Since my latest blog posts have met with objections that I might be cherry-picking poor examples of evidence, I have decided to be a little more thorough and go right to the source. While browsing the Fluoride Action Network (FAN) website I found their page on fluoride and IQ containing the claim that there were “24 published studies” associating high fluoride exposure and low IQ. The link to the list of studies was broken but with the help of the Wayback Machine I found the list. Out of the 25 studies and one letter to the editor listed, I have included 17 here, all from China. Five studies had to be excluded because they did not have an English translation available (though they were part of the meta-analysis written about in my last post), also one study from Iran, one study from Mexico, and one study from India were each excluded for being outside the geographical scoop of this review (though they will be included in a future post).
China does indeed have a fluoride problem, high levels in the groundwater and contamination from the use of coal for cooking and heating both contribute to exceedingly high dosages for the populations in various provinces and villages.
But as you can see here, while the Fluoride Action Network’s focus is on stopping community fluoridation programs in places such as the US, not a single study presented was actually about community fluoridation in developed nations. Rather, the studies presented by FAN are about the threat of endemic fluorosis among those exposed to high levels naturally occurring in the groundwater and from coal pollution in developing nations, issues on which they are not active. This is a disingenuous use of scientific research to advance a fear-based agenda. To demonstrate I’m going to take a look at the cited studies one by one.
#1. Research on the intellectual development of children in high fluoride areas.
Chen Y, Han F, Zhou Z, Zhang H, Jiao X, Zhang S, Huang M, Chang T, Dong Y.
This study compared two villages, one an endemic fluorosis area, Biji, and the other a control area, Jiaobei. Biji had fluoride levels in the water of 4.55 mg/L and IQ scores of 100.24±14.52 while Jiaobei had fluoride levels of 0.89 mg/L.
This is one of many examples of misusing studies done on the health dangers of high levels of naturally occurring fluoride in groundwater, exposure to industrial pollution, and occupational fluoride exposure as “evidence” against the controlled use of dental fluoride and water fluoridation programs.
#2. A preliminary investigation of the IQs of 7-13 year old children from an area with coal burning-related fluoride poisoning.
Guo X, Wang R, Cheng C, Wei W, Tang L, Wang Q, Tang D, Liu G, He G, Li S.
The title of this one says enough, the study concerned children from an area with coal burning-related fluoride poisoning. Coal related fluorosis is a real problem, but it is not related to community water fluoridation programs.
#3. Research on the effects of fluoride on child intellectual development under different environments.
Hong F, Cao Y, Yang D, Wang H.
A quote from the study explains this study,
The region of China selected for this study is a high fluoride, high iodine area in the lower reaches of the Yellow River on the flood plain near the Bohai Sea. Because the residents of the region consume drinking water that has a higher content of fluoride and iodine than the national standard, the prevalence of dental fluorosis and goiter is high.
This is explicitly not evidence of harm from community water fluoridation programs.
#4. Effects of high fluoride intake on child mental work capacity: and preliminary investigation into mechanisms involved.
Li Y, Li X, Wei S.
Once again this study was carried out on children “from a coal-burning fluorosis endemic area“. Coal burning creates airborne fluoride which can be either directly inhaled and be absorbed into foods. In most studies done on fluoride pollution from coal the levels of fluoride seen in the indoor air were fairly high. Such a study is not really relevant to regulated community water fluoridation programs.
#5. The effects of endemic fluoride poisoning on the intellectual development of children in Baotou.
Li Y, Jing X, Chen D, Lin L, Wang Z.
The title of this study is self explanatory but I’ll give a quote from the study,
The endemic fluoride poisoning in the Baotou region of Inner Mongolia is mostly concentrated on the high plateau north of the Ying Mountain Range, and the alluvial plain of the Yellow River south of Ying Mountain. As part of our endemic disease prevention work, we conducted a study of the effects of fluoride poisoning on intellectual development with the children of this region as our subjects.
This study is also on endemic fluorosis and is not relevant to the issue of community water fluoridation as stated above.
#6. Using the Raven’s standard progressive matrices to determine the effects of the level of fluoride in drinking water on the intellectual ability of school-age children.
Qin L, Huo S, Chen R, Chang Y, Zhao M.
