Abstract
|
Part 1: 87 Fluoride IQ Studies Reporting Lowered IQ (1989 – 2025) The 87 human studies listed below report an association of exposure to elevated levels of fluoride and lowered IQ. The studies are based on IQ/cognitive examinations of 32,277 children (83 studies) and 883 adults (4 studies: #s 82, 72, 21, 12). See Part 2 for a list of the 11 IQ studies reporting no effect from fluoride exposure, and one study that reported a large increase in IQ. Location of the Studies: China (51), India (18), Iran (4), Mexico (4), Canada (4), Bangladesh (1), Egypt (1), Indonesia (1), Kenya (1), Pakistan (1), Sudan (1) Sources of Fluoride Exposure in the IQ Studies: 25 Translations from Chinese to English, courtesy of the Fluoride Action Network: 20 studies published by the journal Fluoride* *The journal Fluoride is not indexed by widely used databases, such as PubMed, which is run by the U.S. National Library of Medicine at the National Institutes of Health as part of the Entrez information retrieval system. |
| # | YEAR | AUTHOR – STUDY – JOURNAL | COUNTRY | # CHILDREN |
| 87 | 2025 | Singh et al. Prenatal and childhood exposure to fluoride and cognitive development: findings from the longitudinal MINIMat cohort in rural Bangladesh. Environmental Health Perspectives |
Bangladesh |
500 5 – 10 years old |
| Results: Maternal urinary fluoride concentrations (median: 0.63 mg/L, 5th–95th percentiles: 0.26–1.41 mg/L) were inversely associated with full-scale raw scores at 5 and 10 years (B [95% confidence interval]: -2.8 [-5.1, -0.6] and -4.9 [-8.0, -1.8], respectively, by exposure doubling). In cross-sectional analysis at 10 years, child urinary fluoride (overall median: 0.66 mg/L, 5th–95th percentiles: 0.34–1.26 mg/L) above -0.47 on the log2-scale (corresponding to 0.72 mg/L) was inversely associated with full-scale raw scores (B [95% CI]: -12.1 [-21.2, -3.0]). The association at 5 years was also negative but non-significant. For both prenatal and childhood exposure, associations were most noticeable with perceptual reasoning, but also verbal scores. The estimate for the association between urinary fluoride at 10 years and perceptual reasoning became 18% lower after adjustment for prenatal exposure. Non consistent sex-specific differences were observed. Conclusion: Urinary fluoride concentrations measured prenatally and during childhood (child urinary fluoride concentrations above -0.47 on the log2 scale (corresponding to 0.72 mg/L) were associated with lower cognitive abilities, especially perceptual reasoning and verbal abilities, in Bangladeshi children. |
||||
| 86 | 2025 | Xia et al. Impact of high lodine and fluoride intake on children’s IQ in rural China. European Journal of Nutrition |
China |
711 children 8 – 12 years old |
| Results: … UF [urinary fluoride] >1.4 mg/L and UI [urinary iodine] >300 µg/L were negatively correlated with IQ scores in all school-age children (P<0.001 … Conclusions: High levels of both fluoride and iodine intake negatively affect the IQ of school-age children. Monitoring and regulating these elements in children’s diets is essential to prevent cognitive impairment. |
||||
| 85 | 2025 | Singhal et al. Correlation of fluoride intake with haemoglobin level and intelligence quotient in 8–12 year aged children: an observational study from India. BMC Public Health |
India |
300 children 8 – 12 years old |
| … did not observe a significant association between IQ and dental fluorosis or water fluoride; however, a significant association between IQ and urinary fluoride was noted after extensive evaluation of confounding factors… | ||||
| 84 | 2024 | Liu et al. The Impact of Exposure to Iodine and Fluorine in Drinking Water on Thyroid Health and Intelligence in School-Age Children: A Cross-Sectional Investigation. Nutrients |
China |
399 children 7 – 12 years old |
| Discussion: … However, what deserves more attention in this study is the combined effect of iodine and fluorine on the intelligence of school-age children. By fitting the nonlinear relationship between urine iodine, urine fluoride, and intelligence, it is found that iodine, fluorine, and intelligence evaluation scores of school-age children are indeed negatively correlated as previously assumed. Compared with other regions, the intelligence scores of respondents in areas with high water iodine and high water fluoride are lower, and more respondents are concentrated in the normal file, while the number of respondents with higher IQ is reduced. As every unit of water fluoride and water iodine increases, IQ decreases by 5.85 points, which is consistent with many previous related research conclusions [19,26,40,55,56]. Among them, the influence of fluorine exposure on school-age intelligence is mainly manifested in its threshold and saturation effect, and exposure to moderate excessive fluorine is mainly related to the loss of excellent intelligence [26] … In this study, the role of monoamine neurotransmitters in the above-mentioned influencing pathways was discussed. It has been found that DA [dopamine]-related genes may modify the association between urinary fluoride and intelligence assessment, mainly ANKK1 Taq1A, COMT Val 158 Met, and MAOA uVNTR show high-dimensional interaction with IQ [56]. DA is widely considered to be involved in the learning, memory, fluid intelligence development, and cognitive plasticity of school-age children [60,61]. Fluorine can affect the concentration of DA in the striatum and cerebellum of rats, and lead to a change in dopamine receptor expression [62]. In the model in this study, the concentration of DA in the serum of school-age children is positively correlated with the concentration of fluorine in water in non-high iodine areas. The relationship between urinary fluoride and DA is that THs [thyroid hormones] play an intermediary role in it, and it is speculated that changing the path may be a way to influence school-age children. However, unlike fluorine, the influence of iodine on the intelligence of school-age children is more complicated, and both iodine deficiency and excess may aggravate the negative effect of fluorine on intelligence [17,2] … | ||||
| 83 | 2024 | Du et al. Impaired neurogenesis induced by fluoride via the Notch1 signaling and effects of carvacrol intervention. Environmental Pollution |
China |
198 children 7 – 12 years old |
|
[Note: This is both a human and rat study] … The Notch1 signaling is crucial for neurogenesis, as it regulates the differentiation of neural stem cells (NSCs) and the connection of neurons… |
||||
| 82 | 2024 | Jin et al. A Bayesian benchmark concentration analysis for urinary fluoride and intelligence in adults in Guizhou, China. Science of The Total Environment |
China | 194 ADULTS |
| Conclusions: In conclusion, our findings indicate that intelligence scores decreased as the U-F [urinary fluoride] concentration increased in the endemic fluoride area. The results suggest that U-F can be used as an internal biomarker for monitoring the loss of public IQ caused by fluoride exposure… | ||||
| 81 | 2015 | Zhang et al. Effect of coal-burning endemic fluorosis on children’s physical development and intellectual level. Chinese Journal of Control of Endemic Diseases Translated from Chinese into English by TransPerfect, courtesy of the Fluoride Action Network |
China | 120 children |
| Methods: Ninety children with coal-burning endemic fluorosis were selected for the study, which were divided into heavy fluorosis area group, middle fluorosis area group and light disease area group. 30 children in each group. Another 30 children were selected from non-fluorosis areas as normal group. The index of physical development and intellectual level of each group were compared. Results: Dental fluorosis and urinary fluoride concentration of fluorosis area groups were higher than that of normal group (P<0.05); index of height, weight and vital capacity in normal group children’s was significantly better than that of other 3 groups (P<0.050); intelligence quotient (IQ) index in fluorosis groups was lower than that of normal group (P<0.05). Conclusion: The coal-burning endemic fluorosis may have a serious impact on children’s physical growth and intellectual level, active preventive measures should be attached to protect children’s health. |
||||
| 80 | 2021 | Zhou et al. Low-moderate fluoride exposure and intelligence among Chinese school-aged children: Role of circulating mtDNA content. Science of The Total Environment |
China |
605 children 7 – 13 years old |
| Highlights • First epidemiologic study links mtDNA [Mitochondrial DNA] content with fluoride-caused lower IQ scores. • MtDNA content was positively correlated to odds of having excellent intelligence. • MtDNA content mediated relations of fluoride to reduced odds of excellent intelligence in girls. … As shown in Table3, in the continuous analyses each 1 mg/L increase in water fluoride concentration was correlated with a 1.29-point reduction in IQ scores (95% CI: -2.05, -0.52) in all participants after adjusting for the potential confounding factors. Furthermore, we observed a decrease of 0.75 points (95% CI: -1.35, -0.15) in the IQ scores for each 1 mg/L increase in urinary fluoride concentration… We then evaluated the correlation between fluoride exposure and different grades of intelligence and found that the odds of children having excellent intelligence decreased 5% (OR = 0.95, 95% CI: 0.92, 0.98) with each 1 mg/L increase in water or urinary fluoride concentration… As shown in Table 4, we did not observe any statistically distinct correlation between mtDNA content and the children’s IQ scores. In the subgroup analyses, we analyzed the association between mtDNA content and the different intelligence levels and found that being in the highest tertile of relative mtDNA content was associated with increased odds of having excellent intelligence (OR = 1.11; 95% CI: 1.00, 1.22) compared to children in the lowest tertile (P for trend = 0.032). In addition, in the gender-stratified analyses, each 1-unit increment in the mtDNA content was associated with a statistically significant increase of 18% in the odds of having excellent intelligence in girls (OR = 1.18; 95% CI: 1.07, 1.30), but not in boys… |
||||
| 79 | 2022 | Kaur et al. Assessment of Fluoride Content in Water and Its Impact on the Intelligence Quotient of School Children Aged 12–13 Years. Cureus |
India |
90 children 12 – 13 years old |
| Materials and Methods: The IQ was measured using Raven’s Colored Progressive Matrices in 90 children, who were life-long residents in three villages (30 children each) of similar population size but differing in the level of fluoride in drinking water. Urinary fluoride concentration was measured using the selective ion electrode technique. One-way ANOVA was used for the statistical analysis of the data. Results: Children who lived in locations with fluoride levels of 1.60, 6.70, or 2.80 parts per million in their drinking water had urinary fluoride concentrations of 1.60, 6.82, or 2.69 parts per million, and IQ scores of 16.77 + 8.24, 19.36 + 9.98, or 21.87 + 7.47, respectively. Conclusion: The results indicated that there was a positive correlation between excess fluoride in drinking water and IQ. |
||||
| 78 | 2023 | Xia et al. Effects of High-Water Fluoride Exposure on IQ Levels in School-Age Children: A Cross-Sectional Study in Jiangsu, China. Exposure and Health |
China | 721 children |
| Abstract: … The HF [high fluoride] group exhibited lower average IQ scores than the CONTROL group, with a statistically significant difference among the groups (P<0.001). The proportion of individuals with Dull normal and below of IQ in the HF group was significantly higher than that in the CONTROL group (15.0 vs 3.1%), moreover in children with dental fluorosis (DF) was significantly higher than that in children without it (21.8 vs 4.4%), in children with excessive urinary fluoride (UF) was significantly higher than that in children with normal UF (16.5 vs 1.7%); these distributions were significantly different (P<0.001, P=0.048, P<0.001, respectively). Furthermore, the risk of below normal IQ in children from the HF group was significantly elevated compared to CONTROL children with a normal intelligence quotient, with an adjusted OR of 6.81 (95% confidence interval [CI]: 3.20, 14.48). Urinary fluoride (UF) was inversely linked with IQ scores, with an adjusted coefficient (B) o -4.08 (95% CI -3.04, -1.32). The coefficient of UF in the HF group was statistically different from that in the CONTROL group (P<0.001). Excessive exposure to fluorine has severe negative effects on the intellectual development of children. It is necessary to monitor children’s urinary fluoride levels and investigate other sources of fluoride intake. | ||||
