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FLUORIDE & IQ: THE 64 STUDIES
As of December 2019, a total of 72 studies
have investigated the relationship between fluoride and human intelligence. Of
these investigations, 64 studies have found that elevated fluoride exposure is
associated with reduced IQ in humans, while over 60 animal studies have found that fluoride
exposure impairs the learning and/or memory capacity of animals. The human
studies, which are based on IQ examinations of 23,773 children (62 studies) and 245 adults (2 studies), provide compelling evidence that
fluoride exposure during the early years of life can damage a child’s
developing brain. For a discussion of the 8 studies that did not find an association
between fluoride and IQ, click here.
STUDIES FINDING ASSOCIATION
BETWEEN FLUORIDE & REDUCED IQ:
IQ Study #64 (Till 2019) |
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Citation:
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Till C, Green R, Flora D, Hornung R, Martinez-Miller EA, Blazer
M, Farmus L, Ayotte P, Muckle G, Lanphear B. (2019). Fluoride
exposue from infant formula and child IQ in a Canadian birth cohort. Environment
International 134:105315.
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Location of Study:
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In fluoridated and non-fluoridated cities in Canada.
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Size of Study:
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398 mother-child pairs
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Age of Subjects:
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Fetus and Infants up to 3-4 year-olds
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Source of Fluoride:
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Fluoride in drinking water for (1) Fetal fluoride exposure and
(2) breast-fed versus formula-fed from both fluoridated and non-fluoridated
cities.
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Water Fluoride Level:
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Thirty-eight percent of mother-child pairs lived in
fluoridated communities, with the optimal fluoride level of 0.7 mg/L.
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Urinary fluoride
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The authors “used maternal urinary fluoride (MUF) adjusted for
specific gravity as a proxy of fetal fluoride exposure. MUF, which was
derived by averaging three spot samples collected across all three trimesters
of pregnancy”.
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Type of IQ Test:
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Wechsler Primary and Preschool Scale of Intelligence-III at
3–4 years.
Outcomes included Full Scale IQ (FSIQ), a measure of global intellectual functioning, Verbal IQ (VIQ), a measure of verbal reasoning, and Performance IQ (PIQ), a measure of non-verbal reasoning and visual-motor coordination skills. |
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Results:
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Thirty-eight percent of mother-child dyads [pairs] lived in
fluoridated communities. An increase of 0.5 mg/L in water fluoride
concentration (approximately equaling the difference between fluoridated and
non-fluoridated regions) corresponded to a 9.3- and 6.2-point decrement in
Performance IQ among formula-fed (95% CI: -13.77, -4.76) and breast-fed
children (95% CI: -10.45, -1.94). The association between water fluoride concentration
and Performance IQ remained significant after controlling for fetal fluoride
exposure among formula-fed (B = -7.93,
95% CI: -12.84, -3.01) and breastfed children (B = -6.30,
95% CI: -10.92, -1.68). A 0.5 mg increase in fluoride intake from infant
formula corresponded to an 8.8-point decrement in Performance IQ (95% CI:
-14.18, -3.34) and this association remained significant after controlling
for fetal fluoride exposure (B = -7.62,
95% CI: -13.64, -1.60).
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Conclusions:
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In summary, fluoride intake among infants younger than 6
months may exceed the tolerable upper limits if they are fed exclusively with
formula reconstitued with fluoridated tap water. After adjusting for fetal
exposure, we found that fluoride exposure during infancy predicts diminished
non-verbal intelligence in children. In the absence of any benefit from
fluoride consumption in the first six months, it is prudent to limit fluoride
exposure by using non-fluoridated water or water with lower fluoride content
as a formula diluent.
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Funding for Study:
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This study was funded by a grant from the U.S. National
Institute of Environmental Health Sciences (NIEHS) (grant #R21ES027044).
The MIREC Study [from which the women were chosen] was supported by the Chemicals Management Plan at Health Canada, the Ontario Ministry of the Environment, and the Canadian Institutes for Health Research (grant #MOP-81285). |
IQ Study #63 (Wang 2019) |
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Citation:
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Wang M, Liu L, Li H, LI Y, Liu H, Hou C, Zeng Q, Li P, Zhao Q,
Dong L, Zhou G, Yu X, Liu L, Guan Q, Zhang S, Wang A.(2019). Thyroid
function, intelligence, and low-moderate fluoride exposure among Chinese
school-age children. Environment
International 134:105229. [Epub ahead of
print].
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Location of Study:
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From endemic and non-endemic fluorosis areas in Tianjin,
China.
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Size of Study:
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571 children randomly selected from endemic and non-endemic
fluorosis areas in Tianjin. Children who were not long- term residents of the
area were eliminated. Further, children who had congenital or acquired
diseases affecting intelligence, or a history of cerebral trauma and
neurological disorders, or those with a positive screening test history (like
hepatitis B virus infection, Treponema palladium infection and Down’s
syndrome) and adverse exposures (smoking and drinking) during maternal
pregnancy were excluded from the analyses.
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Age of Subjects:
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7–13 years
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Source of Fluoride:
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Drinking water
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Water Fluoride Level:
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About half of the children are in the district where water
fluoride concentrations were within the Standards for Drinking Water Quality
in China of 1 mg/L, while the other half had significantly higher fluoride
concentrations than the screening guideline of 1 mg/L. The water fluoride
concentration ranged from 0.20 mg/L to 3.9 mg/L, with a mean value of 1.39 ±
1.01 mg/L.
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Urinary fluoride levels:
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The mean (±SD) urinary fluoride was 1.28 ± 1.3 mg/L, with the
range from 0.01 mg/L to 5.54 mg/L.
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Thyroid hormone levels
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The median THs levels in the serum were 1.33 ng/mL for TT3, 6.8 g/dL for TT4, 3.28 pg/mL for FT3, 1.12 ng/dL for FT4, and 2.28 uIU/mL for
TSH.
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Type of IQ Test:
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A Combined Raven’s Test for Rural China (CRT-RC2) was taken to
evaluate the IQ of each child. Additionally, we utilized logistic regression
model to examine the associations between fluoride, THs (Thyroid hormones)
and different levels of intelligence, in which the IQ scores were categorized
into five degrees as follows: marginal (70–89), normal (90–109), high normal
(110–119), superior (120–129) and excellent (130), and the normal group was
assigned as the control. Moreover, multivariate linear regression models were
constructed to assess the associations between quartiles of water fluoride or
urinary fluoride and THs and IQ scores, as well as associations between
quartiles of THs and IQ scores. Trends tests were assessed by using the
median value in each quartile as a continuous variable in the linear
regression models
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Results:
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Fluoride exposure was inversely related to
IQ scores for water fluoride and for urinary fluoride. The study detected a
significant modification effect by TSH on the association between urinary
fluoride and IQ scores, without mediation by THs.
Adjusted estimates
(95% CI) for the associations between fluoride exposure
and IQ scores were a decrease of 1.587) points (95% CI: 2.607,
0.568, P= 0.002) and 1.214 points (95% CI: 1.987,
0.442), P = 0.002)
in every 1mg/L increase of water and urinary fluoride concentration,
respectively (Table 4). The similar relationship between IQ scores and
fluoride exposure were observed in boys and girls, respectively. However, the
modification effects by gender were not significant (Table 4).
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Conclusions:
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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.
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Funding for Study:
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This work was supported by grants from the State Key Program
of National Natural Science of China (Grant No. 81430076), the National
Natural Science Foundation of China (Grants No. 81502785 and No. 81773388)
and the Fundamental Research Funds for the Central Universities (HUST
2016YXMS221 and HUST 2015ZDTD052).
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IQ Study #62 (Green-2019) |
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Citation:
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Green R, Lanphear B, Hornung R, Flora D, Martinez-Mier
EA, Neufeld R, Ayotte P, Muckle G, Till C. (2019). Association
Between Maternal Fluoride ExposureDuring Pregnancy and IQ Scores in Offspring
in Canada. JAMA Pediatrics. Published August 19.
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Location of Study:
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CANADA. 6 major cities.
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Size of Study:
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512 mother-child pairs
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Age of Subjects:
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Between the ages 3 and 4 years at testing
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Source of Fluoride:
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Self-reported maternal daily fluoride intake from water and
beverage consumption available for 400 pregnant women. the design of our
study
compares water fluoride level and IQ score |
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Water Fluoride Level:
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0.7 mg/L in fluoridated communities
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Type of IQ Test:
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Wechsler Preschool and Primary Scale of Intelligence, ThirdEdition. Full Scale IQ (FSIQ), a measure of global intellectual
functioning, was the primary outcome. We also assessed verbal IQ (VIQ),
representing verbal reasoning and comprehension, and performance IQ (PIQ),
representing nonverbal reasoning, spatial processing, and visual-motor skills.
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Results:
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Data on Maternal urinary fluoride (MUFSG) concentrations, IQ scores, and complete covariates were
available for 512 mother-child pairs; data on maternal fluoride intake
and children’s IQ were available for 400 of 601mother-child pairs. Women living
in areas with fluoridated tap water (n = 141) compared with nonfluoridated
water (n = 228) had significantly higher mean (SD) MUFSG concentration. A
1-mg/L increase in MUFSG was associated with a 4.49-point lower IQ score (95% CI,
-8.38 to -0.60) in boys, but there was no statistically significant
association with IQ scores in girls (B= 2.40; 95% CI, -2.53 to
7.33). A 1-mg higher daily intake of fluoride among pregnant women was associated with a 3.66 lower IQ score (95% CI, -7.16
to -0.14) in boys and girls. Children had mean (SD) Full Scale IQ scores of
107.16 (13.26), range 52-143, with girls showing significantly higher mean
(SD) scores than boys: 109.56 (11.96) vs 104.61(14.09); P= .001. There was a
significant interaction (P= .02) between child sex and MUFSG (6.89; 95% CI,
0.96-12.82) indicating a differential association between boys and girls.
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Conclusions:
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“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.”
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Funding for Study:
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This study was funded by a grant from the
U.S. National Institute of Environmental Health Sciences (grant R21ES027044).
The Maternal-Infant Research on Environment
Chemicals Study (from which the women were chosen) was supported by the
Chemicals Management Plan at Health Canada, the Ontario Ministry of the
Environment, and the Canadian Institutes for Health Research
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IQ Study #61: (Cui-2018) |
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Citation:
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Cui Y, Zhang B, Ma J, Wang Y, Zhao L, Hou C, Yu J, Zhao Y, Zhang
Z, Nie J, Gao T, Zhou G, Liu H. (2018). Dopamine
receptor D2 gene polymorphism, urine fluoride, and intelligence impairment of
children in China: A school-based cross-sectional study. Ecotoxicology
and Environmental Safety, Sept 11;165:270-277.
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Location of Study:
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CHINA. Tianjin. Four
schools in both historical endemic and non-endemic areas of fluorosis.
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Size of Study:
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323 children. Urine fluoride levels and age-specific IQ scores
in children were measured at the enrollment.
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Age of Subjects:
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7–12 years old.
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Source of Fluoride:
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Drinking water
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Water Fluoride Level:
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Endemic fluorosis area = 1.52–2.49 mg/L.
Nonendemic fluorosis area 0.20–1.00 mg/L. |
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Type of IQ Test:
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Combined Raven’s Test – The Rural in China (CRT-RC) method,
which is based on the Raven’s Standard Progressive Matrices (SPM) and the
Color Progressive Matrices (CPM) and was widely adopted in China with
modifications.
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Results:
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the relationship between urine fluoride levels and IQ scores
was significant after adjusting for child age, mother’s education, family
member smoking, stress, and anger.
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Urine fluoride was inversely associated with IQ.
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DRD2 Taq 1A polymorphism was not related to IQ in children
exposed to high fluoride.
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Urine fluoride had a stronger association with IQ in children
with TT genotype.
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The threshold of urine fluoride affecting IQ in children with
TT genotype existed.
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Conclusions:
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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, and careful modeling with applications of cross-validation,
bootstrap techniques, and sensitivity analysis.
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).
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Funding for Study:
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This work was supported by the National Nature Science
Foundation of China (Grant nos. 81573107 and 81372934), Scientific and
Technological Project of Tianjin Medicine in 2014 (Grant no. 14KG120) and
Scientific and Technological Project of Tianjin Centers for Disease Control
and Prevention (Grant no. CDCKY1501).
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IQ Study #60: (El Sehmawy-2018) |
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Citation:
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El Sehmawy AAEW, Hammouda SM, Ibrahim GE, Barghash SS, Elamir
RY. (2018). Relationship between Drinking
Water Fluoride and Intelligence Quotient in Egyptian School Children. Occupational
Medicine & Health Affairs, Aug 13: 6:3.
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Location of Study:
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EGYPT. Beheira
Governorate. Two different towns (urban) and four village (rural), the towns
are Italy Elbaroud Center and two villages that belong to it, the second town
is Shubra Khit Center and two villages that belong to it.
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Size of Study:
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1,000 children, 495 (49.5%) female and 405 (50.5%) male
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Age of Subjects:
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4.6 – 11 years old
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Source of Fluoride:
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Drinking water
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Water Fluoride Level:
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1.903 ± 1.06 mg/L; 0.330-0.377 mg/L .
the mean arsenic and cadmium
levels in tap drinking water was (0.005 ± 0.004 mg/L) and (0.002 ±0.001 mg/L)
for arsenic and cadmium respectively which are below the recommended WHO and
the Egyptian level for all.