This is another study on endemic fluoride. This study involved children from 22 villages with varying fluoride levels. An interesting finding of this study was that children with the lowest fluoride intake in the study had lower IQs than children who lived in areas with fluoride levels closer to our national standard in the US. The authors even stated, “it was discovered that both high and low fluoride had an effect on child intelligence. Fluoride levels greater than 2.0 mg/L or less than 0.2 mg/L can disrupt intellectual development.“
Among 141 children in villages with 2.1–4.0 ppm F in the drinking water, 34 (24.11%) had IQ scores in the top three categories (1–3) of intelligence; among 147 children in the villages with 0.1–0.2 ppm F, the number was 40 (27.21%), and among 159 children in villages with a “normal” 0.5–1.0 ppm F, the number was 92 (57.86%). For the lowest two IQ categories (4 and 5), the percentages were, respectively, 75.89, 72.79, and 42.14%.
Once again, this is not good evidence against community water fluoridation in developed nations.
#7. A study of the intellectual ability of 8-14 year-old children in high fluoride, low iodine areas.
Ren D, Li K, Liu D.
This study compared IQ scores of children in an area of high fluoride and low iodine with children of the same ages from an area with low iodine only. As with previous studies the levels of fluoride in question is from endemic sources and is above the recommendations here in the US. This is not good evidence against community water fluoridation. It is also interesting to note that the authors found harmful effect from low iodine intake. This is something to keep in mind when speaking about the opposition to iodized salt for which there is some overlap in the anti-fluoridation community.
#8. A study of the IQ levels of four- to seven-year-old children in high fluoride areas.
Wang G, Yang D, Jia, Wang H.
This study compared IQ scores of children in a low fluoride area (≤ 1.0 mg/L) to children in a high endemic fluoride area with fluoride levels in the water reaching as high as 8.60 mg/L (not accounting for coal contaminated air or food). IQ scores were higher among the former group and lower among the latter. This study simply does not support the hypothesis that community water fluoridation at 0.70 mg/L is harmful.
#9. The effects of endemic fluoride poisoning caused by coal burning on the physical development and intelligence of children.
Wang S, Zhang H, Fan W, Fang S, Kang P, Chen X, Yu M.
One again we have a study with a self explanatory title, the authors we investigating the effects of endemic fluoride poisoning caused by coal burning. The area studied was even described as a “heavily fluoride poisoned area”. This is not good evidence against community water fluoridation.
#10. Effect of fluoride exposure on intelligence in children.
Li XS, Zhi JL, Gao RO.
The authors of this study on endemic fluorosis state,
In the medium and severe fluorosis areas, it was customary for coal to be used as a domestic fuel for cooking, heating and drying grain whereas in the areas without or only slight fluorosis there was no custom of drying grain by the use of coal.
This is not good evidence against community water fluoridation.
#11. The relationship of a low-iodine and high-fluoride environment to subclinical cretinism in Xinjiang.
Lin FF, Aihaiti, Zhao HX, Lin J, Jiang JY, Maimaiti, and Aiken
The authors of this study state,
We studied a total of 769 schoolchildren of 7-14 years in three areas, characterized by intakes of (A) low iodine, high fluoride; (B) low iodine, normal fluoride; and (C) iodine supplemented, normal fluoride. Results for the following parameters for areas A, B, and C, respectively were: (a) average IQ: 71,77,96
Once more we are presented with a study on high levels of endemic fluoride. As with study #7, this study does not provide evidence against community fluoridation programs, but its does highlight the importance of getting enough iodine.
#12. Effect of high-fluoride water on intelligence in children.
Lu Y, Sun ZR, Wu LN, Wang X, Lu W, Liu SS.
The authors of this study on endemic fluorosis state,
The children in the high-fluoride area (drinking water fluoride 3.15 ± 0.61 mg/L [ppm]) (mean ± S.D.) had higher urinary fluoride levels (4.99 ± 2.57 mg/L) than the children in the low-fluoride area (drinking water fluoride 0.37 ± 0.04 mg/L) (urinary fluoride 1.43 ± 0.64 mg/L). The IQ of the 60 children in the high-fluoride area was significantly lower, mean 92.27 ± 20.45, than that of the 58 children in the low-fluoride area, mean 103.05 ± 13.86. More children in the high-fluoride area, 21.6%, were in the retardation (<70) or borderline (70-79) categories of IQ than children in the low fluoride area, 3.4%. An inverse relationship was also present between IQ and the urinary fluoride level.
While these results have meaning to endemic fluoride control, they are not meaningful evidence against community water fluoridation.