| 77 | 2023 | Hall et al. Fluoride exposure and hypothyroidism in a Canadian pregnancy cohort. Science of the Total Environment |
Canada | 601 participants completed IQ testing in entirety. |
| Highlights … • Fluoride in water increased risk of hypothyroidism in pregnant women.• Boys had lower IQ scores if their mothers were hypothyroid in pregnancy.•Thyroid disruption may contribute to developmental neurotoxicity of fluoride. |
||||
| 76 | 2022 | Saeed et al. Arsenic and fluoride co-exposure through drinking water and their impacts on intelligence and oxidative stress among rural school-aged children of Lahore and Kasur districts, Pakistan. Environmental Geochemistry and Health |
Pakistan |
148 children 5 to 16 years old |
| Abstract: Arsenic (As), and fluoride (F–) are potent contaminants with established carcinogenic and non-carcinogenic impacts on the exposed populations globally. Despite elevated groundwater As and F– levels being reported from various regions of Pakistan no biomonitoring study has been reported yet to address the co-exposure impact of As and F– among school children. We aimed to investigate the effects of these two contaminants on dental fluorosis and intelligence quotient (IQ) along with the induction of oxidative stress in rural children under co-exposed conditions. A total of 148 children (5 to 16 years old) from the exposed and control group were recruited in the current study from endemic rural areas of Lahore and Kasur districts, Pakistan having elevated As and F– levels in drinking water than permissible limits. We monitored malondialdehyde and its probable association with antioxidants activity (SOD, CAT, and GR) as a biomarker of oxidative stress. GSTM1/T1 polymorphisms were measured to find the impact of As on health parameters. Mean urinary concentrations of As (2.70 vs. 0.016 µg/L, P<0.000) and F– (3.27 vs. 0.24 mg/L, P<0.000) as well as the frequency of dental fluorosis were found elevated among the exposed group. The cases of children with lower IQ were observed high in the exposed group. Additionally, lower concentrations of antioxidants (SOD, CAT, and GR) were found suggesting high susceptibility to F– toxicity. The findings suggest that F– accounted for high variations in health parameters of children under the co-exposure conditions with As. | ||||
| 75 | 2022 | Goodman. Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys’ Intelligence. Nutrients |
Canada | 366 mother–child dyads |
| Abstract: In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys’ and girls’ intelligence. We used data from 366 mother–child dyads in the Maternal–Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children’s full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: -7.67, -1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: -4.77, -1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride’s neurotoxicity in boys. | ||||
| 74 | 2022 | Feng et al. Do methylenetetrahydrofolate dehydrogenase, cyclohydrolase, and formyltetrahydrofolate synthetase 1 polymorphisms modify changes in intelligence of school-age children in areas of endemic fluorosis? Chinese Medical Journal |
China |
694 children 8 to 12 years old |
| Background: Excessive exposure to fluoride can reduce intelligence. Methylenetetrahydrofolate dehydrogenase, cyclohydrolase, and formyltetrahydrofolate synthetase 1 (MTHFD1) polymorphisms have important roles in neurodevelopment. However, the association of MTHFD1 polymorphisms with children’s intelligence changes in endemic fluorosis areas has been rarely explored. Methods: A cross-sectional study was conducted in four randomly selected primary schools in Tongxu County, Henan Province, from April to May in 2017. A total of 694 children aged 8 to 12 years were included in the study with the recruitment by the cluster sampling method. Urinary fluoride (UF) and urinary creatinine were separately determined using the fluoride ion-selective electrode and creatinine assay kit. Children were classified as the high fluoride group and control group according to the median of urinary creatinine-adjusted urinary fluoride (UFCr) level. Four loci of MTHFD1 were genotyped, and the Combined Raven’s Test was used to evaluate children’s intelligence quotient (IQ). Generalized linear model and multinomial logistic regression model were performed to analyze the associations between children’s UFCr level, MTHFD1 polymorphisms, and intelligence. The general linear model was used to explore the effects of gene-environment and gene-gene interaction on intelligence. Results: In the high fluoride group, children’s IQ scores decreased by 2.502 when the UFCr level increased by 1.0 mg/L (B = 2.502, 95% confidence interval [CI]:-4.411, -0.593), and the possibility for having “excellent” intelligence decreased by 46.3% (odds ratio = 0.537, 95% CI: 0.290, 0.994). Children with the GG genotype showed increased IQ scores than those with the AA genotype of rs11627387 locus in the high fluoride group (P< 0.05). Interactions between fluoride exposure and MTHFD1 polymorphisms on intelligence were observed (Pinteraction < 0.05). Conclusion: Our findings suggest that excessive fluoride exposure may have adverse effects on children’s intelligence, and changes in children’s intelligence may be associated with the interaction between fluoride and MTHFD1 polymorphisms. |
||||
| 73 | 2021 | Yani et al. The influence of fluoride in drinking water on the incidence of fluorosis and intelligence of elementary school students in Palu City. Gaceta Sanitaria |
Indonesia |
100 children 6–12 years old |
| Conclusions: The intelligence of children who suffered from fluorosis is lower than the intelligence of children who do not suffer from fluorosis…. The level of intelligence of students who live in the high-fluorine area is lower than students who live in low fluorine area. | ||||
| 72 | 2021 | Ren et al. The cognitive impairment and risk factors of the older people living in high fluorosis areas: DKK1 need attention. BMC Public Health |
China |
444 ADULTS over the age of 60 |
| Objective: To evaluate cognitive impairment and risk factors of elders in high fluoride drinking water areas and investigate whether DKK1 is involved in this disorder. Methods: MoCA-B and AD-8 were used to measure the cognitive functions of 272 and 172 subjects over the age of 60 came from the high and normal fluoride drinking water areas respectively, general information and peripheral blood were collected, the level of SOD, GSH and MDA were measured, mRNA level of DKK1, the concentration of blood fluoride and the polymorphism of APOE were tested. Results: The blood fluoride concentration, mRNA level of DKK1 and ratio of abnormal cognitive function of subjects in high fluorine drinking water areas were higher than those in normal areas. The level of SOD of subjects in high fluorine drinking water was low compared with those in normal areas. The level of MDA and GSH had no difference between the two crowds in different fluorine drinking water areas. There were differences in cigarette smoking, education, dental status, hypertension, hyperlipidaemia and APOE results between the two crowds in different fluorine drinking water areas. The mRNA level of DKK1 and the level of cognitive function showed a positive correlation and DKK1 was one of five risk factors involved in cognitive impairment of older people living in high fluorosis areas. Conclusions: The cognitive functions could be impaired in the older people living in high fluoride drinking water areas, and DKK1 may as a potential intervention point of this brain damage process need attention. |
||||
| 71 | 2021 | Wang et al. The cholinergic system, intelligence, and dental fluorosis in school-aged children with low-to-moderate fluoride exposure. Ecotoxicology and Environmental Safety |
China |
709 children 6.70–13 years old |
| Conclusions: … Our findings suggest low-to-moderate fluoride exposure was associated with dysfunction of cholinergic system for children. AChE may partly mediate the prevalence of DF [dental fluorosis] and lower probability of having superior and above intelligence. | ||||
| 70 | 2021 | Cantoral et al. Dietary Fluoride Intake during Pregnancy and Neurodevelopment in Toddlers: A Prospective Study in the PROGRESS Cohort. NeuroToxicology |
Mexico | 103 mother–child dyads |
| • Mexico has a salt fluoridation program. Conclusions: In this prospective cohort study, higher exposure to fluoride from food and beverage consumption in pregnancy was associated with reduced cognitive outcome, but not with language and motor outcome in male offspring over the first two years of life. |
||||
| 69 | 2021 | Yu et al. Fluoride exposure and children’s intelligence: Gene-environment interaction based on SNP-set, gene and pathway analysis, using a case-control design based on a cross-sectional study. Environment International |
China |
952 children 7 to 13 years old |
| Conclusions: Our study suggests that fluoride is inversely associated with intelligence. Moreover, the interactions of fluoride with mitochondrial function-related SNP-set, genes and pathways may also be involved in high intelligence loss. | ||||
| 68 | 2020 | Zhao et al. Fluoride exposure, dopamine relative gene polymorphism and intelligence: A cross-sectional study in China. Ecotoxicology and Environmental Safety |
China |
567 children 6–11 years old |
| Our study examined the association between excessive fluoride exposure in prenatal and childhood periods and the intelligence of school-age children. We found that prenatal excessive fluoride exposure could cause lower IQ scores, especially the decreased odds of developing excellent intelligence. Meanwhile, a negative association between fluoride exposure and children’s IQ scores was observed in children without prenatal exposure. | ||||
| 67 | 2022 | Prabhakar et al. Effect of Endemic Fluorosis on Cognitive Function of School Children in Alappuzha District, Kerala: A Cross Sectional Study. Annals of Indian Academy of Neurology |
India |
120 children 8–10 years old |
| Conclusions: [Dental] Fluorosis is associated with impaired cognition in children. There is a positive correlation between severity of dental fluorosis and the grade of cognitive impairment. | ||||
| 66 | 2020 | Lou et al. Refinement Impairments of Verbal-Performance Intelligent Quotient in Children Exposed to Fluoride Produced by Coal Burning. Biological Trace Element Research |
China |
99 children 8–12 years old |
| Conclusions: In conclusion, we believe that reducing fluoride intake with the assistance of the government can reduce fluorosis as well as the severity of intellectual impairment caused by fluorosis. Fluorosis in children can cause IQ impairment, especially the VIQ that is represented by language learning and vocabulary comprehension. | ||||
| 65 | 2019 | Till et al. Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environment International |
Canada | 398 Mother–Child dyads |
| Conclusions: In summary, fluoride intake among infants younger than 6 months may exceed the tolerable upper limits if they are fed exclusively with formula reconstituted with fluoridated tap water. After adjusting for fetal exposure, we found that fluoride exposure during infancy predicts diminished non-verbal intelligence in children… | ||||
| 64 | 2020 | Wang et al. Thyroid function, intelligence, and low-moderate fluoride exposure among Chinese school-age children. Environment International |
China |
571 children 7–13 years old |
| Conclusions: The study suggests low-moderate fluoride exposure is associated with alterations in childhood thyroid function that may modify the association between fluoride and intelligence. In the current work, results demonstrated clearly that, across the full range of water and urinary fluoride concentrations and using a measure to focus on children’s IQ scores, higher fluoride levels were associated with lower IQ scores. | ||||
| 63 | 2019 | Green et al. Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada. JAMA Pediatrics |
Canada | 601 Mother–Child dyads |
