In the summer of 2008, the following two reports reviewed the published studies reporting an association of high fluoride exposure and reduced IQ. The fluoride levels in water in these studies range from 0.88 – 9.4 ppm.
Connett M, Limeback H.
Fluoride and its effect on human intelligence. A systematic review.
International Association for Dental Research 83rd General Session and Exhibition. Toronto, Canada.
Poster 2205. July 4, 2008.
Tang Q-Q, Du J, Ma H-H, Jiang S-J, Zhou X-J.
Fluoride and Children’s Intelligence: A Meta-analysis.
Biol Trace Elem Res. 2008 Aug 10. 2008.
The Tang et al. study cites 16 studies, including 5 Chinese studies that had not been translated into English. FAN plans to have them translated.
The Connett & Limeback review, published prior to Tang et al., found 18 out of 20 studies reporting an association to fluoride exposure and lowered IQ. Their results are reproduced below in the following Table.
The citations for the 23 studies are listed at the end with links to the Chinese and translated versions.
The Fluoride journal published 6 of the translated Chinese studies on fluoride's impact on IQ in its April-June 2008 edition (Qin-1990, Chen-1991, Guo-1991, Liu-2000, Hong-2001, Li-2003) and will publish more translated studies in later editions.
Twelve (12) of the human/IQ studies were originally published in Chinese. Julian Brooke translated these studies into English under contract with Fluoride Action Network.
In their review of the toxicology of fluoride, the committee who authored the 2006 National Research Council of the National Academies report on fluoride (NRC), cited only 3 of the 23 studies in its 'Findings on Human Cognitive Abilities', and cited 6 of the 23 studies in its references (Yang et al., 1994; Li et al., 1995; Lin et al., 1991; Zhao et al., 1996; Lu et al., 2000; Xiang et al., 2003). 5 studies (including one untranslated Chinese study) were published after the NRC report was released. The NRC report stated:
Human Cognitive Abilities.
In assessing the potential health effects of fluoride at 2-4 mg/L, the committee found three studies of human populations exposed at those concentrations in drinking water that were useful for informing its assessment of potential neurologic effects. These studies were conducted in different areas of China, where fluoride concentrations ranged from 2.5 to 4 mg/L. Comparisons were made between the IQs of children from those populations with children exposed to lower concentration of fluoride ranging from 0.4 to 1 mg/L. The studies reported that while modal IQ scores were unchanged, the average IQ scores were lower in the more highly exposed children. This was due to fewer children in the high IQ range. While the studies lacked sufficient detail for the committee to fully assess their quality and their relevance to U.S. populations, the consistency of the collective results warrant additional research on the effects of fluoride on intelligence. Investigation of other mental and physiological alterations reported in the case study literature, including mental confusion and lethargy, should also be investigated.
Ref: bottom of page 220 to page 221
The NRC report also stated:
On the basis of information largely derived from histological, chemical, and molecular studies, it is apparent that fluorides have the ability to interfere with the functions of the brain and the body by direct and indirect means. To determine the possible adverse effects of fluoride, additional data from both the experimental and the clinical sciences are needed.
http://www.nap.edu/openbook.php?record_id=11571&page=222
| Table from Connett and Limeback 2008 review [comments in italics were not in original paper] |
Author
(Year) |
Group
compared |
Water
[F-]ppm |
n |
Urine
[F-] |
IQ test |
IQ
Results |
S.D.
