TSCA “Conditions of Use” Rule: No “Whole-Chemical” Risk Determinations and Mandatory Consideration of Real-World PPE in MC Regulation

I. Introduction

East Fork Enterprises v. EPA (5th Cir. Sept. 15, 2026) is a significant Toxic Substances Control Act (“TSCA”) decision reviewing EPA’s 2024 final rule regulating methylene chloride (“MC”), a widely used industrial and commercial solvent with acknowledged acute toxicity hazards and carcinogenic properties.

The consolidated petitions came from:

  • Industry Petitioners (American Chemistry Council, East Fork Enterprises, Epic Paint Company), challenging EPA’s rule and risk determination as contrary to TSCA, arbitrary and capricious, and unsupported by substantial evidence.
  • Sierra Club, arguing EPA failed to go far enough to protect fenceline communities, genetically susceptible persons, and high-elevation residents allegedly affected via ozone depletion pathways.

The Fifth Circuit granted the Industry Petitioners’ petition, vacated the MC Rule and associated risk determination, denied Sierra Club’s petition, and remanded to EPA. The opinion is notable for (1) rejecting EPA’s “whole chemical” risk-determination approach under TSCA, (2) requiring that worker PPE be treated as a “condition of use” when it is reasonably foreseen, and (3) applying TSCA’s unusually demanding substantial evidence review to EPA’s toxicological assumptions, study selection, and exposure-limit setting.

II. Summary of the Opinion

The court held that EPA committed legal and evidentiary errors in both the risk determination and the risk-management rule.

  • TSCA requires condition-of-use risk determinations. EPA lacked authority to issue a “whole chemical” unreasonable-risk determination that effectively treated all conditions of use as requiring regulation.
  • PPE must be accounted for when reasonably foreseen. EPA’s revised assumption that workers do not wear personal protective equipment (“PPE”) violated TSCA’s “conditions of use” framework and lacked substantial evidence and reasoned explanation.
  • Exposure limits were not supported by substantial evidence. EPA’s acute (16 ppm/15 minutes) and chronic (2 ppm/8 hours) limits—roughly ten times more stringent than OSHA’s longstanding standards— reflected selective reliance on limited studies, failure to grapple with contrary human data, and excessively conservative uncertainty assumptions.
  • “Unreasonable risk” is not “zero risk,” and TSCA does not embed the precautionary principle. EPA’s methodology and choices resembled “lowest possible risk” regulation rather than TSCA’s “unreasonable risk” standard.
  • EPA may regulate only “to the extent necessary.” EPA impermissibly justified near-prohibition based on uncertainty about compliance and shifted the practical burden to regulated parties. It also inadequately treated statutory considerations of benefits, economic consequences, and feasible substitutes.
  • Sierra Club challenges failed. The court rejected claims regarding fenceline communities and genetic susceptibility on the merits, and held Sierra Club lacked standing to press the ozone-depletion theory.

III. Analysis

A. Precedents Cited (and How They Shaped the Holding)

1. TSCA’s substantial-evidence rigor and “no-zero-risk” baseline

The opinion is anchored in the Fifth Circuit’s TSCA touchstone: Corrosion Proof Fittings v. EPA, 947 F.2d 1201 (5th Cir. 1991). That case vacated EPA’s 1989 asbestos ban for lack of substantial evidence and failure to adequately consider less burdensome options, and it articulated two principles that the court deployed repeatedly here:

  • Rigorous substantial evidence review under TSCA. The court quoted Corrosion Proof Fittings v. EPA for the requirement that EPA’s decision be based on the “entire record,” including what detracts from the agency’s conclusion.
  • TSCA is not a “zero-risk statute.” The court used Corrosion Proof Fittings v. EPA to reject EPA’s effectively precautionary approach and to frame “unreasonable risk” as tolerating some level of risk (“No more, no less”).