| Conclusions and Relevance: In this study, maternal exposure to higher levels of fluoride during pregnancy was associated with lower IQ scores in children aged 3 to 4 years. These findings indicate the possible need to reduce fluoride intake during pregnancy. | ||||
| 62 | 2018 | Cui et al. Dopamine receptor D2 gene polymorphism, urine fluoride, and intelligence impairment of children in China: A school-based cross-sectional study. Ecotoxicology and Environmental Safety |
China |
323 children 7 – 12 years old |
| Conclusions: Strengths of our study include using urine fluoride as an internal exposure index and thus minimizing the measurement error of exposure, adjusting up to 30 potential confounding covariates including child age and gene polymorphismin regressing IQ on urine fluoride in children… In the overall participants, by LOWESS, the IQ decreased in a roughly linear manner as the log-urine fluoride increased (Fig. 1A)… The authors also determined a safety threshold of urine fluoride on intelligence impairment in the subgroup TT as 1.73 mg/L urine fluoride with a 95% CI of (1.51 mg/L, 1.97 mg/L). | ||||
| 61 | 2019 | El Sehmawy et al. Relationship between Drinking Water Fluoride and Quotient in Egyptian School Children. Occupational Medicine & Health Affairs |
Egypt |
1,000 children 4.6 – 11 years old |
| Conclusions: In this study there’s a highly significant decrease in average IQ level in group of children with high fluoride level more than 1.5 mg /dL than the group of children with low fluoride level less than 1.5 mg /dL with the mean IQ was (96.25 ± 19.63) and (103.11 ± 28.00) for both groups respectively with p value (p<0.001), the graphical representation of the observation is shown in Figure 2. | ||||
| 60 | 2018 | Induswe et al. The Auditory Working Memory of 13-15-Year-Old Adolescents Using Water with Varying Fluoride Concentrations from Selected Public Primary Schools in North Kajiado Sub County. American Journal of Medicine and Medical Sciences |
Kenya |
269 children 13 – 15 years old
|
| Conclusions: In conclusion, low fluoride in the water seemed to enhance the AWM (Auditory Working Memory). However, the AWM declined with an increase in the fluoride concentration in water. | ||||
| 59 | 2018 | Mustafa et al. The relationship between the fluoride levels in drinking water and the schooling performance of children in rural areas of Khartoum State, Sudan. Fluoride |
Sudan |
775 children 6–14 years old |
| Results: Negative correlation coefficients were found for the average score for all the subjects and for the overall score, with the result being statistically significant in five out of the eight subjects and in the overall score (Tables 4 and 5). … significant correlations undoubtedly exist between the drinking water F level and the schooling performances in all the subjects except for one, technology, which might be due to the nature of the subject. | ||||
| 58 | 2018 | Pang et al. Relation Between Intelligence and COMT Gene Polymorphism in Children Aged 8-12 in the Endemic Fluorosis Area and Non-Endemic Fluorosis Area. Chinese Journal of Control of Endemic DiseasesTranslation from Chinese by Fluoride Action Network |
China |
402 children 8 – 12 years old |
| Conclusions: This study found that there was a great difference in the level of intelligence between children in the endemic fluorosis area and those in the non-endemic fluorosis area and such difference was statistically significant (P < 0.05)… The rate of mental retardation (IQ < 69) in children in the endemic fluorosis area was significantly higher than that in the non-endemic fluorosis area, and the difference was statistically significant (P < 0.05). | ||||
| 57 | 2017 | Chang et al. Analysis on the Effect of Coal-Burning Fluorosis on the Physical Development and Intelligence Development of Newborns Delivered by Pregnant Women with Coal-Burning Fluorosis. Chinese Journal of Control of Endemic Diseases |
China |
118 children 3, 6, 9, 12 months |
| Conclusions: Comparison of the mental development index (MDI) and psychomotor development index (PDI) (assessed using the Standardized Scale for the Intelligence Development of Children formulated by the Children Development Center of China [CDCC]) of newborns in the two groups at 3, 6, 9 and 12 months after birth showed that both the MDI and the PDI in the observation group were significantly lower than those in the control group (P< 0.05), which suggests that maternal fluorosis have a significant impact on the intelligence development of newborns. | ||||
| 56 | 2017 | Jin et al. Investigation of Intelligence Levels of Children of 8 to 12 Years of Age in Coal Burning-Related Endemic Fluorosis Areas. Journal of Environment and Health |
China |
284 children 8 – 12 years old |
| Conclusions: The intelligence of the 12-year-old group in the endemic area was lower than that of the control area, with the difference having statistical significance (Z = 3.244, P = 0.001). | ||||
| 55 | 2017 | Razdan et al. Effect of Fluoride Concentration in Drinking Water on Intelligence Quotient of 12-14-Year-Old Children in Mathura District: A Cross-Sectional Study. Journal of International Society of Preventive & Community Dentistry |
India |
219 children 12 – 14 years old |
| Conclusions: Concentration of Fluoride in the ingested water was significantly associated with the IQ of children. Outcome measures revealed that exposure to higher levels of F determined by dental fluorosis status of child inferred higher IQ deficit. | ||||
| 54 | 2018 | Yu et al. Threshold effects of moderately excessive fluoride exposure on children’s health: A potential association between dental fluorosis and loss of excellent intelligence. Environment International |
China |
2,886 children 7 – 13 years old |
| Conclusions: In conclusion, chronic exposure to excessive fluoride, even at a moderate level, was inversely associated with children’s dental health and intelligence scores, especially excellent intelligence performance, with threshold and saturation effects observed in the dose-response relationships. Additionally, DF [dental fluorosis] severity is positively associated with the loss of high intelligence, and may be useful for the identification of individuals with the loss of excellent intelligence. | ||||
| 53 | 2017 | Bashash et al. Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico. Environmental Health Perspectives |
Mexico | 299 mother–child dyads |
| Conclusions: In this study, higher prenatal fluoride exposure, in the general range of exposures reported for other general population samples of pregnant women and nonpregnant adults, was associated with lower scores on tests of cognitive function in the offspring at age 4 and 6–12 y. | ||||
| 52 | 2017 | Valdez Jiménez et al. In utero exposure to fluoride and cognitive development delay in infants. NeuroToxicology |
Mexico | 65 mother-child dyads |
| Results: In this study near to 60% of the children consumed contaminated water and the prevalence of children with IQ below 90 points was 25% in the control group (F urine 1.5 mg/g creatinine) in comparison with the 58% of children in the exposed group (F urine >5 mg/g creatinine) (OR = 4.1, CI 95% 1.3–13.2) (data unpublished)… Only 66.2% of the babies were at term… We found higher levels of F in urine across trimester in premature compared with full term 2.4 vs 1.6 mg/l (1st); 2.3 vs 1.8 mg/l (2nd); and 4.1 vs 2.8 mg/l (3rd) (data not shown). | ||||
| 51 | 2016 | Das et al. Dental fluorosis and urinary fluoride concentration as a reflection of fluoride exposure and its impact on IQ level and BMI of children of Laxmisagar, Simlapal Block of Bankura District, W.B., India. Environmental Monitoring and Assessment |
India |
149 children 6 – 18 years |
| Conclusion: …Most importantly, it was observed that due to exposure to higher fluoride concentration, children excreted higher level of F- through their urine. Therefore, it may be suggested that the status of urinary fluoride and dental fluorosis will act as good biomarkers for fluoride toxicity. Moreover, children residing in areas with higher than normal water fluoride level demonstrated more impaired development of intelligence and moderate DF [dental fluorosis]… | ||||
| 50 | 2016 | Aravind-2016. Effect of fluoridated water on intelligence in 10-12-year-old school children. Journal of International Society of Preventive & Community Dentistry |
India |
288 children 10 – 12 years old |
| Materials and Methods: Water was collected from initially identified endemic fluoride regions…and categorized on the basis of fluoride concentration into low, medium, and high-fluoride regions, i.e., Virajpet (low fluoride level < 1.2 ppm), Banavara (Medium fluoride level 1.2–2 ppm), and Mastihalli (High fluoride levels > 3 ppm). Government school from all three villages were selected randomly and IQ levels were assessed by using Raven’s Standard Progressive Matrices. This test was conducted on each child in the study sample. Results: A significant inverse relationship was found between the fluoride concentration in drinking water and IQ (r value = -0.204; P < 0.000). It was observed that IQ level was negatively correlated with fluoride concentration in drinking water. Conclusion: It is concluded that IQ level was negatively correlated with fluoride level in drinking water… |
||||
| 49 | 2015 | Mondal et al. Inferring the fluoride hydrogeochemistry and effect of consuming fluoride-contaminated drinking water on human health in some endemic areas of Birbhum district, West Bengal. Environmental Geochemistry and Health |
India |
40 children 10 – 14 years old |
| Abstract: This research work is carried out to evaluate fluoride (F) hydrogeochemistry and its effect on the population of two endemic villages of Birbhum district, West Bengal. Fluoride concentration in drinking water varies from 0.33 to 18.08 mg/L. Hydrogeochemical evolution suggests that ion-exchange mechanism is the major controlling factor for releasing F in the groundwater. Most of the groundwater samples are undersaturated with respect to calcite and fluorite. Health survey shows that out of 235 people, 142 people suffer from dental fluorosis. According to fluoride impact severity, almost 80 and 94 % people in an age group of 11–20 and 41–50 suffer from dental and skeletal fluorosis, respectively. Statistically drinking water F has a positive correlation with dental and skeletal fluorosis. Bone mineral density test reveals that 33 and 45 % of the studied population suffer from osteopenic and osteoporosis disease. IQ test also signifies that F has a bearing on the intelligence development of the study area school children. The existence of significant linear relationship (R 2 = 0.77) between drinking water F and urinary F suggests that consumption of F-contaminated drinking water has a major control over urinary F (0.39–20.1 mg/L) excretion. | ||||
| 48 | 2015 | Khan et al. Relationship between dental fluorosis and intelligence quotient of school going children in and around Lucknow district: a cross-sectional study. Journal of Clinical & Diagnostic Research |
India |
429 children 6 – 12 years old |
| Background: Fluoridation of drinking water, despite being regarded as one of the top ten public health achievements of the twentieth century, has remained a much debated concept. Various studies on animals and aborted human fetuses have confirmed that excessive fluoride intake during infancy and early childhood, causes a number of irreversible structural and functional changes in the CNS leading to memory, learning and intellectual deficits. Aim: To compare the IQ levels of school children of two different locations, having different fluoride levels in water, and to establish a relationship between fluoride levels, prevalence of fluorosis and its effect on IQ levels. Materials and Methods: A cross–sectional study was conducted among 429 children aged 6 – 12 years, selected by stratified random sampling from two different areas with different levels of fluoride in drinking water in and around Lucknow district… Results: Majority of the fluorosis free children (76.3%) had an IQ grade 2 (definitely above the average). Majority of the children suffering from very mild and mild dental fluorosis were found to have IQ grade 3 (Intellectually average). Children with moderate cases of dental fluorosis were found to have IQ grade 4 (Definitely below average). Only 5 children with severe fluorosis were included in the study and they all were found to have an IQ grade 5. Hence, a trend of increase in the IQ grade (decrease in intellectual capacity) was observed indicating a strong correlation between fluorosis grade and IQ grade. Conclusion: Findings of this study suggest that the overall IQ of the children exposed to high fluoride levels in drinking water and hence suffering from dental fluorosis were significantly lower than those of the low fluoride area. |