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Type of IQ Test:
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The Draw-A-Person (DAP) test is a valuable instrument for the
assessment of IQ, not only because it is easy to administer, but also for its
multiple uses [25]. The children’s drawings reflect their intellectual
development, not just their visual-motor skills, therefore DAP test is useful
for assessing children IQ between the age of 4 and 13 [26].
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Results:
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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.
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Conclusions:
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A real relationship between fluoride exposure and intelligence
with the average IQ of high fluoride group was lower than those with lower
fluoride level.
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Funding for Study:
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No source identified.
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IQ Study #59: (Induswe-2018) |
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Citation:
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Induswe B, Opinya G, Khasakhala LI, Owino R. (2018). 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, Jan; 8(0):274-290.
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Location of Study:
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KENYA. Kajiado North
Subcounty in North Kajiado in the Great rift valley.
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Size of Study:
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269 school children; 178 (66.2%) female; 91 (33.8%) male.
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Age of Subjects:
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13-15 years
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Source of Fluoride:
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Drinking water
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Water Fluoride Level:
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15 (5.58%) had F level between 0-0.5mg/l;
52 (19.33%) had F level between 0.6-0.8 mg/l;38 (14.12%) had F between 0.9-1 mg/l; 41 (15.24%) had F level between 1.1-1.8 mg/l; 44 (16.36%) had F between 1.9-2.5 mg/l; 79 (29.37%) had F above 2.5mg/l. |
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Type of IQ Test:
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Wechsler intelligence scale for Children V (WISC-V) subtest
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Results:
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A comparison of the AWM (Auditory Working Memory) of children
from low (105.40±23.6) and high (99.52±23.2) fluoride schools and medium with
high fluoride school had significant differences. The AWM for the children
whose household water had low fluoride had higher AWMI 122.58±19.9 compared
to those whose household had high fluoride in the with ANOVA F (2, 266) =
17.968, p?.0001 and Tukey HSD for low and medium (m=-5.919, se=3.146, p=.145,
low and high fluoride, (m=-18.559. se=3.124, p?.001; medium and high
(m=-12.640, se= 3.32, p?.001 at 95% CL.
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Conclusions:
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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.
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Funding for Study:
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No source identified.
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IQ Study #58: (Mustafa-2018) |
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Citation:
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Mustafa DE, Younis UM, Elhag SA. (2018). The
relationship between the fluoride levels in drinking water and the schooling
performance of children in rural areas of Khartoum State, Sudan. Fluoride 51(2):102–113.
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Location of Study:
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SUDAN. 16 rural areas in
Khartoum state. These villages depend on groundwater as the main source of
drinking water because of the lack of a central water supply. The main
activities in these villages are agriculture and animal breeding. The
villages lack any industrial and mining activities and are located away from
high traffic roads.
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Size of Study:
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775 primary students, 315 boys and 460 girls from 27 schools.
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Age of Subjects:
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NA
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Source of Fluoride:
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Ground water
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Water Fluoride Level:
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The range for the F level was 0.14–2.07 mg/L
in the dry season and0.01–1.34 mg/L in the rainy season (Table 1).
Although the F level not extremely high,
frequent water drinking may occur due to several factors such as the rural
human activities, arid conditions, and high temperatures. In addition, food
products also contribute to the F intake as the people in these areas consume
their own crops. These crops may possibly accumulate F to considerable
levels.
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Type of IQ Test:
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Using the Khartoum Ministry of Education’s method, the
schooling performance for the boys’ and girls’ primary schools in the 16
areas where the F samples were taken and were assessed by calculating the
average score and high score prevalence… Generally, the schooling performance
in these rural areas was poor compared to urban areas. There were also
significant dropout rates in these rural areas, which could reflect even
lower schooling performances.
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Results:
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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 exit
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.
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Conclusions:
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In summary, the results of this study suggest that there may
be an association between the fluoride level in drinking water and the
schooling performance of children. This result may be applicable to children
in other areas with conditions similar to those of the study areas.
Consequently, the upper permissible drinking water fluoride level needs to be
revised downwards to minimize the effect of fluoride on children
neurodevelopment
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Funding for study:
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The Department of Research, Ministry of Higher Education and
Scientific Research, Sudan.
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IQ Study #57: (Pang-2018) |
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Citation:
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Pang H, Yu L, Lai X, Chen Q. (2018). 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 Diseases 32(2):151-152. Study
in Chinese translated into English.
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Location of Study:
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CHINA. The areas for
population sampling were divided into a non-endemic fluorosis area where the
prevalence of dental fluorosis in local children aged 8-12 is less than 30%,
and an endemic fluorosis area where the prevalence of dental fluorosis in
local children aged 8-12 is greater than 30%.
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Size of Study:
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268 children: 134 children each from endemic fluorosis area
and non-endemic fluorosis areas.
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Age of Subjects:
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8 -12 years of age
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Source of Fluoride:
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Endemic fluorosis area and non-endemic fluorosis areas.
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Water Fluoride Level:
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NA
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Type of IQ Test:
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Combined Raven’s Test (CRT)
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Results:
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This study found that in COMT gene polymorphism, there was no
difference between children in the endemic fluorosis area and those in the
non-endemic fluorosis area (P >0.05). It was found that alleles of the
COMT gene were codominantly inherited, and the activity of different
genotypes of the COMT gene expressed in vivo was somewhat different. This
study also found that there were great differences in terms of the level of
intelligence between children with Val/Val or Met/Val and children with
Met/Met, and such differences were statistically significant (P < 0.05):
children with the highly active COMT Val/Val genotype had significantly
higher intelligence than those with the Met/Met COMT genotype or the Met/Val
COMT genotype, and intelligence in children with any of the three
genotypes in the endemic fluorosis area was lower than that in the
non-endemic fluorosis area, indicating that the highly active COMT Val/Val
genotype has a protective effect on children’s intelligence development.
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Conclusions:
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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).
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Funding for Study:
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No mention
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IQ Study #56: (Jin-2017) |
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Citation:
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Jin T, Wang Z, Wei Y, Wu Y, Han T, Zhang H.
(2017). 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 34(3):229-231.
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Location of Study:
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CHINA. Cichong
Elementary School in the coal burning-related endemic fluorosis area of
Liupanshui City in Guizhou Province; and Minzu Elementary School of Guian
District’s Dangwu Township, a non-coal burning area, as the control group
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Size of Study:
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284 children: 167 were from the endemic area and 117 were the
control.
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Age of Subjects:
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8 – 12 years
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Source of Fluoride:
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Coal Burning-Related Endemic Fluorosis Areas
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Water Fluoride Level:
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NA
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Type of IQ Test:
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Raven’s Standard Progressive Matrices (RSPM)
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Results:
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we found that except for the intelligence levels of
12-year-old children in the control area being higher than that of those in
the endemic area, there were no statistically significant differences among
any of the other age groups. The differences of intelligence level among
children in the endemic area with different dental fluorosis severities also
showed no statistical significance. However, there was a negative correlation
between age and intelligence level in children of the endemic area, which is
in direct opposition to the usual situation of the intellectual development
of school-aged children in general. The reason for this is that the dental
fluorosis patients in our investigation were mainly concentrated in the
suspected fluorosis group, and patients with other levels of severity only
made up 50% of the total number of patients, with only six child patients
with moderate dental fluorosis and no child patients with severe clinical
fluorosis. The degree of fluorosis severity in the patients included in this
investigation was not high, so a dosage-effect relationship might not have
been able to be formed. In addition, the factors that influence the
intelligence level of children are multivariate, and the mechanisms are
complex, with fluorosis possibly only being one of many factors.
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Conclusions:
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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).
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Funding for Study:
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No mention
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IQ Study #55: (Razdan-2017) |
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Citation:
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Razdan P, Patthi B, Kumar JK, Agnihotri N, Chaudhan P, Prasad
M. (2017). 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 7(5):252-258.
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Location of Study:
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INDIA. Mathura district,
Uttar Pradesh.
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Size of Study:
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219: 75 from low F area, 75 medium F area, and 69 from high F
area. Identical numbers of male and female children were included.
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Age of Subjects:
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12-14 year olds
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Source of Fluoride:
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Drinking water
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Water Fluoride Level:
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Charora (Group A) had low fluoride (0.60 ppm) village, Farah
(Group B) had medium fluoride level (1.70 ppm), and Raya (Group C) had the
highest concentration of fluoride in water used for consumption (4.99 ppm).
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Type of IQ Test:
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SPM Test by John C Raven (1998)
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Results:
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Appraisal of the IQ
levels among the three groups (low-, medium-, and high-fluoride areas) showed
a statistically significant difference (P = 0.05).
None of the children in the low-fluoride region were intellectually
compromised when compared to 15 (20%) in the high-fluoride region and 4
(5.3%) in the medium-fluoride areas [Table 1]. In addition, no subject in the
low fluoride area had below average IQ in contrast to 35 (46.7%) in the high
and 10 (13.3%) in the medium-fluoride areas. Similarly, no one in medium and
high fluoride area had either above average or superior IQ when compared to
38 (55.1%) and 9 (13%) children having above average and superior IQ in
low-fluoride area, respectively.
None of the children in the low-fluoride
region had dental fluorosis as compared to 8 (10.7%), 45 (60.0%), and 22
(29.3%) children in the high-fluoride area who had mild, moderate, and severe
dental fluorosis, respectively.
|
|
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.
|
|
Funding for Study:
|
There was no financial support nor sponsorship for this study.
|
IQ Study #54: (Yu-2018) |
|
|
Citation:
|
Yu X, Chen J, Li Y, Liu H, et al. (2018). Threshold
effects of moderately excessive fluoride exposure on children’s health: A
potential association between dental fluorosis and loss of excellent
intelligence. Environment International,
Jun 2; 118:116-124.
|
|
Location of Study:
|
CHINA. In endemic and
non-endemic fluorosis areas
in Tianjin.
|
|
Size of Study:
|
2,886 resident children
|
|
Age of Subjects:
|
7 to 13 years
|
|
Source of Fluoride:
|
Drinking water
|
|
Water Fluoride Level:
|
The water fluoride concentration ranged from 0.20 mg/L to 1.00
mg/L, with a mean value of 0.50 ± 0.27 mg/L in the normal fluoride exposure
group, and from 1.10 mg/L to 3.90 mg/L, with a mean value of 2.00 ± 0.75 mg/L
in the high-fluoride exposure group (Table 1).
|
|
Type of IQ Test:
|
We examined the
dose-response effects of
low-to-moderate fluoride exposure on dental fluorosis (DF) and intelligence quotient
(IQ), and evaluated the potential relationships
between DF grades and intelligence levels
using piecewise linear regression and multiple logistic regression,
respectively.IQ scores were measured using the second edition of Combined
Raven’s Test–The Rural in China (CRT-RC2) (Liu et al., 2009) for children
aged 7 to 13 years. The CRT-RC2 is a validated test for basic cognitive
abilities, and has been widely adopted in China after modifications, as it is
non-verbal and less affected by language, and cultural and ethnic differences
(Sun et al., 2015).
Dean’s fluorosis index (WHO criteria)
(Molina-Frechero et al., 2015) was used to estimate the prevalence and
severity of DF. Each participant was examined by two qualified and
independent experts, who had rich experience on examination of dental
fluorosis… The final diagnosis was made only when judgments from the two
experts were in agreement; if not, a third expert would join in and offer suggestion.
For repeatability, 10% of participants were double checked and the Kappa
value was 0.82.
|
|
Results:
|
The adjusted odds ratios (ORs) of DF were 2.24 (95% confidence
interval [CI]: 2.02 to 2.48) for every 0.1 mg/L increment in the water fluoride concentration in
the range of 0.80 to 1.50 mg/L, and 2.61 (95% CI: 2.32 to 2.93) for every 0.5
mg/L increment in the urinary fluoride level up to 1.80 mg/L. Every 0.5
mg/L increment in the water fluoride level was associated with a
reduction of 4.29 in the IQ score (95% CI: -8.09 to -0.48) in the range of
3.40 to 3.90 mg/L, and a decreased probability of developing excellent intelligence (IQ ?130, OR
= 0.60, 95% CI: 0.47 to 0.77) in the range of 0.20-1.40 mg/L, respectively.