+/- |
p |
Conclusion |
Hu
(1989) |
Low F
High F |
<0.70
>7.0 |
181
198 |
ND
ND |
-- |
84.9
85.15 |
NR
NR |
>0.05 |
“the effect of fluoride poisoning on intellectual ability is negligible” |
Ren
(1989) |
Low I
High F, low I |
Not
reported |
169
160 |
ND |
Wechsler |
85
64.8 |
22.3
20.4 |
<0.01 |
“Disrupted child intellectual development” is “clearly much more serious” from a “ harmful environment containing both high fluoride and low iodine …than the effects of iodine deficiency alone” |
Qin
(1990) |
Low F
Normal F
High F |
0.1-0.2
0.5-1.0
2.1-4.0 |
147
59
141 |
ND
ND
ND |
Raven |
23.03
28.14
21.17 |
NR
NR
NR |
>0.05
<0.01
|
“A child whose drinking water is above 2.0 mg/L or below 0.2 mg/L manifest intellectual deficits as compared to ‘normal’ control group.” |
Guo
(1991) |
Control
Endemic fluorosis
|
Serum F
0.10
0.15 |
61
60
|
ND
ND
|
Chinese
Binet |
83.95
77.30
|
8.93
8.52
|
(7-9 yr.)
<0.05 |
“children living in high fluoride areas have lower IQs” |
Lin
(1991) |
Low F, (Low I)
High F (high I) |
0.34 (0.96 ppb)
0.88 (5.21 ppb) |
256
250 |
1.52
2.56 |
-- |
78
71 |
NR
NR |
<0.01 |
“low iodine intake coupled with high fluoride intake exacerbates the central nervous lesions and the somatic developmental disturbance of iodine deficiency" |
| Chen (1991) |
Low F
High F |
0.89
4.55 |
320
320 |
ND
ND |
Raven |
104.03
100.24 |
14.96
14.52 |
<0.01 |
“fluoride has a direct connection with intellectual development of children” |
Yang (1994) |
Low F (Low I)
High F (high I) |
0.5 (0.13 mg/L)
2.97 (1.1 mg/L) |
416
1102 |
0.82
2.03 |
Chinese Comparative Scale of Intelli-gence Test |
81.97
76.67 |
11.97 7.75 |
>0.05 |
IQ ‘somewhat’ lower but not significant
“The average IQ scores of children in the high fluoride, high iodine area and the control area were 76.67±7.75 and 81.67±11.97 respectively. This difference is not significant, however the number of children showing moderately low IQ scores in the subject population is significantly higher than the control. See Table 2.” |
Li
(1994) |
Low F
HF I no fluorosis
HF II fluorosis
HF III flurosis |
0.3 in all water
0.5 ppm (grain)
4.7 ppm (grain)
5.3 ppm (grain)
31.6 ppm(grain) |
51
33
37
36 |
ND
ND
ND
ND
ND |
Work capacity
(reaction time, short-term memory, etc.) |
Two com-ponents of mental capacity decreased |
- |
0.05
and
<0.01 |
“early prolonged high fluoride intake causes a decrease an a child’s mental work capacity” |
Li
(1995) |
Low F
High F
|
fluorosis
low-mild
severe |
226
230
|
1.02
2.69
|
Rui Wen |
89.9
80.3
|
10.4
12.9
|
<0.01 |
High fluoride environment can adversely affect the development of intelligence in children |
| Wang (1996) |
Low F
High F |
<1.0
>1.0 – 8.6 |
83
147 |
ND
ND |
Wechsler |
101.23
95.64 |
15.84
14.34 |
<0.05 |
“high fluoride intake has a clear influence on the IQ of preschool children” |
Zhao
(1996) |
Low F
High F |
0.91
4.12 |
160
160 |
ND
ND |
Pau Wan |
105.21
97.69 |
14.99
13.00 |
<0.01 |
“The intake of high fluoride drinking water before birth had a significant deleterious influence on children’s IQ. “ |
Lu
(2000) |
Low F
High F |
0.37
3.15 |
58
60 |
1.43
4.99 |
Raven |
103.5
92.2 |
13.86
20.45 |
<0.005 |
"exposure of children to high levels of fluoride may therefore carry the risk of impaired development of intelligence” |
Hong
(2001) |
Low F
High F
High F, low I |
0.75
2.90
2.94 |
32
85
28 |
ND
ND
ND |
Raven |
82.79
80.58
68.38 |
8.98
2.28
19.12 |
>0.05
<0.01
|
F makes I-deficiency worse, lowering IQ more
than just with low I |
Li
(2003) |
Non-fluorosis
fluorosis |
ND
ND |
301
419 |
ND
ND |
Raven |
96.97
88.67 |