||||
| 47 | 2015 | Sebastian et al. A cross-sectional study to assess the intelligence quotient (IQ) of school going children aged 10-12 years in villages of Mysore district, India with different fluoride levels. Journal of the Indian Society of Pedodontics and Preventive Dentistry |
India |
405 children 10 – 12 years old |
| Aims and Objectives: This study assessed the Intelligence Quotient (IQ) of school going children aged 10-12 years in villages of Mysore district with different fluoride levels. … Results: In bivariate analysis, significant relationships were found between water fluoride levels and Intelligence Quotient of school children (P < 0.05). In the high fluoride village, the proportion of children with IQ below 90, i.e. below average IQ was larger compared to normal and low fluoride village. Age, gender, parent education level and family income had no significant association with IQ. Conclusion: School children residing in area with higher than normal water fluoride level demonstrated more impaired development of intelligence when compared to school children residing in areas with normal and low water fluoride levels. Thus, children’s intelligence can be affected by high water fluoride levels. |
||||
| 46 | 2015 | Kundu et al. Effect of fluoride in drinking water on children’s intelligence in high and low fluoride areas of Delhi. Journal of the Indian Association of Public Health Dentistry |
India |
200 children 8 – 12 years old |
| Materials and Methods: A total of 200 school children were selected, 100 from low F area and 100 from high F area… Results: Comparison of mean IQ of children in both high (76.20 ± 19.10) and low F (85.80 ± 18.85) areas showed a significant difference (P = 0.013). Multiple regression analysis between child IQ and all other independent variables revealed that mother’s diet during pregnancy (P = 0.001) along with F in drinking water (P = 0.017) were the independent variables with the greatest explanatory power for child IQ variance (r2 = 0.417) without interaction with other variables. Conclusion: Fluoride in the drinking water was significantly related with the IQ of children. Along with fluoride, mother’s diet during pregnancy was also found to be significantly related with IQ of children… |
||||
| 45 | 2015 | Choi et al. Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study. Neurotoxicology & Teratology |
China |
51 children 6 – 8 years old |
| Background: A systematic review and meta-analysis of published studies on developmental fluoride neurotoxicity support the hypothesis that exposure to elevated concentrations of fluoride in water is neurotoxic during development. Methods: We carried out a pilot study of 51 first-grade children in southern Sichuan, China, using the fluoride concentration in morning urine after an exposure-free night; fluoride in well-water source; and dental fluorosis status as indices of past fluoride exposure. We administered a battery of age-appropriate, relatively culture-independent tests that reflect different functional domains … Results: Dental score was the exposure indicator that had the strongest association with the outcome deficits, and the WISC-IV digit span subtest appeared to be the most sensitive outcome, where moderate and severe fluorosis was associated with a digit span total score difference of -4.28 (95% CI -8.22, -0.33) and backward score with -2.13 (95% CI -4.24, -0.02). Conclusions: This pilot study in a community with stable lifetime fluoride exposures supports the notion that fluoride in drinking water may produce developmental neurotoxicity, and that the dose-dependence underlying this relationship needs to be characterized in detail. … 4. Discussion: Results of our pilot study showed that moderate and severe dental fluorosis was significantly associated with deficits in WISC-IV digit span. Children with moderate or severe dental fluorosis scored significantly lower in total and backward digit span tests than those with normal or questionable fluorosis. These results suggest a deficit in working memory. Scores on other tests did not show significant relationships with indices of fluoride exposure… |
||||
| 44 | 2015 | Zhang et al. Modifying effect of COMT gene polymorphism and a predictive role for proteomics analysis in children’s intelligence in endemic fluorosis area in Tianjin, China. Toxicological Sciences |
China |
180 children 10 – 12 years old |
| Abstract: Cumulative fluoride exposure has adverse influences on children’s intelligence quotient (IQ). In addition, catechol-O-methyltransferase (COMT) gene Val158Met polymorphism (rs4680) is associated with cognitive performance. This study aimed to evaluate the associations of COMT polymorphism and alterations of protein profiles with children’s intelligence in endemic fluorosis area. We recruited 180 schoolchildren (10–12 years old) from high fluoride exposure (1.40mg/l) and control areas (0.63mg/l) in Tianjin City, China. The children’s IQ, fluoride contents in drinking water (W-F), serum (S-F), and urine (U-F); serum thyroid hormone levels, COMT Val158Met polymorphism, and plasma proteomic profiling were determined. Significant high levels of W-F, S-F, U-F, along with poor IQ scores were observed in the high fluoride exposure group compared with those in control (all P<0.05). S-F and U-F were inversely related with IQ… Importantly, higher fluoride exposure was associated with steeper cognitive decline among children with the reference allele Val compared with those homozygous or heterozygous for the variant allele Met… Additionally, 5 up-regulated protein spots related to cell immunity and metabolism were detected in children with high fluoride exposure compared with the control. In conclusion, fluoride exposure was adversely associated with children’s intelligence, whereas the COMT polymorphism may increase the susceptibility to the deficits in IQ due to fluoride exposure. Moreover, the proteomic analysis can provide certain basis for identifying the early biological markers of fluorosis among children. | ||||
| 43 | 2014 | Bai et al. Investigation and analysis of the development of intelligence levels and growth of children in areas suffering fluorine and arsenic toxicity from pollution from burning coal. Chinese Journal of Endemiology Translation of the summary courtesy of the Fluoride Action Network – see Chinese version |
China |
Children 8 – 12 years old |
| Aim: To study the impacts on the development of intelligence and growth of children suffering fluorine and arsenic toxicity from pollution from burning coal. Method: Areas suffering from significant morbidity and minor morbidity were selected for investigation from areas of southern Shaanxi Province suffering fluorine and arsenic toxicity from pollution from burning coal in 2011 and 2012. Areas not showing morbidity were selected as a control. Intelligence tests were conducted on school students 8–12 years old, and dental fluorosis and growth development were also tested… Results: The median urinary fluoride levels for children 8–12 years old in the areas of significant, minor and no morbidity were, respectively, 1.96, 0.81 and 0.54 mg/L; the median urinary arsenic levels were, respectively, 0.023, 0.019 and 0.018 mg/L. The children’s intelligence quotients were, respectively, 101.22±15.97, 104.83±12.78 and 107.92±13.62… The children’s urinary fluoride and urinary arsenic levels versus intelligence [quotients] were both negatively correlated (r=-0.560, -0.353, all P<0.05). Conclusion: Exposures to fluorine and arsenic are deleterious to the development of intelligence and the development of growth in children. We propose that stoves and furnaces be further upgraded to promote the healthy growth of children. |
||||
| 42 | 2014 | Wei et al. The effects of comprehensive control measures on intelligence of school-age children in coal-burning-borne endemic fluorosis areas. Chinese Journal of Endemiology Translation courtesy of the Fluoride Action Network |
China |
741 children 8 – 12 years old
|
| Objective: To investigate the incidence of dental fluorosis, urinary fluoride level and intelligence of children who lived in the coal-burning-borne endemic fluorosis areas and to reveal the effects of comprehensive control measures on intelligence of children in this area. Methods: Children aged 8-12 who lived in coal-burning-borne endemic fluorosis areas in Bijie City of Guizhou Province were selected and divided into two groups according to the duration of comprehensive treatments given: long treatment group (Xiaba Village and Zhongtun Village, furnace stove was changed and comprehensive control measure of health education was carried out for more than 3 years) and short treatment group (Chadi Village and Maoliping Village, stoves were improved and health education time < 1 year). The children who lived in a non-fluorosis area were selected as controls in 2012… Results: The number of children surveyed in control group was 104, long treatment group was 298, short treatment group was 339, and the incidence rates of dental fluorosis were 0 (0/104), 72.5% (216/298) and 85.2% (289/339), respectively, and the incidence rates of dental fluorosis in children lived in the endemic fluorosis areas were significantly increased compared with that of control group; the difference of incidence rates between long treatment group and short treatment group was statistically significantly (x2 =15.736,P < 0.01). Urinary fluoride content were (2.33 ± 0.18) and (3.03 ± 0.16) mg/L, respectively, compared with the control group [(1.34 ± 0.64) mg/L], the values in endemic fluorosis areas were significantly higher (F =306.53, P < 0.01). Above average IQ of children in the control group was 97.1% (101/104), which was significantly higher than that of long and short treatment groups; after a lengthy treatment, mental retardation detection rate was significantly lower in the low-age group, 8-10 year-old children (x2 =7.542, P < 0.01). Urinary fluoride content was negatively correlated with the level of IQ (r =-0.553, P < 0.01). Conclusions: The intelligence development of children in coal-burning-borne endemic fluorosis area is significantly delayed. After a certain period of comprehensive treatment, the decreased level of cognition is inhibited and the mental retardation in the low-age group is improved. |
||||
| 41 | 2013 | Nagarajappa et al. Comparative assessment of intelligence quotient among children living in high and low fluoride areas of Kutch, India: a pilot study. Iranian Journal of Public Health |
India |
100 children 8 – 10 years old |
| Methods: A cross-sectional descriptive survey was conducted among 100 school children aged 8 to 10 years, living in Kutch District, Gujarat, India during July 2012. Mundra (2.4 to 3.5 mg/L) and Bhuj (0.5mg/L) were the two villages randomly selected to represent the high and low water fluoride areas respectively… Results: Mean scores for average, shortest and total timing category were found to be significantly higher (P<0.05) among children living in Mundra (30.45±4.97) than those living in Bhuj (23.20±6.21). Mean differences at 95% confidence interval for these timings were found to be 7.24, 7.28 and 21.78 respectively. In both the villages, females had lower mean timing scores than males but the difference was not statistically significant (P>0.05). Conclusion: Chronic exposure to high levels of fluoride in water was observed to be associated with lower intelligence quotient. |
||||
| 40 | 2013 | Singh et al. A correlation between serum vitamin, acetylcholinesterase activity and IQ in children with excessive endemic fluoride exposure in Rajasthan, India. International Research Journal of Medical Sciences |
India |
73 children 9 – 14 years old |