Every 0.5 mg/L increment in the urinary fluoride level was related to a decrease of
2.67 in the IQ scores (95% CI: -4.67 to -0.68) between 1.60 mg/L to 2.50
mg/L. Excellent intelligence decreased by
51% in children with higher urinary fluoride, and by 30% with each degree increment of
DF.
|
|
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 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. Thus, it is important to monitor water
quality, and supply fluoride-free drinking water to safeguard children’s
health.
|
|
Funding for Study:
|
This study was supported by the State Key Program of National
Natural Science of China (Grant No. 81430076) and the Fundamental Research Funds
for the Central Universities (HUST 2015ZDTD052 and HUST 2016YXMS221).
|
IQ Study #53: (Bashash 2017) |
|
|
Citation:
|
Bashash M, Thomas D, Hu H, Martinez-Mier EA, Sanchez BN, Basu N,
Peterson KE, Ettinger AS, Wright R, Zhang Z, Liu Y, Schnaas L, Mercado-García
A, Téllez-Rojo MM, Hernández-Avila M. (2017). Prenatal
Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of
Age in Mexico. Environmental Health
Perspectives, Sept 19;125(9):097017.
|
|
Location of Study:
|
MEXICO. Participants from
the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT)
project.
|
|
Size of Study:
|
299 mother–child pairs, of whom 287 and 211 had data for the
General Cognitive Index and IQ analyses, respectively.
|
|
Age of Subjects:
|
Tests of cognitive function in the offspring at age 4 and 6–12
years.
|
|
Source of Fluoride:
|
Fluoridated salt (at 250?ppm) and to varying degrees of
naturally occurring fluoride in drinking water.
|
|
Water Fluoride Level:
|
Natural water fluoride levels in Mexico City may range from
0.15 to 1.38 mg/L
|
|
Type of IQ Test:
|
“At age 4 y, neurocognitive outcomes were measured using a
standardized version of McCarthy Scales of Children’s Abilities. For children
6–12 y old a Spanish-version of the Wechsler Abbreviated Scale of
Intelligence.”
|
|
Results:
|
“In multivariate models we found that an increase in maternal
urine fluoride of 0.5mg/L (approximately the IQR) predicted 3.15 (95% CI:
5.42, 0.87) and 2.50 (95% CI 4.12, 0.59) lower offspring GCI and IQ scores,
respectively.”
|
|
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.”
|
|
Funding for study:
|
This study was supported by the U.S. National Institutes of
Health (NIH; grants R01ES021446 and R01-ES007821); the National Institute of
Environmental Health Sciences/the U.S. Environmental Protection Agency
(NIEHS/EPA; grant P01ES022844), the NIEHS (grant P42-ES05947 and NIEHS Center
Grant P30ES017885), and by the National Institute of Public Health/Ministry
of Health of Mexico. The American British Cowdray Hospital provided facilities
used for this research.
|
IQ Study #52: (Valdez Jiménez 2017) |
|
|
Citation:
|
Valdez Jiménez L, López Guzmán OD, Cervantes Flores M,
Costilla-Salazar R, Calderón Hernández J, Alcaraz Contreras Y, Rocha-Amador
DO. 2017. In utero exposure to fluoride
and cognitive development delay in infants. Neurotoxicology Mar;59:65-70.
|
|
Location of Study:
|
MEXICO. Durango City and
Lagos de Moreno, Jalisco. Both are endemic hydro-fluorosis areas.
|
|
Size of Study:
|
“65 mother-infant pairs recruited from 2013 to 2014. Inclusion
criteria were: 12 weeks of gestation, with no history of thyroid
disease, without clinically diagnosed diabetes, and a minimum 5 years of
residence in the study area.”
|
|
Age of Subjects:
|
“The average age of children assessed was 8 months (3–15
months) and almost 70% were girls.” The average age of the mothers was
22.4 ±4.0.
|
|
Source of Fluoride:
|
The study was performed in an endemic hydrofuorosis area.
According to the authors: ‘in Mexico F in water remains as the main source of
F exposure. In endemic hydrofuorosis areas of Mexico only non-fluorinated
salt is distributed according to the NOM-040-SSA1-1993.”
|
|
Water Fluoride Level:
|
F levels in tap water mean concentrations
for each trimester were: 2.6 ±1.1 mg/l, 3.1 ±1.1 mg/l and
3.7 ±1.0 mg/l respectively. It is worthy to note that over 81.5% of the
samples of tap water were above 1.5 mg/l (NOM-127- SSA1-1994) with the
highest value of 12.5 mg/.
33.8% of women reported drink tap water and
78.4% use it for cooking. The practice of use tap water for drink or cooking
is crucial because exposure to F could be increased when the infant change to
bottle feeding and starts solid foods. Regarding, bottled water it is
important to mention that we have analyzed several brands of this water and
65% of the samples exceeded the 0.7 mg/l value (NOM-041-SSA1-1993) and 22.9%
had values over 1.5 mg/l (NOM-127-SSA1-1994) data not shown.
|
|
Type of IQ Test:
|
“Neurodevelopment was assessed with the Bayley Scales of
Infant Development II (BSDI-II) (Bayley, 1993). This test has good
reliability and validity; it is applied to evaluate developmental delay in
children between 3 months to 5 years in Mexico by the SSA (CNPSS, 2013). The
Mental Development Index scale (MDI) of the Bayley test evaluate aspects of
functioning such as eye-hand coordination, manipulation, understanding of
object relation, imitation and early language development whereas the
Psycho-motor Development Index (PDI) scale assesses gross motor development…
To standardize the raw scores for children who were born prematurely, the
number of months of prematurity was subtracted from their chronological age.
The scores below 85 points indicated a possible developmental delay.”
|
|
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)
|
|
Conclusions:
|
“After adjusting for potential confounding factors
(gestational age, age of child, marginalization index and type of water for
consumption), the MDI [Mental Development Index] showed an inverse
association with F levels in maternal urine for the first (b = -19.05, p = 0.04) and second trimester (b
= -19.34, p = 0.01). Our data suggests
that cognitive alterations in children born from exposed mothers to F could
start in early prenatal stages of life.
|
|
Funding for study:
|
The authors acknowledge the financial support of this research
by CONACYT with number 181577, FONSEC 2012 and the University of Guanajuato
through DAIP support with number FO-DAI-05, 2013. The present work was
carried out during the first
period of the first author postdoctoral training (fellowship number 239404). |
IQ Study #51: (Das 2016) |
|
|
Citation:
|
Das K, Mondal NK. (2016). 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
& Assessment 188(4):218.
|
|
Location of Study:
|
INDIA. West Bengal.
|
|
Size of Study:
|
149 schoolchildren
|
|
Age of Subjects:
|
6 to 18
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Level:
|
Average = 2.1 mg/L (S.D. = 1.64 mg/L)
|
|
Type of IQ Test:
|
Combined Raven’s Test for RuralChina (CRT-RC)
|
|
Results:
|
“IQ has anegative significant correlation
with dental fluorosis (r=0.253,P<0.01). Dental fluorosis acts as
an indicator of decreasing level of IQ. As fluorosis is a consequence of
fluoride exposure, so IQ has a negative significant correlation with
exposure dose (r =0.343, P<0.01) which was considered as a fluoride
input source.”
“IQ values were plotted against the
urinary fluoride concentration and it was found that they have a
significant negative correlation (r=0.751, P<0.01).”
|
|
Conclusion
|
“[C]hildren residing in areas with higher than normal
water fluoride level demonstrated more impaired development of
intelligence and moderate [dental fluorosis]. Millions of children
including adults around the world are affected by higher level of
fluoride concentration through their drinking water and are therefore
potentially at risk. It is concluded that for the benefit of the future
generation, urgent attention should be paid on this
substantial public health problem.”
|
IQ Study #50: Aravind et al. |
|
|
Citation:
|
Aravind A, Dhanya RS, Narayan A, Sam G, Adarsh VJ, Kiran
M. (2016). Effect of fluoridated water
on intelligence in 10-12-year-old school children. Journal
of International Society of Preventive & Community Dentistry 6 (Suppl 3), S237-S242.
|
|
Location of Study:
|
Schools: Virajpet (low fluoride level < 1.2 ppm), Banavara
(Medium fluoride level 1.2-2 ppm), and Mastihalli (High fluoride levels >
3 ppm).
|
|
Size of Study:
|
96 children from each of the three fluoride water levels
above, for a total of 288.
|
|
Age of Subjects:
|
10–12 years
|
|
Source of Fluoride:
|
Drinking water
|
|
Type of IQ Test:
|
Raven’s Standard Progressive Matrices 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.
|
|
Conclusions:
|
It is concluded that IQ level was negatively correlated with
fluoride level in drinking water. Factors that might affect children’s IQ
need to be considered, and it is necessary to devise solutions for preventing
the harmful effects of excessive intake of fluoride ion to the body.
|
|
Funding:
|
No financial support or sponsorship.
|
IQ Study #49: Mondal (2016) |
|
|
Citation:
|
Mondal D, Dutta G, Gupta S. (2016). 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
& Health 38(2):557-76.
|
|
Location of Study:
|
INDIA. Birbhum district.
|
|
Size of Study:
|
40 children (20 from endemic fluorosis area; 20 from control
area)
|
|
Age of Subjects:
|
10 to 14 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
“Mean F concentration in the study area varies from 0.32 to
13.29 mg/L.”
|
|
Type of IQ Test:
|
Raven Standard Theoretical Intelligence Test
|
|
Results:
|
“This study indicates that students exposed to high F
(children of Junidpur and Nowapara) show an average IQ of 21.17 ± 6.77 in
comparison with low-F exposed students (children of Bilaspur, Mohula,
Bhalian) having an average IQ of 26.41 ± 10.46. . . . Statistical analysis (Z
test) demonstrates that there is a significant (Z = 2.59) difference in IQ
among the high- and low-F area student.”
|
|
Conclusion
|
“[S]tudents of the study area have less IQ than students of
non-contaminated area, demonstrating that consumption of F also has a major
role with the intellectual development of
children.” |
IQ Study #48: Khan (2015) |
|
|
Citation:
|
Khan SA, Singh RK, Navit S, Chadha D, Johri N, Navit P, Sharma
A, Bahuguna R. (2015). 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 9(11):ZC10-15.
|
|
Location of Study:
|
INDIA. Lucknow district.
|
|
Size of Study:
|
429 schoolchildren
|
|
Age of Subjects:
|
6-12 years old
|
|
Source of Fluoride:
|
Water
|
|
Results:
|
“In this study, on comparison of children at two locations
according to IQ grades [Table/Fig-4], majority of the children (74.8%) living
in low fluoride area had an IQ grade 2 (definitely above the average in
intellectual capacity). None of the children from the low fluoride area had
an IQ grade 4 and 5 (definitely below average and intellectually impaired).
On the other hand, majority of children (58.1%) from high fluoride area fall
under IQ grade 3 (intellectually average). None of the children from high
fluoride area had an IQ grade 1 (intellectually superior). This difference in
IQ grades of children amongst the two areas was found to be statistically
significant (p<0.001).””[I]t is clearly evident that with increase in the
grade of fluorosis, a trend of increase in the IQ grade (decrease in
intellectual capacity) was observed indicating a strong correlation between
fluorosis grade and IQ grade (Spearman’s p=0.766).”
|
|
Conclusion:
|
“The data from this research may support the hypothesis that
excess fluoride in drinking water has toxic effects on the nervous system.”
|
IQ Study #47: Sebastian (2015) |
|
|
Citation:
|
Sebastian ST, Sunitha S. 2015. 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 33(4):307-11.
|
|
Location of Study:
|
INDIA. Mysore district.
|
|
Size of Study:
|
405 schoolchildren (135 children from high fluoride area; 135
children from “normal” fluoride area; 135 chidren from “low” fluoride area)
|
|
Age of Subjects:
|
10-12 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High-fluoride: 2.2 mg/L; “Normal” Fluoride: 1.2 mg/L; “Low”
Fluoride: 0.4 mg/L
|
|
Type of IQ Test:
|
Raven’s colored Progressive Matrices Test
|
|
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.”
|
IQ Study #46: Kundu (2015) |
|
|
Citation:
|
Kundu H, Basavaraj P, Singla A, Gupta R, Singh K, Jain S.
(2015). 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 13(2):116-121.
April-June.
|
|
Location of Study:
|
INDIA. Delhi.
|
|
Size of Study:
|
200 school children:
100 from low F area and 100 from high F area.
|
|
Age of Subjects:
|
8-12 years of age.
Equal numbers of male
and female children were included in the study.
|
|
Source of Fluoride:
|
Water
|
|
Type of Cognitive Tests:
|
Ravens Standardized
Progressive Matrices Test
|
|
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.”
|
IQ Study #45: Choi (2015) |
|
|
Citation:
|
Choi AL, Zhang Y, Sun G, Bellinger D, Wang K, Yang XJ, Li JS,
Zheng Q, Fu Y, Grandjean P. (2015). Association of lifetime
exposure to fluoride and cognitive functions in Chinese children: A pilot
study. Neurotoxicology &
Teratology 47:96-101.
|
|
Location of Study:
|
CHINA. Southern Sichuan
Province.
|
|
Size of Study:
|
51 children from elevated fluoride area
|
|
Age of Subjects:
|
Avg = 7.1 years old
|
|
Source of Fluoride:
|
Water
|
|
Urine Fluoride Levels:
|
Mean = 1.64 mg/L; Range = 0.22 to 5.84 mg/L
|
|
Water Fluoride Levels:
|
Mean = 2.2 mg/L; Range = 1.0 to 4.07 mg/L
|
|
Confounding Factors:
|
“In this rural community, social differences
are limited. The parents or guardians completed a questionnaire on
demographic and personal characteristics including the child’s sex, age at
testing, parity, illnesses before age 3, past medical history of the child
and caretakers, parental or guardian age, education and occupational
histories, and residential history, and household income. It is known that
iron deficiency can impair motor and mental developments in children, iron
concentration was therefore considered as a covariate. These potential
confounders were used for adjustment in the statistical analysis.”
“Among possible confounders, both arsenic
and lead are known to be low in drinking water in the area.”
|
|
Type of Cognitive Tests:
|
WRAML, WISC-R, WRAVMA
|
|
Results:
|
“Results of our pilot study showed that moderate and severe
dental fluorosis was significantly associated with deficits in WISC-R digit
span. Children with moderate or severe dental fluorosis scored significantly
lower in total and backward digit span tests than thosewith 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.”
|
|
Conclusion:
|
“Results of our field study raise a concern about the safety
of elevated systemic exposure to fluoride from high concentrations in the
drinking water.While topical fluoride treatment confers benefits of reducing
caries incidence, the systemic exposure should not be so high as to impair
children’s neurodevelopment especially during the highly vulnerable windows
of brain development in utero and during infancy and childhood and may result
in permanent brain injury. We are planning a larger scale study to better
understand the dose–effect relationships for fluoride’s developmental
neurotoxicity in order to characterize the appropriate means of avoiding
neurotoxic risks while securing oral health benefits.”
|
IQ Study #44: Zhang (2015) |
|
|
Citation:
|
Zhang S, Zhang X, Liu H, Qu W, Guan Z, Zeng Q, Jiang C, Gao H,
Zhang C, Lei R, Xia T, Wang Z, Yang L, Chen Y, Wu X, Cui Y, Yu L, Wang A.
