According to a report released Wednesday by the U.S. National Toxicology Program, drinking water with fluoride levels more than twice the recommended limit is linked to lower IQ scores in children. While adding small amounts of fluoride to drinking water has long been hailed as one of public health’s greatest achievements for strengthening teeth and preventing cavities, the latest findings, based on studies in Canada, China, India, Iran, Pakistan, and Mexico, suggest a link between fluoride levels exceeding 1.5 milligrams per liter and lower IQ scores in children. Although the report did not quantify the exact IQ point decrease associated with different levels of fluoride exposure, some studies have shown that higher fluoride levels can lead to a 2-5 point decrease in children’s IQ scores. The U.S. has recommended a fluoride limit of 0.7 milligrams per liter since 2015, down from 1.2 milligrams per liter for the previous 50 years. The WHO recommends a maximum of 1.5 milligrams per liter. Approximately 0.6% of the U.S. population has access to drinking water with fluoride levels at or above 1.5 milligrams per liter.
