HUMAN STUDIES- Fluoride's Impact on IQ:
“We found that exposure to fluoride (F) in urine was associated with reduced Performance, Verbal, and Full IQ scores before and after adjusting for confounders. The same pattern was observed for models with F in water as the exposure variable... The individual effect of F in urine indicated that for each mg increase of F in urine a decrease of 1.7 points in Full IQ might be expected.” SOURCE: Rocha-Amador D, et al. (2007). Decreased intelligence in children and exposure to fluoride and arsenic in drinking water. Cadernos de Saude Publica 23(Suppl 4): S579-87.
"These negative correlations between IQ and urinary As and between IQ and urinary fluoride indicate that exposure to high levels of As or fluoride, or both, could affect children’s intelligence... This study indicates that exposure to fluoride in drinking water is associated with neurotoxic effects in children."
SOURCE: Wang SX, et al. (2007). Arsenic and fluoride exposure in drinking water: children's IQ and growth in Shanyin county, Shanxi province, China. Environmental Health Perspectives 115(4):643-7.
"In agreement with other studies elsewhere, these findings indicate that children drinking high F water are at risk for the impaired development of intelligence." SOURCE: Trivedi MH, et al. (2007). Effect of high fluoride water on intelligence of school children in India. Fluoride 40(3):178-183.
"Based on the findings of this study, exposure of children to high levels of fluoride may carry the risk of impaired development of intelligence." SOURCE: Seraj B, et al. (2006). [Effect of high fluoride concentration in drinking water on children’s intelligence]. Journal of Dental Medicine 19(2):80-86.
"A few epidemiologic studies of Chinese populations have reported IQ deficits in children exposed to fluoride at 2.5 to 4 mg/L in drinking water. Although the studies lacked sufficient detail for the committee to fully assess their quality and relevance to U.S. populations, the consistency of the results appears significant enough to warrant additional research on the effects of fluoride on intelligence." SOURCE: National Research Council. (2006). Fluoride in Drinking Water: A Scientific Review of EPA's Standards. National Academies Press, Washington D.C. p. 6.
"Conclusion: High fluoride burden has a definite effect on the intellectual and physical development of children." SOURCE: Wang S, et al. (2005). Effects of coal-burning related endemic fluorosis on body development and intelligence levels of children. Journal of Applied Clinical Pediatrics 20(9): 897-898.
"In our study, it was shown that the average IQ of children in a fluoride endemic area was somewhat lower than the control, but the result was not significant (P>0.05). The rate of children with “low” IQs, however, was elevated as compared to the control, and this was very statistically significant... Our study showed that, within the fluoride endemic area, the average IQ of children suffering from dental fluorosis is clearly lower than those that show no signs of the disease, and this result is very significant (P <0.01). This IQ difference of 8.12 suggests that children suffering from dental fluorosis might be particularly sensitive to excess fluoride and that the manifestation of this is not limited to the typical symptoms of fluorosis, but, more seriously, also disrupts intellectual development." SOURCE: Li Y, et al. (2003). The effects of endemic fluoride poisoning on the intellectual development of children in Baotou. Chinese Journal of Public Health Management 19(4):337-338.
“Higher drinking water fluoride levels were significantly associated with higher rates of mental retardation (IQ <70) and borderline intelligence (IQ 70-79)... In endemic fluorosis areas, drinking water fluoride levels greater than 1.0 mg/L may adversely affect the development of children's intelligence.” SOURCE: Xiang Q, et al. (2003a). Effect of fluoride in drinking water on children's intelligence. Fluoride 36: 84-94.
"As an additional part of our investigation of an association between fluoride in drinking water and children’s intelligence in two villages of Sihong County, Jiangsu Province, China, we have now determined blood lead levels of children in that study... The results show there is essentially no difference between the two villages in blood lead concentrations of the children... These results thus make it very unlikely that the differences in IQ of the children living in Wamiao and Xinhua are the result of differences in exposure to lead rather than to fluoride." SOURCE: Xiang Q, et al. (2003b). Blood lead of children in the Wamiao-Xinhuai intelligence study. Fluoride 36: 198-199.
"After controlling by significant confounders, urinary fluoride correlated positively with reaction time and inversely with the scores in visuospatial organization. IQ scores were not influenced by fluoride exposure. An increase in reaction time could affect the attention process, also the low scores in visuospatial organization could be affecting the reading and writing abilities in these children.” SOURCE: Calderon J, et al. (2000). Influence of fluoride exposure on reaction time and visuospatial organization in children. Epidemiology 11(4): S153.
"In terms of IQ ranking, the high fluoride groups showed significant deficits as compared to control (P<0.01)... Conclusion: When fluoride and iodine levels in excess of national standards for drinking water are present in the same area and ingested together, the harmful effects of fluoride are more pronounced, and the resulting damage compounded." SOURCE: Hong F, et al. (2001). A study of fluorine effects on children's intelligence development under different environments. Chinese Primary Health Care 15: 56-57.
