For decades, fluoride has been a staple in public health initiatives, hailed as a cavity-fighting hero added to community water supplies. However, a rigorous nine-year research review has cast a shadow over this long-standing practice, suggesting that fluoride may have a more complex relationship with human health than previously acknowledged. The study, published in the journal JAMA Pediatrics, has sparked a heated debate and calls for a reevaluation of fluoride's role in public health.

The review's findings are alarming: as fluoride levels rise, IQ scores in children appear to drop. Specifically, every 1 part per million increase in urinary fluoride—a comprehensive measure of all fluoride sources consumed—was associated with a roughly 1 point decrease in a child's IQ score. While a 1-point drop may seem negligible for an individual, the study authors emphasize that on a population scale, the implications are profound. A 5-point decrease in a population's IQ could nearly double the number of individuals classified as intellectually disabled, highlighting the potential public health crisis at hand.

The study's journey to publication has been fraught with controversy. Conducted by scientists at the National Toxicology Program, which evaluates various exposures for potential health risks, the research began in 2015. It underwent several rounds of reviews, a process criticized by some as an attempt to delay its release. The full review was eventually published in August, and in September, it became the basis for a federal judge's ruling, ordering the US Environmental Protection Agency (EPA) to further regulate fluoride to protect children's intellectual development. US District Judge Edward Chen stated that the risk to health at exposure levels found in US drinking water was high enough to warrant regulatory action by the EPA under federal law.

The controversy surrounding fluoride is not new. In November, Robert F. Kennedy Jr., then President-elect Donald Trump's pick for US Health and Human Services secretary, referred to fluoride as "an industrial waste" and pledged that the Trump administration would advise utilities to cease adding it to public water supplies. This statement brought the issue to the forefront of public consciousness, reigniting the debate over fluoride's safety and efficacy.

Fluoride is a naturally occurring mineral found in soil, rocks, and water, and it is also a byproduct of fertilizer production. For years, it has been added to treated drinking water on the recommendation of the US Centers for Disease Control and Prevention (CDC) and the World Health Organization to prevent cavities. Fluoride works by remineralizing tooth enamel and making teeth more resistant to acid, thus protecting against tooth decay. However, in some areas with naturally high fluoride levels in well water, children have experienced dental fluorosis, a condition characterized by streaks and spots on the teeth.

In 2015, the US Department of Health and Human Services (HHS) lowered its recommended levels for fluoride in drinking water from a range of 0.7 to 1.2 parts per million to 0.7 parts per million to prevent fluorosis. The CDC continued to endorse the health benefits of water fluoridation, even naming it one of the "10 Greatest Public Health Achievements of the 21st Century." Yet, the recent research on fluoride's potential neurotoxicity has led environmental health experts to call for a reassessment of its risks and benefits.

Dr. Bruce Lanphear, an epidemiologist and professor at Simon Fraser University in Canada, who wrote a commentary on the new paper, states, "The evidence is sufficient. It's not definitive." He argues that there is a need to pause and review the evidence rather than dismissing the concerns. The new review includes 74 studies from 10 countries, with the majority coming from China, where researchers first observed differences in intelligence between communities with high fluoride exposure and those without.

The researchers meticulously analyzed each study, considering factors such as the age of the children, the methods of intelligence testing, and the measures of fluoride exposure. Some of the most compelling studies, conducted in Canada and Mexico, examined fluoride levels in the urine of pregnant women and later tested the IQ of their children. The data was sliced into three meta-analyses, revealing consistent findings that higher fluoride exposure was associated with lower IQ scores.

However, not all experts are convinced. Dr. Steven Levy, a professor of preventive and community dentistry at the University of Iowa, questions the conclusions of the research and the way JAMA Pediatrics is presenting them. He points out that the human studies included in the review were mostly from outside the US and that many were classified as having a high risk of bias. Levy also notes that animal studies conducted by the National Toxicology Program found no apparent decrease in learning and memory in rodents exposed to low to moderate fluoride levels.

Despite these criticisms, the consistency of the findings across the analyses is striking. Children with higher fluoride exposure, whether measured by dental fluorosis, water fluoride levels, or urinary fluoride, showed a consistent association with diminished IQ. This association is particularly concerning during early life when the brain is still developing. Emerging evidence suggests that fluoride might also be linked to behavioral problems in children, adding another layer of complexity to the issue.

Given the potential risks, especially during pregnancy and infancy, when the brain is most vulnerable, some experts, including Lanphear, recommend counseling pregnant women to limit their exposure to all sources of fluoride. Fluoride can be found in various products, including soft drinks, pesticides, and black tea, which bioaccumulates the mineral. Infants, in particular, absorb fluoride more readily than older children and adults, making it crucial to avoid mixing fluoridated water with infant formula.

In conclusion, the fluoride controversy highlights the delicate balance between the benefits of preventing cavities and the potential risks to cognitive development. As new evidence emerges, it is imperative for health agencies to reassess the risks and benefits of fluoride, ensuring that public health initiatives are based on the most current and comprehensive scientific understanding. The journey to finding the right balance is ongoing, but the health and well-being of future generations depend on our willingness to question, investigate, and adapt our practices in light of new knowledge.