The court also reinforced TSCA’s heightened evidentiary review by citing Vinyl Inst., Inc. v. EPA, 106 F.4th 1118 (D.C. Cir. 2024), for the proposition that TSCA’s substantial evidence standard is “more searching” than ordinary APA review.

2. Statutory “best data/best science” as an anti-speculation constraint

The court invoked Bennett v. Spear, 520 U.S. 154 (1997), which interpreted an agency duty to use the “best scientific and commercial data available” as a mandate against implementing law “haphazardly” on “speculation or surmise.” The Fifth Circuit used Bennett v. Spear as an interpretive analogue: TSCA’s “best available science,” “weight of scientific evidence,” and “reasonably available information” provisions operate similarly to constrain EPA’s discretion and prevent “freewheeling authority.”

3. Policy reversals must be reasoned and evidence-based

EPA’s PPE reversal was evaluated through administrative-law doctrines articulated in:

  • FCC v. Fox Television Stations, Inc., 556 U.S. 502 (2009), quoted (via BNSF Ry. Co. v. Fed. R.R. Admin., 105 F.4th 691 (5th Cir. 2024)) for the requirement of a “reasoned explanation” when an agency disregards facts underlying prior policy.
  • The court concluded EPA did not meet that standard: it speculated about noncompliance while simultaneously disclaiming any belief in widespread noncompliance, and it failed to reconcile the change with OSHA’s longstanding MC regulatory regime.

4. Judicial role after the end of Chevron deference

The court relied on Loper Bright Enters. v. Raimondo, 603 U.S. 369 (2024), to emphasize that courts independently interpret statutes. This mattered because EPA framed “unreasonable risk” as a largely technical agency call. The Fifth Circuit treated “unreasonable” as a statutory baseline courts must construe—much as the Supreme Court construed “undue hardship” in Groff v. DeJoy, 600 U.S. 447 (2023), and as the Fifth Circuit construed “unclassifiable” while vacating an EPA rule in Texas v. EPA, 137 F.4th 353 (5th Cir. 2024).

5. Precautionary principle requires clear congressional authorization

The court contrasted TSCA with statutes where Congress expressly requires “erring on the side of caution,” citing Lead Indus. Ass'n v. EPA, 647 F.2d 1130 (D.C. Cir. 1980), and relied on Me. Lobstermen's Ass'n v. Nat'l Marine Fisheries Serv., 70 F.4th 582 (D.C. Cir. 2023), for the proposition that courts should not infer a precautionary principle from unclear text. The Fifth Circuit imported Me. Lobstermen's Ass'n v. Nat'l Marine Fisheries Serv.’s “No more, no less” logic to TSCA: regulate to eliminate unreasonable risk, not to minimize risk to the lowest achievable level.

6. Study selection and the illegitimacy of relying on “only those results”

The opinion’s critique of EPA’s reliance on narrow or animal-only evidence was strongly shaped by Gulf S. Insulation v. U.S. Consumer Prod. Safety Comm'n, 701 F.2d 1137 (5th Cir. 1983), which vacated a product ban because exclusive reliance on a single animal study was not substantial evidence where epidemiological evidence existed, even if inconclusive. The court treated that logic as directly applicable: EPA could not discard “acceptable” human studies and rely solely on a rat study to set chronic limits.

The court also cited related evidentiary skepticism about animal-to-human inference in Johnson v. Arkema, Inc., 685 F.3d 452 (5th Cir. 2012), quoting Allen v. Pa. Eng'g Corp., 102 F.3d 194 (5th Cir. 1996), for the “very limited usefulness of animal studies” when the question is human toxicity—reinforcing the court’s view that EPA had to engage meaningfully with human workplace data.

7. Agencies must respond to significant comments

The court used Perez v. Mortg. Bankers Ass'n, 575 U.S. 92 (2015), to hold EPA had to respond to significant public comments—particularly Dr. Borak’s critique of the epidemiological studies. The court reinforced the same principle with Chamber of Comm. of U.S. v. SEC, 85 F.4th 760 (5th Cir. 2023).