(2015). 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 144(2):238-45. April.
|
|
Location of Study:
|
CHINA. Tianjin City.
|
|
Size of Study:
|
180 children (96 from control area; 84 from “high fluoride”
area)
|
|
Age of Subjects:
|
Avg = 11 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High = 1.4 mg/L
Control = 0.63 mg/L |
|
Urine Fluoride Levels:
|
High = 2.4 + 1.01 mg/L
Control = 1.10 + 0.67 mg/L |
|
Serum Fluoride Levels:
|
High = 0.18 + 0.11 mg/L
Control = 0.06 + 0.03 mg/L |
|
Type of IQ Test:
|
Combined Raven’s Test for Rural China (CRT-RC)
|
|
Confounding Factors:
|
“Covariates included the indicator variables for age, gender,
educational levels of parents (primary and below, junior high school, senior
high school, and above), and continuous variables for drinking water fluoride
(mg/l) and levels of thyroid hormones (T3, T4, and TSH).”
|
|
Results:
|
“[T]he present work demonstrated that the IQ scores of
children exposed to high fluoride drinking water were significantly lower
than those who lived in control area . . . . [O]ur findings further showed
that, across the full range of serum and urinary fluoride, children’s IQ
decreased gradually with the increase of fluoride contents in serum and
urine, in a dose-dependent manner.”
|
|
Conclusion:
|
“In summary, our data suggest that the intelligence of
children is affected by the COMT gene polymorphism and, in particular, this
SNP plays a role in modifying the effect of fluoride exposure on cognition.
Children with COMT reference allele had a higher risk for cognitive
impairments after fluoride exposure. Additionally, proteomics analysis
represents early specific markers of developmental fluoride neurotoxicity.
Hence, our findings provide certain basis for clarifying the mechanisms and
identifying molecular targets of pharmacological interventions for potential
delayed therapy.”
|
IQ Study #43: Bai (2014) |
|
|
Citation:
|
Bai Z, Li Y, Fan Z, Li X, Li P. (2014) 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 33(2):160-163.
|
|
Location of Study:
|
CHINA. Shaanxi Province.
|
|
Size of Study:
|
303 children (120 children from high-fluoride area; 95 from
mid-fluoride area, 98 from low-fluoride area)
|
|
Age of Subjects:
|
8 to 12 years old
|
|
Source of Fluoride
|
Coal burning
|
|
Urine Fluoride Levels:
|
“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.”
|
|
Results:
|
“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”
|
IQ Study #42: Wei (2014) |
|
|
Citation:
|
Wei N, Li Y, Deng J; Xu S, Guan Z. (2014). The
effects of comprehensive control measures on intelligence of school-age
children in coal-burning-borne endemic fluorosis areas. Chinese
Journal of Endemiology 33(3):320-22.
|
|
Location of Study:
|
CHINA. Bijie City,
Guizhou Province.
|
|
Size of Study:
|
741 children (104 children from low-fluoride area; 298
children from an endemic fluorosis area with long-term defluoridation
measures; 339 children from endemic fluorosis area with short-term
defluoridation measures).
|
|
Age of Subjects:
|
8-12 years old
|
|
Source of Fluoride:
|
Coal
|
|
Urinary Fluoride Levels:
|
Control: 1.34 ± 0.64 mg/L; Long-term
defluoridation: 2.33 ± 0.18 mg/L; Short-term defluoridation: 3.03 ± 0.16)
mgL.
|
|
Results:
|
“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).“
|
|
Conclusion:
|
“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.”
|
IQ Study #41: Nagarajappa (2013) |
|
|
Citation:
|
Nagarajappa R, Pujara P, Sharda AJ, Asawa K, Tak M, Aapaliya
P, Bhanushali N. (2013). 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 2(8): 813–818.
|
|
Location of Study:
|
INDIA. Kutch District,
Gujarat.
|
|
Size of Study:
|
100 children (50 children from high-fluoride area; 50 children
from control area)
|
|
Age of Subjects:
|
8-10 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High Fluoride: 2.4 to 3.5 mg/L; Control: 0.5mg/L.
|
|
Type of IQ Test:
|
Seguin Form Board Test
|
|
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.”
|
|
Conclusion:
|
“Chronic exposure to high levels of fluoride in water was
observed to be associated with lower intelligence quotient.”
|
IQ Study #40: Singh (2013) |
|
|
Citation:
|
Singh VP, Chauhan DS, Tripathi S, Kumar S, Gaur V, Tiwari M,
Tomar A. (2014). A correlation between serum
vitamin, acetylcholinesterase activity and IQ in children with excessive endemic
fluoride exposure in Rajasthan, India. European
Academic Journal 2(4):5857-5869.
|
|
Location of Study:
|
INDIA. Jaipur,
Rajasthan.
|
|
Size of Study:
|
42 children (70 from high-fluoride area; 72 from control area)
|
|
Age of Subjects:
|
9 to 14 year olds
|
|
Source of Fluoride:
|
Water
|
|
Levels of Fluoride in Water:
|
High Fluoride = 6.8 mg/L
Control area = <1.03 mg/L |
|
Confounding Factors:
|
“The subjects were similar in living conditions, parental
literacy, socioeconomic status, and health history. Moreover, age and sex matched
controls were selected from the [low-fluoride area].”
|
|
Type of IQ Test:
|
Raven’s Test
|
|
Conclusion:
|
“We observed reduced AChE activity in [the high fluoride area]
which may be directly correlate[d] with the reduced intelligence score of the
subjects.”
|
IQ Study #39: Karimzade (2014) |
|
|
Citation:
|
Karimzade S, Aghaei M, Mahvi AH. (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 47(1):9-14.
|
|
Location of Study:
|
IRAN. Poldashi and
Piranshahr, West Azerbaijan province.
|
|
Size of Study:
|
39 male children (19 from high-fluoride area; 20 from control
area)
|
|
Age of Subjects:
|
9 to 12 year olds
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High Fluoride = 3.94 mg/L
Control = 0.25 mg/L |
|
Confounding Factors:
|
No significant differences were found in the potential
confounding factors of educational, economic, social, cultural, and general
demographic characteristics between the high- and low-F regions.
|
|
Type of IQ Test:
|
Iranian version of the Raymond B Cattell test
|
|
Results:
|
“The IQ of the 19 children in the high-F region was lower
(mean±SD: 81.21±16.17), than that of the 20 children in the low-F region
(mean±SD: 104.25±20.73, p=0.0004). In the high-F region, 57.8% had scores
indicating mental retardation (IQ <70) or borderline intelligence (IQ
70–79), while this figure was only 10% in the low–F region.”
|
|
Conclusions:
|
“The study found that children residing in a region with a
high drinking water F level had lower IQs compared to children living in a
low drinking water F region (p<0.001). The differences could not be
attributed to confounding educational, economic, social, cultural, and general
demographic factors.”
|
IQ Study #38: Trivedi (2012) |
|
|
Citation:
|
Trivedi MH, Sangai NP, Patel RS, Payak M, Vyas
SJ. (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, Gujurat, India. Fluoride 45(4):377-83.
|
|
Location of Study:
|
INDIA. Gujurat.
|
|
Size of Study:
|
84 children (34 from high-fluoride villages, 50 children from
control village)
|
|
Age of Subjects:
|
6th and 7th grade students
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High Fluoride = 2.3 + 0.87 mg/L
Control = 0.83 + 0.38 mg/L |
|
Urine Fluoride Levels:
|
High Fluoride = 2.69 + 0.92 mg/L
Control = 0.42 + 0.23 |
|
Confounding Factors:
|
Same socioeconomic status (E on an A-E scale); same attendance
status at school (regular students attending more than 80% of classes)
|
|
Type of IQ Test:
|
Questionnaire prepared by Prof. JH Shah; standardized on the
Gujarati population with 97% reliability rate in relation to the
Stanford-Binet Intelligence Scale
|
|
Results:
|
“The average IQ score of the 34 students drinking the high F
water was significantly lower (p?0.05) than among the 50 students drinking
the low F water.”
|
|
Conclusions:
|
“the present investigation concludes that the three villages
of Chhasara, Gundala, and Mundra, are F-contaminated villages. Because of
high F concentrations in the [groundwater], children in these villages have
greater exposure to F that may lead in to low IQ as compared to the nearby
villages of Baroi, Zarpara, and Pragpar, which have low F in their
[groundwater].”
|
IQ Study #37: Seraj (2012) |
|
|
Citation:
|
Seraj B, Shahrabi M, Shadfar M, Ahmadi R, Fallahzadeh M,
Eslamlu HF, Kharazifard MJ. (2012). Effect of high water fluoride
concentration on the intellectual development of children in Makoo/Iran. Journal
of Dentistry, Tehran University of Medical Sciences 9(3):
221-29.
|
|
Location of Study:
|
IRAN. Makoo.
|
|
Size of Study:
|
293 children (91 children in control village; 106 children in
medium F village; 96 children in high F village)
|
|
Age of Subjects:
|
6 to 11 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
Control = 0.8+0.3 ppm
Medium fluoride = 3.1+0.9 ppm High fluoride = 5.2+1.1 ppm |
|
Confounding Factors:
|
Age, gender, child’s educational level, mother’s educational
level, father’s educational level, fluorosis intensity, iodine level in
water, lead level in water.
|
|
IQ Test:
|
Raven’s Color Progressive Matrices (RCPM)
|
|
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:
|
“Since all potentially confounding factors were adjusted,
the difference in IQ scores may reveal the potential effect of high fluoride
exposure on the intellectual development of children.”
|
IQ Study #36: Saxena (2012) |
|
|
Citation:
|
Saxena S, Sahay A, Goel P. (2012). Effect
of fluoride exposure on the intelligence of school children in Madhya
Pradesh, India. Journal of Neurosciences in
Rural Practice 3(2):144-49.
|
|
Location of Study:
|
INDIA. Madhya Pradesh.
|
|
Size of Study:
|
173 children (120 children in three high-F areas and 53
children from a control group)
|
|
Age of Subjects:
|
School children in the 5th & 6th grades
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
Group 1 = >4.5 ppm
Group 2 = 3.1-4.5 ppm Group 3 = 1.5-3.0 ppm Control = <1.5 ppm |
|
Urine Fluoride Levels:
|
Group 1 = 7.01+1.02
Group 2 = 4.85+0.50 Group 3 = 3.28+0.48 Control = 2.25+0.28 |
|
Confounding Factors:
|
(1) No significant differences in urinary lead, arsenic, or
iodine levels between the four groups. (2) No significant differences
in gender ratio, socio-economic status, SES, parental education,
height/age ratio, and weight/height ratio. (3) Children were excluded if
they were not lifelong resident of area, if they had changed their water
source since birth, or if they had history of congenital or acquired
neurological disease and/or head injury.
|
|
IQ Test:
|
Raven’s Standard Progressive Matrices
|
|
Results:
|
“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:
|
“This study indicates that exposure to fluoride is
associated with reduced intelligence in children. We have found a significant
inverse relationship between intelligence and the water fluoride level, and
intelligence and the urinary fluoride level. After adjusting for confounders,
urinary fluoride was the significant predictor for intelligence.”
|
IQ Study #35: Ding (2011) |
|
|
Citation:
|
Ding Y, Yanhui G, Sun H, Han H, Wang W, Ji X, Liu X, Sun D.
(2011). 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 186(2-3):1942-46.
|
|
Location of study:
|
CHINA. Hulunbuir, Inner
Mongolia.
|
|
Size of study:
|
331 children from four sites
|
|
Age of Subjects:
|
7-14 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
Mianduhe town=0.28+0.03 mg/L
Nan district=0.79+0.33 mg/L Donghu district=1.78+0.60 mg/L Zhalainuoer county=1.82+1.00 mg/ |
|
Urine Fluoride Levels:
|
No dental fluorosis = 0.80+0.55 mg/L
Questionable fluorosis = 1.13+0.73 mg/L Very mild fluorosis = 1.11+0.74 mg/L Mild fluorosis = 1.31+0.78 mg/L Moderate fluorosis =1.46+0.79 mg/L. |
|
Confounding Factors:
|
(1) Sites selected to match social and natural factors like
economic situation, educational standard, and geological environments.
(2) Schools had similar teaching quality. (3) Sites are not exposed
to known neurotoxins (e.g. arsenic) in drinking water, nor are they endemic
areas for iodine deficiency disorders. (4) Five children who had not
lived in these areas at least 1 year were excluded.
|
|
IQ Test:
|
CRT-RC3 (Combined Raven’s Test for Rural China)
|
|
Results:
|
Children’s IQ was inversely related to urinary fluoride
content, (p<0.0001). Each increase in 1 mg/L of urine F was associated
with 0.59 point decrease in IQ (p=0.0226).
|
|
Conclusion:
|
“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.”
|
IQ Study #34: Poureslami (2011) |
|
|
Citation:
|
Poureslami HR, Horri A, Khoramian S, Garrusi B. (2011).