| Abstract: … The present study was carried out among 9-14 years old school children of Dausa district, Rajasthan India. The subjects were selected from high fluoride region (>2.0 ppm) and age matched were selected from Jaipur district where fluoride content was (<1.5 ppm). A set of question was used to collect information from the children’s personal character, clinical health outcome, residential record, educational achievements and family socioeconomic status. Fluoride in serum, urine and drinking water were estimated in both subjects and controls along with serum vitamin (A, C, D and E) and acetylcholinesterase (AChE). The Raven’s Standard Progressive Matrices was used to measurement of children’s intelligence. IQ scores and serum F levels was directly correlated with the concentration of serum F level. Reduced concentration of vitamin (C, D and E) and AChE activity is the potent markers of neurodegeneration. The conclusion of the study is that the excessive fluoride delineates the neuronal impairment which were evident by reduce IQ score and serum AChE activity. Moreover, the altered vitamin concentrations which may further lead to brain and bone damage. | ||||
| 39 | 2014 | Karimzade (2014). Investigation of intelligence quotient in 9-12-year-old children exposed to high- and low-drinking water fluoride in west Azerbaijan province, Iran. Fluoride See Letter to Editor: Further information on the two villages in the study and the confounding factors considered. |
Iran |
39 children 9 – 12 years old |
| Summary: … 39 9–12-year-old children in West Azerbaijan, were selected and their IQ measured using the Iranian version of the RB Cattell test. The study cases were 19 children living in a high-drinking water F region (3.94 mg F/L), and the control group was 20 children in a low-drinking water F region (0.25 mg F/L). The results showed that, the mean IQ of children living in the high-drinking water F region was lower (81.21±16.17) than that of children in the low-drinking water F region (104.25±20.73, p=0.0004). There is a significant linear trend for children in the high-drinking water F region to have a lower IQ (p=0.0067). | ||||
| 38 | 2012 | Trivedi (2012). Assessment of groundwater quality with special reference to fluoride and its impact on IQ of schoolchildren in six villages of the Mundra Region, Kachchh, Gujarat, India. Fluoride |
India |
84 school children 6th and 7th standard |
| Abstract: … Fluoride (F) [groundwater] concentrations were higher in Chhasara, Gundala, and Mundra villages with values of 3.42, 1.8, and 1.9 mg/L (ppm), respectively. The socio-economic scale of the area was essentially low and equal, i.e., category E in a scale of A–E. Urine samples of 34 schoolchildren from high F and 50 from low F villages were collected and analyzed for F: 2.25 ppm in urine samples from villages having higher F levels in the GW [ground water], which was highly significant (p=0.01) as compared to 0.42 ppm F in the low F villages. The average IQ level of schoolchildren (N = 50) from the low F villages was 97.17, which is significantly higher (p=0.001) than 92.53 of schoolchildren (N = 34) from the high F villages. | ||||
| 37 | 2012 | Seraj et al. Effect of high water fluoride concentration on the intellectual development of children in Makoo/Iran. Journal of Dentistry (Tehran, Iran) |
Iran |
293 children 6 – 11 years old |
| Materials and Methods: In this cross-sectional study, 293 children aged 6-11 years were selected from five villages in Makoo with normal fluoride (0.8±0.3 ppm), medium fluoride (3.1±0.9 ppm) and high fluoride (5.2±1.1 ppm) in their water supplies. The IQ of each child was measured by the Raven’s test. Educational and residential information and the medical history of each child was recorded by a questionnaire completed by the parents. Data were analyzed by ANOVA test with a significance level of 0.05. Results: The mean IQ scores decreased from 97.77±18.91 for the normal fluoride group to 89.03±12.99 for the medium fluoride group and to 88.58±16.01 for the high fluoride group (P=0.001). Conclusion: Children residing in areas with higher than normal water fluoride levels demonstrated more impaired development of intelligence. Thus, children’s intelligence may be affected by high water fluoride levels. |
||||
| 36 | 2012 | Saxena et al. Effect of fluoride exposure on the intelligence of school children in Madhya Pradesh, India. Journal of Neurosciences in Rural Practice |
India |
120 children 12 years old |
| Results: Differences in participant’s sociodemographic characteristics, urinary iodine, urinary lead, and urinary arsenic levels were statistically not significant (P>0.05). However, a statistically significant difference was observed in the urinary fluoride levels (P 0.000). Reduction in intelligence was observed with an increased water fluoride level (P 0.000). The urinary fluoride level was a significant predictor for intelligence (P 0.000). Conclusion: Children in endemic areas of fluorosis are at risk for impaired development of intelligence. |
||||
| 35 | 2011 | Ding et al. The relationships between low levels of urine fluoride on children’s intelligence, dental fluorosis in endemic fluorosis areas in Hulunbuir, Inner Mongolia, China. Journal of Hazardous Materials |
China |
331 children 7 – 14 years old |
| In this survey, we investigated the effects of low fluoride exposure on children’s intelligence and dental fluorosis. 331 children aged from 7 to 14 were randomly recruited from four sites in Hulunbuir City, China. Intelligence was assessed using Combined Raven Test-The Rural in China while dental fluorosis was diagnosed with Dean’s index. Mean value of fluoride in drinking water was 1.31 ± 1.05 mg/L (range 0.24–2.84). Urine fluoride was inversely associated with IQ in the multiple linear regression model when children’s age as a covariate variable was taken into account (P < 0.0001). Each increase in 1 mg/L of urine fluoride associated with 0.59-point decrease in IQ (P = 0.0226). Meanwhile, there was a dose–response relationship between urine fluoride and dental fluorosis (P < 0.0001). In conclusion, our study suggested that low levels of fluoride exposure in drinking water had negative effects on children’s intelligence and dental health and confirmed the dose–response relationships between urine fluoride and IQ scores as well as dental fluorosis. | ||||
| 34 | 2011 | Poureslami et al. Intelligence quotient of 7 to 9 year-old children from an area with high fluoride in drinking water. Journal of Dentistry and Oral Hygiene |
Iran |
119 children 6 – 9 years old |
| In this cross sectional study, two urban communities with similar socio-economic and cultural status but with different levels of fluoride in drinking water, in Kerman province of Iran were studied: Koohbanan City (fluoride 2.38 mg/L), Baft City (fluoride 0.41 mg/L). Study samples consisted of 119 children 6 to 9 years old: 59 children from Koohbanan and 60 children from Baft… In the low fluoride area (control group), the mean IQ score of children was 97.80±15.95 that decreased to 91.37±15.63 for the high fluoride group (Koohbanan`s children), it was significantly different from the control group (P<0.05)… | ||||
| 33 | 2011 | Eswar et al. Intelligent quotients of 12-14 year old school children in a high and low fluoride village in India. Fluoride |
India |
133 children 6 – 8 years old |
| SUMMARY: The aim of this preliminary study was to compare the intelligence quotient (IQ) scores of 12–14 year old school children… In the high F village of Holesirigere the mean IQ score of the 68 children was lower (86.3±12.8) than in the low F village of Ajjihalli, where the mean IQ score of 65 children was higher (88.8±15.3), but the difference was not statistically significant (p = 0.30) The number of children with IQ scores < 90 was 43/68 (63.2%) in high F Holesirigere and 31/65(47.7%) in low F Ajjihalli, a difference that is nearly but not quite statistically significant (p = 0.06). The trend was toward lower IQ with high F water, even though these preliminary findings indicated that the F level in the drinking water was not significantly associated with IQ scores of 12–14 year old children in the high and low F villages. | ||||
| 32 | 2011 | Shivaprakash et al. Relation between dental fluorosis and intelligence quotient in school children of Bagalkot district. Journal of Indian Society of Pedodontics and Preventive Dentistry |
India |
160 children 7 – 11 years old |
| This study was conducted on 160 children, in the Bagalkot district of Karnataka state between August and October 2010, with the aim of finding out if there is a relation between dental fluorosis status and Intelligence Quotient (IQ). Children were categorized as, those suffering from dental fluorosis and those not suffering from dental fluorosis and for all children in both categories…: The mean IQ score of children without dental fluorosis was significantly higher than those children who had dental fluorosis. The mean IQ scores did not vary with the severity of dental fluorosis as classified by Dean’s fluorosis index. Also it was noticed that the percentage of children with dental fluorosis was more in Extremely Low and Low IQ categories whereas the percentage of children without dental fluorosis was more in Average and High Average IQ categories. Previous studies had indicated toward decreased Intelligence in children exposed to high levels of fluoride and our study also confirmed such an effect. | ||||
| 31 | 2009 | Sudhir et al. Effect of fluoride exposure on intelligence quotient (IQ) among 13-15 year old school children of known endemic area of fluorosis, Nalagonda District, Andhra Pradesh. Journal of the Indian Association of Public Health Dentistry |
India |
1,000 children 13 – 15 years old |
| Methodology: An analytical cross sectional study was conducted among the permanent residents of Nalgonda District of Andhra Pradesh. A total of 1000 school children aged 13-15 years were selected by stratified random sampling from four different areas with different levels of naturally occurring fluoride in drinking water. Raven’s standard progressive matrices (1992 Edition) were used for assessment of Intelligence Quotient (IQ) of children. Results: Intellectually superior (Grade I) scores for individual IQ assessment were absent in all the 4 different fluoride levels. Only 0.8% of children were present in Grade l(definitely above the average in intellectual capacity) scores except in 4th level (>4.1ppm). Number of intellectually impaired children were gradually increased with the increase in fluoride concentration in the drinking water. Conclusion: Findings of this study suggest that overall IQ levels in children exposed to high fluoride level were significantly lower than the low fluoride areas. |
||||
| 30 | 2009 | Li et al. The impact of endemic fluorosis caused by the burning of coal on the development of intelligence in children. Journal of Environment and Health Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
20 children 8 – 12 years old |
| Objective: To explore the effect of endemic fluorosis caused by coal burning on the level of intelligence in children. The Method: We randomly selected 20 school children from … slight, moderate, and severe endemic fluorosis areas that were affected by regional fluoride poisoning brought on by the burning of coal, and a controlled, non[1]endemic area… The Results: We have found that those more severely impacted by dental fluorosis had a higher level of fluoride in their urine samples (P<0.01). A significant difference in the children’s levels of IQ could be observed amongst the different disease areas. The children’s level of IQ tended to decrease as the severity of dental fluorosis increased. There was a negative correlation between the children’s IQ level and urinary fluoride content (P<0.01). Significant differences could be seen in the abilities of comparative inference, serial relationship, and abstract inference between the different groups tested (P<0.05). In terms of cognition and analogical comparison abilities, the difference was not significant among the children from the different disease groups (P>0.05). Conclusion: High exposure to fluoride most definitely has an adverse effect on the development of intelligence in children, in particular on the capability of abstract inference. |
||||
| 29 | 2007 | Rocha-Amador et al. Decreased intelligence in children and exposure to fluoride and arsenic in drinking water. Cadernos de Saúde Pública |
Mexico |
132 childen 6 – 10 years old |