8. Standing doctrine (Sierra Club ozone theory)

The standing analysis relied on Supreme Court and Fifth Circuit precedent:

  • TransUnion LLC v. Ramirez, 594 U.S. 413 (2021), for the core three-part standing test.
  • Clapper v. Amnesty Int'l USA, 568 U.S. 398 (2013), rejecting “highly attenuated” chains of possibilities.
  • Shrimpers & Fishermen of RGV v. Tex. Comm'n on Env't Quality, 968 F.3d 419 (5th Cir. 2020), cautioning that increased-risk claims often fail “actual or imminent” injury.
  • For procedural standing, Nat'l Infusion Ctr. Ass'n v. Becerra, 116 F.4th 488 (5th Cir. 2024), citing Massachusetts v. E.P.A., 549 U.S. 497 (2007), and limiting principles from Summers v. Earth Island Inst., 555 U.S. 488 (2009).
  • The court also cited Sugar Cane Growers Coop. of Fla. v. Veneman, 289 F.3d 89 (D.C. Cir. 2002), emphasizing that procedural steps must be plausibly connected to a different substantive outcome.

9. Additional interpretive/administrative supports

  • Wyo. Outdoor Council v. U.S. Forest Serv., 165 F.3d 43 (D.C. Cir. 1999), used to treat a regulatory preamble as evidence of contemporaneous agency understanding—supporting the court’s rejection of EPA’s post hoc “whole chemical” reading.
  • DOJ v. Fed. Lab. Rels. Auth., 991 F.2d 285 (5th Cir. 1993), for the proposition that agencies must follow their own regulations— critical because EPA’s then-operative procedural rule required risk determinations “under each condition of use.”
  • Noranda Alumina, L.L.C. v. Perez, 841 F.3d 661 (5th Cir. 2016), used to reject Sierra Club’s claim that EPA unlawfully departed from “settled policy” when the fenceline methodology was expressly a draft.
  • The court referenced other “ignore-the-record” cases (e.g., Am. Tunabout Ass'n v. Baldrige, 738 F.2d 1013 (9th Cir. 1984); Ctr. for Biological Diversity v. Zinke, 900 F.3d 1053 (9th Cir. 2018)) to underscore that agencies cannot sidestep significant contrary evidence.

B. Legal Reasoning

1. TSCA forecloses “whole chemical” unreasonable-risk determinations

The court’s statutory analysis is textual, structural, and reinforced by EPA’s own prior rules. TSCA repeatedly ties both evaluation and regulation to “conditions of use.” The court read 15 U.S.C. § 2605(a) and § 2605(b)(4)(A), in light of the statutory definition of “conditions of use” (15 U.S.C. § 2602(4)), to require discrete determinations by activity/circumstance.

Critically, the court treated EPA’s 2017 procedural rule as confirming that legal command: “determine whether the chemical substance presents an unreasonable risk . . . under each condition of uses within the scope of the risk evaluation.” EPA’s later attempt to re-interpret the preamble as allowing a whole-chemical approach failed because (a) the operative rule text was clear, (b) EPA had long applied it use-by-use, and (c) TSCA requires EPA to conduct evaluations “in accordance with” the procedural rule.

Doctrinal consequence: the decision establishes a Fifth Circuit rule that EPA may not use a whole-chemical unreasonable-risk determination as a shortcut to regulate conditions of use that are not themselves found unreasonably risky.

2. PPE is a “condition of use” when it is “reasonably foreseen”

The court treated PPE not as a discretionary “risk management” afterthought, but as part of the exposure reality TSCA requires EPA to consider in the risk evaluation: the statute commands consideration of exposure “under the conditions of use,” and “conditions of use” include what is “reasonably foreseen.” Given OSHA’s methylene-chloride standard (29 C.F.R. § 1910.1052), EPA could not simply assume away PPE without evidence and a reasoned explanation.

