Readers of the Environmental Law Monitor have followed methylene chloride (MC), the solvent best known for its use in paint stripping, through nearly every stage of its modern regulatory life.
In “Partially Stripped,” we examined EPA’s decision to retreat from a proposed complete ban and instead prohibit only consumer paint-stripper uses. In “9th Circuit: EPA’s Review of Methylene Chloride Will Remain Limited for Now,” we covered the 9th Circuit’s refusal to disturb EPA’s risk evaluation while the agency reconsidered it. We later discussed EPA’s proposed overhaul of methylene chloride regulation in “EPA Proposes Ban on Common Solvent and Processing Aid Methylene Chloride,” and then analyzed the agency’s sweeping final rule in “Don’t You Know That You’re Toxic? EPA Spears Most Uses of Controversial Solvent.” What began as a dispute over a single solvent has steadily evolved into a broader debate about the scope of EPA’s authority under the Toxic Substances Control Act (TSCA).
That debate reached a critical turning point on September 15, when a unanimous 5th Circuit panel vacated EPA’s 2024 methylene chloride risk-management rule and the unreasonable-risk determination underlying it. In East Fork Enterprises, Inc. v. EPA, No. 24-60227 (consolidated with No. 24-60256), the court concluded that EPA committed multiple legal and evidentiary errors, granted the industry petition for review, denied the Sierra Club’s competing challenge, vacated both the rule and the risk determination, and remanded the matter to EPA. The decision may ultimately prove as significant for TSCA jurisprudence as it is for methylene chloride itself.
The rule at issue stemmed from EPA’s post-2016 effort to reassess existing chemicals under the amended TSCA. In its 2020 risk evaluation, EPA examined 53 conditions of use for methylene chloride and found unreasonable risk for 47 of them while concluding that six did not present unreasonable risk. Two years later, however, EPA fundamentally changed its approach. Without altering the underlying scientific record, the agency replaced those use-specific findings with a single determination that methylene chloride presented an unreasonable risk as a “whole chemical.” EPA simultaneously abandoned its prior assumption that workers used personal protective equipment (PPE) when evaluating occupational exposures. The resulting 2024 rule prohibited 40 conditions of use and allowed 13 industrial and commercial uses to continue only under a stringent Workplace Chemical Protection Program.
The 5th Circuit rejected both premises underlying that rule. Beginning with EPA’s “whole chemical” determination, the court held that TSCA requires EPA to determine whether a chemical presents unreasonable risk under its particular “conditions of use.” Because different uses can present different levels of risk, the court concluded that EPA lacked authority to replace use-specific findings with a single chemical-wide determination. That holding struck at the heart of EPA’s post-2021 approach, which allowed the agency to regulate some uses based not on risks associated with those uses themselves, but on an overall finding that the chemical posed unreasonable risk somewhere within its use profile.
The court likewise rejected EPA’s decision to disregard PPE during its risk evaluation. EPA had treated PPE primarily as a risk-management tool rather than as part of the conditions under which a chemical is actually used. The 5th Circuit disagreed, holding that where the record demonstrates that PPE is used in practice, EPA must account for it when evaluating risk. The court emphasized that TSCA requires EPA to assess risks based on reasonably foreseeable real-world conditions, not hypothetical workplaces stripped of existing protective measures. Although the court did not require EPA to assume perfect compliance with workplace safety requirements, it concluded that the agency could not simply presume noncompliance without evidentiary support.
Perhaps the most consequential aspect of the opinion, however, concerns the meaning of “unreasonable risk.” Reaffirming that “Congress did not enact TSCA as a zero-risk statute,” the court rejected the notion that EPA may regulate toward the lowest achievable level of risk or apply a precautionary principle whenever scientific uncertainty exists. Instead, the court explained that the statutory term necessarily tolerates some degree of risk and requires EPA to demonstrate why a particular level of risk is actually unreasonable. Relying in part on Loper Bright, the court further concluded that determining what constitutes an unreasonable risk is not solely a matter of agency expertise but a legal question that courts must independently evaluate. In practical terms, EPA’s interpretation of “unreasonable risk” no longer receives the level of judicial deference the agency had often expected.
The court’s skepticism extended to EPA’s underlying scientific analysis. EPA’s occupational exposure limits rested largely on a small number of studies and substantial uncertainty factors that dramatically reduced permissible exposure levels. The 5th Circuit found that EPA discounted contrary evidence, failed to adequately engage with relevant human data, and relied on methodological assumptions that were excessively conservative. Reviewing the record under TSCA’s substantial-evidence standard, the court concluded that key components of EPA’s scientific analysis were unsupported and failed to reflect the “best available science” required by the statute.
Further, Section 6 authorizes EPA to regulate chemicals only “to the extent necessary” to eliminate unreasonable risk, and the 5th Circuit emphasized that this language imposes meaningful limits on the agency’s choice of remedies. EPA must consider factors such as a chemical’s benefits, economic consequences, and the availability of technically and economically feasible alternatives. The court found that EPA failed to adequately address evidence regarding substitutes and economic feasibility and improperly treated uncertainty regarding compliance as a justification for broad prohibitions. EPA, the court explained, bears the burden of demonstrating that its chosen restrictions are necessary; it cannot shift that burden to regulated entities.
Notably, the Sierra Club fared no better. The court rejected each of the organization’s arguments that EPA should have regulated methylene chloride more aggressively, including challenges concerning fenceline exposures, susceptible populations, and ozone depletion. In doing so, the court narrowed several theories environmental groups may attempt to pursue in future TSCA litigation.
The implications of East Fork extend well beyond methylene chloride. The decision interprets several foundational TSCA concepts that recur throughout EPA’s existing-chemicals program, including “conditions of use,” “unreasonable risk,” and Section 6’s requirement that restrictions be imposed only to the extent necessary. As a result, the ruling is likely to feature prominently in ongoing challenges involving perchloroethylene (PCE), trichloroethylene (TCE), carbon tetrachloride, and future Section 6 rules. Although binding only within the 5th Circuit, the opinion provides persuasive authority that regulated parties will undoubtedly invoke elsewhere.
The decision may also have consequences outside the administrative-law context. Plaintiffs frequently rely on EPA findings as evidence of hazard, notice, or an applicable standard of care, and experts often cite EPA risk determinations as authoritative support for their opinions. East Fork gives defendants a published appellate opinion that carefully scrutinizes an EPA risk determination and identifies both scientific and legal shortcomings. While the decision does not suggest that methylene chloride is harmless, it provides a useful framework for challenging regulatory conclusions that rest on disputed assumptions, limited data sets, or highly conservative analytical choices.
For now, East Fork sends EPA back to the drawing board on methylene chloride. More importantly, it redraws several of the boundaries governing EPA’s authority under TSCA. Whether other courts ultimately adopt the 5th Circuit’s reasoning remains to be seen. But for manufacturers, processors, users, and defense counsel, the decision provides a powerful new roadmap for challenging how EPA identifies risk, evaluates scientific evidence, and crafts chemical regulations under Section 6.