Choppy waters continuing for community water fluoridation

Two recent publications reached opposing views on the safety of community water fluoridation (CWF). A study by Singh et al., accepted on Feb 6, 2025, concluded that urinary fluoride concentrations measured prenatally and during childhood (child urinary fluoride concentrations above -0.47 on the log2 scale (corresponding to 0.72 mg/L) were associated with lower cognitive abilities, especially perceptual reasoning and verbal abilities, in Bangladeshi children. A New Zealand Ministry of Health, Manatu Hauora, evidence review of CWF, published 4 December 2024, found that this public health intervention was safe and effective for preventing dental caries. In addition the New Zealand review found that no high-quality evidence had been published since 2014 and 2021 to suggest a causal link between fluoride exposure at the levels used in Aotearoa New Zealand for CWF, 0.7-1.0 mg/L, and significant harm to health. It found that three studies for neurodevelopmental outcomes, including one by Grandjean et al. on over 1500 mother-child pairs, should be excluded from the review because they used a benchmark dose analysis of the amount of fluoride which led to the adverse effect of a decline in IQ of 1 or 5 IQ points, which was considered to be a wrong outcome. These opposing interpretations of the scientific literature have resulted in choppy waters continuing for community water fluoridation.