Fluoride is under fire.
A recent federal meta-analysis has found that fluoride exposure may slightly reduce children’s IQ, though not at the low levels commonly used in U.S. drinking water. Conducted by researchers at the National Institute of Environmental Health Sciences (NIEHS), the study observed a link between reduced IQ scores and fluoride concentrations in drinking water exceeding 1.5 mg/L, but no such effect was observed below this threshold. In the United States, public health guidelines recommend a fluoride level of 0.7 mg/L for optimal dental health.
The researchers, led by Kyla Taylor from NIEHS, noted uncertainty regarding the relationship between fluoride exposure and children’s cognitive development at levels under 1.5 mg/L when solely considering drinking water as the source of exposure. By analyzing the 11 highest-quality studies in their review, they found a 1.14-point decline in IQ for every 1 mg/L increase in urinary fluoride levels. However, none of the 74 studies included in the review were conducted in the U.S.; the majority came from countries such as China, India, and Mexico, where naturally occurring fluoride levels are often higher than in U.S. water supplies.
Critics of the study have pointed out that fluoride levels examined in these international studies often exceed U.S. guidelines. Dr. Brett Kessler, president of the American Dental Association (ADA), emphasized that fluoride levels in these regions are typically more than double the recommended U.S. standard. The ADA reiterated its support for fluoridation as a preventive measure against dental decay and encouraged continued use of fluoridated water along with other dental hygiene practices.
The meta-analysis has sparked debate within the public health community. While an editorial in JAMA Pediatrics praised the study for compiling and synthesizing existing data, another editorial expressed skepticism regarding the reliability of using urinary fluoride as a measure of long-term fluoride exposure. Dr. Steven Levy from the University of Iowa cautioned against over-interpreting the findings, noting that spot urinary samples are not a valid reflection of long-term exposure due to fluoride’s short half-life and day-to-day variations.
Despite the controversy, experts like Bruce Lanphear, who co-authored an editorial supporting the study, argued that the findings are sufficient to prompt further action by regulatory agencies such as the Environmental Protection Agency (EPA). He suggested that the study provides enough evidence to merit a reassessment of fluoride levels in drinking water. Meanwhile, the ADA maintained its position, advocating for continued fluoridation as a critical tool in preventing dental disease.
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