Fifth Circuit Vacates EPA’s Methylene Chloride Risk Management Rule
In a groundbreaking decision with significant implications for the regulation of existing chemicals under the Toxic Substances Control Act (TSCA), the Fifth Circuit vacated EPA’s risk management rule for the solvent methylene chloride (“MC”) on September 15, 2026.
“At every juncture of its scientific analysis, EPA has gone with the most extreme position,” the decision states. “EPA cannot justify the MC Rule in light of the TSCA’s requirements, the more demanding substantial-evidence standard that the TSCA requires, and the arbitrary and capricious standard.”
The ruling rejects policy positions developed under the Biden administration that were not defended by the Trump EPA. These include “whole chemical” risk determinations and the assumption that workers do not wear personal protective equipment (PPE)—policies EPA proposed to reverse in September 2025.
The ruling also addresses the meaning of “unreasonable risk,” the threshold for regulation under TSCA, by emphasizing that TSCA is not a zero-risk statute.
In addition to siding with industry-aligned petitioners, including the American Chemistry Council, the decision rejects a challenge from the Sierra Club that the MC rule is insufficiently protective.
The decision may implicate numerous previously conducted risk evaluations, which are already mired by delays. It also calls into question elements of EPA’s other risk management rules, including rules for carbon tetrachloride, perchloroethylene, and trichloroethylene, which are currently being litigated. EPA is reconsidering at least part of all three rules.
Finalized in 2024, the MC rule prohibits MC’s distribution for consumer use and most commercial uses. Uses not banned are subject to stringent workplace exposure limits. As discussed in a previous post, the Fifth Circuit appeared skeptical of EPA’s justifications for these restrictions during oral argument in June 2025.
“Whole Chemical” Approach and Assumption Workers do not Wear PPE
EPA completed its initial risk evaluation for MC in 2020 under the first Trump administration. The Biden EPA issued a revised risk evaluation in 2022. The revised evaluation replaced the initial evaluation’s condition-of-use-specific risk determinations with a determination that MC presents unreasonable risk “as a whole chemical substance.” Unlike the initial evaluation, the revision also assumed that exposed workers do not wear PPE. The panel held that both policy reversals were unlawful.
The court first examined the “whole chemical” approach. Emphasizing TSCA’s repeated use of the phrase “conditions of use” when describing how risk evaluations must be conducted, the court held that a whole-chemical determination exceeds EPA’s authority under the statute.
“There is no getting around the conclusion that the TSCA focuses on both determining and regulating risk according to the actual, separate ‘conditions of use’ for a given chemical or substance,” the decision states.
The court also found that EPA erred when issuing whole-chemical determinations under the Trump EPA’s regulations for risk evaluations, which the court held expressly requires use-by-use determinations. Those regulations were replaced by the Biden EPA in 2024.
Turning to PPE, the court held that PPE use is encompassed by the definition of “conditions of use.” EPA justified its reversal on assumed usage by arguing that some workplaces may not be covered by OSHA standards or comply with OSHA requirements. But the court found that this position was undermined by the initial MC risk evaluation. There, EPA found some evidence of PPE use and concluded that PPE use was reasonably foreseeable because EPA had no basis to assume noncompliance with OSHA requirements.
The court also pointed to statements in EPA’s revised risk evaluation indicating that the policy change was not an indication of widespread OSHA noncompliance and that MC is subject to numerous regulations. Combined with EPA’s decision not to alter the exposure assessments in the revised risk evaluation, the court found that EPA’s explanations “are remarkably self-contradictory.”
EPA’s reversal was therefore contrary to law, arbitrary and capricious, and lacked substantial evidence, the court concluded.
The Fifth Circuit’s ruling aligns with changes EPA proposed in 2025. EPA’s proposed rule would require use-by-use risk determinations and eliminate language prohibiting the assumption of PPE use.
