In a landmark decision that could impact the decades-old practice of water fluoridation in the United States, a federal judge has ruled that current levels of fluoride in drinking water pose an “unreasonable risk” to people's health. The decision, handed down by Judge Edward Cheng of the U.S. District Court for the Northern District of California, requires the U.S. Environmental Protection Agency (EPA) to take regulatory action to address this.
The Court emphasized that fluoride in drinking water affects “nearly all Americans.” Most people consume water treated to the long-recommended optimal level of 0.7 milligrams per liter (mg/L). But Judge Chen's decision, supported by compelling scientific evidence, shows that exposure to this level of fluoride can pose serious health risks, particularly to pregnant women and young children.
Challenging official orthodoxy
The ruling challenges long-held positions of public health organizations, including the Centers for Disease Control and Prevention (CDC) and professional societies such as the American Academy of Pediatrics (AAP) and the American Dental Association (ADA). These organizations promote water fluoridation as an important public health outcome. Amid growing scientific concerns, they defend the safety of fluoride and cite its role in preventing tooth decay.
Judge Cheng emphasized that scientific research clearly demonstrates the possible neurotoxic effects of fluoride, which are of particular concern to the developing brains of infants and young children.
The judge wrote:
Plaintiffs proved by a preponderance of the evidence that water fluoridation at the U.S. prescribed optimum concentration of 0.7 mg/L poses “unreasonable risks of harm to health or the environment, without consideration of cost and other non-risk factors, including unreasonable risks to potentially exposed or susceptible populations under the conditions of use.”
The decision follows several years of legal proceedings brought by environmental and consumer advocacy groups, including the Fluoride Action Network, who sought review under the Toxic Substances Control Act (TSCA).
The impact of fluoride on children's IQ
Key evidence in this decision came from the National Toxicology Program (NTP) under the U.S. Department of Health and Human Services, which conducted a systematic review of studies and found a significant association between fluoride exposure and reduced IQ in children, and found that fluoride levels as low as 1.5 mg/L can pose health risks.
Given this evidence, Judge Cheng rejected the EPA's defense that the threshold for fluoride toxicity is “not entirely clear. Judge Cheng found this argument unpersuasive. He emphasized that exposure to fluoride in U.S. drinking water is dangerously close to levels known to cause harm.
He insisted.
Overall, there is ample scientifically credible evidence establishing that fluoride poses risks to human health: it is associated with lower IQ in children, and it is dangerous at doses very close to the fluoride concentrations found in U.S. drinking water.
Chen further emphasized that a decline in IQ can have serious consequences. Studies have shown that a drop in IQ of just one or two points can lead to lower academic achievement, fewer employment opportunities, less productivity, and less income. The EPA itself acknowledges that a decline in IQ poses serious public health concerns for communities.
Pregnant women
According to the ruling, pregnant women across the country are already being exposed to fluoride levels that exceed dangerous thresholds established by scientific studies.
The Pooled Benchmark Dose Analysis concluded that for every 0.28 mg/L of fluoride concentration in a pregnant woman's urine, a child's IQ would be predicted to decrease by one point. This is of great concern because urinary fluoride concentrations in pregnant women in the United States range from a median of 0.8 mg/L to 1.89 mg/L, depending on the level of exposure. (emphasis in original)
Citing recent research, the judge noted that the “optimum” fluoridation level in U.S. drinking water, 0.7 mg/L, is nearly double the safe limit of 0.4 mg/L for pregnant women and their children.
Impact on U.S. drinking water
The EPA has a mandate to respond, while retaining discretion over specific actions. Potential responses range from issuing public warnings to banning fluoride in drinking water altogether. Furthermore, the decision highlights other areas where fluoride exposure may pose problems, such as areas with naturally high levels of fluoride in groundwater. Additionally, it raises concerns about fluoride intake from sources such as toothpaste.
Decades of debate and the future of fluoridation
For over 70 years, U.S. public health officials have promoted water fluoridation as a key strategy to improve dental health. In 1962, the U.S. Public Health Service (PHS) recommended that local water systems add fluoride to drinking water to prevent tooth decay. By 1975, the EPA recommended an optimal fluoride concentration of 1.2 mg/L and set a maximum limit of 4 mg/L, which aimed to balance fluoride's dental benefits with safety concerns.
However, as research increasingly revealed that fluoride could have adverse health effects, Surgeon General Vivek Murthy lowered the recommended levels in 2015. The new guidelines lowered the range from 0.7-1.2 mg/L to a consistent 0.7 mg/L.
However, this recent decision challenges long-standing fluoride recommendations and raises serious concerns about the safety of a practice that was once hailed as a major public health achievement. The plaintiffs' victory also marks the first time a case under the amended Toxic Substances Control Act (TSCA) has reached a federal court, setting an important precedent for future public health challenges related to chemical exposures.
The decision has sparked a new debate about fluoride as the EPA considers its next steps, with important implications for public health policy and the millions of Americans who consume fluoridated water.
What's next?
The EPA is expected to appeal the decision, but a growing body of evidence highlights the need for regulatory reform. The Court's decision also sets a significant precedent: it paves the way for citizen-initiated petitions to challenge long-standing environmental policies under the TSCA framework, which could impact future decisions regarding the safety of chemicals in consumer products and the environment.
The recent publication of a long-delayed study from the NTP on the neurotoxic risks of fluoride adds another layer to the debate, as both the scientific community and regulators continue to grapple with the broader effects of fluoride exposure.