| Recent evidence suggests that fluoride (F) and arsenic (As) may adversely affect intelligence quotient (IQ) scores. We explore the association between exposure to F and As in drinking water and intelligence in children. Three rural communities in Mexico with contrasting levels of F and As in drinking water were studied: Moctezuma (F 0.8±1.4mg/L; As 5.8±1.3µg/L); Salitral (F 5.3±0.9mg/L; As 169±0.9µg/L) and 5 de Febrero (F 9.4±0.9mg/L; As 194±1.3µg/L). The final study sample consisted of 132 children from 6 to 10 years old. After controlling for confounders, an inverse association was observed between F in urine and Performance, Verbal, and Full IQ scores (beta values = -13, -15.6, -16.9, respectively). Similar results were observed for F in drinking water (beta values = -6.7, -11.2, -10.2, respectively) and As in drinking water (beta values= -4.30, -6.40, -6.15, respectively). The p-values for all cases were < 0.001. A significant association was observed between As in urine and Full IQ scores (beta = -5.72, p = 0.003). These data suggest that children exposed to either F or As have increased risks of reduced IQ scores. | ||||
| 28 | 2007 | Wang et al. Arsenic and fluoride exposure in drinking water: children’s IQ and growth in Shanyin County, Shanxi Province, China. Environmental Health Perspectives |
China |
720 children 8 and 12 years old |
| Objectives: We investigated the effects of As and fluoride exposure on children’s intelligence and growth. Methods: We report the results of a study of 720 children between 8 and 12 years of age in rural villages in Shanyin county, Shanxi province, China. The children were exposed to As at concentrations of 142 ± 106 ug/L (medium-As group) and 190 ± 183 ug/L (high-As group) in drinking water compared with the control group that was exposed to low concentrations of As (2 ± 3 ug/L) and low concentrations of fluoride (0.5 ± 0.2 mg/L). A study group of children exposed to high concentrations of fluoride (8.3 ± 1.9 mg/L) but low concentrations of As (3 ± 3 ug/L) was also included because of the common occurrence of elevated concentrations of fluoride in groundwater in our study area… Results: The mean IQ scores decreased from 105 ± 15 for the control group, to 101 ± 16 for the medium-As group (p < 0.05), and to 95 ± 17 for the high-As group (p < 0.01). The mean IQ score for the high-fluoride group was 101 ± 16 and significantly different from that of the control group (p < 0.05). Children in the control group were taller than those in the high-fluoride group (p < 0.05); weighed more than the those in the high-As group (p < 0.05); and had higher lung capacity than those in the medium-As group (p < 0.05). Conclusions: Children’s intelligence and growth can be affected by high concentrations of As or fluoride. The IQ scores of the children in the high-As group were the lowest among the four groups we investigated. It is more significant that high concentrations of As affect children’s intelligence. It indicates that arsenic exposure can affect children’s intelligence and growth. |
||||
| 27 | 2007 | Trivedi et al. Effect of high fluoride water on intelligence of school children in India. Fluoride |
India |
190 children 12 – 13 years old |
| SUMMARY: The intelligence quotient (IQ) was measured in 190 school-age children, 12-13 years old, residing in two village areas of India with similar educational and socioeconomic conditions but differing in fluoride (F) concentration in the drinking water. The children in the high F area (drinking water F 5.55+0.41 mg/L) had higher urinary F levels (6.13+ 0.67 mg/L) than the children in the lower F area (drinking water F 2.01+0.09 mg/L; urinary F levels 2.30+0.28 mg/L). The mean IQ score of the 89 children in the high F area was significantly lower (91.72+1.13), than that of the 101 children in lower F area (104.44+1.23). A significant inverse relationship was also present between IQ and the urinary F level. In agreement with other studies elsewhere, these findings indicate that children drinking high F water are at risk for impaired development of intelligence. | ||||
| 26 | 2007 | Fan et al. The effect of high fluoride exposure on the level of intelligence in children. Journal of Environmental Health Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
79 children 7 – 9 years old |
| Objective: Investigate the effect of high fluoride exposure on the level of intelligence in children. Method: In May 2006, 42 children from a high endemic fluorosis group and 37 children from the control area (who have been consuming low-fluoride water after water improvement schemes) were chosen for the test. They are all from a primary school in Pucheng county, Shaanxi province. Their level of intelligence was tested, and a test for dental fluorosis was conducted using Dean’s method, and the level of fluoride in urine was determined with a fluoride ion selective method. Results: The average intelligence level of the children in the high fluoride group (96.11 + 12.00) was lower than that of the control group (98.41 + 14.75). We have not found any children with an intelligence level exceeding a level deemed as excellent; as for the intelligence distribution in these groups, there is little statistical significance. There was a negative correlation between the urine fluoride concentration and the level of intelligence in children (P>0.05). Conclusion: Exposure to high levels of fluoride is likely to cause a certain level of harm. |
||||
| 25 | 2006 | Seraj (2006). Effect of high fluoride concentration in drinking water on children’s intelligence. Journal of Dental Medicine (Tehran, Iran) 2006;19(2):80-86. |
Iran |
126 children 7 – 14 years old |
| Materials and Methods: In this cross sectional study, 41 children were selected from the high fluoride area with 2.5mg/l (ppm) fluoride in the drinking water and 85 children were selected from low fluoride area with 0.4mg/l (ppm) fluoride in the drinking water. The intelligence quotient (IQ) of each child was measured by the Raven’s test. The history of illnesses affecting the nervous system, head trauma, birth weight (>2.5kg or >2.5kg), residential history, age and sex of children were investigated by questionnaires completed by the children’s parents. Data were analyzed by Chi-Square test with p<0.05 as the limit of significance. Results: In the high fluoride area the mean IQ of children (87.9±11) was significantly lower than in the low fluoride area (98.9±12.9) (P=0.025). Conclusion: Based on the findings of this study, exposure of children to high levels of fluoride may carry the risk of impaired development of intelligence. |
||||
| 24 | 2005 original * (2008) |
Wang et al. The Effects of endemic fluoride poisoning caused by coal burning on the physical development and intelligence of children. Fluoride (2008) Study originally in Chinese in Journal of Applied Clinical Pediatrics (2005) 20(9):897-9. Translated by Julian Brooke, courtesy of the Fluoride Action Network |
China |
176 children 7 – 12 years old. |
| SUMMARY: Goal: To investigate the effects of endemic fluoride poisoning caused by coal burning on the physical development and intellectual ability of children. Method: Using random sampling from the relevant population, 176 fluorosis sufferers aged 7–12 (the subjects) were drawn from a heavily fluoride poisoned area of Zhijin County, with 50 children without dental fluorosis (the control) selected from a less severely poisoned area. The children were subjected to tests to determine levels of urinary fluoride, physical development, and intellectual ability, followed by analysis of the various measurements. Results: Compared to the control group, the fluorosis group showed retarded physical development, and the levels of urinary fluoride and intellectual ability were both lower than the control (P < 0.05 for both). Conclusion: high fluoride burden has a definite effect on the intellectual and physical development of children. |
||||
| 23 | 2003 |
Xiang-a et al. Study: Effect of fluoride in drinking water on children’s intelligence. Xiang-b et al. Addendum: Letter: Blood Lead of Children in Wamiao-Xinhuai Intelligence Study. Fluoride |
China |
512 children 8 – 13 years old |
| SUMMARY: The Intelligence Quotient (IQ) was measured in 512 children, aged 8–13 years, living in two villages in Sihong County, Jiangsu Province, China, differing in the level of fluoride in their drinking water. 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 children’s IQs were not related to urinary iodine, family income, or parent’s education level. Higher drinking water fluoride levels were significantly associated with higher rates of mental retardation (IQ <70) and borderline intelligence (IQ 70–79). 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. In endemic fluorosis areas, drinking water fluoride levels greater than 1.0 mg/L may adversely affect the development of children’s intelligence. | ||||
| 22 | 2003 original * (2008) |
Li et al. Effects of endemic fluoride poisoning on the intellectual development of children in Baotou. Fluoride (2008) |
China |
720 children
6 – 13 years old |
| Our goal was to investigate the effects of endemic fluoride poisoning on the intellectual development of children living in Baotou, Inner Mongolia. Our method was to select random child subjects from endemic fluoride areas in Baotou and use the illustrated version of the Chinese Standardized Raven Test for use with children in rural areas to test their IQ. The results showed that the average IQ of 720 children in the endemic area was 92.07 (compared to 93.78 for 236 children in the control area), with 10.38% falling into the “low” IQ category versus 4.24% in the control area. Compared with the theoretical average IQ for the Chinese children from rural areas, the average IQ of the endemic fluoride area subjects was 7.93 points lower, and the rate of underdeveloped intelligence 8% higher than the average, a very significant difference. The average IQ of children with dental fluorosis was 88.67, which was 8.12 points lower than the average for the unaffected children (96.79), and 11.69% were classified as having “low” IQ, a rate 3% higher than the children not exhibiting dental fluorosis. This indicates that children living in areas of endemic fluoride poisoning have development deficits, and that the damage to intellectual ability caused by fluoride is significant. | ||||
| 21 | 2003 | Shao et al. Initial Study of Cognitive Function Impairment as Caused by Chronic Fluorosis. Chinese Journal of Endemiology Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
49 ADULTS 30 – 50 years old |
| Objective: To investigate whether an impairment in cognitive function exists in parents diagnosed with fluoride poisoning as well as its biological basis. Methods: Individuals suffering from fluoride poisoning from a high fluorine region were selected for the study group, while healthy individuals from a non-endemic region were selected as the control group. Using specific psychological methods, the indices of blood oxidatative stress were also tested with the following: Thiobarbituric acid reaction (TBA) for Serum lipid peroxide (LPO), Ellman’s for reduced glutathione (GSH) in serum, nitrite method for superoxide dismutase (SOD) in red blood cells, and the Dithiobis-nitrobenzoic acid (DTNB) method for glutathione peroxidase (GSH-Px) in serum. As to determining the amount of NO In the subjects, this was done through testing the nitrous and nitrate (NO2/NO3-) in serum. Results: Between the study group and the control group, significant differences were observed in the data gathered from the psychological tests. Big differences were found in the tests of language fluency, recognition, similarity, associative learning, and working memory (digit span test). The total failure numbers from the psychological tests and the concentration of NO demonstrated a significant positive correlation, while the similarity test showed a significant negative correlation. SOD activity showed a significant negative correlation with the similarity and digit span tests. Conclusion: The results suggest that some cognitive function limitations exist in those suffering from chronic fluoride poisoning, and its biologic basis may be related to the levels of SOD and NO. |
||||
| 20 | 2001 | Wang et al. Effects of high iodine and high fluorine on children’s intelligence and thyroid function. Chinese Journal of Endemiology Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
322 children 8 – 12 years old |