“Unreasonable Risk” and Exposure Limits
The industry petitioners’ central argument is that EPA treated any MC risk as unreasonable and regulated beyond what was required to remove unreasonable risk. The panel agreed, concluding that “EPA’s approach to ‘unreasonable risk’ was far more conservative than the statutory term connotes.”
TSCA is not a zero-risk statute, the court held, emphasizing that the word “unreasonable” “must allow for some risk.” Moreover, unlike other environmental statutes, TSCA does not incorporate a precautionary principle, the court noted.
The court also rejected EPA’s argument that unreasonable risk is a factual finding deserving judicial deference, describing it instead as a “legal conclusion” drawn from scientific findings.
The court then turned to the MC rule’s exposure limits, including a 16 ppm limit for acute exposures and a 2 ppm limit for chronic exposures. These limits “lack epidemiological support, reflect selective use of data and failures to consider alternative acceptable data, and were based on unrealistic benchmark margins of error,” the decision states.
“In sum, the risk analysis did not accord with the best available science as the TSCA requires, and the results more closely approximate the precautionary principle than the statute’s ‘unreasonable risk’ standard,” the court held.
According to the court, EPA calculated the acute exposure limit by taking a human study finding peripheral vision impairment at 478 ppm and dividing by thirty, in part to account for variability among humans. But EPA’s exclusive reliance on the study was problematic, the court held, because EPA did not show that another human study with less concerning results should be disregarded entirely. The court also noted the gap between the 16 ppm limit and the 2,300 ppm concentration EPA rated as “immediately dangerous,” as well as OSHA’s 125 ppm standard.
The court’s analysis of the 2 ppm chronic exposure limit was similar. EPA exclusively relied on a single imperfect animal study, improperly excluded results from human studies, and reached a chronic exposure limit less than one-tenth of OSHA’s, the court held.
Regulatory Response and Alternatives
Even if the exposure limits had been correctly derived, the court concluded that the rule would still regulate more than necessary to remove the unreasonable risk.
First, the panel rejected EPA’s decision to prohibit MC uses when it was unsure whether industrial and commercial users would be able to satisfy “dramatically reduced” limits. “EPA cannot simply ban a chemical substance whenever it is ‘uncertain’ whether a risk will remain reasonable,” the decision states.
Second, the court concluded that the rule did not meet TSCA’s command that EPA consider the availability of alternatives. The court held that EPA did not seriously consider numerous comments explaining the unavailability of alternatives. In addition, EPA repeatedly failed to consider economic, productivity, and environmental losses associated with the adoption of alternatives, the court held.
Excluding Exposures
A final key holding arose from the Sierra Club’s challenge. Among other arguments, the environmental group contends that EPA did not adequately consider air and drinking-water exposures. Those exposures were excluded from the scope of EPA’s risk evaluation, although EPA considered them in a subsequent, truncated analysis.
The panel was not persuaded, pointing to uncertainties EPA identified in the supplemental analysis. “We cannot say that EPA is prohibited from excluding exposure pathways and exposure types that it does not have a methodology to accurately assess,” the decision states. “A fair reading of the TSCA leaves ample latitude for EPA to exclude certain exposure pathways when the science or methodology is not developed.”
The Ninth Circuit has held that TSCA’s directive requiring EPA to publish risk evaluation scoping documents based on the conditions of use it “expects to consider” does not authorize EPA to exclude conditions of use. But the Fifth Circuit found that precedent inapposite because that case concerned EPA’s regulations governing the conduct risk evaluations rather than a specific risk evaluation.
In a footnote, the court added that it did not necessarily agree with the Ninth Circuit’s reasoning, pointing to a separate provision of TSCA that might provide EPA with discretion.
That issue, too, is the subject of EPA’s proposed regulatory changes. EPA’s proposed revisions to the risk evaluation framework regulations would grant EPA discretion to exclude conditions of use and exposure pathways from risk evaluations.
The case is East Fork Enterprises v. Zeldin, No. 24-60227 (5th Cir.), filed May 10, 2024. Unless expedited, the court will issue its mandate November 7, 2026.