18.43
15.26 |
<0.01 |
Fluoride disrupts intellectual
development |
Xiang
(2003) |
Low F
High F |
0.36
2.47 |
135
155 |
1.11
3.47 |
Combined raven |
100.41
92.02 |
-- |
0.003 |
drinking water fluoride levels greater than 1.0 mg/L may adversely affect the development of children’s intelligence” |
Wang
(2005) |
Control
dental fluorosis
skeletal fluorosis |
- |
49
97
57 |
1.61
1.35 |
Raven |
percentiles
5-25 >75
4
14
24
8
12
2 |
- |
<0.01 |
“..Negative correlation between urine fluoride and intelligence”
“...The numbers of below-average IQ subjects from the two fluorosis groups were clearly higher than the control group. Further demonstrating that high fluoride intake has a damaging effect on intellectual ability. Even the control group had 16.3% of subjects in the low range, suggesting that even moderate levels of fluoride contamination such as were present in the control zone can still have a noticeable effect on the intellectual development of children.” |
Seraj
(2007) |
Low F
High F |
0.4
2.5 |
85
41 |
ND
ND |
Raven |
98.9
87.9 |
12.9
11.0 |
0.000 |
“High F may be associated with impaired development of intelligence” |
Rocha-Amador (2007) |
Low F
Mod F
High F |
0.8
5.3
9.4 |
52
20
60 |
1.5
6.0
5.5 |
Wechsler |
b values
-6.7
-11.2
-10.2 |
- |
<0.001
<0.001
<0.001 |
“Children exposed to either F or As have increased risks of reduced IQ scores” |
Trivedi
(2007) |
Low F
High F |
2.01
5.55 |
101
89 |
2.30
6.13 |
Stanford-Binet |
100.04
91.72 |
1.23
1.13 |
<0.001 |
“..the mean IQ level of students exposed to high F drinking water was significantly lower than that of the students to a lower F level drinking water” |
Wang
(2007) |
Low F
High F |
0.5
8.3 |
110
106 |
1.5
5.1 |
Raven |
105
101 |
15
16 |
<0.05 |
“Children’s intelligence and growth can be affected by high concentrations of As or fluoride.” |
The 23 studies reporting an association between fluoride exposure and reduced IQ:
9 CHINESE LANGUAGE STUDIES:
(1)
Chen Y, Han F, Zhou Z, Zhang H, Jiao X, Zhang S, Huang M, Chang T, Dong Y. (2008)
Research on the intellectual development of children in high fluoride areas.
Chinese Journal of Control of Endemic Diseases 1991;6 Suppl:99-100. 1991.
English version published in Fluoride 41(2):120–124. April-June 2008.
Translated by Julian Brooke and published with the concurrence of the Chinese Journal of Control of Endemic Diseases.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
(2)
Guo
X, Wang R, Cheng C, Wei W, Tang L, Wang Q, Tang D, Liu G, He G, Li S. (2008)
A preliminary investigation of the IQs of 7-13 year old children from an area with coal burning-related fluoride poisoning.
Chinese Journal of Endemiology 1991;10(2):98-100. 1991.
English version published in Fluoride 41(2):125–128. April-June 2008.
Translated by Julian Brooke and published with the concurrence of the Chinese Journal of Endemiology.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
(3)
Hong F, Cao Y, Yang D, Wang H. (2008)
Research on the effects of fluoride on child intellectual development under different environments.
Chinese Primary Health Care 2001;15(3):56-7.
2001.
Translated by Julian Brooke and published with the concurrence of Chinese Primary Health Care.
English version published in Fluoride 41(2):156–160. April-June 2008.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
(4)
Li Y, Li X, Wei S. (2008)
Effects of high fluoride intake on child mental work capacity: and preliminary investigation into mechanisms involved.
The Journal of West China University of Medical Sciences 1994: 25(2): 188-191. 1994.
