birth weight and impaired

development. EPA issued an emergency suspension

order upon finding that dacthal poses an imminent

hazard to fetuses even if pregnant farmworkers wear

personal protective equipment and use respirators.

See Pesticides; Emergency Order Suspending the

Registrations of All Pesticide Products Containing

Dacthal, 89 Fed. Reg. 64445, 64448 (Aug. 7, 2024).

The suspension order spurred the company to cancel

its dacthal registration. See Dacthal; Notice of

Receipt of Requests to Voluntarily Cancel Pesticide

Registrations, 89 Fed. Reg. 70181, 70181 (Aug. 29,

2024).

For decades after Congress required protection,

farmworkers have been exposed to dacthal and other

endocrine disrupting pesticides without label

directions needed to reduce serious health threats.

State failure to warn claims reinforce manufacturers’

obligations to ensure pesticide labels will protect

against this type of health crisis.

B. EPA Has Failed To Ensure That

Pesticide Labels Protect Children

From Pesticide Drift.

For many pesticides, EPA has failed to require

measures to protect children from toxic pesticide drift,

despite congressional direction to do so. As a result,

the pesticide labels lack adequate directions to protect

children from harm.

Congress has directed EPA to protect children

from aggregate exposures to pesticides used on food,

see 21 U.S.C. §§ 346a(b)(2)(A)(ii), 346a(b)(2)(C)(ii)(I),

which includes exposures to pesticide drift when

pesticide dust moves from the fields to homes and

schools. In 2014, EPA acknowledged that it had failed

to fulfill its legal obligation to address pesticide drift

and indicated that it would incorporate drift

safeguards in its forthcoming registration reviews.

EPA, Agency Response to “Pesticides in the Air - Kids

at Risk: Petition to EPA to Protect Children from

Pesticide Drift, (2009)” at 32 (Apr. 2, 2014) (EPA-HQOPP-2009-0825-0084).

EPA has since conducted risk assessments that

identify unacceptable drift risks from many toxic

pesticides unless spraying is prohibited in buffer

zones around schools, homes, and playgrounds.

However, EPA has yet to complete registration review

for these pesticides, and as a result, the pesticide

labels fail to mandate no-spray buffers. See Petition

for a Writ of Mandamus at 9-10, Pesticide Action &

Agroecology Network North America v. EPA, No. 253955 (9th Cir. filed June 25, 2025) Dkt. No. 1.1. In

addition, prior to July 2024, EPA registered new

pesticides without assessing drift or determining

whether the pesticide labels should require no-spray

buffer zones. See EPA, Implementing Chemical

Specific Human Health Spray Drift Analysis for

Pesticide Registration Actions at 3 (July 2024) (EPAHQ-OPP-2013-0676-0124).

EPA has also developed a protocol for screening

pesticides for volatilization, which occurs when a

pesticide converts into a gas or vapor and moves far

from

the

application site.

See

Pesticides;

Consideration of Volatilization in Pesticide Risk

Assessment: Notice of Availability and Request for

Comment, 79 Fed. Reg. 16791 (Mar. 26, 2012). EPA’s

protocol requires further testing where the screening

indicates potential volatility, but the agency has

rarely ordered manufacturers to conduct the follow-up

tests. Several amici challenged EPA’s 2021 interim

registration review decision for paraquat, in part,

because EPA had not obtained a volatility study

required under its policy. In response, EPA ordered

the manufacturer to conduct the study, but it will take

four years for the study to be completed and inform

revisions to the registration-review decision and

pesticide label. See Decl. of Edward Messina at 6-8,

Cal. Rural Legal Assistance Found. v. EPA, No. 2171287 (9th Cir. filed Mar. 17, 2026) Dkt. No. 84-2.

Without the full testing and exposure assessments,

EPA has insufficient information to ensure pesticide

labels protect people from pesticide drift and

volatilization.

In sum, EPA fails to ensure pesticide labels

provide adequate warnings and directions to protect

people from cancer and other chronic health effects

because of gaps in the information before the agency

and in the types of warnings it requires. Congress has

authorized some registrations without the full testing

necessary to ensure the labels will be adequate. EPA’s

regulatory schemes leave gaping holes in cancer

testing and warnings. And EPA has failed to

implement congressionally mandated toxicity testing

and exposure assessments. Due to these gaps, EPA’s

acceptance of a manufacturer’s pesticide label is no

guarantee that the label is adequate to protect human

health. Just as states may adopt use regulations to

afford greater health protection, juries may find EPAaccepted labels inadequate to protect health. An

uninformed or outdated registration is no defense to a

misbranding

offense

that

could

spur

the

manufacturer to provide adequate label warnings to

protect health. Nor is it a defense to a state failure to

warn claim. Juries deciding such claims can afford an

additional remedy for violating FIFRA’s misbranding

prohibition and compensate people who suffer harm

from inadequate label directions that manufacturers

can readily change.

CONCLUSION

The judgment of the court of appeals should be

affirmed.

Respectfully submitted,

GREGORY C. LOARIE

EARTHJUSTICE

1 Sansome Street

Suite 1700

San Francisco, CA 94104

PATTI GOLDMAN

Counsel of Record

NOORULANNE JAN

EARTHJUSTICE

810 3rd Avenue

Suite 610

Seattle, WA 98104

(206) 578-5868

pgoldman@earthjustice.org

Counsel for Amici Curiae

April 1, 2026

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.