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Effect of high fluoride water on intelligence of school children in India

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Abstract and Figures

The intelligence quotient (IQ) was measured in 190 school-age children, 12-13 years old, residing in two village areas of India with similar educational and socioeconomic conditions but differing in fluoride (F) concentration in the drinking water. The children in the high F area (drinking water F 5.5510.41 mg/L) had higher urinary F levels (6.13± 0.67 mg/L) than the children in the lower F area (drinking water F 2.01±0.09 mg/L; urinary F levels 2.30±0.28 mg/L). The mean IQ score of the 89 children in the high F area was significantly lower (91.7211.13), than that of the 101 children in lower F area (104.44±1.23). A significant inverse relationship was also present between IQ and the urinary F level. In agreement with other studies elsewhere, these findings indicate that children drinking high F water are at risk for impaired development of intelligence.
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Research report
Fluoride 40(3)178–183
July-September 2007
Effect of high F water on children’s intelligence in India
Trivedi, Verma, Chinoy, Patel, Sathawara 178178
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MH Trivedi,a RJ Verma,a NJ Chinoy,a† RS Patel,b NG Sathawarac
Ahmedabad, India
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Keywords: Fluoride in drinking water; India school children; Intelligence quotient; Urinary
fluoride.
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According to current research findings, fluoride (F) produces neuronal
dysfunction and synaptic injury by a mechanism that involves free radical
production and lipid peroxidation.1-4 A recent study revealed that a high F level in
drinking water depressed learning-memory ability of brain in Wistar rats,5 in
agreement with earlier findings of Mullenix et al. showing that F exposure caused
a common pattern of sex and dose-specific behavioral deficits in rats.6 Brain
histology of NaF-intoxicated rabbits revealed loss of molecular layer and glial cell
layer, and Purkinje neurons exhibited chromatolysis and acquired a ‘ballooned’
appearance.7 Reduction and even complete loss of Nissl substance was observed
in rabbit7 and rat8 brain.
In recent studies in our laboratory, we found a significant dose-dependent
reduction in DNA, RNA, and proteins in the cerebral hemisphere, cerebellum, and
medulla oblongata regions of the brain in mice.9-10 In related work, Wang and co-
workers11 recorded evidence of DNA damage in brain cells of adult rats exposed
to high F and low iodine. Effects of F on the thyroid gland and its function have
also been studied.12-14 Moreover, animal experiments on the effect of high F and
low iodine on biochemical indexes and the antioxidant defense of the brain have
revealed decreased learning-memory in offspring rats.15-16
An association of high F in drinking water with lower intelligence in children in
China has been reported by Li et al.17 Earlier, Xiang et al.18 determined a
benchmark concentration-response relationship between IQ <80 and the F level in
aFor Correspondence: RJ Verma, Department of Zoology, University School of Sciences,
Gujarat University, Ahmedabad-380 009, Gujarat, India, E-mail: ramtejverma2000@yahoo.com;
bProfessor and Head, Dean Department of Education, University School of Psychology,
Philosophy & Education, Gujarat University, Ahmedabad-380 009, India.
cAsst. Director, Department of Hygiene, N.I.O.H (National Institute for Occupational Health),
Meghani Nagar, Ahmedabad-380 016, India. Deceased May 8, 2006.
Research report
Fluoride 40(3)178–183
July-September 2007
Effect of high F water on children’s intelligence in India
Trivedi, Verma, Chinoy, Patel, Sathawara 179179
drinking water was 2.32 mg F/L, and the lower-bound confidence limit was 1.85
mg F/L. By contrast, Spittle et al.19 found no trend for IQ to decline in children
drinking artificially fluoridated for seven years in an area of South Island, New
Zealand. Nevertheless, other studies indicate that exposure to increased levels of F
are associated with lower IQ.20-21 In India, both iodine deficiency disorders and
fluorosis due to excessive consumption of F cause two prevalent endemic diseases
that coexist in certain regions in the country.22 However, the majority of studies
that show a correlation between lower IQ and elevated F intake are from China,
and no such studies that we are aware of have been reported from India.
The aim of the present investigation was to examine F exposure of two groups of
school children and its impact on their intelligence quotients.
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Our study was undertaken on 190 school-age children in the 6th and 7th standard
(12–13 years old) of the lower F area of Chandlodia, Ahmedabad (101 students),
and the high F area of Sachana (89 students), in the Sanand district of Gujarat,
India. The children were life-long residents of their respective locations with only
one school in each area. The nutritional and middle class socioeconomic status of
both areas is very similar and good, but slightly lower in Sachana. Iodized salt is
used in both areas.