The court found EPA’s change arbitrary and capricious because it (1) conflicted with EPA’s earlier rationale that it would assume compliance absent case-specific facts, (2) relied on speculation about uncovered workers/noncompliance while disclaiming widespread noncompliance, and (3) lacked substantial evidence.

3. “Unreasonable risk” is a legal standard, not an agency-defined “precautionary” output

EPA argued “unreasonable risk” is a “technical determination.” The court rejected that framing: “unreasonable risk” is a statutory prudential baseline that must be applied consistent with TSCA’s guardrails (best available science, weight of evidence, transparency, and record-based decisionmaking). Post-Loper Bright Enters. v. Raimondo, the court emphasized it must interpret that baseline independently.

The opinion also signals that TSCA’s “unreasonable risk” standard cannot be operationalized as “no observed adverse effect” (or functionally zero-risk) without confronting the statutory word “unreasonable” and Congress’s deliberate choice not to include Clean Air Act-style “margin of safety” language.

4. Substantial evidence failures in EPA’s acute and chronic exposure limits

The court’s critique is not that EPA must never use uncertainty factors or animal studies; it is that, on this record and under TSCA’s heightened review, EPA’s choices became untethered from “the entire record.”

Acute (15-minute) limit (16 ppm)
  • EPA relied heavily on a small human study (“Putz study”) and treated modest, temporary vision impacts as a “precursor” to severe harm without explaining why that translated into “unreasonable risk.”
  • EPA down-adjusted using uncertainty factors in a way the court saw as effectively converting TSCA into a “NO adverse effect”/precautionary regime.
  • The court faulted EPA for discounting other evidence (including the “Winneke study,” workplace history, “immediately dangerous” concentration benchmarks, and OSHA’s much higher limit) without sufficient justification.
Chronic (8-hour) limit (2 ppm)
  • EPA relied principally on a rat study (“Nitschke study”) and used modeling to derive a conservative human-equivalent concentration, then effectively disregarded “acceptable” human epidemiological studies.
  • EPA’s limited response (e.g., bilirubin discussion) did not grapple with the point that the studies did not show clear adverse liver outcomes at far higher exposures, nor did EPA address Dr. Borak’s critique.
  • The court analogized directly to Gulf S. Insulation v. U.S. Consumer Prod. Safety Comm'n: “it is not good science to rely on a single experiment,” especially where human evidence exists.

5. Risk management: “to the extent necessary” means no bans by uncertainty or burden shifting

Even assuming some unreasonable risk exists, TSCA limits EPA to regulating “to the extent necessary” and requires consideration of benefits, economic consequences, and feasible/available substitutes.

The court held EPA misconceived its authority by justifying near-prohibition on: (a) uncertainty whether industries could comply with EPA’s newly reduced limits, (b) speculative concerns about ongoing attempted compliance, and (c) fear of increased MC use in sectors that had moved away. The court treated these as the type of “musings and conjecture” condemned in Corrosion Proof Fittings v. EPA (quoting Aqua Slide 'N' Dive Corp. v. Consumer Prod. Safety Comm'n).

The court also criticized EPA’s practical burden shifting: a lack of comments from some regulated parties could not substitute for EPA’s statutory burden to justify the restriction with evidence.

C. Impact

1. TSCA program structure: re-centering “conditions of use”

The decision sharply limits EPA’s ability to treat a chemical as regulable “as a whole” when the record shows heterogeneous risk across uses. In future TSCA § 6 actions within the Fifth Circuit (and persuasively elsewhere), EPA should expect litigation risk if it:

  • collapses distinct “conditions of use” into a single “whole chemical” finding, or
  • uses that collapse to justify regulating uses not supported by use-specific unreasonable-risk findings.

2. Worker protection realism: PPE must be integrated into risk evaluation when foreseeable

The ruling makes it difficult for EPA to assume away PPE in occupational settings where PPE is mandated, standard, or otherwise “reasonably foreseen.” It also signals that EPA cannot “move” PPE from risk evaluation to risk management merely to inflate risk findings, absent evidence and statutory justification.

