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On May 21, 2026, the U.S. Court of Appeals for the Ninth Circuit reversed a previous ruling by a lower court that mandated the Environmental Protection Agency (EPA) to establish new regulations governing fluoride concentrations in drinking water.
Understanding the Court’s Ruling
The appellate court’s opinion highlighted that the lower court had breached the principle of party presentation, which requires courts to serve as neutral arbiters rather than active investigators. Key concerns included the lower court’s decision to hold the case “in abeyance” while awaiting the release of the NTP Monograph, State of the Science Concerning Fluoride Exposure and Neurodevelopment and Cognition, and the subsequent bench trial that evaluated this publication. The appellate opinion characterized the lower court’s actions as “commandeering” and determined that it “strayed so far from the principle of party presentation that it constituted an abuse of discretion.”
The Lengthy Legal Journey
This litigation, initiated in 2017 following the EPA’s denial of a petition to discontinue fluoridation in the U.S., extended over seven years. This duration included a four-year phase during which the NTP Monograph underwent two failed peer reviews by the National Academies of Sciences, Engineering, and Medicine (NASEM). The document required further scientific assessment and multiple revisions before its eventual release on August 21, 2024. The report, along with a separate meta-analysis, has faced rigorous examination and criticism, as have many foundational studies.
Growing Evidence Against Neurodevelopmental Risks
Significantly, substantial evidence supports that community water fluoridation in the United States, and similar practices globally, does not negatively impact neurodevelopment. Recent findings include a November 2025 study involving nearly 27,000 individuals, which assessed various cognitive test scores throughout life. It revealed that “children exposed to recommended fluoride levels in drinking water demonstrate modestly improved cognitive performance in secondary school.” A 2025 national review from England found that existing research indicated no adverse effects on neurodevelopment or other non-dental health issues. an April 2026 U.S. study, representative of a large population over an extended period, concluded that “no evidence supports a negative association between [water fluoridation] and adolescent IQ or adult cognitive abilities.”
The Campaign for Dental Health commends the appellate court for overturning and remanding the lower court’s decision, ensuring that the case can be assessed impartially. They express confidence in the mounting body of evidence, which includes over 80 years of research and more than 7,000 studies, supporting the EPA’s stance.