| Results: In high iodine and high fluorine areas, the goiter rate and dental fluorosis of 8-12 years children were 29.8% and 72.98%. The children’s average intelligence quotient (IQ) was 76.67+7.75, slightly lower than comparison point, but low intelligent pupil was 16.67%. The urinary iodine and fluoride were (816.25+1.80) ug/L and (3.08+1.03) mg/L separately, clearly higher than comparison point. The thyroid iodine-131 uptake rates were visible lower. The value of 3h and 24h were respectvely (9.36+1.55)% and (9.26+4.63)%. The serum TSH level was obviously higher than comparison point. Conclusions: High iodine and high fluorine have certain influence on children’s intelligence and thyroid. |
||||
| 19 | 2001 original * (2008) |
Hong et al. Research on the effects of fluoride on child intellectual development under different environmental conditions. Fluoride (2008) |
China |
205 Children 8 – 14 years old |
| Results: In endemic areas with high fluoride and high iodine, there was greater prevalence of both fluorosis and goiter than in the areas with only one of these two factors. Although the high fluoride and high fluoride/high iodine groups showed no significant drop in average IQ compared to the control (p>0.05), in both cases this tendency was present. There was also no significant difference in IQ between the high fluoride and high fluoride/high iodine groups (p>0.05). The IQ scores of the high fluoride/low iodine and low fluoride/low iodine groups each showed significant differences compared to the control (p<0.01). With regard to average IQ, high fluoride and low iodine show significant interaction (p<0.01). In terms of IQ ranking, the high fluoride groups showed significant deficits compared to the control (p<0.01). The average IQ was also significantly linked to the educational level of the parents as well as preschool attendance(p<0.01). | ||||
| 18 | 2000 |
Lu et al. Effect of high-fluoride water on intelligence in children. Fluoride |
China |
118 children 10-12 years old |
| SUMMARY: The Intelligence Quotient (IQ) was measured in 118 children, aged 10-12 years, who were life-long residents in two villages of similar population size and social, educational and economic background but differing in the Level of fluoride in drinking water. 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. Exposure of children to high levels of fluoride may therefore carry the risk of impaired development of intelligence. | ||||
| 17 | 1998 | Zhang et al. The effect of high levels of arsenic and fluoride on the development of children’s intelligence. Chinese Journal of Public Health Translated from Chinese to English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
61 children 4 – 10 years old |
| In order to better understand the long-term effects of arsenic poisoning, fluoride poisoning and its combined poisoning, we have conducted research on the level of intelligence in children aged 4-10, who were born after water clean-up prevention schemes were put into place, and report our results as follows…. Upon analysis, there are significant differences on the levels of intelligence between the age groups of 9 and 10 years old across every observational group. In comparison, differences are not significant amongst other age groups (P>0.05). Using Q tests to perform pairing comparisons, there exists significant differences between the 9 year age group from the high arsenic high fluoride group, and their counterparts from the high fluoride group and comparative group (P<0.05), whereas there is no significant difference in the results of the high fluoride group and the comparative group (P>0.05). As for the 10-year old age bracket, there exists significant differences in the results of the high arsenic high fluoride group, the high fluoride group and the comparative group (P<0.01), whereas there is no significant difference in the results of the high arsenic high fluoride group and that of the high fluoride group (P>0.05). Discussion. Upon our research of the level of intelligence in children who were born after the water improvement schemes have been put in place, children who were born 1 year or 2 years after the improvement schemes took place have a significantly lower level of intelligence than the normal comparative group. However, results from the 9-year old age group have shown that a high level of fluoride and low level of arsenic have little effect on the subjects’ level of intelligence, whereas a high level of arsenic does affect the subject’s intellectual development. Even though there were differences in the results from the 10 year-old subjects from the normal comparative group, in contrast to subjects from the high fluoride high arsenic group and the high fluoride group, these results might not be overtly representative as less number of subjects from the high fluoride group has been tested. This might be representative, however, of the fact that a high level of arsenic was primarily responsible for the negative effect on the level of intelligence in subjects from the high arsenic high fluoride group. A potential cause for the relatively lower level of intelligence in subjects from the 9 and 10 year old age group (in comparison against those from the comparative group) could be due to the high level of arsenic contained in their parents after the water improvement schemes have been put in place. The arsenic could have travelled to the fetus’ body via the placenta, which then has taken on a negative impact on the development of the fetus’ nervous system. It could also be due to the existence of a generally higher than average level of arsenic in the area of research (despite being subjected to water clean-up schemes), which means that a higher amount of arsenic has entered the body, which then affected the development of brain tissues and resulted in the abnormal secretion of neurotransmitters in the nervous system. |
||||
| 16 | 1997 | Yao et al. Comparative Assessment of the Physical and Mental Development of Children in an Endemic Fluorosis Area with and without Water Improvement Programs. Chinese Journal of Control of Endemic Diseases Translated from Chinese to English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
1,100 children 7 – 14 years old |
| Abstract: Tests were performed to compare the IQ and physical development of 7-14-year old children from endemic fluorosis areas, with and without water improvement programs, with children from a non-fluorosis area. The results showed that the average IQ of children in each age group from the fluorosis area without water improvement is lower than those from either the fluorosis area with water improvement or the non-fluorosis area (P<0.01). When comparing 7-8-year old children born after the implementation of the water improvement program to children of the same age group in the non-fluorosis area, no obvious difference was found. Comparisons of the height, weight, and sitting height of children in the fluorosis area without water improvement and the fluorosis area with water improvement revealed an obvious difference for the 12-14-year old age group. No obvious differences were found between the fluorosis area with water improvement and the non-fluorosis area. These results show that water improvement defluoridation can improve the mental and physical development of children in a fluorosis area. | ||||
| 15 | 1996 | Yao et al. Analysis on the Correlation Between TSH and Intelligence in Children with Dental Fluorosis from Endemic Fluorosis Regions. Chinese Journal of Control of Endemic Diseases. Translated from Chinese to English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
536 children 8 – 12 years old |
|
These children are from a region impacted with endemic fluorosis: Chaoyang City of Liaoning Province. The children in the study were tested for TSH (Thyroid Stimulating Hormone) and intelligence, and meaningful results were found… 2.2 Intelligence Test Results The mean intelligence quotient of the children suffering from dental fluorosis in the two endemic areas is significantly lower than that of the children in the non-endemic area. Furthermore, subjects from the severely endemic region are found to have much lower IQ levels than their counterparts in the slightly endemic regions. (See Table 2). Half of the subjects suffering from dental fluorosis in the endemic regions were found to have IQ levels in the average and below-average range of the chart, while half of the subjects from the non-endemic and slightly endemic regions were found to have IQ levels in the average and above average range (See Table 3). From Table 3, we can see that the rate of high IQ levels (superior and excellent) from the non-endemic group is 10.74%. This is higher than the lightly endemic area group (6.91%) and the severely endemic group (3.85%). Those with lower IQ levels are dispersed on the charts in a linear fashion, where the more endemic a region, the greater the % of subjects with lower IQ… |
||||
| 14 | 1996 | Zhao et al. Effect of high-fluoride water supply on children’s intelligence. Fluoride |
China |
320 children 7 – 14 years old |
| SUMMARY: In Shanxi Province, China, children living in the endemic fluoride village of Sima (water supply F 4.12 m/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 rnm; average IQ = 105.21). These differences were not associated with gender, but the IQ scores were directly related to educational level of the parents. | ||||
| 13 | 1996 Original * (2008) |
Wang et al. A study of the IQ levels of four- to seven-year-old children in high fluoride areas. Fluoride (2008) Originally published by Endemic Diseases Bulletin (China) 1996;11(1):60-2. Translated by Julian Brooke for Fluoride Action Network. |
China |
230 children 4 – 7 years old |
|
SUMMARY: Using the Wechsler Preschool and Primary Scale of Intelligence, we conducted a study to determine the intellectual ability of 147 four- to seven-year-old preschool children in a high fluoride zone [of a rural area of Shehezi in Xinjiang Province, China] and 83 similarly-aged children from a low fluoride zone in the same region. The results show that a high fluoride intake has a clear influence on the IQ of preschool children, manifesting itself primarily as damage to performance intelligence. The study also indicates that the proportion of preschool children living in the high fluoride area that have retarded head development (based on measurement of the circumference) is significantly greater than in the low fluoride control group, and that children with this developmental deficiency demonstrate a lower IQ than children with normal head development. |
||||
| 12 | 1995 | Duan et al. A comparative analysis of the results of multiple tests in patients with chronic industrial fluorosis. Guizhou Medical Journal (China)Translated from Chinese to English by TransPerfect Translations, courtesy of Fluoride Action Network |
China |
72 ADULTS 43 – 62 years old |
|
… There have been few domestic reports on the effects of chronic industrial fluorine poisoning on the adult nervous system. In order to understand the state of higher functions of the central nervous system in patients with chronic industrial fluorosis, in November 1993 we performed X-rays, intelligence testing, fingernail fluorine content testing, electroencephalographs, and tests of nervous system symptoms and signs on workers in the electrolysis workroom at an aluminum production facility on the outskirts of Guiyang, Guizhou province, an environment in which they were exposed to fluorine, as well as control groups… It can be seen from the comparison of Group A and Group B that the longer the exposure in a high-fluorine environment, the more severe the degree of fluorine poisoning, the more obvious the decline in IQ, the greater the frequency of EEG abnormalities, and the more positive neurological signs. |
||||
| 11 | 1995 | Li et al. Effect of fluoride exposure on intelligence in children. Fluoride (2008) |
China |
907 children 8 – 13 years old |
| SUMMARY: 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 fluorosls 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 but to a minor extent only in areas with only a slight prevalence of fluorosis. A high fluoride intake was associated with a lower intelligence. No correlation was found between age and intelligence in the areas with a medium and severe prevalence of fluorosis. The effect of exposure to a high level of fluoride on intelligence may occur at an early stage of development of the embryo and infant when the differentiation of brain nerve tells is occurring and development is most rapid. | ||||
| 10 | 1994 | Xu et al. The Effect of Fluoride on the Level of Intelligence in Children. Endemic Diseases Bulletin Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
