The Obama-appointed US judge Edward Chen found fluoridation could cause developmental damage and lower IQ in children at levels to which the public is generally exposed in drinking water. Though the ruling did not state the level at which fluoridation would damage brains, the levels in US water present an unreasonable risk, the court found.
https://www.theguardian.com/us-news/2024/oct/04/fluoridation-water-epa-risk-assessement