The intelligence quotient (IQ) was measured in the children of both areas by
using a questionnaire prepared by Professor JH Shah, copyrighted by Akash
Manomapan Kendra, Ahmedabad, India, and standardized on the Gujarati
population with 97% reliability rate in relation to the Stanford-Binet Intelligence
Scale.23 Before the students were allowed to open the questionnaire, the
examiners gave a friendly explanation of the important instructions to avoid
mental stress for those taking the test. Questions were related to the educational
background of the children, and the test had to be completed in 8 min under the
supervision of examiners.
Scores were ranked as: mental retardation (IQ <70), borderline (IQ 70–79), dull
normal (IQ 80–89), normal (IQ 90–109), bright normal (IQ 110–119), superior (IQ
120–129), and very superior (IQ >129).18
The drinking water and urine samples of the children of both areas were
collected in plastic bottles, stored under refrigeration, and used for the
measurement of F using an ion selective electrode (Orion research, USA. Model
no 96-09).
Values are expressed as Mean±SEM. Student’s t test was used for statistical
analysis of the data, and values of p<0.05 were considered significant.
,!1+*$1
As seen in Table 1, mean urinary F levels were significantly higher in the
children living in the area where the F content in drinking water was high
compared to the area where it was much lower.
Research report
Fluoride 40(3)178–183
July-September 2007
Effect of high F water on children’s intelligence in India
Trivedi, Verma, Chinoy, Patel, Sathawara 180180
Table 2 shows that the mean IQ of the 89 children in the high F water area of
Sachana was 12.2 percent lower than the mean IQ of the 101 children in the lower
F area of Chandlodia, which is highly significant. Significant differences between
the IQ of male and female children within each of the two areas were also found.
As seen in Table 3 and illustrated in the Figure, the IQ of nearly half the children
in the lower F area of Chandlodia was in the normal range of 90 to 109. The IQ of
38.61% the children in this village area was above the normal range, and only
11.88% were below the normal range. On the other hand, the IQ of a much larger
percentage of the children in the high F area of Sachana was in the normal range,
and only 2.25% were above that range, with none with an IQ above 119.
Moreover, in Sachana the IQ of 28.09% of the children was below the normal
range—over twice the percentage found in Chandlodia.
$DT:6%IV Drinking water and urinary F level of children living in lower F Chandlodia and high F Sanacha (Mean ± SEM)
Area Number of children
examined
Level of F in drinking water
(mg/L)
Urinary F level
(mg/L)
Chandlodia,
Ahmedabad District
101 2.01 ± 0.009 2.30 ± 0.28
Sanacha, Sanand District 89 5.55 ± 0.41* 6.13 ± 0.67*
*p<0.001 (Compared to lower F level).
$DT:6%NV IQ scores of school children (numbers in parenthesis) living in lower F Chandlodia
and high F Sachana (Mean ± SEM)
Group Chandlodia, Ahmedabad Sachana, Sanand
Total
104.44 ± 1.23 (101) 91.72 ± 1.13** (89)
According to gender
Male (Total 6th/7th) 104.80 ± 1.47 (62) 90.24 ± 1.58** (56)
Female (Total 6th/7th) 103.87 ± 2.21 (39) 94.15 ± 1.35 (33)
According to gender and grade level
6th Standard
Male 105.22 ± 2.45 (31) 96.25 ± 2.73 (20)
Female 105.55 ± 2.95 (18) 93.35 ± 2.23 (14)
7th Standard
Male 104.38 ± 1.67 (31) 86.70 ± 1.70** (36)
Female 102.42 ± 3.27 (21) 94.73 ± 1.72* (19)
*p<0.05; p<0.01; **p<0.001 (compared to higher IQ group).