219 children 8 – 14 years old |
| Observations B: Results of IQ testing: the number of children whose level of intelligence is lower is significantly increased in regions of high fluoride/iodine regions of high fluoride only, regions of high fluoride/low iodine, against their respective comparative groups. Little difference was detected in the results of high fluoride/iodine regions where only a high amount of fluoride is detected. However, the results in these aforementioned regions in comparison against regions of high fluoride/low iodine are significantly different. This could be demonstrative of the fact that fluoride acts to increase the toxicity and worsen the occurrence of thyroid swelling. | ||||
| 9 | 1994 original * (2008) |
Li et al. Effects of high fluoride intake on child mental work capacity: Preliminary investigation into the mechanisms involved. Fluoride (2008) Originally published in the Journal of West China University of Medical Sciences (1994) Translated by Julian Brooke for Fluoride Action Network |
China |
157 children 12 – 13 years old |
| SUMMARY: A study was carried out on 157 children, age 12–13, from a coal-burning fluorosis endemic area together with an experiment looking into the effect of high fluoride intake in animals. The results showed that early, prolonged high fluoride intake causes a decrease in a child’s mental work capacity and that prolonged high uptake of fluoride causes a child’s levels of hair zinc to drop. A multifactoral correlative analysis demonstrated a direct correlation between hair zinc and mental work capacity. The decrease of 5-hydroxyindoleacetic acid and the increase of norepinephrine in animal brains exposed to high levels of fluoride suggest a possible mechanism for mental work capacity deficits in children. However, further research is necessary. | ||||
| 8 | 1994 original * (2008) |
Yang et al. The effects of high levels of fluoride and iodine on intellectual ability and the metabolism of fluoride and iodine. Fluoride (2008) Originally published in Chinese Journal of Epidemiology (1994). Translated by Julian Brooke for Fluoride Action Network |
China |
1, 518 children 8 – 14 years old |
| SUMMARY: The authors carried out a study on the intellectual abilities and fluoride/iodine metabolism of children living in a high fluoride-high iodine area. Among the results: the percentage of the general population living in this fluoride/iodine contaminated region that suffered from goiter (clinical thyroid enlargement) was 3.8%, the rate of children already showing some thyroid enlargement was 29.80%. Similarly, the rate of dental fluorosis for the general population was 35.48%, while for children it was 72.98%. Student subjects had average IQs of 76.67±7.75, with 16.67% of the IQs in the “low” category. The iodine content and fluoride content of the children’s urine were 816.25±1.80 ug/L and 2.08±1.08 mg/L, respectively, significantly higher than the control. The thyroid glands of the subjects showed a markedly lower uptake rate of iodine-131 when compared with the control, the values after 3 hr and 24 hr were 9.36±1.55% and 9.26±4.63%, respectively, and the blood serum levels of thyroid stimulating hormone (TSH) were significantly higher than the control. The results indicate that high levels of fluoride and iodine have a serious damaging effect on the body, and should be given greater attention. | ||||
| 7 | 1992 | An et al. The effects of high fluoride on the level of intelligence of primary and secondary students. Chinese Journal of Control of Endemic Diseases 7(2):93-94. Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
242 children 7 – 16 years old |
|
From Table 2, we can see that the level of intelligence of primary students from the high fluoride area and the intelligence of primary students from the secondary high fluoride area had significant differences (P<0.05), and the intelligence of students from the high fluoride area and non-endemic area are also significantly different (P<0.01). The average IQ of males was 85.8 and the average IQ of females was 81.8; there were no significant gender differences according to the statistical test. From Table 3, it can be seen that there were students at a critical state or with mental retardation in both of these two areas, but there were more in the high fluoride area than in the non-high fluoride area. There were significant differences (P<0.01) according to the Chi-square test. |
||||
| 6 | 1991 | Lin et al. The Relationship of a Low-Iodine and High Fluoride Environment to Subclinical Cretinism in Xinjiang. Endemic Disease Bulletin 6(2):62-67. Republished in Iodine Deficiency Disorder Newsletter 7(3):24-25. |
China |
769 children 7 – 14 years old |
|
… Area with high fluoride and low iodine levels (Area A) – ln the township Xinyuan in the lower reaches of Kliya river in the county of Yutian, north of the highway, we examined 250 schoolchildren, aged 7-14 years. The goiter prevalence was 91 % and dental fluorosis 20.80%. The average level of iodine in drinking water was 5.21 ug/L, and that of fluoride 0.88 mg/L. Discussion: One hundred and four children with mental retardation were detected in all. Area A had 25%, area B 16%, and area C 8%. 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 (5). We found significant differences among the three areas, indicating that lack of iodine in children results in disturbance of the process of growth and ossification and that high fluoride intake can further disturb bone development (6,7) … |
||||
| 5 | 1991 original * (2008) |
Guo et al. A preliminary investigation of the IQs of 7–13 year old children from an area with coal burning-related fluoride poisoning. Fluoride (2008) Originally published in Chinese Journal of Epidemiology (1991) Translated by Julian Brooke for Fluoride Action Network |
China |
121 children 7 – 13 years old |
| ABSTRACT: The Chinese Binet I+ Test was used to investigate the IQs of 7-13 year-old children suffering from dental fluorosis, living and attending school in an area with coal burning-related fluoride poisoning. The average IQ of these children was found to be markedly lower than in the control area, and the number of children classified as having low intelligence was significantly higher. For both groups, IQ and serum fluoride show a negative correlation (r = 0.205). | ||||
| 4 | 1991 original * (2008) |
Chen et al. Research on the intellectual development of children in high fluoride areas. Fluoride (2008) Originally published in Chinese Journal of Epidemiology (1991) Translated by Julian Brooke for Fluoride Action Network |
China |
640 children 7 – 14 years old |
| SUMMARY: As measured by the rural version of the Chinese Standardized Raven Test, the average IQ of 320 children conceived and raised in the village of Biji, Linyi County, Shanxi Province, with 4.55 mg F/L in the drinking water, was 100.24+14.52. The average IQ of the same number of children conceived and raised in the control village of Jiaobei in the same county with 0.89 mg F/L in the drinking water was significantly higher at 104+.03+14.96 (p<0.01). Higher rates of dental and skeletal fluorosis were found in Biji than in Jiaobei. Although the two villages have essentially the same cultural, occupational, health care, and life-style characteristics, higher IQs of the children were associated with higher levels of parental employment and education. | ||||
| 3 | 1991 | Sun et al. Using drawing tests to measure intelligence in children from areas impacted by combined Al-F endemic toxicosis (Shuicheng, Guizhou). Journal of Guiyang Medical College (China) Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Action Network |
China |
420 children 6.5 – 12 years old |
|
Abstract: Measurements of intelligence via drawing tests have been conducted to examine the intelligence development of children from regions affected by combined Al-F endemic toxicosis. A selected number of 196 children between 6.5 and 12 years of age participated in the testing. Across all age groups, the average IQ level of children from the endemic zones was lower than their counterparts in the non-endemic region. With the exception of the <7-year-old age-group, significant differences in intelligence were found across all age groups when comparing the results between the endemic and the non-endemic group. From these results, it can be concluded that excessive consumption of fluorine and aluminum in the early stage of development directly impacts the development of the human brain, which causes the delayed intellectual development seen in children living in the endemic areas. Discussion: …It has not been reported to date that aluminum poisoning influences children’s intelligence. However, there is a lot of research to indicate that when aluminum enters the human body, damage to the brain’s nerve cells can occur… Aluminum salt has been used worldwide, therefore, as a way to combat, remove, and purify fluoride in drinking water. This raises a question about the influence of large amounts of aluminide on the intestine’s absorption of fluoride. What exactly would be the scale or scope of this impact? Presently, research on the joint effect of fluoride and aluminide on the human body has developed rapidly in China and has drawn attention from researchers around the world. In 1987, Li Fulin Zhou Linye, et al., have found in animal experiments that fluoride and aluminide can interact with the other’s absorption into the human body. The two elements both accumulate in the body[4]. … To further investigate this issue, IQ tests have been conducted on school children living in endemic areas where high exposures to both fluoride and aluminum have been found. The area that we tested was Shuicheng, a city in Guizhou… Cichong Village examined in this study was an endemic area with high levels of fluoride and aluminum present in its environment. The local residents consistently consumed large amounts of fluorine and aluminum, as they were exposed to air and food items polluted by fuel and smoke generated from the burning of coal. Judging from this evidence, we believe that the low intelligence of children in the endemic area Is caused by the joint poisoning of fluorine and aluminum. … III. The critical period for the development of brain cells is from the 18th week of pregnancy up to 2 years of age. Children younger than 2 should therefore be prevented from being exposed to contaminants and other factors which could negatively impact the development of the brain. They should also receive enough nutrition from their daily food intake. The average IQ of children from the 8-12-year-old group in the endemic area continued to reduce as they aged, and the results were significantly different from their counterparts in the non-endemic area. This indicates that these children were experiencing various forms of intellectual disabilities. Such results are also indicative of the fact that these children were influenced by high amounts of fluorine and high aluminum while they were in the critical period of intellectual development… |
||||
| 2 | 1990 original * (2008) |
Qin et al. 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. Fluoride (2008) Originally published in Chinese Journal of Epidemiology 1990;5(4):203-4. Translated by Julian Brooke for Fluoride Action Network |
China |
447 children 9 -10.5 years old |
| SUMMARY: … 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%. The reasons for this non-monotonic pattern are not clear. | ||||
| 1 | 1989 original * (2008) |
Ren et al. A study of the intellectual ability of 8-14 year-old children in high fluoride, low iodine areas. Fluoride (2008) Originally published in the Chinese Journal of Control of Endemic Diseases 1989;4(4):251. Translated by Julian Brooke for Fluoride Action Network |
China |
329 children 8 – 14 years old |
| SUMMARY: Wechsler Intelligence Test IQ scores of 160 children, 8–14 years old, from nine schools in an area of high fluoride and low iodine averaged 64.8 compared with 85.0 (p<0.01) for 169 children of the same ages from seven schools in an area with low iodine only. Among the first group 65 (40.6%) had IQs below 60, but only 23 (13.6%) among the second group had scores this low. In each group the IQs of the boys and girls did not differ significantly. Clearly, exposure to the combination of high fluoride and low iodine was more deleterious than to low iodine alone. | ||||