Intelligence quotient of 7 to 9 year-old children from an area with high
fluoride in drinking water. Journal of Dentistry and Oral
Hygiene 3(4):61-64.
|
|
Location of study:
|
IRAN. Kerman Province;
Koohbanan (high-F) and Baft (low-F).
|
|
Size of study:
|
120 children: 60 children per city
|
|
Age of Subjects:
|
7-9 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride levels:
|
High-F = 2.38 mg/L
Low-F = 0.41 mg/L |
|
Confounding Factors:
|
(1) Exclusion criteria: genetic, congenital, or acquired
diseases related to the nervous system, past or present. (2) Inclusion
criteria (high-F village): signs of grade III TSIDF (total surface index of
Dental Fluorosis) or more. (3) Inclusion criteria (low-F village): similar
physical and mental health criteria adopted, but children lacked any sign of
Dental Fluorosis. (4) Both towns at high altitude.
|
|
Type of IQ Test
|
Raven’s Progressive Matrices Intelligence Test (Persian
version)
|
|
Results:
|
Average IQ of High F group (91.37+16.63) is significantly
lower than average IQ of Low-F group (97.80+15.95), p <
0.05.
|
|
Conclusion:
|
“Based on the findings, chronic exposure to high levels of
fluoride can be one of the factors that influence intellectual development.”
|
IQ Study #33: Eswar (2011) |
|
|
Citation:
|
Eswar P, Nagesh L, Devaraj CG. (2011). Intelligent
quotients of 12-14 year old school children in a high and low fluoride
village in India. Fluoride 44:168-72.
|
|
Location of study:
|
INDIA. Ajjihalli (low F)
and Holesirigere (high F) villages, Davangere district, Karnataka.
|
|
Size of study:
|
133 children total (low F village=65; high F village=68)
|
|
Age of Subjects:
|
12-14 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride levels:
|
High F village=2.45 mg/L
Low F village =0.29 mg/L |
|
Confounding Factors:
|
(1) Children included were continuous residents of study
villages since birth; drinking water from same public water supply (1 per
village); (2) attended same high school (1 per village). (3) Children with
history of trauma or injury to head; affected by congenital or acquired
neurological disorders, psychological disorders were excluded.
|
|
Type of IQ Test
|
Raven’s Standard Progressive Matrices Test
|
|
Results:
|
63.2% of children in high F area had IQ less than 90, versus
47.7% of children in low F village. (p=0.06).
|
|
Conclusion:
|
“Though there was a trend in our study towards lower IQ in a
greater number of children from high F village than in the low F village, probably
the small sample size of the present study failed to establish a
statistically significant difference.”
|
IQ Study #32: Shivaprakash (2011) |
|
|
Citation:
|
Shivaprakash PK, Ohri K, Noorani H. (2011). Relation
between dental fluorosis and intelligence quotient in school children of
Bagalkot district. J Indian Soc Pedod Prev Dent. 29(2):117-20.
|
|
Location of study:
|
INDIA. Bagalkot
district, Karnataka state.
|
|
Size of study:
|
160 children
|
|
Age of Subjects:
|
7-11 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
high F village = 2.5-3.5 mg/L
low F village = < 0.5 mg/L |
|
Confounding Factors:
|
(1) Children included in study had normal birth history, were
permanent residents in the region of study, had no history of trauma to the
head, no history of chronic illness, not on medication. (2) Villages have
similar culture, standard of living, and lifestyle habits.
|
|
Type of IQ Test
|
Raven’s Colored Progressive Matrices Test
|
|
Results:
|
(A) Children with dental fluorosis had lower IQ (66.63+18.09) than those without dental fluorosis (76.36+20.84), p < 0.05. (B) Children with mild
dental fluorosis had lower IQ (66.73) than those without dental fluorosis
(75.89), p < 0.05.
|
|
Conclusion:
|
“Previous studies had indicated toward decreased Intelligence
in children exposed to high levels of fluoride and our study also confirmed
such an effect.”
|
IQ Study #31: Sudhir (2009) |
|
|
Citation:
|
Sudhir KM, Chandu GN, Prashant GM, Subba Reddy VV.
(2009). Effect of fluoride exposure
on intelligence quotient (IQ) among 13-15 year old school children of known
endemic area of fluorosis, Nalgonda District, Andhra Pradesh. Journal
of the Indian Association of Public Health Dentistry 13:88-94.
|
|
Location of Study:
|
INDIA. Nalgonda
District, Andhra Pradesh.
|
|
Size of Study:
|
1000 children
|
|
Age of Subjects:
|
13-15 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
Four areas were studied: <0.7 mg/L; 0.7-1.2 mg/L; 1.2-4.0
mg/L; >4 mg/L
|
|
Type of IQ Test:
|
Raven’s standard progressive matrices
|
|
Results:
|
“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’s exposed to high fluoride level were significantly lower than the
low fluoride areas.”
|
IQ Study #30: Li (2009) |
|
|
Citation:
|
Li F, Chen X, Huang R, Xie Y. (2009). The
impact of endemic fluorosis caused by the burning of coal on the development
of intelligence in children. Journal of Environmental
Health 26(4):838-40.
|
|
Location of study:
|
CHINA. Xinhua County, Hunan Province.
|
|
Size of study:
|
80 children total: 20 children from “mild” fluorosis area, 20
from “medium” fluorosis area, 20 from “severe” fluorosis area, and 20 from
non-fluorosis area.
|
|
Age of Subjects:
|
8-12 years old
|
|
Source of Fluoride:
|
Coal burning
|
|
Fluoride exposure levels:
|
Urine F (by region):
severe = 2.34+1.13 mg/L
medium = 1.67+0.66 mg/L mild = 1.24+0.43 mg/L control = 0.96+0.52 mg/L
Urine F (by dental fluorosis type):
severe = 2.66+1.09 mg/L
medium = 2.01+0.80 mg/L mild = 1.64+0.68 mg/L very mild = 1.17+0.48 mg/L suspected = 1.09+0.36 mg/L no fluorosis = 0.87+0.23 mg/L. |
|
Confounding Factors:
|
(1) All children were born and raised in the respective areas.
(2) Children were excluded if they had been diagnosed with physical
deformation, developmental disorders, delayed mental development, emotional/behavioral
obstacles or challenges, or other forms of mental disorders.
|
|
Type of IQ Test
|
CRT-RC (Combined Raven’s Test for Rural China)
|
|
Results:
|
– IQ decreased with increasing F level in urine (p < 0.01)
– IQ was significantly reduced among children with severe fluorosis as
compared to children without fluorosis (p < 0.05) – A trend (albeit not
statistically significant) for IQ to decrease with increasing severity of
dental fluorosis (NS) and with increasing severity of the region’s fluoride poisoning
|
|
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.”
|
IQ Study #29: Rocha-Amador (2007) |
|
|
Citation:
|
Rocha-Amador D, Navarro ME, Carrizales L, Morales R, Calderón
J. (2007). Decreased intelligence in
children and exposure to fluoride and arsenic in drinking water. Cadernos
de Saude Publica 23(Suppl 4):S579-87.
|
|
Location of study:
|
MEXICO. Durango State,
Mexico & San Luis Potosi State.
|
|
Size of study:
|
132 children
|
|
Age of Subjects:
|
6 to 10 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels
|
Lowest F village: 0.8+1.4 mg/L
Middle F village: 5.2+0.9 mg/L Highest F village: 9.4+0.9 mg/L |
|
Urine Fluoride Levels
|
Lowest F village: 1.8+1.5 mg/L
Middle F village: 6.0+1.6 mg/L Highest F village: 5.5+3.3 mg/L |
|
Confounding Factors:
|
(1) A multiple regression analysis was used that controlled
for blood lead levels, socioeconomic status, mother’s education,
height-for-age (an index of malnutrition), and transferrin saturation. (2)
Each child’s water fluoride level, and urine fluoride level, levels were
individually determined. (3) The test examiner was blinded as to the
children’s fluoride exposure.
|
|
IQ Test:
|
Wechsler Intelligence Scale for Children–Revised Mexican
Version (WISC-RM)
|
|
Results:
|
(1) Both fluoride in urine, and fluoride in water, were
significantly correlated with IQ, and this correlation remained significant
after controlling for lead exposure, socioeconomic status, mother’s
education, malnutrition, and transferrin. (2) Fluoride’s effect on IQ was
larger than the effect from arsenic.
|
|
Conclusion:
|
“We found that exposure to F in urine was associated with
reduced Performance, Verbal and Full IQ scores before and after adjusting for
confounders. The same pattern was observed for models with F in water as the
exposure variable. . . . The individual effect of F in urine indicated that
for each mg increase of F in urine a decrease of 1.7 points in Full IQ might
be expected.”
|
IQ Study #28: Wang (2007) |
|
|
Citation:
|
Wang SX, Wang ZH, Cheng XT, Li J, Sang ZP, Zhang XD, Han LL,
Qiao XY, Wu ZM, Wang ZQ. (2007). Arsenic and fluoride exposure
in drinking water: children’s IQ and growth in Shanyin county, Shanxi
province, China. Environmental Health
Perspectives 115(4):643-7.
|
|
Location of study:
|
CHINA. Shanyin County, Shanxi Province.
|
|
Size of study:
|
720 children: 21-196 per village (3 villages for each of the
arsenic groups)
|
|
Age of Subjects:
|
8-12 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High-Arsenic group = 0.9+0.5 mg/L
Medium-Arsenic group = 1.7+1.1 mg/L High-Fluoride group = 8.3+1.9 mg/L Control group = 0.5+0.2 mg/L |
|
Urine Fluoride levels:
|
High-Arsenic group = 1.0+1.7 mg/L
Medium-Arsenic group = 2.8+1.9 mg/L High-Fluoride group = 5.1+2.0 mg/L Control group = 1.5+1.6 mg/L |
|
Confounding Factors:
|
(1) Arsenic used as variable. Similar manganese levels in
water for all groups. (2) All groups lived in rural areas with similar
geographic and cultural conditions and a comparable level of socioeconomic
development (years of parental education, average income, years of exposure).
(3) All children currently attending school.
|
|
Type of IQ Test
|
CRT-RC (Combined Raven’s Test for Rural China)
|
|
Results:
|
– Average IQ in high-arsenic area (95.1+16.6) is significantly lower than IQ in control area
(104.8+14.7). p < 0.05 – The average IQ in high-fluoride
area (100.5+15.8) is also significantly lower than average IQ in
control area (104.8+14.7). p < 0.05 –
Significantly more children with IQ lower than 70 (mental retardation) in
high-F area (4%), medium-arsenic area (3.3%), and high-arsenic area (8.3%) as
compared to control (0%).
|
|
Conclusion:
|
“This study indicates that exposure to fluoride in drinking
water is associated with neurotoxic effects in children.”
|
IQ Study #27: Trivedi (2007) |
|
|
Citation:
|
Trivedi TMH, Verma RJ, Chinoy NJ, Patel RS, Sathawara NG.
(2007). Effect of high fluoride water on intelligence of school
children in India. Fluoride 40(3):178-183.
|
|
Location of study:
|
INDIA. High F area:
Sachana, Sanand district, Gujarat; Medium F area: Chandlodia, Ahmedabad.
|
|
Size of study:
|
190 children (89 in high F area; 101 in medium F area)
|
|
Age of Subjects:
|
12-13 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High F area=5.55+0.41 mg/L
Medium F area=2.01+0.009 mg/L |
|
Urine Fluoride Levels:
|
High F area = 6.13+0.67 mg/L
Medium F area = 2.30+0.28 mg/L |
|
Confounding Factors:
|
(1) The study included only those children who were life-long
residents of the areas. respective location. (2) The areas have similar
nutritional status and both have middle class socioeconomic status (although
Sachana is slightly poorer). (3) Iodized salt is used in both areas.
|
|
Type of IQ Test
|
Questionnaire prepared by Prof. JH Shah; standardized on the
Gujarati population with 97% reliability rate in relation to the
Stanford-Binet Intelligence Scale
|
|
Results:
|
(A) Average IQ is lower in High-F area (91.72+1.13) than in Low-F area
(104.44+1.23), p<0.001. (B) High F area has 28.09% of children
with IQ below normal (over twice the percentage found in lower F area).
|
|
Conclusion:
|
“In agreement with other studies elsewhere, these
findings indicate that children drinking high F water are at risk for
impaired development of intelligence.”
|
IQ Study #26: Fan (2007) |
|
|
Citation:
|
Fan Z, Dai H, Bai A, Li P, Ro L, Li G, Zhang C, Li X.