$DT:6%PV IQ distribution in children in lower F Chandlodia and high F Sachana
Chandlodia Sachana
IQ
Male Female Total % Male Female Total %
!130 2 0 2 1.98 0 0 0 0
120–129 2 1 3 2.97 0 0 0 0
110–119 22 12 34 33.66 2 0 2 2.25
90–109 31 19 50 49.50 35 27 62 69.66
80–89 5 4 9 8.91 10 4 14 15.73
70–79 0 2 2 1.98 6 2 8 8.99
"69 0 1 1 0.99 3 0 3 3.37
Total 62 39 101 100 56 33 89 100
Research report
Fluoride 40(3)178–183
July-September 2007
Effect of high F water on children’s intelligence in India
Trivedi, Verma, Chinoy, Patel, Sathawara 181181
-(1#+11(&0
This study indicated that the mean IQ level of students exposed to high F
drinking water was significantly lower than that of the students exposed to a lower
F level drinking water. Because the kidney is the principal organ for the excretion
of F, the rate or degree of exposure to F was checked by analyzing the urinary F
level.22 In high F Sachana, more children had IQ scores below the normal 90–109
range than in lower F Chandlodia, where more children scored above the normal
level. It thus appears that elevated F exposure depressed higher levels of
intelligence even more than it affected normal and below normal intelligence of
the children. Overall, the difference in mean IQ between the two groups was
12.2%, which, statistically, is highly significant. The normal IQ range for these
areas is 100–110.23
The biomechanism of the action of F in reducing IQ is not clear. However, there
is evidence that it may involve in alteration of membrane lipid and reduction in
cholinesterase activity in the brain. Guan et al.25 demonstrated that the contents of
phospholipids and ubiquinone are altered in the brain of rats affected by chronic
fluorosis, and therefore changes in membrane lipids could be involved in the
pathogenesis of this disorder. F is also known to have adverse effects on
cholinesterase activity involved in the hydrolysis of esters of choline.26 This toxic
effect may lead to altered utilization of acetylcholine, thus affecting the
transmission of nerve impulses in brain tissue.27-29 Recently, NaF has been found
to alter the levels of dopamine, serotonin, 5-hydroxyindoleacetic acid,
homovanillic acid, norepinephrine, and epinephrine in the hippocampus and
neocortex regions of the rat brain.30 Earlier, Yu et al.31 demonstrated changes in
neurotransmitters and their receptors in human fetal brain from an endemic
fluorosis area.
It is also well established that F can pass through the placenta to the fetus, and
with subsequent continuous exposure to F during childhood, it may have adverse
8.91
69.66
0
49.5
33.66
2.97 1.98
1.98
0.99
3.37
8.99
15.73
2.25
0
0
10
20
30
40
50
60
70
80
? 69 70-79 80-89 90-109 110-119 120-129 ? 130
Range of intelligence quotient
Percent
distribution
###
##"
#
##!
Range of intelligence quotient
Percent distribution
"7;>G6V IQ score distribution of children in the high and lower F areas.
High fluoride area
Low fluoride area
Research report
Fluoride 40(3)178–183
July-September 2007
Effect of high F water on children’s intelligence in India
Trivedi, Verma, Chinoy, Patel, Sathawara 182182
effects on the developing brain, thereby causing decreased IQ in children.32-34 The
greater reduction in IQ of children exposed to high F in our study compared to
previous studies might reflect the magnitude of the difference in F concentration in
the drinking water of the two areas, the modified version of the IQ test, and/or
environmental, genetic, and cultural variations. The difference in F concentration
in the drinking water between the two areas is 3.54 mg/L, which is higher in
comparison to the studies done by Lu et al.20 (2.78 mg/L), Xiang et al.18 (2.11 mg/
L), and Seraj et al.35 (2.1 mg/L).
Thyroid hormones play an important role in development of brain and thus
might also affect IQ level. As noted in the Introduction, important aspects of F/
iodine interactions on thyroid function are now being explored,12-14 and Susheela
et al.22 have found that elevated F intake may cause iodine deficiency in fluorotic
individuals, even when they reside in non-iodine deficient areas.
Clearly, for the benefit of future generations, urgent attention needs to be
directed to improving our understanding of and correcting adverse effects of F on
intelligence.
%%%/#`0&.*!-)!2!0$1
We take this opportunity to express our gratitude to Ms Yasheshvini A Trivedi
and Twinkle N Tiwari for their kind assistance in conducting the IQ test. We also
thank the technical staff of the National Institute of Occupational Health, Mr
Pradeep Arya and Mr Idrish Shaikh, for their kind help with the analysis of urine
and water samples.
,!"!,!0#!1
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Effect of high F water on children’s intelligence in India
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Copyright © 2007 International Society for Fluoride Research.
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... According to research, fluoride can cause negative biochemical and functional alterations in the developing human brain [4]. High levels of fluoride in drinking water may have a negative impact on intelligence, which could be a major health issue. ...
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... Raymond Cattell asserts that intelligence increases until the age of 15 and thereafter remains constant. Additionally, examining these age groups made it easier to compare the results of this study with those of numerous other studies in which kids in a comparable age group were examined [4,5,9]. Children's IQs were measured using Raven's Coloured Progressive Matrices test, which is a "culturally fair" test suited for comparing children in terms of their immediate capacities for observation and clear reasoning. ...
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