“The IQ of the 60 children in the high-fluoride area was significantly lower than that of the 58 children in the low-fluoride area... More children in the high-fluoride area were in the retardation or borderline categories of IQ than children in the low fluoride area. An inverse relationship was also present between IQ and the urinary fluoride level. Exposure of children to high levels of fluoride may, therefore, carry the risk of impaired development of intelligence.” SOURCE: Lu Y, et al (2000). Effect of high-fluoride water on the intelligence of children. Fluoride 33:74-78.
"A study of intelligence quotient (IQ) in China was conducted using Wickler's Intelligence Quotient Table for preschool children, in 4-7-year-old children, 147 from a district with a high level of fluoride and 83 from a control area. High F intake had a significant influence on the IQ of preschool children. Operation IQ was mainly affected." SOURCE: Wang G, et al. (1996). Research on intelligence quotient of 4-7-year-old children in a district with a high level of fluoride. Endemic Diseases Bulletin 11:60-62.
"In Shanxi Province, China, children living in the endemic fluoride village of Sima located near Xiaoyi City had average IQ significantly lower than children living to the north in the nonendemic village of Xinghua.” SOURCE: Zhao LB, et al (1996). Effect of high-fluoride water supply on children's intelligence. Fluoride 29: 190-192.
“The intelligence was measured of 907 children aged 8-13 years living in areas which differed in the amount of fluoride present in the environment. The Intelligence Quotient (IQ) of children living in areas with a medium or severe prevalence of fluorosis was lower than that of children living in areas with only slight fluorosis or no fluorosis. The development of intelligence appeared to be adversely affected by fluoride in the areas with a medium or severe prevalence of fluorosis. A high fluoride intake was associated with lower intelligence.” SOURCE: Li XS. (1995). Effect of Fluoride Exposure on Intelligence in Children. Fluoride 28:189-192.
“We made an investigation in 157 children, aged 12-13, born and grew up in a coal-burning pattern endemic fluorosis area and an experiment on excessive fluoride intake in rats. The results showed: (1) Excessive fluoride intake since early childhood would reduce mental work capacity (MWC) and hair zinc content: (2) The effect on zinc metabolism was a mechanism of influence on MWC by excessive fluoride intake...” SOURCE: Li Y, et al. (1994). [Effect of excessive fluoride intake on the mental work capacity of children and a preliminary study of its mechanism] Hua Hsi I Ko Ta Hsueh Hsueh Pao. 25:188-91.
"An excess of fluoride and a lack of iodine in the same environment has been shown to have a marked effect on child intellectual development, causing a more significant intellectual deficit than lack of iodine alone. The subject group of children from the high fluoride, high iodine zone have an average IQ of 76.67±7.75, which was somewhat less than the control (IQ = 81.67 ±11.9), though the difference is not significant (P>0.05). However, the percentage of subject children in the low range (16.67%) is higher than the control, suggesting that high iodine, high fluoride environment also has a definite negative influence on child intellectual ability." SOURCE: Yang Y, et al. (1994). Effects of high iodine and high fluorine on children's intelligence and the metabolism of iodine and fluorine. Chinese Journal of Pathology 15(5):296-8.
"The results of this study show that the children living in high fluoride areas have lower IQs than the children from the non-endemic area. Also, there were many more children from the endemic area with an +-IQ score ranking of below the borderline low level as compared to the control; in the endemic area, there were 18 such subject, or 30% of the total, while in the non-endemic area there were only 7, or a rate of 11.5%. The difference between the two groups is significant. The overall distribution shows a marked difference, with the scores in the control group on average one rank higher than the control... In summary, although diminished intellectual ability can result from a multitude of factors (both innate and acquired) that influence neural development and cell division in the cerebrum, the comparison conducted in this study of two areas where the other environmental factors are basically the same shows clear differences in IQ, and it's probable that this difference is due to a high fluoride environment. It is not clear whether the underlying mechanism is fetal exposure to fluoride resulting from the poisoning of the mother or intake of fluoride after birth (in either case causing a disruption nerve cell development leading to mental deficits); this matter awaits further study." SOURCE: Guo XC, et al. (1991). A preliminary exploration of the IQ of 7-13-year-old pupils in a fluorosis area with contamination from burning coal. Chinese Journal of Endemiology 10:98-100.
"The results of this study indicate that there is a significant difference between the intellectual ability of the 7-14-year-old children from the endemic area and those of the control, and moreover that the average IQ of the children from the endemic area is clearly lower. In the endemic region, the children in the 80-89 range and below make up more than 25% of the total, while in the control range only 18% of the children fall into that range, demonstrating that high fluoride has a direct connection with the intellectual development of children." SOURCE: Chen YX, et al. (1991). Research on the intellectual development of children in high fluoride areas. Chinese Journal of Control of Endemic Diseases. 6(supplement):99-100.
“The significant differences in IQ among these regions suggests that fluoride can exacerbate central nervous lesions and somatic developmental disturbance caused by iodine deficiency. This may be in keeping with fluoride's known ability to cause degenerative changes in central nervous system cells and to inhibit the activities of many enzymes, including choline enzymes, causing disturbance of the nerve impulse.” SOURCE: Lin Fa-Fu; et al (1991). The relationship of a low-iodine and high-fluoride environment to subclinical cretinism in Xinjiang. Iodine Deficiency Disorder Newsletter Vol. 7. No. 3.