(2007). The effect of high fluoride
exposure on the level of intelligence in children. Journal
of Environmental Health 24(10):802-03.
|
|
Location of study:
|
CHINA. Pucheng County,
Shaanxi Province.
|
|
Size of study:
|
79 children (42 children in High F area; 37 children in low F
area)
|
|
Age of Subjects:
|
7-14 years old
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
– High F area=3.15 mg/L
– Low F area=1.03 mg/L (water-improvement schemes implemented 14-18 years before study) |
|
Urine Fluoride Levels:
|
– High F area group=2.89+1.97 mg/L (range:
1.14-6.09 mg/L);
– Low F area group=1.78+0.46 mg/L (range: 1.33-2.35 mg/L) (non-significant difference, likely because F is consumed from various sources other than water) |
|
Confounding Factors:
|
(1) The two areas have common habits and lifestyles in terms
of cuisine, economy, culture, education, agricultural goods, etc.. (2) No
chemical factories in area. (3) The area does not have an iodine deficiency
problem.
|
|
Type of IQ Test
|
CRT-C2 intelligence module
|
|
Results:
|
(A) Average IQ in High-F area (96.11 + 12.00) is lower than Low-F area (98.41 + 14.75), although difference is not
statistically significant. (B) No child in High-F area has outstanding
or excellent intelligence. The respective rates in the Low-F area are 2.7%
and 5.4%, respectively.
|
|
Conclusion:
|
“Exposure to high levels of fluoride is likely to cause
a certain level of harm to a child’s level of intelligence.”
|
IQ Study #25: Seraj (2006) |
|
|
Citation:
|
Seraj B, Shahrabi M, Falahzadeh M, Falahzadeh F, Akhondi N.
(2006). [Effect of highfluoride concentration in drinking water on
children’s intelligence]. [Study in Persian] Journal
of Dental Medicine 19(2):80-86.
|
|
Location of study:
|
IRAN
|
|
Size of study:
|
126 children (85 children from low-F village, 41 children from
high-F village)
|
|
Age of Subjects:
|
Not provided in English abstract (full study is in Persian)
|
|
Source of Fluoride:
|
Water
|
|
Water Fluoride Levels:
|
High F village = 2.5 mg/L
Low F village = 0.4 mg/L |
|
Confounding Factors:
|
The history of illnesses affecting the nervous system, head
trauma, birth weight (>2.5kg or < 2.5kg),
residental history, age and sex of children were investigated by
questionnaires completed by the children’s parents.
|
|
Type of IQ Test
|
Raven’s
|
|
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).”
|
|
Statistical significance
|
““Based on the findings of this study, exposure of
children to high levels of fluoride may carry the risk of impaired
development of intelligence.”
|
IQ Study #24: Wang (2005) |
|
|
Citation:
|
Wang S, Zhang H, Fan W, Fang S, Kang P, Chen X, Yu M.
(2005). The effects of endemic
fluoride poisoning caused by coal burning on the physical development and
intelligence of children. Journal of Applied Clinical
Pediatrics 20(9):897-898 (republished in Fluoride 2008;
41:344-348).
|
|
Location of study:
|
CHINA. Zhijin County,
Ghizhou Province.
|
|
Size of study:
|
226 children (176 children in High F area, including 119
children with skeletal fluorosis and 57 children with only dental fluorosis; 50
children in low-F area without skeletal or dental fluorosis)
|
|
Age of Subjects:
|
7-12 years old
|
|
Type of Exposure:
|
Coal burning
|
|
Urine Fluoride Levels:
|
High F group=1.352+0.457 mg/L
(n=144)
Lower F group=1.611+0.467 mg/L (n=35) |
|
Confounding Factors:
|
(1) Both areas are free from iodine deficiency. (2) Both areas
have similar standard of living, sanitation, culture, and availability
of medical treatment.
|
|
Type of IQ Test
|
Raven’s Standard Theoretical Intelligence Test, Chinese
version
|
|
Results:
|
Children from high F (endemic) areas had lower IQ than those
from lower F (control) area (p<0.01). Negative correlation between urine F
and IQ (p<0.01).
|
|
Conclusion:
|
“High fluoride burden has a definite effect on the
intellectual and physical development of children.”
|
IQ Study #23: Xiang (2003a), Xiang, (2003b) |
|
|
Citation:
|
– Xiang Q, et al. (2003a). Effect
of fluoride in drinking water on children’s intelligence. Fluoride 36:
84-94. – Xiang Q, et al. (2003b).
Blood lead of children in Wamiao-Xinhuai intelligence study. Fluoride 36:
198-199.
|
|
Location of study:
|
CHINA. Sihong County,
Jiangsu Province.
|
|
Size of study:
|
512 children (222 children in high-F village, 290 children in
low-F village)
|
|
Age of Subjects:
|
8-13 years old
|
|
Type of Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High F village=2.47+0.79 mg/L (range=0.57-4.50 mg/L)
Low F village=0.36+0.15 mg/L (range=0.18-0.76 mg/L)In the high-F village, children were subdivided into the following five fluoride water levels:Group A<1.0 mg/L; Group B=1.0-1.9 mg/L; Group C=2.0-2.9 mg/L; Group D=3.0-3.9 mg/L; Group E>3.9 mg/L. |
|
Urine Fluoride Levels:
|
High F village=3.47+1.95 mg/L
Low F village=1.11+0.39 mg/L |
|
Confounding Factors:
|
(1) The two villages have similar urine iodine levels
(p>0.3), and blood lead levels (p>0.48). (2) Neither village has
fluoride pollution from burning coal or other industrial sources. (3) None of
the residents reported drinking brick tea. (4) Children who had been
absent from either village for 2 years or longer, or who had a history of
brain disease or head injury were excluded from study.
|
|
Type of IQ Test
|
CRT-RC (Combined Raven’s Test for Rural China)
|
|
Results:
|
(A) Mean IQ of high F village (92.02+13.00)
is lower than low F village (100.41+13.21),
p<0.01. (B) Higher drinking water F is significantly associated with
higher rates of mental retardation (IQ<70) and borderline intelligence (IQ=70-79),
p<0.05. (C) Children’s IQs are not related to urinary iodine, family
income, or parent’s education level.
|
|
Conclusion:
|
“In endemic fluorosis areas, drinking water fluoride levels
greater than 1.0 mg/L may adversely affect the development of children’s
intelligence.”
|
IQ Study #22: Li (2003) |
|
|
Citation:
|
Li Y, Jing X, Chen D, Lin L, Z Wang Z. (2003). Effects
of endemic fluoride poisoning on the intellectual development of children in
Baotou. Chinese Journal of Public
Health Management 19(4):337-338 (republished in Fluoride 2008;
41:161-64).
|
|
Location of study:
|
CHINA. Baotou, Inner
Mongolia.
|
|
Size of study:
|
936 children (720 children from high-F endemic area; 236 children
from low-F control area)
|
|
Age of Subjects:
|
6-13 years old
|
|
Source of F exposure:
|
Water
|
|
Fluoride exposure levels:
|
“The region classified as endemic was designated using the
1981 standards for designation of endemic regions laid out in 1981’s Standards
for Endemic Fluorosis Prevention and Treatment Work”
|
|
Type of IQ Test
|
Illustrated version of the Chinese Standardized Raven Test for
children in rural areas
|
|
Results:
|
(A) Average IQ of children in endemic area (92.07) somewhat
lower than that of control area (93.78), NS. (B) Rate of children with low IQ
(<69) greater in endemic area (10.38%) than in control area (4.24%) (“high
statistical significance”, but no p value given).
|
|
Conclusion:
|
“In our study, we found that the average IQ of children
in a fluoride endemic area was somewhat lower than the control, but the
result was not statistically significant (p > 0.05). The percentage of
children with fluorosis, however, was higher as compared to the control, and
this was very significant statistically.”
|
IQ Study #21: Shao (2003) |
|
|
Citation:
|
Shao Q, Wang Y, Li L, Li J. (2003). Study
of cognitive function impairment caused by chronic fluorosis. Chinese
Journal of Endemiology 22(4):336-38.
|
|
Location of study:
|
CHINA. Bijie City (high
F area) and Tongren area (control area), Guizhou Province.
|
|
Size of study:
|
88 adults (49 adults in High-F area; 39 adults in Low-F area)
|
|
Age of Subjects:
|
Aged 30-50 (High-F area = 42+6 years; Low-F
area = 43+6 years)
|
|
Source of Fluoride Exposure:
|
Water
|
|
Fluoride exposure levels:
|
Adults in high-F area diagnosed as suffering from fluoride
poisoning (as evident by dental and skeletal changes). Water F levels not
provided.
|
|
Confounding Factors:
|
Non-iodine deficient areas. Exclusions of mental disorders
caused by mental retardation, brain organic and somatic diseases. All
farmers. Similar distribution of age, sex, education level.
|
|
Type of IQ Test
|
Wechsler Adult Intelligence Scale test for Rural China
(WATS-RC); Associated learning (AL) test; Digit Span (DS) test; Similarity
test; Speech fluency test (SFT); Comprehension test.
|
|
Results:
|
(A) Significantly lower operation score on IQ test in high F
area (48-54) versus low F area (52-59), p < 0.01. (B) Lower total IQ score
in high F area (78-100, average) than in low F area (109-118, average-high),
although not statistically significant (C) High F subjects have
significantly lower scores on several of the performance tests (speech
fluency, recognition, similarity, p < 0.01, and digit span, p < 0.05),
and this correlates with elevated levels of oxidative stress.
|
|
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 [indices of oxidative
stress].”
|
IQ Study #20: Wang (2001) |
|
|
Citation:
|
Wang X, Wang L, Hu P, Guo X, Luo X. (2001). Effects
of high iodine and high fluorine on children’s intelligence and thyroid
function. Chinese Journal of
Endemiology 20(4):288-90.
|
|
Location of study:
|
CHINA. Binzhou and
Dezhou, Qingyun County, Shandong Province.
|
|
Size of study:
|
513 children (322 children from school in high iodine/high
fluoride area; 193 children from school in lower iodine/lower fluoride area).
|
|
Age of Subjects:
|
8-12 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
– High iodine/high fluoride area=2.97 mg/L – Lower
iodine/lower fluoride area=0.5 mg/L
|
|
Urine Fluoride Levels:
|
– High iodine/high fluoride = 3.08+1.03 mg/L – Low
iodine/low fluoride = 0.82+0.56 mg/L
|
|
Type of IQ Test
|
CRT-RC (Combined Raven’s Test for Rural China)
|
|
Results:
|
(A) Average IQ is lower in High-F area than in Low-F area
(76.67+7.75 vs. 81.67+11.97), although
the difference does not reach statistical significance. (B) The rate of
extremely low and borderline IQ is higher in the High F areas than in the Low
F areas (16.67% vs. 10% and 36.67% vs. 16.67, respectively), although these
differencese do not reach statistical significance.
|
|
Conclusion:
|
“High iodine and high fluorine have certain influence on
children’s intelligence and thyroid function.”
|
IQ Study #19: Hong (2001) |
|
|
Citation:
|
Hong F, Cao Y, Yang D, Wang H. (2001). Research
on the effects of fluoride on child intellectual development under different
environmental conditions. Chinese Primary Health Care 15(3):56-57
(republished in Fluoride 2008;
41(2):156–60).
|
|
Location of study:
|
CHINA. Wukang, Boxing,
and Zouping counties, Shangdong Province.
|
|
Size of study:
|
205 children (32 controls; 85 High F; 32 High-F/High Iodine;
28 High F/Low Iodine; 28 Low F/Low Iodine)
|
|
Age of Subjects:
|
8-14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
– Control area = 0.75 mg/L – High F only = 2.90 mg/L – High
F/High I = 2.85 mg/L – High F/Low I = 2.94 mg/L – Low F/Low I = 0.48 mg/L
|
|
Confounding Factors:
|
– Areas have same geographical features and standard of
living.
|
|
Type of IQ Test
|
Chinese Standardized Raven’s Test for Rural areas (CRT-R)
|
|
Results:
|
(A) Average IQ of High F/Low I group (68.38+19.12) and Low F/Low I group (75.53+6.92) is lower than control group (82.79+8.98), p<0.01. (B) IQ of High F/Low I group is
lower than Low F/Low I group, p<0.01. (C) Significant interaction exists
between High Fluoride and Low Iodine, p<0.01. (D) IQ ranking of high F
groups show significant deficits compared to control, p<0.01.
|
|
Conclusion:
|
“The IQ results of this study show no significant difference
between the average IQs of those children from the high fluoride only areas
and the high fluoride/high iodine areas, however the result from the high
fluoride/low iodine group show statistically significant differences as
compared to that of the low fluoride/low iodine group. In short, it appears
that the presence or lack of iodine is a more significant factor in both the
prevalence of goiter and average IQ.”
|
IQ Study #18: Lu (2000) |
|
|
Citation:
|
Lu Y, Sun L, Wu LN, Wang X, Lu W, Lis SS. (2000). Effect
of high-fluoride water on intelligence of children. Fluoride 33:74-78.
|
|
Location of study:
|
CHINA. Tianjin Xiqing
District.
|
|
Size of study:
|
118 children (60 children in High-F village; 58 children in
Low-F village)
|
|
Age of Subjects:
|
10-12 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
– High F village = 3.15+0.61 mg/L – Low F
village = 0.37+0.04 mg/L
|
|
Urine Fluoride Levels:
|
– High F village = 4.99+2.57 mg/L – Low F
village = 1.43+0.64 mg/L
|
|
Confounding Factors:
|
(1) Children included in the study are lifelong residents of
study area. (2) Villages have similar population size, social, economic and
educational backgrounds. (3) Children with congenital or acquired neurological
disorders were excluded.
|
|
Type of IQ Test
|
Chinese Combined Raven’s Test, Copyright 2 (CRT-C2)
|
|
Results:
|
(A) Average IQ of children from High F village (92.27+20.45) is lower than children from Low F village
(103.05+13.86), p<0.005. (B) More “retarded” (IQ=<70)
and “borderline” intelligence (IQ=70-79) children in high F group (21.6%)
than in low F group (3.4%), p<0.005. (C) Significant inverse relationship
exists between urinary F and IQ.
|
|
Conclusion:
|
“The findings of this study thus replicate those of
earlier studies and suggest that a real relationship exists between fluoride
exposure and intelligence.”