English version published in Fluoride 41(4):331-335. October-December.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
(5)
Li Y, Jing X, Chen D, Lin L, Wang Z. (2008)
The effects of endemic fluoride poisoning on the intellectual development of children in Baotou.
Chinese Journal of Public Health Management 2003:19(4):337-8. 2003.
Translated by Julian Brooke and published with the concurrence of the Chinese Journal of Public Health Management.
English version published in Fluoride 41(2):161–164. April-June 2008.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
(6)
Qin L, Huo S, Chen R, Chang Y, Zhao M. (1990)
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.
Chinese Journal of the Control of Endemic Diseases 5:203-204.
Translated by Julian Brooke and published with the concurrence of the Chinese Journal of Control of Endemic Diseases.
English version published by Fluoride 41(2):115–119. April-June 2008.
• NRC did not have this study for review.
• Translation into English paid for by Fluoride Action Network.
• Chinese version.
(7)
Ren D, Li K, Liu D. (2008)
A study of the intellectual ability of 8-14 year-old children in high fluoride, low iodine areas.
Chinese Journal of Control of Endemic Diseases Vol. 4, No. 4, p 251. 1989.
English version publised by Fluoride 41(4):319-320. October-December.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
* Chinese version.
(8)
Wang G, Yang D, Jia, Wang H. (2008)
A study of the IQ levels of four- to seven-year-old children in high fluoride areas.
Endemic Diseases Bulletin, Vol. 11, No. 1, 60-6. February 1996.
English version published by Fluoride 41(4)340–343. October-December.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
(9)
Wang S, Zhang H, Fan W, Fang S, Kang P, Chen X, Yu M. (2008)
The effects of endemic fluoride poisoning caused by coal burning on the physical development and intelligence of children.
Journal of Applied Clinical Pediatrics 20(9): 897-898. September 2005.
English version published in Fluoride 412(4)344-348. October-December.
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
8 STUDIES IN ENGLISH:
(10)
Li XS, Zhi JL, Gao RO. (1995)
Effect of fluoride exposure on intelligence in children.
Fluoride 28(4): 189-192. 1995.
• NRC cited this study in its references.
(11)
Lin FF, Aihaiti, Zhao HX, Lin J, Jiang JY, Maimaiti, and Aiken (1991)
The relationship of a low-iodine and high-fluoride environment to subclinical cretinism in Xinjiang.
Xinjiang Institute for Endemic Disease Control and Research;
Office of Leading Group for Endemic Disease Control of Hetian Prefectural Commitlee of the Communist Party of China; and County Health and Epidemic Prevention Station, Yutian, Xinjiang.
• NRC cited this study in its references.
(12)
Lu Y, Sun ZR, Wu LN, Wang X, Lu W, Liu SS. (2000)
Effect of high-fluoride water on intelligence in children.
Fluoride 33(2): 74-78. 2000.
• NRC cited this study in its references.
(13)
Rocha-Amador D, Navarro ME, Carrizales L, Morales R, Calderón J. (2007)
Decreased intelligence in children and exposure to fluoride and arsenic in drinking water.
Cad. Saúde Pública, Rio de Janeiro, 23 Sup 4:S579-S587. 2007.
• NRC did not have this study for review.
(14)
Trivedi MH, Verma RJ, Chinoy NJ, Patel RS, Sathawara NG . (2007)
Effect of high fluoride water on intelligence of school children in India.
Fluoride 40(3):178–183. July-September. 2007.
• NRC did not have this study for review.
(15)
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. (2007)
Arsenic and fluoride exposure in drinking water: children’s IQ and growth in Shanyin County, Shanxi Province, China.
Environmental Health Perspectives115(4):643-647. April 2007.
• NRC did not have this study for review.
(16)
Xiang Q, Liang Y, Chen L, Wang C, Chen B, Chen X, Zhou M. (2003)
Effect of fluoride in drinking water on children's intelligence.
Fluoride 36(2): 84-94. 2003.
• NRC cited this study in its references.
(17)
Zhao LB, Liang GH, Zhang DN, Wu XR. (1996)
Effect of high-fluoride water supply on children's intelligence.