"By testing the intellectual ability of 447 elementary school students ranging in age from 9 to 10 1/2, 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." SOURCE: Qin LS, Cui SY. (1990). The influence of drinking water fluoride on pupil's IQ, as measured by Rui Wen's standards. Chinese Journal of the Control of Endemic Diseases 5:203-204.
"The effect of a harmful environment containing both high fluoride and low iodine on the development of child mental ability has yet to be reported on. To investigate this question, the authors used the Wechsler Intelligence Test to determine the IQs of a total of 329 eight- to fourteen-year-old children living in nine high fluoride, low iodine villages and seven villages that had only low levels of iodine. We discovered that the IQs of children from high fluoride, low iodine villages were clearly lower than those from the villages with low iodine alone." SOURCE: Ren Da-Li. (1989). An investigation of intelligence development of children aged 8-14 years in high-fluoride and low-iodine areas. Chinese Journal of Control of Endemic Diseases 4:251.
HUMAN STUDIES- Fluoride's Impact on the Developing Brain (Fetuses/Infants):
"The effects of excessive fluoride intake during pregnancy on neonatal neurobehavioural development and the neurodevelopment toxicity of fluoride were evaluated. Ninety-one normal neonates delivered at the department of obstetrics and gynecology in five hospitals of Zhaozhou County, Heilongjiang province, China were randomly selected from December 2002 to January 2003. The subjects were divided into two groups (high fluoride and control) based on the fluoride content in the drinking water of pregnant women. The results showed that the urinary fluoride levels of mothers from the high fluoride group were higher than those of the control group. There were significant differences in the neonatal behavioral neurological assessment score and neonatal behavioral score between the subjects in endemic areas and the control group. There were also significant differences in the non-biological visual orientation reactions and biological visual and auditory orientation reactions between the two groups. It is concluded that fluoride is toxic to neurodevelopment. Excessive fluoride intake during pregnancy can cause adverse effects on neonatal neurobehavioural development." SOURCE: Li J, Yao L, Shao Q-L. (2004). Effects of high-fluoride on neonatal neurobehavioural development. Chinese Journal of Endemiology 23:464-465.
"The levels of neurotransmitters and receptors in brain tissue of aborted fetuses from areas of endemic fluorosis were tested. The results showed that in 10 subjects from a high fluoride area ranging in age from 5 to 7 months, the levels of norepinephrine, 5-hydroxytryptamine, and α1-receptor were lower and the level of epinephrine higher as compared with levels seen in the control fetuses from a non-fluorosis endemic area; each of these results was statistically significant (P<0.05). Other monoamine neurotransmitters and metabolic products, such as dopamine, 5-hydroxy-indole acetic acid, and 3,4-dihydroxybenzoic acid showed no significant differences (P>0.05). The results suggest that the accumulation of fluoride in the brain tissue can disrupt the synthesis of certain neurotransmitters and receptors in nerve cells, leading to neural dysplasia or other damage." SOURCE: Yu Y, et al. (1996). Changes in neurotransmitters and their receptors in the human fetal brain from an endemic fluorosis area. Chinese Journal of Endemiology 15:257-259.
“Fifteen therapeutically aborted fetuses at the 5th-8th gestation month from the endemic fluorosis area were compared with those from the non-endemic area. The stereological study of the brains showed that the numerical density of the volume of the neurons and the undifferentiated neuroblasts as well as the nucleus-cytoplasm ratio of the neurons were increased. The mean volume of the neurons was reduced. The numerical density of volume, the volume density, and the surface density of the mitochondria were significantly reduced. The results showed that chronic fluorosis in the course of intrauterine fetal life may produce certain harmful effects on the developing brain of the fetus.” SOURCE: Du L. (1992). [The effect of fluorine on the developing human brain]. Chung-Hua Ping Li Hsueh Tsa Chih. 21:218-20.
"Fluoride can pass through the blood-brain barrier and accumulate in brain tissue, thus in our study, the brain tissue of the fetuses from the fluoride endemic area showed higher fluoride levels than the control. The mechanisms involved are not yet clear. Besides increased amounts of fluoride, the brain tissue of the endemic subjects also showed nerve cells with swollen mitochondria, expanded granular endoplasmic reticula, the grouping of the chromatin, damage to the nuclear envelope, a lower number of synapses, fewer mitochondria, microtubules, and vesicles within the synapses, and damage to the synaptic membrane. These changes indicate that fluoride can retard the growth and division of cells in the cerebral cortex. Fewer mitochondria, microtubules, and vesicles within the synapses could lead to fewer connections between neurons and abnormal synaptic function, influencing the intellectual development after birth. These questions await further research." SOURCE: Han H, et al. (1989). The effects of fluoride on the human fetus. Chinese Journal of Control of Endemic Diseases 4:136-138.