The recent article on community water fluoridation (CWF) by Broadbent et al.1 states that our meta-analysis of fluoride exposure and IQ deficits2 was based on “selective readings.” We wish to emphasize that we, for the first time, reviewed 27 eligible studies, many of which shared the unique advantage of stable populations with fairly constant exposures throughout the children’s lifetimes. Because the water–fluoride concentrations in the groups with elevated exposure varied between levels similar to those achieved by CWF and up to 10-fold that level, we refrained from attempting to link the average IQ loss of seven points to specific doses.
Because our study was misinterpreted in the media, we released a press statement, which concluded:
These results do not allow us to make any judgment regarding possible levels of risk at levels of exposure typical for water fluoridation in the US. On the other hand, neither can it be concluded that no risk is present. We therefore recommend further research to clarify what role fluoride exposure levels may play in possible adverse effects on brain development, so that future risk assessments can properly take into regard this possible hazard.3
Further, to ascertain the validity of previous Chinese reports on fluoride neurotoxicity, we carried out a pilot study in Sichuan.4 Although we examined only 51 children, our results support the notion that cognitive deficits occur at elevated fluoride exposures.
Broadbent et al.1 erroneously state that our press release “had to emphasize the fact that [our] research was irrelevant to CWF,”1(p72) and they give no reason why a threshold for developmental neurotoxicity would necessarily be higher than systemic doses associated with CWF. Also, although the authors1 emphasized potential biases in our meta-analysis,2 they downplayed the wide confidence intervals in their own study and the fact that the 10% who had not lived in fluoridated areas likely received fluoride supplements. Other dentistry colleagues5 claim that our work has been severely criticized and conclude that the Broadbent et al. study1 “found that fluoridation is not neurotoxic for either children or adults, and does not have a negative effect on IQ.” We are therefore concerned that the safety of elevated fluoride exposure is being exaggerated in ways similar to those employed by vested interests to misconstrue the scientific evidence of other neurotoxicants, such as lead, mercury, and certain pesticides.6 Firm dismissal of fluoride as a potential neurotoxic hazard would seem premature.
Acknowledgments
The authors declare they have no competing financial interests.
References
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