Fluoride 29(4): 190-192. 1996.
• NRC cited this study in its references.
1 STUDY IN PERSIAN
(18)
Seraj B*, Shahrabi M, Falahzade M, Falahzade F, Akhondi N. (2007)
Effect of high fluoride concentration in drinking water on children's intelligence.
• English translation forwarded by lead author: (B. Seraj, Department of Pediatric Dentistry, Faculty of Dentistry,Tehran University of Medical Sciences)
Journal of Dental Medicine 19(2):80-86. 2007.
• NRC did not have this study for review.
• Persian version
5 CHINESE STUDIES NOT YET TRANSLATED INTO ENGLISH:
The Tang et.al. study cited the following 5 studies as reporting lowered IQ from fluoride exposure.
(FAN intends to translate these papers into English.)
(19)
Title: Effect of high level of fluoride on children’s intelligence.
Authors: An JA, Mei SZ, Liu AP et al.
Published in: Zhong Guo Di Fang Bing Fang Zhi Za Zhi 7(2):93–94. 1992. (in Chinese)
(20)
Title: Effect of fluoride on children’s intelligence.
Authors: Xu YL, Lu CS, Zhang XN
Published in:
Di Fang Bing Tong Bao 9:83–84. 1994. (in Chinese)
(21)
Title: Comparison of children’s health and intelligence between the fluorosis area with altering water source and those without altering water source.
Authors: Yao LM, Deng Y, Yang SY et al (1997) Yu Fang Yi Xue Wen
Published in: Yu Fang Yi Xue Wen Xian Xin Xi 3(1):42–43. 1997. (in Chinese)
(22)
Title: Effect of high level of fluoride and arsenium on children’s intelligence.
Authors: Zhang JW, Yao H, Chen Y.
Zhong Guo Gong Gong Wei Sheng Xue Bao 17(2):119. 1998. (in Chinese)
(23)
Title: Effect of high fluoride exposure on children intelligence.
Authors: Fan ZX, Dai HX, Bai AM et al.
Published by: Huan Jing Yu Jian Kang Za Zhi 24(10):802–803. 2007. (in Chinese)
2 CHINESE STUDIES that Connett & Limeback did not list as finding an association between fluoride exposure and reduced IQ:
Hu
Y, Yu Z , Ding R. (1989)
Research on the intellectual ability of 6-14 year old students in an area with endemic fluoride poisoning.
Collection of papers and abstracts of 4th China Fluoride Research Association 6:73. 1989.
• Translation into English by Julian Brooke. (English translation not yet published)
• NRC did not have this study for review.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
Yang Y, Wang X, Guo X, Hu P. (1994)
The effects of high levels of fluoride and iodine on child intellectual ability and the metabolism of fluoride and iodine.
Chinese Journal of Epidemiology 15(4). October 1994.
• Translation into English by Julian Brooke. (English translation not yet published)
• NRC cited this study in its references.
• Translation into English paid by Fluoride Action Network.
• Chinese version.
• FAN note: The paper states, “The average IQ scores of children in the high fluoride, high iodine area and the control area were 76.67±7.75 and 81.67±11.97 respectively. This difference is not significant, however the number of children showing moderately low IQ scores in the subject population is significantly higher than the control. See Table 2.”
... In humans, only five substances have so far been documented as developmental neurotoxicants: lead, methylmercury, polychlorinated biphenyls, arsenic, and toluene. From this evidence, including our own studies on some of these substances, parallels may be drawn that suggest that fluoride could well belong to the same class of toxicants, but uncertainties remain. At least 200 industrial chemicals are known to cause brain toxicity in humans, mainly adults, and they must also be suspected to harm the developing brain. Because of the individual and societal importance of optimal brain function, recognition of developmental neurotoxicity is a public health priority, and further evidence on fluoride is needed.
Potentials for Developmental Fluoride Neurotoxicity by Anna L. Choi and Phillippe Grandjean
XXVIITH Conference of the International Society for Fluoride Research, October 9-12, 2007, Beijing China |
