Opening briefs have been filed by industry petitioners, the Sierra Club, and EPA in a case challenging EPA’s 2024 rule banning most uses of methylene chloride.  The lawsuit has critical implications not only for EPA’s regulation of the solvent but for future risk management rules and risk evaluations promulgated under the Toxic Substances Control Act (TSCA).

The case, East Fork Enterprises Inc. v. EPA, No. 24-60256, is before the Fifth Circuit.  Industry petitioners are requesting that the court vacate the methylene chloride rule and its underlying risk evaluation in their entirety.  The Sierra Club, taking the opposite position, contends the rule does not go far enough but seeks only a remand to EPA without vacatur.

“Extreme” Risk Evaluation

One of the central arguments in the industry petitioners’ October 9 brief is that EPA’s methylene chloride risk evaluation conflated the potential for any harm with “unreasonable risk,” the threshold for regulation under TSCA.  “EPA treated a use as risky if there was even a theoretical possibility of health risks,” the brief states, a stance described as “contrary to the statutory text and Congress’s regulatory structure.”

The industry petitioners argue this approach represents massive EPA overreach.  “Under EPA’s extreme (and incorrect) reading of TSCA, EPA can prohibit a wide range of commercial activities simply by saying a chemical substance poses unreasonable risk,” the brief continues.

In its opening brief, filed December 13, EPA argues that the agency has sole discretion to determine what constitutes unreasonable risk.  “Congress assigned to EPA the task of determining what risks are ‘unreasonable’ for a given chemical substance based on EPA’s scientific and technical expertise,” the agency states.  “Applications of that expertise are entitled to the Court’s respect.”

Last term, the Supreme Court struck down Chevron deference—a longstanding precedent requiring courts to defer to “permissible” agency interpretations of statutes they administer—in Loper Bright v. Raimondo. Nevertheless, EPA cites Loper Bright, emphasizing language clarifying that the Administrative Procedure Act “mandate[s] that judicial review of agency policymaking and factfinding be deferential.”

The industry petitioners also contend two policy reversals made by the Biden EPA regarding risk evaluations: the adoption of a “single determination” of a chemical’s risk and the removal of the assumption that workers use personal protective equipment. These changes led the Biden EPA to replace a Trump-era methylene chloride risk evaluation with a revised version in 2022.

“Assumption Upon Assumption”

Other industry attacks focus on the risk management rule’s stringent limits on methylene chloride exposure concentrations, which are significantly lower than OSHA’s.  According to the industry petitioners, EPA ignored human exposure studies, relied on a single rat study, and “piled assumption upon assumption upon uncertainty” to reduce the acceptable exposure level “100-fold.”

In response, EPA contends that the industry petitioners misunderstand the toxicology underlying the limits. The agency also defends its use of “uncertainty factors” to extrapolate findings from limited studies, including a policy of basing certain calculations on the 1st percentile of human susceptibility to ensure more conservative protections.

These strict exposure limits prompted EPA to ban many uses of methylene chloride in the risk management rule. EPA argues that it had reason to believe compliance with the limits was not feasible for the banned uses, while the industry petitioners claim the bans were implemented “simply because EPA was uncertain whether businesses would be able to comply with EPA’s new exposure limits.”

Fenceline Communities

The Sierra Club’s challenge is comparatively narrow, primarily focusing on methylene chloride’s risks to fenceline communities.  In a supplement to its risk evaluation, EPA found that methylene chloride air releases elevated cancer risks in these communities.  However, EPA “never determined whether those risks are unreasonable” and “fail[ed] to address those risks” in the risk management rule, the Sierra Club’s October 9 brief states.

In its brief, EPA acknowledges that it “identified some existing risk to fenceline communities” but argues that the risk management rule “adequately address[es] that risk.”  TSCA does not require EPA to “formally determine” whether the risks identified in the supplement were unreasonable because it was conducted after the risk evaluation was completed, the brief argues.  Instead, EPA “opted to factor in the potential risk to fenceline communities as a human health effect that informed the Rule’s choice of restrictions.”

The Sierra Club also challenges EPA’s failure to evaluate the risk methylene chloride poses to the ozone layer, while EPA maintains that the chemical “is not an ozone depleting substance.”

More on EPA’s methylene chloride risk management rule can be found here.