#13. Arsenic and fluoride exposure in drinking water: children’s IQ and growth in Shanyin County, Shanxi Province, China.
Wang SX, Wang ZH, Cheng XT, Li J, Sang Z-P, Zhang X-D, Han L-L, Qiao X-Y, Wu Z-M, Wang Z-Q.
This study is looking at the effects of high levels of arsenic (up to 190 ± 183 μg/L ) and high levels of fluoride (up to 8.3 ± 1.9 mg/L) from endemic sources. These levels are extremely high and the presence of so much arsenic is worrying. But once more, this does not support the hypothesis that community water fluoridation at 0.70 mg/L is harmful.
#14. Effect of fluoride in drinking water on children’s intelligence. (& follow up letter to the editor)
Xiang Q, Liang Y, Chen L, Wang C, Chen B, Chen X, Zhou M.
The authors of this study on endemic fluorosis state,
In the high fluoride village of Wamiao (water fluoride: 2.47±0.79 mg/L; range: 0.57–4.50 mg/L), the mean IQ of 222 children was significantly lower (92.02±13.00; range: 54–126) than in the low-fluoride village of Xinhuai (water fluoride: 0.36±0.15 mg/L; range: 0.18–0.76 mg/L), where the mean IQ of 290 children was higher (100.41±13.21; range: 60–128)…The Benchmark Concentration (BMC) for the concentration-response relationship between IQ <80 and the drinking water fluoride level was 2.32 mg/L, and the lower-bound confidence limit (BMCL) of the BMC was 1.85 mg/L. Taking dental fluorosis and other sources of dietary fluoride into account, the reference value concentration (RfC) for fluoride was calculated to be 0.925 mg/L, which is very close to the current national Chinese standard of <1.0 mg/L.
The author are stating that the Chinese fluoride standard of <1.0 mg/L is safe and this study does not provide meaningful evidence against community water fluoridation.
#15.Effect of high-fluoride water supply on children’s intelligence.
Zhao LB, Liang GH, Zhang DN, Wu XR.
The authors of this study on endemic fluorosis state,
children living in the endemic fluoride village of Sima (water supply F = 4.12 mg/L) located near Xiaoyi City had average IQ (97.69) significantly lower (p < 0.02) than children living to the north in the nonendemic village of Xinghua (F = 0.91 mg/L; average IQ = 105.21).
This study is consistent with the rest that excessively high levels of fluoride are a problem but that levels similar to those used in community fluoridation programs are safe.
#16. Research on the intellectual ability of 6-14 year old students in an area with endemic fluoride poisoning.
Hu Y, Yu Z , Ding R.
Once more we have a self explanatory title. In this study researchers look at two groups of children, one with high fluoride exposure from endemic sources (7.00 ppm) and a low fluoride area (0.8ppm or less). The authors of this study describe the impact of fluoride in this study as “negligible” however.
#17. The effects of high levels of fluoride and iodine on child intellectual ability and the metabolism of fluoride and iodine.
Yang Y, Wang X, Guo X, Hu P.
This study examined the “twin contamination zone” of Lidian Village, where the well water had an “iodine content of 1,100 μg/L and a fluoride content of 2.97 mg/L”. The control area for the study, Dading village, had drinking water with an “iodine content of 128.6 μg/L, and a fluoride content of 0.5 mg/L”. Children in Dading were found to outperform children from Lidian on the Chinese Comparative Scale of Intelligence Test (though the difference was not deemed “significant”). While relevant to the situation in some locations in China, this is not meaningful as evidence against community water fluoridation.
Once again, while the FAN’s focus is on stopping community fluoridation programs in places such as the US, not a single study presented was actually about community fluoridation in developed nations. Rather, the studies presented by FAN are about the threat of endemic fluorosis among those exposed to high levels naturally occurring in the groundwater and from coal pollution in developing nations, issues on which they are not active. This is a disingenuous use of scientific research to advance a fear-based agenda. I urge my readers to join me in supporting real, meaningful efforts to protect communities from the harms of endemic fluorosis. If you enjoyed this post please donate what you can to Frank Water and their efforts to provide sustainable water filtration to some of the worlds poorest communities.
Further Reading:
Fluoride & Heart Disease?
Fluoride & Brain Damage
Fluoride & the Brain: Déjà Vu
Fluoride & the Brain: Strike 3, You’re Out!
Science by Press Release: Fluoride & IQ