Fluoride Exposure: Neurodevelopment and Cognition

Since 1945, the use of fluoride has been a successful public health initiative for reducing dental cavities and improving general oral health of adults and children. There is a concern, however, that some pregnant women and children may be getting more fluoride than they need because they now get fluoride from many sources including treated public water, water-added foods and beverages, teas, toothpaste, floss, and mouthwash, and the combined total intake of fluoride may exceed safe amounts.

Therefore, the National Toxicology Program (NTP) conducted a systematic review of the published scientific literature on the association between fluoride exposure and neurodevelopment and cognition. The NTP released their findings in a State of the Science Monograph (available below under Documents). A corresponding meta-analysis on children's IQ was published in JAMA Pediatrics on January 6, 2025 (see sidebar).

The NTP started this work in 2016. As with all research documents intended for publication, the NTP fluoride monograph and meta-analysis underwent rigorous scientific evaluation. The evaluation process has involved many steps. The draft fluoride monograph received critical feedback during peer-review by the National Academies of Science, Engineering and Medicine (NASEM), from other external experts, and from experts in several federal health agencies. After modifications were made, additional evaluation following a rigorous scientific framework was conducted by subject matter experts organized by the NTP Board of Scientific Counselors. This document is now complete and available for reference.

The monograph represents a thorough review of the data, and the various interpretations of the data, to accurately reflect what we know and where additional research is needed.

Findings

The NTP monograph concluded, with moderate confidence, that higher levels of fluoride exposure, such as drinking water containing more than 1.5 milligrams of fluoride per liter, are associated with lower IQ in children. The NTP review was designed to evaluate total fluoride exposure from all sources and was not designed to evaluate the health effects of fluoridated drinking water alone. It is important to note that there were insufficient data to determine if the low fluoride level of 0.7 mg/L currently recommended for U.S. community water supplies has a negative effect on children’s IQ. The NTP found no evidence that fluoride exposure had adverse effects on adult cognition.

The NTP uses 4 confidence levels - high, moderate, low, or very low - to characterize the strength of scientific evidence that associates a particular health outcome with an exposure. After evaluating studies published through October 2023, the NTP Monograph concluded there is moderate confidence in the scientific evidence that showed an association between higher levels of fluoride and lower IQ in children.

The determination about lower IQs in children was based primarily on epidemiology studies in non-U.S. countries such as Canada, China, India, Iran, Pakistan, and Mexico where some pregnant women, infants, and children received total fluoride exposure amounts higher than 1.5 mg fluoride/L of drinking water. The U.S. Public Health Service currently recommends 0.7 mg/L, and the World Health Organization has set a safe limit for fluoride in drinking water of 1.5 mg/L.

Application

An association indicates a connection between fluoride and lower IQ; it does not prove a cause and effect. Many substances are healthy and beneficial when taken in small doses but may cause harm at high doses. More research is needed to better understand if there are health risks associated with low fluoride exposures. This NTP monograph may provide important information to regulatory agencies that set standards for the safe use of fluoride. It does not, and was not intended to, assess the benefits of fluoride.