In an unpublished opinion, Food & Water Watch; et al. v. United States Environmental Protection Agency, No. 25-384 (9th Cir. May 21, 2026), the Ninth Circuit vacated and remanded a district court ruling that had found the addition of fluoride to drinking water at 0.7 mg/L presents an unreasonable risk to human health under the Toxic Substances Control Act (“TSCA”). The plaintiffs petitioned the EPA in 2016 under TSCA § 21 seeking a rule banning the addition of fluoride to drinking water. The EPA denied the petition, and the plaintiffs sought judicial review.
After two bench trials, the district court found that fluoridation at 0.7 mg/L presented an unreasonable risk and ordered the EPA to manage that risk under TSCA. The EPA appealed, arguing that the district court improperly took control of the case after the first bench trial, considered a record different from the one presented to the EPA, and erred in finding Article III standing.
The Ninth Circuit agreed with the EPA on the central procedural issue. Relying on the party-presentation principle, the Court explained that federal courts generally act as neutral arbiters of issues framed by the parties, rather than investigators who develop the factual record themselves. The Court held that the district court crossed that line after the first bench trial by refusing to decide the case on the record the parties presented, holding the matter in abeyance for approximately one-and-a-half years, waiting for additional scientific materials, and then effectively requiring the case to proceed on evidence the parties had not chosen to present.
The Ninth Circuit distinguished the district court’s initial invitation to address standing, which it viewed as permissible, from the Court’s later handling of the evidentiary record. According to the Court, the district court’s insistence on considering the later National Toxicology Program monograph, despite the parties’ prior agreement not to rely on it at the first trial, transformed the case beyond the parties’ presentation. The Court therefore vacated the judgment and remanded with instructions for the district court to rule based solely on the first trial record.
The Ninth Circuit rejected the EPA’s broader argument that the District Court was limited to the evidence submitted in the original 2016 TSCA petition. Because both parties introduced new evidence during the first trial, the Court held that the District Court did not err in considering that evidence under the circumstances. However, the Court declined to decide whether TSCA § 21 allows new evidence beyond the administrative petition record in other cases. The Court also remanded the standing issue for the District Court to consider EPA’s judicial-notice request in the first instance.
The decision provides a meaningful procedural safeguard for agencies and regulated parties. It confirms that courts reviewing agency action under TSCA must remain within the adversarial framework and decide the case the parties present. In scientific disputes where new research is constantly developing, that limitation may be critical. Otherwise, litigation could become open-ended, with courts delaying rulings to await additional studies rather than deciding the record before them.