A study released on August 21 by the National Toxicology Program (NTP) on the effects of fluoride exposure on cognitive function concluded that fluoride levels in drinking water above 1.5 milligrams per liter are associated with lower IQ scores in children.

The NTP, a part of the U.S. Department of Health and Human Services, started its study in 2016 with all its work undergoing rigorous scientific evaluation and peer review by the National Academies of Science, Engineering and Medicine (NASEM), and experts from several federal health agencies.

NTP research found that for every additional 0.5mg/L increase in fluoride exposure, there could be a 2.5-point drop in IQ. This inverse relationship was observed across various countries, indicating a global health concern. This relationship has been described as linear in some analyses, suggesting no safe level of exposure when considering cognitive health.

The data sets comprised both human epidemiological studies and animal research, with a focus on neurodevelopmental outcomes. These studies were drawn from diverse geographical locations, ensuring a broad spectrum of exposure levels and demographic backgrounds.

The NTP has recommended a reevaluation of fluoride levels in public water supplies. While not advocating for an immediate cessation of water fluoridation, the program suggests that current guidelines might need adjustment to protect public health, particularly for vulnerable populations.

Children, especially during critical developmental stages, and fetuses are identified as the most susceptible to fluoride’s cognitive effects. Prenatal exposure through maternal consumption has been linked to neurobehavioral deficits in offspring, highlighting the importance of monitoring fluoride intake during pregnancy. Additionally, individuals living in areas with naturally high fluoride levels or where water is treated with higher-than-average fluoride concentrations face increased risks.

The NTP calls for further research to pinpoint safer exposure thresholds and for public health policies to consider these cognitive risks alongside dental health benefits.

The primary sources of fluoride exposure include:

• Drinking Water: The most discussed and often the primary source, especially where fluoride is added for dental health or where natural levels are high.
• Dental Products: Toothpaste, mouth rinses, and fluoride treatments in dental offices.
• Food and Beverages: Certain foods and beverages, particularly tea, can contain significant fluoride levels due to soil and water content.
• Industrial Exposure: Certain industries emit fluoride, which can contaminate local water supplies or air.

According to the 2023 Water Quality report from the Mukilteo Water and Wastewater District, fluoride is added to the water for dental health. The average concentration of fluoride in its water system is 0.7 part per million (or 0.7 mg/L). The same levels of fluoride were reported in the 2023 Alderwood Water & Wastewater report.

According to documentation by the Snohomish PUD and the Snohomish County Health Department, fluorinated water is also added as a dental additive in the following communities at a concentration of 0.6-0.7 mg/L: Brier, Edmonds, Granite Falls, Lake Stevens, Mill Creek, Monroe Mountlake Terrace, and Sultan.

Non-fluorinated drinking water is found in the communities of Darrington, Gold Bar, Lakewood, Maltby, Snohomish, and Stanwood.

The release of the NTP study will most likely reignite the debate on fluoride use in drinking water. While the study is not calling for an outright ban on fluoridation, it strongly advocates for caution and further research into fluoride’s cognitive effects, especially in children. As the debate continues, the focus remains on balancing dental health benefits with potential cognitive risks.