Fluoride Part II: Concerns Surrounding Fluoride
/Introduction:
In Fluoride Part I, we covered the basics of fluoride: why it’s significant in dentistry, fluoridation of community water, and dental fluorosis. In this part II post, I will address some of the other concerns pertaining to fluoride.
Skeletal fluorosis:
What is it?
Just as fluoride incorporates into the mineral component of enamel (hydroxyapatite), it also incorporates into the mineral component of bone (bone also has hydroxyapatite). This alters the mineral structure of bone, and although the bone becomes more electrostatically stable and compact, the bone strength is compromised.1
Quoting directly from the World Health Organization (WHO), “In skeletal fluorosis, fluoride accumulates progressively in the bone over many years. Early symptoms include stiffness and pain in the joints. Crippling skeletal fluorosis is associated with osteosclerosis, calcification of tendons and ligaments, and bone deformities.”2
Should I be concerned about developing it?
According to the WHO, “There is an elevated risk of skeletal effects at fluoride intakes above 6 mg/day. These intake levels occur in many areas of the world because of naturally high fluoride levels in the groundwater, notably in the Rift Valley of East Africa and in China.”3
To protect us from developing skeletal fluorosis, the US Environmental Protection Agency (EPA) has an enforceable drinking water standard that requires community water systems ensure that fluoride levels are less than 4.0 mg/L. The EPA also has a secondary non-enforcable standard of 2.0 mg/L (“Community water systems that exceed the fluoride secondary standard of 2 mg/L must notify persons served by that system as soon as practical but no later than 12 months from the day the water system learns of the exceedance) (4).
Does fluoride decrease IQ?
In 2012, Harvard released a review article by Choi et al (5) that supports the possibility that fluoride may negatively impact IQ. Some other past studies have come to the same conclusion but because they had obvious flaws and because this is the most recent article, I feel this is the one worth discussing for this segment.
This particular article was a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development. 27 studies were eligible, including numerous from the China National Knowledge Infrastructure database.
What did the review find?
SIDE NOTE:
To put 0.45 IQ points into context, a brief review of the literature on IQ in children brought up articles showing that IQ with childhood snoring is associated with a decrease of up to 10 points (6). Hearing loss is associated with a decrease in IQ of up to 4 points (7).
The review found that the standardized weighted mean difference in IQ score between exposed (high fluoride) and reference (low fluoride) populations was –0.45 (95% confidence interval: –0.56, –0.35) using a random-effects model. In other words, children exposed to high levels of fluoride (some water levels as shockingly high as 11.5 mg/L) averaged 0.45 points less on the intelligence quotient scale.
The article stated, “Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas.” Depending on how you read this, this is an alarming finding. Based on this statement alone one would expect that the children in high fluoride areas have IQs substantially lower than children in low fluoride areas. However, the review also reported shortcomings, including that the “estimated decrease in average IQ associated with fluoride exposure based on our analysis may seem small and may be within the measurement error of IQ testing.” In this case, the use of the term “significantly” refers to statistical significance rather than a substantial difference in IQ as it may seem to imply.
As just indicated, the article acknowledged the shortcomings of the included studies, stating that “the studies were generally of insufficient quality,” lacking key information on covariates and failing to report age adjustment of the cognitive test scores. There were also some methodological limitations noted.
What is the takeaway?
Unfortunately, at this time there is a lack of good science to definitively advise us in the safety of fluoride pertaining to effect on IQ. The study has the same conclusion, stating, “The results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment. Future research should formally evaluate dose–response relations based on individual-level measures of exposure over time, including more precise prenatal exposure assessment and more extensive standardized measures of neurobehavioral performance, in addition to improving assessment and control of potential confounders.” (5).
Are the chemicals used to fluoridate water unsafe?
This is an aspect of water fluoridation that I had not considered prior to writing this post series but came across the issue in my research. There has been concern raised by parties opposed to fluoridated water about the safety of the chemicals used to fluoridate water.
According to an article in the International Journal of Occupational Environmental Health, “Scientific evidence supports the fluoridation of public water supplies as safe for the environment and beneficial to people. Reports at the local, national, and international levels have continued to support this most important public health measure. There appears to be no concern about the environmental aspects of water fluoridation among those experts who have investigated the matter. Furthermore, since the chemicals used for water fluoridation are co-products of the manufacture of phosphate fertilizers, and the raw material used is a natural resource (rocks excavated for their mineral content), water fluoridation could accurately be described as environmentally friendly, as it maximizes the use made of these natural resources, and reduces waste” (8).
Interested in more?
For those motivated to read literature about other concerns about fluoride, the review below is the best summary I found in my research. It is a publication of the European Union Directorate-General for Health and Food Safety:
Closing thoughts
Ultimately, I would say that it is a personal decision as to how to use or limit fluoride. If you are interested in my personal decision, to the best of my knowledge, the benefits of the 0.7 ppm fluoride in our water outweigh the risks.
Thus, I do continue drink and cook with our fluoridated water supply and to have my children (currently ages 9 and 6 years old) drink from our fluoridated water supply as well. Everyone in my household also uses fluoridated toothpaste and gets fluoride applied to their teeth at their dental visits.
I do still plan to finish this series and add specifics on how to apply all of this information and discuss safe daily fluoride use, though there was a 5 year gap between the 1st and 2nd fluoride posts, so I make no promises on when!
References:
1. SCHER, Opinion on critical review of any new evidence on the hazard profile, health effects, and human exposure to fluoride and the fluoridating agents of drinking water. 16 May 2011. https://ec.europa.eu/health/scientific_committees/opinions_layman/fluoridation/documents/fluoridation.pdf
2. WHO 2004. Fluoride in drinking-water: Background document for development of WHO guidelines for drinking-water quality. World Health Organization, Geneva. https://www.who.int/water_sanitation_health/dwq/chemicals/fluoride.pdf
3. WHO 2010. Inadequate or excess fluoride: A major public health concern. World Health Organization, Geneva. https://www.who.int/ipcs/features/fluoride.pdf?ua=1
4. United States Environmental Protection Agency. Questions and Answers on Fluoride. 2011. https://www.epa.gov/sites/production/files/2015-10/documents/2011_fluoride_questionsanswers.pdf
5. Choi, Anna L., Guifan Sun, Ying Zhang, and Philippe Grandjean. 2012. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environmental Health Perspectives 120(10): 1362-1368.
6. O’Brien LM. Cognitive and behavioral consequences of obstructive sleep apnea. In: Sheldon SH, Ferber R, Kryger MH, Gozal D, editors. Principles & practice of pediatric sleep medicine. 2nd ed. London: Elsevier; 2014. p. 231–8.
7. Purcell PL, Shinn JR, Davis GE, Sie KC. Children with unilateral hearing loss may have lower intelligence quotient scores: A meta-analysis. Laryngoscope. 2016;126(3):746–754. doi:10.1002/lary.25524
8. Pollick, Howard F. Water fluoridation and the environment: Current perspective in the United States. Int J Occup Environ Health 2004;10:343–350. https://www.cdc.gov/fluoridation/pdf/pollick.pdf