## Facts

- EPA promulgated a rule under the Resource Conservation and Recovery Act (RCRA) listing numerous carbamate-related wastes as “hazardous,” including certain process waste streams (K-listed) and certain discarded chemical products or intermediates (U-listed).
- The listed compounds included carbamates, carbamoyl oximes, thiocarbamates, and dithiocarbamates, used in pesticides and in industrial applications (e.g., rubber, wood, textiles).
- Industry petitioners (including a manufacturers’ task force and chemical companies) filed consolidated petitions for review in the D.C. Circuit.
- Petitioners challenged only specific portions of the listings, arguing EPA relied on limited data and improperly treated some dithiocarbamate wastes as broadly “reactive” without adequately addressing contrary studies.
- Petitioners also argued EPA failed to connect toxicology/exposure evidence to the challenged listings and failed to show, listing-by-listing, how the regulatory factors for listing hazardous waste were applied.
- The petitions sought relief under the Administrative Procedure Act (APA), contending the challenged listings were arbitrary and capricious.

## Issues

1. Whether EPA provided a reasoned explanation, supported by the administrative record, for listing the challenged carbamate-related wastes as hazardous under RCRA.
2. Whether specific K- and U-waste listings were arbitrary and capricious under APA § 706(2)(A) because EPA failed to examine relevant data and explain its inferences (including extrapolations about reactivity and risk).
3. Whether EPA adequately demonstrated consideration of the regulatory listing factors in a manner permitting meaningful judicial review.

## Decision

- The D.C. Circuit granted the petitions in part and denied them in part.
- The court affirmed the portions of the rule where EPA sufficiently explained its scientific judgments and linked record evidence to the regulatory criteria.
- The court vacated and remanded the portions of the rule where EPA’s explanations were inadequate, including instances where EPA generalized from limited evidence (such as class-wide conclusions about dithiocarbamate reactivity) without addressing contrary data or explaining the extrapolation.
- The court emphasized it could not uphold agency action by supplying reasoning the agency itself did not provide.

## Legal Principles

- Under APA § 706(2)(A), agency rulemaking must satisfy a minimum standard of reasoned decisionmaking: the agency must consider relevant factors, evaluate relevant data, and articulate a rational connection between facts found and choices made.
- Judicial deference to technical and scientific judgments depends on the agency providing an intelligible explanation; deference does not excuse opaque reasoning or unexplained extrapolation.
- When regulations require consideration of specified listing factors (including toxicity and exposure potential), the agency must show—at least enough to permit review—how those factors were applied to the challenged listings.
- A reviewing court may affirm valid portions of a complex rule while vacating unsupported portions (partial vacatur) and remanding for further explanation or reconsideration.

## Conclusion

The D.C. Circuit upheld EPA’s carbamate-related hazardous-waste listings where EPA adequately connected record evidence to RCRA’s listing criteria, but vacated and remanded specific listings where EPA’s explanation and treatment of conflicting evidence fell below the APA’s requirement of reasoned decisionmaking.


Dithiocarbamate Task Force v. EPA, 98 F.3d 1394 (D.C. Cir. 1996)