|
IQ Study #17: Zhang (1998) |
|
|
Citation:
|
Zhang J, Yao H, Chen Y. (1998). The
effect of high levels of arsenic and fluoride on the development of
children’s intelligence. Chinese
Journal of Public Health 17(2):119.
|
|
Location of Study:
|
CHINA. Kuitun region,
Urumqi.
|
|
Size of Study:
|
164 children
|
|
Age of Subjects:
|
4-10 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
For the 4 to 8 year olds, the fluoride level their entire life
(including during fetal development) was between 0.49 and 0.81 ppm. The 9
year olds were exposed to high fluoride (level not provided) during fetal
development. The 10 year olds were exposed to high fluoride during fetal
development and their first year of life.
|
|
Type of IQ Test:
|
50-point evaluation tests created by Japanese
researcher, Shigeo Kobayashi
|
|
Results:
|
No difference in IQ among the 4 to 8 year olds, a slight
(non-significant) reduction in IQ among the 9 year olds (who were exposed to
fluoride during fetal development), and a significant reduction among the 10
year olds (who were exposed during fetal development and their first year of
life).
|
|
Conclusion:
|
“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.”
|
IQ Study #16: Yao (1997) |
|
|
Citation:
|
Yao L, Deng Y, Yang S, Zhao J, Wang X, Cui Z. (1997). Comparative
assessment of the physical and mental development of children in endemic
fluorosis area with water improvement and without water improvement. Literature
and Information on Preventive Medicine 3(1):42-43.
|
|
Location of study:
|
CHINA. Chaoyang City,
Liaoning Province.
|
|
Size of study:
|
823 children (326 children from fluorosis area with water
improvement; 183 children from fluorosis area without water improvement; 314
children from non-fluorosis area)
|
|
Age of Subjects:
|
7-14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
– Fluorosis area without water improvements = 2.0 mg/L-
Fluorosis with water improvements = 0.33 mg/L (prior to improvement 8 years
before study, the F level was 2.0 mg/L)- Non-fluorosis area = 0.4 mg/L
|
|
Confounding Factors:
|
– All children born locally.
– Areas in study have adequate iodine
exposure and similar levels of economic development, living conditions,
school size, and number of teachers.
|
|
Type of IQ Test
|
CRT-RC (Combined Raven’s Test for Rural China)
|
|
Results:
|
(A) Children in fluorosis area (without water improvement)
have lower average IQ than children in fluorosis area (with water
improvement) for all age groups, p<0.01. (B) Children in fluorosis area
without water improvement have lower average IQ than children in
non-fluorosis area for all age groups, p<0.01. (C) Children born prior to
water improvement program in fluorosis area with water improvement have lower
average IQ than children in non-fluorosis area, p<0.05. (D) No significant
difference in intelligence exists between children born after water
improvement and children in non-fluorosis area.
|
|
Conclusion:
|
“These results show that water improvement and defluoridation
can improve the mental and physical development of children in a fluorosis area.“
|
IQ Study #15: Yao (1996) |
|
|
Citation:
|
Yao L, Zhao J, Wang X, Cui Q, Lin F. (1996). Analysis
on TSH and intelligence level of children with dental Fluorosis in a high
fluoride area. Literature and Information on
Preventive Medicine 2(1):26-27.
|
|
Location of study:
|
CHINA. Chaoyang City,
Liaoning Province.
|
|
Size of study:
|
536 children (78 children from high-fluorosis area; 188
children from light-fluorosis area; 270 children from non-fluorosis area)
|
|
Age of Subjects:
|
8-12 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High-F area: <11 mg/L Low-F
area: 2.0 mg/L Control area: 1.0 mg/L
|
|
Confounding Factors:
|
(1) Children in each of the three areas have adequate iodine
exposure as determined through urine analysis. (2) The three areas have
similar economic development, schools, and teachers.
|
|
Type of IQ Test
|
Raven test—Associative Atlas (Version of Chinese village)
|
|
Results:
|
(A) Average IQ of children with dental fluorosis in
high-fluorosis area and light-fluorosis areas is lower than children in
non-fluorosis area, p<0.01. (B) Average IQ of children with dental
fluorosis from high-fluorosis area is lower than those from light-fluorosis
area, p<0.05. (C) Rate of high IQ (>120) is lower in high-fluorosis
area (3.85%) and light-fluorosis area group (6.91%) than non-fluorosis area
(10.74%) (no p value given).
|
|
Conclusion:
|
“The results of the intelligence tests show that a high level
of fluoride influences children’s IQ, which is consistent with some previous
data. It is worth mentioning that the higher the degree of dental fluorosis,
the more negative the impact on the children’s intelligence level. This is an
issue which merits utmost attention.”
|
IQ Study #14: Zhao (1996) |
|
|
Citation:
|
Zhao L, Liang G, Zhang D, Wu X. (1996). Effect
of high-fluoride water supply on children’s intelligence. Fluoride 29:
190-192.
|
|
Location of study:
|
CHINA. Shanxi Province.
|
|
Size of study:
|
320 children (160 children from high-F village; 160 children
from lower-F village)
|
|
Age of Subjects:
|
7-14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High-F village = 4.12 mg/L Lower-F village = 0.91 mg/L
|
|
Confounding Factors:
|
(1) Similar occupations, living standards, and social customs
in the two villages. (2) Only children whose mothers lived in the
village during pregnancy were included in study. (3) Parents’ educational
level was determined (and found to have a significant influence on IQ, p <
0.01).
|
|
Type of IQ Test
|
“Official intelligence quotient (IQ) tests lasting 40 minutes”
|
|
Results:
|
Children in High-F village have significantly lower average IQ
(97.69+13.00) than children in lower-F village (105.21+14.99), p<0.01.
|
|
Conclusion:
|
“The results of this study indicate that intake of
high-fluoride drinking water from before birth has a significant deleterious
influence on children’s IQ in one of two similar villages.”
|
IQ Study #13: Wang (1996) |
|
|
Citation:
|
Wang G, et al. (1996). A study of the IQ levels of
four- to seven-year-old children in high fluoride areas. Endemic
Diseases Bulletin 11(1):60-6 (republished in Fluoride 2008;
41:340–43).
|
|
Location of study:
|
CHINA. Shehezi, Xinjiang
Province.
|
|
Size of study:
|
230 children (147 children from High-F village; 83 children
from Low-F village)
|
|
Age of Subjects:
|
4-7 years old
|
|
Source of Fluoride Exposure:
|
Water & Coal-Burning
|
|
Water Fluoride Levels:
|
– All wells = 0.58-8.60 mg/L – High F area = > 1.0 mg/L –
Low F area = < 1.0 mg/L
|
|
Confounding Factors:
|
(1) Children were excluded from study if they had a low
intellectual ability due to genetic inheritance, past illness, malnutrition,
uses of medication, or other reasons. (2) “Significantly greater” percentage
of children with below average head circumference in High F area (18.37%)
than in Control area (9.64%) (no p value given).
|
|
Type of IQ Test
|
Wechler Preschool and Primary Scale of Intelligence (WPPSI)
|
|
Results:
|
(A) Average Total IQ in High F group (95.64+14.34) is lower than in control group (101.23+15.84), p<0.05. (B) Average Performance IQ in
High F group (94.33+14.76) is lower than in Control
group (101.77+18.12), p<0.01. (C) Average
Verbal IQ is not significantly different. (D) In High F area, children with
below-normal head circumference have lower average IQ (89.07+15.69) than those with normal head circumference
(97.13+8.06), p<0.01.
|
|
Conclusion
|
“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.”
|
IQ Study #12: Duan (1995) |
|
|
Citation:
|
Duan J, Zhao M, Wang L, Fang D, Wang Y, Wang W. (1995). A
comparative analysis of the results of multiple tests in patients with
chronic industrial fluorosis. Guizhou
Medical Journal 18(3):179-180.
|
|
Location of study:
|
CHINA. Guiyang, Guizhou
Province.
|
|
Size of study:
|
157 adults (72 adults with diagnoses with industrial
fluorosis; 43 adults exposed to occupational fluoride but without industrial
fluorosis; 42 non-exposed workers)
|
|
Age of Subjects:
|
35 to 62 yrs
|
|
Source of Fluoride Exposure:
|
Occupational exposures
|
|
Air Fluoride Levels
|
Avg = 2.21 mg/m3
|
|
Confounding Factors:
|
Non-exposed workers had similar work conditions, economic
status, and lifestyle habits.
|
|
Type of IQ Test
|
Wechsler Adult Intelligence Scale revised by Prof Gong Yaoxian
of Human Medical Sciences University (WAIS-RC)
|
|
Results:
|
Average IQ of workers with industrial fluorosis was
significantly lower (68 to 72) than fluoride-exposed workers without
industrial fluorosis (84.5), and IQ of fluoride-exposed workers without
fluorosis (84.5) was significantly lower than IQ of non-exposed workers
(99.4).
|
|
Conclusion:
|
“it may be determined that industrial fluorine poisoning has
gradually progressive effects on the normal function and metabolism of the
adult brain and other aspects of the nervous system. With the progression of
the course of fluorosis, neurological damage gradually worsens, with the
degree of damage closely related to the length of exposure to fluorine, nail
fluorine content, and other factors. Damage from high concentrations of
fluorine not only affects bones and ligaments, tendons, and other soft
tissue, but is also quite widespread throughout the entire nervous system.
This is of major significance for worker protection and other areas.”
|
IQ Study #11: Li (1995) |
|
|
Citation:
|
Li X, Zhi J, Gao R. (1995). Effect
of fluoride exposure on intelligence in children. Fluoride 28:189-192.
|
|
Location of study:
|
CHINA. Anshu and Zhijin
counties, Guizhou Province.
|
|
Size of study:
|
907 children (230 children from severe fluorosis area; 224
children from medium fluorosis area; 227 children from slight fluorosis area;
226 children from non-fluorosis area)
|
|
Age of Subjects:
|
8-13 years old
|
|
Source of Fluoride Exposure:
|
Coal burning
|
|
Urine Fluoride Levels
|
– Severe dental fluorosis = 2.69 mg/L – Medium dental
fluorosis = 2.01 mg/L – Slight dental fluorosis = 1.81 mg/L – No dental
fluorosis = 1.02 mg/L
|
|
Confounding Factors:
|
(1) All children of Han nationality.(2) Children were excluded
from study if they had congenital or acquired diseases “not related to
fluoride.” (3) Groups separated by intervals of 6 months in age.
|
|
Type of IQ Test
|
China Rui Wen’s Scaler for Rural Areas
|
|
Results:
|
Average IQ of children in severe (80.3+12.9) and medium (79.7+12.7) fluorosis
areas is lower than the slight (89.7+12.7) and
non-fluorosis (89.9+10.4) areas, p<0.01.
|
|
Conclusion:
|
“A high fluoride intake was associated with a lower
intelligence.”
|
IQ Study #10: Xu (1994) |
|
|
Citation:
|
Xu Y, Lu C, Zhang X. (1994). The
effect of fluorine on the level of intelligence in children. Endemic
Diseases Bulletin 9(2):83-84.
|
|
Location of study:
|
CHINA. Shandong
Province.
|
|
Size of study:
|
330 children (8 groups of 21-97 children categorized based on
fluoride and iodine content of water)
|
|
Age of Subjects:
|
8-14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
– High Fluoride/High Iodine = 3.9 mg/L – High Fluoride/Low
Iodine = 2.0 mg/L – High Fluoride = 1.8 mg/L – Low Fluoride = 0.38-0.5
mg/L – Control Area = 0.8 mg/L
|
|
Confounding Factors:
|
(1) Water iodine level used as variable. (2) Child’s
pre-school education history was determined. (3) Parent’s literacy was
determined.
|
|
Type of IQ Test
|
Bient-Siman
|
|
Results:
|
(A) Children in areas with high-fluoride and low-iodine have
significantly lower IQs than children in areas with high-fluoride and
high-iodine, p < 0.01. (B) More children have low IQ (< 69) in areas
with High F/High I (10.53%), High F only (7.32%), and High F/Low I (12.82%)
than in control group (1.61%)
|
|
Conclusion:
|
“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. . . . This could be demonstrative of the fact that
fluoride acts to increase the toxicity and worsen the occurrence of thyroid
swelling.”
|
IQ Study #9: Li (1994) |
|
|
Citation:
|
Li Y, Li X, Wei S. (1994). Effects
of high fluoride intake on child mental work capacity: Preliminary
investigation into the mechanisms involved. Journal
of West China University of Medical Sciences 25(2):188-91
(republished in Fluoride 2008;
41:331-35).
|
|
Location of study:
|
CHINA. Sichuan Province.
|
|
Size of study:
|
158 children from two neighboring townships (107 children with
various degrees of dental fluorosis; 51 children with no dental fluorosis)
|
|
Age of Subjects:
|
12-13 years old
|
|
Source of Fluoride Exposure:
|
Food contaminated by coal smoke
|
|
Fluoride Content of Grain:
|
– Children with no dental fluorosis = 0.5 mg/kg- Children with
dental fluorosis (HiF1) = 4.7 mg/kg- Children with dental fluorosis (HiF2) =
5.2 mg/kg- Children with dental fluorosis (HiF3) = 31.6 mg/kg
|
|
Confounding Factors:
|
(1) The areas have similar levels of fluoride in water (0.3
mg/L) and air (0.02-0.51 mg/m3) and similar levels of zinc in soil. (2) The
areas townships have similar economic and cultural status, lifestyle, dietary
habits, basic constituents of food. (3) Age, gender, and grade level of the
children are kept “as constant as possible.” (4) Children with acute or
chronic diseases not related to fluoride were excluded from study.