3. Evidence discipline: TSCA substantial evidence as a meaningful constraint

The opinion demonstrates that TSCA’s substantial evidence standard is not rhetorical. EPA must expect courts to scrutinize study selection, treatment of contradictory human evidence, and the justification for conservative modeling choices—especially where agency outputs diverge dramatically from longstanding OSHA standards.

4. “Unreasonable risk” litigation after Loper Bright

By framing “unreasonable risk” as a judicially interpretable legal standard rather than an agency-defined technical endpoint, the decision invites more searching review of how EPA operationalizes the term across TSCA rules. This may encourage regulated parties to challenge not only data choices but also EPA’s implicit normative thresholds.

5. Sierra Club issues: limits of TSCA’s scope-setting and Article III standing

The court’s fenceline analysis suggests EPA retains some discretion to exclude pathways where methodology is not adequately developed under TSCA’s “best available science” and “reasonably available information” constraints, especially under statutory deadlines. Separately, the standing holding on ozone depletion underscores that climate/atmospheric theories must satisfy concrete injury and non-attenuated causation, even when asserted as procedural violations.

IV. Complex Concepts Simplified

  • “Conditions of use”: the real-world circumstances under which a chemical is made, used, or disposed of. Under TSCA, EPA must analyze risk in those specific circumstances (e.g., furniture stripping vs. lab use).
  • “Whole chemical” risk determination: EPA’s attempt to declare the chemical risky overall so that every use becomes regulable, even if some specific uses were previously found not to present unreasonable risk. The court held TSCA does not allow this shortcut.
  • PPE (Personal Protective Equipment): respirators, gloves, protective clothing, eye protection. If workers actually use PPE (or it is reasonably foreseeable they will), TSCA requires EPA to incorporate it into exposure estimates.
  • Acute vs. chronic exposure: short-term (e.g., 15 minutes) vs. long-term (e.g., 8 hours/day over years) exposure.
  • Point of Departure (POD): the exposure level in studies where an effect begins to show up (or no effect is observed).
  • LOAEL vs. NOAEL: “lowest observed adverse effect level” vs. “no observed adverse effect level.” Using LOAEL often leads agencies to add extra “uncertainty factors” to be more conservative.
  • Margin of Exposure (MOE) and “uncertainty factors”: tools EPA uses to compare expected real-world exposure to study-based effect levels, then adjust for uncertainty (differences among humans, study limits, etc.). The court faulted EPA for stacking conservative assumptions without adequate record support, yielding near-zero-risk thresholds under an “unreasonable risk” statute.
  • Substantial evidence (TSCA): more demanding than ordinary APA review; EPA must address contrary evidence in the record, not just present evidence supporting its preferred outcome.
  • “To the extent necessary”: TSCA authorizes regulation only as far as needed to eliminate the unreasonable risk—not to eliminate all conceivable risk or ban based on uncertainty.

V. Conclusion

East Fork Enterprises v. EPA reasserts statutory limits on TSCA chemical regulation and imposes meaningful discipline on EPA’s risk evaluation and risk management process. The Fifth Circuit held that:

  • EPA must make unreasonable-risk determinations by condition of use, not by “whole chemical” declaration;
  • PPE cannot be ignored where it is a reasonably foreseen workplace circumstance;
  • TSCA’s substantial evidence standard requires EPA to confront contrary human data and avoid selective study reliance;
  • “Unreasonable risk” is not “no risk,” and TSCA does not silently authorize a precautionary principle;
  • risk management must be no more than necessary, supported by evidence, and attentive to TSCA’s required consideration of benefits, economic consequences, and feasible substitutes.

The immediate practical result is vacatur of the MC Rule and its risk determination, but the broader significance is doctrinal: TSCA regulation—at least in this circuit—must remain tethered to use-specific findings, real-world conditions of use, and a record-based, non-speculative showing that the chosen controls (including bans) are actually necessary to eliminate unreasonable risk.