Ninth Circuit Vacates Order Requiring EPA to Regulate Fluoridation of Drinking Water under TSCA
The U.S. Court of Appeals for the Ninth Circuit has vacated the district court order that required the U.S. Environmental Protection Agency (EPA) to regulate the “unreasonable risk” the court found to be posed by the fluoridation of drinking water. The Ninth Circuit issued a decision in the long-running case Food & Water Watch v. EPA, No. 25-384 (9th Cir. May 21, 2026), which stems from a Toxic Substances Control Act (TSCA) Section 21 citizen petition seeking to ban the addition of fluoride to drinking water.
The Ninth Circuit decision is important, but narrow. The panel did not decide whether fluoride in drinking water at 0.7 milligrams per liter presents an unreasonable risk to human health. It also did not resolve broader legal questions about the scope of evidence that may be considered in TSCA Section 21 litigation. Instead, the Ninth Circuit held that the district court abused its discretion by “commandeering” the case after the first bench trial, holding the case in abeyance to await new scientific evidence, and then conducting a second trial based on evidence the parties had not initially agreed to present.
For now, the Ninth Circuit’s decision unwinds the district court’s 2024 order requiring EPA to initiate rulemaking under TSCA Section 6(a) to manage the risks allegedly posed by community water fluoridation. But the case is not over. The Ninth Circuit remanded the case to the U.S. District Court for the Northern District of California with instructions to decide the merits based solely on the record from the first bench trial and to address standing issues.
Background
Since 1945, public water systems have added fluoride to drinking water for its dental health benefits. Currently, more than three-quarters of the U.S. population gets its drinking water from fluoridated public sources. Under the Safe Drinking Water Act (SDWA), EPA regulates the fluoridation of drinking water in public water systems. Currently, EPA permits public water systems to fluoridate drinking water up to 4.0 milligrams per liter (mg/L). EPA also set a non-enforceable “secondary standard” at 2.0 mg/L to prevent “moderate dental fluorosis.” Separately, the U.S. Department of Health and Human Services (HHS) recommends community water systems maintain fluoride concentrations of 0.7 mg/L for “optimal” dental benefits.
In 2016, a group of NGOs petitioned EPA under TSCA Section 21 to ban the fluoridation of drinking water, notwithstanding EPA’s allowance of the same under the SDWA. The petitioners argue that fluoride has neurotoxic effects when ingested, even at the “optimal” concentrations identified by HHS and thus presents an “unreasonable risk to human health.” EPA denied that petition in 2017. Pursuant to TSCA Section 21, the NGOs appealed to the federal district court for the Northern District of California.
As discussed in our previous alert, in September 2024, Senior Judge Edward Chen of the U.S. District Court for the Northern District of California concluded that fluoridation of drinking water at 0.7 mg/L poses an unreasonable risk of reduced IQ in children, and then ordered EPA to initiate a proceeding for rulemaking under TSCA to mitigate that risk. Food & Water Watch, Inc. v. EPA, No. 17-cv-02162-EMC (N.D. Cal. Sept. 24, 2024). The district court issued its decision after conducting two separate bench trials. Notably, that order was the first time that any court had ordered EPA to initiate a TSCA Section 6(a) rulemaking proceeding after the agency had denied a Section 21 citizen petition. The court based its decision on a controversial National Institutes of Health (NIH) report that concluded that “higher levels” of fluoride are linked to lowered IQ in children. The American Academy of Pediatrics, among others, question the validity of the NIH report. While the NIH report clearly stated further research was needed regarding any link between the lower levels of fluoride exposure typically found in U.S. drinking water and children’s IQs, the court nonetheless determined “there is not enough of a margin” of safety at those levels.
The Ninth Circuit’s Decision
EPA raised three principal issues on appeal: (1) whether the district court violated the party presentation principle by effectively taking over the case and holding a second bench trial on evidence that the district court found relevant and appropriate, in contrast to the evidence the plaintiffs initially presented on their own; (2) whether the district court erred by "encouraging” plaintiffs to use discovery to build a petition with evidence different from the record presented to EPA in the 2016 petition; and (3) whether plaintiffs’ claims are redressable and qualify for Article III standing, if the sole plaintiff supporting standing lives in a district where the public water naturally contains levels of fluoride beyond the level of harm the district court identified.
The Ninth Circuit agreed with EPA on the party presentation principle issue. Relying on United States v. Sineneng-Smith, 590 U.S. 371 (2020), the panel held that the district court departed too far from its role as neutral arbiter. The panel acknowledged that courts may take a “modest initiating role” but concluded that the district court’s remaining actions crossed the line.
