Fluoride in US water linked to lower IQ in children

A U.S. government report has concluded that fluoride in drinking water at twice the recommended limit is linked with lower IQ in children. This marks the first time a federal agency has identified this link with moderate confidence, highlighting potential neurological risks from high fluoride levels.

The report, based on previously published research, does not solely evaluate the effects of fluoride in drinking water. It points out a significant potential risk from elevated fluoride levels. According to the U.S. Centers for Disease Control and Prevention, fluoride helps strengthen teeth and reduce cavities by replenishing minerals lost during wear. Adding low levels of fluoride to drinking water has been considered a major public health achievement of the last century.

Ashley Malin, a researcher from the University of Florida who has studied the effects of higher fluoride levels in pregnant women on their children, called the report crucial for understanding the risk. She described it as the most rigorous of its kind.

Released on Wednesday, the long-awaited report comes from the National Toxicology Program, part of the Department of Health and Human Services. It reviews studies from Canada, China, India, Iran, Pakistan, and Mexico, concluding that drinking water with over 1.5 milligrams of fluoride per litre consistently associates with lower IQ in children.

The report did not quantify the exact IQ loss at different fluoride exposure levels, but some studies suggested a decrease of 2 to 5 points in children with higher exposures. Since 2015, federal health officials have recommended a fluoridation level of 0.7 milligrams per litre, down from the previous upper limit of 1.2. The World Health Organization has set a safe limit of 1.5.

Approximately 0.6% of the U.S. population, about 1.9 million people, are on water systems with naturally occurring fluoride levels of 1.5 milligrams or higher. Malin questioned how these individuals could be protected and what would make the most sense.

The 324-page report did not reach a conclusion about the risks of lower fluoride levels, indicating the need for more study. It also did not address the effects of high fluoride levels on adults.

The American Dental Association, which supports water fluoridation, had previously criticised earlier versions of the report and Malin’s research. A spokesperson mentioned that the organisation’s experts were still reviewing the final report.

A mineral found naturally in water and soil, fluoride was discovered about 80 years ago to reduce cavities in populations with higher natural levels. This led to efforts to increase its use for better dental health. Grand Rapids, Michigan, was the first U.S. city to add fluoride to tap water in 1945. Federal officials endorsed water fluoridation in 1950 to prevent tooth decay and continued its promotion even after toothpaste became available.

In 2015, officials lowered the recommended fluoride levels in drinking water to address fluorosis, a condition causing teeth splotches that had become more common among U.S. children. The Environmental Protection Agency has a longstanding requirement that water systems cannot exceed 4 milligrams of fluoride per litre to prevent skeletal fluorosis, a disorder causing weaker bones, stiffness, and pain.

Recent studies increasingly suggest a link between higher fluoride levels and brain development, raising concerns about the impact on developing fetuses and young children ingesting water with baby formula. Animal studies showed it could affect neurochemistry and cell function in brain regions responsible for learning, memory, executive function, and behaviour.

In 2006, the National Research Council highlighted limited evidence from China on neurological effects from high fluoride levels, calling for more research into its impact on intelligence. Continued research raised more questions, prompting the National Toxicology Program in 2016 to review available studies to determine if new limiting measures were needed.

Earlier drafts faced delays, and a committee of experts once stated that available research did not support the conclusions of a previous draft. Rick Woychik, director of the National Toxicology Program, emphasised the importance of ensuring the accuracy of the science due to the public and health officials’ interest in fluoride.

Malin suggested that pregnant women lower their intake from water and certain teas. She also proposed policy discussions on requiring fluoride content labels on beverages.