Fluoride Action Network

Abstract

Over the past 75 years, health authorities have declared that community water fluoridation-a practice that reaches over 400 million worldwide-is safe. Yet, studies conducted in North America examining the safety of fluoride exposure in pregnancy were nonexistent. When a Canadian study reported that higher fluoride exposure in pregnant women was associated with lower IQ scores in young children, critics attacked the methodology of the study and discounted the significance of the results. Health authorities continued to conclude that fluoride is unequivocally safe, despite four well-conducted studies over the last 3 years consistently linking fluoride exposure in pregnancy with adverse neurodevelopmental effects in offspring. We describe the challenges of conducting fluoride research and the overt cognitive biases we have witnessed in the polarized fluoride debate. The tendency to ignore new evidence that does not conform to widespread beliefs impedes the response to early warnings about fluoride as a potential developmental neurotoxin. Evolving evidence should inspire scientists and health authorities to re-evaluate claims about the safety of fluoride, especially for the fetus and infant for whom there is no benefit.

References

  1. Needleman, H. L. Salem comes to the National Institutes of Health: notes from inside the crucible of scientific integrity. Pediatrics 90, 977–981 (1992).

  2. Newbrun, E. Effectiveness of water fluoridation. J. Public Health Dent. 49, 279–289 (1989).

  3. Centers for Disease Control and Prevention. Water Fluoridation Data & Statistics. Monitoring Fluoridation in the United States.

  4. Choi, A. L., Sun, G., Zhang, Y. & Grandjean, P. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environ. Health Perspect. 120, 1362–1368 (2012).

  5. Bashash, M. et al. Prenatal fluoride exposure and cognitive outcomes in children at 4 and 6–12 years of age in Mexico. Environ. Health Perspect. 1, 1–12 (2017).

  6. National Research Council (NRC). Fluoride in Drinking Water: A Scientific Review of EPA’s Standards (National Academies Press, Washington, DC, 2006).
  7. Mullenix, P. J., Denbesten, P. K., Schunior, A. & Kernan, W. J. Neurotoxicity of sodium fluoride in rats. Neurotoxicol. Teratol. 17, 169–177 (1995).

  8. Green, R. et al. Fluoride exposure during fetal development and intellectual abilities in a Canadian birth cohort. JAMA Pediatr. 173, 940–948 (2019).

  9. Jenco, M. American Academy of Pediatrics (AAP) continues to recommend fluoride following new study on maternal intake and child IQ. AAP News (August 19, 2019).

  10. Picard, A. Fluoride won’t make you dumber, but the ‘debate’ about its safety might. The Globe and Mail (August 23, 2019).

  11. Berezow, B. A., No, Fluoride Doesn’t Lower IQ. It Fails To Satisfy Hill’s Criteria of Causality (2019).

  12. Science Media Centre. Expert reaction to study looking at maternal exposure to fluoride and IQ in children. https://www.sciencemediacentre.org/expert-reaction-to-study-looking-at-maternal-exposure-to-fluoride-and-iq-in-children (2019).

  13. Off, C. & Howden, C. As it happens. https://www.cbc.ca/radio/asithappens/as-it-happens-tuesday-edition-1.5339960/october-29-2019-episode-transcript-1.5341184 (2019).

  14. Iheozor-Ejiofor, Z. et al. Water fluoridation for the prevention of dental caries. Cochrane Database Syst. Rev. https://doi.org/10.1002/14651858.CD010856.pub2(2015).

  15. American Dental Association. Responses to fluoride study flood in from all over the globe. ADA News.

  16. National Toxicology Program (NTP). Systematic Literature Review on the Effects of Fluoride on Learning and Memory in Animal Studies (National Toxicology Program (NTP), Research Triangle Park, NC, 2016).

  17. Ritchey, S. Maternal Fluoride and IQ—The Scientific Community Pushes Back (Science Based Medicine, 2019).

  18. Valdez Jiménez, L. et al. In utero exposure to fluoride and cognitive development delay in infants. Neurotoxicology 59, 65–70 (2017).

  19. Bashash, M. et al. Prenatal fluoride exposure and attention deficit hyperactivity disorder (ADHD) symptoms in children at 6–12 years of age in Mexico City. Environ. Int. 121, 658–666 (2018).

  20. Kirkey, S. “So much is at stake”: Academics call for release of data behind controversial Canadian fluoride study. The National Post (October 29, 2019).

  21. Limeback, H. A re-examination of the pre-eruptive and post-eruptive mechanism of the anti-caries effects of fluoride: is there any anti-caries benefit from swallowing fluoride? Community Dent. Oral. Epidemiol. 27, 62–71 (1999).

  22. Centers for Disease Control and Prevention. Recommendations for using fluoride to prevent and control dental caries in the United States. Morb. Mortal. Wkly. 50, 1–42 (2001).

  23. Takahashi, R. et al. Fluoride supplementation (with tablets, drops, lozenges or chewing gum) in pregnant women for preventing dental caries in the primary teeth of their children. Cochrane Database Syst. Rev. https://doi.org/10.1002/14651858.CD01185.pub2 (2017).

  24. Canadian Pediatrics Society. The use of fluoride in infants and children. Pediatr. Child Health 7, 569–572 (2002).