After the first trial, both parties agreed that the district court should lift the abeyance and decide the case on the first trial record. The district court instead declined to do so, waited for additional scientific developments, and ultimately considered the final National Toxicology Program monograph and other evidence in a second trial. The Ninth Circuit held that the district court “effectively provided its own factual presentation,” and that the case no longer bore “a fair resemblance to the case shaped by the parties.” The panel therefore vacated the district court’s decision and remanded for the district court “to rule based solely on the first trial record.”
Separately, because both parties introduced evidence during the first trial that went beyond the 2016 petition record, the panel held that “in these circumstances,” the district court did not err by considering that evidence. But the panel expressly declined to decide whether TSCA Section 21 would allow consideration of evidence beyond the initial petition record in different circumstances.
The panel also remanded the standing issue, directing the district court to consider, in the first instance, EPA’s request for judicial notice and whether the noticed facts affect plaintiffs’ standing.
Impacts and Next Steps
The immediate practical effect is that EPA is no longer subject to the district court’s order to initiate TSCA rulemaking proceedings. It also delays the question of how EPA will reconcile court-ordered TSCA rulemaking with its existing allowance for fluoridated drinking water under SDWA. That is a significant development for EPA, drinking water systems, and stakeholders concerned about the potential use of TSCA Section 21 litigation to force EPA directly into risk management rulemaking without the benefit of prior risk evaluation specifically under TSCA.
The broader consequences are more limited. The Ninth Circuit did not resolve the core scientific dispute over fluoride, did not decide whether the first trial record establishes unreasonable risk, and did not answer how much evidence beyond the original TSCA Section 21 petition courts may consider in future cases. The panel also did not address what exactly EPA is required to do if a district court orders it to “initiate a proceeding” for rulemaking under TSCA Section 6(a), though this issue was not raised on appeal.
Still, the decision is likely to matter in future TSCA citizen petition litigation. It confirms that district courts may not develop their own factual record to displace the parties’ presentation of the case. The party presentation principle may constrain future attempts to use ongoing scientific developments, post-petition studies, or agency draft assessments to expand a TSCA Section 21 trial record after the parties have closed their evidentiary presentations.
On remand, Judge Chen will need to decide whether plaintiffs have standing and, if so, whether the first trial record supports an unreasonable risk finding under TSCA Section 21. If the district court again finds unreasonable risk, EPA may face renewed arguments that it must initiate a TSCA Section 6(a) rulemaking proceeding.
In the meantime, several states have reacted to the National Toxicology Program monograph on fluoride exposure and the 2024 district court decision. In March 2025, Utah became the first state to ban the addition of fluoride to public water, with its bill taking effect in May 2025. Florida followed suit shortly thereafter, with its ban taking effect in July 2025. As of May 2026, bills to ban fluoridation are pending in 10 other states, including Hawaii, Texas, Alaska, and Louisiana. By contrast, the state legislatures of Maine, New Hampshire, Montana, and North Dakota rejected fluoride bans.
In January 2026, EPA announced the next step in its review of potential public health risks associated with fluoride in drinking water and released the “Review of Science on Fluoride in Drinking Water: Preliminary Assessment Plan and Literature Survey” for public comment. Under the typical SDWA timeline, the next analysis of scientific information on potential health risks of fluoride in drinking water is not due until 2030. This scientific review, ahead of the regulatory schedule, indicates that, regardless of the disposition of this case, drinking water utilities should continue to monitor potential changes to the regulation of fluoride in water in the coming years.
If the district court rules in the plaintiffs’ favor, EPA’s January 2026 review also makes it more likely that EPA will attempt to move the entire matter to the Office of Water under TSCA Section 9(b) on the basis that the risk identified by the court “could be eliminated or reduced to a sufficient extent by actions taken under the authorities” of that office. If the district court rules in EPA’s favor, plaintiffs may appeal or seek rehearing.
Drinking water utilities should continue to monitor both the litigation and any parallel federal activity concerning fluoride under SDWA or through public health agencies. The Ninth Circuit’s decision reduces the immediate TSCA rulemaking pressure created by the 2024 district court order, but it does not remove fluoridation from the federal regulatory agenda.
Beveridge & Diamond’s Chemicals Regulation practice group and Chemicals industry group provide strategic, business-focused advice to the global chemicals industry. We work with large and small chemical and products companies whose products and activities are subject to EPA’s broad chemical regulatory authority under TSCA and state chemical restrictions.