|
|
Type of IQ Test
|
Mental Work Capacity determined by number of letters found
(NLF), rate of error (RE), index of mental capacity (IMC), short-term memory
capacity (SMC), visual reaction time (RT).
|
|
Results:
|
(A) Children with dental fluorosis in mid-exposure group
(HiF2) have reduced short-term mental capacity (p<0.05), reduced mental
capacity index (p < 0.01), and reduced NLF scores (p<0.01) as compared
to children with no fluorosis and children with lower exposure.(B) Children
with dental fluorosis in high-exposure group (HiF3) have reduced short-term
mental capacity (p<0.01), reduced mental capacity index (p < 0.01), and
reduced NLF scores (p<0.01) as compared children with no fluorosis and
children with low exposure.
|
|
Conclusion:
|
“As shown in this study, the mental work capacity (MWC) of the
two groups of children with grade 3 dental fluorosis was lower than the two
groups with no dental fluorosis. . . . This indicates that early, long-term
exposure to excess fluoride causes deficits in memory, attention, and
reaction time, but 12–13 year-old children with only recent exposure show no
major effects. Studies [on human fetuses] have already shown that the
developing brain is one of the ripest targets for disruption by fluoride
poisoning. Given that before six years of age the human brain is in its
fastest stage of development, and that around seven and eight basic
structural development is completed, therefore the brain is most vulnerable
to damage from excess fluoride intake before this age.”
|
IQ Study #8: Yang (1994) |
|
|
Citation:
|
Yang Y, Wang X, Guo X, Hu P. (1994). The
effects of high levels of fluoride and iodine on intellectual ability and the
metabolism of fluoride and iodine. Chinese
Journal of Epidemiology 15(4):296-98 (republished in Fluoride 2008;
41:336-339).
|
|
Location of study:
|
CHINA. Shandong
Province.
|
|
Size of study:
|
60 children (30 from high-F village, 30 from Low-F village)
|
|
Age of Subjects:
|
8-14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High F/High Iodine area = 2.97 mg/L Control area = 0.5 mg/L
|
|
Urine Fluoride Levels:
|
High F/High Iodine area = 2.08+1.03 mg/L Control
area = 0.82+0.56 mg/L
|
|
Type of IQ Test
|
Chinese Comparative Scale of Intelligence Test
|
|
Results:
|
(A) Children in high F/high iodine area have lower IQ
(76.67+7.75) than those in low F area (81.67+11.97), although the difference
is not statistically significant.(B) Greater percentage of children have
moderately low IQ (<79) in High F/High Iodine
area (76.67%) than in control area (36.67%), p<0.01.
|
|
Conclusion:
|
“An excess of fluoride and a lack of iodine in the same
environment has been shown to have a marked effect on child intellectual
development, causing a more significant intellectual deficit than lack of
iodine alone.”
|
IQ Study #7: An (1992) |
|
|
Citation:
|
An J, Mei S, Liu A, Fu Y, Wang Q, Hu L, Ma L. (1992). 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.
|
|
Location of study:
|
CHINA. Xingshunxi Town,
Guyang County, Inner Mongolia (4 neighboring villages with high fluoride
centered around Wubu Ziyao village and 6 neighboring villages with lower
fluoride centered around Hada Heshao Village).
|
|
Size of study:
|
242 children (121 children from high-F villages and 121
children from the low-F villages)
|
|
Age of Subjects:
|
7-16 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High-F villages = 2.1+7.6 mg/L Control
villages = 0.6+1.0 mg/L
|
|
Confounding Factors:
|
(1) Dental fluorosis rates were determined in both areas
(90.9% in High-F area vs. 21.5% in Low-F area). (B) Both areas are in the
countryside, are 15 km from each other, and share the same Han ethnicity. (C)
The geography, culture, education, living standard, and social economic
conditions are “very similar.”
|
|
IQ Test:
|
Wechsler Intelligence Scale for Children
|
|
Results:
|
(A) Children in the High-F villages have significantly lower
IQs at each age group studied: 7-10 (p < 0.02); 11-13 (p < 0.01); 14-16
(p < 0.03); 7-16 (p < 0.01). (B) Significantly more children in High-F
villages have “critical state” IQ, p < 0.01. (C) When children within the
High-F villages are stratified into highest-F (5.2-7.6 mg/L), and lowest-F
levels (2.1-3.2 mg/L), the children in the higher-F areas had significantly
lower IQ than the lower-F areas (p < 0.05).
|
|
Conclusion
|
“The results show that the level of intelligence of primary
and secondary students from the high fluoride area and that of primary and
secondary students from the non-high fluoride area had very significant
differences, proving that high fluoride has adverse effects on the mental
development of students. The higher the water fluoride is, the lower the
level of IQ.”
|
IQ Study #6: Lin (1991) |
|
|
Citation:
|
Lin FF, Aihaiti, Zhao HX, Lin J, Jiang JY, Malmaiti, and
Aiken. (1991). 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 Vol. 7(3):24-25).
|
|
Location of study:
|
CHINA. Hetian
prefecture, Xinjiang.
|
|
Size of study:
|
749 children (250 children in High-F/Low Iodine area; 256
children in Low-F/Low-Iodine area; and 243 children in Low F/Low Iodine area)
|
|
Age of Subjects:
|
7-14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High F/Low Iodine = 0.88 mg/L Low F/Low Iodine = 0.34 mg/L
Control area = n/a
|
|
Urine Fluoride Levels:
|
High F/Low Iodine = 2.56 mg/L Low F/Low Iodine = 1.34-1.61
mg/L Control area = 1.6 mg/L
|
|
Confounding Factors:
|
(1) Lower socioeconomic status in all areas. (2) Areas have
similar nationalities, habits, customs, and income.
|
|
IQ Test:
|
CRT-RC (Combined Raven’s Test for Rural China)
|
|
Results:
|
Children from the High F/Low Iodine area have significantly
lower IQs (IQ=71) than children from the Low F/Low Iodine area (IQ=77-79;
p<0.05), and control area (IQ=96); p<0.01).
|
|
Conclusion:
|
“The significant differences in IQ among these regions
suggests that fluoride can exacerbate central nervous lesions and somatic
developmental disturbance caused by iodine deficiency.”
|
IQ Study #5: Guo (1991) |
|
|
Citation:
|
Guo X, Wang R, Cheng C, Wei W, Tang L, Wang Q, Tang D, Liu G,
He G, Li S. (1991). A preliminary investigation
of the IQs of 7-13 year old children from an area with coal burning-related
fluoride poisoning. Chinese Journal of
Endemiology 10(2):98-100 (republished in Fluoride 2008;
41(2):125–28).
|
|
Location of study:
|
CHINA. Xinshao County,
Hunan Province.
|
|
Size of study:
|
121 children (60 children with mild to severe fluorosis from
an endemic area where coal is used as a fuel source; 61 children from a
non-endemic area where wood is used as a fuel source)
|
|
Age of Subjects:
|
7 to 13 years old
|
|
Source of Fluoride Exposure:
|
Coal burning (Fluoride levels in water < 0.5 mg/l in
both areas)
|
|
Blood Fluoride Levels:
|
Endemic area=0.1483+0.0473 mg/L Non-endemic
area=0.1044+0.0652 mg/L (p<0.01)
|
|
Confounding Factors:
|
The two areas are neighboring townships with “very similar”
economies, cultures, living standards, lifestyles, public health,
and education.
|
|
IQ Test:
|
Chinese Binet IQ Test
|
|
Results:
|
(A) Children from endemic fluorosis area have lower average IQ
(76.7) than children in non-endemic area (81.4), p<0.05. (B) A greater
percentage (30%) of children in endemic area have low IQ (<69) than in non-endemic area (11.5%), p<0.05.
|
|
Conclusion:
|
“In summary, although diminished intellectual ability
can result from a multitude of factors (both innate and acquired) that
influence neural development and cell division in the cerebrum, the
comparison conducted in this study of two areas where the other environment
factors are basically the same shows clear differences in IQ, and it [is]
probable that this difference is due to a high fluoride environment.”
|
IQ Study #4: Chen (1991) |
|
|
Citation:
|
Chen Y, Han F, Zhou Z, Zhang H, Jiao X, Zhang S, Huang M,
Chang T, Dong Y. (1991). Research on the
intellectual development of children in high fluoride areas. Chinese
Journal of Control of Endemic Diseases 6(Suppl):99-100
(republished in Fluoride 2008;
41:120–24).
|
|
Location of study:
|
Linyi County, Shanxi Province, China
|
|
Size of study:
|
CHINA. 640 children (320
children from High-F village; 320 children from Lower-F village)
|
|
Age of Subjects:
|
7 to 14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High-F village = 4.55 mg/L Lower-F village = 0.89 mg/L
|
|
Confounding Factors:
|
The occupations, culture, standard of living, lifestyle
habits, access to health and transportation facilities are “essentially the
same” between the two areas.
|
|
IQ Test:
|
Rural version of Chinese Standardized Raven Test
|
|
Results:
|
Average IQ of children in High-F village (100.24+14.52) significantly lower than children in lower-F
village (104.03+14.96), p<0.01.
|
|
Conclusion:
|
“The results of this study indicate that there is significant
difference between the intellectual ability of the 7–14 year old children
from the [fluorosis] endemic area and those of the control, and moreover that
the average IQ of the children from the endemic area is clearly lower.”
|
IQ Study #3: Sun (1991) |
|
|
Citation:
|
Sun M, et al. (1991). Using drawing tests to
measure intelligence in children from areas impacted by combined Al-F endemic
toxicosis (Shuicheng, Guizhou). Journal
of Guiyang Medical College 16(3):204-06.
|
|
Location of study:
|
CHINA. Guizhou Province:
Liupanshui City (endemic fluorosis area) and Guiyang City (non-endemic area)
|
|
Size of study:
|
420 children (196 children from endemic fluorosis area; 224
children from non-endemic area)
|
|
Age of Subjects:
|
6.5-12 years old
|
|
Source of Fluoride Exposure:
|
N/A
|
|
Fluoride exposure levels:
|
N/A
|
|
Confounding factors:
|
(1) Majority of children of farmers. (2) Children with bone
and joint deformities or nervous system symptoms were excluded from study.
|
|
IQ Test:
|
Drawing test for children (Japanese researcher’s Shigeo
Kobayashi’s 50-point scoring method).
|
|
Results:
|
Children from endemic fluorosis area had lower IQ than those
from non-endemic area at all ages except <7 (p <
0.05)
|
|
Excerpt:
|
“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.”
|
IQ Study #2: Qin (1990) |
|
|
Citation:
|
Qin LS, Cui SY. (1990). Using the Raven’s standard
progressive matrices to determine the effects of the level of fluoride in
drinking water on the intellectual ability of school-age children. Chinese
Journal of the Control of Endemic Diseases 5(4):203-04
(republished in Fluoride 2008;
41:115–19).
|
|
Location of study:
|
CHINA. Jing County,
Hubei Province.
|
|
Size of study:
|
447 children (141 children from High-F area; 159 children from
“normal” F area; 147 children from low-F area)
|
|
Age of Subjects:
|
9 to 10.5 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Water Fluoride Levels:
|
High F = 2.1-4.0 mg/L“Normal” F = 0.5-1.0 mg/LLow F = 0.1-0.2
mg/L
|
|
Confounding factors:
|
All children had grown up drinking well water in their home
village.
|
|
IQ Test:
|
Raven’s Standard Progressive Matrices
|
|
Results:
|
Children in High F (21.17%) and Low F (23.03%) areas had lower
average IQ scores than children in normal F area (28.14%), p<0.01.
|
|
Conclusion:
|
“All of these finding serve to indicate that both high and low
fluoride can affect the normal development and function of the cerebrum as
well as the entire nervous system causing a decrease in intellectual ability.”
|
IQ Study #1: Ren (1989) |
|
|
Citation:
|
Ren D, Li K, Liu D. (1989). A
study of the intellectual ability of 8-14 year-old children in high fluoride,
low iodine areas. Chinese Journal of Control of
Endemic Diseases 4(4):251 (republished in Fluoride 2008;
41:319-20).
|
|
Location of study:
|
CHINA. Shandong
Province.
|
|
Size of study:
|
329 children (160 children in High F/low Iodine area: 169
children in Low-F/Low Iodine area)
|
|
Age of Subjects:
|
8 to 14 years old
|
|
Source of Fluoride Exposure:
|
Water
|
|
Fluoride exposure levels:
|
N/A
|
|
Confounding factors:
|
Both study groups had low iodine intake.
|
|
IQ Test:
|
Wechsler Intelligence Test
|
|
Results:
|
– Average IQ of children in the High Fluoride/Low Iodine group
(IQ=64.8) significantly lower than the children in the Low Fluoride/Low
Iodine group (IQ = 85.0), p<0.01.- The percentage of children with low IQ
(<69) significantly greater in High F/Low Iodine group (40.6%) than in Low
Fluoride/Low Iodine group (13.6%), p<0.01.
|
|
Conclusion:
|
“From the results it is evident that disrupted child
intellectual development is among the effects on the human body from a
harmful environment containing both high fluoride and low iodine, and this
disruption is clearly much more serious than the effects of iodine deficiency
alone.”
|
.
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