Abstract

Aim: The aim of the present study was to evaluate the relationship of drinking water fluoride levels with children’s intelligence quotient (IQ).

Materials and methods: Water was collected from initially identified endemic fluoride regions according to the geological research of Government of India. Fluoride concentration of the water was assessed by utilizing fluoride ion selective electrode, Orion 9609BN, and categorized on the basis of fluoride concentration into low, medium, and high-fluoride regions, i.e., Virajpet (low fluoride level < 1.2 ppm), Banavara (Medium fluoride level 1.2-2 ppm), and Mastihalli (High fluoride levels > 3 ppm). Government school from all three villages were selected randomly and IQ levels were assessed by using Raven’s Standard Progressive Matrices. This test was conducted on each child in the study sample.

Results: A significant inverse relationship was found between the fluoride concentration in drinking water and IQ (r value = -0.204; P < 0.000). It was observed that IQ level was negatively correlated with fluoride concentration in drinking water.

Conclusion: It is concluded that IQ level was negatively correlated with fluoride level in drinking water. 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.

EXCERPTS:

DISCUSSION

The study was conducted in government school children aged 10–12 years. The study involved almost equal numbers of male and female children. The present study showed that there was no significant association between the mean IQ level and gender. These results are similar to the studies done by Poureslami et al.[6] and Seraj et al.[7] In a study conducted by Xian et al.,[8] only one village out of two villages considered had a significant relationship between IQ and gender. In a psychological book written by Beirne-Smith et al., gender is mentioned as a non-related factor to IQ.

The present study showed low mean IQ in high fluoride concentration areas (31.59 ± 16.81) compared to low fluoride concentration areas (41.03 ± 16.36). The study results are similar to the study reported by Eswar et al., where mean IQ in high fluoride areas was 86.3 ± 12.8 and in low fluoride areas was 88.8 ± 15.3,[9] and in a study conducted by Karimzade et al., where the IQ of the 19 students in the high-fluoride areas was lower than 20 students in the low-Flouride areas.[10] According to Eswar et al., lack of IQ in children exposed to high levels of fluoride is mainly due to functional and biochemical harm to the nervous system during the prenatal and development periods of infancy and childhood because fluoride can cross the blood brain barrier; however, it is also due to factors involving variation in biological susceptibility, environmental conditions, and measurement errors.[11] During pregnancy, fluoride plays a major role in in determining IQ development such as freedom from disease, parental IQ, nutrition, prenatal care, breast feeding, physical trauma, and good schooling.[12] In addition, the present study results are consistent with the study of Sebastian and Sunitha[13] who demonstrated a higher percentage of children with above the normal IQ range in the normal and low-fluoride group compared to high-fluoride group. This was in line with the findings of Trivedi et al.,[14] who reported that an elevated fluoride level would affect higher levels of intelligence more vigorously than normal and low intelligence levels. There was a statistically significant difference in IQ levels of children belonging to high, medium, and low fluoride areas, which was in accordance with studies reported by Khan et al.[15] and Mondal et al.[16] The present study is in contrast with Broadbent et al.[17] study results, where there was no apparent difference in IQ because of fluoride exposure. In the present study, certain factors were not taken into consideration such as exposure to school environment and freedom from physical trauma; the possible effects of the above mentioned confounding factors including the parental education and difference in socioeconomic status between the villages. Therefore, it is not possible to explain the IQ of children based on the effects of exposure to high or low-fluoride water alone.

In the present study, significant negative correlation was found between IQ and fluoride concentration level in drinking water (r value = -0.204, P < 0.0001), in which the results were contrary to the research conducted by Kundu et al.,[18] which showed a positive correlation of fluoride in drinking water with IQ (r = 0.417). Our study results were in accordance with those of Das et al.,[19] where 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). Further investigations are required with larger sample size considering all the confounding factors to clarify the nature of the relationship between intelligence and fluoride are clearly desirable.

CONCLUSION

Fluoride has been advised since a long time as the ideal preventive, therapeutic agent for dental caries. However, like a coin that has two sides, fluoride has both favorable and harmful effect. In the present study, it was observed that IQ level was negatively correlated with fluoride concentration level in drinking water and it is highly significant (P < 0.0001). Therefore, it is necessary to devise solutions for preventing the harmful effects of excessive intake of fluoride ion in the body. Because fluoride has the capability to be toxic to many organ systems, further toxicity studies must be conducted to evaluate this further. It is essential to evaluate the current situation and control the drinking water fluoride level if the fluoride concentration in a community’s water supply is significantly above the permissible level of 1.5 mg/L.

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ABSTRACT ONLINE AT
https://journals.lww.com/jpcd/fulltext/2016/06003/effect_of_fluoridated_water_on_intelligence_in.11.aspx

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